Influence of the Wood Species, Forest Management Practice and Allocation Method on the Environmental Impacts of Roundwood and Biomass

Abstract

This study quantifies and compares the environmental impacts of production systems of biomass and roundwood from different wood species—maritime pine, eucalyptus, and cryptomeria. The results showed that roundwood and biomass from eucalyptus had the highest environmental impacts in most of the environmental categories. In contrast, cryptomeria products had the lowest impacts. For biomass, the impacts were higher for the forest production scenario when less biomass was produced (eucalyptus). The literature review showed that one of the main topics under study in the quantification of the environmental impacts of biomass is the allocation methodology. Thus, this study compared the environmental impacts of the various scenarios considering different methods of allocation: sub-division of processes, volume, mass, economy, and energy. The results showed that, for most scenarios, the biomass environmental impacts calculated by subdivision of processes had the highest values. In contrast, the environmental impacts of biomass calculated by economic allocation had the lowest environmental impact in most scenarios. The impacts of mass and energy allocation were similar for both products in all scenarios. Furthermore, this study showed that the system boundaries in biomass production have a strong influence on the environmental impacts and require further research.

1. Introduction

In recent years, the search for sustainable energy sources suitable that are suitable replacements for fossil fuels has shown a significant increase [1]. Biomass obtained from responsible and sustainable forestry sources has emerged as a viable alternative for energy production [2,3]. Apart from energy production, biomass has also been studied as a sustainable alternative for other uses [3,4] to replace products with a high environmental impact. Roundwood, another forest product, is also highlighted as a raw material of great interest for high added-value purposes, especially in the construction sector [5,6].

The environmental impacts of both products have been calculated and compared with other market alternatives, and both have shown good performance. González-Garcia et al. [7] analysed 12 types of forest systems in Europe with different species (willow, poplar, maritime pine, Douglas-fir, and spruce) dedicated to wood production for industrial or energy uses. The authors based their study on six forest management systems [8,9,10,11,12,13]. The system boundary has been divided into three stages: site preparation, stand establishment and tending, and harvesting operations. The functional unit defined was one cubic meter of felled fresh roundwood per year. In addition, the differences between forest operations, others were identified in management regimes (light or intensive), lifespan (between 10 and 90 years), basic density (between 340 and 451 kg/m³), yield (between 6.1 and 58.8 m³/(ha/year)), and amount of fertiliser and manure (when applicable, in kg of product per ha). The authors reported the difference in environmental results depending on tree species, management regime (level of fertilisation, time of harvesting, and intensity of forest operations) and country. Harvesting operations, i.e., felling and cutting as well as primary transport, the operations related to fertilising, such as production and fertilisation, and operations related to weed control were identified as environmental hotspots.

Based on the literature review, Klein et al. [14] proposed a method for the Life Cycle Assessment (LCA) of forest production based on ISO 14040 [15], ISO 14044 [16], and EN 16485 [17]. According to the authors, the system boundary must start with the site preparation process and end at the forest exit road, including all relevant processes that take place directly in the forest (primary processes). The mandatory processes considered must include site preparation, site tending, forestry operations and secondary processes. The transportation process beyond the forest road and group chipping process (if chipping is conducted on-site) can be optionally considered. The recommended functional unit is the cubic meter of product. In the study, the authors referred that the subdivision of processes (dividing the single process into two or more production systems) is applicable if all processes can be sub-divided into specific processes for each different product. When this is not possible, mass and volume allocations are preferable to economic allocation because prices can vary a lot in terms of time and region. For future research, to obtain clearer conclusions, the authors recommended the study and comparison of various allocation methodologies for wood used for material and fuel purposes.

