*Article* **Environmental and Economic Assessment of Castor Oil Supply Chain: A Case Study**

#### **Luigi Pari, Alessandro Suardi \*, Walter Stefanoni, Francesco Latterini and Nadia Palmieri**

Consiglio per la Ricerca in Agricoltura e l'analisi dell'Economia Agraria (CREA)—Centro di Ricerca Ingegneria e Trasformazioni Agroalimentari, Via della Pascolare 16, Monterotondo, 00015 Rome, Italy; luigi.pari@crea.gov.it (L.P.); walter.stefanoni@crea.gov.it (W.S.); francesco.latterini@crea.gov.it (F.L.); nadia.palmieri@crea.gov.it (N.P.)

**\*** Correspondence: alessandro.suardi@crea.gov.it; Tel.: +39-06-9067-5248

Received: 30 June 2020; Accepted: 5 August 2020; Published: 6 August 2020

**Abstract:** Among the species currently cultivated for industrial vegetable oil production, castor could be a good candidate for future investments due to the good resistance to pests, tolerance to drought, and suitability for marginal lands cultivation. In addition, the production of castor oil from Ricinus generates a large quantity of press cake, husks, and crop residues that, in a framework of bioeconomy, could be used as by-products for different purposes. Using a case study approach, the work presents results of the environmental impact assessment and economic feasibility of the production of castor oil from two different castor hybrids comparing four by-products management scenarios and two harvesting systems (manual vs. mechanical). Castor hybrid C-856 harvested manually and that involved only the soil incorporation of press cake obtained by the oil extraction resulted as the most sustainable. The hybrid C-1030 resulted as more profitable than C-856 when harvested with the combine harvester. The ratio between gross margin and GWP emissions was applied to calculate the economic performance (gross margin) per unit of environmental burden. Findings showed that Sc1B scenario in case of C-856 cultivar hybrid had a better ratio between economic performance and greenhouse gas (GHG) emitted into the atmosphere (€3.75 per kg CO2eq).

**Keywords:** bioeconomy; life cycle assessment; life cycle costing; *Ricinus communis*, L.; castor oil; harvesting; by-product; residue management

#### **1. Introduction**

The world's population is estimated to exceed 9 billion people by 2050 according to FAO (2009). Thus, increasing in food and energy demand worldwide cannot be avoided: projections show that the overall food production is expected to rise by 70% [1] while the global demand for energy will increase by more than a quarter to 2040 [2]. Bioenergy production primarily aims at the greenhouse gas (GHG) reduction and achieving such a goal may lead to indirect land use change. Competition for land use among food and non-food crops is a serious issue that European Commission has been addressing for decades, and more stringent policy measures regarding sustainable production of food and energy are on the Agenda. On 1 January 2021 the proposed new directive RED II will enter into force, setting the new thresholds for minimum renewable energy share [3]. Investments on biofuel production from non-food feedstock are largely promoted by UE. New policy measures aim to achieve a 27% renewable energy share consumed by the electricity, heating and cooling, and transportation sectors by 2030 [3]. The adoption of energy crops could generate benefits from the reduction of fossil energy dependence, improvement of rural economies, and the achievement of environmental goals [4]. Biodiesel production from vegetable oils is feasible and widely accepted as an alternative strategy to meet these goals: It has similar properties to oil-derived diesel and, furthermore, it produces lower sulfur emission. Among the species currently cultivated for industrial vegetable oil production, castor could be a good candidate

for future investments due to the good resistance to pests, tolerance to drought, and suitability for marginal lands cultivation [5]. According to FAO, in 2017, almost 1.8 million tons of castor seed had been produced worldwide, and Europe is the main user [6]. Furthermore, according to industry executives, the worldwide castor oil market is growing: The global castor oil market was \$1180 million in 2018 and is expected to reach \$1470 million by the end of 2025, growing at a compound annual growth rate (CAGR) of 2.8 percent between 2019 and 2025, according to international reports [7]. The price of castor oil in the beginning of 2019 in the international market reached 1600 dollars per ton compared with 1300 dollars per ton of 2018 [8].

In addition, the production of castor oil from Ricinus generates a large quantity of press cakes, husks, and crop residues [9] that, in a framework of bioeconomy, could be used as by-products for different purposes. In this framework, the European Project MAGIC (Marginal lands for Growing Industrial Crops—Grant Agreement number: 727698-MAGIC-H2020-RUR-2016-2017/H2020-RUR-2016-2) aims towards the development of resource-efficient and economically profitable industrial crops to be grown on marginal land. Among industrial crops considered in the Project, there is *Ricinus communis*, L. (castor) that is cultivated for its seed oil, which is employed extensively in medicine, pharmaceuticals, and biorefineries [10]. Castor is a vigorous fast-growing herbaceous plant native to tropical Africa [11,12] which is tolerant to salinity and drought stresses, with additional benefits of providing a multi-purpose oilseed production [13]. In the world, the most productive country is India (more than 80% of the worldwide production) along with Mozambique, China, Brazil, Myanmar, Ethiopia, Paraguay, and Vietnam. These are all developing countries that benefit from low labor costs, and the economic impact of the harvesting phase is thus sustainable. The lack of possibility to harvest the seeds mechanically is dictated by a high amount of aboveground biomass produced by wild cultivars that cannot be processed by common combine harvesters. In fact, clogging may occur in the case of a high quantity of aerial biomass production, and high seed losses. In order to solve this problem, breeders around the world are struggling to produce hybrids of castor exhibiting high productivity but shorter in height and with homogeneous ripening of the capsules.

To our knowledge, limited studies have been dedicated to the environmental and economic sustainability of castor [14,15]. Some studies are focused on the sustainability assessment of the residue biomass utilization [16] or biodiesel production [17] without investigating in detail the impact of the various castor agricultural stages and different residue management. In particular, a comparison the of the environmental sustainability between different castor hybrids, harvesting methods, and by-products management have not been presented in the literature. Using a case study approach [18,19], the work aimed to present results concerning the estimation of the environmental impacts caused by two different castor hybrids harvested both manually and mechanically (manual vs. mechanical harvestings). Both hybrids had similar seed yields, even though hybrid C-856 is shorter than hybrid C-1030. The latter reported a higher amount of epigeal biomass. Various scenarios of on-farm by-products managements were analyzed. Starting by the same approach, the study carried out an economic assessment to identify the most advantageous scenario for each castor variety and residue management.

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

#### *2.1. Study Sites*

The study area is located in Geaca Municipality, Cluj District (Romania). Cluj District lies in the northwestern half of the country, between parallels 47◦28' in North and 46◦24' in South, meridians 23◦39' in west and 24◦13' in east, respectively. It is located in the contact zone of three representative natural units: Apuseni Mountains, Somes, Plateau, and Transylvanian Plain. Cluj District is the 12th largest in the country and accounts for almost 3% of Romania's area. It is bordered to the northeast by Maramures, and Bistrit,a-Năsăud counties, to the east by Mures, District, to the south by Alba District, and to the west by Bihor and Sălaj counties.

The trials were carried out on the 8th and 9th of October 2019 in two different experimental fields where castor was harvested (Figure 1).

**Figure 1.** Study area and experimental field location (Geaca Municipality, Cluj District, Romania).

Main features of the experimental fields are given in Table 1. Data were taken both from GIS analysis and from field relieves with clinometer.

