**TableA8.**Correlationmatrixofvariablesdescribingmixedproductionfarms.

Source:Owncalculation basedonFADNdata

 [28].

#### **References**


## *Article* **Economic and Energy Efficiency of Farms in Poland**

**Marcin Wysoki ´nski 1, Bogdan Klepacki 1, Piotr Gradziuk 2, Magdalena Golonko 1, Piotr Gołasa 1, Wioletta Bie ´nkowska-Gołasa 1, Barbara Gradziuk 3, Paulina Tr ˛ebska 1, Aleksandra Luba ´nska 1, Danuta Guzal-Dec 4, Arkadiusz Weremczuk <sup>1</sup> and Arkadiusz Gromada 1,\***

	- <sup>2</sup> Poland Economic Modelling Department, Institute of Rural and Agricultural Development, Polish Academy of Sciences, 00-330 Warsaw, Poland; pgradziuk@irwirpan.waw.pl
	- <sup>3</sup> Poland Department of Management and Marketing, Faculty of Agrobioengineering, University of Life Sciences in Lublin, 22-033 Lublin, Poland; barbara.gradziuk@up.lublin.pl
	- <sup>4</sup> Institute of Economics, Pope John Paul II State School of Higher Education in Biała Podlaska, 21-500 Biała Podlaska, Poland; danuta\_guzal-dec@wp.pl
	- **\*** Correspondence: arkadiusz\_gromada@sggw.edu.pl

**Abstract:** Climate change and negative environmental effects are results of a simplified understanding of management processes, i.e., assuming economic effects as the basis for development, without taking into account external costs. Economically efficient facilities are not always environmentally efficient. Due to the existing conflict of economic and environmental goals, it seems necessary to look for measures that would include both economic and environmental elements in their structure. The above doubts were the main reasons for undertaking this research. One of the important sectors of the economy accepted for research, where energy is an essential factor of production, is agriculture. Agricultural production is very diversified both in terms of inputs and final products. Depending on the production direction, the processes of conversion of energy accumulated in inputs into energy accumulated in commodity products have different natures and relationships. Taking into account the importance of agriculture in the national economy and the current environmental needs of the world, the types of farms generating energy surplus and those in which the surplus is the least cost-consuming were indicated. The research used the economic and energy efficiency index, which makes it possible to jointly assess technical and economic efficiency. Assuming the need to produce food with low energy consumption and a positive energy balance, it is reasonable to develop a support system for those farms showing the highest economic and energy efficiency indicators.

**Keywords:** agriculture; energy consumption; efficiency; farms; FADN

#### **1. Introduction**

The current standard of living of mankind is possible thanks to the exploitation of natural capital on an unprecedented scale, which causes increasing interference in the state of the planet and uncertainty about its future [1]. Natural resource mismanagement leads to climate change and limitations in the biological productivity of the land [2–5]. In the history of mankind, there have been many cases of degradation of regional ecosystems as a result of human activity. One of them was "ecological suicide", the so-called Fertile Crescent that 12,000 years ago was the cradle of cities, empires, and great civilizations in the Middle East. The Fertile Crescent is a belt of more fertile lands, shaped like a great crescent, stretching from Egypt, through Palestine and Syria, to Mesopotamia. It extended from Memphis in the Nile Valley to Ur in southern Mesopotamia, including Syria and Canaan, the steppe between the mountain range of Asia Minor and the Syrian Desert. It is

**Citation:** Wysoki ´nski, M.; Klepacki, B.; Gradziuk, P.; Golonko, M.; Gołasa, P.; Bie ´nkowska-Gołasa, W.; Gradziuk, B.; Tr˛ebska, P.; Luba ´nska, A.; Guzal-Dec, D.; et al. Economic and Energy Efficiency of Farms in Poland. *Energies* **2021**, *14*, 5586. https:// doi.org/10.3390/en14175586

Academic Editors: Dalia Štreimikiene˙ and Talal Yusaf

Received: 16 July 2021 Accepted: 27 August 2021 Published: 6 September 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

the geographic cradle of the great civilizations of the ancient Near East. Thanks to favorable conditions, the first agricultural areas were created here (around 10,000 BC). During the Neolithic revolution, wheat, millet, and barley were grown here. As man domesticated new species of plants and animals, legumes, figs, and grapevines began to be cultivated. Later, the civilizations of Mesopotamia and Ancient Egypt developed [6]. As a result of human activity, this area has become a dry, desert terrain, economically and socially backward. In the 21st century, humans are causing ecosystem destruction on a global scale, i.e., they will not be able to move to areas with favorable living conditions, as did the ancestors from the Fertile Crescent. According to Diamond [7], the societies that committed inadvertent "ecological suicide" were among the most developed and complex of their time. Currently, the most developed economies are experiencing trends based on the economic cult of economic growth and the consumption of goods and services, which are produced based on resources obtained from the environment. The appropriate counterbalance may be sustainable development [8–12], the condition of which is shaping the relations between the economy, society, and the environment in such a way that will not affect the ability of the environment to provide its services in the future. It is also important to treat environmental issues from a supranational and global perspective, treating the earth's ecosystem as a common good [13,14]. A contradiction of such an idea is, for example, the transfer of energy-intensive and "environmentally dirty" production by rich (pseudo-sustainable) countries to other parts of the globe. A significant problem is also the uneven distribution of natural resources, especially minerals, which are the main sources of energy. It is very dangerous to be in a situation where several countries have a good whose consumption can no longer be excluded. International raw material and energy dependencies are becoming an element of pressure and may be the cause of socio-economic crises.

The technological nature of human existence is dependent on external energy sources, which has become the condition of every civilization and the driving force behind every action. According to the Goban-Class [15], "without matter, there is nothing, without energy everything is stationary". This confirms the contemporary dependence of mankind on energy, which determines economic growth, living standards, and can also be a source of international conflicts [16,17]. One of the main problems is the limited energy sources, especially non-renewable ones. Therefore, there is a need for proper management, taking into account the needs of the present and future generations of the Earth's inhabitants [18] (Figure 1).

**Figure 1.** Energy management as an economic problem. Source: own study.

Another problem is the negative impact on the environment of the processes of obtaining energy from non-renewable sources. The main disadvantage is the high greenhouse gas emissions and interference with the ecosystem of conventional energy [19]. Climate change and any negative environmental effects are the results of a simplified understanding of

management processes, i.e., assuming economic effects as the basis for development, without taking into account external costs. Performing an assessment solely using the classical measurement of economic efficiency turned out to be the wrong approach, providing inadequate information from the point of view of sustainable development. Economically efficient facilities are not always environmentally efficient. Due to the existing conflict of economic and environmental goals, it seems necessary to search for measures that would include both economic and environmental elements in their structure. The above doubts were one of the main reasons for researching the presented study. Another premise is the dependence of the world economy and its growth on limited natural resources and the growing energy demand. Moreover, there is a need to improve energy efficiency and reduce greenhouse gas emissions on a micro- and macro-scale [20]. Thus, the improvement of energy efficiency becomes the goal to which all activities aimed at reducing the energy consumption needed by the economy to produce products and services are subordinated.

A significant consumer of energy is modern agriculture, which, especially in developed countries, is fully dependent on external non-renewable energy sources. In the 20th century, when the world population increased 3.7 times and the inhabited area increased by about 40%, the energy input increased from 0.1 to almost 13 EJ. As a result, in 2000, on average, about 90 times more energy was used per hectare of arable land than in 1900. In 1900, gross global plant production (before losses in storage and distribution) was little more than the average human food demand, meaning that a large proportion of humanity had little or no nutrition, and the share of the harvest that could be used for feeding the animals was minimal. Increased energy inputs allowed the basic varieties to reach their full potential, which increased yields [21].

The use of means of production of industrial origin meant the introduction of a new source to agriculture—fossil raw materials, which was initiated by the use of solid fuels. Increasing energy resources increased production effects, in particular in plant production. Today, agriculture draws energy from two sources: biospheric resources and fossil resources, which correspond to two types of power—natural and industrial.

Agriculture using only natural sources of energy was a system with relatively high input processing efficiency. The production effects were not high, but the energy expenditure was also small. As the use of fossil fuel energy increases, the unit of energy expended yields less and less product revenue, which is a direct result of the law of diminishing returns. In addition, the increasing consumption of fossil fuels means an increase in greenhouse gas emissions from agriculture and an increasingly negative impact on the natural environment.

In agricultural activity, energy as a production input may determine the profitability of agricultural production, which in turn may affect the level of investments in farms aimed at improving production systems. It can be assumed that measures leading to the improvement of energy efficiency in agriculture and, consequently, to the reduction of production costs, are necessary both from an economic and environmental point of view by reducing GHG (greenhouse gas) emissions [22–24]. The discussion about energy use in agriculture most often focuses on direct energy consumption [25–29]. It is worth noting, however, that 50% or more of total energy consumption is due to the production of nitrogen fertilizers or other activities that indirectly affect the number of energy inputs [30,31]. Different agricultural production systems under different environmental conditions show different energy consumption and energy-saving potential. Therefore, the energy needs of agriculture depend on the nature of individual production processes, and agricultural production is very diverse both in terms of inputs and final products. Depending on the production direction, the processes of conversion of energy accumulated in inputs into energy accumulated in commodity products have different natures and relationships, hence the main objective of this research was to identify economic and energy efficiency in agriculture depending on the type and scale of production.

The research is an original contribution of the authors in the area of analyses of economic and energy efficiency. The proposed index is a measure that combines both economic

data and technical data on energy consumption. The innovative approach consists in implementing the EROI (energy return on invested) method in agricultural research and treating the farm as a system that converts energy invested into commodity energy useful for humans in the form of food products. Recognizing that the most important task of agriculture is to feed humanity, a methodology was proposed to evaluate farms in terms of their efficiency and conversion of energy invested into commodity energy. Bearing in mind the negative impact of agriculture on the environment, inter alia through the consumption of non-renewable energy sources, the research results provide information on which farms generate energy surpluses and which of them do it at the lowest cost. The results of the research fill the gap in this respect because in the area of agriculture, the analyses conducted concern either only economic efficiency or only energy efficiency.

#### **2. Materials and Methods**

The research used the economic and energy efficiency index (*EEEI*, used for research on farms). The main theoretical assumption of the indicator is to treat a farm as a system that uses energy accumulated in inputs necessary for production, and on the other hand, a system that supplies energy contained in products sold, both of plant and animal origin (Figure 2). Based on Goł ˛ebiewska [32], a systemic approach was applied. The inputs "reaching" the farm are transformed in the production process into effects that "leave" the system. What "enters" the system (for example as raw material) is transformed within the system (farm) and leaves the system at the output (as products). The energy entering the system is energy that is purposefully invested by humans (the calculation does not include the energy provided by the sun and used by plants in photosynthesis), while the energy leaving the system is commodity energy (energy contained in animals and vegetable products) useful to consumers. This approach allows the assessment of the effectiveness, including economic, of conversion of invested energy into commodity energy.

**Figure 2.** Generalized model of an agricultural farm as an energy system. Source: own study.

One of the goals of the work was, inter alia, diagnosing in which types of farming and on what scale of production the ratio of commodity energy to invested energy is the highest. Farms produce very diverse products that provide human living energy. While only a few dozen years ago the basis for the evaluation of a given production was the economic account, nowadays, it is necessary to include the environmental account. Humanity must very precisely produce food, paying attention to the lowest possible

consumption of resources, including energy. Man needs a certain amount of protein and energy to live and work. The challenge is therefore to develop an optimal structure of food products produced with minimal energy inputs. The conducted research is the first step, where the purpose is to obtain information on which farms will provide more energy for the consumer than they use in the production process. The next step was to identify farms where the energy surplus is the least expensive. For this purpose, the following economic and energy efficiency index (*EEEI*) was constructed:

$$EEEI = \frac{\sum\_{t=1}^{j=n} \left( G\_p \* Q\_j \right) - \sum\_{t=1}^{i=n} \left( G\_r \* Q\_i \right)}{TPC} = \frac{CE - IE}{TPC} = \frac{SE}{TPC} \tag{1}$$

where:

*EEEI*—economic and energy efficiency index, *Gp*—the weight or quantity of the individual products sold, *Qj*—the amount of energy contained in individual products sold (Table 1), *Gr*—the weight or number of individual inputs, *Qi*—the amount of energy contained in individual inputs (Table 2), *TPC*—total production costs (EUR).

$$SE = CE - IE\tag{2}$$

where:

*SE*—surplus energy (MJ),

*CE*—commodity energy (energy included in sold production) (MJ),

*IE*—invested energy (energy accumulated in direct and indirect inputs used in the production process) (MJ).

$$IE = E\_{cc} + E\_{II} + E\_{af} + E\_{pf} + E\_{pa} \tag{3}$$

where:

*Eec*—energy from energy carriers (fuels, electricity) (MJ),

*Ell*—energy equivalent to live labor (MJ), *Eaf*—energy contained in artificial fertilizers (MJ),

*Epf*—energy contained in purchased feed (MJ),

*Epa*—energy contained in animals from purchase (MJ).

**Table 1.** Energy value of products used to calculate the commodity energy.



**Table 1.** *Cont.*

Reproduced from [33].




**Table 2.** *Cont.*

Reproduced from [33–35].

For empirical research in the field of economic and energy efficiency of farms, data from the Polish FADN (Farm Accountancy Data Network) for 2016, from the entire territory of Poland, were used. The FADN operating in Poland is part of the European system, operating since 1965, based on the Regulation of the Council of 15 June 1965 setting up a network for the collection of accountancy data on the incomes and business operation of agricultural holdings in the European Economic Community [36]. Data in FADN are collected in the management accounting convention. The FADN database is economic and organizational. It is now the most complete source of information on the situation of agricultural holdings. The identical principles of operation of the FADN system throughout the EU make the results comparable for all EU countries. The obtained data are used both for decision-making by EU bodies, monitoring the effects of these activities, and scientists dealing with the economics and organization of agriculture. Participation in the FADN system is voluntary. Farmers participating in the research write down every economic event that took place on their farm, in a special book, then agricultural advisors transfer them to the system [24]. When selecting the research objects, the purposeful selection method was used—the results were adopted according to the set of classification coefficients "SO 2013". To eliminate the influence of the production structure and economic power on the results of the analyses, all calculations were performed using the division of farms into production types and economic size classes. The production type is defined as the share of standard outputs (SO) from particular production lines in the total value of standard production of a given farm. Two threshold values apply to the type of farming formula. Farms in which the share of one direction of plant or livestock production exceeds 2/3 of SO are called specialist farms. Farms where the share of any of the directions does not exceed 1/3 of the SO are defined as "mixed", i.e., combining animal and plant production

(multidirectional) [37]. The economic size of farms is determined by the sum of standard outputs from all agricultural activities occurring on a given farm. Standard output (SO) is the five-year average value obtained from one hectare of a given type of crop production or, in the case of livestock production, from one head, in the production conditions average for a given region [38]. For analytical purposes, farms classified into 5 types of farming were selected following the FADN methodology:


The division of the researched farms into 3 economic size classes in each type was adopted, considering the economic size of the farm as a criterion for grouping:


The surveyed population is 6261 farms. The most numerous group were farms specializing in dairy cattle breeding (2742 farms) and farms specializing in cereal cultivation (2036 farms). Taking into account the economic size classes, the share of farms in individual classes was very similar: 2143 in economic size class I, 2077 in economic size class II, and 2041 in economic size class III. Due to the type of farming and the economic size class of classified farms, the largest group in the study were medium-sized farms specializing in dairy cattle production (1165 farms).

The paper presents only selected production and economic indicators, which allowed for the characteristics of the examined objects in terms of assets involved, costs incurred, or effects of the activity. The selection of the presented data also resulted from their impact on economic and energy efficiency.

All the researched farms conducted their activities using land resources, which the greater they were, the higher the economic size (Table 3). The greatest amount of arable land was found on cereal farms—approximately 62 ha on average. However, the ownership structure of the land used is interesting, including the ratio of leased land to own use.

Among the analyzed types of farming, the largest amount of land was leased by farms specializing in cereal crops, which constituted approximately 32% of the total area of agricultural land in these farms. Farms with this type of production, working out by far the smallest direct surplus per hectare, are forced to increase their area more intensively to achieve acceptable income than farms with other types of production. Farms specializing in the cultivation of fruit trees and shrubs used the lease to the least extent, which is largely due to the specificity of production based on long-term plantings and significant related investments. The duration of the lease is usually limited to 5 years, which is a disadvantage in this case. It was found that with the increase in the scale of production, the share of leased agricultural land in each type of farm increases. This process was most dynamic in the pigs' type.

It was assumed that the number of tractors may also affect the efficiency considered in the study—fuel consumption is one of the main energy inputs in agriculture. It was found that farms specializing in the cultivation of fruit trees and shrubs were characterized by significantly higher than average equipment with tractors—on average almost 15 pieces per 100 ha of UAA (Utilized Agricultural Area). The reasons can be found in the large number of agrotechnical and agro logistic works carried out at the same time, which determines the need to have many low-power tractors. The use of large and efficient machines is also problematic, as in the case of cereal production, where on average 2.4 tractors are used per 100 ha of agricultural land. A negative correlation was observed between the production scale and the number of tractors per 100 ha of UAA.


**Table 3.** Characteristics of the researched farms.

Source: own study.

One component of the invested energy is labor input. In the studied objects, they were the highest in fruit-growing farms—on average 19.17 AWU (Annual Work Unit) per 100 ha of UAA, and the smallest in farms specializing in the cultivation of cereals, oilseeds, and protein crops for seeds—on average 2.49 AWU per 100 ha of UAA. The level of labor inputs decreases with increasing economic size. Clear differences in the labor intensity of extreme types of farming are a consequence of the specificity of production and the possibility of using efficient machines and work automation, which should translate into savings in energy inputs.

Fixed assets include agricultural land, farm buildings, forest plantings, and machinery and equipment, as well as livestock animals (Table 4). For the calculation of the invested energy, energy accumulated in machines and devices as well as in buildings and structures was taken into account, as an indirect input. Taking these components into account gives grounds to believe that the conducted analyses have the features of a drawn calculus. Therefore, it was considered justified to present the significance of selected components of fixed assets and indicators of technical equipment for land and work in the researched farms.


**Table 4.** Structure of assets and technical infrastructure of land and work.

Source: own study.

The share of fixed assets in total assets was at a similar level in all types. The highest level of the indicator was recorded in small horticultural farms (91.01%), and the lowest in large farms specializing in slaughter cattle (83.05%).

When analyzing the structure of fixed assets, clear differences in individual types were observed. In the case of buildings, their share in fixed assets ranged from 7.82% in the largest cereal farms to almost 30% in farms specialized in rearing pigs from economic size class I. It should be added that pig farms had the highest index in all economic size classes. Therefore, these farms have the greatest negative impact of buildings and structures on the energy invested. This indicator decreases along with an increase in the economic size of farms. For buildings, it was assumed that the value of energy, which is the expenditure in a given year, constitutes 2.5% of the total energy accumulated in this fixed asset—following the principles of calculating depreciation for buildings and structures.

The researched farms were characterized by a very high share of machines and devices in the structure of fixed assets (18% on average). The differences between the individual types of farming were slight. The farms specializing in rearing cattle for slaughter were characterized by a lower index than the average. It was also found that the share of machines and devices in fixed assets increases with the increase in the scale of production. In the case of machines and devices, it was assumed that the value of energy, which is an input in a given year, constitutes 14% of the total energy accumulated in this fixed asset—following the principles of calculating depreciation for machines and devices.

A measure closely related to the value of buildings and machinery and equipment is the technical equipment of the land, which achieved the lowest value in large farms specializing in cereal cultivation (EUR 1699.99 per ha of UAA), while the highest value in small horticultural farms (EUR 6928.13 per ha of UAA), which is determined by the production technology appropriate for horticultural farms, where specialized buildings and structures (cold stores, etc.), as well as machines and devices, are required.

The study also counted the technical equipment of work, which in the studied group of farms is very diverse and ranges from EUR 28,609.24 per AWU in the smallest dairy farms, up to EUR 115,269.42 per AWU on cereal farms from economic size class III. Along with the increase in the economic size of farms, there is an increase in the technical equipment of work. The factor strongly affecting the level of this indicator is the number of people working on the farm, which is several times higher on dairy farms than on cereal farms.

#### **3. Results**

During the analyses, attention was also paid to economic effects (Table 5). One of the measures used for such calculations is economic labor productivity, which increases with the increase in the economic size of the researched farms, except farms specializing in the cultivation of fruit trees and shrubs. Average economic labor productivity for fruit farms is several times lower than in other types of production. The differences deepen with the increase in the scale of production. In every economy size class, cereal farms are the leader.


**Table 5.** Economic results of researched farms.


**Table 5.** *Cont.*

Source: own study.

The land profitability index is the ratio of income from an agricultural holding to the UAA. It allows for the assessment of land use efficiency as one of the production factors. The highest profitability of land was characterized by large farms specializing in pig farming (EUR 1009.66 per ha of UAA) and small farms specializing in the cultivation of fruit trees and shrubs (EUR 930.67 per ha of UAA). The lowest values of this indicator were recorded for both small, medium-sized, and large farms specializing in the cultivation of cereals (approximately EUR 387.17 per ha of UAA), which use employees more effectively than the cultivated land. It is worth adding that cereal farms require relatively the largest amount of energy to be invested to earn EUR 1.00 of income—on average 87.68, which is a result 2.5 times worse than in farms of the slaughter cattle type.

The factor having a significant impact on the cost-intensity of the researched farms was energy costs (engine fuels, electricity, heating fuels). However, their impact on direct costs was varied (Table 6). By far the highest share of energy costs in direct costs was recorded in fruit-tree and shrub-type farms, which results from the specificity of production in these facilities. The dependence of this variable on the economic value was identified—with the increase in the scale of production, the share of energy costs in direct costs decreases. This relationship was most clearly visible in pig farms. Fruit farms were also characterized by the highest energy costs per hectare of UAA—on average EUR 210.89. The results of research on the structure of energy costs, which depended on the type of agricultural production, are interesting. For example, the cost of electricity was much more important for fruit and pig farms (on average over 30% share in energy costs) than for cereals (6.75%). Apart from the farm types of cereals and slaughter cattle, no clear correlation was found between the share and the economic size. In the case of the costs of propellants, their highest share in the energy costs is held by farms in the types of cereals and slaughter cattle—about 90%. The importance of individual energy sources depends on the needs of individual types of farming, resulting from the number of works and activities specific to a given production.

**Table 6.** Characteristics of energy costs in the researched farms.



**Table 6.** *Cont.*

Source: own study.

Invested energy is one of the key elements of the proposed economic and energy efficiency index. Therefore, it is important to recognize the impact of individual energy inputs on their amount. The structure of the energy invested is shown in Table 7. Mineral fertilizers, direct energy carriers (engine fuels, electricity, heating fuels), as well as machines and devices, had the greatest share. The energy inputs accumulated in buildings (this is a consequence of the adopted methodology of calculation—2.5% of the total expenditure, which corresponds to the methodology of depreciation) and the energy contained in the equivalent of live labor had a marginal impact. In the case of fertilizers, their dominant share was in the energy invested in cereal farms—75% on average. In this area, it is possible to seek efficiency improvement by reducing the most energy-consuming inputs. Direct energy carriers had the highest share in fruit farms, which results from the course and specificity of production in these facilities. Additionally, the share of machines and devices in shaping the invested energy was the highest in these farms.


**Table 7.** Invested energy structure.


**Table 7.** *Cont.*

Source: own study.

Concerning fertilizers, buildings, and live labor, it can be argued that along with the increase in the scale of production, the share of energy inputs in the invested energy decreases.

One of the objectives of the work was to calculate the EROI, i.e., the ratio of commodity energy to invested energy. Invested energy is energy accumulated in inputs used in the production process, while commodity energy is energy accumulated in sold products. The index should therefore be above 1, otherwise, it means that more energy has been invested than obtained in the production process. From an economic and environmental point of view, any activity should generate energy surpluses. In the researched farms, only the production of cereals and pigs generated such a surplus, regardless of the production scale (Table 8). Additionally, the smallest farms specialized in milk production recorded the indicator above 1. The greatest losses of energy were recorded in farms specialized in the production of slaughter cattle and fruit from economic size class III. It was found that with the increase in the production scale, the EROI index decreased. This is the result of a disproportionate increase in commodity energy in relation to the increasing energy inputs accumulated, among others in mineral fertilizers and larger, more advanced machines and devices used in farms with a larger production scale.

When analyzing the economic and energy efficiency separately and comparing their course, different relations between them depending on the type and scale of production were observed (Figure 3). It was found that farms with the highest energy efficiency (cereals) are characterized by the lowest economic efficiency, while the opposite was true for farms specialized in fruit production. It is worth adding that farms of the slaughter cattle type achieved the lowest values for both types of efficiency. The reaction of the examined efficiencies to changes in the production scale was also interesting. There was no common trend in this respect for the researched types of agricultural production. In pigs and dairy cattle farms, energy efficiency decreased and economic efficiency increased as the scale increased. The situation was quite different in fruit farms, where the growing production volume had negative effects on both economic and energy efficiency. In the case of cereals and slaughter cattle, the scale of production had a slightly positive impact on the economic effects per hectare of UAA, while in the case of energy efficiency, the direction of the trend cannot be clearly stated.

**Table 8.** Commodity energy to invested energy relations.


**Figure 3.** Economic and energy efficiency in the researched farms. Source: own study.

The last stage of the research was to calculate the economic and energy efficiency according to the proposed methodology (Figure 4). The highest ratio was achieved by farms specialized in cereal production—on average they generated 26.60 MJ of energy surplus per EUR 1.00 of costs. The result above zero was also achieved by pig producers and the smallest dairy farms.

**Figure 4.** *EEEI*-economic and energy efficiency index (MJ/EUR). Source: own study.

In the group of effective farms (index above zero), the most effective farms were those with the smallest production scale. Therefore, it can be concluded that in the case of economic and energy efficiency, there are decreasing scale effects.

#### **4. Discussion**

Energy analysis, as an independent research approach, was first used in the early 1970s [39]. An impulse for research towards energy analyses was the work of Georgescu-Roegen "The entropy law and the economic process" [40] from 1971. Such analyses require combining biological and technical knowledge with economic knowledge [41–43]. It is not very easy, and therefore, no appropriate, uniform methodological foundations have yet been developed in energy analyses [44–46]. Previous studies usually focused on economic or energy efficiency, treating them separately. This approach was also most often used in agriculture. Energy efficiency indicators are used to evaluate various agricultural systems as well as production methods (ecological, conventional) [47–51]. According to Risoud [52] and the methodology developed in her work, the energy efficiency of a farm is defined as the following ratio: gross energy of useful products/non-renewable energies used to produce them. Research in the field of energy consumption and efficiency of its use was conducted in particular concerning selected crops or breeding. The energy and economic analysis of wheat cultivation in Bangladesh were carried out by Rahman and Hasan [53], and the rice production on farms in Iran by Pishgar-Komleh et al. [54]. In their opinion, mainly, large farms (more than 1 ha) had better management and were more successful in energy use and economic performance. Heidari et al. in their research determined the efficiency of energy use (EUE) for the production of broilers [55]. Energy consumption and energy efficiency for a representative crop (Flemish Farm Accountancy Data Network, FADN) of specialized dairy, arable, and pig farms in Flanders were determined by Meul et al. [56]. The most energy-efficient dairy and pig farms were intensive farms, which combined a high production with low energy use, and which possessed a gross value added per production unit comparable to, or even higher than the average.

Energy efficiency, yield efficiency, and labor requirements in the production of maize, wheat, potatoes, and apples were determined for organic (without synthetic fertilizers and pesticides) and conventional agricultural technologies in the studies of Pimentel et al. [57]. For all four crops, the labor input per unit of yield was higher for organic systems compared to conventional production. Similar studies for the comparison of cultivation systems (conventional, organic, and integrated) were carried out by the Italian research team of Falcone et al. [58]. The energy efficiency and economic effects of the main cultivation methods (conventional, organic, and integrated) of clementine's crops in Calabria (South Italy) were assessed by a combined use of the Life Cycle Energy Assessment (LCEA) approach and economic analysis. The economic efficiency of energy from clementine production was higher compared to the other two farming systems.

Keummel et al. [59] proposed, for example, a system of agricultural production combining food and energy production, which could be a step towards the development of sustainable agriculture. The purpose of introducing such a system would be to reduce the positive balance of carbon dioxide emissions by agriculture, which contributes to climate change. This goal would be achieved by replacing the use of energy from fossil fuels with energy from biofuels produced in mandatory separate areas within farms. In this way, the emission of carbon dioxide from fossil fuels would be significantly reduced and, additionally, the absorption of carbon dioxide from the atmosphere by crops could increase. These studies show that such a system would be economically acceptable both from the point of view of the farmer and the society. Introducing biofuel production on a local scale would have benefits not only in terms of energy and climate, but also reducing carbon dioxide emissions was estimated by the authors at the equivalent of EUR 300/ha of external benefits.

