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Nonpotable water reuse (NPR) is one option for conserving valuable freshwater resources. Decentralization can improve distribution system efficiency by locating treatment closer to the consumer; however, small treatment systems may have higher unit energy and greenhouse-gas (GHG) emissions. This research explored the trade-off between residential NPR systems using a life-cycle approach to analyze the energy use and GHG emissions. Decentralized and centralized NPR options are compared to identify where decentralized systems achieve environmental advantages over centralized reuse alternatives, and vice versa, over a range of scales and spatial and demographic conditions. For high-elevation areas far from the centralized treatment plant, decentralized NPR could lower energy use by 29% and GHG emissions by 28%, but in low-elevation areas close to the centralized treatment plant, decentralized reuse could be higher by up to 85% (energy) and 49% (GHG emissions) for the scales assessed (20-2000 m3/day). Direct GHG emissions from the treatment processes were found to be highly uncertain and variable and were not included in the analysis. The framework presented can be used as a planning support tool to reveal the environmental impacts of integrating decentralized NPR with existing centralized wastewater infrastructure and can be adapted to evaluate different treatment technology scales for reuse. [ABSTRACT FROM AUTHOR]

Reductions in the greenhouse gas (GHG) intensity of passenger and freight transportation are possible through adoption of fuel-saving technologies, demand switching between modes, and large-scale electrification of fleets, in addition to other actions. In this study, future scenarios to 2030 and 2050 are the basis for assessment of GHG reduction potentials for major passenger and freight modes (automobiles, buses, trains, aircraft, and oceangoing vessels) across eight regions of the world. New fuel-saving technologies can significantly reduce the life-cycle GHG footprint of both passenger and freight vehicles, but not uniformly worldwide. Countries outside of the Organization for Economic Cooperation and Development (OECD) lag behind OECD countries in GHG reduction potentials for all modes but oceangoing vessels owing to a combination of slower adoption of fuel-saving technologies and a slower decarbonization of electricity generation and other processes. The reduction of GHG intensity will occur more slowly for freight modes than for passenger modes. However, improved fuel efficiency has negative feedbacks to the effectiveness of mode-switching and alternative fuel adoption policies through 2050 because improvements in the fuel efficiency of vehicles alone may cause the marginal benefits of GHG abatement policies to diminish over time. This trend may be reversed if alternative fuel pathways decarbonize at faster rates than conventional transportation fuels. The largest opportunities for GHG reductions occur in non-OECD countries. Given the many factors that distinguish transportation systems between developed and developing nations (e.g., availability of new technologies, the financial ability to acquire them, and policies to incentivize their adoption), many benefits could be gained through interregional cooperation. [ABSTRACT FROM AUTHOR]

The freight infrastructure network (e.g., roads, railways, waterways, etc.) is the backbone of nearly all trade partnerships in the United States and abroad. The manner in which the individual portions of its constituent parts are interrelated or arranged plays an important role for determining the environmental footprint of goods moved within the network. Herein, we compare the spatial distribution of potential consumer-producer exchanges (i.e., accessibility) under varying greenhouse gas (GHG) budgets or preferences for minimal transportation-related GHG emissions. We conduct case studies using two freight modes (truck and intermodal rail) for two representative commodities: meat/seafood and paper articles. Results across all counties in the United States indicate that the geographic area in which trade is possible, given a GHG budget, varies by transportation mode, location, and commodity. Our results suggest that intermodal terminal availability is an important determinant of low-GHG accessibility. Since only a fraction of road-to-rail terminals accommodate meat/seafood (4.9%) and paper (0.7%), the United States could increase its expected GHG savings associated with truck-to-rail mode-switching policies by 70% (+20 kg CO2,e/ton for meat/seafood) and 310% (+30 kg CO2,e/ton for paper) by upgrading current terminals to allow the exchange of all types of goods. [ABSTRACT FROM AUTHOR]

The life-cycle output (e.g., level of service) of infrastructure systems heavily influences their normalized environmental footprint. Many studies and tools calculate emission factors based on average productivity; however, the performance of these systems varies over time and space. We evaluate the appropriate use of emission factors based on average levels of service by comparing them to those reflecting a distribution of system outputs. For the provision of truck and bus services where fuel economy is assumed constant over levels of service, emission factor estimation biases, described by Jensen's inequality, always result in larger-than-expected environmental impacts (3%-400%) and depend strongly on the variability and skew of truck payloads and bus ridership. Well-to-wheel greenhouse gas emission factors for diesel trucks in California range from 87 to 1,500 g of CO2 equivalents per ton-km, depending on the size and type of trucks and the services performed. Along a bus route in San Francisco, well-to-wheel emission factors ranged between 53 and 940 g of CO2 equivalents per passenger-km. The use of biased emission factors can have profound effects on various policy decisions. If average emission rates must be used, reflecting a distribution of productivity can reduce emission factor biases. [ABSTRACT FROM AUTHOR]

