Wood pellets,what else? Greenhouse gas parity times of European electricity from wood pellets produced in the south‐eastern United States using different softwood feedstocks

Several EU countries import wood pellets from the south‐eastern United States. The imported wood pellets are (co‐)fired in power plants with the aim of reducing overall greenhouse gas (GHG) emissions from electricity and meeting EU renewable energy targets. To assess whether GHG emissions are reduced and on what timescale, we construct the GHG balance of wood‐pellet electricity. This GHG balance consists of supply chain and combustion GHG emissions, carbon sequestration during biomass growth and avoided GHG emissions through replacing fossil electricity. We investigate wood pellets from four softwood feedstock types: small roundwood, commercial thinnings, harvest residues and mill residues. Per feedstock, the GHG balance of wood‐pellet electricity is compared against those of alternative scenarios. Alternative scenarios are combinations of alternative fates of the feedstock materials, such as in‐forest decomposition, or the production of paper or wood panels like oriented strand board (OSB). Alternative scenario composition depends on feedstock type and local demand for this feedstock. Results indicate that the GHG balance of wood‐pellet electricity equals that of alternative scenarios within 0–21 years (the GHG parity time), after which wood‐pellet electricity has sustained climate benefits. Parity times increase by a maximum of 12 years when varying key variables (emissions associated with paper and panels, soil carbon increase via feedstock decomposition, wood‐pellet electricity supply chain emissions) within maximum plausible ranges. Using commercial thinnings, harvest residues or mill residues as feedstock leads to the shortest GHG parity times (0–6 years) and fastest GHG benefits from wood‐pellet electricity. We find shorter GHG parity times than previous studies, for we use a novel approach that differentiates feedstocks and considers alternative scenarios based on (combinations of) alternative feedstock fates, rather than on alternative land uses. This novel approach is relevant for bioenergy derived from low‐value feedstocks.     

Effects of Using Heterogeneous Prices on the Allocation of Impacts from Electricity Use: A Mixed‐Unit Input‐Output Approach

Economic input‐output life cycle assessment (IO‐LCA) models allow for quick estimation of economy‐wide greenhouse gas (GHG) emissions associated with goods and services. IO‐LCA models are usually built using economic accounts and differ from most process‐based models in their use of economic transactions, rather than physical flows, as the drivers of supply‐chain GHG emissions. GHG emissions estimates associated with input supply chains are influenced by the price paid by consumers when the relative prices between individual consumers are different. We investigate the significance of the allocation of GHG emissions based on monetary versus physical units by carrying out a case study of the U.S. electricity sector. We create parallel monetary and mixed‐unit IO‐LCA models using the 2007 Benchmark Accounts of the U.S. economy and sector specific prices for different end users of electricity. This approach is well suited for electricity generation because electricity consumption contributes a significant share of emissions for most processes, and the range of prices paid by electricity consumers allows us to explore the effects of price on allocation of emissions. We find that, in general, monetary input‐output models assign fewer emissions per kilowatt to electricity used by industrial sectors than to electricity used by households and service sectors, attributable to the relatively higher prices paid by households and service sectors. This fact introduces a challenging question of what is the best basis for allocating the emissions from electricity generation given the different uses of electricity by consumers and the wide variability of electricity pricing.     

Adapting Stand‐Alone Renewable Energy Technologies for the Circular Economy through Eco‐Design and Recycling

Renewable energy (RE) technologies are looked upon favorably to provide for future energy demands and reduce greenhouse gas (GHG) emissions. However, the installation of these technologies requires large quantities of finite material resources. We apply life cycle assessment to 100 years of electricity generation from three stand‐alone RE technologies—solar photovoltaics, run‐of‐river hydro, and wind—to evaluate environmental burden profiles against baseline electricity generation from fossil fuels. We then devised scenarios to incorporate circular economy (CE) improvements targeting hotspots in systems’ life cycle, specifically (1) improved recycling rates for raw materials and (ii) the application of eco‐design. Hydro presented the lowest environmental burdens per kilowatt‐hour of electricity generation compared with other RE technologies, owing to its higher efficiency and longer life spans for main components. Distinct results were observed in the environmental performance of each system based on the consideration of improved recycling rates and eco‐design. CE measures produced similar modest savings in already low GHG emissions burdens for each technology, while eco‐design specifically had the potential to provide significant savings in abiotic resource depletion. Further research to explore the full potential of CE measures for RE technologies will curtail the resource intensity of RE technologies required to mitigate climate change.     