It is worth paying attention to the research of Alluvione and co-authors [60]. These researchers analyzed energy consumption and efficiency in three farming systems: lowcost, integrated, EU-compliant, and traditional-conventional. It was found that in the first two systems, the efficiency of energy use increases by 32.7% and 31.4% respectively, while maintaining similar results in terms of net energy. In the area of research on efficiency, the study by Uzal [61] deserves attention, where the energy efficiency of milk production was compared on two farms. In the first, dairy cattle were reared in a free-stall housing system, in the second—in a loose housing system. It was found that in both cases, the highest percentage of energy inputs came from feed and the electricity consumed. Total energy consumption per hectare was lower on loose housing system farms. In the research by Gronroos et al. [24], the energy consumption of traditional and organic milk and rye bread production in Finland was examined. Basic energy consumption in traditional milk production was 6.4 GJ per 1000 L of milk and 4.4 GJ in organic production. In the case of the production of rye bread, it was 15.3 and 13.3 GJ respectively, per 1000 kg of rye bread. Renewable energy use ranged from 7% to 16%, with a slightly higher percentage for organic farming.

An interesting approach to energy productivity in agriculture was presented by Uhlin [62], questioning the statements widely described in the earlier literature that to reverse the downward trend in energy productivity in Swedish agriculture, energy inputs from fossil fuels should be reduced. The author claims that the emphasis should be placed not on the reduction of the use of fossil fuels, but on the development of the use of energy from renewable sources, e.g., solar energy, as this approach offers many more benefits than just reducing energy inputs. In research and policymaking, technical development and modern technologies used in agriculture should not be overlooked

One of the methods of assessing effectiveness is Data Envelopment Analysis (DEA). Using this method, Ghali et al. [63] assessed the efficiency of the use of energy resources in French farms. Results show that disentangling energy resources from the rest of intermediate consumption highlights energy use excess, which is masked when considering intermediate consumption as a whole. Using DEA, Mohammadi et al. [64] assessed the energy efficiency of farmers, to find efficient and inefficient ones and to identify the wasteful

uses of energy in kiwifruit production. Chemical fertilizers and chemical energy were the main inefficient consuming inputs.

An important research problem is also the relation between the energy obtained and the energy put into the production process. Many scientists in recent years have undertaken such research, among them Kuesters and Lammel [65], who in 1989–1997 analyzed the aforementioned relationship for winter wheat and sugar beet. It was found that the ratio of energy obtained to energy input was highest in the case of low-intensity crops, which means that extensive cultivation methods are preferred. However, with these production methods, low yields are obtained, and hence also low energy efficiency, therefore the authors additionally extended the analysis to include the net energy balance. The results were similar.

A similar aim of the research was adopted by Moitzi and his team [26], who verified energy consumption and energy efficiency in selected farms in Slovakia, Romania, Serbia, and Austria. It was found, inter alia, that the intensity of the use of production factors, i.e., fuel, seeds, fertilizers, and pesticides, affects the energy efficiency of plant production. The main analyzed index: energy generated for energy inputs, in the case of winter wheat cultivation was 5.6, with the range from 4.8 to 7.1.

This article proposed a combination of energy efficiency, economic efficiency, and EROI index, and the development of the *EEEI* economic and energy efficiency index (used for research on farms). The main theoretical assumption for the development of the indicator is to treat a farm as a system that uses energy accumulated in inputs necessary for production and as a system supplying energy contained in sold products of both plant and animal origin. Based on Goł ˛ebiewska [32], a systemic approach was applied. The inputs "reaching" the farm are transformed in the production process into effects that "leave" the system. What "enters" the system (for example as raw material) is transformed within the system (farm) and leaves the system at the output (as products). The energy entering the system is energy that is purposefully invested by humans (the calculation does not include the energy provided by the sun and used by plants in photosynthesis), while the energy leaving the system is commodity energy (energy contained in animals and vegetable products) useful to consumers. This approach allows the assessment of the effectiveness, including economic, of conversion of invested energy into commodity energy.

Recognizing that it is necessary to introduce a coherent environmental and energy policy in agriculture, the Common Agricultural Policy should be shaped differently, extending it with measures promoting the economical use of energy sources. Combining self-exclusive goals, i.e., economic and energy efficiency, requires regulation and support. Food production should use energy efficiently and carefully manage natural resources, and this requires a different policy than the current CAP of the EU. In the context of the current needs in the field of environmental protection and eco-efficiency, the obtained research results may be the basis for considering changes in the agricultural policy and its evolution towards supporting farms with the highest economic and energy efficiency. Using the proposed measure, it is possible to search for the best farms, and also within individual types and through the system of payments for these producers, encourage farmers to apply the most beneficial and energy-saving practices and activities. Farms that will be effective in terms of energy management will also emit relatively less GHG, which will have an impact on lower costs related to the planned fees for the GHG emissions.

To further develop research in the field of economic and energy efficiency, using the developed methodology, comparative analyses should be conducted between individual EU countries and a recommendation should be developed concerning in which regions of Europe particular production directions should be developed due to energy efficiency. Moreover, to deepen the analysis and identify the reasons for the differences in the indicator, a questionnaire survey among farmers is needed.

#### **5. Conclusions**


**Author Contributions:** Conceptualization, M.W. and B.K.; methodology, M.W. and P.G. (Piotr Gradziuk); software, P.T. and W.B.-G.; validation, M.W., B.K. and P.G. (Piotr Gradziuk); formal analysis, P.G. (Piotr Gradziuk) and B.K.; investigation, D.G.-D., A.L. and W.B.-G.; resources, A.L., D.G.-D. and B.G.; data curation, P.T., B.G. and A.G.; writing—original draft preparation, M.W. and P.G. (Piotr Gołasa); writing—review and editing, B.K. and P.G. (Piotr Gradziuk); visualization, A.W., A.G. and M.G.; supervision, M.W. and P.G. (Piotr Gołasa); project administration, M.W. and A.G.; funding acquisition, A.W. and M.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


**Paweł Siemi ´nski 1,\*, Jakub Hady ´nski 1, Jarosław Lira <sup>1</sup> and Anna Rosa <sup>2</sup>**


**Abstract:** Access to energy, including electricity, determines countries' socio-economic development. The growing demand for electricity translates into environmental problems. Energy is therefore a crucial element of the European Union's sustainable development strategy. This article aims to present the changes taking place in the electricity market in Poland considering the goals of the energy policy until 2040. This is the basis for the determination of the scale of processes taking place in the Polish energy sector from two perspectives, i.e., the production of electricity considering its level and energy carriers used, and the consumption of electricity in households depending on their location (rural vs. urban areas). The research was conducted at the regional level (NUTS 2 until 2017) in Poland. Secondary data from the Central Statistical Office (GUS) contained in the Local Data Bank were used, along with information from the European Commission and Eurostat websites. Results of the study made it possible to identify areas in which a greater environmental load is observed due to increasing electricity consumption. The coefficient of localization and concentration (by Florence) and the rate of change were applied. These results indicate that, in Poland, it is now the rural areas that have a greater negative environmental impact than urban areas, resulting from differences in unit energy consumption. Compared to the other provinces, rural areas of Podlaskie province had the highest rate of growth in energy consumption in the years 2004–2019, with an annual average of almost 20%.

**Keywords:** electricity; production; consumption; rural areas; energy carriers; Poland

#### **1. Introduction**

Due to development, more and more energy resources are necessary to satisfy social needs as well as production. There is a growth trend in electricity consumption all over the world. Abolhosseini et al. [1] indicate that electricity consumption will constitute an increasing share of global energy demand over the next two decades, contributing to climate change and environmental pollution, and constituting a serious threat to human health. Energy is therefore a crucial element of the European Union's sustainable development strategy.

Climate problems in EU countries are noticeable as issues that may significantly affect or limit future socio-economic development. The cause of climate problems is the increasing emission of greenhouse gases due to anthropogenic activities directly related to the combustion of fossil fuels for electricity, heat, and transport. However, it is primarily the combustion of fossil fuels that causes atmospheric pollutants that are harmful to the environment and human health. Fossil fuels play a dominant role in global energy systems [2]. They are responsible for more than 70% of world greenhouse gas emissions [3]. In 2019, the largest share of greenhouse gas emissions, 77%, was those related to energy production [4], while, in 2015, this share was 78% [5].

**Citation:** Siemi ´nski, P.; Hady ´nski, J.; Lira, J.; Rosa, A. Regional Diversification of Electricity Consumption in Rural Areas of Poland. *Energies* **2021**, *14*, 8532. https://doi.org/10.3390/ en14248532

Academic Editor: Ashish Prakash Agalgaonkar

Received: 6 October 2021 Accepted: 14 December 2021 Published: 17 December 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Coal is the most damaging fossil fuel for environmental concerns and carbon emissions. In many countries, it is increasingly being replaced by natural gas for electricity production. However, reserves of coal could last a long time and still play a role in meeting primary energy demand [6]. Poland is rich in energy resources, with hard coal and lignite, i.e., energy resources with a potentially high environmental impact, predominating [7].

The electricity market has a dominant position among other energy markets (heat, car fuel, etc.) in terms of the scale of production.

In the EU, the greatest role is played by the conventional energy sources, while a decrease in production has recently been observed (e.g., in the years 2017–2019 mean annual production was approximately 7% lower at 1.166 million GWh). Nuclear energy (0.729 GWh in 2019) is the second most important energy source in the EU.

Conventional energy production accounted for 42.8% of the total, while nuclear power rose to 26.7% of the total. In the EU countries, a considerable role is also played by wind power (13%) and hydro power (12%) (Figure 1).

**Figure 1.** Energy production in the EU countries in 2019 (%). Source: Eurostat.

In the EU, a significant problem in energy production is related to limited and rapidly depleting energy resources, thus resulting in the increasing dependence on imported energy. Net imports cover over 50% of gross available energy in the EU, with the energy dependence rate exceeding 50.0% [8].

Electricity consumption in the EU has been characterized by considerable changes. In the years 2005–2007, it increased rapidly, reaching its highest level of over 76,000 tonnes of oil equivalent (TOE) in 2007. This led to decisive action aimed at reducing this trend. In the following years, a decrease was observed, which may be connected with the consequences of the economic crisis in Europe. Slight increases in the successive years did not cause an increase in energy consumption over the 2007 level, whereas, at present (Table 1), a marked economic slowdown triggered by the negative effects of the Covid-19 pandemic has led to a decrease in energy consumption and a general reduction in negative anthropogenic impacts on the natural environment.

The data in Table 1 indicate that Poland is one of the EU's highest electricity consumers. At the same time, it predominantly relies on conventional energy sources (Figure 1). Solutions and regulations are being sought to minimize electricity consumption, regardless of the current condition of the economy. However, it is crucial to ensure the country's energy security [9].

EU policies set objectives that are important for global priorities for the protection and conservation of the natural environment. The effects of these policies can be identified, among others, in Poland, where dynamic changes in the diversification of energy generation are taking place, which is confirmed by the research. It should also be noted that the energy market in Poland is undergoing dynamic changes which greatly affect rural areas. At the same time, the level of regional development determines the development of the electricity market.


**Table 1.** Electricity and heat generation in the EU countries (thousand tonnes of oil equivalent).

Source of data: Eurostat.

This article aims to present:


The research was conducted at the regional level (NUTS 2 until 2017). Secondary data from the Central Statistical Office (GUS) in the Local Data Bank were used, along with information from the European Commission and Eurostat websites.

The research problem is important from the point of view of sustainable development and environmental protection as well as the economic security of electricity consumers. This paper does not discuss all the aspects of energy economics; however, the analysis covered two key issues, i.e., the production and consumption of electricity.

#### **2. Background and Literature Review**

#### *2.1. EU Energy Policy*

Energy policy must be long-term and beneficial to all member states. Accordingly, the EU is implementing an energy policy covering the full range of sources, from fossil fuels to nuclear and renewable energy. The goal is to transform economies into lowenergy economies while ensuring greater security, competitiveness and sustainability of the energy used.

It may be assumed that the EU project, consisting in the integration of economies after WWII and peaceful cooperation between countries, was based, among other things, on energy policy initially related to the coal market and, subsequently, also to nuclear energy. The foundations for this process were laid by the Treaty of Paris, establishing the European Coal and Steel Community (ECSC) signed in 1951, which entered into force on 23 July 1952. At that time, coal was the main energy source worldwide, and it accounted for approximately 70% of the total. The energy balance of the six member states showed considerable differences between individual countries, since in France it was approximately 60%, whereas in Luxembourg it amounted to 95% [10]. In view of the current actions aiming at the establishment of a common energy market for the EU member states, cooperation within ECSC may be considered as the foundation for a common energy policy [11]. In turn, the Energy Card Treaty signed in 1991 by 46 countries is a document of significant importance, providing grounds for actions aimed at the improvement of energy efficiency and thus also the energy economy [11,12]. In their study, Grycan et al. indicated the following most important regulations in this respect [12]:


It seems that a milestone in the EU energy policy was the adoption of a strategy establishing the energy union, which reflected the new concept of energy security for the EU countries [13]. Its aim was to establish the energy union, which would provide secure, sustainable, competitive and reasonably priced energy supplies to EU households and enterprises.

A natural continuation of actions related to the development of the energy union was provided by the "clean energy for all Europeans" package [14]. Its objectives included, first of all, energy efficiency and increased energy production from renewable sources, with the simultaneous assurance of cheap energy accessible to all consumers. Thanks to the implementation of measures leading to modernization of the EU economies (Figure 2), it is assumed that the intensity of CO2 emissions will be reduced by over 40%, while renewable sources will account for approximately 50% all electricity [15,16]. A significant component in this reform package for the energy market is related to the need for a 10-year integrated national energy and climate plan for the years 2021–2030.

The EU energy policy in the 2030 perspective—setting out national strategies—includes three primary goals [17]:


Both for the Polish economy and the entire population, an important planning document is the Energy Policy of Poland by 2040 (PEP 2040) [18], which has been considerably modified by arrangements in the climate and energy policy adopted at the EU level. The essence of Poland' energy policy by the year 2040 is based on three pillars:


The above-mentioned three pillars of the energy policy comprise eight specific goals, of which some directly concern the power sector, including green power engineering, which jointly constitute an energy supply chain, starting from the acquisition of raw materials and energy generation and supply, as well as energy use and sale, at the same time maintaining energy security for consumers.

#### *2.2. Economic Transformation for Sustainable Development*

The EU energy policy indicates the direction of activities oriented towards sustainable development, of which energy is an essential factor.

The concept of sustainable development [19–22] in the following decades was acknowledged and incorporated into various forms of socio-economic development.

The concept of sustainable development includes the following aspects: humans as subjects affecting the environment, our planet as an object of human activity and the mode of action, i.e., partnership, since only integrated measures will facilitate achieving the goal of the concept, i.e., sustainable prosperity [23]. Thus, sustainable development promotes environmental protection and, by preventing the over-exploitation of natural resources, it protects them for future generations.

**Figure 2.** Role of the energy union and climate action. Source: [23].

In the EU countries, the concept of sustainable development has been an important part of economic development strategies for several decades. It is incorporated into the strategic socio-economic policies in all these countries, while being based on climate stability. When considering the implementation of sustainable development, we need to focus on the Europe 2020 strategy and the European Green Deal. One of the leading directions for the implementation of sustainable development within the Europe 2020 strategy has been connected with meeting the requirements of the climate and energy policy in the EU. In terms of the operations, it is intended to achieve goals such as a reduction in CO2 emissions and reduced consumption of fossil fuels, particularly coal, since this exhibits the greatest emission loads. Such goals are to promote a low-emission economy, protecting sustainable resources both for the present and future generations. Figure 3 presents the primary environmental goals of Agenda 2030 and the Europe 2020 strategy as an intermediate stage in the execution of the ultimate goals. The goals established provide direction to national changes in the energy policy in the EU countries.

There are paths ("trajectories") to the RES target, i.e., presentations of the rate of implementation of the contribution in the period 2021–2030. These are agreed on individually with each country; however, they are not arbitrary. The regulations indicate the minimum levels of RES share in specific years [24]:

• In 2022—at least 18% of the planned (for 2030) RES growth share in the period 2021–2030;


Within the next three decades, more ambitious goals have been proposed for sustainable development in the EU countries by updating the list of climate and environmental problems which need to be solved, as specified in the European Green Deal strategy [26–29].

The European Green Deal (Figure 4) is a new strategy for growth, aimed at transforming the EU into a fair and prosperous society with a technologically advanced, resourceefficient and competitive economy, which will reach zero net greenhouse gas emissions by 2050 and within which economic growth will not be dependent on the consumption of natural resources [26].

**Figure 4.** The European Green Deal. Source: [26].

Such a goal is a very ambitious developmental challenge both economically and socially. However, it is advisable to undertake such challenges considering potential benefits resulting from the reduction or possibly even halting of the progressive increase in global temperatures and environmental degradation, as well as the resulting climate change. The European Green Deal 2050 adopted by the EU is in line with the guidelines for the protection of climate and the natural environment within the UN 2030 sustainable development agenda, i.e., actions undertaken on the global scale in terms of environmental protection and responsible environmental management.

The essence of the EU economic transformation aimed at a sustainable future will be based on the joint funding of green investments and the simultaneous financial involvement of public and private stakeholders in the transition process. Moreover, it needs to be a just transformation, concentrating on the regions and sectors that will suffer most from its consequences due to their dependence on fossil fuels and high-emission processes. Within the cohesion policy, the Just Transformation Fund (JTF) is a new financial instrument covering the years 2021–2027, providing financial support to regions suffering serious socioeconomic problems resulting from the transformation aimed at climate neutrality [27–29]. The Fund resources will curb the negative social, economic and environmental impacts of the energy transformation. Most probably, the funds will provide support to beneficiaries from the Sl ˛ ´ askie, Dolno´sl ˛askie and the Wielkopolskie provinces, while the government is also trying to make the support available also to the Lubelskie, Łódzkie and Małopolskie provinces. Nevertheless, the national budgets will continue to play a key role in the green transformation processes, among other things using green budgeting tools, facilitating the transition of public investment and consumption and tax systems to further environmental priorities and reduce further degradation of the natural environment.

Realization of the economic transformation towards a sustainable future for the EU countries will be based on the following strategic tasks:


Gradual and successful implementation of the strategic tasks in the following years will result in positive changes, while, at the same time, the EU countries may become world leaders in preventing climate change and environmental degradation.

In view of these expected changes, the Executive Vice-President of the European Commission Frans Timmermans stated: "*We must show solidarity with the most affected regions in Europe, such as coal mining regions and others, to make sure the Green Deal gets everyone's full support and has a chance to become a reality*" [30].

As indicated by Jonker and Krukowska [31], the creation of "green economy" in all industrialized countries will establish a boundary between the two eras. A green economy is a circular economy. Its essence is manifested in the fact that changes progress from one phase to the next, followed by the return to the transitional phase, which reverses the previous linear economic system if changes follow the "make-take-dispose", stepby-step direction. The term green economy was first used by David Pearce [32], who observed that sustainable development is impossible in the current economy dependent on depleting resources such as oil and coal [33]. The green economy model involves low carbon dioxide emissions, efficient utilization of natural resources and the inclusion of all groups and individuals.

A green transformation both of the global and EU economies is becoming an increasingly accepted form of economic development. Such a socio-economic development is more and more universally accepted thanks to the potential positive effects of the green economy, with its environmentally friendly development pattern. Another crucial aspect is connected with the fact that the green transformation is to be a fair one, which means that inhabitants of the affected regions will not be disadvantaged and left alone but will be presented with a viable alternative. Such an approach seems to be highly beneficial for Poland, since our country may be the greatest beneficiary of this fund, with the allocated financial resources reaching two billion euro, i.e., approximately a quarter of the entire JTF. However, it needs to be remembered that the real absorption of funds is dependent on the acceptance of the Paris Agreement goals by the prospective beneficiary. For the time being, Poland is the only country which has refused to join in the climate neutrality goal, arguing that this stems from the specific character of its domestic energy sector, which needs much more time to adapt to changes, while automatic acceleration of energy transformation would involve huge social costs, greatly exceeding the amount allocated to Poland in the JTF. As a result, the real funds would be only 50% of those originally allocated.

The success of the green transformation in the EU countries, aimed at achieving climate neutrality by 2050 through the decarbonization of economies, will depend to a considerable extent on transformation programs such as the Regional Just Transformation Plans. In the opinion of officials from the Ministry of Development Funds and Regional Policy " ... *the aim is to develop plans, which will ensure sustainable and just solutions for mining regions. The Regional Just Transformation Plans need to be compatible with the national energy and climate plans*" [34].

#### *2.3. Challenges in the Strategic Goal: Provision of Clean, Reasonably Priced, and Secure Energy*

In view of prevention of further climate change and progressive degradation of the natural environment throughout the EU, the primary issue is to implement the strategic goal ensuring the "provision of clean, reasonably priced and secure energy." EU countries' previous experience indicates that over 75% of greenhouse gas emissions are generated by the production and use of energy [35]. Such a high share of greenhouse gas emissions from the energy sector results from the predominant use of carbon energy carriers. To date, less than 18% of gross final energy consumption in the EU countries in 2017 has come from renewable energy sources [36]. The forecast objective in this respect in 2020 was 20%. In view of the current data in some EU countries, there is a risk of failing to reach the expected objective, with a serious risk of such failure indicated for such countries as Belgium, France and Poland, while a moderate risk is suggested for Luxembourg and the Netherlands. In turn, based on estimates for all the EU-28 countries, the probable share of renewable energy

in 2020 was approximately 23% (For the group of EU-27 countries (excluding Great Britain) this level will amount to approximately 24%.); thus, it would be higher than expected [37]. This indicates the internal diversification between the EU-28 countries in terms of the development of renewable energy and achieving the adopted goals. The energy sector based on renewable energy needs to be further developed. To a considerable degree, this will facilitate the elimination of coal as the main source of energy, while at the same time reducing the emission levels in the economy.

The transition to clean energy is a long-term process, consisting of the transformation of the power engineering system; while ensuring the effectiveness of these changes, it will be necessary to involve all consumers and gain their acceptance thanks to the economic benefits offered and the awareness of the need for change. In the transition to clean energy, a key role will be played by renewable energy sources. The European Commission Communication [29] expressed an opinion that: "*Increasing offshore wind production will be essential, building on regional cooperation between Member States. The smart integration of renewables, energy efficiency and other sustainable solutions across sectors will help to achieve decarbonisation at the lowest possible cost. The rapid decrease in the cost of renewables, combined with improved design of support policies, has already reduced the impact on households' energy bills of renewables deployment*".

Nevertheless, some households still face the problem of energy poverty [38]. In view of the above, considering the poorest part of the population, special measures need to be introduced to protect financially stressed households when they cannot afford indispensable energy services to maintain a basic standard of living. The most important role is played by effective initiatives, e.g., those which may in the future reduce energy bills and which, through specific solutions, will have a positive and advantageous impact on the condition of the natural environment.

At present, individual countries are only starting the long process of transition to a lowemission power generation system and the low-emission economy. Profound changes related to energy transformation will require considerable public and political support. It is energy prices and the costs of energy transformation that should stimulate market transformation to achieve a climate-neutral economy within the next few decades. To ensure the success of the entire transition process, it is essential for energy consumers, both households and businesses, to have access to reasonably priced energy. In the last five years, an upward trend for wholesale electricity prices has been evident in the EU countries, followed by rising retail prices for end users. A culmination of the wholesale price increases was recorded in 2018, followed in 2019 by a reduction in prices mainly thanks to decreasing consumer demand as well as the rapid increase in the supply of renewable energy. In the EU countries, this phenomenon was far from universal; as a result, the diversification in price levels between the regional markets grew. In the first half of 2020 compared to the analogous period in 2019, prices dropped by 30% in some regional markets in southern Europe and up to 70% in certain northern regions [39]. This diversified reduction is explained by insufficient interconnection capacity, differences in the production of renewable energy on individual markets and the considerable growth of CO2 prices, which had a considerable impact particularly in the EU countries with greater shares of fossil fuel in their energy basket. Thus, it stresses the need for additional investment in grid flexibility, transboundary transmission capacity and renewable energy sources, particularly in EU countries that are falling behind in this respect, which should, in the future, result in greater price integration of electricity between the regional markets and benefits for consumers. Taking the existing needs into consideration, achieving climate neutrality requires an intelligent infrastructure. Strengthening transboundary and regional cooperation between countries will benefit from the transition to affordable clean energy. Thus, it will be necessary to review the frameworks regulating the energy infrastructure, including the TEN-E regulation 12, in order to ensure cohesion aimed at climate neutrality. These frameworks need to promote innovative technologies and infrastructure, such as intelligent grids, hydrogen networks or the capture, storage and disposal of carbon

dioxide as well as energy storage, while facilitating sector integration. Nevertheless, the general public has to realize that certain existing facilities and infrastructure will have to be modernized to further serve their role and resist climate change.

Energy consumers may be concerned about price levels on the retail electricity markets since, in the last decade, these have kept rising. In the years 2010–2019, electricity prices for households were increasing at 2.3% annually, while the general prices of consumer goods increased by 1.4% [39]. Over the same period, an increase was also recorded for electricity prices for business consumers; however, in this case, the annual mean growth rate was 1.1%. In turn, for energy consumers such as large industrial enterprises, energy prices decreased by 5%, in the 2010–2019 period; thus, they were advantageous for this group of consumers. Energy prices for the end users are determined by a variety of factors. These obviously include wholesale prices, but also grid charges as well as taxes and other fees, such as the current subsidies for renewable energy or the costs of energy-supply commercialization. At present, it is taxes and charges that are the most important cause of differences in retail prices at the regional level.

Results of the latest analyses of energy prices in the EU have confirmed considerable differences in taxation of electricity consumption between individual EU countries and, as a consequence, the impact of this element on retail energy prices. In 2019, environmental taxes paid by households ranged from 1 EUR/MWh in Luxembourg to 118 EUR/MWh in Denmark, while VAT rates ranged from 5% in Malta to 27% in Hungary. Fees charged on renewable energy range from 3 EUR/MWh in Sweden to 67 EUR/MWh in Germany. Moreover, in most countries, taxes and fees, as well as grid charges (i.e., the two price elements defined based on regulatory measures), considerably exceed the element imposed on energy and determined by market mechanisms.

#### **3. Materials and Methods**

This study is based on data from the Local Data Bank of the Central Statistical Office (Statistics Poland), titled *Electricity in households by consumer location* [40]. Moreover, both national and international reports were used along with numerous studies concerning electricity production and consumption in general, particularly in rural areas. The problems investigated were analyzed in terms of development conditions resulting from the EU development strategy by 2050 referred to as the European Green Deal and the Energy Policy of Poland by 2040.

The primary aim of this study was to identify homogeneous groups of provinces (województwa) characterized by a comparable rate of change in electricity consumption considering changes observed in rural areas. Moreover, the level, directions and rate of changes in electricity generation and consumption were also investigated.

The subject of studies on the energy economy presented in this paper are related to energy production, taking into consideration energy carriers used in the generation processes and electricity consumption in households by consumer location. Thus, energy consumption was analyzed separately for rural areas compared to urban areas or the overall consumption on the national level.

In the case of electricity production, its generation was analyzed for two periods, 2004 and 2019. In this way, the direction of change, the dynamics and the mean annual rate of change in electricity production in Poland were compared for these two periods, considering the environmental impact of energy generation processes, and assuming that an advantageous situation would be manifested in a situation considered to be desirable, i.e., the share of energy generated using fossil fuels will decrease in successive years, being replaced by renewable energy. In the case of electricity consumption in households, the time frame for the analyses covered the years 2004–2019.

A separate analysis was conducted for energy consumption in households in rural areas and in urban areas, thus identifying existing trends in this respect. It specified which of the areas contributes to a greater environmental load in absolute terms, resulting from higher electricity consumption. The rate of change in electricity consumption was also determined on a regional scale divided into rural and urban areas, which made it possible to identify which of the areas contributed to a greater environmental load related to growing electricity consumption in the period investigated. With the implementation of development assumptions stipulated by the EGD 2050 and a reduction in the negative anthropogenic impact on the environment, particularly by supplying clean and environmentally safe energy, it is crucial to have knowledge on the effect of these phenomena both in rural and urban areas. Insight into this problem will facilitate appropriate and adequate preventive or countermeasures addressing the needs identified. The degree of similarity was determined for the distribution of electricity consumption in the spatial unit system in rural and urban areas, applying Florence's coefficient [L1] as presented by [41]:

$$L\_1 = \frac{1}{200} \sum\_{i=1}^{n} |u\_{ir} - u\_{is}| \tag{1}$$

where *uir* = *yir* ∑*n <sup>j</sup>*=<sup>1</sup> *yjr* ·100% and *uis* <sup>=</sup> *yis* ∑*n <sup>j</sup>*=<sup>1</sup> *yjs* ·100% are percentages of the <sup>Y</sup>*<sup>r</sup>* and <sup>Y</sup>*<sup>s</sup>* features, respectively, and *n* denotes the number of objects (*i* = 1, 2, ··· , *n*).

The total coefficient of localization L1 assumes values in the range of <0, 1>, with the closer its value is to one, the greater the degree of discrepancy for the characteristic, while the closer the value is to zero, the greater the similarity.

Moreover, the degree of concentration of absolute electricity consumption in the system of spatial units in rural and urban areas made it possible to identify the degree of discrepancy in electricity consumption by provinces, while Florence's coefficient [K1] was applied as proposed by [41]:

$$K\_1 = \frac{1}{200} \sum\_{i=1}^{n} \left| u\_i - \frac{100}{n} \right| \tag{2}$$

where *ui* = *yi* ∑*n <sup>j</sup>*=<sup>1</sup> *yj* ·100% is the percentage of the examined feature Y, and *n* denotes the number of objects (*i* = 1, 2, ··· , *n*).