As highlighted in Table 1, all fields have southern exposition and the prevalent altitude of 313 m a.s.l. was recorded in Field 2 while the maximum slope was recorded in Field 1. However, both fields can be considered flat terrains. The surface of the field 2 was 0.27 ha higher than Field 1. A view of experimental fields positioning on Sentinel-2 image dated 3 September 2019 is given in Figure 2.

**Figure 2.** Experimental fields positioning. Base map Google Satellite Images dated 3 September 2019.


**Table 1.** Main features of the experimental fields for castor harvesting.

#### *2.2. Crop Characteristics and Management of the by-Products*

The main data of two dwarf hybrids of *Ricinus communis* (C-856 and C-1030) collected during the trials are reported in Table 2. Plants were cultivated in Romania, and seeds were provided to local farmer (Ecoricinus—National association of Ricinus growers) by the Israelian company KAIIMA.

**Table 2.** Primary data: Two castor hybrids. Pre-harvest data collection: Height of the plants, aerial biomass produced, and Harvest Index.


Note: Common letters within columns denote the absence of significant difference (*p* < 0.05).

The dwarf hybrids tested were two of the various chosen by the association Ecoricinus to evaluate their behavior and productivity in Romania. Although hybrid C-856 has already been analyzed in productive and morphological terms by Alexopoulou et al. [6] in Greece and Italy, hybrid C-1030 has never been described in the literature and in the present study, it has been analyzed only to assess its productivity and the amount of epigeal biomass available for the LCA study.

Despite the significant difference found in height, straw production, and the harvest index (HI) between the two hybrids, in both cases, the aboveground biomass produced was lower than the quantity produced by wild varieties commonly cultivated in Romania (data not shown). Therefore, more suitable for mechanical harvesting. The farmer reported that fertilization and plowing took place in 2018 between week 47 and 48, while harrowing and sowing occurred in week 23 and 24 2019 at the depth of 8–10 cm with the sowing density of 3.6 seeds m−2. Mature cow manure was applied at the quantity of 6 Mg ha−<sup>1</sup> and no irrigation was provided. No chemicals were used for both weed control and desiccation of leaves.

On the basis of farmer's survey, two scenarios for each castor variety with a different mix of by-products management were considered (Table 3).



In the case of manual harvesting (Sc1A and Sc1B), the castor fruit is harvested as whole, and the separation of the spiny capsules from the seeds takes place on the farm. According to Parascanu (2017), castor husk might be deemed as the best candidate for the combustion process due to its high heat release [20]. Therefore, in the Sc1A and Sc1B scenarios, the sale of spiny capsules has been assumed at a

market price of crushed olive stones due to similar lower heating value (LHV) that results in 16.48 [20] and16.50 MJ/kg [21], respectively.

In the scenarios Sc2A and Sc2B involving castor mechanical harvesting, castor husk has always been considered incorporated into the soil because it was discharged on the ground by the combine harvester as residue and not collected. Castor straw is a residue with an LHV of 17.68 MJ/kg and an ash content of 1.70 wt% [20]. For this reason, both manual and mechanical harvesting scenarios have been considered, both sold as solid biofuel (Sc1B and Sc2B) and incorporated into the soil (Sc1A and Sc2A). According to the farmer, press cake that resulted during the oil extraction phase is used as fertilizer and for this reason was always considered incorporated into the soil. Castor oil is the main product in the supply chain, and it has always been considered as sold.

#### *2.3. Data Sampling and Measurements*

Pre-harvest tests were conducted directly in the field. Four plots of 1.5m x 2m each were randomly selected within the two experimental fields in order to measure the growth of the plants and estimate the aboveground biomass produced. In each plot, plants were counted and cut at the collect level, then brought outside the field for height measurements as well as straw and capsules fresh weight determination. The height of the plant was taken by measuring the distance between the collect and the tip of the longest raceme. Samples of straw and the total capsules collected in each plot were put in sealed bags and brought to the laboratory for dry weight determination. In the laboratory, capsules were separated manually from the seeds. Thus, seeds were weighed for seed yield estimation. Simultaneously, samples of straw and empty capsules (husks) were dried at constant temperature of 105 ◦C in a ventilated oven until constant weight was reached (EN ISO 18134-2:2015). Then, the dry matter and humidity content were calculated. All data were subjected to the analysis of variance (ANOVA) to separate statistically different means (*P* < 0.05).

#### *2.4. Life Cycle Assessment of Castor Oil Supply Chain*

An environmental impact analysis of castor oil production was carried out using the life cycle assessment methodology (LCA) according to UNI EN ISO 14040: 2006 [22] and UNI EN ISO 14044: 2006 [23], by means an attributional approach [24–27], including the following statements: (a) Goal definition and scoping: Defining the goals of the study, the functional units, the boundaries of the system, and the required data; (b) life cycle inventory: data collection; (c) life cycle impact assessment: Estimation of the potential environmental impacts; (d) life cycle interpretation and improvement: Final step where the risks are evaluated and checked to draw conclusions.

#### 2.4.1. Goal Definition and Scoping

The considered system is defined by all the agricultural processes that occurred during the *Ricinus communis* growing phase and subsequent oil extraction phase carried out at farm level.

The boundary of the system (Figure 3) is given by the life cycle stages of castor to be included in the LCA. Cultivation phases and extraction phase of oil were studied from cradle-to-farm gate.

The functional unit represents the reference unit used to quantify all inputs and outputs from the boundaries of the system. It is defined as 1 Mg of castor oil produced by the farm.

Firstly, the environmental impact of each single hybrid cultivar was separately analyzed for each scenario; then, each scenario was assessed to identify the best hybrid cultivar.

Allocation describes how environmental impacts are shared between the main product and co-products along the supply chain [28]. Castor oil is the main product, while crop residues (castor husks and straw) and press cakes are considered co-products [9]. In an LCA study, the co-product handling is a crucial issue because it could impact on the final results [29]. Agricultural products are particularly sensitive to allocation methods because of the different share that their co-products can have. In our case, an economic allocation method that takes into account market prices and mass of product and by-products per each scenario was used [30] (Table 4). Castor market prices are not easy to be find, especially for castor co-products that do not have a market. For this reason, the selling price of castor seed was considered to be 600 euros per Mg, while the price of castor oil for cosmetic purposes was 30 euros per liter according to informal local market. As described above, in the absence of a market, husk and straw prices for energy purposes have been assimilated to solid biomass with similar characteristics (olive stones and wheat straw) used for energy purposes and with known market prices. In fact, following information from the informal local market as happen in other studies [31], the price of husks for energy purposes was 180 euros per Mg, while the price of straw was considered 55 euros per Mg. The prices used are those indicated by the Ricinum producers National Association of Romania (Ecoricinus Productie Comert Srl, Cluj-Napoca, 10, Fanatelor st. jud, Cluj, Romania). Even if the press cake corresponds to an important amount of biomass, due to its returns to the soil as fertilizer internally at the farm, according to the economic allocation type used and due to an absence of a market and a market price, the impact generated by the press cake was assumed to be very low (0.07%) with a minimum price of 0.1 € per Mg of by-product.

**Figure 3.** System boundary.



Source: CREA elaboration.

#### 2.4.2. Life Cycle Inventory Analysis

Data resulting from a survey carried out by field technicians were utilized for the life cycle inventory analysis. The Simapro code database 8.0.2 (Prè Consultants, Amersfoort, The Netherlands) was used for data not identifiable by survey.