Similar to the LCA studies conducted on roundwood, some studies have calculated the environmental impacts of biomass (Costa et al. [18], Chen et al. [19], and Gonçalves et al. [3]). Hosseinzadeh-Bandbafha et al. [20] did a review on the LCA of bioenergy product systems and identified three main phases for bioenergy systems: (i) biomass production, including cultivation, collection, processing, and transportation; (ii) bioenergy production, including pre-treatment, production, transportation, and distribution of bioenergy, and (iii) construction, demolition, and recycling of the bioenergy plant. Martín-Gamboa et al. [21] reviewed approximately 60 studies that performed an LCA of biomass for pellets production. Six types of raw materials were identified: wood biomass (raw, forest waste, and industrial waste), herbaceous biomass (raw and waste), and fruit biomass (agro-industrial waste). The authors concluded that the operations considered in system boundaries vary with the type of biomass. Most of the studies assumed that waste biomass is free of environmental burdens, which means that the environmental impacts of biomass were 100% allocated to the environmental impacts calculated. The remaining studies applied either mass, economic, or energy allocation procedures.

For most of the studies analysed, biomass was mainly assumed as a residue from forest management operations. In these situations, according to the studies analysed, the system boundaries begin with the collection of biomasses in the forest. However, following the allocation rules given by ISO 14044 [16], when biomass is obtained from roundwood forest management, the forest management operations directly associated with roundwood production should also be included in the biomass system boundary. The environmental impacts related to these operations can be accounted for within biomass system boundaries through allocation procedures.

One of the main gaps identified in roundwood and biomass LCA studies is the lack of consensus on allocation processes. According to ISO 14044 [16] and EN 16485 [17], firstly, the allocation of products and co-products shall be based on the subdivision of processes. In this allocation methodology, the inputs, outputs, and processes shall be sub-divided between the different products in a way that reflects the physical relationship between them. In the case of products and co-products processes that cannot be sub-divided, the products and co-products processes can be grouped and analysed together. When the difference in revenue between co-products is “low” (lower than 25%), the allocation shall be based on physical properties, such as volume and mass. For other cases, an economic allocation shall be assumed. Whenever that product and co-products have functions directly related to its physical properties (e.g., energy content for energy production), the allocation method shall reflect its physical flows.

Silvestre et al. [22] compared the manufacturing share of volume, mass, and economic allocation procedures of outputs from Insulated Cork Boards (ICB) production: boards and granulate. The authors found that, as the difference in revenue of co-products was high, the economic allocation procedure should be followed. However, this procedure led to environmental impacts that did not respect the physical relationships between products and co-products. Furthermore, the authors stated that the results from this type of allocation could not be compared with the majority of LCA results (e.g., in Environmental Product Declarations (EPDs)) of forest products because they are usually achieved using physical allocation procedures. Therefore, the types of allocation should be chosen not only according to the rules given by the standards but also to the scope and objectives of the study.

In the literature, no studies quantifying and comparing the environmental impacts of roundwood and biomass with different allocation methodologies were found. Furthermore, no studies quantifying and comparing the environmental impacts of maritime pine (Pinus pinaster Aiton), eucalyptus (Eucalyptus globulus Labill.), and cryptomeria (Cryptomeria japonica (Thunb. Ex L.f.) D.Don) biomass were found. For the latter, no studies quantifying the environmental impacts of roundwood were found either. This study calculates and compares the environmental impacts of five types of roundwood and biomass from various origins: maritime pine (planted), eucalyptus (planted), and cryptomeria (planted). The environmental impacts are calculated using the methodology given by EN 15804+A2 [23] standard. Finally, the environmental impacts of the various products are calculated and compared using different allocation methodologies: the subdivision of processes, and volume, mass, economic, and energy allocation.

This study applied the LCA methodology to quantify the environmental impacts of various Portuguese forest management scenarios. The application of LCA methodology comprises four stages: (i) goal and scope definition, (ii) life cycle inventory, (iii) life cycle impact assessment, and (iv) interpretation. The first two stages are assessed in Section 2, and the two last are assessed in Section 3 and Section 4.

2. Materials and Methods

2.1. Goal and Scope Definition

The aim of this study was to quantify and compare the environmental impacts of various types of roundwood from different Portuguese forest management scenarios. Those scenarios were:

• Planted maritime pine (MP_Plant);
• Planted eucalyptus (Euc_Plant);
• Planted cryptomeria (Crypt_Plant).