The Efficiency of Informality: Quantifying Greenhouse Gas Reductions from Informal Recycling in Bogotá, Colombia

The dual challenges of increasing urbanization and consumption are centered in cities in the Global South, where growing waste production threatens public and environmental health. Reuse and recycling are widely recognized to provide broad environmental benefits. Although most industrialized cities replaced their informal recycling sectors with municipally run recycling schemes and have had to build their recycling rates anew, most industrializing cities in the Global South remain centers of recycling and reuse through the work of informal workers. Bogotá, Colombia, is emblematic of many cities in the Global South seeking to modernize their city, in part by formalizing their recycling system. This article asks: What are the greenhouse gas (GHG) emission implications of this modernization? Using interviews and observation in combination with life cycle assessment, we compare GHG emissions resulting from the baseline case (1,200 tonnes per day [t/d] recycled through informal channels; 5,700 t/d landfilled) to three alternative scenarios that formalize the recycling sector: the prohibition of informal recycling; a reduction in informal recycling coupled with a scale‐up of formalized recycling; and the replacement of informal recycling with formal recycling. We find that the baseline recycling scenario, dependent on the informal sector only, emits far fewer GHGs than do all formalization scenarios. Three processes drive the results, in order of magnitude: informal textile reuse (largest GHG savings); landfilling (largest emitter of GHGs); and metal recycling (GHG savings). A hybrid model could combine the incentives and efficiency of the informal system with the better working conditions of the municipal one.     

Dry Matter Losses and Methane Emissions During Wood Chip Storage: the Impact on Full Life Cycle Greenhouse Gas Savings of Short Rotation Coppice Willow for Heat

A life cycle assessment (LCA) approach was used to examine the greenhouse gas (GHG) emissions and energy balance of short rotation coppice (SRC) willow for heat production. The modelled supply chain includes cutting multiplication, site establishment, maintenance, harvesting, storage, transport and combustion. The relative impacts of dry matter losses and methane emissions from chip storage were examined from a LCA perspective, comparing the GHG emissions from the SRC supply chain with those of natural gas for heat generation. The results show that SRC generally provides very high GHG emission savings of over 90 %. The LCA model estimates that a 1, 10 and 20 % loss of dry matter during storage causes a 1, 6 and 11 % increase in GHG emissions per MWh. The GHG emission results are extremely sensitive to emissions of methane from the wood chip stack: If 1 % of the carbon within the stack undergoes anaerobic decomposition to methane, then the GHG emissions per MWh are tripled. There are some uncertainties in the LCA results, regarding the true formation of methane in wood chip stacks, non-CO₂ emissions from combustion, N₂O emissions from leaf fall and the extent of carbon sequestered under the crop, and these all contribute a large proportion of the life cycle GHG emissions from cultivation of the crop.     

Life Cycle Inventory Analysis of the Wood Pallet Repair Process in the United States

This study developed gate‐to‐gate life cycle inventory (LCI) data for the repair of 48 by 40 inch (1,219 by 1,016 millimeter [mm]) stringer‐class wood pallets in the United States. Data were collected from seven wood pallet repair facilities. Approximately 1.98 FBM (foot, board measure) (4.67E‐03 cubic meters) of lumber were used for repairing each 48 by 40 inch (1,219 by 1,016 mm) stringer‐class wood pallet, the majority (97%) recovered from damaged pallets received by the pallet repair facilities. Repair equipment powered by electricity made the largest contribution to greenhouse gas (GHG) emissions. Steel nails used for the pallet repair had the largest contribution to GHG emissions among the material inputs, while use of recovered lumber yielded the largest GHG emissions credits. Overall, the repair process for a 48 by 40 inch (1,219 by 1,016 mm) stringer‐class wood pallet had GHG credits rather than a positive GHG emission due to the GHG offsets from co‐products.     