The primary data were relative to the technical characteristics of the tractors and agricultural equipment utilized and diesel consumption (Table 5). Regarding the hypothesis of mechanical harvesting, all data for the costs, performance, and specifications of a conventional combine harvester were derived from personal communication and literature. Moreover, the primary data were relative to different castor varieties.


**Table 5.** Technical characteristics of the machineries, diesel consumption, and agricultural phases.

Source: CREA elaboration on survey data. \*Scenario 1. \*\* Scenario 2.

The secondary data referred to the emission generated by the machines during different agricultural phases and from fertilizers.

Emissions in air, soil, and underground water (leaching) due to manure storage, as well as by-products and manure incorporation into the soil per each scenario, were calculated using the model proposed by [32] and values of the references reported in Table 6.

**Table 6.** Secondary data: Source of the emissions considered in the study for storage and soil incorporation of the manure, and by-products (press cake, straw, and husk according to the scenario—Table 2).


The exhaust gases emissions from agricultural tractors and combine harvester were calculated using the standard emission factors for diesel engines reported by Directive 2004/26/EC for carbonnitrogen oxides (g NOx ha−1), hydrocarbons (g HC ha−1), monoxide (g CO ha−1), and particulate matter (g PM ha<sup>−</sup>1), according to the method reported by [39]. The amount of released carbon dioxide (kg CO2 ha<sup>−</sup>1) was calculated by multiplying the fuel consumption (kg ha−1) by an air emission factor of 2.6 (kg CO2 emitted per kg of diesel fuel consumed), according to [40,41].

#### 2.4.3. Land Use Change (LUC)

The direct and indirect land use change (LUC) associated with crop production can produce changes in the carbon from soil and vegetation [42]. Castor oil can be in the form of herbaceous or arborescent plant, annual or perennial, depending on the climatic conditions of the region. In the present study, castor oil is cultivated as annual oil crop in cropland that had not undergone any land-use conversion for a period of more than 20 years [34]. Following the indications of the Intergovernmental Panel on Climate [34] there is no net accumulation of biomass carbon stocks for annual crops. On the other hand, emission from soil carbon mineralization per each scenario has been taken into consideration because there are changes in the management activities on croplands, and in particular, in the amount of biomass that has been considered incorporated into the soil according to the different scenario considered (Table 2). Even if the soil's organic carbon was considered in the steady state, and the farm analyzed employed crop rotations, different crop residue management considered in the study and the amount of GHG emitted during the different scenario were calculated according to the following formula:

$$\text{GHG}\_{\text{res}} = \sum\_{i=1}^{3} \left( \text{Res}\_{i} \times \text{C}\_{\text{res}\_{i}} \times \text{C}\_{\text{min}\_{i}} \times aw\_{\text{CO}\_{2}} \right) \tag{1}$$

where

*GHGres* = Greenhouse gases emissions from soil incorporation of residue "*i*" per scenario (Mg CO2 ha<sup>−</sup>1) *Res*<sup>i</sup> = Amount of residue "*i*" incorporated into the soil (Mg ha<sup>−</sup>1) *Cresi* = Organic carbon content in the residues "*i*" (%) [6] *Cmini* = Organic carsbon in the residues "*i*" mineralized in soil (%) [38] *aw*CO2 = atomic weight of carbon dioxide equal to 44/12

#### 2.4.4. Life Cycle Impact Assessment

The environmental impact of 1 Mg of castor oil was based on GHG emissions. The carbon footprint was defined as the sum of all GHGs emitted within the system boundary and expressed in CO2 equivalent applying the IPCC 2007 method (100-year life span).

A parallel economic assessment is integrated with LCA also using a life cycle perspective that covers all activities in the supply chain up to the farm gate. The economic sustainability is critical because when it comes to assessing the different products and by-products management, the attention of farmers does not fall solely on environmental impacts, but also (and mainly) on economic aspects. For this reason, an economic assessment was carried out.

#### *2.5. Economic Assessment*

The study followed the steps in LCA identified in the relevant international standard [22,23] with the corresponding steps in life cycle costing (LCC) introduced in parallel. Life cycle costing (LCC) is a methodology that. aimed to assess the costs across the entire life cycle of a product, process, or service [43] concentrating on the economic cost at each stage [44]. A conventional cradle-to-gate LCC was applied here and includes the assessment of all costs associated with the life cycle of the castor-oil cultivation specific to each scenario. In particular, the LCC assessment is focused on internal costs (value of goods and services consumed, including raw materials, services, other operating expenses, and labor costs). It is important to underline that the contractors provide all phases of the preparation of the field up to sowing (bottom fertilization, ploughing, harrowing, and sowing). Everything afterwards (weed control and harvesting) is performed by the owners of the field for Sc1A and Sc1B. In Sc2A and Sc2B, all agricultural phases are in subcontractor account. Later, to evaluate the gross margin of farm, the revenues for each product (multiplying between prices and quantity of products) are calculated. Gross margin refers to the difference between revenue from crop sales and the variable costs related to the agricultural activities [44] and it is a profitability indicator of a farm. All data (Table 7) come from the budget (year 2018) of the farm studied.


**Table 7.** Economic data expressed in €/ha per year.

Source: CREA elaboration.

#### **3. Results and Discussions**

According to the literature, castor yield can change appreciably with genotype [45]. Arnaud (1990) observed a seed yield from 2000 to 2620 kg ha−<sup>1</sup> in France [46], while Anastasi (2015) reported a yield between 1790 to 4750 kg ha−<sup>1</sup> in Italy [47]. In the present research, the genotypes of castor grown showed similar productions of 2800 and 2900 kg ha−<sup>1</sup> for C-856 and C-1030, respectively. However, the C-1030 hybrid, which is higher than C-856 and has a significantly higher HI (Table 2), produced 85% more straw than C-856, with the same inputs used.

Alexopoulou et al. [6], from the comparison of various castor hybrids planted in Greece and Italy, found an average amount of stems and leaves of 1.08 Mgdm ha<sup>−</sup>1, and the hybrid C-856, that resulted as 133 cm tall (79% taller than in our study) in Greece (Aliartos area, Greece in 2014), allowed for obtaining 1.13 Mgdm ha−<sup>1</sup> of stems and leaves against 0.87 Mg ha−<sup>1</sup> obtained in the present study. In the same study, the C-856 hybrid produced a straw quantity of 0.585 Mg ha<sup>−</sup>1, much more similar to that obtained in this study in 2012 in Greece (Aliartos area, Greece in 2014) [6]. In general, Alexopoulou et al. [6] highlighted that C-856 resulted as the best-performing hybrid in Italy while in Greece, its yields were quite low, probably related to the high percentage of immature racemes (60%) at harvest. This suggests the influence of the climate and crop management on the phenotype expression of this hybrid. To the best of our knowledge, there is no information in the literature about the C-1030 hybrid.

The type of harvesting represents a critical phase that can also have a significant influence on the amount of product that can be collected per unit area. Mechanized harvesting allows for collecting about 3 t/h of castor oil seeds (considering a harvesting rate between 0.75 and 1.5 hectares per hour) ready to be pressed. On the other hand, according to farmers, manual harvesting shows extremely low losses <5%. On the contrary, castor mechanized harvesting needs to be improved due to the major losses, which can be up to 50% as evidenced by [48]. So far, only one machine manufacturer has started the first harvesting tests using a specific castor header, which would be able to reduce losses to 5% [48], and Zhao et al. [49] reported the possibility to harvest the capsules using a vibrating system instead of a cutting bar [49]. In the present study, losses were not considered given the uncertainty of the data to be scientifically verified in specific tests.