For each roundwood production scenario, it was also modelled the production of biomass:

• Biomass from planted maritime pine scenario (MP_Plant_Biomass);
• Biomass from planted eucalyptus scenario (Euc_Plant_Biomass);
• Biomass from planted cryptomeria scenario (Crypt_Plant_Biomass).

The declared unit of this study was 1 m³ of roundwood with bark at the forest road. Additionally, a declared unit of 1 m³ of biomass at the forest road was also considered. Biomass included the bio-residues from thinning and pruning operations and branches. The system boundary covers the operations from the preparation of soil for plantation until the harvesting of trees. The forest operations life cycle was divided into site preparation, stand establishment, and tending and harvesting operations.

The MP_Plant and Euc_Plant scenarios cover the following operations:

• Site preparation: harrowing with disk harrow, ploughing, subsoiling with subsoiler plough, and road construction and management;
• Stand establishment and tending: Phosphorus (P) fertilising, Nitrogen (N) fertilising, seedling production (from unheated greenhouses for the planted scenario), manual planting, mechanical weed control with a forwarder, thinning and pruning with a power saw, and forwarding of thinned logs with a forwarder;
• Harvesting operations: the harvesting operations were entirely mechanical and were performed with a harvester (with a total height of 14 ton) and forwarding (with a total height of 11 ton). The harvester cuts the trees to the ground and cuts them to a specific size for sawing. The forwarder then carries and transports them to the forest road.

The Crypt_Plant scenario covered the same operations but excluded fertilising. The system boundary of each biomass scenario covered the same operations of roundwood production but excluded harvesting operations.

2.2. Life Cycle Inventory

The data were collected from two different sources: generic and site-specific data. The generic data sources were the LCA databases (e.g., Ecoinvent [24]). The site-specific data were calculated from companies’ inquiries and from the literature [8,25,26]. The LCA databases were used to model the background data, such as the inputs and outputs of forest operations (for site preparation, stand establishment, tending and harvesting operations).

The data inventoried were geographically and technologically limited to the Centro region of Portugal and its industrial technology. The time-related coverage was representative of 2016. Whenever it was not available for background data, mean data representative of the decade from 2010 to 2020 was adopted. For data collected in the LCA databases, the mean data representative of the last decade were chosen.

The inventory of forest management processes was performed through companies’ inquiries. The data were collected for the management operations of a hectare of forest land. In order to obtain the results per cubic meter of roundwood and biomass, the inputs and outputs of the production processes were divided by the total volume of roundwood and biomass, respectively. The total volume of roundwood produced per hectare of land, the volume of co-products produced per hectare of land, stands’ productivity, dry wood density and the rotation period of each scenario are shown in

Table 1. Total volume of roundwood produced per hectare of land, volume of co-products produced per hectare of land, stands’ productivity, dry wood density and rotation period of various scenarios.

Forest Scenario	Total	Roundwood	Biomass	Productivity	Dry Wood Density	Rotation Period
	m3	m3	m3	m3/ha/year	kg/m3	Year
MP_Plant	499.2	412.8	86.4	8.0	561.8	45.0
Euc_Plant	744.0	697.5	46.5	15.5	852.0	45.0
Crypt_Plant	557.7	429.0	128.7	14.3	290.8	30.0

.

The inputs and outputs of operations performed during the forest growth of maritime pine, cryptomeria and eucalyptus were modelled using data provided by Portuguese governmental offices and associations reports and the Ecoinvent database [24] processes. The modelling procedures based on the Ecoinvent were performed through agricultural and forest processes available in this database. The processes used to model the operations within the system boundaries are shown in

Table 2. Ecoinvent process used to model operations of various forest management scenarios within the system boundary (RoW—Rest of the World; RER—European region, GLO—Global, U—unitary process).