Application of a Life Cycle Model for European Union Policy‐Driven Waste Management Decision Making in Emerging Economies

Solid waste life cycle modeling has predominantly focused on developed countries, but there are significant opportunities to assist developing and transition economies to minimize the environmental impact of solid waste management (SWM). Serbia is representative of a transition country and most (92%) of its waste is landfilled. As a Candidate European Union (EU) country, Serbia is expected to implement SWM strategies that meet EU directives. The Solid Waste Life‐Cycle Optimization Framework (SWOLF) was used to evaluate scenarios that meet EU goals by 2030. Scenarios included combinations of landfills, anaerobic digestion, composting, material recovery facilities (MRFs), waste‐to‐energy (WTE) combustion, and the use of refuse‐derived fuel in cement kilns. Each scenario was evaluated with and without separate collection of recyclables. Modeled impacts included cost, climate change, cumulative fossil energy demand, acidification, eutrophication, photochemical oxidation, total eco‐toxicity, and total human toxicity. Trade‐offs among the scenarios were evaluated because no scenario performed best in every category. In general, SWM strategies that incorporated processes that recover energy and recyclable materials performed well across categories, whereas scenarios that did not include energy recovery performed poorly. Emissions offsets attributable to energy recovery and reduced energy requirements associated with remanufacturing of recovered recyclables had the strongest influence on the results. The scenarios rankings were robust under parametric sensitivity analysis, except when the marginal electricity fuel source changed from coal to natural gas. Model results showed that the use of existing infrastructure, energy recovery, and efficient recovery of recyclables from mixed waste can reduce environmental emissions at relatively low cost.     

Life cycle analysis of biochemical cellulosic ethanol under multiple scenarios

Cellulosic ethanol is widely believed to offer substantial environmental advantages over petroleum fuels and grain‐based ethanol, particularly in reducing greenhouse gas emissions from transportation. The environmental impacts of biofuels are largely caused by precombustion activities, feedstock production and conversion facility operations. Life cycle analysis (LCA) is required to understand these impacts. This article describes a field‐to‐blending terminal LCA of cellulosic ethanol produced by biochemical conversion (hydrolysis and fermentation) using corn stover or switchgrass as feedstock. This LCA develops unique models for most elements of the biofuel production process and assigns environmental impact to different phases of production. More than 30 scenarios are evaluated, reflecting a range of feedstock, technology and scale options for near‐term and future facilities. Cellulosic ethanol, as modeled here, has the potential to significantly reduce greenhouse gas (GHG) emissions compared to petroleum‐based liquid transportation fuels, though substantial uncertainty exists. Most of the conservative scenarios estimate GHG emissions of approximately 45–60 g carbon dioxide equivalent per MJ of delivered fuel (g CO₂e MJ^?1) without credit for coproducts, and 20–30 g CO₂e MJ^?1 when coproducts are considered. Under most scenarios, feedstock production, grinding and transport dominate the total GHG footprint. The most optimistic scenarios include sequestration of carbon in soil and have GHG emissions below zero g CO₂e MJ^?1, while the most pessimistic have life‐cycle GHG emissions higher than petroleum gasoline. Soil carbon changes are the greatest source of uncertainty, dominating all other sources of GHG emissions at the upper bound of their uncertainty. Many LCAs of biofuels are narrowly constrained to GHG emissions and energy; however, these narrow assessments may miss important environmental impacts. To ensure a more holistic assessment of environmental performance, a complete life cycle inventory, with over 1100 tracked material and energy flows for each scenario is provided in the online supplementary material for this article.     

Abatement cost of wood‐based energy products at the production level on afforested and reforested lands

We combined economic and life‐cycle analyses in an integrated framework to ascertain greenhouse gas (GHG) intensities, production costs, and abatement costs of GHG emissions for ethanol and electricity derived from three woody feedstocks (logging residues only, pulpwood only, and pulpwood and logging residues combined) across two forest management choices (intensive and nonintensive) and 31 harvest ages (year 10–year 40 in steps of 1 year) on reforested and afforested lands at the production level for slash pine (Pinus elliottii) in the Southern United States. We assumed that wood chips and wood pellets will be used to produce ethanol and generate electricity, respectively. Production costs and GHG intensities of ethanol and electricity were lowest for logging residues at the optimal rotation age for both forest management choices. Opportunity cost related with the change in rotation age was a significant determinant of the variability in the overall production cost. GHG intensity of feedstocks obtained from afforested land was lower than reforested land. Relative savings in GHG emissions were higher for ethanol than electricity. Abatement cost of GHG emissions for ethanol was lower than electricity, especially when feedstocks were obtained from a plantation whose rotation age was close to the optimal rotation age. A carbon tax of at least $25 and $38 Mg^?1 CO₂e will be needed to promote production of ethanol from wood chips and electricity from wood pellets in the US, respectively.     