Values of the coefficient are found within the range of <0, 1>, with the coefficient value of 0 indicating a uniform distribution, i.e., lack of concentration, while the value of 1 denotes complete non-uniformity, i.e., complete concentration of the trait analyzed.

Analysis of the rate of changes made it possible to identify the existing trends in energy consumption in urban and rural areas. This was calculated on the basis of values throughout the entire period analyzed, which covered the years 2004–2019, applying the formula [41]:

$$r\text{gy} = \frac{-3m + \sqrt{9m^2 + 24m\left(n - 1\right)\left(\frac{1}{y\_1}\sum\_{t=1}^{n} y\_t - n\right)}}{2m(n - 1)}\tag{3}$$

where: *yt* denoted the observation of the feature Y in the period *t*, *m* = *n*(*n* + 1) and *n* is the number of periods (*i* = 1, 2, ··· , *n*).

Moreover, using the rate of change, the provinces were divided into homogeneous classes in terms of the scale of changes observed. This made it possible to distinguish regions of greater area, in relation to which similar instruments may be applied in the future to boost environmentally friendly actions. The classification of provinces from the high to the low rate of change was based, e.g., on an analysis of differences in the values of the rate of change. After the ordering of provinces according to the non-growing values of the rate of changes, differences were calculated between its values for neighbouring provinces, i.e., for the first and second, the second and the third, etc. Analyzing successive differences starting from the first (the difference between the second and the first province), a markedly higher value of this difference from the others will make it possible to distinguish classes of province with the highest rate of change, while the successive differences make it possible to identify the successive class.

#### **4. Results**

#### *4.1. Electricity Production in Poland*

Analysis of the national energy system in 2004 and 2019 indicates advantageous changes in Polish electric power engineering in view of the goals of the energy policy by 2040. Between 2004 and 2019, a simultaneous increase was recorded in installed capacity and electricity production. The growth dynamics of installed power in that period amounted to almost 35%, while electricity production increased by 3.5%; thus, it was ten times lower. In 2004, total installed power was almost 35 GW, while it grew in the successive years to reach almost 47 GW in 2019. Both in 2004 and 2019, the energy system was based primarily on carbon-based sources, with their share of the installed power types in power plants amounting to almost 60% and 50% for coal and 25% and 18% for lignite. Thus, in the next fifteen years, the share of carbon-based sources decreased by a total of approximately 17 p.p., including almost 10 p.p. for coal and by approximately 7 p.p. for lignite. In the analogous period, a gradual increase was observed in installed power based on gas-fired power plants, from less than 770 MW to almost 2800 MW, while their share in the structure amounted to 2.2% and 6%, respectively, i.e., it continued to be rather marginal despite the increase.

The analysis of data also showed that, in the following years, Poland realized that the process of gradual elimination of lignite as an energy source and a decreasing role of lignite-fired power plants in the national energy production system is indicated by the negative growth rate of installed power, the mean annual value of which was −0.33% in the years 2004–2019.

In view of the challenges resulting from the implementation of the Polish energy policy by 2040 in the successive decades, in line with the guidelines in the EGD 2050, particularly provision of clean and secure energy, in the last fifteen years advantageous changes were introduced in the national electric power engineering system in Poland. First, in the successive years since Poland's accession to the EU, interest in renewable energy has been increasing.

According Arıo ˘glu et al. [42], renewable energy is becoming the fastest growing energy source in the world. Gielen et al. [43] also note that renewable energy can meet two-thirds of the total global energy demand and, to a large extent, contribute to the reduction in greenhouse gas emissions responsible for climate change.

While, in 2004, wind power plants and renewable energy systems did not exist in Poland on a broader scale, by 2019 they had become a relatively important source of power in the national energy system. In 2019, wind power plants and other renewable energy sources accounted for almost 7500 MW, and their share in the total structure was 16%, i.e., slightly less than the share of lignite-fired power plants (17.9%), at the same time being over two-and-a-half times greater than gas-fired power plants (6%) (Table 2). Simultaneously, in 2019, the production of what is defined as clean and secure energy in the regulations adopted within the EGD 2050 amounted to more than 14,000 GWh in Poland, at 9% of energy generation. This share exceeded that of energy from gas-fired power plants by 1.5 p.p. and was as much as six times greater than energy from hydro power (1.5%). The conclusions provided by the observations of changes to hydro power in Poland between 2004 and 2019 are disturbing. This results from the drop in the energy generated from more than 3500 GWh in 2004 to less than 2500 GWh in 2019. The negative direction of change confirms the negative mean annual rate of change, which amounted to almost (−2.4%) and, at the same time, was the highest of all other energy sources. This is a greater reduction than in the case of coal-fired power plants (mean annual decrease of less than minus 0.6%) and lignite-fired power plants (mean annual decrease of approximately minus 1.5%). In view of the energy generation conditions in Poland, the most pressing need to reduce the energy sources in the national energy production system concerns coal- and lignite-fired power plants. Experience from the last fifteen years shows that this process is taking place in Poland; however, at a very slow rate. In view of the implementation of the objectives of the national energy plan PEP2040 and EGD 2050 in the coming years by

providing consumers with clean and secure energy, further development of wind power and the use of other renewable energy sources needs to be promoted, together with the further development of gas-fired power plants, since this type of energy has a much less negative environmental impact. Experience in this respect obtained in the last fifteen years indicates that, in Poland, the use of gas in energy generation was developing dynamically, as indicated by the dynamics of change, amounting to almost 320%, as well as the high mean annual rate of change, which was positive and amounted to approximately 8% for this type of installation.


**Table 2.** The National Electric Power System in Poland in 2004 and 2019.

Source: [44,45].

#### *4.2. Electricity Consumption in Poland Rural vs. Urban Areas*

Since Poland became an EU member, the entire country, including rural areas, has received new development opportunities. Accession to the EU and the related development policies, particularly the cohesion policy and the CAP, as well as the trade and industrial policies, provided a new economic and social quality. An important impulse for development has related to the targeted support from the EU funds addressing rural development in Poland. For example, allocation and utilization of the EU CAP funds are typically almost twice as high in Poland as the EU mean (the Polish agri-food sector and rural areas after ten-year EU membership—a review of major changes in 2014). Thus, the transfer of funds, also including public funds, has contributed to a boost in economic activity, which has been manifested in increased electricity consumption. Economic activity in rural areas measured by the number of economic entities in the REGON registry has improved considerably, as indicated by the almost 25% increase in 2018 compared to 2010 (at that time there were 1.2 million out of the total 4.4 million entities), whereas, in towns and cities in the same period, the increase was as little as 8% [46].

Electricity consumption in Polish households in the last fifteen years has grown continuously. In 2004, it was 22.8 TWh, while, in 2019, it was 30.6 TWh, i.e., the absolute increase amounted to 7.8 TWh, or approximately a third in absolute terms (Figure 5). A particularly marked increase was recorded for energy consumption in rural areas, in 2004 consumers in those areas used 6.3 TWh electric energy, while in 2019 it was 12.7 TWh, an increase of 6.4 TWh. Rural areas were thus responsible for an over 80% increase in electricity consumption in Poland. This phenomenon was becoming even more pronounced in the successive years, since, while the share of rural areas in electricity consumption in Poland in 2004 was below 28%, in 2019 it reached over 41%. Rural areas in Poland are thus characterized by growing needs in terms of electricity supply. This is confirmed by the dynamics of changes in electricity consumption. While, in the extreme years, this amounted to slightly over 34%, in urban areas it was less than 10%, then in the same period in rural areas it was ten times higher, amounting to almost 100%, which shows a doubling of electricity consumption (Table 3). In the regional system, the dynamics of change in electricity consumption varied between individual provinces (Table 3). First of all, it may be observed that, in contrast to rural areas, electricity consumption in urban areas is generally characterized by minor changes. In provinces such as Pomorskie, Łódzkie and Warmi ´nsko-mazurskie, a highly stable level of energy consumption was recorded, while the dynamics of change in 2019 compared to 2004 did not exceed 2.5%. Rural areas exhibited a much greater dynamic of electricity consumption in the years 2004–2019. In certain provinces, energy consumption increased several-fold. In the Podlaskie province, electricity consumption increased five-fold, while in the Łódzkie and Lubelskie provinces a minimum three-fold increase was recorded.


**Table 3.** Dynamics of change in electricity consumption in Poland (GWh).

Source: [44]. https://bdl.stat.gov.pl/BDL/dane/podgrup/temat/11/57/1880, accessed on 12 September 2021.

Mean annual rate of change in electricity consumption in households (Table 3) in rural areas of Poland on average was almost nine times greater than in urban areas, 6.51% compared to 0.74%. The greatest growth rate for electricity consumption in rural areas was found in the Podlaskie and Lubelskie provinces, at almost 20% and 12.5%, respectively (Table 4).

**Figure 5.** Electricity consumption in households in Poland in the years 2004–2019 (TWh). Source: [44].


**Table 4.** The rate of change in electricity consumption in households in Poland in the years 2004–2019 (%).

Source: authors' calculations based on Local Data Bank [44], https://bdl.stat.gov.pl/BDL/dane/podgrup/temat/ 11/57/1880, accessed on 12 September 2021.

Analyzing unit electricity consumption in Poland in the years 2004–2019 (Figure 6), i.e., per capita, with the division into rural and urban areas, it may be indicated that a characteristic event took place in 2014. For the first time in Poland, unit electricity consumption was higher in rural areas than in urban areas—by 1.4%. In the following years, this phenomenon grew. As a result, in 2019, unit electricity consumption in rural areas was already 6.3% higher and amounted to 827 kWh compared to 778 kWh.

A comparison of the degree of concentration of electricity consumption by provinces between rural and urban areas suggests a low degree of concentration for electricity consumption by province both in rural and urban areas (Table 5). Analogously, a close similarity is also observed in electricity consumption between rural and urban areas, as evidenced by similar values of the coefficient of similarity according to Florence (Table 5). In Poland, only in the Podlaskie province in the years 2004–2019, was a high growth rate for electricity consumption observed (Figure 7). In the next five provinces, i.e., Mazowieckie, Lubelskie. Podkarpackie, Swi ˛ ´ etokrzyskie and Łódzkie, electricity consumption increased at a medium rate. In the other provinces, it exhibited a low growth rate.

**Figure 6.** Unit electricity consumption in Poland (kWh/per capita). Source: authors' calculations based on Local Data Bank [44].

**Figure 7.** Regional variation in electricity consumption in rural areas of Poland in the years 2004–2019 according to mean annual rate of changes. Source: authors' study based on Table 3.


**Table 5.** The degree of similarity and concentration of electricity consumption.

Source: authors' calculations based on Local Data Bank [44].

#### **5. Discussion**

The energy market in Poland is undergoing dynamic changes that affect rural areas. Since 2014, unit electricity consumption per capita in rural areas exceeded the level of consumption in urban areas. This relationship is permanent, since it has been evident in the following years, while, additionally, differences in the level of consumption also grew in subsequent years.

Rural areas in Poland are characterized by a growing need for electricity. The scope of the research made it possible to track the existing trends in electricity consumption. Moreover, the provinces of Poland were grouped based on the growth rate of their electricity consumption. Classes characterized by low, medium and high growth rates were distinguished. The analysis was carried out for rural areas in Poland, which show great

territorial differences in the level of socioeconomic development. This is understood as changes taking place in a direction that meets the collective and individual needs and individual aspirations of residents and local communities to an ever-greater extent [47]. At the same time, the level of regional development determines the development of the electricity market. The voivodships with a high and medium growth rate of electricity consumption include rural areas, which are characterized by a very low and low socioeconomic development.

The results indicate that, currently, rural areas contribute to the high adverse impact on the natural environment in Poland, which is the result of differences in specific energy consumption. In terms of the spatial arrangement, Podlaskie Voivodeship has a unique situation. This voivodeship had the highest increase in electricity consumption per capita in 2004–2019 (on average it was almost 20%).

The changes observed are related to the increase in economic activity in rural areas, the intensification of agriculture and the increase in the scale of livestock production on farms. According to Wójcicki [48], animal breeding is more energy-consuming than arable farming.

In Poland, Podlaskie Voivodeship has the highest cattle population per 100 ha of UAA. This creates excellent opportunities for biogas production due to the increased availability of the substrate. There are therefore possibilities to limit the negative impact of Podlaskie Voivodeship on the environment in the future. This reduces CO2 emissions, particularly those from rural areas, and reduces the electricity consumption generated from fossil fuels. In the conditions of the energy transformation consisting of abandoning coal, a good state energy policy is needed [49]. Also, activities at the regional level support the existing solutions at the national level, for example, support from EU funds for investments in agricultural biogas plants.

Experience from the global energy market shows that it is possible to shift from fossil fuels to clean energy as the world moves towards decarbonizing economies and reducing greenhouse gas emissions worldwide [50]. As a result, environmental targets are no longer seen as an obstacle to economic development but as a solution to economic and social development.

According to Kaygusuz [51], renewable energy sources are a desirable form of practical solutions in the energy sector to develop clean and sustainable energy to reduce environmental pollution.

Over ten years ago, Marecki [52] and Jaczewski [53] indicated that, around 2020, the following may be expected:


The results of the study confirm the accuracy of these forecasts; particularly in the Polish energy economy in the last fifteen years, a considerable increase has been recorded in natural gas consumption for electricity generation along with a dynamic development of renewable energy [54]. A gradual reduction in the use of coal for electricity production has also been observed, although the rate of changes in this respect is not adequate to meet the existing challenges. These gradual changes in the consumption of energy carriers are consistent with the strategic EU goals. Thanks to further actions resulting from the Polish national energy plan PEP 2040, in the coming years, the energy economy in Poland will be increasingly compatible with that of the EU.

Within approximately the last two decades, Poland has made progress in reducing the negative environmental impact of electricity production, and the reduction in coal and lignite consumption on average by 0.6% and 1.5% confirms this.

In the following years, the development of renewable energy generation may also be observed. In 2019, the share of electric energy produced by wind power as well as other renewable energy sources was 9%, while, together with hydro power plants, it amounted to more than 10%. Poland has reserves in the potential for clean energy generation, as indicated by the available production capacity which, for the two types together, amounts to 21% of total installed power in Poland.

Moreover, the realization of renewable energy investments with the support of EU funds in many local government units [54], also in rural communes, will, in the immediate future, bring an increase in the share of renewable energy.

Investments in renewable energy sources are desirable in rural areas. Sutherland et al. [55] highlight the countryside and the potential of agriculture to generate renewable energy. They indicate that, due to its historic commitment to managing essential resources, especially land and biomass, the agricultural sector plays, or at least can play, an important role in the transformation of renewable energy.

However, special care should be taken to ensure that the production of renewable energy in rural areas does not result in competition for food and energy resources, which could result in a deterioration of food security [56].

There are possible solutions that minimize the occurrence of such a phenomenon. According to Jasiulewicz [57], for example, to produce biomass, we should use lower quality soils that have been set aside, degraded or are at least not suitable for food production. The production of renewable energy in rural areas can also be based to a greater extent than before on biogas and the use of agriculture waste, which may be slurry or manure from the breeding of cattle, pigs or poultry [58–60].

#### **6. Conclusions**

Forecasted changes and the transformation of energy systems both in Europe and worldwide are taking place under the influence of the so-called development megatrends [61]. The most important of these in the European power engineering include decreasing costs of renewable, limitation of the environmental impact of the energy sector, the decreasing role of coal as an energy source and new business models in power engineering. On the international and EU scales, in the last five years, we have witnessed many crucial events and agreements, which, during the coming decades, will influence changes in the energy sector. These include the Paris Agreement on the global reduction of climate change, the adoption of the European Green Deal 2050, aimed at a zero-emission economy, and actions to introduce the Energy Union. National energy policy needs to adapt to such conditions on the macro scale, as new challenges have also appeared. The most important of these include the following issues: how to ensure energy security in a changing energy market? What might the future role of coal be in energy economy? In what areas should the development of renewable energy sources be promoted? What should the rate of integration in the national electric energy market with the EU market be and, as a consequence, what should the European compromise for the energy sector be? [62].

Over the last five years, the problems of the energy economy have gained importance for the public. At the same time, they are a constant and essential aspect in the work of the EU summit meetings. The research problem discussed is important from the point of view of sustainable development, environmental protection and economic security of electricity consumers.

Actions aimed at the implementation of sustainable development result from the fact that, at present, it is universally acknowledged that the previous paths of socio-economic development and a recreation of previously grounded trends for economic growth disregarding broadly understood environmental, social and economic consequences should not be maintained in the future.

Sustainable development requires the application of prevention and, first of all, foresight, preferably in all areas of socio-economic life [63]. A form of prevention seems to be

enacting seeing changes in the consumption of electricity and the energy carriers used to generate it.

Based on experience, it is possible to reduce greenhouse gas emissions in the EU. This results mainly from reducing the use of hard coal and lignite in electricity production (in favor of increasing the importance of renewable energy). The effects of the 2005–2015 period showed that greenhouse gas emissions fell below the target set for 2020 [5].

**Author Contributions:** Conceptualization, P.S., J.H., J.L. and A.R.; methodology, P.S., J.L.; software, P.S., J.L.; validation P.S., J.H., J.L. and A.R.; formal analysis, P.S., J.H., J.L. and A.R., investigation, P.S., J.H., J.L. and A.R., resources, P.S., J.H., J.L. and A.R., data curation, P.S., J.H., J.L. and A.R.; writing—original draft preparation, P.S., J.H., J.L. and A.R., writing—review and editing, P.S., J.H., J.L. and A.R.; visualization, P.S., J.H. and R.A; supervision, P.S., J.H., J.L. and A.R.; project administration, P.S.; funding acquisition, P.S., J.H. and J.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was financed from resources of the Faculty of Economics Pozna ´n University of Life Sciences.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** Not applicable.

#### **References**


## *Article* **Economic Feasibility of Agricultural Biogas Production by Farms in Ukraine**

**Galyna Trypolska 1, Sergii Kyryziuk 2, Vitaliy Krupin 3,\*, Adam W ˛as <sup>4</sup> and Roman Podolets 1,\***


**Abstract:** Renewable energy generation in Ukraine is developing slower than state strategies and expectations, with the installations for energy generation based on biogas currently being among the lowest in terms of installed capacity. Most of those involved in energy generation from agricultural biogas are large enterprises, while the small and medium-sized farms are far less involved. Thus the article aims to assess the economic feasibility of biogas production from agricultural waste by specific farm types and sizes, with a special focus on small and medium-sized farms. The research results present findings in two dimensions, first defining the economic feasibility of biogas installations in Ukraine based on investment costs and the rate of return at both the current and potential feed-in tariff, and second, analyzing the influence of state regulation and support on the economic feasibility of agricultural biogas production in Ukraine. The results emphasize that the construction of small generation capacities does not provide sufficient funds under the current feed-in tariff to meet the simple return period expected by the domestic financing institutions. Except for the general support programs for agricultural activities, there are no support funds specifically for biogas producers, while there is tight competition with wind and solar energy due to diversified feed-in tariffs.

**Keywords:** agricultural biogas; farm; economic feasibility; investment; LCOE; state support; feed-in tariff; Ukraine

#### **1. Introduction**

Global climate change is increasing its tempo and impact [1] on humanity, while the origin of this change is primarily anthropogenic [2–5] due to the excessive negative influence of the intense use of fossil fuels and the consequent environmental pollution. A swift shift to renewable energy is among key solutions to this growing problem and needs to be implemented by all technically feasible means. These include energy generation from biogas, which is becoming an increasingly popular and important source of renewable energy from the standpoint of the circular economy [6–8], yet still falls behind the shares of solar and wind energy [9,10]. The global direct consumption of biogas in 2018 equaled ca. 35 Mtoe, including 16.1 Mtoe in Europe, 8.8 Mtoe in China and 4.0 Mtoe in North America [11].

While biogas can be generated from numerous types of organic waste, they can be aggregated into either of the two major ones: solid and agricultural. The latter includes the plant leftovers, weeds, leaf litter, sawdust, as well as the animal-originated solid, slurry and liquid waste. The utilization of biogas makes it possible to generate electricity and heat, reduce greenhouse gas emissions (methane and nitrous oxide from livestock waste), smooth overloads in the energy transfer grids and create new jobs in rural areas.

**Citation:** Trypolska, G.; Kyryziuk, S.; Krupin, V.; W ˛as, A.; Podolets, R. Economic Feasibility of Agricultural Biogas Production by Farms in Ukraine. *Energies* **2022**, *15*, 87. https://doi.org/10.3390/en15010087

Academic Editor: Attilio Converti

Received: 1 November 2021 Accepted: 15 December 2021 Published: 23 December 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Ukraine is often referred to as a country with substantial agricultural development potential [12–14]. The same applies to bioenergy generation, yet in this case, a distinction needs to be made between different sources. While the biomass from crop production is increasingly available due to the subsector's growth [15,16], the livestock sector has been declining drastically in the past 30 years [17,18]. Thus the production of biogas from livestock feedstock could simultaneously be a significant chance to intensify renewable energy generation [19,20], but a difficult task due to specific conditions of the livestock subsector's development.

The integration of livestock production with the agricultural biogas installation could be especially beneficial for small and medium-sized farms, as it would allow them to use the livestock waste (utilization of which is currently an additional economic [21,22] and environmental burden [23]) in order to increase economic viability and achieve their own energy security, as well as aid the achievement of national goals of energy independence, regional energy generation diffusion and increasing the number and capacity of renewable energy sources.

The combined model of biogas production and use, in which biogas can be produced simultaneously from different types of feedstock, is a common approach in the global perspective [24]. While the average efficiency of electricity production (excluding heat) is ca. 34.6%, the simultaneous production of heat and electricity (i.e., co-generation) increases the efficiency of the production plant to 76.4% (provided there are heat consumers present on-site). Heat can be used for agricultural premises (e.g., farms, warehouses, greenhouses, processing), residential premises or the social infrastructure.

Despite the obvious advantages of biogas production for farm income diversification, the spread of biogas plants is still quite limited in Ukraine [20], especially compared to more economically developed European countries [25,26]. In particular, as of 1 January 2020, there were 49 biogas plants in Ukraine [27], of which only 21 were utilizing agricultural waste products as their feedstock, compared to almost 10,000 similar plants in nearby Germany [28]. Researchers say the limitations lie in the regulatory field [29–32], the lack of substantiated and efficient state support for energy generation from biogas [29,33] and a low level of understanding of the benefits of renewable energy generation by private entities and individuals [30,34]. In our opinion, there is still a gap within the research aimed at deepening the technological and economic feasibility of biogas production, taking into account national, regional and local conditions, and the suitability of installations to particular types of entities (according to their sizes and economic potential).

Until now, the typical approach in research articles regarding the development of biogas in Ukraine has been rather general [16,17,25,29,31] or technology-focused [21,35–38], still lacking a well-substantiated focus on farms, yet even more on their different sizes. Some research analyzed small energy generation installations that would be most suitable for small entities [37,39,40], but these focused rather on overview statistical and analytical data or technological issues, omitting the economic feasibility component. At the same time, work mentioning economic feasibility issues for various sizes of generation capacity does not tackle the state support system [34,41–43], or they take into account the feed-in tariff system for the energy generation from biogas [32,33,44] but do not view them from the perspective of farm size. This creates a research gap, especially for the small and medium-sized farms taking account of the economic elements of the support system, which would help understand the limitations and possibilities of development of small- and medium-scale bioenergy generation capacity by farming entities and individuals.

The study thus aims to assess the economic feasibility of biogas production from agricultural waste by farms, with a special focus on small and medium-sized farms involved in cattle, pig and poultry. The following research objectives were set for this:


The manuscript is divided into six sections. Following the introduction, Section 2 describes the current state, official plans and potential of renewable energy generation and biogas production in Ukraine. Section 3 presents the materials used and methods applied within the research. The results in Section 4 present findings of two dimensions: the assessment of the economic feasibility of biogas installations in Ukraine and the analysis of the influence of state regulation and support on the economic feasibility of agricultural biogas production in Ukraine. Section 5 discusses the results obtained and compares the current state of agricultural biogas development with selected EU experience. Section 6 summarizes the results and defines limitations and possible future directions of research within the topic.

#### **2. Renewable Energy Generation and Biogas Production in Ukraine: Current State, Plans and Potential**

The development of renewable energy in Ukraine is taking place in accordance with the National Renewable Energy Action Plan through 2020 (NREAP2020 [45,46]) and the Energy Strategy of Ukraine until 2035 (ESU2035 [47,48]). According to the strategic goals set in the NREAP2020, by 2020, it was expected that 11% of the final energy consumption would come from renewable sources, while the share of electricity from biomass should have reached 16.2% (of which 2.6% is biogas), and 85.5% in heating and cooling systems (of which 2.6% is biogas). By 2035, the share of energy from renewable sources is to reach 25%, in accordance with ESU2035. The total installed domestic capacity of bioenergy (including not only biogas-based installations but also other biomass plants) reached 0.98 GW in 2020, 1.3 GW in 2025, 1.67 GW in 2030 and 2.13 GW in 2035 [49].

Current achievements in renewable energy in Ukraine indicate it is falling behind the targets. In particular, in 2019, the share of energy generated by renewable energy sources in gross final energy consumption reached 8.1%. An increase in energy consumption from renewable energy sources in 2019 by 9.1% (0.36 Mtoe) compared to the previous year and the general reduction in energy consumption (by 2.6 Mtoe) made it possible to achieve some overall progress in the development of renewable energy (Figure 1), yet the rate of implementation is still not sufficient to meet the goals.

**Figure 1.** Renewable energy generation shares (actual vs. planned) in final energy consumption in 2014–2020 in Ukraine (in %). Source: own compilation based on [50].

During 2015–2019, the renewable electricity capacity in Ukraine (excluding the temporarily occupied territory of the Autonomous Republic of Crimea by the Russian Federation) performing under the set feed-in tariff increased by 5965 MW (from 967 MW to 6932

MW). The overall capacity of renewable energy generation in Ukraine is currently (as of 1 January 2020) dominated by solar installations (71%), while biogas made up only 1.24% (Figure 2).

**Figure 2.** Renewable energy facilities functioning within the feed-in tariff as of 1 January 2020, by sources (in MW). Source: own compilation based on [50].

The development of renewable energy especially intensified in 2019. In that year alone, renewable energy facilities with a total capacity of 4642 MW were put into operation, which is five times the capacity installed in 2018. However, this was achieved mainly by expanding solar power plants: 76% of the total installed generation capacity in that year was from solar installations, while biomass and biogas grew by only 0.7% and 0.9%, respectively [50].

During 2019 the renewable energy facilities functioning under the feed-in tariff generated 5908 million kWh, of which: solar power plants generated 2932 million kWh, household photovoltaic stations generated 303 million kWh, wind power plants generated 2022 million kWh, small hydroelectric power plants generated 242 million kWh, biomass power plants generated 162 million kWh and biogas power plants generated 247 million kWh [50]. Thus the share of energy produced from biogas in 2019 amounted to 4.2% of the total from renewables. Of the total functioning 49 biogas plants, agricultural biomass is used as feedstock in 21 plants with a total installed capacity of 59 MW (Figure 3).

Energy generation based on agricultural biogas in Ukraine is currently carried out primarily by large agricultural or processing enterprises. Key factors of their intense involvement in this activity include large generation capacities, dependence on their own feedstock, a relatively high rate of return, state support and a greater ability to overcome bureaucratic obstacles.

Despite the rather limited overall development of biogas production, Ukraine has significant potential due to both the availability of feedstock and a developed gas distribution system, with ca. 70% of the population having direct access to the natural-gas grid. In 2018, the annual potential of biogas from agricultural waste, food industry and enterprises' wastewater was estimated at 7.8 billion m3 of methane [52]. According to the Bioenergy Association of Ukraine, the development of biogas use in Ukraine could potentially replace 2.6–18 billion m<sup>3</sup> of natural gas annually [53], thus strengthening national energy security. The latter is a crucial issue in light of Ukraine's high energy dependence on imported resources [54,55].

The use of agricultural biogas for energy generation in Ukraine has numerous advantages compared to other renewable energy sources [56]:


Studies by the Institute for Economics and Forecasting of the National Academy of Sciences of Ukraine [56] show that with the steady development of biogas production and use, its economically feasible potential could reach 9.9 Mtoe by 2030. The use of biogas replacing fossil fuels could result in greenhouse gas emission reduction within the range of 11.5–19.1 Mt CO2eq. In order to achieve this, the additional consumption of corn silage could reach 13.9 million tonnes. In order to implement the necessary biogas development projects, ca. EUR 4 billion is necessary for the heat and electricity generation field. The implementation of such projects in Ukraine could lead to numerous positive macroeconomic consequences, such as additional GDP growth of 0.3% in 2025–2029, structural changes, including the increased output of machinery and construction sectors, and a slowdown in coal mining. Despite the fact that biogas projects have almost no effect on the level of real household income (from −0.1 to 0.3%), they can potentially aid households by reducing their expenses, including those for heat and electricity.

#### **3. Materials and Methods**

Livestock manure is the most suitable feedstock for agricultural biogas production, with more liquified options such as slurry making it possible to increase methane output. It is being used as feedstock for reactors, where the fermentation process is initiated under appropriate conditions [64]. Pig manure is also well suited for biogas production but requires dilution with water. Poultry manure is suitable only in the cage systems, as the floor system increases the risk of the appearance of solid minerals in the manure, which adversely affects the reactor. However, poultry manure can be efficiently combined with livestock manure. By using pure poultry manure as feedstock, there is a danger of high ammonia concentrations; thus, it is crucial to adhere to the proper composition of the feedstock in accordance with the technological solution selected [65]. For small feedstock volumes, it is recommended to use biogas installations with a mesophilic temperature range and a twentieth of the daily load of the total feedstock volume accompanied by a slow stirring process (every 4–6 h).

