Science of the Total Environment 357 (2006) 1 – 11 www.elsevier.com/locate/scitotenv Life cycle assessment of wood wastes: A case study of ephemeral architecture Beatriz Rivelaa, Marıa Teresa Moreiraa,*, Ivan Munozb, ´ ´ ˜ b a Joan Rieradevall , Gumersindo Feijoo a Department of Chemical Engineering, University of Santiago de Compostela, C/ Lope de Marzoa s/n., E-15782 Santiago de Compostela, Spain b Department of Chemical Engineering, Autonomous University of Barcelona, E-08193 Bellaterra (Barcelona), Spain Received 12 January 2005; accepted 1 April 2005 Available online 26 May 2005 Abstract One of the most commonly used elements in ephemeral architecture is a particleboard panel. These types of wood products are produced from wood wastes and they are used in temporary constructions such as trade fairs. Once the event is over, they are usually disposed into landfills. This paper intends to assess the environmental effects related to the use of these wood wastes in the end-of-life stage. The Life Cycle Assessment (LCA) of two scenarios was performed, considering the recycling of wood waste for particleboard manufacture and energy generation from non-renewable resources (Scenario 1) versus the production of energy from the combustion of wood waste and particleboard manufacture with conventional wooden resources (Scenario 2). A sensitive analysis was carried out taking into account the influence of the percentage of recycled material and the emissions data from wood combustion. According to Ecoindicator 99 methodology, Damage to Human Health and Ecosystem Quality are more significant in Scenario 2 whereas Scenario 1 presents the largest contribution to Damage to Resources. Between the two proposed alternatives, the recycling of wood waste for particleboard manufacture seems to be more favorable under an environmental perspective. D 2005 Elsevier B.V. All rights reserved. Keywords: LCA; Wood; Ephemeral architecture residues; Energy emissions; Recycling 1. Introduction and processing of wood generates a variety of co- products and wastes throughout the wood processing Wood is the most important renewable material and chain, from its cultivation in forests, its extraction, regenerative fuel (Bowyer, 1995). The management sawing and processing to intermediate and finished products, to its recycling, incineration or final dispos- * Corresponding author. Tel.: +34 981563100x16776; fax: +34 al. Co-products and wastes generated are residues 981547168. from thinning, bark, sawdust, shavings, chips and E-mail address: firstname.lastname@example.org (M.T. Moreira). fibers, side-cuts, wood waste and waste of intermedi- 0048-9697/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2005.04.017 2 B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 ate products from wood and wood-based industries methodology but the system boundaries are different, (Jungmeier et al., 2002a,b). results are not directly comparable. This fact could be It is evident that the huge utilization of wood as considerably improved if the analyses defines a stan- raw materials needs an appropriate management as a dard functional unit and special attention is paid to the key action to optimize the use of resources and to management of the materials and how carbon fixation reduce the environmental impact associated. Sustain- on forestland is included (Jungmeier et al., 2002a,b). able management of renewable resources is defined in The objective of this paper is to assess the envi- a broad sense. One of the most widely accepted ronmental issues related to the use of wood wastes definitions was set up in 1993 by the Ministerial derived from a worldwide used wooden product: par- Conference for the Conservation of Forest in Europe: ticle boards. These items are currently used in areas bThe stewardship and use of forest and forest land in a such as carpentry, building, furniture, and decoration, way, and at a rate, that maintains their biodiversity, among others. Temporary buildings such as trade fairs productivity, regeneration capacity, viability and their often use particle boards as a contemporary form of potential to fulfill, now and in the future, relevant architecture based on mobility and flexibility noted as ecological, economic and social functions, at local, ephemeral architecture. In this research study, one national and global levels, and that does not cause representative trade fair was analyzed in detail: the damage to other ecosystemsQ (MCPFE, 1993; 2002). trade fair of