玉米秸秆基纤维素乙醇生命周期能耗与温室气体排放分析

生命周期评价是目前分析产品或工艺的环境负荷唯一标准化工具,利用其生命周期分析方法可以有效地研究纤维素乙醇生命周期能耗与温室气体排放问题。为了定量解释以玉米秸秆为原料的纤维素乙醇的节能和温室气体减排潜力,利用生命周期分析方法对以稀酸预处理、酶水解法生产的玉米秸秆基乙醇进行了生命周期能耗与温室气体排放分析,以汽车行驶1 km为功能单位。结果表明：与汽油相比,纤维素乙醇E100 (100％乙醇) 和E10 (乙醇和汽油体积比=1∶9) 生命周期化石能耗分别减少79.63％和6.25％,温室气体排放分别减少53.98％和6.69％;生物质阶段化石能耗占到总化石能耗68.3％,其中氮肥和柴油的生命周期能耗贡献最大,分别占到生物质阶段的45.78％和33.26％;工厂电力生产过程的生命周期温室气体排放最多,占净温室气体排放量的42.06％,提升技术减少排放是降低净排放的有效措施。     

Evaluation of a Regional Approach to Standards for Plug‐in Battery Electric Vehicles in Future Light‐Duty Vehicle Greenhouse Gas Regulations

Representing the greenhouse gas (GHG) emissions attributable to plug‐in electric vehicles (PEV) in vehicle GHG emissions regulations is complex because of spatial and temporal variation in fueling sources and vehicle use. Previous work has shown that the environmental performance of PEVs significantly varies depending on the characteristics of the electricity grid and how the vehicle is driven. This article evaluates the U.S. Environmental Protection Agency's (EPA's) GHG emissions accounting methodology in current and future standards for new electrified vehicles. The current approach employed by the EPA in their 2017–2025 model year light‐duty vehicle GHG regulation is compared with an accounting mechanism where the actual regional sales of PEVs, and the regional electricity emission factor in the year sold, are used to determine vehicle compliance value. Changes to the electricity grid over time and regional vehicle sales are included in the modeling efforts. A projection of a future GHG regulation past the 2017–2025 rule is used to observe the effect of such a regional regulation. The results showed that the complexity involved in tracking and accounting for regional PEV sales will not dramatically increase the effectiveness of the regulations to capture PEV electricity‐related GHG emissions in the absence of a major policy shift. A discussion of the feasibility and effectiveness of a regional standard for PEVs, and notable examples of region‐specific regulations instated in past energy policies, is also addressed.     

Life cycle assessment of eucalyptus short rotation coppices for bioenergy production in southern France

Short rotation coppices (SRC) are considered prime candidates for biomass production, yielding good‐quality feedstock that is easy to harvest. Besides technical, social and economical aspects, environmental issues are important to be taken into account when developing SRC. Here, we evaluated the environmental impacts of delivering 1 GJ of heat from eucalyptus SRC using life cycle assessment (LCA), based on management scenarios involving different rotations lengths, fertilizer input rates, stem densities and harvest methods. Compared to equivalent fossil chains, all eucalyptus scenarios achieved savings of fossil energy and greenhouse gas (GHG) emissions in the 80–90% range, and had generally lower impacts, except for eutrophication. The 3 year rotation scenario was the most energy and GHG‐intensive, whereas manual felling for the longer rotations resulted in twofold larger photochemical ozone impacts compared to the other scenarios. Transportation of wood chips and fertilization were the top two contributors to the impacts, the latter being more important with the shorter rotation lengths due to the evergreen character of eucalyptus. The possibility of including ecosystem carbon dynamics was also investigated, by translating the temporary sequestration of atmospheric CO₂ in the above and belowground biomass of eucalyptus as CO₂ savings using various published equivalence factors. This offset the life cycle GHG emissions of heat provision from eucalyptus SRC by 70–400%.     