#### *3.1. LCA*

The impact analysis allowed for identifying the processes that had higher impacts on the environment.

What emerged from the analysis was that fertilization was the agricultural phase with the most impact. This result is common to various studies [50–56]. In the present study, for all cultivar hybrids and scenarios, the environmental impacts of fertilization phase were due to emissions of methane (CH4), dinitrogen monoxide (N2O), and carbon dioxide (CO2) from manure management and its incorporation into the soil. In fact, fertilization emitted 74 to 89% of the GHG of the castor oil production. The LCA study of biodiesel production from rapeseed published by Malça et al. [57] reported that the cultivation stage impacted 66 to 79% and fertilization was the main cause of GHG emissions [57]. According to our results, the higher GHG emissions were mainly due to the characteristics, and the direct and indirect emissions were generated by manure itself. It should be highlighted that, as suggested by Aguilera et al. [58], organic fertilizers applied at similar N rates to synthetic fertilizers generally make smaller contributions to the leached NO3 <sup>−</sup> pool, and can mitigate N2O emissions [58]. The different by-product management also influenced the indirect emissions of GHG due to their degradations during soil incorporation.

In the case of castor oil produced by both C-856 and C-1030 cultivar hybrids, as expected, the manual harvesting resulted as more sustainable (Sc1A and Sc1B), and Sc1B scenario was always the least impactful, followed by scenarios 1A and 2B (Figures 4 and 5).

**Figure 4.** Carbon footprint of 1 Mg of castor oil hybrid C-856 for each scenario ((Sc1 = scenario 1; Sc2 = scenario 2).

**Figure 5.** Carbon footprint of 1 Mg of castor oil hybrid C-1030 for each scenario (Sc1 = scenario 1; Sc2 = scenario 2).

Moreover, among cultivar hybrids and all scenarios, Sc2A\_C-1030 is more impactful than the other treatments analyzed, while the Sc1B\_C-856 is less burdensome than others. These results were due to both different combinations of on-farm by-products (castor press cake incorporation into the soil in case of 1B\_C-856, and castor press cake, straw and husks incorporation into the soil in case of 2A\_C-1030) and yields (2.8 Mg per ha in case of C-856 vs. 2.9 Mg per ha in case of C-1030). In general, the incorporation of by-products in the soil at farm level has resulted in higher GHG emissions than their sale. For this reason, the highest impact observed in the mechanized harvesting treatments (Sc2A and Sc2B) is largely due to the non-collection of husks that are left in the field by the combine and then buried (unlike manual harvesting where husks are separated from the seeds on the farm and then sold as solid fuel). Obviously, the study focused on the impacts related to the production of castor oil on the farm, not considering the whole process downstream of the supply chain and the related impacts that could completely reverse the results obtained.

The life cycle of scenario 1B, in which manual harvesting was assumed (less burdensome in the case of hybrid C-856, slightly less productive, and with less press cake), and with the incorporation of the pressed cake alone and the sale of the other by-products, resulted in the emission of 8.14 Mg CO2eq per Mg of castor oil (8.14 kg CO2eq per kg of castor oil extracted). On the other hand, the life cycle of scenario 2A\_C-1030, in which mechanized harvesting with combine harvesters and the incorporation of straw, husks, and press cakes was assumed, resulted in the emission of 18.9 Mg CO2eq per Mg of castor oil produced (18.9 kg CO2eq per kg of castor oil extracted).

Although, in Sc1A and Sc1B scenarios, there is the de-hulling phase that there is not in Sc2A and Sc2B, this has a very small impact always <8% (on average 0.698 Mg CO2eq Mg−<sup>1</sup> of castor oil produced) of the total CO2 emissions. The oil extraction impacted less than 5% of the total CO2 emitted (on average 0.412 Mg CO2eq Mg−<sup>1</sup> of castor oil). Sanz Requena (2010) reported that for each ton of crude sunflower, rapeseed, and soybean oil extracted, an average of 2.2 Mg of CO2 was emitted, but it should be highlighted that after the mechanical extraction, a treatment with a solvent (hexane) was included [54].

Spinelli (2012) reported a total emission of 13.7 Mg CO2eq Mg<sup>−</sup><sup>1</sup> of sunflower oil produced [59]. However, according to the study and the allocation used, the emissions became 4.52 Mg CO2eq Mg<sup>−</sup><sup>1</sup> of sunflower oil and 9.18 Mg CO2eq Mg−<sup>1</sup> of sunflower cake produced. The lack of allocation of a higher share of emissions from the press cake makes castor oil production inevitably more impactful in GHG emitted than other vegetable oils, although the variety C-856 with manual harvesting have relatively low and promising overall emissions.

#### *3.2. Economic Assessment*

The economic gross margin is related mainly to the yield level (product and by-products) and to the cost of inputs for each scenario and cultivar hybrid. As far as the yield is concerned, the values for each farm and crop have been previously discussed and the data are reported in Table 8, showing higher yields per ha for C-1030 than for C-856 crops. For these reasons, the C-1030 cultivar shows lower total costs per Mg cultivated than C-856 ones (Table 8). Moreover, for both cultivar hybrids, the total costs of manual harvesting scenario are higher than mechanical harvesting scenario ones. This finding was due to labor costs in harvesting phase. In fact, in case of the manual harvesting scenario, five workers are required to harvest castor seed, contributing 32% to the total costs; while in case of mechanical scenario one worker (with machinery) is required contributing just 13% to the total costs. The impact that manual harvesting has on costs can be equated to that reported by Silalertruksa (2012) in Thailand, where manual harvesting accounts for 22% of total costs in the palm oil sector [60].


**Table 8.** Economic grossmargin for each scenario expressedin€/FU (1 Mg of castor oil)—(Sc1 = scenario 1; Sc2 = scenario 2).

Source: CREA elaboration on budget data (year 2018). \* For each agricultural phase are included the internal costs (i.e., value of goods and services consumed, including raw materials, services, other operating expenses and labor costs).

Table 9 shows that the 2B\_C-1030 scenario had higher gross margin than other scenarios; while the 1A\_C-856 scenario had the lowest gross margin.

**Table 9.** Gross margin and carbon footprint for each scenario, expressed in €/FU (1 Mg of castor oil)—(Sc1 = scenario 1; Sc2 = scenario 2).


Source: CREA elaboration on both budget data (year 2018) and environmental findings.

In addition, the ratio between gross margin and GWP emissions was applied to calculate the economic performance (gross margin) per unit of environmental burden (Table 9). The ratio is based on data from both environmental and economic accounting systems. The higher the ratio value, the higher the economic performance per unit of GWP emitted.

Findings showed that scenario 1B in the case of C-856 cultivar hybrid had a better ratio between economic performance and GHG emitted into the atmosphere (€3.75 per kg CO2eq); while the 2A\_C-1030 scenario showed the worst ratio between economic and environmental performances (€1.62 per kg CO2-eq) confirming the environmental results. These results were due to different combinations of on-farm by-products (see Table 3), different revenues (see Table 8), and yields (see Table 2).

#### **4. Conclusions**

There has been a critical increment in interest for sustainable and biodegradable items so as to diminish reliance on petrochemicals. This is one of the essential elements which is driving the growth of the worldwide castor oil market. The research focused on the evaluation of the environmental and economic sustainability of two different castor hybrids (C-856 and C-1030) comparing manual and mechanical harvesting methods, and by-product management.