Barcelona, with an annual waste genera- Based on the concept of sustainability, the equi- tion of 8,000 tons, of which 70–80% are wood waste librium between consumption of natural resources that are mainly disposed in landfills. and their regeneration has to be encouraged. This requires a more effective and efficient use of wood including optimized process technology and products 2. Methodology with longer service life and an aptitude for repairing, material recycling and finally incineration with ener- Life Cycle Assessment (LCA) is compiled of sev- gy recovery (Lafleur and Fraanje, 1997). Reuse, eral interrelated components: goal definition and recycling and energetic valorization of wood must scope, inventory analysis, impact assessment and in- be considered since the material characteristics of terpretation (ISO, 2000). SimaPro 6.1, which was wood after the utilization phase still allow for a designed by Pre Consultant, is the software used in variety of options such as material or energy carriers. ´ this study (PRe-Consultants, 2004). However, the more often the wood is reprocessed, the more restricted are its potential applications. 2.1. Goal definition and scope Besides, the investment of non-renewable energy and material is necessary to restore physical–chemi- 2.1.1. Purpose cal properties (Fraanje, 1997). The goals of this study were to assess and compare The Life Cycle Assessment (LCA) methodology the environmental impacts of end-of-life scenarios of has proved to be a valuable tool for documenting and a product using LCA methodology. The two scenarios analysing environmental considerations of product under study were (Fig. 1): and service systems that need to be part of decision- making process towards sustainability (Baumann and ! Scenario 1: Recycling of wood waste for particle- Tillman, 2004). LCA has been already considered as board manufacture and energy production from an important tool to evaluate the environmental im- non-renewable resources (i.e. natural gas). pact of wood related products (Karjalainen et al., ! Scenario 2: Energy production from the combus- 2001). Petersen and Solberg (2003) have published tion of wood waste and particleboard manufacture an extensive review of several studies of LCA appli- with ordinary wooden resources. cation to wood related products and, there, wood appears to be not only a better alternative than other The main objectives considered were the identifi- materials but also competitive on price as a building cation and quantification of the most important envi- material. As the LCA studies have all used common ronmental burdens related to the alternatives under B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 3 Particleboard with Conventional recycled material + energy SCENARIO 1 Product Wood Waste & Recovery Energy SCENARIO 2 Particleboard with no Energy from recycled material + wood waste Fig. 1. Scheme of the scenarios analyzed for wood waste treatment. analysis as a basis to discuss the final disposal of systems (ISO, 2000). The system expansion allows wood waste. the definition of an extensive functional unit that, in this study, can be delimited using allocation accord- 2.1.2. Functional unit ing to one type of material use and energy from the This unit provides a reference to which the inputs wood combustion (Jungmeier et al., 2002a). The two and outputs are related (ISO, 2000). The twofold scenarios are described in Fig. 2, including their nature of wood, commonly used as renewable mate- different subsystems. Depending on data availability, rial or regenerative fuel, is a key aspect to be con- a process analysis or an economic input–output ap- sidered. System expansion and substitution are first proach was considered to define the subsystems priority strategies for dealing with multifunctional under study. In both scenarios, the previous activities situations. As a consequence of the system expan- of manufacture and use related to ephemeral archi- sion, a variety of functions are added up to the tecture are assumed not to affect to the environmental functional unit (Jungmeier et al., 2002a,b). Experts burdens considered as we are studying an end-of-life from industry stated that a recycling percentage of phase (Boughton and Horvath, 2004). Infrastructures 30% would have no detrimental effect on the final were not taken into account according to the principle quality of the board, which would result into a lower of excluding identical activities for comparative consumption of wood