Forest Operations		Database Operations
Site preparation	Harrowing with disk harrow	Tillage, harrowing, by offset disk harrow {RoW}| tillage, harrowing, by offset disk harrow|Cut-off, U
	Ploughing	Tillage, ploughing {RoW}| processing|Cut-off, U
	Subsoiling with subsoiler plow	Tillage, subsoiling, by subsoiler plow {RoW}| tillage, subsoiling, by subsoiler plow|Cut-off, U
	Road construction	Diesel, burned in building machine {GLO}| processing|Cut-off, U
	Road maintenance	Diesel, burned in building machine {GLO}| processing|Cut-off, U
Stand establishment and tending	Seedling	Tree seedling, for planting {RER}| tree seedling production, in unheated greenhouse|Cut-off, U
	P fertilising	Phosphate fertiliser, as P2O5 {GLO}| market for|Cut-off, U
	N fertilising	Nitrogen fertiliser, as N {GLO}| market for|Cut-off, U
	Mechanical weed control with forwarder	Tillage, harrowing, by offset disk harrow {RoW}| tillage, harrowing, by offset disk harrow|Cut-off, U
	Thinning and pruning with power saw	Power sawing, without catalytic converter {RER}| processing|Cut-off, U
	Forwarding of thinned logs with forwarder	Forwarding, forwarder {RER}| forwarding, forwarder|Cut-off, U
Harvesting operations	Harvesting with harvester	Harvesting, forestry harvester {RER}| harvesting, forestry harvester|Cut-off, U
	Forwarding	Forwarding, forwarder {RER}| forwarding, forwarder|Cut-off, U

.

The processes for construction and maintenance of roads were not found in the database. The modelling procedures of those processes were made based on the LCI performed by Dias et al. [25], which found that the consumption of diesel for those operations is 8.27 MJ and 7.72 MJ, respectively, for each operation of a forest road area of 249.55 m²/ha as given by Ferreira et al. [26]. The diesel consumption was modelled by the “Diesel, burned in building machine {GLO}| processing|Cut-off, U” process.

In addition to the processes identified in Table 2, this study also considers inputs from the environment, such as: “Carbon dioxide, in air”, “Solar energy” (equal to the gross calorific value of wood species), “Wood, soft, standing”, “Transformation, from forest, extensive”, “Transformation, from forest, intensive”, “Transformation, from traffic area, rail/road embankment”, “Transformation, to traffic area, rail/road embankment”, and “Land occupation forest”. These inputs were quantified according to the information given by Ferreira et al. [26] and the quantities modelled are shown in

Table 3. Biomass related inputs of various forest management scenarios.

Forest Scenario	Rotation Period	Total Volume per ha	Biomass Related Inputs
			Wood	Energy	Carbon
Units	years	m3	m3	MJ	kg
MP_Plant	45	499.2	1.00	10,994.8	1030.9
Euc_Plant	45	744.0	1.00	15,744.1	1563.3
Crypt_Plant	30	557.7	1.00	6446.8	533.6

and

Table 4. Land use inputs of various forest management scenarios.

Forest Scenario	Transformation, from and to Forest	Transformation, from and to Traffic Area	Land Occupation	Traffic Road Occupation
	m2/m3	m2/m3	m2·year/m3	m2·year/m3
MP_Plant	19.5	0.50	878.9	22.5
Euc_Plant	13.1	0.34	589.7	15.1
Crypt_Plant	17.5	0.45	524.5	13.4

. These inputs are grouped into “Land occupation” and “Biomass related inputs”. The carbon content of each product was calculated according to Equation (1) of EN 16449 [27], and is shown in

Table 5. Calculation of carbon content of each product.

Wood Species	Density	Density at 0% of Moisture Content (MC)	Amount of Carbon Dioxide Sequestered
	kg/m3	kg/m3	kg/m3
Maritime pine	597.0	561.8	1030.9
Eucalyptus	905.3	852.0	1563.3
Cryptomeria	309.0	290.8	533.6

.