Biogenic Carbon and Temporary Storage Addressed with Dynamic Life Cycle Assessment

A growing tendency in policy making and carbon footprint estimation gives value to temporary carbon storage in biomass products or to delayed greenhouse gas (GHG) emissions. Some life cycle‐based methods, such as the British publicly available specification (PAS) 2050 or the recently published European Commission's International Reference Life Cycle Data System (ILCD) Handbook, address this issue. This article shows the importance of consistent consideration of biogenic carbon and timing of GHG emissions in life cycle assessment (LCA) and carbon footprint analysis. We use a fictitious case study assessing the life cycle of a wooden chair for four end‐of‐life scenarios to compare different approaches: traditional LCA with and without consideration of biogenic carbon, the PAS 2050 and ILCD Handbook methods, and a dynamic LCA approach. Reliable results require accounting for the timing of every GHG emission, including biogenic carbon flows, as soon as a benefit is given for temporarily storing carbon or delaying GHG emissions. The conclusions of a comparative LCA can change depending on the time horizon chosen for the analysis. The dynamic LCA approach allows for a consistent assessment of the impact, through time, of all GHG emissions (positive) and sequestration (negative). The dynamic LCA is also a valuable approach for decision makers who have to understand the sensitivity of the conclusions to the chosen time horizon.     

Energy Use and Greenhouse Gas Emissions of Air‐Source Heat Pump and Innovative Ground‐Source Air Heat Pump in a Cold Climate

This article compares climate impacts of two heat‐pump systems for domestic heating, that is, energy consumption for space heating of a residential building. Using a life cycle approach, the study compared the energy use and greenhouse gas (GHG) emissions of direct electric heating, a conventional air‐source heat pump, and a novel ground‐source air heat pump innovated by a citizen user, to assess whether such user innovation holds benefit. The energy use of the heat pumps was modeled at six temperature intervals based on duration curves of outdoor temperature. Additionally, two heat pump end‐of‐life scenarios were analyzed. Probabilistic uncertainty analysis was applied using a Monte Carlo simulation. The results indicated that, in ideal conditions, that is, assuming perfect air mixing, the conventional air‐source heat pump's emissions were over 40% lower and the ground‐air heat pump's emissions over 70% lower than in the case of direct electric heating. Although proper handling of the refrigerant is important, total leakage from the retirement of the heat‐pump appliance would increase GHG emissions by just 10%. According to the sensitivity analysis, the most influential input parameters are the emission factor related to electricity and the amount of electricity used for heating.     

Estimating product and energy substitution benefits in national‐scale mitigation analyses for Canada

The potential of forests and the forest sector to mitigate greenhouse gas (GHG) emissions is widely recognized, but challenging to quantify at a national scale. Mitigation benefits through the use of forest products are affected by product life cycles, which determine the duration of carbon storage in wood products and substitution benefits where emissions are avoided using wood products instead of other emissions‐intensive building products and energy fuels. Here we determined displacement factors for wood substitution in the built environment and bioenergy at the national level in Canada. For solid wood products, we compiled a basket of end‐use products and determined the reduction in emissions for two functionally equivalent products: a more wood‐intensive product vs. a less wood‐intensive one. Avoided emissions for end‐use products basket were weighted by Canadian consumption statistics to reflect national wood uses, and avoided emissions were further partitioned into displacement factors for sawnwood and panels. We also examined two bioenergy feedstock scenarios (constant supply and constrained supply) to estimate displacement factors for bioenergy using an optimized selection of bioenergy facilities which maximized avoided emissions from fossil fuels. Results demonstrated that the average displacement factors were found to be similar: product displacement factors were 0.54 tC displaced per tC of used for sawnwood and 0.45 tC tC^?1 for panels; energy displacement factors for the two feedstock scenarios were 0.47 tC tC^?1 for the constant supply and 0.89 tC tC^?1 for the constrained supply. However, there was a wide range of substitution impacts. The greatest avoided emissions occurred when wood was substituted for steel and concrete in buildings, and when bioenergy from heat facilities and/or combined heat and power facilities was substituted for energy from high‐emissions fossil fuels. We conclude that (1) national‐level substitution benefits need to be considered within a systems perspective on climate change mitigation to avoid the development of policies that deliver no net benefits to the atmosphere, (2) the use of long‐lived wood products in buildings to displace steel and concrete reduces GHG emissions, (3) the greatest bioenergy substitution benefits are achieved using a mix of facility types and capacities to displace emissions‐intensive fossil fuels.     