raw material from forest opera- assessments (Consoli, 1993; Werner et al., 1997; tions and sawmill. According to Jungmeier et al. Jungmeier et al., 2002a). (2002a,b), a widespread functional unit was chosen, Scenario 1 includes the following subsystems: considering both the possibility of material use and energy recovery from wood combustion. Therefore, 1 ! Collection of wood waste. The consumption of the m3 of particleboard with 30% of recycled material forklift truck necessary for recollecting activities (0.42 m3 of wood waste, calculated upon the wood was computed with an average value of 3.2 L of raw materials substituted) in combination with the fuel per ton collected. energy generated if the same quantity of wood waste ! Transport and crushing. Wood waste has to be is burned in a cogeneration unit for energy purposes crushed and transferred for further processing. was the functional unit selected: 1 m3 of particle- Three alternatives were here considered (Fig. 3): board along with 260 kWh of electricity and also Option A represents the existing management of the 1570 kWh of heat. fair, that is to say, transport of the waste to a recovery center in a semitrailer, off site crushing 2.1.3. System boundaries and final transport for further processing; Option B, This term is defined as the interface between the proposed as an improvement action, takes into con- product system and the environment or other product sideration the on site crushing and its further trans- 4 B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 CONVENTIONAL ENERGY FOREST SCENARIO 1 ACTIVITIES I PARTICLEBOARD MANUFACTURE I TRANSPORT & TRITURATING WASTE COLLECTION BIOENERGY Ephemeral Architecture FOREST PARTICLEBOARD ACTIVITIES II MANUFACTURE II SCENARIO 2 Fig. 2. System boundaries and subsystems considered in the scenarios studied. port to be recycled or used as an energy source; hyde), mainly for indoor uses in which boards are Option C considers the transport of the waste to be neither exposed to high temperatures nor moisture crushed and processed in the particleboard or co- (ANSI, 1993). The inputs and outputs related to the generation plant. It is remarkable that the size of particleboard manufacture computing wood waste particle required for the recycling process is differ- materials were included in the analysis. ent from the required size for cogeneration, al- ! Conventional energy. The comparison of the sce- though there are not significant differences in the narios requires the consideration of an equal energy energy consumption. generation in both scenarios. Based on the energy ! Forest activities I. The environmental loads associ- generation from the incineration of the waste wood ated to both industrial wood and industrial residue flow (combustion of 0.42 m3 of wood waste), the wood were considered according to Ecoinvent da- cogeneration of 260 kWh of electricity plus 1570 tabase (Werner et al., 2003). The consumption of kWh was considered using natural gas as fuel. wood per m3 particleboard is around 1.39 m3 of wood materials. As Scenario 1 considered a 30% of Scenario 2 comprises the following subsystems: recycled material from ephemeral architectural, the inventory data entail the activities related to 0.67 m3 ! Collection of wood waste. As it was previously of industrial wood and 0.30 m3 of industrial residue defined in Scenario 1. wood, whereas 0.42 m3 of wood waste from the fair ! Transport and crushing. As it was previously de- fulfils the requirements of raw materials. fined in Scenario 1. ! Particleboard processing I. A particleboard is made ! Forest activities II. As defined in Scenario 1, 0.96 from small discrete wood elements with a water- m3 of industrial wood and 0.43 m3 of industrial resistant adhesive binder (usually urea formalde- residue wood were considered. B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 5 OPTION A: off site TRANSPORT OFF SITE TRANSPORT I CRUSHING I II 0.24 Ldiesel/ton•km 172.9 MJ/ton 0.02 Ldiesel/ton•km OPTION B: on site ON SITE TRANSPORT CRUSHING III FURTHER PROCESSING Ephemeral Architecture 4.6 Ldiesel/ton 0.02 Ldiesel/ton•km 6,000 ton/year OPTION C: off site TRANSPORT OFF SITE IV CRUSHING II 0.24 Ldiesel/ton•km 172.9 MJ/ton Fig. 3. Alternatives for transport and crushing of wood waste. ! Particleboard processing II. The inputs and outputs (2003). The subsystems linked to forest activities, related to conventional particleboard manufacture particleboard manufacture and energy cogeneration were included