As in agriculture, there are both specialized and mixed farms; the type determines the availability of feedstock for biogas production in terms of volumes and composition. In order to estimate the amount of manure available for production within a farm, data were used to estimate the yield of excrements depending on the animal species and their age [66]. These data were obtained from a specialized statistical survey of agricultural enterprises, which contains detailed information about 2860 farms in Ukraine keeping specific types of animals (cattle, pigs and poultry). The age structure of farm livestock was estimated on the basis of averaged data provided by the State Statistics Service of Ukraine and extrapolated for the farms analyzed. Coefficients of feedstock conversion into biogas made it possible to calculate the theoretical yield of biogas for each type of farm.

The study focused on the Ukrainian agricultural sector and took into account the following farm types: (1) agricultural enterprises and (2) farming households, yet only those that are either legal entities or private entrepreneurs (referred to in the text as registered farming households), thus excluding the smallest subsistence farms.

For the purposes of this research, the farm sizes were assumed based on the farm livestock (cattle, pigs and poultry) population. This assumption is necessary as Ukrainian legislation does not provide precise definitions of farm sizes, yet these are needed to understand the energy generation potentials based on their own available feedstock and typical features in biogas generation by small, medium-sized and large farms. Thus for cattle farms, the assumed distribution is as follows: small farms with a population up to 100 head, medium in the range between 100 and 1000 head, and large farms of over 1000 head. Small pig farms are assumed to have up to 200 head, medium farms have between 200 and 1000 head and large farms have over 1000 head. For poultry farms, the small ones are assumed to keep under 5000 head, medium farms keep between 5000 and 50,000 head and large farms keep over 50,000 head.

Given the technical limitations of manure use, the study assumes that a biogas installation uses 20% (in terms of energy content) of corn silage and 80% of manure as its feedstock. The capacity of a biogas installation that could be theoretically installed is estimated based on the availability of feedstock (volume of manure + silage). Thus the installation's capacity equals the annual volume of biogas multiplied by two and divided by hours in a day multiplied by days in a year (capacity = annual volume × 2/(24 × 365)).

As emphasized in Section 2, the practical possibilities for the utilization of biogas potential (as is also the case for other renewable energy sources) are determined by profitability. The approach to its estimation in the research is based on the concept of the Levelized Cost of Energy (LCOE). In order to obtain the results, the following assumptions were made:



Wherever applicable, the currency exchange rate from UAH to EUR was conducted based on the average rate of the National Bank of Ukraine for 2020, [68] at 30.79 UAH/EUR.

In order to calculate the cost of investment capital, it is assumed that the risk-free rate of return (e.g., on deposits) is set at 9% in Ukrainian currency (UAH), the annual interest rate on a loan is 19% in UAH, the share of equity capital is 30% (the remaining 70% is the loan capital) and the income tax rate is set at 18%.

In order to assess the feasibility of biogas installation, the authors used a simple payback period approach. The latter matters, as biogas technologies have relatively high investment costs, and the commercial banks in Ukraine tend to provide only mediumterm loans.

The materials used include the openly accessible data provided by the State Statistics Service of Ukraine [59], as well as an additional purchased database prepared by the State Statistics Service of Ukraine for 2015, which included solely the farms registered as mediumand large-scale agricultural enterprises, covering 59% of all cattle in the sector, 86% of pigs and 100% of poultry.

#### **4. Results**

#### *4.1. Assessment of the Economic Feasibility of Biogas Installations in Ukraine*

In Ukraine, the group of farms studied holds 33.4% of the total livestock, 59.1% of pigs and 57.4% of poultry (as of 1 January 2020). However, the availability of feedstock for biogas production is diverse, as farms differ substantially according to their livestock quantity. In particular, most farms that keep cattle fall into the categories of either 100–500 head and up to 50 head. However, farms with the largest number of cattle hold over 1500 head (Figure 4).

According to estimates, a 1 MW biogas installation requires ca. 6000 head of cattle. If only cattle manure were used (i.e., without corn silage), then ca. 10,000 head of cattle may be needed [69]. There are examples of such farms in Ukraine, such as the farm in Bziv village (Kyivska region), which has a biogas installation with a generation capacity of 330 kW, fed by 950 cows [70]. For 75 kW installations, ca. 500 head of cattle is sufficient [69].

**Figure 4.** Cattle farms in Ukraine grouped according to livestock quantity as of 1 January 2020. Source: own compilation based on data of the State Statistics Service of Ukraine [59].

There is a similar distribution for pig farms. The most numerous are small farms (up to 100 pigs) and medium farms (ranging between 200 and 499 pigs). However, the largest pig population is held on large farms with over 10,000 head (Figure 5).

**Figure 5.** Pig farms in Ukraine grouped according to livestock quantity as of 1 January 2020. Source: own compilation based on data of the State Statistics Service of Ukraine [59].

Concentration is even more visible on poultry farms. Most small farms have fewer than 5000 head of poultry. However, the total number of poultry kept is significantly dominated by large enterprises with over 500,000 head (Figure 6).

**Figure 6.** Poultry farms in Ukraine grouped according to livestock quantity as of 1 January 2020. Source: own compilation based on data of the State Statistics Service of Ukraine [59].

As already mentioned, the design of a biogas installation should take into account not only the amount of available feedstock (which directly depends on the number of animals on the farm) but also its composition. Based on the farm data, the share of farms within each livestock type that would be self-sufficient in terms of provision of feedstock for their potential biogas installations was estimated. These values are 33% for cattle farms, 30.8% for pig farms, 6.3% for poultry farms and 29.9% for mixed farms. The required biogas installation's capacity is calculated for each farm type based on the amount of its own available feedstock, maintaining a combination of 80% manure and 20% silage (Figure 7). The visualization shows the distribution of farms that can meet this constraint and makes it possible to see the shares of such farms from the smallest possible generation capacity.

**Figure 7.** Distribution of farms in Ukraine by potential biogas installation's capacity based on availability of own feedstock. Source: own calculations based on data of the State Statistics Service of Ukraine [59].

The theoretical possibility of the construction of a biogas installation should be consistent with its economic feasibility. This assessment was carried out on the basis of LCOE. Results of these calculations for different capacities of biogas installations are presented in Table 1.

**Table 1.** Levelized costs of electricity and heat generation by biogas installations of various capacities and corresponding investment return (simple payback) periods.


Source: own calculations.

As the results in Table 1 show, with the current renewable energy support system from biogas installations in Ukraine in the form of feed-in tariff at 0.1239 EUR/kWh, the construction of small-capacity installations (in our case, all types below 500 kW fall into this category) is not feasible, because:


Thus promoting the development of renewable energy generation from agricultural biogas by small and medium installations (from 100–500 kW) would require the introduction of additional stimulating measures for such farms.

Farms whose production of feedstock does not meet the necessary capacity of biogas installations of 100 kW and below could still be involved in the generation of renewable energy by cooperation with other farms. However, the economic feasibility of such cooperatives is limited by the transport costs; thus, the distance between them would need to be limited to ca. 20 km for liquid manure and ca. 50 km for dry manure. According to our estimates, in compliance with the above-mentioned criteria, it is possible to utilize up to 85.9% of feedstock from farms whose agricultural production volumes do not make it possible to meet the feasibility criteria for their own biogas installation.

#### *4.2. Impact of State Regulation and Support on the Economic Feasibility of Agricultural Biogas Production in Ukraine*

Currently, the main financial incentive for biogas projects in Ukraine is the feed-in tariff (called the "green tariff") introduced by the Law of Ukraine "On electricity" [72] and substantiated by the Law of Ukraine "On the electricity market" [73]. The feed-in tariff is set at 0.1239 EUR/kWh, and the state guarantees this until the end of 2029. In 2019, the opportunity to generate electricity from biogas was introduced for cooperatives with a capacity of up to 150 kW [74].

The downside is that the set feed-in tariff can be applied only to installations put into operation by January 2023 [75]. This latest legislation change introduced in July 2020 means that from 2023, all biogas installations, including small ones, will have to participate in state auctions to receive state support and qualify for the feed-in tariff. Participation in such auctions will be accompanied by an additional financial burden for producers, as each bidder for the right to participate in the auction must pay 5000 EUR/MW and an additional 15,000 EUR/MW if they win in the auction. This will limit the current financial benefits from biogas installations and will certainly demotivate potential investors. Thus possible investment return periods for biogas installations were assessed both according to the current conditions as well as those set to come into force from January 2023 (Table 2).


**Table 2.** Possible return periods of biogas installations according to selected generation capacity.

Source: own calculations.

Participation in auctions thus extends the simple return period of projects, yet the effect is not substantial. For large biogas installations, the fact of participation in the auction increases the cost of the project from EUR 20,000 to 400,000. For small installations, the increase ranges from EUR 0.5 to 10 thousand. Compared to the cost of biogas installations, this is not a large additional burden, but the question remains about the participation in such auctions, their clarity and level of bureaucracy. The key advantage of the auction system is that it guarantees the provision of state support for the next 20 years, while currently, the feed-in tariff is set to expire in 2029. However, the disadvantage is that according to [75], the only feed-in tariff for electricity generated besides wind and solar installations cannot exceed the above-mentioned 12 eurocents/kWh, which means that biogas projects are unprofitable for small producers due to the lack of a flexible economic support mechanism. It was estimated that the feed-in tariff would have to be increased to at least 0.3 EUR/kW if the state was aiming to support the development of small biogas projects based on livestock waste.

The legal basis for the introduction of feed-in tariff auctions in Ukraine was enacted in 2019 [74]. The pilot auction was to be held no later than October 2019, then it was postponed to April 2020, then to October 2021 [76] yet without success, and the new date is not yet known. For this purpose, annual quotas of support for particular types of renewable energy installations were to be determined. Given these implications and the need for significant investments, these auctions are obviously designed for large-capacity biogas installations, as the companies constructing them need to have access to large volumes of capital.

Another stimulating tool is also a premium on installations utilizing equipment produced domestically (Table 3). This premium is added on top of the feed-in tariff and depends on the share of domestic equipment used in the biogas project. At the same time, this premium is limited to 10% after six years of exploitation.


**Table 3.** Premiums for the use of domestic equipment in renewable energy generation projects.

Source: [75].

With the adoption of the Law of Ukraine "On the natural gas market" [77], biogas producers were granted the right to access gas transmission and distribution systems, gas storage facilities and LNG installations, as well as to connect to gas transmission and distribution systems, provided that technical and safety standards are met. The physical and technical characteristics of biogas should also meet the standards for natural gas.

In terms of electrical energy, according to the Law "On electricity market" [73], the taker (referred to in the legislation as the Guaranteed Buyer) is obligated to purchase electricity produced by households with installations of up to 50 kW capacity (the excess electricity above their monthly consumption volume), with the price set as the feed-in tariff. Similarly, the regional service provider is obligated to purchase electricity from producers (including energy cooperatives with a capacity of up to 150 kW) of all electricity supplied, reduced by the amount of electricity consumed for their operational needs. It is estimated that biogas installations typically consume ca. 5–8% of the generated electricity to ensure their operation. According to the Bioenergy Association of Ukraine [51], if biogas plants could sell 100% of the generated electricity to the grid, it would slightly increase the investment attractiveness of biogas production. Estimates were thus made to assess the simple return period of biogas installations with different capacities depending on the selected support scenarios and conditions: (1) at current feed-in tariff rate and without the purchase of electricity for the installation's operational needs; (2) at the current feed-in tariff rate and with the purchase of electricity for the installation's operational needs; (3) at a potential feed-in tariff rate of 0.3 EUR/kWh and with the purchase of electricity for the installation's operational needs (Figure 8).

**Figure 8.** Simple return period of different-capacity biogas installations depending on the support scenarios. Source: own calculations.

The assessment (Figure 8) shows that a simultaneous increase in the feed-in tariff from 0.1239 EUR/kWh to 0.3 EUR/kWh together with permission to buy electricity from the grid for energy needs of a biogas installation allow an acceptable return period (up to 5 years [78]) of for installations with a capacity starting at 150 kW. In order to achieve an adequate return period for smaller biogas installations (below 150 kW), it would be recommended to additionally compensate their investment (equipment) costs if renewable energy from this source is to be stimulated.

Despite the adoption of amendments to the Law of Ukraine "On heat supply" [79] providing a financial mechanism for non-natural-gas boilers (i.e., biogas in co-generation units), this mechanism has not provided a significant impetus for the development of biogas projects. It is advisable for agro-industrial enterprises in Ukraine to continue developing the generation of electricity and heat with the subsequent sale of heat to neighboring households, as the available feed-in tariff means this option of biogas utilization is most favorable in Ukraine's economic conditions. However, farms are usually located at a distance from heat consumers (other farms and households), so the option of selling heat is rather an exception. Biogas projects can be located in areas where significant agricultural waste is produced, so the heat generated can be used in part to heat the farm itself. The key limitation here is that demand for heat is seasonal (at best half of a year in given climatic conditions), so it is impractical to focus solely on heat generation.

According to Ukrainian legislation [80], disposal of animal waste must be carried out exclusively by specialist companies and can not be performed by companies producing animal products for human consumption. Manure and animal residues belong to the second class of waste and can either be burned or converted into organic fertilizer after mandatory sterilization under pressure or converted into biogas by pressure sterilization. Processing facilities for animal waste must be separate from companies producing foodstuffs. Class 2 waste can be used to make organic fertilizers and soil improvers that can be put on the market. Waste disposal companies are market operators. The law does not define the minimum and maximum size of such enterprises, which means that it also applies to small enterprises. Market operators are required to report their activities to the central veterinary authority on a monthly basis. They dispose of animal residues at their own expense or at the expense of state or local budgets that provide subsidies to businesses to partially compensate for the costs associated with the disposal and removal of animal by-products.

The procedure for using state funds to finance measures related to the disposal of animal by-products is approved by the Cabinet of Ministers of Ukraine. The State Budget of Ukraine for 2021 does not provide for such expenditure. Market operators who dispose of or remove by-products without pressure sterilization or without processing into biogas under pressure after sterilization can be fined. For legal entities, the fine is 23–30 minimum wages (in 2020, the minimum monthly wage in Ukraine equaled EUR 153); for private entrepreneurs, it is 8–15 minimum wages. For using unsealed containers for the transport of livestock waste by market operators, legal entities are subject to a fine of 8–12 minimum wages, and individual entrepreneurs are subject to a fine of 5–8 minimum wages. Sometimes companies prefer to pay a fine without further measures to dispose of livestock waste. However, large agribusinesses are subject to inspections by the Ministry of Health, the Prosecutor's Office, the Sanitary and Epidemiological Service and the Environmental Inspectorate of the Ministry of Ecology and Natural Resources. In some cases, biogas installations using Ukrainian equipment are therefore not economically feasible even to cover the additional costs of waste disposal. For example, for a pig farm with 12,000 head, which produces 20,000 tonnes of waste, the manure disposal costs reach ca. EUR 10,000 annually [81].

In Ukraine, there are sectoral budget support programs for agricultural producers, with additional preferences for farms. In particular, the small farms are supported, which may be a synergy with the feed-in tariff for renewable energy generation utilizing biogas installations (Table 4).


**Table 4.** State farm-support programs of additional assistance to potential biogas producers.


**Table 4.** *Cont.*

Source: compiled based on [83].

However, most of these programs are aimed at supporting agricultural production and could be treated as only supplementary support for the development of energy generation based on biogas. Moreover, the partial reimbursement of costs for the purchase of agricultural machinery of domestic origin includes a limited list of components for the generation of renewable energy (e.g., heat generators based on straw feedstock). At the same time, there should be dedicated state programs that would make it possible to take out a loan to finance biogas installations directly. It would also be advisable to extend the list of advisory services and include issues of renewable energy generation, as the lack of knowledge and advisory support to farms planning to engage and establish renewable energy installations is one of the key obstacles to their development.

In addition to government support, farmers and processors could benefit from a variety of sponsorships. In particular, the lending program through the Fund for Development of Entrepreneurship [84] was established jointly by the German state investment and development bank (KfW) [85], the Ukrainian government and the National Bank of Ukraine. Within this support, it is possible to apply for a loan of up to EUR 250,000 for five years to finance fixed assets of medium-sized enterprises (micro-crediting). Up to EUR 100,000 can be provided to enterprises, including for energy efficiency and energy saving, as well as job creation in depressed regions. The loan rate is calculated on the basis of the National Bank of Ukraine's discount rate plus 5%; the loan's timeframe is limited to six years [86]. Under the EU4Business program, it is possible to obtain a loan of up to EUR 5 million for up to ten years at a rate of 6–10% [87].

#### **5. Discussion**

By comparing the dynamics of energy generation based on biogas with the EU's experience, it can be stated that in the past three decades, Ukraine has shown relatively slow progress. In the EU, renewable energy generation based on biogas is developing at a much higher rate [88]. In 2018, 18,202 existing biogas plants had a total capacity of over 11 GW, producing 63,511 GWh of electricity [89]. In European countries, the main feedstock for biogas installations is crop residues and energy crops (almost half of the total feedstock) and livestock manure (ca. one-third) [11]. Germany is the European leader in the development of biogas energy, especially in terms of using the potential of agricultural feedstock. Thus, from 2014 to 2019, an annual average of 126 biogas installations were added, while the highest rate was from 2009 to 2011 (Figure 9). In addition, Germany is the European leader in the number of biomethane installations; as of 2018, the country had 195 units out of the total 540 units in the EU [90]. These installations are aimed at purifying biomethane and transferring it to the general distribution network.

**Figure 9.** Biogas installations in Germany within 1992–2019. Source: own compilation based on [28].

The dynamics of average annual biogas installation capacity in Germany show a rising trend (Figure 10). While by 2005, the average capacity of the new biogas installations was in the range of 150–200 kW, in 2005–2013, it increased to an average of ca. 0.5 MW, and after 2014, a tendency of large installations began, stabilizing around 2016.

**Figure 10.** Average annual new biogas capacity in Germany (in MW). Source: own compilation based on [28].

This development of biogas installations in Germany became possible not only due to the stimulation of renewable energy generation but also through the reduction in the attractiveness of fossil fuel. Thus, in the early 2000s, a tax on fossil fuels was imposed at 0.47–0.67 EUR/L of petroleum products and 0.015 EUR/kWh on electricity generated from other fossil fuels. There was a feed-in tariff of 0.0616–0.27 EUR/kWh, as well as 15–35% of additional subsidies for mini biogas installations [91]. As of 2017, the feed-in tariff for biogas from biowaste oscillated around 0.134–0.237 EUR/kWh, the feed-in tariff for biogas from organic fertilizers (manure) was at 0.2314 EUR/kWh for installations with a capacity of less than 75 kW. Feed-in tariffs are ranked overall depending on the size of biogas installation and the type of feedstock used; the energy producers are guaranteed the level of the feed-in tariff for ten years. In order to participate in the auctions, the installation capacity needs to be over 150 kW. If the auctions are won, state support is provided for up to 20 years [92]. By comparing Germany and Ukraine in terms of energy generation from biogas, it can be stated that Ukraine's biogas market is in a similar condition and development level to Germany's in the early 1990s. Maintaining such favorable policies for renewable energy generation in Germany has ensured the development not only of large biogas investment projects but also stimulated the appearance of numerous small and medium-sized installations, which is of considerable interest for Ukraine.

Most studies in Ukraine [34,41–43] stress the importance of biogas production development with a later generation of bioenergy, but they fail to take into account the investment issues depending on the size and availability of feedstock in small and medium-sized farms. What is more important, studies [32,33,44] that go deeper into the feed-in tariff analysis do not search for alternatives in order to propose more detailed approaches helping to create more beneficial conditions for various types of entities that might engage in biogas production. Thus there is a gap between theory and practice, as many researches do not differentiate between the above-mentioned dimensions, therefore failing to analyze the key predisposition—economic feasibility—to the full extent. The assessment presented in Section 4 makes it possible to understand these issues and shows that economic feasibility is missing from current state support conditions for all small and most medium-sized farms.

Obtained results go in line with the conclusions from [34] in terms of Ukrainian high potential for biogas generation, especially by farming households. The constant rise of natural gas prices emphasized upon in the aforementioned study support the necessity to tackle the issues hindering economic feasibility of energy generation from biogas by small and medium farms, as these entities would be the first to lose due to increased energy costs in case of further exploitation of fossil fuels. Another study [44] states that "a necessity to implement such projects is the introduction of an economically substantiated feed-in tariff for generation of energy based on biogas", as with the current levels of the tariff, such feasibility is not reachable for most potential producers. These statements were proven true by the estimations conducted in the current study, as the small and most medium farms would not be able to return the investments in the expected timeframe based on the existing feed-in tariff for biogas installations.

The current state program aimed at supporting biogas energy generation does not differentiate the feed-in tariff, due to which there is a sharp polarization in investment only large agricultural enterprises become involved in bioenergy based on biogas, and only 21 such installations have been established so far. Such a rate is not sufficient to make biogas energy a relevant renewable source, despite the existing agricultural potential defined in Sections 2 and 4.

Despite these implications, it is possible to seek solutions outside of solely the feed-in tariff. Farms whose feedstock production volumes do not allow profitable utilization of their biogas installations could potentially be merged into energy cooperatives based on the economic acceptability of feedstock transport costs. It is estimated that the economically feasible distance for the delivery of feedstock is up to 20 km for liquids and up to 50 km for solids [33]. Based on the previous administrative-territorial division [93,94], farms with biogas installations of up to 100 kW located in the same district as other farms could be united into cooperatives. While there are possible limitations, in many districts, the 20 km range criterion would be maintained, although this aspect would need to be studied further.

Additionally, the establishment of energy cooperatives allows the construction of energy facilities at the expense of local communities. Ukraine established its first municipal renewable energy cooperative, "Solar City" in Slavutych (Kyivska region), in February 2020, which is a 200-kWh-capacity solar power installation [95]. In Ukraine, the creation of energy cooperatives may be particularly appropriate in rural areas, as they are home to over a third of the population, while the costs and quality of energy services are not always satisfactory. There are examples of uniting nearby communities according to the principles of an energy cooperative when the community uses waste from the production/cultivation of basic agricultural products as energy feedstock (for example, the Yagidnyi Krai cooperative in the Ternopilska region) [96].

The definition of "energy cooperative" in Ukraine is established by the Law "On alternative energy sources" [97]. Further, in accordance with the provisions of the Law of Ukraine "On the electricity market" [73], energy cooperatives can sell their electricity either to the Guaranteed Buyer or to private households through the regional energy service provider. The creation of energy cooperatives is in line with a number of global trends, including distributed energy generation, the use of renewable energy sources and the concentration of energy production near places of direct consumption. The largest energy cooperatives are in the United States, Germany, Denmark, Sweden, the Netherlands and Austria [98–100]. As of 2015, there were 1000 cooperatives in Germany, which owned 47% of the renewable energy capacity [101].

Wider use of biogas requires changes in infrastructure, such as new roads for the supply of feedstock. Long-term contracts between suppliers of feedstock and enterprises that process it are necessary, which is especially relevant for small and medium-sized projects. Priority grid connection could be introduced for biogas projects, with the small installations (up to 500 kW) having these permits lifted. The construction of biogas pipelines is required to supply biomethane to the gas transportation systems. A Ukrainian corporation ("MHP Agro and Industrial Holding") has experience in building such biogas pipelines at ca. EUR 1 million per kilometer [102].

In the long run, it is possible to introduce the mandatory use of biogas by farms that produce the corresponding feedstock. This can be performed by introducing new national building standards for the construction of new agro-industrial companies whose activities are related to waste generation (farms, breweries) or the introduction of requirements for mandatory measures to reduce methane and carbon dioxide emissions. Legislation defining the need for sterilization of livestock waste under pressure should be repealed for biogas production, and existing fines for improper management of agricultural waste should be canceled.

Government loan guarantees would be beneficial. In order to enable the spread of biogas projects for small and medium-sized enterprises in Ukraine, interest rates on loans should be reduced through further cooperation of Ukrainian banks with international financial institutions such as the Global Environment Facility, the European Bank for Reconstruction and Development and the Clean Technology Fund.

There is poor dissemination of information and a lack of nationwide information campaigns on the use and construction of renewable energy sources in the agro-industrial complex. In our opinion, this barrier is no less important than financial barriers. Large agricultural corporations (referred to in Ukraine as agriholdings) already understand the benefits of using biogas and are launching large biogas projects. However, potential small and medium-sized producers need detailed information that not only provides information about the types of equipment but also about institutions providing financial support (state and private), as well as what would be the practical steps to construct a renewable energy installation and connect it to the energy grid or how to obtain the feed-in tariff for the energy. Changes should be made to requirements for obtaining state support, cutting bureaucracy and shortening the time lag between investments and actual support.

An important difference between small and large biogas projects (not to mention wind and solar energy) is access to development companies, which could be hired to prepare an investment feasibility study, change the land documentation to allow the placing of energy generation installations, obtain permits implementing the project, connect to the grid and start construction work [103]. Such functions are not widely available or affordable for small and medium-sized biogas projects, thus excluding them from investments in renewable energy generation. Detailed step-by-step information is needed to enable and speed up this process.

#### **6. Conclusions**

The study identified the economic feasibility of the development of renewable energy based on biogas projects in Ukraine, its key obstacles and legislation implications. Mediumsized and small farm capacities were focused upon as these types of farms in Ukraine are less economically viable. State support measures were analyzed to understand possible synergies between potential agricultural biogas projects and programs aimed at general or specific agricultural activities.

The analysis has shown there are relatively high initial investment costs, especially for small biogas installations. The smaller the installation, the higher the investment cost per unit of capacity. Loans and a special program for the implementation of small projects (up to 0.5 MW) are needed to aid small farms. This can be achieved in part through international financial institutions with energy efficiency and renewable energy generation programs, for example, by the International Finance Corporation or by the European Bank for Reconstruction and Development. The latter launched the EU4Business program in 2016 in cooperation with the European Commission, aimed at small- and mediumsized enterprises. It is also necessary to expand the Ukrainian state program to support farmers, including in terms of stimulating the purchase of certain types of machinery and equipment [104].

The feed-in tariff or the upper limit of the auction purchase price (currently the same as the feed-in tariff) is too low for biogas installations, which typically require high investment costs. The low feed-in tariff does not allow payback periods of biogas investment projects of less than seven years while, due to national currency volatility, inflation and the unstable political situation, bank institutions in Ukraine typically consider financing projects with a payback period of four to five years. In addition, it is advisable to differentiate feed-in tariff coefficients for biomass and biogas depending on the feedstock used so that the feed-in tariff coefficient or the upper limit of the auction price should be higher for biogas from agricultural waste than for biogas from by-products from alcoholic beverage production. In addition, the feed-in tariff or auction price should be differentiated depending on the installed capacity—the lower the capacity, the higher the tariff.

Currently, electricity from wind and solar energy installations is cheaper than that from biogas, while the feed-in tariffs in Ukraine for these sources of energy are higher. This is caused by significant differences in the costs of equipment, especially in the field of solar energy. It is likely that, with the introduction of liability for supply shortages, electricity from biogas would no longer be significantly more expensive, as upgrading meteorological stations to improve the quality of the forecast requires investment, and the question of who should invest in upgrading meteorological equipment in Ukraine has not been sufficiently considered. Moreover, wind and solar energy generation are dependent on seasonal and weather conditions, as well as daytime slots. At the same time, energy from agricultural biogas could be carried out either on a permanent basis or on-demand to cover gaps in the energy supply from more intermittent sources. Thus the lower feed-in tariffs for biogas are not well-grounded and do not take into account the importance and role of this source, yet this is a point for future research.

In conclusion, the state policy on biogas production and energy generation from agricultural sources is still fragmented and does not take into account the diversity of farms and their peculiarities, including the small and medium-sized ones. Within the existing legal framework, even after the launch of auctions, small farms have no real financial incentives to launch biogas projects. The current feed-in tariff is too low to provide reasonable payback periods. The marginal auction price is also too low. Small and mediumsized farms also need to prepare the investment projects on their own, as well as have limited access to financing. In order to overcome these problems, a specialist state biogas development program with government loan guarantees is needed, as well as advisory support and services to enable small and medium-sized farms to overcome the barriers of a lack of information. Such a complex approach could improve the conditions and make investments in bioenergy generation based on biogas more feasible, at least for a larger group of farms of various sizes.

Conclusions based on the studied Ukrainian experience could also serve as recommendations for other countries aiming to develop renewable energy generation. Financial (state or otherwise) support for diffusion of such innovations plays a crucial role, as its intensification is not possible if economic feasibility is not achieved and transfer to more "green" energy generation technologies are not incentivized, either in financial or organizational dimension. As for the latter, the experience of renewable energy development in Ukraine highlights the importance of institutional aspects, proving that transparency, consistency, stability and long-term predictability of state support and regulations are as crucial for the appropriate investment climate and transition to more environmentally-friendly energy generation solutions.