Fuel Economy and Greenhouse Gas Emissions Labeling for Plug‐In Hybrid Vehicles from a Life Cycle Perspective

Fuel economy has been an effective indicator of vehicle greenhouse gas (GHG) emissions for conventional gasoline‐powered vehicles due to the strong relationship between fuel economy and vehicle life cycle emissions. However, fuel economy is not as accurate an indicator of vehicle GHG emissions for plug‐in hybrid (PHEVs) and pure battery electric vehicles (EVs). Current vehicle labeling efforts by the U.S. Environmental Protection Agency (EPA) and Department of Transportation have been focused on providing energy and environmental information to consumers based on U.S. national average data. This article explores the effects of variations in regional grids and regional daily vehicle miles traveled (VMT) on the total vehicle life cycle energy and GHG emissions of electrified vehicles and compare these results with information reported on the label and on the EPA's fuel economy Web site. The model results suggest that only 25% of the life cycle emissions from a representative PHEV are reflected on current vehicle labeling. The results show great variation in total vehicle life cycle emissions due to regional grid differences, including an approximately 100 gram per mile life cycle GHG emissions difference between the lowest and highest electric grid regions and up to a 100% difference between the state‐specific emission values within the same electric grid regions. Unexpectedly, for two regional grids the life cycle GHG emissions were higher in electric mode than in gasoline mode. We recommend that labels include stronger language on their deficiencies and provide ranges for GHG emissions from vehicle charging in regional electricity grids to better inform consumers.     

Life Cycle–based Assessment of Energy Use and Greenhouse Gas Emissions in Almond Production,Part I: Analytical Framework and Baseline Results

This first article of a two‐article series describes a framework and life cycle–based model for typical almond orchard production systems for California, where more than 80% of commercial almonds on the world market are produced. The comprehensive, multiyear, life cycle–based model includes orchard establishment and removal; field operations and inputs; emissions from orchard soils; and transport and utilization of co‐products. These processes are analyzed to yield a life cycle inventory of energy use, greenhouse gas (GHG) emissions, criteria air pollutants, and direct water use from field to factory gate. Results show that 1 kilogram (kg) of raw almonds and associated co‐products of hulls, shells, and woody biomass require 35 megajoules (MJ) of energy and result in 1.6 kg carbon dioxide equivalent (CO₂‐eq) of GHG emissions. Nitrogen fertilizer and irrigation water are the dominant causes of both energy use and GHG emissions. Co‐product credits play an important role in estimating the life cycle environmental impacts attributable to almonds alone; using displacement methods results in net energy and emissions of 29 MJ and 0.9 kg CO₂‐eq/kg. The largest sources of credits are from orchard biomass and shells used in electricity generation, which are modeled as displacing average California electricity. Using economic allocation methods produces significantly different results; 1 kg of almonds is responsible for 33 MJ of energy and 1.5 kg CO₂‐eq emissions. Uncertainty analysis of important parameters and assumptions, as well as temporary carbon storage in orchard trees and soils, are explored in the second article of this two‐part article series.     