The yield of harvesting operations (hours of work per cubic meter of wood) was determined based on data given by Dias et al. [5]. The yield of the other operations was given by the Ecoinvent database per hectare of land. That study considers data calculated by national offices (Institute for Nature Conservation and Forests) and industry associations’ (Association for the Competitiveness of the Forest Industries) reports, which provide representative values for Portuguese scenarios. These reports quantified the inputs and outputs of diesel, petrol, and lubricants combustion and use in machinery, per hour of work (litres per hour), and the yield of machinery (hour per ha). The data from these reports were summarised by Dias and Arroja [8]. The background data of these processes were obtained from the Ecoinvent database. Inputs of roundwood and biomass production processes are shown in Tables S1 and S2 of the Supplementary Material document.

3. Results

3.1. LCIA Methodology

The LCIA methodology followed in this study was that proposed by EN 15804+A2 [23]. This method is aligned with the requirements of the Environmental Footprint 3.0 (EF) methodology [28], except for the biogenic carbon account. The EN 15804+A2 [23] method considers that the emission of biogenic carbon causes the same impact as fossil carbon on the Climate change indicator, but this impact can be neutralised by removing this carbon from the atmosphere through photosynthesis processes. In contrast, EF 3.0 methodology does not include biogenic carbon uptake and release.

The environmental impacts were calculated using the SimaPro 9.1 software [29]. SimaPro assigns the LCI results to the selected impact categories (classification) and determines the corresponding results based on characterisation factors given by EN 15804+A2 [23]. This study calculates the core environmental impact categories given by EN 15084+A2 [23]: global warming potential (GWP-t), global warming potential fossil fuels (GWP-f), global warming potential biogenic (GWP-b), and global warming potential land use and land use change (GWP-luluc), the depletion potential of the stratospheric ozone layer (ODP), acidification potential (AP), eutrophication potential, the fraction of nutrients reaching freshwater end compartment (EP-f), eutrophication potential, the fraction of nutrients reaching marine end compartment (EP-m), and eutrophication potential—accumulated exceedance (EP-t), formation potential of tropospheric ozone (POCP), abiotic depletion potential for non-fossil resources (minerals and metals) (ADP-m), abiotic depletion potential for fossil resources (ADP-f), and water deprivation potential—deprivation weighted water consumption (WDP). The environmental impacts per each cubic meter of roundwood and biomass are shown in Tables S3 and S4 in the Supplementary Material document.

3.2. Comparison of Results

The core environmental impacts of the production of one cubic meter of roundwood with bark (at the forest road) production and of one cubic meter of biomass (at the forest road) production of the various scenarios assessed are shown in Figure 1, respectively.

In Figure 1, the roundwood of eucalyptus had the highest impact on the GWP-f, ODP, AP, EP-m, EP-t, and the ADP-f and WDP categories. In contrast, this scenario had the lowest impact on the GWP-t and GWP-b categories. Cryptomeria had the smallest impacts on GWP-f, AP, EP-f, EP-m, EP-t, POCP, ADP-m, ADP-f, and WDP. In contrast, cryptomeria had the highest impact on the GWP-t and GWP-b categories. Maritime pine (planted) had the highest impacts on the GWP-luluc, EP-f, and ADP-m categories.

Figure 2 shows that eucalyptus biomass had the highest impacts on all categories, except on GWP-t and GWP-b, where cryptomeria biomass had the highest impacts. In contrast, cryptomeria had the lowest impacts on all categories, except on GWP-t and GWP-b, where eucalyptus biomass had the lowest impacts.

For both products, the eucalyptus management scenarios had the highest impact on most categories. The difference in impacts between eucalyptus and the other wood species was higher for biomass than for roundwood products. These results were a consequence of the reduced volume of biomass produced in eucalyptus management (approximately half that of maritime pine and three times less than that of cryptomeria) and the number of operations carried out during eucalyptus forest management (which was higher than those of maritime pine and cryptomeria).

The forest management processes for roundwood and biomass production were very similar in both cases, and it was not possible to clearly distinguish which processes correspond only to the production of roundwood or biomass. Therefore, according to ISO 14044 [8] and EN 15804+A2 [9] rules, an allocation of inputs and outputs should be made to the entire production system.