**Author Contributions:** Conceptualization, G.T., S.K. and V.K.; methodology, G.T. and S.K.; investigation, G.T., S.K., V.K., A.W. and R.P.; writing—original draft preparation, G.T., S.K., V.K. and A.W.; writing—review and editing, G.T., S.K., V.K., A.W. and R.P.; visualization, G.T., S.K. and V.K.; supervision, G.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


## *Article* **Water Needs of Willow (***Salix* **L.) in Western Poland**

**Daniel Liberacki 1,\*, Joanna Koci ˛ecka 1, Piotr Stachowski 1, Roman Rolbiecki 2, Stanisław Rolbiecki 2, Hicran A. Sadan 2, Anna Figas 3, Barbara Jagosz 4, Dorota Wichrowska 5, Wiesław Ptach 6, Piotr Prus 7, Ferenc Pal-Fam <sup>8</sup> and Ariel Łangowski <sup>2</sup>**


**Abstract:** Willows are one of the plants which can be used to produce biomass for energy purposes. Biomass production is classified as a renewable energy source. Increasing the share of renewable sources is one of the priority actions for European Union countries due to the need to reduce greenhouse gas emissions. To achieve the best possible growth of the willow and increase its biomass for fuel, it is crucial to provide optimal water conditions for its growth. The aim of the study was to determine the water requirements of willows under the conditions of the western Polish climate and to verify whether this area is potentially favourable for willow cultivation. The novelty of this paper lies in its multi-year climatic analysis in the context of willow water needs for the area of three voivodships: Lubusz, Lower Silesian, and West Pomeranian. This is one of the few willow water-needs analyses for this region which considers the potential for widespread willow cultivation and biomass production in western Poland. Reference evapotranspiration (ETo) was determined by the Blaney-Criddle equation and then, using plant coefficients, water needs for willow were determined. Calculations were carried out for the growing season lasting from 21 May to 31 October. The estimated water needs during the vegetation season amounted on average to 408 mm for the West Pomeranian Voivodeship, 405 mm for the Lubusz Voivodeship, and 402 mm for the Lower Silesian Voivodeship. The conducted analysis of variance (ANOVA) showed that these needs do not differ significantly between the voivodeships. Therefore, it can be concluded that the water requirements of willows in western Poland do not differ significantly, and the whole region shows similar water conditions for willow cultivation. Furthermore, it was found that water needs are increasing from decade to decade, making rational water management necessary. This is particularly important in countries with limited water resources, such as Poland. Correctly determining the water requirements of willow and applying them to the cultivation of this plant should increase the biomass obtained. With appropriate management, willow cultivation in Poland can provide an alternative energy source to coal.

**Citation:** Liberacki, D.; Koci ˛ecka, J.; Stachowski, P.; Rolbiecki, R.; Rolbiecki, S.; Sadan, H.A.; Figas, A.; Jagosz, B.; Wichrowska, D.; Ptach, W.; et al. Water Needs of Willow (*Salix* L.) in Western Poland. *Energies* **2022**, *15*, 484. https://doi.org/10.3390/ en15020484

Academic Editors: Vitaliy Krupin, Roman Podolets and Alban Kuriqi

Received: 1 December 2021 Accepted: 5 January 2022 Published: 11 January 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

**Keywords:** willow; *Salix* L.; water needs; biomass; evapotranspiration; energy crops; precipitation deficit

#### **1. Introduction**

One of the priority strategies of the European Union is "Climate Neutral by 2050". This document assumes reducing greenhouse gas emissions by the Member States and striving for climate neutrality (i.e., zero emissions). The implementation of this task focuses, among other things, on the use of alternative sources of energy to eliminate conventional fuels. This is particularly important in Poland, where most energy comes from burning fossil fuels. In 2019, the share of renewable energy in gross final energy consumption in this country was only 12.2% [1]. This is one of the lower results concerning the European Union countries. One of the ways to improve the current situation is to replace classical energy sources with biofuels created from biomass. Biomass can be obtained from energy crops. The energy plants cultivated in the conditions of Polish climate include poplar (*Populus* L.), Robinia acacia (*Robinia pseudoacacia* L.), Virginia fanpetals (*Sida hermaphrodita*), Jerusalem artichoke (*Helianthus tuberosus*), Giant miscanthus (*Miscanthus* × *giganteus*), and willows (*Salix* L.).

The willow is a plant that is easy to reproduce and overgrows. The willow comprises more than 300 species that occur as trees, shrubs, or dwarf shrubs. It has low soil requirements but broadly responds to habitat conditions, especially water conditions and organic and mineral fertilization [2]. *Salix* tolerates moist habitats, and its cultivation is not complicated. It usually occupies clay soils with poor permeability and difficult groundwater recharge [3]. Researchers highlight that the willow is a cleaner energy source than fossil fuels and one of the most promising biomass fuels [4]. According to Heinsoo [5], under moderate climate conditions, annual woody biomass production of *Salix* species can approach 20 Mg of woody dry matter per hectare. Once planted, it provides yields for about 25–30 years. Furthermore, it was estimated that the mean yield of dry willow biomass achieved in Poland is approx. 8.5 Mg ha−<sup>1</sup> y−<sup>1</sup> d.m. [6]. It was also found that 0.5 ha of willow (*Salix viminalis*) cultivation can supply any farm with fuel throughout the year [2]. In biomass production from willow for energy purposes, an important role is played by the density of plants per area unit. Research results conducted by different authors [7,8] indicate that the optimum plant density should be from 15,000 to 25,000 stem cuttings per ha and depend on habitat conditions and the willow variety. Based on the review of previous research, it was concluded that in Poland, the cultivation of new willow clones in the SRC system (short rotation coppice) on former agricultural land should be at a density of about 20,000 cuttings ha−<sup>1</sup> and harvested in three-year cycles [6]. Moreover, the willow has higher calorific values (19 MJ·kg−1) than other energy crops under the conditions of the Polish climate (Table 1). Although this value does not match the value of hard coal, which is 21 MJ·kg<sup>−</sup>1, the willow is nevertheless a viable alternative energy source for heating purposes [9]. Furthermore, when assessing the calorific value, the percentage of ash after biomass combustion is an important aspect. It has been estimated that this should not exceed 1.5 percent. This value for the willow is around 1.10 percent and thus meets the requirements. It should be noted that for other energy crops such as giant miscanthus or Jerusalem artichoke, this value is exceeded up to four times (Table 1).

**Table 1.** Energy crop parameters [9].


Willows have a high demand for nutrients, and adequate soil moisture promotes the tree's movement and uptake of these nutrients. One way of meeting willow requirements is to provide nutrients by fertilising with municipal sewage after pre-treatment. This is particularly applicable on land that does not directly include food or fodder crops [10]. It should be mentioned that willow stands significantly reduce nitrogen and phosphorus concentrations in wastewater. According to Börjesson [11], this value is even 75–90%. Using wastewater to irrigate willow crops can significantly increase yield and biomass. Furthermore, it also reduces the risk of groundwater pollution and eutrophication of surface waters through the trees' partial uptake of nitrogen and phosphorus. The use of willow as a natural filter for wastewater treatment is an excellent way to clean the environment while increasing biomass production without using additional costs associated with (e.g., fertilization). Another factor in preferring this type of management is the reduction of natural water resources under climate change conditions in favour of using water from municipal [12] or agricultural wastewater [13].

The main factor limiting the growth of energy crops, including the willow, is water availability. This is especially true in regions with temperate climatic conditions, where insufficient rainfall limits biomass growth even with high nitrogen fertilization [14]. In the period of the maximum increase of plant mass (from June to August), the willow reacts particularly to the course of weather conditions. Precipitation and moderately high temperature in this time have a positive effect on biomass yields, while drought may cause a decrease in yields even by 50% [15]. Plant water consumption depends mainly on the species, the yield obtained and the meteorological conditions, and the length of the growing season [16]. To quantify trees water use (including willow), methods such as Bowen ratio energy balance system, Eddy covariance, and plant water flow (SF) evaluation techniques are used. SF of willow shows diurnal and seasonal variability. Air temperature is the main factor controlling the seasonal variation of SF. The highest water use by willow occurs in May, June, July, August, and September [17]. The willow's groundwater use also depends on the soil's depth, the plant's root system structure, and the soil type. The willow has a deep and well-developed root system, allowing it to use shallow groundwater, unlike field crops usually supplied with water stored in the aeration zone [18]. The range of optimum groundwater table under different soil conditions for willow cultivation is wide and between 1 and 3 m. The increase in willow yields is mainly related to the enhancement of transpiration and the correct ratio between water and air in the soil [19]. The measured transpiration rates for willow are among the higher values compared to other cultivated trees. This is partly due to the fact that the willow is a highly hydrophilic plant that requires high transpiration for biomass production [20]. Despite willow's high water use efficiency (6.3 g dry biomass per kg transpired water), researchers note that water availability is a critical factor shaping willow short-rotation forestry [21]. Therefore, it is crucial to carry out research on willow water management and the possibilities of meeting its water needs.

This study aims to determine the water requirements of willow in western Poland. To check whether the water needs of willow are fulfilled in this region, an analysis of the course of climatic conditions and precipitation deficit values was carried out. The hypothesis that the water needs of willow differ between the three analyzed voivodships (Lubusz, Lower Silesian, and West Pomeranian) was considered in this study. Also, trends in changes in water needs were determined. Estimating water needs based on current climatic conditions is essential in appropriate crop management of this plant in this part of the country. This is one of the few studies on the water needs of willow cultivation in western Poland. The conducted research will be a valuable practical guideline for cultivating this plant for farmers and growers.

#### **2. Materials and Methods**

The assessment of water needs of willow (*Salix* L.) was carried out for three voivodships located in western Poland, namely the Lower Silesian, Lubusz, and West Pomeranian voivodships. Calculations were based on data obtained from meteorological stations located

in the largest cities of each province (i.e., for the Lower Silesian voivodship from Wrocław, for the Lubusz voivodship from Zielona Góra, and the West Pomeranian voivodship from Szczecin (Figure 1)).

**Figure 1.** The location of the analyzed voivodships and meteorological stations.

The analysis was carried out for the years from 1981 to 2010. The calculations were made for the growing season lasting in the studied area from the third decade of May (21 May) to the end of October. Based on meteorological data, the reference evapotranspiration (ETo) was determined. ETo is an agrometeorological parameter essential in irrigation planning and management [22]. ETo was calculated using the Blaney-Criddle (B-C) Formula (1) modified by Zakowicz [ ˙ 23] for the conditions of Poland. In this study, equation B-C was chosen to estimate ETo due to the limited availability of meteorological data (only monthly temperature values for the period from 1981 to 2010 are accessible). FAO Irrigation and Drainage Paper No. 24 'Crop water requirements' [24] suggests using the Blaney-Ciddle formula when only air temperature data are available [25]. The B-C formula is commonly used to estimate evapotranspiration with a limited number of available meteorological parameters. This is confirmed by several studies in various world areas [26–28].

$$\text{ETo} = \mathbf{n} \times \left[ \mathbf{p} \times (0.437 \times \mathbf{t} + 7.6) - 1.5 \right] \tag{1}$$

where:

ETo = reference evapotranspiration (mm);

n = number of days in the month;


Crop (potential) evapotranspiration was then estimated with equation (2). This method is widely used in scientific research [29–32]. Moreover, this equation is also used to calculate crop transpiration in the AquaCrop model developed by the Land and Water Division of FAO [33].

$$\text{ETp} = \text{ETo} \times \text{kc} \tag{2}$$

where:

ETp = crop (potential) evapotranspiration (mm);


**Figure 2.** Crop coefficient for the Blaney-Criddle equation for willow depending on the month [34].

The final calculation stage determined the precipitation deficit using Ostromecki's formula (3) [35,36]. The rainfall deficit determines the difference between the sum of evapotranspiration of plants and the sum of precipitation. Therefore, by estimating the precipitation deficit, it is possible to determine to what extent plants' water needs are met by precipitation, how much water is lacking, and what amount should be supplied to crops for adequate growth. Rainfall deficit assessments were made for the occurrence probability of the normal years (N50%), medium dry years (N25%), and very dry years (N10%).

$$\mathbf{Np}\% = \mathbf{Ap}\% \times \mathbf{ETp} \; \mathbf{ \neg BP}\% \times \mathbf{P} \tag{3}$$

where:

Np%= precipitation deficit at the probability occurrence p% (mm period<sup>−</sup>1);

ETp = average multi-year amount of evapotranspiration in the analyzed period (mm period<sup>−</sup>1);

P = multi-year average amount of precipitation in the analyzed period (mm period<sup>−</sup>1);

Ap% and Bp% = numerical factors characterizing the variability of evapotranspiration and precipitation for a given meteorological station.

The obtained results were statistically analyzed in R and Microsoft Excel environments. They aimed to determine the tendency of changes in the water needs of willow and significant differences in the results for individual voivodeships. ANOVA analysis of variance was used to find significant differences in water needs between the three voivodeships, preceded by Shapiro-Wilk tests and Bartlett's test for equality of variance. The analysis considered the following hypothesis:

**Hypothesis 1 (H1):** the water needs of willow do not differ between voivodships.

The linear correlation coefficient (r) method, widely used and proven in many studies, was used to determine the trend of changes in water needs.

#### **3. Results**

The results of willow ETp for individual growing seasons (third decade of May to the end of October) in the years from 1981 to 2010 were analyzed. The calculated values for each of the three provinces were compared to precipitation in the growing season. The analysis for the West Pomeranian voivodship showed that only in two years, 1996 and 2007, precipitation values (*P*) were higher than water needs (ETp). Therefore, it can be concluded that for this region, the course of climatic conditions in the studied period is unfavorable concerning the water needs of willow (Figure 3). The highest ETp values were estimated for 2006 and amounted to 442 mm. At the same time, the precipitation reached 253 mm. The lowest rainfall values were recorded in 1982–1983 and were about 162–174 mm. However, it should be noted that this was at the same time also in the period when the greatest differences between ETp and *P* occurred, amounting to 262 and 247 mm, respectively. Large differences were observed in 1992 (221 mm) and 1994 (209 mm). The standard deviation (SD) value for precipitation in the West Pomeranian province in 1981– 2010 was 75.1. For the same period, the SD of water needs reached 13.6. Other statistical characteristics are presented in Table 2.

**Figure 3.** Precipitation (*P*) and water needs (ETp) in the growing season (third decade of May— October) in 1981–2010 in the West Pomeranian voivodeship (SD of *P* = 75.1, SD of ETp = 13.6).

**Table 2.** Statistical characteristics of willow water needs (ETp) and precipitation during 1981–2010 for each province.


The situation was slightly better in Lubusz voivodship, where precipitation was greater than water needs in the growing seasons in the analyzed 5 out of 30 years (Figure 4). This group includes 1981, 1985, 1993, 1996, and 1998. The highest precipitation values occurred during the growing season in 1981 and amounted to 463 mm, while the lowest of 150 mm was recorded a year later (1982). The standard deviation of precipitation for the years analyzed reached 93. The difference in the driest year between *P* and ETp was 249 mm. However, it should be noted that this was not the highest value for the analyzed multi-year period. The greatest difference between precipitation and water needs in the West Pomeranian Voivodship was recorded in 1992, and it amounted to 278 mm. The maximum value of water needs was in 2006 and amounted to 444 mm. The standard deviation of the ETp in the analyzed years was 17.4 (Table 2).

**Figure 4.** Precipitation (*P*) and water needs (ETp) in the growing season (third decade of May— October) in 1981–2010 in the Lubusz voivodeship (SD of *P* = 93, SD of ETp = 17.4).

Among the analyzed regions, Lower Silesian voivodship had the highest number of vegetation seasons in which precipitation exceeded water needs. In this case, positive values were recorded in 6 out of 30 years, more precisely in 1981, 1986, 1995, 1997, 2001, and 2009 (Figure 5). The year 1981 was also in this region characterized by the lowest precipitation in the vegetation season, amounting to 179 mm. It was also the year when the difference between precipitation and ETp was the greatest and amounted to 233 mm. A relatively large difference (220 mm) was re-recorded in 1994. The highest precipitation values were reached in 1997 with 522 mm. For the 30 years analyzed, the SD of precipitation was 85.7, while for water needs, the SD was 12.6 (Table 2).

**Figure 5.** Precipitation (*P*) and water needs (ETp) in the growing season (third decade of May— October) in 1981–2010 in the Lower Silesian voivodeship (SD of *P* = 85.7, SD of ETp = 12.6).

Analyzing the climatic conditions during 30 years (1981–2010) in the growing seasons for the three provinces, it can be seen that in most years in all voivodships the ETp values were higher than *P*. Only in a few years the situation was reversed, and interestingly for each province, there were different years in most cases. Looking at the graphs (Figures 3–5), one can conclude that conditions were unfavorable for willow cultivation in most years. A potential solution to the problem of large differences between precipitation and ETp values for *Salix* cultivation could be the application of an adequate irrigation rate with treated

wastewater. Many scientific studies underline that willow is a plant for which this type of irrigation can benefit and contribute to plant development [10]. Wastewater irrigation could also be a favourable solution in the case of Poland due to the country's limited water resources.

As part of the analyses, mean values of monthly water needs were determined for each of the studied voivodships (Lower Silesian, Lubusz, and West Pomeranian) for the measurement periods in 1981–2010 (Figure 6). It was observed that the beginning of the growing season (3rd decade of May) is characterized by relatively low water needs resulting from lower temperature and limited evaporation. These values are 18 to 25 mm for the Lower Silesian and the West Pomeranian voivodships. In the case of Lubusz Voivodeship, the maximum value of water requirements in the third decade of May is 47 mm. Low values of water needs are also noted at the end of the growing season (October). Moreover, the highest water needs are observed in June, July, and August. They resulted from plant growth enhancement and increased evaporation.

**Figure 6.** Water requirements (ETp) in the growing season calculated for individual voivodeships in 1981–2010.

The highest values of standard deviation (SD) characterizing the variability of water demand also occurred in the summer months (i.e., June, July, August, and September (Table 3)). Even though the value of the average potential evapotranspiration of willow ETp for the three voivodeships was similar in the whole growing season and amounted to 402–408 mm, there were differences in the value of the SD index. Among the studied voivodeships, Lubusz had the highest monthly SD index values ranging from 3.0 to 9.3. In the two other voivodeships, the values were similar. The highest SD value was reached in July for Lubusz, and it was 9.3.


**Table 3.** Statistical characteristics of willow water needs in the period 1981–2010 determined as ETp [mm].

Voivodeship: WP, West Pomeranian; L, Lubusz; LS, Lower Silesian.

Based on meteorological data from 1981–2010 for each analyzed voivodship, the average water needs in the growing season (from the 3rd decade of May to the end of October) were calculated (Figure 7). For the Lubusz Voivodship, average water needs from 30 years were 405 mm, while the median was 407 mm. The maximum value was 444 mm, and the minimum was 377 mm. For the Lower Silesian province, the mean value for the growing season was 3 mm lower than for the Lubusz vhoivodship and amounted to 402 mm. The minimum value of water needs of this voivodship in the growing season was 378 mm and a maximum 429 mm. In West Pomeranian voivodship, the average value of water needs was the highest of all three studied voivodships and amounted to 408 mm. The range of values, in this case, was from 385 mm to 442 mm.

**Figure 7.** Average water requirements of willow for the analyzed voivodeships during the growing season (3rd decade of May to the end of October) calculated based on data from 1981 to 2010. (SD equaled 12.7, 17.4 and 13.6 for Lower Silesian, Lubusz and West Pomeranian, respectively).

The calculated Etp values for the growing season for each year in the years 1981–2010 in the studied three voivodeships were also subjected to statistical analyses in R to check whether there were significant differences between the provinces. First, for a data sequence for each voivodship, the hypothesis of normality of distribution was verified using the Shapiro-Wilk test. A significance level of α = 0.05 was assumed. The obtained results for the probability level (*p*-value) were greater than 0.05. Based on this (*p*-value > α), it was concluded that the assumption of normality of distribution is fulfilled (Table 4). Next, Bartlett's test for equality of variance was performed. Also, a significance level was taken as α = 0.05. A *p*-value of 0.1811 was obtained, greater than 0.05 (*p*-value > α). Therefore, it was concluded that at a significance level of α = 0.05, there are no grounds to reject the hypothesis stating the equality of variance of water needs in the growing season for the three provinces. Therefore, further analyses can be carried out.

**Table 4.** *P*-value obtained after Shapiro-Wilk test.


Another analysis performed in the R environment to determine whether there were significant differences between water needs in the individual voivodships was an ANOVA analysis of variance. It included hypothesis H0: the water needs of willow in the analysed provinces do not differ. The significance level was taken as α = 0.05. The ANOVA analysis resulted in a *p*-value of 0.33 (i.e., greater than 0.05 (*p*-value > α)). Therefore, it was concluded that at a significance level of α = 0.05, there were no grounds to reject the H0 hypothesis. Thus, the values of water requirements in 1981–2010 calculated for the growing season for the three voivodships do not differ statistically significantly. As there was no basis for rejecting the H0 hypothesis, no further multiple tests were conducted to test the significance of the differences. Post-hoc tests were not performed since, based on ANOVA analysis, they would not show differences between water needs in the analyzed provinces. Therefore, it can be concluded that the whole area of western Poland is characterized by similar water needs in the case of willow.

Analyzing the obtained values of water needs in the studied period compared to precipitation for Lubusz, West Pomeranian, and Lower Silesian voivodships, it can be noticed that water requirements in western Poland are not fulfilled. The precipitation values were lower than the needs in all three voivodships (Figure 8). The most remarkable difference is visible in West Pomeranian voivodship, where the average amount of rainfall in the growing season is 365 mm, and the calculated water needs are 408 mm. In Lubusz and Lower Silesian voivodeships, this difference was lower and ranged from 18–24 mm, almost half as much as in West Pomeranian voivodeships. The standard deviation values for the data are shown in Table 2.

**Figure 8.** Water needs of willow and average precipitation during the growing season for individual provinces in 1981–2010.

The estimated water requirements of willow in individual decades (1981–1990, 1991–2000, and 2001–2010) of the 1981–2010 period showed an increasing trend (Figure 9). In Lubusz province in 1981–1990, the water needs were 394 mm and in 2001–2010 as much as 416 mm. Thus, the needs in this province increased by 22 mm. It was the highest increase in comparison to all three analyzed voivodeships. In Lower Silesian, this increase was 16 mm, and in West Pomeranian 14 mm. In the first analyzed decade of 1981–1990, the highest water requirements for willow were in the West Pomeranian voivodship. They amounted to 403 mm, while the lowest (394 mm) were in the Lubusz voivodship. On the other hand, the Lower Silesian province's lowest value in 2001–2010 of 411 mm. Analysing standard deviation (SD), the highest values in all three regions were recorded for data from the decade 1991–2000. The greatest SD was for Lubusz province and reached 20.53. The lowest SD was estimated for data from 2001 to 2010 in Lower Silesian and earned 8.51 (Table 5).

**Figure 9.** Average water needs of willow in each decade (10-year periods) from 1981 to 2010 for the analyzed voivodeships.


**Table 5.** Values of standard deviation (SD) for decadal data for each voivodship.

#### **4. Discussion**

The impact of water resources on crops is particularly important in Poland, as Polish water resources are relatively small compared to other European countries. The average total precipitation is about 630 mm (i.e., 196 km<sup>3</sup> per year) [37]. Additionally, water resources in Poland are characterized by high spatial and temporal variability. The recommended way of rational management of limited water resources is retention. It consists in storing water when there is an excess and giving it back to users and the environment in times of shortage. Climate change scenarios indicate that we will increasingly be dealing with extreme weather events that will cause droughts or floods, and therefore appropriate water management is extremely important.

The assessment of climatic water balance for western Poland in the six-month growing season (April-September) indicates the occurrence of large negative differences between precipitation and evapotranspiration values. The increasing likelihood of heatwaves in summer may result in short- or long-lasting droughts that significantly impact crops [38]. Also, in this study on willow, large differences between precipitation values and potential evapotranspiration are noticeable (Figures 3–5). It is predicted that the values of the P-E index will change unfavorably in the future, leading to more frequent and more severe summer water stress. Therefore, western and central Poland areas require the necessary protection of agriculture against the negative effects of water shortage during the growing season [39]. Moreover, studies conducted in this paper indicate that plants' water needs will also increase. The determined time trend of the variability of water needs and the linear correlation coefficient (r) showed that in all of the three studied voivodeships, there was a significant tendency for the water needs of willow to increase during the growing season (Table 6). Significant differences were also observed in the summer months (June, July) for Lubusz province. In the Lower Silesian voivodeship, significant differences were also observed in August besides these two months. However, at the same time, no differences were noticed in West Pomeranian.

**Table 6.** Water needs (mm) of willow in the years between 1981 and 2010 in the provinces of western Poland.


\*\*\*—significant at *p* = 0.01; \*\*—significant at *p* = 0.05; \*— significant at *p* = 0.1; n.s.—not significant (r = 0.46398, r = 0.362 and r = 0.30692 for *p* = 0.01, *p* = 0.05, and *p* = 0.1, respectively (i.e., for probability 99%, 95%, and 90% accordingly)).

Analyzing the trend of changes in water needs in the thirty years 1981–2010, it can be observed that for the whole growing season in Lubusz, West Pomeranian, and Lower Silesian voivodeships, the trend is positive (Table 4). The highest is in Lubusz, and it is 9.4 mm-decade−1. The values are similar in the following two provinces, and they are 6.7 mm·decade−<sup>1</sup> for Lower Silesian and 5.0 mm·decade−<sup>1</sup> for West Pomeranian. Analyzing monthly data, the highest increasing tendency of water needs of willow was 4.6 mm·decade−<sup>1</sup> in July. On the other hand, slight negative tendencies for all voivodeships were observed in October (Figure 10).

Poland's western and central areas require necessary protection of agriculture against the adverse effects of water shortage during the growing season. The water deficit is evident on light soils with low water retention capacity. Security of crop production against drought is ensured by irrigation. Therefore, irrigation becomes an indispensable element of cultivation in large parts of the country, especially where the climatic water balance is negative (e.g., Wielkopolska, Kujawy), and the soils are characterized by low water retention [39]. The problem of water scarcity is also analyzed in this publication in the context of willow plantations. The precipitation deficits for three voivodeships in the growing season determined by Ostrom ˛ecki's method [35] are presented in Figure 11. The results of the calculations were shown for three categories of years: very dry years (once per ten years, N10%), medium dry (once per four years, N25%), and normal years (once per two years, N50%). The highest rainfall deficits occurred in the West Pomeranian Province in the very dry year and amounted to 286 mm. Among the three analyzed voivodships, in West Pomeranian voivodship, the deficits were also the highest in average dry years

(222 mm) and normal years (132 mm). Moreover, the lowest precipitation deficits in the studied period were recorded in Lower Silesian Province. They amounted to 263 mm for very dry years, 193 mm for medium dry years, and 99 mm for normal years.

**Figure 10.** The trend of water needs of willow in each month for the analyzed voivodships.

**Figure 11.** Rainfall deficit for willow cultivation in the analyzed provinces in 1981–2010.

The results confirm a problem of precipitation shortage in western Poland. In combination with its low water resources, it creates a particular threat to agriculture and the production of productive crops. Researchers emphasize that the decision on the location of energy crops with a high share in the catchment should take into account the water needs of energy crops, as their cultivation can significantly affect water balance parameters [40]. The analyses carried out on water need help to determine the potential of a region for willow cultivation. Published scientific articles note the potential of relatively large areas of marginal land and fallow grounds in Poland as suitable sites for willow growth. It should be noted that fallow grounds constitute as much as 10% of shares of arable lands [41]. Research carried out by scientists shows that in the management of fallow and uncultivated land in Poland for willow weed cultivation, the amount of energy obtained would be 3083 TJ. Moreover, it was shown that one of the voivodeships with the largest potential energy resource is the Lower Silesian voivodeship analyzed in this paper (with a volume of 386 TJ) [42]. Subsequent estimations carried out assuming willow cultivation on the

total fallow area in Poland in 2014 showed that the energy value of willow wood dry mass would be 138,285,528 GJ·yr−1. Moreover, the dry wood mass for the whole country would be 7,128,120 t·yr−1. The ecological effects of obtaining energy willow biomass for heating purposes were also estimated in these analyses. It was found that as a result of this practice, nitrogen oxide emissions could potentially be reduced in Poland by 26,274 tons per year, carbon dioxide emissions by 13,828,553 tons and sulphur dioxide emissions by about 103,714 tons per year [43]. Therefore, it can be concluded that growing willow on fallow land and harvesting it for use would be a potentially positive measure in the face of climate change and the need to reduce greenhouse gases. Moreover, it would allow meeting the objectives of the European Union policy on greenhouse gas reduction.