in the analysis. According to experts scenarios are inventoried using data from the Ecoin- from industry, no significant differences related to ¨ vent database (Werner et al., 2003; Fruhwald et al., energy and additives consumption as well as emis- ¨ 1996; Fruhwald et al., 2001). The particleboard sions from the process were found between parti- considered is for indoor use and includes the inputs cleboard processing I and II. to the production processes, transport of those ! Bioenergy. A typical combined heat and power inputs and the process emissions (Werner et al., plant (CHP) operating with biomass were consid- 2003). ered, with a standard ratio of electricity / heat of The electricity profile is of major importance as it 1 : 6. The cogeneration of 260 kWh of electricity broadly affects the environmental impacts assigned plus 1570 kWh from wood waste combustion was to energy-consuming steps. The assignment of the considered. environmental loads associated to the different sources of electricity was made from BUWAL 250 2.1.4. Data quality database (1996). According to data from the Insti- All the data related to the consumptions of the tute for Diversification and Energy Saving (Spain): subsystems of wood waste collection, transport and 35.8% of the electricity is produced from coal, crushing were obtained from the company, which 27.6% is nuclear, 13.9% is hydroelectric, 9.9% is manages the wood waste from the Barcelona fair. obtained from oil power plants, 9.7% from gas The assignment of the environmental loads associ- power plants, 2.2% from wind power plants, 0.6% ated to these consumptions was made according to from waste use and 0.3% from biomass use (IDAE, Kellenberger et al. (2003) and Spielmann et al. 2004). 6 B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 2.1.5. Allocation 2.2. Life cycle inventory Allocation is the apportioning of the input or out- put flows of a unit process to the product system Life Cycle Inventory (LCI) analysis involves the under study (ISO, 2000). The wood residues from collection and computation of data to quantify rele- the trade fair, as they are considered waste from vant inputs and outputs of a product system, including other activities, have no environmental burden alloca- the use of resources and releases to air, water and land tion from previous processes and only their transport associated with the system (ISO, 2000). The inventory and further processing were computed. Residues in data were collected for each process unit included forest and in the wood industry taken into account for within the system boundaries. Data sources are indi- particleboard manufacture, referred here as industrial cated in the data quality sub-section and they are wood waste, are in fact by-products that can be used detailed in the results and discussion section. as raw materials and fuel (i.e. edgings and chips coming from sawmill). An economic allocation from 2.3. Impact assessment Ecoinvent database considering the wood resource, CO2 absorption from air and the energy in biomass Impact assessment is a technical, quantitative and/ is used to assign the proper mass, energy and CO2 or qualitative process to characterize and assess the uptake from nature (Werner et al., 2003). It is remark- effects of the environmental burdens identified in the able that allocation according to monetary value has Inventory (Consoli, 1993). Damage oriented impact the fundamental disadvantage that market prices for assessment methodology has received attention in re- forest products have a very volatile variation over cent years (Goedkoop and Spriensma, 2000; Hertwich time, so it must be revised according to the short- ¨¨ ¨ ¨¨ and Hammitt, 2001; Seppala and Hamalainen, 2001; term market disturbances. Erlandsson and Lindfors, 2003). This approach pro- vides not only characterization (potential impacts of 2.1.6. Sensitivity analysis impact categories such as climate change), but also To estimate the variability of the results obtained, damage assessment for safeguard subjects such as two suppositions were considered: human health (Goedkoop et al., 1998). This impact assessment was performed with the Ecoindicator 99 ! Proportion of recycled material. Different percen- methodology, which reflects the state of art in LCA tages of recycled material from 10% to 50% were (Itsubo, 2002). The inventory data are assigned to considered with the subsequent modifications of categories that represent basic environmental issues. the inventory data