Comparing all the proposed scenarios, the cultivation of the manually harvested castor hybrid C-856 and the by-product management that involved only the soil incorporation of press cake obtained by the oil extraction resulted as the most sustainable. On the other hand, the mechanized harvesting of hybrid C-1030, which involved the incorporation of all the by-products of the cultivation of castor and production of castor oil (husk, straw, and press cake) showed the highest CO2 emissions per Mg of castor oil (+132%). It is therefore clear how, with the same inputs used, the castor-oil cultivation method affects the management of by-products and how, while residues are a source of organic matter for the soil, they cause greenhouse gas emissions during the degradation process in the soil.

From an economic point of view, a difference in Gross Margin (€/Mg) between the hybrids used was only evident when comparing the scenarios in which mechanized harvesting was used, i.e., C-856\_Sc2A vs. C-1030\_Sc2A and C-856\_Sc2B vs. C-1030\_Sc2B, resulting in an increase in Gross Margin of 6 and 7%, respectively, using the hybrid C-1030. The two hybrids when harvested manually did not show appreciable increases in Gross Margin (0.1%). In general, the scenario that produced most Gross Margin was the C-1030\_Sc2B where mechanized harvesting of the plants, the incorporation of husk and press cake, and the sale of castor oil and straw were carried out.

In the end, to determine the most economically and environmentally convenient scenario, the ratio between gross margin and GWP emissions was applied to calculate the economic performance (gross margin) per unit of environmental burden. Findings showed that scenario Sc1B in the case of C-856 cultivar hybrid had a better ratio between economic performance and GHG emitted into the atmosphere (€3.75 per kg CO2eq); while the Sc2A\_C-1030 scenario showed the worst ratio between economic and environmental performances (€1.62 per kg CO2eq) confirming the environmental results.

Although Sc1B represents a good economic–environmental compromise, including manual harvesting, it clashes both with the need to innovate the castor production chain, and with the costs and availability of labor that may vary over time, affecting the sustainability of the chain, costs, and market prices.

Furthermore, an important aspect that was not considered in the study is the loss of product during harvesting. This is particularly relevant in the case of very high losses that are reflected in the impacts per unit of product. With the implementation of well-functioning mechanized castor harvesting systems, the resulting seed losses will also necessarily have to be considered in future studies.

Moreover, it is important to highlight that the study did not consider the whole process downstream of the castor oil extraction and the related impacts that could completely reverse the results obtained, which should be investigated in future researches.

Ultimately, the lack of official economic data on the market prices of products and by-products, and the difficulty of finding the costs resulting from the various cultivation practices, within the castor production chain, as old as it is, currently undergoing improvement and remodernization, represents a limit to obtaining exhaustive answers on its economic sustainability. For this reason, this research does not have the presumption to provide a definitive answer to the questions related to the environmental and economic sustainability of the castor-oil production chain, which will need further study and analysis as the production methods are refined.

**Author Contributions:** Conceptualization and methodology, A.S., N.P., L.P.; investigation and data curation N.P., A.S., W.S., F.L.; writing—original draft preparation N.P., W.S., F.L., A.S.; writing—review and editing, A.S.; supervision, L.P. and A.S.; funding acquisition, L.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by European Union's Horizon 2020 Magic—Marginal lands for Growing Industrial Crops: Turning a burden into an opportunity project grant number 727698 (http://https://magic-h2020.eu). The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

**Acknowledgments:** Authors thank the ricinum producers National Association of Romania (Ecoricinus Productie Comert Srl, Cluj-Napoca, 10, Fanatelor st. jud, Cluj, Romania) and his team for their valid support and assistance provided during the activities, the field data and data for the economic analysis, as well as Sandu Lazar for his valuable contribution in the field activities.

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

#### **References**


© 2020 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 (http://creativecommons.org/licenses/by/4.0/).

## *Article* **Economic and Environmental Assessment of Two Different Rain Water Harvesting Systems for Agriculture**

**Luigi Pari, Alessandro Suardi, Walter Stefanoni, Francesco Latterini and Nadia Palmieri \***

Consiglio per la Ricerca in Agricoltura e l'analisi dell'Economia Agraria (CREA)—Centro di Ricerca Ingegneria e Trasformazioni Agroalimentari, Via della Pascolare 16, Monterotondo, 00015 Rome, Italy; luigi.pari@crea.gov.it (L.P.); alessandro.suardi@crea.gov.it (A.S.); walter.stefanoni@crea.gov.it (W.S.); francesco.latterini@crea.gov.it (F.L.)

**\*** Correspondence: nadia.palmieri@crea.gov.it; Tel.: +39-069-067-5219

**Abstract:** Increasing aridity and subsequent water scarcity are currently among the major problems of agriculture. Rainwater harvesting could represent a way to tackle this issue, and, as a consequence, scientific research has been more and more focused on such topic. On the other hand, few scientific studies related to economic and environmental assessment of rainwater harvesting systems in agriculture are available. The present study carried out an economic and environmental analysis of two different systems for rainwater harvesting: a typical pond and an innovative flexible water storage system (FWSS). The environmental and economic performance of the systems was compared using the Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) methodologies, referring to a functional unit (FU) of 1 m<sup>3</sup> of storable water. The FWSS showed better environmental end economic performance than the pond system, resulting with both lower environmental impacts (17.04 g per m3 CO2 *vs* 28.2 g per m<sup>3</sup> CO2) and lower costs (16.94 € per m<sup>3</sup> *vs* 20.41 € per m3). Moreover, the pond system was more impactful than the FWSS for all the 17 categories investigated. Therefore, the FWSS can be a suitable solution for water harvesting in agriculture sector, showing interesting features for farmers.

**Keywords:** ecoefficiency; life cycle assessment (LCA); life cycle costing (LCC); run-off; pond; flexible water storage system

#### **1. Introduction**

Water scarcity and water supply are among the major concerns that countries worldwide have been struggling to address during the last decades. Usually, European countries are not arid, but some, like Cyprus, Bulgaria, Belgium, Spain, Malta and Italy, are currently exploiting 20% or more of their long-term water supplies every year. Agriculture is among the main responsible sector for freshwater consumption accounting for the 24% of the abstracted water that can go up to 80% in southern regions [1]. The need to rely on natural fresh water basins or on underground water is further fostered by the effect of climate change on the rainfall pattern in the Mediterranean region, where heavy rainfall events are occurring more frequently and only in a limited period of the year [2]. Farmers struggle to plan field activities, and plants need to be irrigated artificially more often than before. They mainly rely on underground water, but the overexploitation of such resource has detrimental effects on the environment [3]. Public awareness of agriculture impact on the environment is driving the change from conventional farming to organic farming, the latter of which seeks to burden the environment with as little water depletion as possible [4]. Although organic farming also contributes to GHGs reduction, it is not the resolutive strategy to cope with this problem. Interest is growing in arid and semi-arid regions of the planet concerning the possibility of collecting and storing rainwater for urban and agriculture purposes [5].

**Citation:** Pari, L.; Suardi, A.; Stefanoni, W.; Latterini, F.; Palmieri, N. Economic and Environmental Assessment of Two Different Rain Water Harvesting Systems for Agriculture. *Sustainability* **2021**, *13*, 3871. https://doi.org/10.3390/ su13073871

Academic Editor: Hossein Azadi

Received: 10 March 2021 Accepted: 26 March 2021 Published: 31 March 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 present water scarcity leads to a new paradigm in water resource management, and the application of sustainable water supply solutions is essential [6,7]. Some studies [8,9] have catalyzed interest in alternative approaches to ensure water security by applying, for example, rainwater harvesting systems.