Moreover, studies conducted in Poland on willow cultivation in a short rotation woody crops (SRWC) system (of three- to four-year rotation) and Eko-Salix systems (five-year rotation) have shown that the energy gain obtained is even 20 times higher than the inputs needed to run the plantation and harvest the willow biomass [44]. Therefore, this shows that willow cultivation benefits the climate, environment, and economic context. All of these studies support Poland's high potential for this type of cultivation. As Jadczyszyn et al. [45] estimated, the potential area of willow cultivation for energy purposes in Poland amounts to 9541 km2 or 4.6% of agricultural land. However, this analysis did not cover soils with the highest production potential belonging to the wheat and very good rye complexes and the weakest, too dry soils of the very weak rye complex. It also excluded mountain areas, protected areas and areas with annual precipitation <550 mm. For the West Pomeranian voivodship, the estimated potential area for willow cultivation amounted to 1094 km<sup>2</sup> (6.5% of agricultural land), for the Lubusz voivodship 534 km2 (6.5% of agricultural land) and the Lower Silesian voivodship 883 km2 (6.8% of agricultural land) [45]. Thus, it can be concluded that these provinces not only do not differ concerning the water needs of willow (as shown in this paper) but also the potential area under willow cultivation is similar for the percentage of agricultural land in the given voivodship (it is about 6.5–6.8% of the agricultural land of the voivodship). The research carried out in this study has shown that in the area of the three voivodships of western Poland, there are no significant differences in the water needs of willow estimated for the growing season between 1981 and 2010. Lack of significant differences in the obtained ETp values results most probably from the course of air temperatures in the analyzed period in the voivodships. The used Blaney-Criddle formula is based on air temperature, and hence the data strongly affect the obtained results. However, it should be noted that the use of the B-C formula in this study captured an extremely important trend, namely the increase of water needs of willow. This is due to the fact that the predicted climatic changes under Polish conditions include an increase in air temperature, which affects the growth of plants' water needs.

The water requirements of willow estimated in the paper showed the current unfavorable state of conditions for the cultivation of this plant in western Poland. To obtain the largest possible biomass for energy purposes, providing the willow plant with optimal water conditions is crucial. World research papers have increasingly focused on water management in crops and estimated the necessary amount of water required for adequate irrigation. It is also essential to carry out studies considering the impact of climate change on plants' water needs [46]. Increasingly, research work is being conducted to model crop water requirements and the necessary amount of irrigation water under different climate change scenarios [30,47]. Previous analyses show that climate change has an impact on irrigation water requirements. Furthermore, irrigation demand will increase for many crops due to climate change [48].

Worldwide research indicates the need for precise estimation of plant water requirements. When making such calculations, it is crucial to use appropriate kc coefficients. Measurements conducted for Peach-leaf willow (*Salix amygdaloides*) in the Platte River basin in central Nebraska, USA, contributed to the development of crop evapotranspiration coefficient (KcET) curves for this cultivar [49]. However, it should be remembered that the water needs of willow depend on climatic conditions. In a study conducted on *Salix*

*gooddingii* grown in restoration plots in three irrigation districts on the Lower Colorado River, reference crop evapotranspiration (ETo) values ranged from 1890 to 1969 mm·yr−1. For the same sites, irrigation requirement was estimated from 1817 to 1962 mm·yr−<sup>1</sup> [50]. Evapotranspiration (ET) values were also evaluated for wetlands and the willow variety *Salix miyabeana*. From May to October, the average evapotranspiration rate in eastern Canada was 22.7 mm·day−<sup>1</sup> [51]. Therefore, it can be concluded that the estimation of ETp for willow in this study is fundamental in the context of its proper cultivation, and these analyses fit into the trend of global research. Moreover, this study fills a gap in science concerning the determination of the water needs of this plant for the conditions of western Poland. This is one of the few studies on this subject for this region.

Scientists emphasize that the willow is not a demanding plant in cultivation conditions. Furthermore, it has been noted that willow also shows salt tolerance, which has been defined as sensitive to moderately tolerant [52]. Moreover, it has been demonstrated that irrigation of willow with stormwater up to 1625 mg Cl had no short-term effect on biomass accumulation and evapotranspiration [53]. All of these measurements indicate that willow has a high tolerance to different growing conditions. However, it should be remembered that it is a plant that needs an adequate amount of water for optimal growth. Soil water availability is one of the determinants of willow growth in montane riparian communities in the USA [54]. High available water content (AWC) values were also the most critical determinant of willow yield in the Danish area. AWC had a much greater effect on yield than precipitation, radiation sum, and region [55]. The Swedish researchers found that water is critical for the excellent profitability of willow short-rotation forestry [56]. In addition, studies have shown that the Carolina Willow (*Salix caroliniana*) seeds in saturated soils kept moist by capillarity had the highest germination capacity [57]. The research also included estimating factors affecting aboveground biomass allocation and water storage ratio in alpine willow shrubs. It was observed that relative water storage allocation was significantly affected by species types [58].

The analyses carried out in this paper have shown that water needs of willow in Poland have an increasing tendency year by year. Due to the ongoing climatic changes, the occurrence of drought periods, and thus precipitation deficits, it will be more and more challenging to fulfill them. It may not be possible to supply the appropriate amount of rainwater necessary for irrigation during drought periods. However, it should be remembered that willow is a plant that can also be successfully irrigated with wastewater. Worldwide research shows that using willow for energy production is an opportunity to reduce greenhouse gas emissions. It has been found that the biomass of this plant can be a carbon negative or low-carbon energy source with high emissions and energy return on investment. This applies to regions with similar conditions for the plant's growth, transport distances, and infrastructure [59]. Therefore, it is crucial to continue research into willow cultivation to optimize its cultivation and widespread use. Research should include field experiments on different willow cultivation practices and varying water availability. In view of climate change and the need for crop adaptation, all kinds of experiments simulating stress conditions such as drought are desirable. Increasing research and knowledge is extremely important, especially in countries such as Poland, which soon must change their energy policy and drastically reduce coal burning in favour of other alternative energy sources, including biomass.

#### **5. Conclusions**

The calculations and analyses carried out in this paper determined the water needs of willow and evaluated the current conditions of its cultivation in three voivodships of western Poland: West Pomeranian, Lubusz, and Lower Silesian. The main conclusions of the study are as follows:

1. Estimated water needs for the years between 1981 and 2010 in the growing season (from 3rd decade of May to the end of October) amount on average to 408 mm for West Pomeranian Voivodeship, 405 mm for Lubusz Voivodeship, and 402 mm for Lower Silesian Voivodeship. The highest values of water needs can be found in June, July, and August, while the lowest can be found in the third decade of May and October.


The analyses carried out show that similar conditions for willow cultivation characterize West Poland, and its water needs mainly were not fulfilled by precipitation in the period from 1981 to 2010. Based on previous worldwide studies, one should consider trying to apply adequate irrigation with water or irrigation with treated wastewater, which would provide an appropriate amount of water to this plant. At the same time, this measure could contribute to obtaining an adequate or even higher yield. The use of wastewater in Poland for this purpose would also be potentially beneficial due to the relatively small water resources. However, more research should be conducted in Poland to verify this hypothesis. Nevertheless, without estimating the water requirements, it is not possible to use adequate irrigation and carry out further experiments correctly. Therefore, this study provides guidance and encouragement for further research and valuable practical advice for farmers and growers.

Currently, scientists emphasize that due to Poland's limited water resources, the selection of a suitable energy crops should be based on the water needs of the plants [40], which were estimated in this paper for the willow. This research project is one of the few attempts to estimate willow ETp for the climate of western Poland. With the accurate estimation of the water needs of the willow, it will be possible to optimize the cultivation of this plant and thus increase the biomass obtained. With increased biomass, this plant could potentially be a source of renewable energy for Poland, thus speeding up the country's transition away from coal mining. Such an action fits into the climate neutrality policy of the European Union, which is currently one of the priorities to be implemented by member states.

**Author Contributions:** Conceptualization, R.R., S.R., B.J., W.P. and P.P.; methodology, S.R., R.R., P.P., F.P.-F., H.A.S., J.K., A.F., W.P. and D.W.; validation, A.F., D.W., R.R., P.P., S.R., P.S. and H.A.S.; formal analysis, S.R., J.K., R.R. and B.J.; investigation, R.R., S.R., B.J., W.P., D.L., P.S., F.P.-F. and A.Ł.; writing—original draft preparation, J.K., D.L., P.S., R.R. and S.R.; writing—review and editing, J.K., D.L., P.S., R.R. and S.R; visualization, J.K. supervision, R.R., S.R. and D.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data sharing not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


**Dumitru Peni 1,\*, Marcin D ˛ebowski <sup>2</sup> and Mariusz Jerzy Stolarski <sup>1</sup>**


**\*** Correspondence: dumitru.peni@uwm.edu.pl

**Abstract:** Biogas production is one of the solutions for replacing fossil fuels, which promotes the widespread use of green energy. The aim of this study was to determine the potential of *Silphium perfoliatum* as an energy crop for biogas production, as well as the effect of different fertilization doses (0, 85 and 170 kg N ha−1) on the production potential (NL CH4 kg−<sup>1</sup> VS) of *Silphium perfoliatum*. The study investigated the use of different feedstocks, such as raw and ensiled *Silphium perfoliatum* biomass. The methane production ranged between 193.59 and 243.61 NL CH4 kg−<sup>1</sup> VS. The highest biogas production potential was achieved with the biomasses which were cultivated with the highest fertilization dose (170 kg N ha−1), both for raw and ensiled crop biomasses, although the difference from the other fertilization doses was not significant. The feedstock (biomass and silage) and digestate parameters were investigated as well. The use of *Silphium perfoliatum* for biogas production seems very promising since its methane production potential was found to be similar to that of the most common energy crop, such as maize, indicating that *Silphium perfoliatum* can compete in the future with maize.

**Keywords:** anaerobic digestion; fertilization; *Silphium perfoliatum*; biogas; biomass characteristics; digestate

#### **1. Introduction**

In the last few decades of the 20th century, fossil fuels were the most important source of energy used worldwide, having a huge impact on the technological and economic development of many countries [1]. However, their widespread use has had detrimental consequences for the environment by increasing the level of CO2 released into the atmosphere, which highly contributes to global warming and climate change [2,3]. Now, fossil fuels are continuing to be used widely in energy production. But facing the depletion of fossil fuels and their constantly rising prices, new and considerably less polluting renewable energy sources are needed [4]. Although European countries have set out to reach a certain percentage/target of renewable energy share to reach by 2020 [5], some of them, including Poland, have not been able to achieve the proposed target. Therefore, it is very important to investigate and implement the use of renewable energy sources on a large scale.

Anaerobic digestion is a biological process that converts biomass into energy/methane [6]. Digestate is the main anaerobic digestion byproduct from which methane has been obtained that can be used as a substitute for mineral fertilizers [7,8]. Nowadays, this process is used to convert biomass to obtain methane as a source of green renewable energy. The production and use of biogas contribute in many aspects to economic, environmental, and social factors [9–11]. Biogas can be obtained from a manifold of substrates. All that is needed is a biomass that contains carbon, carbohydrates, proteins, fats, cellulose and hemicellulose. Currently, biogas is produced from various types of biomass, such as residues from fruits and vegetables, slurry, maize, silage, manure, agricultural and industrial wastes, municipal organic wastes, sewages and sludges [12]. Poland is one of the most important biomass

**Citation:** Peni, D.; D ˛ebowski, M.; Stolarski, M.J. Influence of the Fertilization Method on the *Silphium perfoliatum* Biomass Composition and Methane Fermentation Efficiency. *Energies* **2022**, *15*, 927. https:// doi.org/10.3390/en15030927

Academic Editors: Vitaliy Krupin and Roman Podolets

Received: 11 January 2022 Accepted: 26 January 2022 Published: 27 January 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

exporters in Europe [13,14] and at the national level, the biomass represents the highest raw material (79%) to obtain energy from renewable energy sources (RES) [15] and could influence the EU market towards bio-based economy [16]. At the end of 2019, there were 103 biogas agricultural plants in Poland [17], while for example, Germany has more than 9000 [6]. The most popular agricultural feedstocks for biogas production in Poland in the last year were distillery stillage (20.6%), residues from fruits and vegetables (19.4%), slurry (18.5%). Maize silage (10.6%) is widely used as well [17]. Mono–digestion of, for example, manure releases low methane yields, and hence co-digestion with energy crops is more preferable [18], and mixing substrates can also have positive effects [19].

Some recent studies [20,21] describe a possible and promising use of *Silphium perfoliatum* for biogas production after an anaerobic digestion process [22]. In this context, it is highly possible that the use of *Silphium perfoliatum* for co-digestion could improve and contribute to the higher yield of methane. *Silphium perfoliatum* belongs to the sunflower family *Asteraceae*. It is used and investigated for its properties as feed [23–27], as well as for its content of active compounds which are used for pharmaceutical and cosmetic purposes [28–30]. *Silphium perfoliatum* is a species that in the future may provide a source of renewable energy [10,20]. *Silphium perfoliatum* plantations can be exploited for a period of over 20 years with one or two harvests during the growing/vegetation season. It contributes to the improvement of the soil quality due to the reduced agricultural operations, as well as being beneficial to biodiversity [31–33]. It is less competitive with food and feed, compared with the most common agricultural crop used for biogas production, i.e., maize [33,34]. Its productivity of biogas is currently investigated [31–33] as the plant is considered a promising energy crop that could replace maize [35] in regions where lands are highly affected by intensive agriculture, as well as on marginal soils that are not suitable for the cultivation of other agricultural crops [36]. Another product following the production of biogas is digestate, which—depending on its characteristics and origin—can be used as a bio-fertilizer or for the production of solid biofuel [37,38].

Therefore, the novel perennial energy crop *Silphium perfoliatum*, which is more often proposed as an alternative crop for biogas production, has been investigated in the present study to gain new knowledge regarding its suitability as a biogas substrate in order to expand its use to a much wider scale. Particular attention was paid to its use as raw material or as silage, as well as the influence of fertilization on biogas and methane production. Withal, the digestate after the end of biogas fermentation was investigated to allow for a more comprehensive evaluation of its properties. The aim of this research was to investigate the potential of biogas production from *Silphium perfoliatum* as raw biomass, and silage as a feedstock for agricultural biogas plants depending on the form (organic and mineral) and doses of fertilization applied, as well as the characteristics of the digestate.

#### **2. Materials and Methods**

#### *2.1. Organization of Experimental Works*

The research was composed of two different experimental stages focused on the type of feedstock: raw biomass *Silphium perfoliatum* (stage 1) and silage of *Silphium perfoliatum* (stage 2), and three experimental series, analyzing the form of fertilization (organic, mineral and control without fertilizer). In each series, there were three variants, i.e., doses of fertilization (0, 85 and 170 kg ha−<sup>1</sup> N) used every year after the onset of vegetative growth. The research design is presented in Table 1.

#### *2.2. Feedstock Origin*

The substrate used in the present study was raw and ensiled *Silphium perfoliatum*. The biomass collected was green forage from whole plants. The field experiment was conducted on land owned by the Research Station of the University of Warmia and Mazury in Olsztyn (UWM) in the village of Ł ˛ezany (Poland). Plants of ˙ *Silphium perfoliatum* were harvested at the maturity stage in the third and fourth years of growth. They were cut with a rotary mower in the first ten days of September 2019 and 2020. Chopping was performed with a device for cutting and grinding (Viking Ge220).

**Table 1.** The research design.


(A) RO85—raw biomass with organic fertilizer 85 kg ha−<sup>1</sup> N; (B) RO170—raw biomass with organic fertilizer 170 kg ha−<sup>1</sup> N; (C) RM85—raw biomass with mineral fertilizer 85 kg ha−<sup>1</sup> N; (D) RM170—raw biomass with mineral fertilizer 170 kg ha−<sup>1</sup> N; (E) RC0—raw biomass without fertilization; (A) SO85—silage with organic fertilizer 85 kg ha−<sup>1</sup> N; (B) SO170—silage with organic fertilizer 170 kg ha−<sup>1</sup> N; (C) SM85—silage with mineral fertilizer 85 kg ha−<sup>1</sup> N; (D) SM170—silage with mineral fertilizer 170 kg ha−<sup>1</sup> N; (E) SC0—silage without fertilization.

Anaerobic sludge, which served as the inoculum for the fermentation process in bioreactors, came from a closed bioreactor with a capacity of 7300 m3 operated at 36 ◦C. The characteristics of anaerobic sludge are provided in Table 2.

**Table 2.** Characteristics of anaerobic sludge used as the inoculum for the fermentation process in bioreactors.


DM—dry mass (% d.m.); ODM—organic dry mass (% d.m.); Ash (% d.m.); Carbon (% d.m.); Nitrogen (% d.m.); C/N—carbon to nitrogen ratio.

#### *2.3. Silage Preparation*

Silage investigated in the present study was preserved by ensiling *Silphium perfoliatum* in 1000 mL plastic silos on the day of harvesting, immediately after chopping. Ensiling began by filling in every silo manually by compaction. All silos were filled completely and subsequently sealed, obtaining an average density of 867 kg m−3. The silos were stored at a temperature of 10–15 ◦C, for a period of 7 months before starting the measurements. Moreover, fresh silage samples were dried at 105 ◦C for 24 h and then crushed in a fiber mill (Retsch SM 200, Retsch GmbH, Haan, Germany) to a particle size of 1 mm for chemical analyzes. Silage was prepared in triplicate, without silage additives or preservatives.

#### *2.4. Anaerobic Digestion Test*

The biogas generation from raw material and silage was carried out for 25 days under mesophilic conditions (37 ◦C) in Automatic Methane Potential Test System II (AMPTS II) reactors coupled with a system recording changes in partial pressure. The amount of methane produced in AMPTS II was measured every three hours throughout the process. Tests were performed on a laboratory scale in 500 cm3 reactors (glass vessels) filled with approximately 190 g of the inoculum and then assumed amounts of substrate were added (depending on the content of organic matter). Moreover, 200 g of inoculum substrate-free was used as a negative control sample. In the technological repetitions, the initial load varied between 4.5 and 5.5 g VS/L, respectively. Was recalculated amounts of substrate. Anaerobic conditions were achieved by removing oxygen from the reactors (the feedstock and gas phase of the reactors), which was purged with compressed nitrogen. Reactors were equipped with automated stirrers (mixing the content at 100 rpm for 30 s every 10 min), a stabilizing system, and temperature control. The pressure (biomethane production) report was automatically recorded daily, in already normalized data (1.0 standard atmospheric pressure, 0 ◦C and zero moisture content), using the bioprocess control software. The composition of biogas was measured at the end of the process using a 10 mL injection volume syringe probing into the gas chromatograph connected to a thermal conductivity detector (TCD) (GC Agilent 7890 A–Agilent Technologies, Santa Clara, CA, USA). Helium (He) and argon (Ar) were used as the carrier gases at a flow of 15 mL/min. The temperatures of the injection and detector ports were 150 ◦C and 250 ◦C, respectively. Methane yields were calculated as the methane volume produced over a period of 25 days. The perfect gas equation was the basis for computing the volume of produced methane. The endogenous production of the anaerobic sludge was excluded from the calculations of methane production of the tests.

#### *2.5. Analytical Methods*

At the beginning of the trials, substrates (raw and silage), inoculum and digestate were analyzed for dry matter content, organic dry matter content, ash content, carbon content and total nitrogen. For the substrates, inoculum and digestate samples, moisture, dry matter content and organic dry matter were determined with the gravimetric method by drying in an oven at 105 ◦C for 24 h (EN ISO 18134–1:2015 using the FD series laboratory dryer (FD BINDER series, Tuttlingen, Germany)). Ash content was determined using an automatic ELTRA TGA–THERMOSTEP analyzer (ELTRA GmbH, Neuss, Germany) according to the PN–EN ISO 18122:2016–01. The carbon content was determined using an automatic ELTRA CHS–500 analyzer (ELTRA GmbH, Neuss, Germany) PN–EN ISO 16948:2015–07. The total nitrogen was determined by the Kjeldahl method with the use of a K–435 mineralizer and B–324 BUCHI distiller (Büchi Labortechnik AG, Flawil, Switzerland).

#### *2.6. Statistical Analysis*

All experimental variants were conducted in triplicate. Statistical analysis of the results was supported by a Statistical 13.3 PL package. Thus, the reaction rate constants (k) based on experimental data were determined by non-linear regression. The rate of biogas production (r) could be determined for each experimental variant. The iterative method was applied, in which the function is replaced in each iterative step with a linear differential in relation to the determined parameters. The coefficient of convergence ϕ2 was adopted as the measure of the curve's fit (with determined parameters) to experimental data. This coefficient is the ratio of the sum square of deviations of experimental values to the sum square of deviations of experimental values from the mean value. A three-way analysis of variance (ANOVA) was carried out to determine the significance of differences between the variables. To determine the significance of differences between the analyzed variables, Tukey's HSD test was used. In all tests, differences were considered significant at *p* < 0.05. The Pearson correlation coefficient between the analyzed trials was also determined.

#### **3. Results and Discussion**

#### *3.1. Biomass Characteristics*

The characteristics of the *Silphium perfoliatum* (raw biomass and silage) used in the study are presented in Table 3. The DM had values between 22.5–25.3% for raw material and 20.6–21.8% for silage. In the studied biomass, the ODM had values between 90.3–92.0% for raw material and 89.5–91.9% for silage. The analysis showed that the substrate type (raw biomass and silage) influenced the ODM, ash content, C, N content and the C/N ratio (Table 4). In turn, the fertilization type significantly influenced ODM, ash content, dry matter content, N content and C/N ratio. On the other hand, the fertilization dose had a significant effect only on the N content and C/N ratio. By analyzing the influence of the interaction of the main factors, it was found that only the fertilization type × N dose had an effect on DM content. A positive correlation between DM and methane and biogas production was also observed (Table 5). Previous studies on other perennial crops as well show that the N fertilization dose influences the N content and C/N ratio and improved the biomass quality [39,40].

**Table 3.** Characteristics of raw material and silage of *Silphium perfoliatum* used for the preparation of feedstock. (O85—organic fertilization 85 kg ha−<sup>1</sup> N; O170—organic fertilization 170 kg ha−<sup>1</sup> N; M85—mineral fertilization 85 kg ha−<sup>1</sup> N; M170—mineral fertilization 170 kg ha−<sup>1</sup> N; C—without fertilization).


DM—dry mass (% d.m.); ODM—organic dry mass (% d.m.); Ash (% d.m.); Carbon (% d.m.); Nitrogen (% d.m.); C/N—carbon to nitrogen ratio.

#### **Table 4.** Analysis of variance (*p* values) for the analyzed features.


\* Significant values (*p* < 0.05).

**Table 5.** The Pearson correlation coefficients for the analyzed trials.


\* Significant values (*p* < 0.05).

The results of our experiments showed that the highest C/N ratio was found in *Silphium perfoliatum* raw biomass with the organic fertilization dose of 85 kg ha−<sup>1</sup> N (62.3); meanwhile, the lowest C/N ratio was found in *Silphium perfoliatum* raw biomass with the mineral fertilization dose of 170 kg ha−<sup>1</sup> N (41.7) (Table 3). However, the fertilization type and N dose had a significant impact on the C/N ratio in the biomass (Table 4), but the values of this parameter were not correlated with the production of biogas (Figure 1). The results of our investigation showed the opposite of the observation regarding other energy crops which show that there was a correlation between the C/N ratio and biogas yield; this is not the rule, but the inappropriate C/N ratio is unfavorable for AD [40].

**Figure 1.** Correlation of biogas yields of substrates with a C/N ratio of raw (**a**) and silage (**b**) from *Silphium perfoliatum*.

The characteristics of the mixture of anaerobic sludge and substrate are provided in Table 6. The carbon and nitrogen (C/N) ratio in the substrate is one of the most important factors that influence biogas production [41]. In the present study, it was found that the use of *Silphium perfoliatum* biomass as a feedstock for anaerobic digestion significantly improved the value of the C/N ratio. However, the literature review provides the optimal ranges of the C/N ratio for an undisturbed course of anaerobic digestion in the range of 10 to 30 [42] or even in a narrower range from 20 to 30 [43].


**Table 6.** Characteristics of the mixture of anaerobic sludge and substrate raw material/silage of *Silphium perfoliatum* used for the anaerobic digestion test.

DM—dry mass (% d.m.); ODM—organic dry mass (% d.m.); Ash (% d.m.); Carbon (% d.m.); Nitrogen (% d.m.); C/N—carbon to nitrogen ratio.

#### *3.2. Methane and Biogas Production*

Daily biogas and methane production from the raw substrates and silages of *Silphium perfoliatum* is presented in Figure 2. The methane and biogas yields of *Silphium perfoliatum* averaged between 222.82 and 361.18 NL kg−<sup>1</sup> VS, respectively, for raw biomass, and 200.09 and 317.59 NL kg−<sup>1</sup> VS for silage. Methane yields are evaluated on a DM–basis, but the results are presented and discussed on a VS–basis. Higher methane yields were obtained in Germany, 232–321 NL kg−<sup>1</sup> VS [32,44–47], the Republic of Moldova, 275 NL kg−<sup>1</sup> VS [48] and the Czech Republic, 276 NL kg−<sup>1</sup> VS [33]. In the present study, methane and biogas production showed differences between substrate type—raw material and silage. The methane production differed significantly in the case of substrate type, ranging from 193.59 to 243.61 NL kg−<sup>1</sup> VS (Figure 2). The highest methane and biogas yield: 243.61 and 395.15 NL kg−<sup>1</sup> VS, respectively, was achieved from raw material with the mineral fertilization dose of 170 kg ha−<sup>1</sup> N (Figure 2a), as well as 204.26 and 327.45 NL kg−<sup>1</sup> VS, respectively from silage with the mineral fertilization dose 170 kg ha−<sup>1</sup> N (Figure 2b). The highest effectiveness was achieved with the mineral fertilization dose of 170 kg ha−<sup>1</sup> N and silage (Figure 2b) at the production rate of r = 90.0 cm<sup>3</sup> d−<sup>1</sup> and methane content of 63.2 ± 0.8% (Table 7) and with the mineral fertilization dose of 170 kg ha−<sup>1</sup> N and raw biomass (Figure 2a), at the production rate of r = 75.1 cm<sup>3</sup> d−<sup>1</sup> and methane content of 62.2 ± 3.2% (Table 7). Nonetheless, there were not any significant statistical differences regarding biogas and methane production between fertilization type, and the N dose and between all interactions (Table 4). In a similar study where different energy crops were investigated, it was found that the N dose significantly influenced the methane and biogas production (maize and sunflower) but was not a rule for all energy crops (sorghum and triticale) [40].


**Table 7.** Biogas production rate (r), the reaction rate constant (k) and methane (CH4), carbon dioxide (CO2) content in biogas of the analyzed raw material, and silage of *Silphium perfoliatum*.

#### *3.3. Methane Content*

The biogas production rate, reaction rate constant, methane and carbon dioxide content in biogas from raw material and silage is presented in Table 7. It was found that the *Silphium perfoliatum* silage was easier and faster biodegradable in anaerobic conditions. In the case of silage, r values ranged from 80.8 to 90.0 cm3 d–1. In the case of raw biomass, they ranged from 65.5 to 75.1 cm3 d–1. The highest content of methane was achieved in silage and raw biomass substrates without fertilization, 63.6% and 62.4%, respectively. But, there were no significant statistical differences regarding the content of methane and carbon dioxide between analyzed features (substrate type, fertilization type and N dose) and between their interaction (Table 4). In a study conducted in Poland, the methane content of maize straws was found between 48.97 and 50.26% CH4 [49]. Of course, this value (of corn straw) is much lower compared to the maize silage, which has a value corresponding to 56–59% CH4 [40], or even up to 65% CH4 at the beginning of the process [50].

**Figure 2.** *Cont*.

**Figure 2.** Cumulative methane and biogas yield (NL kg−<sup>1</sup> VS) of *Silphium perfoliatum* as raw biomass (**a**) and as silage (**b**) in the 25-day test, depending on the type of fertilization (kg ha−<sup>1</sup> N): (**A**) mineral fertilization 85, (**B**) mineral fertilization 170, (**C**) organic fertilization 85, (**D**) organic fertilization 170, (**E**) without fertilization.

#### *3.4. Digestate Characteristic*

Digestate is the substance that remains after the end of the biogas generation process. It is rich in various active substances that can be extracted or reused as fertilizer, depending on the content of micro and macronutrients [38].

Its composition and the amounts of certain elements largely depend on the raw material used to produce biogas. The content of the DM, ODM, ash content, C/N ratio, and nitrogen (N) of the digestate and inoculum after anaerobic digestion (I.A.A.D) is presented in Table 8. The measurements were carried out in three replication and the results were averaged. The studied digestate DM had values between 6.7 and 6.9% depending on the fertilization dose supplied to *Silphium perfoliatum*, and was slightly lower for the digestate obtained after AD (anaerobic digestion). The carbon and nitrogen content of digestate is very important for the C/N ratio. To be used safely as fertilizer in agriculture, it is recommended the C/N ratio be between 15 and 20 without some pretreatment operations [51]. This ratio was much lower in the present study (between 11.5–12.3 from silage and 12.1–12.8 from raw material).

**Table 8.** Characteristic of digestate from raw material and ensiled *Silphium perfoliatum*.


DM—dry mass (% d.m.); ODM—organic dry mass (% d.m.); Ash (% d.m.); Carbon (% d.m.); Nitrogen (% d.m.); C/N—carbon to nitrogen ratio; I.A.A.D—inoculum after anaerobic digestion.

#### **4. Conclusions**

In the present study, the influence of different fertilization types, nitrogen dose and substrate types (row biomass and silage) of the Silphium perfoliatum for biogas production was investigated. It was found that the substrate type has a significant influence on most of the analyzed features. This study indicates that *Silphium perfoliatum* can be used to produce biogas. However, the yield of biogas and methane may differ under the effect of different types and doses of fertilizers, although the differences were small. On the other hand, the yield of methane and biogas significantly depends only on the substrate type. It is noteworthy that the C/N ratio is an important factor that influences biogas production but, in our study, there was no correlation between these two parameters. Future studies will require an investigation of the amount of biomass per hectare, to determine what amount/yield of biogas and methane can be obtained from a given area depending on the amount of fertilizer used per hectare.