Comparative LCAs for Curbside Recycling Versus Either Landfilling or Incineration with Energy Recovery (12 pp)

Background This article describes two projects conducted recently by Sound Resource Management (SRMG) – one for the San Luis Obispo County Integrated Waste Management Authority (SLO IWMA) and the other for the Washington State Department of Ecology (WA Ecology). For both projects we used life cycle assessment (LCA) techniques to evaluate the environmental burdens associated with collection and management of municipal solid waste. Both projects compared environmental burdens from curbside collection for recycling, processing, and market shipment of recyclable materials picked up from households and/or businesses against environmental burdens from curbside collection and disposal of mixed solid waste. Method logy. The SLO IWMA project compared curbside recycling for households and businesses against curbside collection of mixed refuse for deposition in a landfill where landfill gas is collected and used for energy generation. The WA Ecology project compared residential curbside recycling in three regions of Washington State against the collection and deposition of those same materials in landfills where landfill gas is collected and flared. In the fourth Washington region (the urban east encompassing Spokane) the WA Ecology project compared curbside recycling against collection and deposition in a wasteto- energy (WTE) combustion facility used to generate electricity for sale on the regional energy grid. During the time period covered by the SLO study, households and businesses used either one or two containers, depending on the collection company, to separate and set out materials for recycling in San Luis Obispo County. During the time of the WA study households used either two or three containers for the residential curbside recycling programs surveyed for that study. Typically participants in collection programs requiring separation of materials into more than one container used one of the containers to separate at least glass bottles and jars from other recyclable materials. For the WA Ecology project SRMG used life cycle inventory (LCI) techniques to estimate atmospheric emissions of ten pollutants, waterborne emissions of seventeen pollutants, and emissions of industrial solid waste, as well as total energy consumption, associated with curbside recycling and disposal methods for managing municipal solid waste. Emissions estimates came from the Decision Support Tool (DST) developed for assessing the cost and environmental burdens of integrated solid waste management strategies by North Carolina State University (NCSU) in conjunction with Research Triangle Institute (RTI) and the US Environmental Protection Agency (US EPA)1. RTI used the DST to estimate environmental emissions during the life cycle of products. RTI provided those estimates to SRMG for analysis in the WA Ecology project2. For the SLO IWMA project SRMG also used LCI techniques and data from the Municipal Solid Waste Life- Cycle Database (Database), prepared by RTI with the support of US EPA during DST model development, to estimate environmental emissions from solid waste management practices3. Once we developed the LCI data for each project, SRMG then prepared a life cycle environmental impacts assessment of the environmental burdens associated with these emissions using the Environmental Problems approach discussed in the methodology section of this article. Finally, for the WA study we also developed estimates of the economic costs of certain environmental impacts in order to assess whether recycling was cost effective from a societal point of view. Conclusions Recycling of newspaper, cardboard, mixed paper, glass bottles and jars, aluminum cans, tin-plated steel cans, plastic bottles, and other conventionally recoverable materials found in household and business municipal solid wastes consumes less energy and imposes lower environmental burdens than disposal of solid waste materials via landfilling or incineration, even after accounting for energy that may be recovered from waste materials at either type disposal facility. This result holds for a variety of environmental impacts, including global warming, acidification, eutrophication, disability adjusted life year (DALY) losses from emission of criteria air pollutants, human toxicity and ecological toxicity. The basic reason for this conclusion is that energy conservation and pollution prevention engendered by using recycled rather than virgin materials as feedstocks for manufacturing new products tends to be an order of magnitude greater than the additional energy and environmental burdens imposed by curbside collection trucks, recycled material processing facilities, and transportation of processed recyclables to end-use markets. Furthermore, the energy grid offsets and associated reductions in environmental burdens yielded by generation of energy from landfill gas or from waste combustion are substantially smaller then the upstream energy and pollution offsets attained by manufacturing products with processed recyclables, even after accounting for energy usage and pollutant emissions during collection, processing and transportation to end-use markets for recycled materials. The analysis that leads to this conclusion included a direct comparison of the collection for recycling versus collection for disposal of the same quantity and composition of materials handled through existing curbside recycling programs in Washington State. This comparison provides a better approximation to marginal energy usage and environmental burdens of recycling versus disposal for recyclable materials in solid waste than does a comparison of the energy and environmental impacts of recycling versus management methods for handling typical mixed refuse, where that refuse includes organics and non-recyclables in addition to whatever recyclable materials may remain in the garbage. Finally, the analysis also suggests that, under reasonable assumptions regarding the economic cost of impacts from pollutant emissions, the societal benefits of recycling outweigh its costs.     