Rain water harvesting (RWH) is the process of accumulating incident raindrops on ground surfaces and roofs, with the help of cisterns, tanks, and underground check dams [10]. RWH has been applied for centuries by humankind to meet water supply needs and nowadays can still represent an important practice to improve the efficiency of the use of water in the urban future [5] by reducing household expenditures on water consumption [11] and offering many opportunities for agriculture.

In fact, irrigation of rainfed crops through RWH could represent a good option to increase crop yields due to an improvement in the water productivity [5].

Jiang et al. (2013) highlighted that the rainwater supplementary irrigation could increase crop yield by more than 30% [12]. Furthermore, even if rainfed agriculture in arid and semi-arid areas represents to up to 90% of the total production of cereal of these regions, in many countries, productivity remains low due to the sub-optimal rainfall characteristics, disadvantageous land conditions, and a deficiency in good management of these resources. On the other hand, increasing productivity of rainfed areas could lead to an increase in food security, reduction in irrigation frequency, and improvement in livelihoods and rural conditions. Furthermore, as reported by Ghimire et al. (2017) [13], RWH could reduce "impacts on the environment and human health, stormwater runoff and combined sewer overflows, and economic viability". As observed by various authors, RWH represents a valid system to reduce stormwater runoff, improving water management in an affordable manner [14–16]. Surface runoff is a phenomenon that, at the farm level, is triggered by 10 to 25% of rainwater falling in arid and semi-arid areas, and it can have negative effects on soil erosion and the accumulation of nutrients, chemicals, and sediments into rivers and streams [5]. Storage can be achieved with various types of storage systems that can also differ remarkably in terms of costs and environmental impacts [5].

Nevertheless, the environmental sustainability of different strategies to store rainwater has been seldomly investigated at the farm level; particularly, it has not been taken into account in the decision-making phase which should include this aspect along with the economical and feasibility aspects. Only few studies dealt with the environmental aspect of fresh water storage system, and, if so, they mainly focused on drinkable water [17,18]. Because agriculture is a highly demanding activity in fresh water (more than a simple beverage), much attention is ought to be paid to such aspect. Life Cycle Analysis (LCA) is widely recognized as a standardized method [19,20] that is used to evaluate the potential environmental impacts of products, processes, or services during the entire life cycle. Similar to LCA, Life Cycle Costing (LCC) methodology [21,22] is one of the main tools used to embed economic factors into the assessment of sustainability.

In general, as noted by several authors, irrigation in agriculture also leads to increased environmental impacts [23–26]. Most of the works in the literature focus on the emissions generated by the irrigation phase, focusing mainly on the amount of water resources used or on the energy related to the irrigation phase [23,24], and often without specifically analyzing the infrastructure (irrigation system) used [25,26].

On the other hand, some studies assessed the sustainability of rain water supply systems. Yan et al. (2018) [9] compared the environmental impacts of decentralized and centralized potable water supply, and they found a water-saving efficiency laying between 0.6 and 100%, depending on rainfall. Their results suggested that potable water produced from this decentralized system currently performs poorer than centralized water from an environmental perspective [9]. Other authors [8] performed a comparative LCA for greywater treatment within a circular economy framework and evaluated the environmental impacts of three greywater treatment alternatives (i.e., photocatalysis, photovoltaic solar-driven photocatalysis, and membrane biological reactor). Their results showed that

photovoltaic photocatalysis driven by solar energy is the most sustainable scenario from the environmental point of view [8].

In this scenario, the implementation of a circular economy strategy results in a promising approach [8]. However, LCA studies performed relying on experimental data for the analysis of the environmental impacts of crops irrigated with reclaimed water are still missing [27], although irrigation plays a critical role in boosting crop yield; furthermore, 40% of freshwater global resources are consumed by agricultural production [28].

In particular, to the best of our knowledge, the literature lacks LCA and LCC studies concerning the impact of RWH systems for agricultural purposes, particularly as tool in the decision-making process. In this paper, the authors investigated the environmental and economic impact of a conventional water storage system, as a pond, against an innovative flexible water storage system (FWSS) that could bring about practical advantages to farmers because of its flexibility and the easy-to-move feature. A comparison has been performed via LCA and LCC assessment starting for the hypothesis that 400 m<sup>3</sup> (average commercial pond's volume capacity available on the market) of rainwater can be collected and stored locally for crop irrigation purposes. Furthermore, there are not studies evaluating the ecoefficiency of different rainwater harvesting systems. For this reason, this study fills a knowledge gap in the current literature.

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

Farms usually rely on underground reservoir or on aqueduct or, sometime, on channels that naturally occur outside the field during the winter to pump the water needed for watering plants or cleaning machineries. All those sources are temporary available. Thus, it is important to catch as much water as possible during the fall-winter season and store it for the following dry season.

Water storage in ponds is quite common in farms. Thus, the research focused on the economic and environmental sustainability assessment of two systems for water harvesting and storage: the pond and the flexible water storage system (FWSS) (Figure 1).

**Figure 1.** Schematic view of the pond (**A**) and the FWSS (**B**) meant for agroforestry application. Numbers refer to the main components of both systems: (1) seasonal water stream, (2) loading system (including electric pump, pipes and connections), (3) water storage system, (4) electric pump for water delivery, (5) water usage (e.g., irrigation system).

#### *2.1. Pond*

Ponds represent a common strategy for water storage because they are relatively easy to build and low demanding in maintenance although they exhibit short lifespan of 5–10 years that could represent a limit for the system [29]. Furthermore, there are other drawbacks that usually are not taken into account like the permanent disturbance of the soil, the reduction of the arable surface which reduces the available arable land and other concerns related to water quality and safety. Moreover, in areas with high evaporation potential ponds are not very suitable [30] and need to be covered with shade net [29].

Building a pond implies permanent changes in the soil, particularly the shallower horizons which are more fertile and suitable for cropping. In order to accommodate the assumed 400 m3 of water, authors made the hypothesis of removing an equivalent volume of soil (336.6 m<sup>2</sup> and 1.4 m depth) by using a 90-kW excavator. According to the estimations, digging requires 20.5 h and 328.1 l of fuel (data not shown). Consequently, a double layer 1350 g m−<sup>2</sup> PVC is applied. A detailed list of the components is shown in Table 1.

**Table 1.** Summary table of components involved in the loading, storing and water distribution in the pond system.


The Flexible Water Storage System

The flexible water storage system (FWSS) is an alternative solution to ponds. Interestingly, it can be easily folded and moved elsewhere according to the domestic needs of the farm; the installation does not require a concrete base, just a little slope is desired to ease the outflow of the water, which is ensured by a secondary electric pump, though. Contrary to the pond, water is not directly exposed to sunlight; thus microbial activities are not promoted and higher water quality is expected [31].