**Author Contributions:** Conceptualization, D.P., M.D. and M.J.S.; methodology, M.D. and D.P.; formal analysis, M.D. and M.J.S.; validation, M.D. and M.J.S.; investigation, D.P. and M.D.; resources, M.D. and M.J.S.; data curation, D.P., M.D. and M.J.S.; writing—original draft preparation, D.P.; writing—review and editing, D.P., M.D. and M.J.S.; visualization, D.P., M.D. and M.J.S.; supervision M.D. and M.J.S.; funding acquisition, M.D. and M.J.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The results presented in this paper were obtained as part of a comprehensive study financed by the University of Warmia and Mazury in Olsztyn, Faculty of Agriculture and Forestry, Department of Genetics, Plant Breeding and Bioresource Engineering (granted by Ministry Education and Science No. 30.610.007-110).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** Dumitru Peni is a recipient of a scholarship from the program of Interdisciplinary Doctoral Studies in Bioeconomy (POWR. 03.02.00-00-I034/16-00), which is funded by the European Social Fund. We would also like to thank the technical staff of the Department of Genetics, Plant Breeding and Bioresource Engineering and the Department of Environmental Engineering for their technical support during the experiment.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


## *Article* **Influence of Growing** *Miscanthus x giganteus* **on Ecosystem Services of Chernozem**

#### **Yana Vodiak 1, Yurii Tsapko 1, Anatolii Kucher 2, Vitaliy Krupin 3,\* and Iryna Skorokhod <sup>4</sup>**


**Abstract:** The paper investigates the optimization of ecosystem services of podzolized heavy loamy chernozem (black soil) as a result of the cultivation of the perennial energy culture of *Miscanthus x giganteus*. The research was conducted on an experimental land plot during 2016–2021. No fertilization was applied to the soil during the experiments, and over the years of research, the growing seasons were accompanied by abnormal droughts, but even under such conditions, the plants of *Miscanthus x giganteus* gradually increased their yield. At the initial stage of research, in the third year of cultivation, dry biomass of *Miscanthus x giganteus* was obtained at 14.3 t/ha, in the fourth year–18.6 t/ha, and already in the fifth and sixth years, 21.7 and 24.5 t/ha, respectively. That is, energy-wise, the harvest for the last year was equivalent to 15.9 tons of coal or 12,618 m3 of natural gas. Cultivation of *Miscanthus x giganteus* on black soil for six years has improved the provision of its ecosystem services, regulation, and ecosystem maintenance services. The possibility of growing perennial energy crops on agricultural soils has been proven by obtaining a significant amount of biomass and a positive phytoremediation effect on the soil by reducing erosion, preserving biodiversity, sequestering carbon, and sustainably improving the ecological situation.

**Keywords:** *Miscanthus x giganteus*; biomass; energy crops; soil; ecosystem services; carbon sequestration; podzolized chernozem; black soil

**1. Introduction**

The importance of a stable energy supply is increasing in the global perspective, as the energy demand is expected to grow at a fast pace in the next decades [1–3] along with population and economic growth [4,5]. Recent geopolitical events associated with the Russian aggression against Ukraine [6] revealed the vulnerability of the current energy supply structure [7], where dependency not only on fossil fuels but also on its particular unstable suppliers, has the potential to distort the global energy security in case of unforeseen political shocks, thus undermining the feasibility of substantiated and set development paths [8] worldwide.

In the past years, key factors influencing the energy policies of the developed countries have been arising mainly from the climate change agenda [9,10], thus targeting to increase the share of renewable energy generation [11,12] and search for ways to limit the greenhouse gas emissions [13,14] from the economic sectors. In current conditions, the role of renewable energy generation representing decentralized and local sources [15,16] of sustainable energy is gaining additional importance and puts the energy transformation agenda on top of development priorities.

**Citation:** Vodiak, Y.; Tsapko, Y.; Kucher, A.; Krupin, V.; Skorokhod, I. Influence of Growing *Miscanthus x giganteus* on Ecosystem Services of Chernozem. *Energies* **2022**, *15*, 4157. https://doi.org/10.3390/en15114157

Academic Editor: Dino Musmarra

Received: 14 May 2022 Accepted: 4 June 2022 Published: 6 June 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Energy based on the use of biomass is among the key sustainable approaches [17] to its generation, allowing us to obtain clean energy in terms of associated greenhouse gas emissions. Additionally, the cultivation of energy crops has numerous economic, environmental, and even social effects, which combined show the importance of substantiated development of this approach in theory and its implementation in practice.

These effects can also be assessed within the concept of ecosystem services, the benefits of which are within reach due to their integrative and interdisciplinary nature as they include economic, environmental, and social dimensions [18]. The services provided by such ecosystems could have a positive effect on climate regulation (through the level of carbon sequestration), structure and quality of soils, as well as water availability and cycling [19,20].

Applying and valuing ecosystem services is seen as an innovative step toward sustainable land use. Assessing these services can reveal the impact of energy crops and add objectivity to the renewable energy debate. The concept of sustainable land management should take into account the current and possible future impacts of energy crop production as well as people's preferences for achieving long-term sustainable solutions [18]. Increased demands on renewable energy are likely to result in the allocation of more land for the production of bioenergy plants. Therefore, land-use change is being increasingly verified through environmental impact assessments, which [21] propose to include a more complete study of ecosystem services.

For a comprehensive assessment of the sustainability of energy production from biomass, it is necessary to take into account the entire life cycle of production and combustion of crops for a wide range of indicators of ecosystem services. Therefore, Lovett et al. [22] in their article present the basis for such an assessment based on the synthesis of a large amount of data on the impact on ecosystem services of bioenergy crops (for example, low vegetation and *Miscanthus x giganteus*), which makes it possible to compare the impact on ecosystems between energy systems.

Ecosystem services are the bridge that exists between nature and people [23], as they can be defined as the direct or indirect contribution of ecosystems to human well-being [24]. Soils provide and regulate a large number of ecosystem services, yet imbalanced or nonsustainable practices can as well produce disservices and lead to soil degradation [25]. Thus, it is important to utilize experimental approaches to verify agricultural practices in set conditions, which allow for substantiated results and grounded policy and practical recommendations.

The Ukrainian background is especially important in this research, as for this country, the latest geopolitical developments further limit the availability of traditional energy sources based primarily on fossil fuels. While the renewable energy generation in Ukraine took place in past decades in a rather slow manner [26], current conditions further amplify the need to diversify the energy sources, yet also continue transformation towards more sustainable energy generation. Thus, the current deficit of fossil fuels in Ukraine contributes to the even more urgent necessity for the development of "green energy", among others, through the cultivation of energy crops with a low-carbon footprint, which opens up opportunities for sustainable biofuel production and, together with the development of wind and solar energy production, steadily reduces the release of greenhouse gases into the atmosphere. Increasing the supply volume of such fuels is extremely important and relatively easily achievable due to the assimilation of large areas not only of sown plantations but also of low-productive "problem" lands, as alternatives to traditional ones, for growing energy crops. In addition, the cultivation of energy crops and biofuels serves as a very important compromise between the development of the energy sector and the "environmental friendliness" of industrial production.

It is this strategy for the development of "green energy" that allows solving the problem of balance between meeting the social, economic, and environmental issues arising in the bioenergy generation industry, which are considered by the concept of ecosystem services. The main advantages of energy crops from the point of view of soil science and the provision of ecosystem services are the suitability for growing on low-productive lands, the possibility of minimal application of fertilizers (or even abandonment of them), no need for weed control (except for one-time treatment in the first year of planting), and phytoremediation ability. This is especially noticeable when compared to permanent fertilization and pest control when growing traditional food and forage crops, which have significantly higher costs than those that cannot function normally and grow on non-agricultural land. Thus, the cultivation of energy crops invariably meets the social and economic needs of society, increasing the profits of entrepreneurs or farmers, meeting energy needs, and, in the long term, increasing the value of ecosystem services through effective management and potential restoration of soil quality. In this work, we draw attention to the fact that in the realities of Ukraine, the cultivation of energy crops with rational use is quite possible on agricultural land [27,28].

Therefore, the purpose of this publication is to detect and reveal the possibilities for optimization of ecosystem services of podzolized heavy loamy chernozem due to the cultivation of *Miscanthus x giganteus*.

#### **2. Materials and Methods**

The research was carried out during 2016–2021 aimed to optimize the ecosystem services of podzolized heavy loamy chernozem while growing the "Zvezdotsvetosenniy" *Miscanthus x giganteus* (referred to later on as *Mischanthus*) variety in the stationary field experiment of the National Scientific Center "Institute for Soil Science and Agrochemistry Research named after O.N. Sokolovsky", enterprise "DG "Grakivske", the village of Novyi Korotychin the Kharkiv region of Ukraine (Figure 1).

**Figure 1.** Experimental research area in Ukraine in Kharkiv region. Source: own elaboration.

The relief of the experimental field is leveled, has a gentle 2–3◦ slope of northern exposure. The field is bounded on all four sides by protective strips. Podzolized heavy loamy chernozem in the experimental area is characterized by the following parameters of the arable layer: pH aq. 5.9–6.0; the carbon content of organic matter is 1.89%; physical clay content is 43%. A one-factor experiment, which did not provide for the application of fertilizers and the use of plant protection products to assess the direct impact of growing *Mischanthus* on the studied soil, it was planted twice: in 2016 (*Mischanthus x giganteus* I) and 2019 (*Mischanthus x giganteus* II). Soil sampling was carried out from layers 0–20, 20–40, and 40–60 cm directly under the plants in triplicate according to Ukrainian state standards DSTU 4287: 2004 and DSTU ISO 11464: 2007. The number of ground invertebratesmicroarthropods (the method of eclectation according to Berlese in Tullgren's modification). Counting the yield of *Miscanthus* was carried out by the method of test plots (sheaves) in triplicate followed by weighing. The carbon content in organic matter was determined by the oxidometric method–DSTU 4289:2004.

The number of microarthropods was determined by the selective Tullgren method, which is based on the use of a trait common to all soil inhabitants-the desire to penetrate deep into the soil when the upper layers of the soil dry out. Brief description of the measurement method: soil samples (from a layer of 0–20 cm) of a fixed volume (150 cm3) were placed in a sieve inserted into a funnel of a slightly larger diameter, under which a vessel with a fixing solution (70% alcohol) was placed. Natural light was used to dry the surface of the soil sample. The number of microartopods that moved down and, sliding along the walls of the funnel, moved into the fixative liquid was counted after distillation using a magnifying glass, previously filtered on filter paper. The results were statistically processed using Microsoft Excel.

#### **3. Results**

The idea of the study is based on obtaining new scientific knowledge about the influence of constant (for five years) cultivation of a perennial energy crop of *Miscanthus* on the optimization of ecosystem services in podzolized heavy loamy chernozem. It is especially important to receive up-to-date scientific information on improving the provision of ecosystem services by soil, which contributes to the solution of the tasks under the UN Sustainable Development Goals (UN SDGs) related to food security, water scarcity, climate change, loss of biodiversity, and threats to public health [29].

The spread of degradation processes due to irrational use of land—excessive plowing, short crop rotations, and rapid climatic changes—forces the scientific community and specialists to intensively search for fundamentally new ways to restore soil fertility, which are used in agricultural production. In this context, it is important to understand that the guarantee of agroecological stability of soils, the promotion of the development of self-reproduction of their fertility, and buffering capacity is the preservation of biological diversity [30,31].

Based on the positive phytoremediation experience of growing energy crops [32,33], we have established a positive effect of growing *Miscanthus* on podzolized heavy loamy chernozem in relation to the optimization of ecosystem services.

#### *3.1. Weather Conditions at the Research Site*

The climatic changes observed in recent years [34] are confirmed by the fact that on the experimental site during the research period from 2016 to 2021, there was an increase in average monthly temperatures (Figure 2) as well as a noticeable decrease in the amount of precipitation (Figure 3).

Assessing the weather data, we note that in the Kharkiv region, even before the beginning of the second decade of the 21st century, the average monthly rainfall was at the level of 43 mm, which means, about 520 mm came to the earth's surface annually, and about 260 mm per year during the growing season. Since 2011, almost every year the amount of precipitation has dropped significantly, and the average value of the air temperature has increased.

Aridization, or signs of desertification, is especially noticeable in September, which is the very month in Ukraine when agricultural enterprises plant winter crops. However, now the realities of the weather conditions in September are as follows: The air temperatures are quite high, and there is practically no natural moisture in the soil (see Figure 2), which

means the problems of agricultural production caused by climatic changes are clearly observed.

**Figure 2.** Average monthly temperature within the periods April–September in 2016–2021. Source: own elaboration.

**Figure 3.** The amount of precipitation within the periods of April–September in 2016–2021. Source: own research results.

However, growing *Miscanthus* on black soil, even in such challenging weather conditions, has not prevented the soil from improving ecosystem services, as evidenced by the gradual increase in yields of this energy crop.

#### *3.2. Harvest of Miscanthus x giganteus*

The world practice of growing *Miscanthus* involves accounting for the harvest in the third year after planting, so we have provided data on the harvest since 2018 (Table 1).


**Table 1.** Yield of *Miscanthus x giganteus* on black soil in 2018–2021, dry weight t/ha.

Source: own research results.

The peculiarities of *Miscanthus* cultivation are that the harvest is usually not taken into account for the first two years, and the harvest is recorded from the third year. It was found that even in relatively dry conditions, *Miscanthus* plants produce significant volumes of biomass without reducing soil productivity, even without fertilization. So, in the third year of cultivation in 2018, the yield of dry biomass of *Miscanthus* was 14.3 t/ha, in 2019–18.6 t/ha, in 2020–21.7 t/ha, and already in September 2021, it was 24.5 t/ha. The harvest for the last year is equivalent to 15.9 tons of coal, 9.8 tons of crude oil, 41.7 tons of timber, or 12,618 m3 of natural gas [35].

Due to the fact that in our studies, podzolized chernozem during the cultivation of *Miscanthus* was not subjected to agrotechnological processing, starting from the second year of cultivation, and the complete rejection of any fertilizers and plant protection products, we received a significant amount of biomass of *Miscanthus*, which indicates a high ecological value and the profitability of growing it. According to scientists [36], starting from the third year, the profitability of *Miscanthus* cultivation is 726% and can remain almost at this level for many years until its complete elimination.

Energy raw materials are referred to as an ecosystem supply service that is the easiest to understand and quantify. At the same time, the resulting harvest is a material benefit that has a specific price in monetary terms and a guaranteed energy supply. On the Ukrainian market, the cost of 1 ton of *Miscanthus* pellets is about UAH 4500, and the cost of 1 ton of straw briquettes is only UAH 2700.

#### *3.3. Carbon Content in Soil Organic Matter*

Studies have shown that under the influence of growing *Miscanthus* on podzolized heavy loamy chernozem, the amount of organic matter carbon in the arable and subsoil layers increases (Figure 4).

**Figure 4.** Carbon content in organic matter of chernozem, May (**a**)–September (**b**) 2018–2020, in %. Source: own research results.

It was found that over three years in the 0–20 cm layer in May, the organic carbon content increased from 1.91% in 2018 to 2.06% in 2020, while in September this indicator changed over the same years, respectively, from 1.92% to 2.11%.

In the subsurface layer (20–40 cm) of the studied chernozem, a similar tendency is observed with respect to a gradual increase in the carbon content of organic matter. The established pattern is extremely important for the development of measures to reduce greenhouse gas emissions into the atmosphere, which is a powerful argument for fulfilling Ukraine's obligations, which are reflected in a number of state documents, in particular: "Concept for the implementation of state policy in the field of climate change for the period up to 2030" (Order of the Cabinet of Ministers of Ukraine dated 6 December 2016 No. 932-r); "National Action Plan to Combat Land Degradation and Desertification" (Order of the Cabinet of Ministers of Ukraine dated 30 March 30 2016 No. 271-r). A gradual increase in the organic carbon content in the studied chernozem under the *Miscanthus* indicates an improvement in the supporting ecosystem service, which, together with a regulatory service (habitat formation, soil formation), provides a significant improvement in the ecological state of this chernozem. The ability of energy crops to store carbon in soil can be attributed to several ecosystem services. Firstly, this is a regulation service—that is, improving soil quality by increasing carbon as the main humus-forming element and improving air quality due to a decrease in carbon dioxide near plantations with energy crops; secondly, the service of maintaining ecosystems, because the content of this element in the soil is part of the process of the biogeochemical carbon cycle, and, consequently, a decrease in the release into the atmosphere, and therefore, counteraction to global warming.

#### *3.4. The Number of Microarthropods in the Experiment*

The biodiversity of soil microfauna, numerous representatives of which are microarthropods–invertebrate oribatids (Oribatida, Acarina carapace mites) and colembola (Springtail Collembola), plays an important role in the destruction and transformation of organic matter. It should also be noted that these soil microorganisms are extremely sensitive and are often used as bioindicators of environmental changes. Since their number clearly reacts to air temperature, moisture, and soil chemical composition, our results vary somewhat depending on the month and year of the study. The number of oribatids on the studied soil under the *Miscanthus* is shown in Figure 5.

**Figure 5.** The number of oribatids on the studied soil under the *Miscanthus*: May 2019–НIР05 = 225; September 2019–НIР05 = 146; May 2020–НIР05 = 130; September 2020–НIР05 = 192; May 2021– НIР05 = 354; September 2021–НIР05 = 142. Source: own research results.

The figure clearly shows that in 2020 the number of oribatids in May and September was 1086 and 908 specimens/m2, respectively, and 1260 and 1264 specimens/m2 under *Miscanthus*. However, in 2021, the number of oribatids almost tripled compared to previous years because May 2021 was characterized by moderate temperatures and relatively high rainfall of 84 mm.

Our studies, carried out on podzolized heavy loamy chernozem in 2020, found that in the control, the number of colemboles (Figure 6) in May was 1622, and in September, 1986 ind./m2, and under *Miscanthus* plants, respectively, 1628 and 3240 ind./m2.

**Figure 6.** The number of colemboles on chernozem under *Miscanthus*: May 2019–НIР05 = 362; September 2019–НIР05 = 232; May 2020–НIР05 = 284; September 2020–НIР05 = 188; May 2021– НIР05 = 204; September 2019–НIР05 = 192. Source: own research results.

The number of colembol specimens differs from oribatids in variants and decreases somewhat over time, although it remains much higher than in the control. This indicator is due, to a large extent, to the increase in the number of ticks (oribatids) because some of them are predators that feed on colemboles. Thus, microarthropods sensitively react not only to weather conditions but also to the species composition of plants in the ecosystem and to the species composition of soil microorganisms.

In general, the number of microarthropods indicates that under the plants of the *Miscanthus* there are more favorable conditions for their habitation and development and, consequently, for the biodiversity of the ecosystem as a whole, which refers to a supporting ecosystem service. Under such conditions, the activation of the biological factor (microarthropods) enhances the course of the soil-forming process towards self-adaptation and self-reproduction, which will certainly lead to an improvement in soil fertility.

#### **4. Discussion**

Based on the achieved results, it is assumed that this research has obtained positive evidence regarding the impact of the cultivation of *Miscanthus* on the optimization of ecosystem services in podzolized loamy chernozem, which is usually used for growing traditional crops of wheat, corn, sunflower, and beet.

The results are consistent with the findings of other researchers on the cultivation of individual bioenergy crops on marginal lands [37,38]. The results of the study are of great practical importance in the context of achieving climate neutrality by 2050, in particular, by increasing the area of cultivation of bioenergy crops, including those on marginal lands [39]. It should be noted that the use of biomass for energy crops in combination with other alternative energy sources [40,41] is one of the priority areas for ensuring low-carbon development of the agricultural sector and the economy as a whole.

Integration of energy crops into agricultural landscapes can foster permanence and maintain sustainability if they are placed in such a way as to stimulate multiple ecosystem services and mitigate harmful ecosystem effects from existing crops [42], as well as promote balanced land use [43].

For example, energy crops in the coastal regions of the midwest United States have a positive effect on ecosystem services while the benefits-costs ratio has fluctuated significantly. At the same time, the overall monetary value of the improved ecosystem services associated with the introduction of perennial energy crops was much lower than the opportunity cost. The mismatch between recoverable costs and social value is a fundamental challenge for the expansion of perennial energy crops and sustainable agricultural landscapes [42] and the potential for biomass supply [44]. Analyzing the dynamics and uncertainty of land-use transformation for the production of perennial energy crops, [45] examined the effects of payment for ecosystem services policies. It has been found that the current expected profit from growing perennial energy crops (including switchgrass) is insufficient for these crops to be widely adopted by American farmers due to relatively unstable yields, volatile incomes, and high costs of growing crops. At the same time, switchgrass has the potential to provide energy while reducing greenhouse gas emissions [46].

In this context, the results of a survey of farmers and non-experts on the perception of energy crop production in Germany turned out to be interesting. In particular, it was found that many farmers consider themselves responsible for the provision of many ecosystem services while they prefer the regional scale of growing energy crops based on conventional crops. Most of the non-specialists interviewed noted the ambiguity of energy crops as a source of energy without side effects. In layman's opinion, the use of biomass for renewable energy production is not an important ecosystem service. Biomass production should be limited to fields that do not require food production and the use of crop residues or materials for landscape management [46].

Global scientists and practitioners are mainly exploring the possibilities and cultivation of energy crops on marginal lands. For example, [37] notes in the article that: (i) ecosystem services differ depending on the type of marginal land; (ii) special bioenergy crops can improve ecosystem services on marginal lands; (iii) there is a need to intensify research in this direction, as there is currently a lack of field data on the productivity of energy crops on marginal lands, and ecosystem services are hardly discussed in the literature. This was among the reasons why the current research was conducted, aiming to fill in the existing gap in experimental data, which would be beneficial for further substantiation of strategies to expand the cultivation of *Miscanthus* in particular soil conditions, as well as to take these findings into account in the policies being implemented towards the protection of the environment, achieving climate-neutrality and improving biodiversity, as well as supplying clean energy from a renewable source.

Another direction to increase the impact of the cultivation of specialized energy crops is to do this on marginal lands, which can provide, in particular, such ecosystem services as biomass production, control of water and wind erosion of soil, sequestration of carbon in the soil, absorption or content of pollutants or metals, stabilization or reclamation of disturbed soils, and improvement of properties. It is summarized in [37] that growing energy crops on marginal lands can increase soil carbon sequestration, restore contaminated or compacted soils, and improve biodiversity. Fertilizing or adding organic improvers increases biomass yield and carbon sequestration on marginal lands [37].

Growing energy crops on marginal lands is considered a useful opportunity for farmers against the progressive risk of underutilization or non-use of these lands. Scenario modeling results indicate the positive impact of energy crops on ecosystem services in terms of environmental quality and biodiversity value [38]. At the same time, other studies show that increased production of bioenergy crops leads to increased soil-use and land-use conflicts and also decreases the supply of several ecosystem services, such as regulation of soil erosion, carbon sequestration, environmental value, and landscape aesthetic value [38]. Therefore, this indicates the need to continue experimental research to answer the question of the impact of energy crops on soil ecosystem services. Among the new and promising areas of research is also the evaluation of the efficiency of growing bioenergy crops using alternative fertilizer systems, including green manure [47].

A substantiated approach needs to be taken with each agricultural practice, as particular ones are especially influential on sustainable development and its goals (SDGs). The authors argue [48], in this context, that such ecosystem service as soil conservation

service can be among those, as it contributes simultaneously to SDG 15 (Life on land), SDG 13 (Climate action), and SDG 6 (Clean water and sanitation), as well as several others to a lesser extent. In our opinion, the cultivation of *Miscanthus* on black soils under the conditions verified within the experimental research proves that such an approach is highly beneficial for the soil conservation service and thus is of high importance in light of ensuring sustainable development.

#### **5. Conclusions**

Based on experimental studies conducted in 2016–2021 on the optimization of ecosystem services of podzolic heavy loamy chernozem by growing *Miscanthus*, its positive impact on the analyzed soil ecosystem services—supply and regulation—was established. The cultivation of *Miscanthus* on chernozem even in relatively dry conditions over the years of research has not prevented the improvement of ecosystem services provided by this soil, as evidenced by the gradual annual increase in the yield of this energy crop.

It is established that under the influence of the growth of *Miscanthus* on chernozem, the amount of carbon organic matter in the soil increases both in the arable and in the underlying layer. The gradual increase in the organic carbon content of chernozem under *Miscanthus* indicates improved support for ecosystem services, which together with regulatory services (habitat formation, soil formation), provides a significant improvement in the agro-ecological condition of the soil and environment. Growing perennial energy crops on agricultural soils provides a significant amount of biomass and a positive phytoremediation effect on the soil by reducing erosion, conserving biodiversity, carbon sequestration and improving the agri-environmental situation.

Further research on the impacts of *Miscanthus* cultivation on chernozem ecosystem services should focus on (i) the economic valuation of possible ecosystem services and an analysis of the cost-benefit ratio of growing energy crops; (ii) strategies for sustainable management of energy crops in specific areas, climatic and socio-economic criteria; (iii) the development of innovative bioenergy projects for the cultivation of energy crops and an assessment of their economic efficiency and investment attractiveness.

**Author Contributions:** Conceptualization, Y.V., Y.T. and A.K.; methodology, Y.V., Y.T. and A.K.; software, Y.V. and Y.T.; validation, Y.V., Y.T. and A.K.; formal analysis, Y.V., Y.T. and A.K.; investigation, Y.V. and Y.T.; resources, Y.V. and Y.T.; data curation, Y.V., Y.T. and V.K.; writing—original draft preparation, Y.V., Y.T., V.K., A.K. and I.S.; writing—review and editing, V.K., A.K. and I.S.; visualization, Y.V. and A.K.; supervision, Y.T. and A.K.; project administration, A.K. and V.K.; funding acquisition, V.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


## *Article* **The Potential of Ukrainian Agriculture's Biomass to Generate Renewable Energy in the Context of Climate and Political Challenges—The Case of the Kyiv Region**

**Adam W ˛as 1,\*, Piotr Sulewski 1, Nataliia Gerasymchuk 2, Ludmila Stepasyuk 3, Vitaliy Krupin 4, Zoia Titenko <sup>5</sup> and Kinga Pogodzi ´nska <sup>1</sup>**


**Abstract:** Increasing the share of renewable energy in the final energy consumption is a way to ensure independence from external supplies of fossil fuels, which is a fundamental political and economic challenge for many countries nowadays. One such country is Ukraine, which depended on Russian gas supplies and energy (electricity) from nuclear power plants. Russian gas is not delivered anymore to Ukraine, and Russians have recently taken over some of the nuclear power plants. The changes in the political situation force Ukraine to search for alternative energy sources. In countries with high agricultural production potential, one of the basic options seems to be popularization of modern methods of obtaining energy from biomass (bioenergy), which so far has played a minor role in the country's energy mix (less than 2% in the case of Ukraine). The analysis carried out on the case of the Kyiv Region indicates that the annual economic potential of biomass in the region is equivalent to 1743 thousand toe (tonnes of oil), and its use allows them to save about 43% of fossil fuel annually.

**Keywords:** biomass; energy potential; alternative energy sources; resources; enterprises; fuel

#### **1. Introduction**

Due to globally observed climate challenges, the energy issue has become one of humanity's most important problems to solve in the near future [1–3]. Global energy production is still dominated by fossil fuels, accounting for 80% of the global energy mix [4]. Simultaneously combustion of fossil fuels (coal, oil, and gas for electricity, heat, and transformation) is the main contributor to global climate change, accounting for over 75% of global GHG emissions [5] and almost 90% of all carbon dioxide emissions [6]. Climate scientists' position is clear—moving away from fossil fuels is essential to stop further climate change [7,8].

The current level of renewable energy development differs significantly between different regions of the world and even neighboring countries [9,10]. On average, less than 11% of global primary energy consumption came from renewable sources in 2019, of which 6.4% was traditional biomass combustion [9]. These statistics show that biomass, particularly modern methods of its use, such as processing into biogas or biomethane, remains a relatively underused renewable energy source. Nevertheless, the production of agricultural biogas and other forms of biomass is an advantageous option in countries with

**Citation:** W ˛as, A.; Sulewski, P.; Gerasymchuk, N.; Stepasyuk, L.; Krupin, V.; Titenko, Z.; Pogodzi ´nska, K. The Potential of Ukrainian Agriculture's Biomass to

Generate Renewable Energy in the Context of Climate and Political Challenges—The Case of the Kyiv Region. *Energies* **2022**, *15*, 6547. https://doi.org/10.3390/en15186547

Academic Editor: Alberto-Jesus Perea-Moreno

Received: 30 July 2022 Accepted: 4 September 2022 Published: 7 September 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

significant agricultural production potential [11,12]. One of them is Ukraine, one of the most important agricultural producers in Europe and the world [13].

In the case of Ukraine (and also in many other countries), increasing the degree of biomass use (including the production of agricultural biogas) is a way to increase energy independence [14,15]. Awareness of this challenge significantly increased after Russia invaded Ukraine. Although Ukraine has not imported natural gas directly from Russia since 2015, it still remains dependent on gas imports from Western countries [16]. However, the invasion has significant consequences for the global energy sector. In particular, it relates to natural gas, which can, at least partially, be replaced by gas from biomass.