associated to the flows of raw Three conditions affecting human and environment are materials substituted. considered: Human Health (HH), Ecosystem Quality ! Emissions data from wood waste combustions. (EQ) and sufficient supply of Resources (R). Model- There are various technical possibilities of energy ling and estimation of an environmental indicator for generation from wood waste. Those aspects to be each category or issue are completed. Damages to HH taken into account for the analysis are the conver- are expressed in Disability Adjusted Life Years sion efficiency from fuel to electricity and/or heat, (DALY). Damages to EQ are expressed as Potentially the electricity / heat ratio, emissions to air (flue gas Disappeared Fraction (PDF) and Potentially Affected cleaning system) and ash treatment (Jungmeier et Fraction (PAF) of species due to an environmental al., 2003). Three alternatives were analyzed con- impact. The PDF and PAF values are then multiplied sidering the effect of the cogeneration plant scale by the area size and the time period to obtain the and the emissions to air. Bioenergy A involves a damage. Damages to R are expressed as the surplus cogeneration unit of 6400 kWth (option selected in energy for the future mining of the resources. Scenario 2). The same unit is proposed in the Bioenergy B scenario with a stricter control of 2.4. Interpretation emissions (filter for particulate matter and selective non-catalytic reduction for NOx). Bioenergy C The interpretation phase may involve the iterative corresponds to a cogeneration unit of 1400 kWth. process of reviewing and revising the scope of the B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 7 LCA, as well as the nature and quality of the data combustion of wood under a sustainable wood pro- collected consistent with the outlined goal (ISO, duction might be CO2-neutral, but not CO2-free. En- 2000). ergy generation avoids natural oxidation (respiration) of biomass by emitting the same amount of CO2; therefore in a 50-years scenario the carbon cycle 3. Results and discussion might be closed (Jungmeier et al., 2003). Wood combustion emissions have been shown in 3.1. Life cycle inventory previous studies to be highly variable and dependent on many factors related to burning conditions, fuels The wood waste collection in the fair reveals a and appliances (McDonald et al., 2000). Complete consumption of 3.2 L diesel per ton collected. The combustion is difficult to obtain and it is rarely main data of the subsystem covering transport and achieved; during incomplete combustion several crushing activities are summarized in Fig. 3. Option A harmful byproducts can be formed including polycy- entails the transport of wood waste to a recovery clic aromatic hydrocarbons and particulate matter plant, located 25 km far from the fair, by trucks (Kralovec et al., 2002). Moreover, there have been with an average load of 2.5 tons; the wood waste is many reports on formation of dioxins and dioxin-like crushed with an electrical grinder and further trans- compounds (polychlorinated dibenzofurans) (Yasu- ported an average distance of 100 km to the particle- hara et al., 2003). In this work, the module of inven- board factory or the cogeneration unit by truck with tory data for bioenergy describes the combustion of an average load of 17 tons. The proposed Option B wood chips, including the infrastructure, the wood comprises a transportable grinder with a processing input, the emissions to air, the transport of fuel and capacity of 100 tons a day, the consumption of crush- the disposal of ashes. Inventory data also include the ing and transport of the grinder covering a round trip substances needed for operation: lubricating oil, urea, of 50 km. In this case, crushed wood is transported to organic chemicals, sodium chloride, chlorine and free- the same destination that Option A (100 km approx- CO2 water. Data from Ecoinvent database have been imately) by trucks with an average load of 17 tons. considered to inventory cogeneration alternatives in Option C entails the direct transport of wood waste to order to make feasible a revision for all the readers the particleboard factory or the cogeneration unit by (Werner et al., 2003); nevertheless the complexity of truck and further crushing there with an electrical wood combustion should involve a more detailed and grinder. The wastes coming from the crushing opera- specific analysis of the operational conditions. tion, mainly plastics, represent