3.3. Discussion—Comparison of Allocation Methodologies

3.3.1. Calculation of Allocation Percentages

This section intends to compare the environmental impacts of roundwood and biomass calculated using different allocation methodologies. The results shown were calculated by allocating the operations of various forest management scenarios to each product (a subdivision of processes). In this stage, the volume, mass, economic and energy allocation methodologies were considered. The calculation of allocation percentages is described below.

The volume allocation was calculated based on the total amount of biomass and roundwood extracted from a hectare of forestland during the periods given. The volumes of roundwood and biomass, given in, were used to calculate the volume allocation percentages also shown in

Table 6. Calculation of percentages of volume allocation.

	Volume of Wood Produced		Volume Percentage
Product	Biomass	Roundwood	Biomass	Roundwood
Unit	m3/ha	m3/ha	%	%
MP_Plant	86.4	412.8	17%	83%
Euc_Plant	46.5	697.5	6%	94%
Crypt_Plant	128.7	429	23%	77%

.

The mass allocation percentages were calculated by multiplying the total volume extracted from the forest by the density of products. The density of the biomass and roundwood of each species were obtained from the literature review and are shown in

Table 7. Calculation of percentages of mass allocation.

	Density (at 12% of MC)		Mass Percentage
Product	Biomass	Roundwood	Biomass	Roundwood
Unit	kg/m3	kg/m3	%	%
MP_Plant	506.5	597.0	15%	85%
Euc_Plant	567.0	905.3	4%	96%
Crypt_Plant	309.0	309.0	23%	77%

, which also presents the mass allocation percentage.

Economic percentages were calculated by multiplying the price of each cubic meter of biomass and roundwood by the total volume produced. The prices of biomass and roundwood were given in February 2022 by a company that purchases both products. Prices per cubic meter of products and allocation percentage are shown in

Table 8. Calculation of percentages of economic allocation.

	Price of Products		Economic Percentage
Product	Biomass	Roundwood	Biomass	Roundwood
Unit	€/m3	€/m3	%	%
MP_Plant	25	75	7%	93%
Euc_Plant	25	45	4%	96%
Crypt_Plant	25	70	10%	90%

.

The energy allocation percentages were calculated by multiplying the gross calorific value of each wood species by the total volume produced. The gross calorific values were found in the literature and are shown in

Table 9. Calculation of percentages of energy allocation.

	Gross Calorific Value	Density (at 0% of MC)		Energy Percentage
Product	Mega Joule	Biomass	Roundwood	Biomass	Roundwood
Unit	MJ/kg	kg/m3	kg/m3	%	%
MP_Plant	19.57	476.65	561.82	15%	85%
Euc_Plant	18.48	533.59	851.95	4%	96%
Crypt_Plant	22.17	290.79	290.79	23%	77%

, which also presents the energy percentage.

3.3.2. Comparison of Results

The comparison of the relative environmental impacts achieved with each allocation methodology is shown in Figure 3, Figure 4 and Figure 5 for maritime pine planted, eucalyptus planted, and cryptomeria planted, respectively.

For the maritime pine planted scenarios, shown in Figure 3, biomass calculated with subdivision of processes had the highest impact on most impact categories. On the other hand, biomass from economy allocation had the least impact on the majority of impact categories. Comparing roundwood and biomass impacts calculated with the subdivision of processes, biomass had higher impacts on all categories, except on ODP and ADP-m. For the other allocation methodologies, one cubic meter of roundwood had higher impacts than one cubic meter of biomass, except on GWP-t, GWP-b. The difference in impacts between both products were higher for economy allocation (higher than 200% in the majority of impact categories) and lower for volume allocation (lower than 5% in the majority of impact categories).

For roundwood, the highest impacts were noted for the subdivision of processes, followed by economy allocation. For biomass, the highest impacts were noted for subdivision of processes, followed by volume allocation. The results of energy and mass allocation were similar for both products.