In the face of the Russian invasion of Ukraine, the challenge of increasing energy independence has become much more critical than ever before. Searching for the possibilities of using biomass for energy purposes is, therefore, a task justified for environmental reasons (replacement of fossil fuels and reduction of GHG emissions) and political reasons (increasing energy independence). There is an urgent need to search for new, alternative sources of energy, and biomass use for energy production is the most attractive option [17]. In this context, the study's goal was to assess the potential of using agricultural biomass for renewable energy production in the Kyiv region.

#### **2. Background Information**

#### *2.1. Biomass and Ukrainian Energy Sector—General Information*

Biomass is a renewable organic material of plant and animal origin and can be helpful in substitution fossil fuels. Energy from biomass can be obtained in processes such as direct combustion, thermochemical conversion, and biological conversion [18]. In practice, the most frequently applied solutions include co-firing in coal power plants, combustion of biomass in dedicated power and CHP plants, or biomass conversion into biogas in anaerobic fermentation or thermo-chemical processes (pyrolysis) [19]. One of the essential advantages of generating energy from biomass is that it is a carbon-free process because emitted CO2 was previously assimilated by plants [19]. Moreover, among the benefits of biomass can be mentioned wide availability, reduced overreliance on fossil fuels, usually lower prices compared to fossil fuels, and reduced waste in landfills [20]. Besides, biomass is a local fuel, and its use increases the regional added value by minimizing fossil fuel imports. Moreover, biomass production and supply contribute to creating new workplaces, mainly in rural areas, which is vital for the local economy.

Shortcomings of biomass use are reflected in the lower efficiency of some biofuels compared to fossil fuels. Although burning biomass is carbon neutral, it still generates air pollution. Overuse of wood can lead to deforestation, and biomass plants usually require a lot of space [20]. Biomass used for energy production may include wood and wood processing wastes, agricultural products, and food wastes as well as municipal, solid, and liquid wastes [18]. Particular hopes for the development of biomass are connected to the production of biogas [12,21].

Ukraine is one of Europe's largest energy consumers, with a primary energy consumption of 93 Mtoe (million tonnes of oil equivalent) in 2018. Domestic energy production is insufficient to meet total energy demand; it covers about 65% of energy needs [22]. In recent years, there has been a significant decrease in domestic energy production compared to 2007 by over 30% (Figure 1). Energy exports have also dropped significantly, and to a lesser extent, imports. As a result, Ukraine is most dependent on imported oil (83% of consumption) and to a lesser extent on coal (50% of consumption) and natural gas (33%), which meant that in 2018 it was necessary to import 8.5 Mtoe of natural gas, 13.5 Mtoe of coal, and 10.4 Mtoe of oil products [22].

**Figure 1.** Production, export, and import of energy in Ukraine, in thousands toe. Source: The author's calculations are based on statistics from the State Statistics Service of Ukraine [23].

The Ukrainian energy sector is mainly based on fossil fuels (natural gas, oil, and coal) and nuclear energy [22]. In the structure of primary energy consumption dominates coal (28.3%), followed by natural gas (28.2%), nuclear energy (23.4%), and oil (13.8%) [4]. The share of other energy sources, including hydropower, wind, solar, and other renewables, is less than 6% [4] (Figure 2).

**Figure 2.** Structure of primary energy consumption in Ukraine by source. Source: [24].

The importance of nuclear energy for Ukraine should be emphasized—although it accounts for less than 25% of the total primary energy, it meets half of the country's electricity needs [22]. Nuclear power plants increase the country's energy independence, but they also pose a severe threat to the whole world in the face of the Russian invasion of Ukraine. An example is the Zaporizhzhia Nuclear Power Plant (the largest nuclear plant in Europe), occupied by the Russians, over which the Ukrainian authorities lost control [25]. This case, as well as other negative experiences with the safety of nuclear power plants, forces us to ask about the further development of the energy sector in Ukraine. It is also worth paying attention to the changes in the share of renewable energy. Although it is still relatively small, in the last few years, it has increased from less than 2% in 2015 to about 6% in 2021 (excluding traditional biofuel use) [4]. The progress in the development of RES observed in recent years is connected with increasing awareness that renewable energy sources have a high potential to reduce natural gas dependency and enhance energy security. The government's decision in 2016 to withdraw from subsidizing the production of heat from natural gas turned out to be particularly important for the development of RES and made the production of heat from renewables (including biomass) comparatively

competitive (in comparison to fossil fuels) [22]. The share of renewable energy in the heating and cooling sector in 2020 was 9.3%; in the electricity sector, it was 13.9%; and in the transport sector, it was 2.5% [26]. The total installed capacity of active renewable energy projects (excluding large scale hydro generation >10 MW) was around 7.7 MW, of which 72% belong to industrial solar, 8% solar in a private household, 15.7% wind, 1.5% small hydro, and 2.3% to biomass and biogas [27]. These data indicate the relatively low importance of biomass in energy production in Ukraine, although the analyses of Lakyda et al. [28] show that the technical potential of forest biomass can be estimated at the level of 2.1 Mtoe and that of agricultural waste at the level of 12 Mtoe. Assuming the demand for primary energy is at the level of 86.4 Mtoe (in 2020), this would meet approximately 16.3% of the country's energy needs.

Many authors underline the need to diversify the Ukrainian energy mix and improve energy efficiency. For example, Lewicki [29] stressed the need for diversification of supplies, differentiation of energy balance through increased use of renewable energy sources, and increasing the energy efficiency in the historical aspect, while Gerasymchuk [30] outlined the background of using renewable energy sources in order to ensure the energy efficiency of Ukraine, given the statistic and existing situation in the energy market, and analyzed the resource base for renewable energy sources and local fuels for the energy efficiency and the reliability of Ukraine's energy supply, which became a start for this research.

The use of biomass seems particularly justified in the case of heat production, because sometimes it seems to be the only feasible option to replace fossil fuels to provide heating for buildings without easy access to other supply options [31]. Ukraine's total thermal energy consumption in 2012 was estimated at 14.03 Mtoe, of which only about 6% was covered by biomass (solid biomass and biogas) [31]. Currently, the share of biomass in Ukraine's total heat production is estimated at 9% [32].

The growth of energy production from renewable sources is an important area for replacing natural gas, as there is a large reserve for reorientating biomass exports to the domestic market. Energy security in the face of the Russian military aggression against Ukraine is another perspective that needs to be assessed and considered in the energy and bioenergy development plans. Energy generation from biomass in this regard seems to be not only sustainable, but also highly dependable [33–35]. Local generation of energy based on locally available sources allows them to sustain the needs of particular farms or even communities and ensures maintaining of their functions regardless of the exogenous shocks and national or regional grid malfunctions [36,37]. In this case, a tight connection between food and energy security strengthens the sustainability and resilience of the local food systems. It allows them to carry on with the provision of essential system functions [38].

Although the current contribution of biomass to energy generation in Ukraine remains small, it can be expected that this situation will change in the future. Geletukha et al. [39], in their complex assessment of the future bioenergy developments in Ukraine, assume the country would follow the European Green Deal and align its climate neutrality achievement and environmental development along the current European priorities. Ukraine is also a member of the European Energy Community, which has declared its conscious participation in a global policy aimed at sustainable development and reduction of harmful effects on the environment. As Ukraine is already committed to the Paris Agreement to work on the reduction of greenhouse gas emissions and the Energy Community Treaty to work towards transformation to clean energy, the development of the bioenergy sector to fulfil its green transitions is crucial.

#### *2.2. Ukrainian Agricultural Sector—Supplier of Biomass for Energy Generation*

As a country with a large agricultural sector, Ukraine has significant development potential in bioenergy. The development of the bioenergy sector is eased by vast areas of fertile croplands and less productive lands suitable for growing undemanding energy plants, a favorable climate for plant and livestock production, and the availability of the necessary human and material resources. In addition, high yields of major crops provide a sustainable resource base, which has not been exploited so far. In this regard, plant biomass plays one of the key roles in the development of bioenergy.

In the European Union, biomass for energy generation reached a share of ca. 60% among renewable energy sources, which directly contributes to the EU's energy security, as most of the demand (about 96%) is covered by domestically produced biomass [40]. Already, as of 2020, the volume of biomass consumption for energy production in the European Union is more than 120 million tonnes of oil equivalent per year [41]. As Ukraine has been granted EU candidate status, compliance with EU legislation and principles will be increasingly important. According to the EU Energy Security Strategy [42], members need to become more energy "independent" by saving energy and producing more local (RES) energy.

According to Geletukha et al. [43], Ukraine has considerable potential for renewable energy sources, one of the most extensive being biomass. Despite some fluctuations, Ukraine's volume of agricultural biomass increases almost every year due to the general trend of growth in the production and yield of major crops. Thus, in 2019, the country harvested a record amount for the last 20 years of sunflower, corn for grain, and some other cereals. Since 2000, the energy potential of straw of cereal eared crops, byproducts and waste of grain, corn and sunflower production in Ukraine has tripled, from 2.8 Mtoe in 2000 to 8.5 Mtoe in 2020. As the abovementioned authors state, agro-biomass (agricultural residues and energy crops) will remain Ukraine's primary type of bioenergy potential. Expanding the use of agricultural residues requires working out technologies for baling corn and sunflower stalks. On the other hand, energy crops for solid biofuels will continue to grow on unused (low-yield) agricultural lands.

Given that the agro-industrial resource is becoming a leading strategic bioresource, biomass from products produced in the agricultural sector can give Ukraine new opportunities for sustainable development through the production of cheap, environmentally friendly bioenergy products through efficient use of agricultural biomass. However, analysis of the use of agricultural biomass for energy purposes showed that the current level of use of energy potential of biomass in the country is very low—from 0 to 2–3% depending on the specific species, and only sunflower husk shows the level of 73.1% [44]. As the authors state, biomass's leading destination is thermal energy production, which is used for heating and hot water supply. Between 2014 and 2018, biomass's share of thermal energy was within 97% of all renewable thermal energy.

Kulyk [45] emphasizes that bioenergy development in Ukraine requires searching for ways to reduce the cost of various types of bio-raw materials in the economic justification of their production. Currently, the main components of the bioenergy production potential in Ukraine are primary agricultural residues (cereal straw, corn, and sunflower residues) and industrial cultivation of energy crops. However, the biomass production of renewable plant material from energy crops depends on many factors determining their cultivation's feasibility. Environmental influences on energy crop cultivation are mainly reflected in its effect on seed germination and the initial stages of plant growth. In order to achieve balanced cultivation and use of energy crops as plant material, ecological aspects must be taken into account. Reducing the pressure on the environment requires establishing energy plantations and growing energy crops on marginal lands with low fertility, showing signs of degradation and requiring reclamation [45,46].

Other studies [47] show that the estimated biological yield of plant biomass in Ukraine could be 64.3 million tonnes. They have also established that an increase in the use of straw for energy needs can be ensured only by increasing green manure crops in crop rotation (in particular, cultivations of cover crops within crop rotation cycles). At the same time, Hutsol [41] states that at this time, Ukraine has not approved a standardized system for measuring and accounting for solid biomass resources of forest and agricultural origin. Lack of such information, especially on energy crops, hinders the development and implementation of sustainable energy policies and projects in a particular area and the country as a whole. They also emphasize that it can be argued that there is the active use of renewable energy and increased energy efficiency in the regions of Ukraine. However, many certain regions are cautiously implementing renewable energy production systems. The authors stress, among others, that the results of their research on solid biomass (mainly from agricultural residue) in Ukraine have a high potential for fuels that can be quickly applied.

The potential of biogas production from the livestock sector of Ukraine has been assessed previously [21]. It was found that, in absolute terms, Ukraine has a significant potential for the production of agricultural biogas from animal manure, reaching nearly 3 billion m3. However, the practical possibilities of using this potential are severely limited by the dual structure of agriculture. More than half of the available manure is produced on small livestock farms that are too small scale to consider investing in biogas plants.

It should be kept in mind that the ongoing war is also affecting the agricultural sector. Reduced production (reduced sown area) of primary agricultural commodities reduces the potential for food production and limits the amount of biomass used to generate energy (even if only agri-food waste was included). Therefore, looking for biomass sources other than agriculture is worthwhile.

#### **3. Material and Methods**

#### *3.1. Case Study Area Description*

Sustainable development of bioenergy requires, first of all, a careful assessment of the available biomass potential. Therefore, we assessed, as an example, the potential of biomass used as an energy source in the Kyiv region.

The Kyiv region is one of the largest regions of Ukraine, with an area of 28.1 thousand square kilometers (without the city of Kyiv), which is 4.7% of Ukraine's territory (Figure 3). By size, the Kyiv region ranks eighth among other regions of Ukraine. Kyiv region is a metropolitan region, in the center of which is located Kyiv, the capital of Ukraine, a powerful political, business, industrial, scientific, technical, transport, and cultural center of the country, connected with the region with close commercial and social ties. The distance from Kyiv to the region's northern border is 118 km, to the southern border is 128 km, to the western border is 76 km, and to the eastern border is 112 km. A feature of the Kyiv region is the absence of a regional center. Kyiv city, where the central administrative bodies of the region are located, is the autonomic region and does not count in Kyiv region statistics. Another feature of the region is the presence of a Slavutych city, which belongs to the Chernihiv region.

**Figure 3.** Geographical location and herb of the Kyiv region in Ukraine. Source: Strategy of Kyiv region for 2021–2027 years [48].

Kyiv Region has favorable conditions for agriculture, namely the region's climate, the structure of agricultural lands, availability of the capital city Kyiv as a sales market, and a robust scientific base for implementing innovative technologies in the production and processing of agricultural products. As a result, by volume of gross agricultural production, the region ranks second among all other regions of Ukraine.

Crop production in the total agricultural production of the region takes a significant share with 62.4%. The main crops grown are grain crops, potatoes, sugar beets, and sunflowers, with a large share of perennial gardens. By zone division, the north part of the Kyiv region is located in the Polissia zone, which is characterized by a larger share of forests over the fields with the developed forest harvesting, and the south is in the forest-steppe zone. The Kyiv region is one of the leaders among grain and oil storage market operators in Ukraine, with 53 elevators operating in the region with a total capacity of 2.6 million tonnes storage of the specified crops and 45 fruit storage refrigerators. The region ranks fourth in Ukraine for egg production and takes first place by volume of livestock meat and poultry.

The Kyiv region belongs to the energy-rich regions. Energy enterprises located on its territory have a total capacity of 3200 MW, namely the Trypilska thermal power station, Kyiv hydroelectric power station, Kyiv Hydroaccumulating Electric Power Station, Bilotserkivska Thermal Power Station, and small hydroelectric power stations, as well as the Dymerska solar power plant that is among the ten most powerful solar power plants of Ukraine [48].

The Kyiv region is an agrarian region in which large volumes of byproducts and waste suitable for energy use are generated. Large areas of agricultural land create significant potential for growing energy crops. The main source of biomass in the Kyiv region is primary crop waste.

#### *3.2. General Assumptions—Methods of Calculating*

Typically, three main types of biomass potential are considered when energy production possibilities are considered, i.e., theoretical, technical, and economic potentials.

The theoretical potential is the maximum amount of terrestrial biomass theoretically available for energy production. For example, the theoretical potential of waste and residues of various types is the total volume from which energy can be extracted. The technical potential limits the theoretical to the amount of biomass that is available for processing, which is available at a specific moment under certain structural, technical, and technological conditions. When calculating it, it is essential to consider spatial restrictions caused by competition between land users and environmental factors [49].

Economic potential is an even narrower concept because it includes only that share of technical potential that provides the desired level of profitability. Therefore, within this study's framework, the cost estimation method was used instead of profitability analysis for its evaluation based on the resource-consuming concept. This approach better represents the importance of the amount of available biomass when planning the production of energy products [50]. Furthermore, the used technique allows, in addition to planning the volume of energy production, to forecast financial results from the activity.

Wood biomass, which can serve as fuel, is produced due to general and sanitary felling. Firewood, wood chips, branches, stumps and crowns, and secondary processing products—shavings and sawdust—are involved in energy production. We used the approach of determining the energy potential of wood waste *Pw* according to the formula:

$$P\_w = \left(V\_w \ast K\_1 + (V\_w - V\_{com}) \ast K\_2\right) \ast Q\_{wr}$$

where:

*Vw*—a volume of wood logging, m3;

*K*<sup>1</sup> = 0.1—waste ratio;

*Vcom*—the volume of round timber, density m3;

*K*<sup>2</sup> =1 − (0.2 ... 0.25) = 0.8 ... 0.75—the total coefficient of waste of wood's main and secondary processing. Considering standard losses during wood processing of 5–10%, we accept *K*<sup>2</sup> = 0.70;

*Qw* = 0.186 toe/dense m3—calorific value of dense wood during logging [51].

We suggest calculating the energy potential of biogas (toe) from organic waste using the formula:

$$E\_{LS} = \sum\_{i=1}^{n} \frac{365 \ast N\_i \ast q\_{mi} \ast \frac{TS\_i}{100} \ast \frac{VS\_i}{100} \ast q\_i^{b\_{\mathcal{S}}} Q\_{LHV}^{hq}}{Q\_{LHV}^{\alpha \varepsilon}}$$

where:

*Ni*—the total number of animals of the *i* species, heads;

*qmi*—yield of organic waste of the *i*-th type, kg/(hour-day);

*TSi*—share of dry substance in organic waste of the *i*-th type, %;

*VSi*—the proportion of organic substance in the dry residue, %;

*qi bg*—expected yield of biogas from an organic waste of the *i*-th type, m3/kg DOM (dry organic matter);

*Qbq LHV*—expected lower heat of combustion of biogas (LHV), generation from an organic waste of the *i* type, MJ/nm3;

*Qoe LHV* = 41.868 MJ/kg—lower heat of combustion of oil equivalent [46].

The formula determines the economic potential of biomass from pruning of fruit trees:

$$P\_{\varepsilon} = \sum Spac\_{i} \ast Pr\_{i} \ast Kt\_{i} \ast Koe\_{i}$$

where:

*Spaci*—land, the area of which is occupied by fruit trees of the *i*-th species at the fruit-bearing age, thousand hectares;

*Pri* (2.4 for pome fruit, 3.0—for stone fruit trees)—specific productivity of pruning fruit trees of the II species at the fruit-bearing age for calculating the theoretical potential of biomass, t/ha;

*Kti* = (2.4 for seed trees, 3.0—for stone trees)—the criterion of the technical possibility of pruning for calculating the technical potential of biomass;

*Koei* (0.406 for pome fruit, 0.400—for stone fruit trees)—the potential biomass coefficient in oil equivalent: the calorific value of plant waste in oil equivalent [51].

The following formula is used to determine the economic potential of processing waste:

$$P\_{\mathcal{C}} = \sum\_{i=1}^{n} \mathcal{C}pr\_i \ast Kr\_i \ast Ko e\_i$$

where:

*Cpri*—the volume of processed raw materials of the i-th type (for example, sunflower seeds);

*Kri*—the coefficient of waste generated during the processing of raw materials (*Kr* = 0.15 for sunflower seeds shows that 1 tonne of processed seeds yields 150 kg of husk, i.e., 15% of the total volume);

*Koei*—coefficient of conversion of biomass potential into oil equivalent: (for sunflower husk, it is 0.358) [51].

#### **4. Results**

Based on the results of the analysis of sunflower seed processing by agricultural enterprises in the Kyiv region, it is clear that from 2014 to 2019, its volume remained practically unchanged. In the reporting year (i.e., 2019), it amounted to 370,000 tonnes. Therefore, the economic potential of such energy-oriented production, calculated according to the above formulas, is 19.9 thousand toe (Figure 4).

**Figure 4.** Volumes of processed raw materials, thousand tonnes. Source: author's calculations are based on statistics from the State Statistics Service of Ukraine [23].

At the same time, it was observed that timber felling in the region increased significantly: from 1608.7 thousand m<sup>3</sup> of wood in 2015 to 2015.2 thousand m<sup>3</sup> of wood in 2019. Thus, the difference between the reporting and base years exceeds 25%. At the same time, the volume of wood harvesting increased by 2.1 times. This increased the economic potential of wood by 1.6 times (Table 1).


**Table 1.** The economic potential of wood waste.

Source: author's calculations based on statistics from Kyiv Oblast Statistical State service [52].

A representative sample is key to objective analysis and reliable results. Based on this postulate, we took for the study of economic energy potential only agricultural enterprises of the Kyiv region with a significant number of livestock, namely: cattle—from 2000 heads, pigs—from 9000 heads, and poultry—from more than 400,000 heads. Small enterprises that do not have a centralized collection of organic waste in animal husbandry were not taken into account.

The results of the calculations show significant dynamics in the size of livestock. Thus, from 2014 to 2019, the poultry number increased by 6%, while the number of cows and pigs decreased by 15% and 1.3% (Table 2). In animal husbandry, poultry farming is the largest source of organic waste for obtaining biogas. The bird population in 2019 was the largest and amounted to about 17 million. From this volume, it is possible to get 40.6 thousand toe. Therefore, the total livestock that was analyzed to calculate the economic potential of biogas production can provide a sound output of 62 thousand toe.


**Table 2.** The economic potential of biogas from organic waste.

Source: author's calculations based on statistics from Kyiv Oblast Statistical State Service [52].

Corn and sunflower stalks, wheat, rye, barley, buckwheat, pea, soybean, rapeseed, and millet straw can be used in crop production for energy needs. Almost all grain and oil subsectors have significant potential for biogas production. The byproduct output rate determines the available amounts of straw in accordance with the agricultural crop yield. Table 3 presents the results of the analysis of the economic potential of crop production in the Kyiv region. Enterprises in the region specialize in growing corn, sunflower, soybeans, rapeseed, barley, and wheat. Byproducts are used as fertilizer, as well as for livestock maintenance, especially barley straw. This trend confirms the structure of the use of byproducts adopted in our methodology, namely that 40% of oil crops and 30% of cereals are free for biogas production.


**Table 3.** The economic potential of grain and industrial waste, thousand toe.

Source: Own calculations based on statistics from the State Service of Statistics [53].

In addition, the methodology uses the coefficient of losses and the volume of slaughtered products for fertilizers and animal husbandry needs (up to 50%).

The distribution of straw in the enterprises of the Kyiv region by areas of use shows that in 2019 the available amount of straw was 1538.4 thousand tonnes, 769 thousand tonnes of which are applied as fertilizers, 189 thousand tonnes were used for litter, and 547.8 thousand tonnes can be used for energy production.

The results show that the area under grain fruit plantations for 2014–2019 decreased by 2.6 times, and fruit trees remained unchanged under the stones. Therefore, according to our calculations, the economic energy potential of perennial plantations in the Kyiv region is 0.9 thousand toe (Table 4). However, its potential is somewhat irrelevant due to the relatively small scale of plantations.


**Table 4.** Areas of perennial plantations in fruiting age in agriculture enterprises of Kyiv region, thous. ha.

Source: Own calculations based on statistics from State Service of Statistics [53,54].

Considering the direct relationship between the yield of crops and the economic potential of byproducts, the results of the analysis showed that, in 2019, the most significant potential in oil equivalent was as follows: straw waste in the amount of 1182 thousand tonnes, wood at 432 thousand tonnes, and manure at 62 thousand tonnes. On the other hand, the husk has the lowest energy potential at only 19.9 thousand toe (Table 5). Thus, the total economic energy potential of agricultural enterprises of the Kyiv region in the amount of 1697 thousand tonnes is distributed by sources in the following ratio: stalks and straw occupy 70% of the structure, wood accounts for 25%, manure for 4%, and sunflower husks produce only 1% (Figure 5).


**Table 5.** The economic energy potential of waste in the Kyiv region, thousand toe.

Source: Own calculations based on statistics from the State Service of Statistics [53].

In 2018, 4019 thousand toe was used in the Kyiv region. At the same time, according to the results (Table 5), the economic energy potential of crop, livestock, and horticulture waste amounted to 1743 thousand toe. This amount could provide about 43.3% of the fuel needs at the expense of alternative types of biofuel. Such optimization will contribute to reducing the destructive impact of harmful emissions from petroleum fuel on the environment, increase the self-sufficiency of enterprises and their organizational and financial independence from external conditions, and reduce the production process cost.

There are no specific data about current renewable energy usage in Kyiv oblast. However, the share of the total capacity of boiler plants operating on alternative fuel types to the total number of boiler plants is 16.9% (against 16.594 in 2019), which is 0.4 percentage points more than in the same period of the 2019 year.

**Figure 5.** Structure of energy potential of the agricultural production in the Kyiv region, 2019. Source: Own calculations based on statistics from the State Service of Statistics [53].

As of January 1, 2021, 378 boiler stations for communal purposes were converted to alternative fuels, which is 23 units more than in the same period in the previous year. The number of boiler plants producing energy from installations converted to alternative fuel is constantly increasing and is 27.3% now against 26.7% for the same period in 2019. There is a positive trend in implementing measures to replace natural gas consumption [55].

Referring to one of the best practices of usage of renewable energy could be mentioned company "UMK" in the Zguriv district of the Kyiv region, which implemented the biogas project of the "Ukrainian Dairy Company" with a capacity of 1 MW, which processes manure from 4000 cows and corn silage. The energy produced is enough for a dairy farm and the village of Velikiy Krupil.

Another example of the use of alternative energy sources is a large biogas plant located in the village of Rokytne, Kyiv region, with a capacity of 2.38 MW. The enterprise's output to the design capacity made it possible to provide energy to about 800 individual households. Furthermore, the project initiator—the group of companies "Silhospproduct"—plans to use the mentioned technologies to construct similar factories [39].

Research on the economic efficiency of production and implementation of granules from agricultural raw materials on the domestic market shows that the average payback period of these projects is 2.8 years for the production of sunflower husk pellets and four years for the production of pellets from grain straw and corn stalks. In addition, the population uses straw fuel briquettes to heat their buildings in solid fuel boilers as a substitute for coal. [56].

#### **5. Discussion and Conclusions**

International studies of the energy security of humanity indicate trends in the increase in the price of energy sources. This issue is particularly tough for Ukraine, as the country depends on oil supplies from abroad. The civilian population and producers in various areas of the economy are sensitive to price fluctuations. The fuel shortage endangers the operation of vehicles, machines, and equipment involved in the production. National authors Geletukha and Zheliezna [39], in their Roadmap for Bioenergy Development in Ukraine, until 2050, have forecasted the growth of renewable energy generation and its implications. While the authors of the current work can highly relate to the trends for the next two to three decades described in the referenced article, it is doubtful that it would be possible to achieve the complete transition to renewables in energy generation by 2050. While it is a welcomed scenario, the current situation triggered by the Russian war against Ukraine will definitely set back the development of Ukraine, either economic or agricultural development, as well as development in energy transformation. Geletukha and Zheliezna [39] assumed the consumption of biomass for energy production in 2050 at 20 Mtoe/year, ehich seems to be quite substantiated and relevant to the expected share of renewables (63%) in the total primary energy supply in the same year. The achievement of the targets defined in the abovementioned roadmap requires numerous legislative improvements in Ukraine and considers the needed investments to neutralize the harmful effects of the Russian aggression and accompanied damages.

Modelling results based on the TIMES-Ukraine energy system model [57] prove the need to develop and implement the national strategy to increase energy generation from biomass. The highly valuable contribution proposed by the referenced authors includes the analysis of the current policy environment in the context of future biomass development and concluded with a set of policy recommendations for utilization of the biomass potential in Ukraine. However, as Kaletnik and Larina [17,58] point out, there are numerous issues hindering bioenergy development at the level of the legislative framework; methodological approaches to the economic, environmental, and social efficiency of production; and the use of biological types of energy. The Kyiv region has all the necessary conditions for biofuel production regarding available land resources and plant potential. Already today, the potential in the region of biomass, which is suitable for the cost-effective production of liquid biofuels (bioethanol and biodiesel), gives grounds to argue about the prospects of this area. According to our calculations (Figure 6), the energy from biomass produced in the Kyiv region can annually replace 43.3% of fossil fuels.

**Figure 6.** The total amount of fuel used in the Kyiv region (thousand toe). Source: own calculations based on statistics from [52].

It can be assumed that covering more than 40% of energy needs with locally produced biomass would represent considerable progress in the energy transformation of the region. However, this requires investments, which must be assessed regarding their profitability, energy security, and state security.

The findings of the current article support the abovementioned findings and show the urgency to implement legislative support for renewable energy generation, in particular forming a transparent and understandable regulatory environment for investments in bioenergy projects. These must be verified against the current conditions due to numerous changes in the local environment due to Russian atrocities and inflicted material and human damages on Ukrainian land. Approaches must be taken to intensify the restoration of the local economic infrastructure and farm property. Transport and energy infrastructure are of the utmost importance to ensure local development and the possibility of further improvements.

**Author Contributions:** Conceptualization, A.W., N.G., L.S., P.S. and Z.T.; methodology, N.G., L.S., Z.T. and P.S.; validation, A.W., P.S. and V.K.; formal analysis, N.G., L.S. and Z.T.; investigation, P.S., N.G., L.S. and Z.T.; resources, N.G., L.S., Z.T. and V.K.; data curation, N.G., L.S., Z.T., P.S. and V.K.; writing—original draft preparation, A.W., P.S., V.K., N.G., L.S. and Z.T.; writing—review and editing, A.W., P.S., V.K. and K.P.; visualization, N.G. and K.P.; supervision, A.W. and P.S.; project administration, A.W.; funding acquisition, A.W. and P.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded in part by National Science Centre, Poland 2021/43/B/HS4/02367. For the purpose of Open Access, the author has applied a CC-BY public copyright licence to any Author Accepted Manuscript (AAM) version arising from this submission.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


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