only the 3% of the main flow. Emissions generated in the landfill are 3.2. Transport and crushing: on site vs. off site not considered since they do not significantly modify the global results (Werner et al., 1997). Moreover, Fig. 4 shows the environmental fingerprint of equal amounts of waste of the same composition are options A, B and C. The diagram represents a com- treated in all scenarios, so the environmental burdens parative analysis of the environmental advantages and associated to their treatment can be rejected according disadvantages of the three alternatives. For each cat- to the principle of excluding identical activities for egory, the characterization values were obtained and comparative assessments (Consoli, 1993; Raynolds et they are relatively compared, assigning a value b1Q to al., 2000; Boughton and Horvath, 2004). the least favorable alternative in the category under It is assumed that wood particles for conventional analysis. The possibility of crushing the wood waste particleboard manufacture have to be taken from for- in the particleboard or cogeneration plant involves a estry and sawmill to satisfy the present demand of the high capacity of transport, which leads to higher particleboard industry (industrial wood and industrial environmental burdens in all the categories analyzed. residue wood, respectively). Emissions from the asso- When comparing options A with B, it is observed that, ciated activities were considered as well as the envi- with the exception of the category of Ozone Layer, the ronmental burdens allocated to edgings and chips results obtained show a significant improvement in proceeding from sawmill. It is noteworthy that the the environmental performance of transport and crush- 8 B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 CC RI categories of Carcinogens, Respiratory organics, Res- R piratory inorganics, Climate change, Radiation and Ozone layer; damage to Ecosystem Quality is associ- RO ated to the categories of Ecotoxicity, Acidification/ Eutrophication and Land use and damage to OL Resources is related to the categories of Minerals and Fossil fuels. The damage to Human Health is C considerably higher in Scenario 2 (1.9 d 10À 4 DALY in Scenario 1 and 5.9 d 10À 4 DALY in Scenario 2). E The damage to Ecosystem Quality is also favorable to FF Scenario 1 (37.3 PDF m2 year for Scenario 1 vs. 74.2 PDF m2 year for Scenario 2). On the other hand, A/E Scenario 1 presents the largest contributions of dam- M age to Resource (782 MJ surplus in Scenario 1 and LU 456 MJ surplus in Scenario 2). Fig. 4. Environmental fingerprint of Option A vs. Option B. C: The contribution of the different subsystems to the Carcinogens; RO: Respiratory organics; RI: Respiratory inorganics; total impact of each Scenario was analyzed in detail. CC: Climate change; R: Radiation; OL: Ozone layer; E: Ecotoxicity; The subsystems of bwood collectionQ and btransport A/E: Acidification/Eutrophication; LU: Land use; M: Minerals; FF: and crushingQ are common for both scenarios and Fossil fuels. Symbols: (n) Option A; (E) Option B; (x) Option C. present a minor contribution to the overall impact in most of the categories analysed (under 10%); only the ing activities when Option B is considered (from 57% contributions of two categories are relevant: Ozone to 80% for the categories analyzed). This fact is Layer (47.9% in Scenario 1 and 40.8% in Scenario 2) explained in simple terms by the saving of diesel in and Acidification/Eutrophication (25.6% in Scenario transport when the waste is crushed before being 1 and 14.6% in Scenario 2). The main differences transported. The use of electricity as energy source between the scenarios are explained by the reduction for crushing would improve the environmental per- of the environmental impact caused by forest activities formance but the available mobile grinder consumes diesel as fuel. CC RI The Option B, corresponding to the optimized subsystem of btransport and crushingQ, is suitable for R both Scenario 1 and 2; thus, it is the option that will be RO further considered in the next section. OL 3.3. Scenario 1 vs. scenario 2 C The analysis of the contribution of the different subsystems to the impact categories is required to E detect the bhot spotsQ. According to the accepted FF LCA protocol of Ecoindicator 99, a methodical pro- cedure for classifying and characterizing the types of A/E environmental effects of each element was performed M and potential environmental impacts were assessed