The relative environmental impacts of eucalyptus roundwood and biomass, shown in Figure 4, were higher for biomass from subdivision of processes, for GWP-f, ODP, AP, EP-f, EP-m, EP-t, POCP, ADP-f, ADP-m, and WDP. For those categories, the environmental impacts of eucalyptus biomass from the subdivision of processes were higher than the other biomass allocation procedures (higher than 300%). For the GWP-t and GWP-b categories, the highest impacts were noted for biomass from mass, economic, and energy allocation. The lowest impacts were noted for roundwood from mass, economic, and energy allocation.

For roundwood and biomass, scenarios with subdivision of processes had the highest impacts on all environmental categories, followed by volume allocation. Mass, economic, and energy allocation of both products had similar impacts.

3.3.3. Discussion of Results

For maritime pine and eucalyptus scenarios, biomass from the subdivision of processes had the highest impact on most impact categories. This is because the system boundaries and production processes of biomass and roundwood were similar, but the volume of biomass produced was lower than that of roundwood. As the difference between the volume of biomass and roundwood was higher in the eucalyptus scenario, the difference between biomass and roundwood environmental impacts from subdivision of processes was also higher in the eucalyptus scenarios. In contrast, as the lowest difference in the volume of biomass and roundwood was noted for cryptomeria, the lowest difference between biomass and roundwood impacts from the subdivision of processes scenario was noted in the cryptomeria scenarios.

Roundwood from the subdivision of processes had higher impacts than roundwood from other allocation processes. This is because the allocation methodology followed reduces the allocation percentages of roundwood processes described in Section 2, which was 100% for the subdivision of processes.

The roundwood and biomass impact results from mass and energy allocation processes were similar to the results from the maritime pine scenarios. This occurs because the allocation percentage from both allocation methodologies is similar for all the wood species studied. The same occurs for mass, energy, and volume impacts of roundwood and biomass from cryptomeria and mass, energy, and economic impacts of roundwood and biomass from eucalyptus.

Excluding the subdivision of processes of roundwood and biomass, the highest difference between roundwood and biomass was noted for economic allocation in the majority of forest management scenarios. This occurs due to the difference in the prices and revenue between both products, which results in a large difference between the percentages and, consequently, between environmental impacts.

4. Conclusions

This study calculated the environmental impacts of roundwood and biomass from various forest management scenarios and wood species: maritime pine, eucalyptus and cryptomeria. The results showed that cryptomeria roundwood had the lowest environmental impacts on most categories. In contrast, eucalyptus roundwood had the highest impact on most categories.

For biomass, eucalyptus and cryptomeria had the highest and lowest impacts on most impact categories, respectively. Maritime pine biomass of various forest management scenarios had similar impacts. The analysis of results showed that the environmental impacts of biomass might be affected by the choice of system boundaries. This is because the boundaries of the biomass production system are dependent on the roundwood production operations.

In order to understand the influence of the allocation method of processes on the results, this study also calculated the environmental impacts of various forest management scenarios using various allocation methodologies referred to by EN 15804+A2: volume, mass, economic, and energy. The environmental impacts of roundwood from the subdivision of processes had higher impacts than roundwood from the other allocation methodologies. Roundwood from economic allocation had higher impacts than the other allocation methodologies on all impact categories, except on GWP-t and GWP-f, where the impacts of various allocation methodologies were similar.

According to EN 15804+A2 [23], as the difference in revenue of co-products was higher than 25%, this study shall follow an economic allocation methodology. The results showed that this was the methodology that had the lowest and highest difference in impacts to the methodology of subdivision of processes for roundwood and biomass, respectively. This occurs because of the difference in price (high) and volumes (low) between biomass and roundwood. This is also a consequence of the choice of the system boundaries assumed for biomass production, in which operations that had no direct influence on production but indirectly influenced biomass productivity were considered. Thus, in LCA studies, the quantification of biomass impacts should be undertaken following the subdivision of processes methodology.