LCA application to integrated waste management planning in Gipuzkoa (Spain)

Goal, Scope and Background  Gipuzkoa is a department of the Vasque Country (Spain) with a population of about 700,000 people. By the year 2000 approximately 85% of municipal solid waste in this area was managed by landfilling, and only 15% was recycled. Due to environmental law restrictions and landfill capacity being on its limit, a planning process was initiated by the authorities. LCA was used, from an environmental point of view, to assess 7 possible scenarios arising from the draft Plan for the 2016 time horizon. Main Features  In each scenario, 9 waste flows are analysed: rest waste, paper and cardboard, glass containers, light packaging, organic-green waste, as well as industrial/commercial wood, metals and plastics, and wastewater sludge. Waste treatments range from recycling to energy recovery and landfilling. Results  Recycling of the waste flows separated at the source (paper and cardboard, glass, light packaging, organic-green waste, wood packaging, metals and plastics) results in net environmental benefits caused by the substitution of primary materials, except in water consumption. These benefits are common to the 7 different scenarios analysed. However, some inefficiencies are detected, mainly the energy consumption in collection and transport of low density materials, and water consumption in plastic recycling. The remaining flows, mixed waste and wastewater sludge, are the ones causing the major environmental impacts, by means of incineration, landfilling of partially stabilised organic material, as well as thermal drying of sludge. With the characterisation results, none of the seven scenarios can be clearly identified as the most preferable, although, due to the high recycling rates expected by the Plan, net environmental benefits are achieved in 9 out of 10 impact categories in all scenarios when integrated waste management is assessed (the sum of the 9 flows of waste). Finally, there are no relevant differences between scenarios concerning the number of treatment plants considered. Nevertheless, only the effects on transportation impacts were assessed in the LCA, since the plant construction stage was excluded from the system boundaries. Conclusions  The results of the study show the environmental importance of material recycling in waste management, although the recycling schemes assessed can be improved in some aspects. It is also important to highlight the environmental impact of incineration and landfilling of waste, as well as thermal drying of sludge using fossil fuels. One of the main findings of applying LCA to integrated waste management in Gipuzkoa is the fact that the benefits of high recycling rates can compensate for the impacts of mixed waste and wastewater sludge. Recommendations and Outlook  Although none of the scenarios can be clearly identified as the one having the best environmental performance, the authorities in Gipuzkoa now have objective information about the future scenarios, and a multidisciplinary panel could be formed in order to weight the impacts if necessary. In our opinion, LCA was successfully applied in Gipuzkoa as an environmental tool for decision making.     

Integration in a depot‐based decentralized biorefinery system: Corn stover‐based cellulosic biofuel

The current or “conventional” paradigm for producing process energy in a biorefinery processing cellulosic biomass is on‐site energy recovery through combustion of residual solids and biogas generated by the process. Excess electricity is then exported, resulting in large greenhouse gas (GHG) credits. However, this approach will cause lifecycle GHG emissions of biofuels to increase as more renewable energy sources (wind, solar, etc.) participate in grid‐electricity generation, and the GHG credits from displacing fossil fuel decrease. To overcome this drawback, a decentralized (depot‐based) biorefinery can be integrated with a coal‐fired power plant near a large urban area. In an integrated, decentralized, depot‐based biorefinery (IDB), the residual solids are co‐fired with coal either in the adjacent power plant or in coal‐fired boilers elsewhere to displace coal. An IDB system does not rely on indirect GHG credits through grid‐electricity displacement. In an IDB system, biogas from the wastewater treatment facility is also upgraded to biomethane and used as a transportation biofuel. The GHG savings per unit of cropland in the IDB systems (2.7–2.9 MgCO₂/ha) are 1.5–1.6 fold greater than those in a conventional centralized system (1.7–1.8 MgCO₂/ha). Importantly, the biofuel selling price in the IDBs is lower by 28–30 cents per gasoline‐equivalent liter than in the conventional centralized system. Furthermore, the total capital investment per annual biofuel volume in the IDB is much lower (by ~80%) than that in the conventional centralized system. Therefore, utilization of biomethane and residual solids in the IDB systems leads to much lower biofuel selling prices and significantly greater GHG savings per unit of cropland participating in the biorefinery system compared to the conventional centralized biorefineries.