LU (Goedkoop and Spriensma, 2000; Rivela et al., 2004). The results for the characterization step are shown Fig. 5. Environmental fingerprint of Scenario 1 vs. Scenario 2. C: Carcinogens; RO: Respiratory organics; RI: Respiratory inorganics; in Fig. 5. Considering the damage assessment as the CC: Climate change; R: Radiation; OL: Ozone layer; E: Ecotoxi- computation of all the individual contributions of the city; A/E: Acidification/Eutrophication; LU: Land use; M: Minerals; categories, damage to Human Health is related to the FF: Fossil fuels. Symbols: (E) Scenario 1; (n) Scenario 2. B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 9 Percentage of recycled material Climate Change Variation (DALY)•105 0% 10% 20% 30% 40% 50% 25 25 Land Use Variation (PDF•m2yr) 20 20 15 15 10 10 5 5 0 0 -5 -5 -10 -10 -15 -15 Fig. 6. Climate Change and Land Use Deviation results for characterization in relation to percentage of material recycled (reference scenario: 30% material recycled). Symbols: (E) Climate Change; (n) Land Use. in Scenario 1. However, it is remarkable that the use level of recycling. A percentage of 30% was selected of natural gas for energy purposes instead of wood in as the representative of value considered in industry, Scenario 1 turns into a significantly higher value for but different percentages in a range of 10–50% were the category of Fossil fuels. analyzed to evaluate the effect of this supposition. In order to discuss the obstacles and limitations of The results obtained for the characterization step of this work, a sensitive analysis was carried out. Scenario 1 exhibit a minor influence of this topic for most of the categories studied with a deviation lower 3.3.1. Wood recycling ratios than 5%. Obviously, the new scenarios have different Technologies available for recycling management inputs of natural gas, according to the energy gener- were studied in order to establish the most adequate ated in each case if the same quantity of wood waste Table 1 Characterization data of different scenarios for energy generation from 0.42 m3 of wood waste Characterization step Category Unit Bioenergy A Bioenergy B Bioenergy C Carcinogens DALY.10 5 4.40 4.43 4.76 Respiratory organics DALY.107 1.27 1.28 1.36 Respiratory DALY.104 3.37 1.01 7.60 Inorganics DALY.105 1.48 2.43 1.45 Climate change DALY.107 1.49 1.51 1.66 Radiation DALY.109 2.27 2.38 2.65 Ozone layer PAF.m2yr 162.00 163.00 175.00 Ecotoxicity PDF.m2yr 5.00 4.94 6.50 Acidification/ Eutrophication PDF.m2yr 15.40 15.50 16.50 Land use MJ surplus 0.96 0.98 1.49 Minerals MJ surplus 19.40 20.50 23.00 Fossil fuel Damage assessment Human health DALY.104 4.0 1.7 8.2 Ecosystem quality PDF.m2yr 36.7 36.8 40.5 Resources MJ surplus 20.3 21.5 24.5 10 B. Rivela et al. / Science of the Total Environment 357 (2006) 1–11 used in the particleboard manufacture was burned in a leads to a significant reduction of the environmental cogeneration unit; thus, characterization results for the burdens of the process. As a first approach, the recy- category of Fossil Fuels vary from 80.7 to 656.0 MJ cling of the wood waste for particleboard manufacture surplus. Moreover, two categories show a significant seems to be more favorable from an environmental effect of recycled percentage: Climate Change and point of view. In this sense, alternative renewable en- Land Use. Fig. 6 represents the variation (difference ergies should be encouraged to avoid damage to in relation to a scenario with 30% of recycled mate- resources. rial) of the characterization results according to the percentage of recycled material considered. Increasing the percentage of recycled material increases the con- Acknowledgments sumption of natural gas as well as reduces the assim- ilation of CO2 from atmosphere from the raw This work was supported by the Galician Auto- materials substituted, worsening the results of the nomous Government, Xunta de Galicia (Project Climate Change category. On the other hand, Land references: PGIDIT04TAL262003PR and PGIDIT02- Use category improves with the increase in recycling. TAM26201PR). 3.3.2. Effect of energy emissions The results from the characterization step of the three alternatives considered for the subsystem of References Bioenergy (cogeneration of 260 kWh of electricity ANSI, American National Standard ANSI 208.1-1993. plus 1570 kWh of heat from wood waste combustion) Baumann H, Tillman AM. The hitch hiker’s guide to LCA. are shown in Table 1. 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