The Flexible Water Storage System is made of polyvinyl chloride (PVC) 930 g m−<sup>2</sup> thick and equipped with inlet and outlet pipe connections. FWSSs find many applications in agricultural sector for storing non-potable water, wastewater or sewage water produced by livestock. According to Rigamonti et al. (2019) the service life of a rain water harvesting system based on a polyethylene storage tank is 50 years [32]. Loading is performed by an electric water pump that pumps the water via a filter from a near seasonal water stream directly into the FWSS. When the tank reaches its maximum capacity, the blow-off valve opens preventing over-pressure. The water can be stored as long as it is needed without leak of water or smell. During the dry season the water can be used for irrigation to reduce the exploitation of the underground water. Components of the FWSS are listed in Table 2.


**Table 2.** Summary table of components involved in the loading, storing and water distribution in the FWSS.

#### *2.2. LCA and LCC Methods*

The environmental impact analysis was carried out using the life cycle assessment methodology (LCA) according to UNI EN ISO 14040:2006 [19] and UNI EN ISO 14044:2006 [20], including the following statements: (a) Goal definition and scoping; (b) life cycle inventory; (c) life cycle impact assessment; (d) life cycle interpretation and improvement. Moreover, the study followed the steps in LCA with the corresponding steps in life cycle costing (LCC) introduced in parallel. Life cycle costing (LCC) is a methodology that aimed to assess the costs across the entire life cycle of a product [33] focusing on the cost at each stage [34].

2.2.1. Boundary of the System for the Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) Analysis

The considered system (for LCA and LCC analysis) is defined by all the processes that occurred during the production and installation phases of two different water tanks (Figure 1). The functional unit is 1 m<sup>3</sup> of storable water of the studied RWH systems. It represents the reference unit used to quantify all inputs and outputs from the studied systems [9].

#### 2.2.2. Life Cycle Inventory Analysis

Primary data of the materials used for the construction of the pond were obtained through interviews to local enterprises, which main activity consists of ponds' construction or, in general, digging jobs. For the FWSS, the primary data was calculated according to [35,36]. Secondary data were obtained by Simapro code database 8.0.2 (Prè Consultants, Amersfoort, The Netherlands) (Tables 3 and 4).


**Table 3.** Technical data of the pond.

Source: data collected from either datasheet or direct weighting of spares.

#### **Table 4.** Technical data of the FWSS.


Source: collected from either datasheet or direct weighting of spares.

#### 2.2.3. Life Cycle Impact Assessment

Environmental impacts per m3 of storable water was assessed using both ReCiPe2008 [37] and GWP100 methods. In particular, ReCiPe 2008 method includes categories of environmental impact and environmental damage, i.e., at the midpoint and endpoint level. Initially, the inventory data were associated to the midpoint level using factors of characterizations. Lately, they have been converted and clustered into the endpoint level considering three damage categories (i.e., HH, EC, RE damage categories) and by using weighting factors. It is important to underline that it was applied the method ReCipe Endpoint (H)/ Europe ReCipe H/A by considering weighing factors referred to the mean values of the hierarchical perspective. Moreover, GHG emission was chosen to link the environmental issue to the economic aspect of the water harvesting systems in order to determine their eco-efficiency [38]. The carbon footprint was defined as the sum of all GHGs emitted within the system boundary and expressed in CO2 equivalent according to IPCC 2007 method (100-year life span). A parallel economic assessment is integrated with LCA using a life cycle perspective. It is important to underline that the economic sustainability is an important aspect to consider for farmers.

#### 2.2.4. Economic Assessment

The possibility of conducting a LCA study integrated with Life cycle costing (LCC) contributes to improve the ecoefficiency of farms [39], and thus reducing their impacts on the environment, while reducing costs [40].

A conventional cradle-to-gate LCC was applied here encompassing the assessment of all costs associated with the life cycle of both RWH systems studied.

The cost of the items included in the analysis referred to raw materials, services, other operating expenses, and labor costs. The economic data (Tables 5 and 6) derive from informal local market as proposed in other studies [41,42].



Total costs include raw materials, services, other operating expenses, and labor costs for each step. Source: data retrieved from informal local market.


**Table 6.** Economic data of the FWSS.

Total costs include raw materials, services, other operating expenses, and labor costs for each step. Source: data retrieved from informal local market.

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

A large majority of literature deals with the environmental impact of water management in agriculture purely in terms of water and energy used [23–26].

It is clear that irrigation might tip the scale towards a less sustainable scenario as observed by Stephenson et al. (2010) [23]. Some authors have evaluated the emissions generated by water harvesting systems and the related costs [32], even if the majority of the studies focused on the impact of RWH systems in urban environment [18,43–46].

In fact, rain and storm water harvesting systems are widely used in urban and agricultural areas especially where the weather conditions are unfavorable, with periods of drought alternating with periods characterized by floods and torrential rains. These aspects were already highlighted by Ghimire et al. (2017) that among the benefits of RWH indicated the reduction of stormwater runoff and combined sewers overflows events, as well as the potential impact reduction on the environment and human health, remarking a lack of understanding in the magnitude of these positive effects [13]. This is especially true in agriculture where, to the best of our knowledge, few studies analyzed the environmental and economic impacts of RWH infrastructure.

#### *3.1. Environmental Assessment*

The impact analysis allowed to identify the RWH infrastructure and its installation which has higher environmental impact. It is important to underline that with the weighing it is possible to assess the importance of each category of impact obtaining aggregate results as damage categories [47]; while the characterization permits to quantify the general impacts concerning different impacts categories [47].

Figure 2 reports the LCA results of each studied RWH system at endpoint level. Comparing the outcomes of weighing (Figure 2) and characterization (Figure 3) helps to identify the environmental performance and impacts of each RWH system. The highest damage categories were resources and human health, while ecosystem damage was the lowest in all systems.

The pond causes the highest impact on resources and human health due to used raw material. Polyvinyl chloride (PVC) production had the highest impact on all damage categories (especially in the pond system); this finding was due to the characteristics of PVC production. Additionally, Ghimire et al. (2017) found out that storage tanks represent the second most important cause of environmental impact (after energy usage) [13]. In order to reduce the impacts, the material used for the construction of a RWH device represents an important aspect to take in consideration. This is true also for the life span and volume of the storage tank that may lead to differing impacts [48]. In fact, Ghimire at al. (2014) observed lower impact of polyethylene (PE) when compared with a concrete storage tank, even if the latter has an expected life span of 70 years (50 years for the PE storage tank) [48]. According to Ghimire et al. (2017), the PE storage tank resulted as a good alternative to the RWH fiberglass storage tank that was less sustainable for the ozone depletion and freshwater withdrawal impact categories [13]. However, to the best of our knowledge, no other studies reported information about the specific impact generated by PVC used for RWH construction.

**Figure 2.** Result of the weighing, comparison of two different RWH systems with functional unit of 1 m3 of storable water. The acronyms of the different damage categories are HH (Human Health), EC (Ecosystem), RE (Resources).

**Figure 3.** Result of the characterization, comparison of two different runoff water storage systems with functional unit of 1 m3 of storable water. The values are expressed as percentages in relation to the 100% given to RWH systems with the biggest impact in each category (i.e., Pond = 100% in all the considered impact categories). The acronyms of the different impact categories are CCHH (climate change human health), OD (ozone depletion), HT (human toxicity), POF (photochemical oxidant formation), PMF (particulate matter formation), IR (ionizing radiation), CCE (climate change ecosystems), TA (terrestrial acidification), FE (freshwater eutrophication), TE (terrestrial ecotoxicity), FRE (freshwater ecotoxicity), ME (marine ecotoxicity), ALO (agricultural land occupation), ULO (urban land occupation), NLT (natural land transformation), MD (metal depletion), FD (fossil depletion).

The characterization analysis (Figure 3) showed the environmental performance of each RWH system in relative terms reporting midpoint environmental impacts.

The analysis showed that the pond system is more impactful than the FWSS in all impact categories. In particular, PVC production was the most impactful phase (11 out of 17 impact categories) regardless of the RWH system; this was due to the characteristics of the PVC production itself. In particular, for each studied system, the environmental impacts on CCHH category were due to carbon dioxide emissions coming from PVC production. This production also impacts the HT category (due to dioxin emission), POF (caused by nitrogen oxides emissions), PMF (due to sulfur dioxide emissions), CCE (caused by carbon dioxide emissions) and TA (due to sulfur dioxide emissions) impact categories. Moreover, the PVC production impacts other categories: FE (caused by phosphorus emissions in the water) and TE (due to chlorine emissions) impact categories. In addition, the impact of PVC production on the FRE category was due to nickel emission in the water for the pond system and copper emission (in the water) for the FWSS. The impacts on the ME category were due to chlorine emissions coming from PVC production. Finally, the PVC production also impacted the fossil depletion (FD) category, and this was because of the energy necessary for the production.

It is interesting to observe that 3 out of 17 impact categories (i.e., OD, IR and NLT impact categories) are affected only by environmental impact due to the pond system, while these categories are not involved in the FWSS. In fact, the extraction of oil and the production of fuel and its combustion during the excavation contributed to OD, IR and NLT impact categories only for the pond system.

Moreover, it is important to underline that the pond system is more impactful than the FWSS in the ALO and ULO impact categories due to a different occupation of land between the two water storage systems. In fact, for the same volume of stored water, unlike the pond, the FWSS does not permanently occupy arable land and can be installed on the uncultivated soil of the farm (e.g., over ditches or between rows of permanent crops that do not require machine passage). This is a major advantage especially in farms where space is a limiting factor.

Finally, the impacts on the MD category were due to the irony parts of excavator (used to create the pond), loading and irrigation systems (for both RWH systems).

#### *3.2. The Economic Aspects and Ecoefficiency Analysis*

The LCC analysis of the water systems was carried out in similar phases corresponding to LCA standard. Table 7 shows the total costs referred to the functional unit of 1 m<sup>3</sup> of storable water.


**Table 7.** The economic aspect of each system per 1 m3 of water.

All data are referred to 1 m3. Source: Authors' elaboration.

Findings showed that the FWSS's costs are slightly lower than the pond system's; in fact, the FWSS shows total costs of 16.94 € per m<sup>3</sup> of storable water, versus 20.41 € per m<sup>3</sup> in the pond system. The current literature lacks studies dealing with costs of an FWSS, though this is quite obvious considering that this system represents an innovation in the sector, which has not been studied yet. On the other hand, several studies analyzed economic aspects related to ponds' construction for rainwater harvesting, with particular reference to irrigation purposes. A literature review carried out by Lasage et al. (2015) reported an average cost for water storage ponds, with dimensions ranging from 30 to 300 m3, of 17.16 € per m<sup>3</sup> [49]. This value is slightly lower than what was found in the present study. Surprisingly, this higher cost is not related to the different lining

material (cement-wire in the cases studied in the review and plastic film in this paper's), considering that cost for lining with cement and wire is generally higher than the cost for the same operation performed with plastic film. Several further studies were carried out especially in India. Reported ponds' construction costs were substantially lower than what was found in the present study. In details, Deshmukh et al. (2016) reported 1.61 € per m<sup>3</sup> [50], while 3.71 € per m<sup>3</sup> were found for a pond lined through an HDPE (high-density polyethylene) geomembrane by Reddy at al., (2020) [51]. Finally, Shalander et al. (2016) reported construction costs for unlined ponds in India ranging from 1.80 to 4.35 € per m3 [52]. Such markedly lower construction costs for ponds are related to both the absence of lining material (in most cases) and to the lower labor costs compared to the Italian ones. Interestingly, Shalander et al. (2016) also reported construction costs for a particular rainwater storage system typical of the Jodhpur region, locally named Tanka [52]. This consists of an underground cistern made of concrete. This system is, under some aspects, comparable to the FWSS, considering that water is not stored in direct contact with air. Construction costs of a Tanka resulted equal at 21.25 € per m3—therefore higher than FWSS ones, highlighting how such innovative water storage system is also suitable outside of Europeon contexts.

An important aspect of the ecoefficiency analysis of two different water storage systems was the variability of their main components, as was demonstrated by differences in carbon footprint (as an environmental indicator) and life cycle costs (as an economic indicator) in relation to RWH systems.

The highest value of the carbon footprint and costs was obtained for the pond system, while the FWSS exhibited the lowest value of GHG emission and aggregated costs (Figure 4). These findings showed that the FWSS was the best solution under the economic and environmental point of view. In fact, the FWSS and the pond system cost 16.94 € with an emission of 17.4 gr CO2 eq per m3 of storable water and 20.41 € with an emission of 28.2 gr CO2 eq per m3 of storable water, respectively.

**Figure 4.** Combined results of the LCC and GWP (LCA analysis) of each RWH system per m3 of storable water. Source: Authors' elaboration.

#### **4. Conclusions**

The present work aimed to perform the environmental and economic analysis of two different RWH systems for irrigation purposes. In particular, LCA and LCC assessments were carried out to compare, under environmental and economic aspect, the water storage of a typical pond and an innovative flexible water storage system (FWSS). The current literature encompasses only few studies assessing the environmental and economic performance of different rainwater harvesting strategies in agriculture. For this reason, the present work represents a first attempt of such kind of evaluation in the topic—mainly regarding the evaluation of eco-efficiency—and the first step to fulfill such knowledge gap.

Findings showed that the FWSS performed better in both environmental and economic aspects, resulting in a suitable and sustainable solution for water harvesting in agriculture.

Evaluating the environmental and economic performance of a given system and carrying out comparisons among possible alternatives is crucial for a proper decisionmaking process. Considering the importance of water scarcity and water harvesting topics in a circular economy framework, carrying out this kind of scientific analysis could provide an important contribution to the decision-makers. In particular, our findings are useful not only for academics but also for farmers and practitioners working in the topic of water management.

Further studies should focus on a real case study, providing tangible evaluation of the environmental and economic performance based on existing RWH systems. The sustainability of such system highlighted by our results—along with the valuable features of the FWSS associated with flexibility and nonpermanent disturbance of the environment—paves the way for interesting abroad applications, particularly where water scarcity jeopardizes human health and food security in arid countries of the globe.

**Author Contributions:** Conceptualization N.P., A.S., W.S. and F.L.; formal analysis, N.P.; investigation, N.P., W.S. and F.L.; data curation and methodology N.P.; writing—original draft preparation N.P., A.S., W.S. and F.L.; In particular, Introduction paragraph, N.P and A.S.; Materials and Methods paragraphs N.P. and W.S.; Results and Discussion paragraph N.P., A.S. and F.L; Conclusions paragraph N.P., A.S., W.S. and F.L.; writing—review and editing N.P., A.S., W.S. and F.L.; supervision, project administration and funding acquisition, L.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the AGROENER project (D.D. n. 26329, 1 April 2016) funded by the Italian Ministry of Agriculture (MiPAAF) and the APC was funded by AGROENER project. The ideas expressed do not represent those of the Italian Ministry of Agriculture (MiPAAF).

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

#### **References**