Petroleum fuels are predominantly transported domestically by pipelines, whereas biofuels are almost exclusively transported by rail, barge, and truck. As biofuel production increases, new pipelines may become economically attractive. Location-specific variables impacting pipeline viability include construction costs, availability and costs of alternative transportation modes, electricity prices and emissions (if priced), throughput, and subsurface temperature. When transporting alcohol or diesel-like fuels, pipelines have a lower direct energy intensity than rail, barge, and trucks if fluid velocity is under 1 m/s for 4-inch diameter pipelines and 2 m/s for 8-inch or larger pipelines. Across multiple hypothetical state-specific scenarios, profit-maximizing design velocities range from 1.2 to 1.9 m/s. In costs and GHG emissions, optimized pipelines outperform trucks in each state and rail and barge in most states, if projected throughput exceeds four billion liters/year. If emissions are priced, optimum design diameters typically increase to reduce pumping energy demands, increasing the cost-effectiveness of pipeline projects. [ABSTRACT FROM AUTHOR]

Pressure management is one cost-effective and efficient strategy for controlling water distribution losses. This paper evaluates the life-cycle energy use and emissions for pressure management zones in Philadelphia, Pennsylvania, and Halifax, Nova Scotia. It compares water savings using fixedoutlet and flow-modulated pressure control to performance without pressure control, considering the embedded electricity and chemical consumption in the lost water, manufacture of pipe and fittings to repair breaks caused by excess pressure, and pressure management. The resulting energy and emissions savings are significant. The Philadelphia and Halifax utilities both avoid approximately 130 million liters in water losses annually using flow-modulated pressure management. The conserved energy was 780 GJ and 1900 GJ while avoided greenhouse gas emissions were 50 Mg and 170 Mg a year by Philadelphia and Halifax, respectively. The life-cycle financial and environmental performance of pressure management systems compares favorably to the traditional demand management strategy of installing low-flow toilets. The energy savings may also translate to cost-effective greenhouse gas emission reductions depending on the energy mix used, an important advantage in areas where water and energy are constrained and/or expensive and greenhouse gas emissions are regulated as in California, for example. [ABSTRACT FROM AUTHOR]

From 1991 to 2009, U.S. production of ethanol increased 10-fold, largely due to government programs motivated by climate change, energy security, and economic development goals. As low-level ethanol-gasoline blends have not consistently outperformed ethanol-free gasoline in vehicle performance or tailpipe emissions, national-level economic and environmental goals could be accomplished more efficiently by concentrating consumption of gasoline containing 10% ethanol (i.e., E10) near producers to minimize freight activity. As the domestic transportation of ethanol increased 10-fold in metric ton-kilometers (t-km) from 2000 to 2009, the portion of t-km potentially justified by the E10 blend wall increased from less than 40% to 80%. However, we estimate 10 billion t-km took place annually from 2004 to 2009 for reasons other than the blend wall. This "unnecessary" transportation resulted in more than $240 million in freight costs, 90 million L of diesel consumption, 300,000 metric tons of CO2-e emissions, and 440 g of human intake of PM2.5. By 2009, the marginal savings from enabling Iowa to surpass E10 would have exceeded 2.5 g CO2-e/MJ and $0.12/gallon of ethanol, as the next-closest customer was 1600 km away. The use of a national network model enables estimation of marginal transportation impacts from subnational policies, and benefits from policies encouraging concentrated consumption of renewable fuels. [ABSTRACT FROM AUTHOR]

In the modern global economy, water and energy are fundamentally connected. Water already plays a major role in electricity generation and, with biofuels and electricity poised to gain a significant share of the transportation fuel market, water will become significantly more important for transportation energy as well. This research provides insight into the potential changes in water use resulting from increased biofuel or electricity production for transportation energy, as well as the greenhouse gas and freshwater implications. It is shown that when characterizing the water impact of transportation energy, incorporating indirect water use and defensible allocation techniques have a major impact on the final results, with anywhere between an 82% increase and a 250% decrease in the water footprint if evaporative losses from hydroelectric power are excluded. The greenhouse gas impact results indicate that placing cellulosic biorefineries in areas where water must be supplied using alternative means, such as desalination, wastewater recycling, or importation can increase the fuel's total greenhouse gas footprint by up to 47%. The results also show that the production of ethanol and petroleum fuels burden already overpumped aquifers, whereas electricity production is far less dependent on groundwater. [ABSTRACT FROM AUTHOR]

Solid state drives (SSDs) show potential for environmental benefits over magnetic data storage due to their lower power consumption. To investigate this possibility, a life-cycle assessment (LCA) of NAND flash over five technology generations (150 nm, 120 nm, 90 nm, 65 nm, and 45 nm) is presented to quantify environmental impacts occurring in flash production and to view their trends over time. The inventory of resources and emissions in flash manufacturing, electricity generation, and some chemicals are based on process data, while that of fab infrastructure, water and the remaining chemicals are determined using economic input-output life-cycle assessment (EIO-LCA) or hybrid LCA. Over the past decade, impacts have fallen in all impact categories per gigabyte. Sensitivity analysis shows that the most influential factors over the life-cycle global warming potential (GWP) of flash memory are abatement of perfluorinated compounds and reduction of electricity-related emissions in manufacturing. A limited comparison between the life-cycle energy use and GWP of a 100 GB laptop SSD and hard disk drive shows higher impacts for SSD in many use phase scenarios. This comparison is not indicative for all impact categories, however, and is not conclusive due to differences in boundary and functional unit. [ABSTRACT FROM AUTHOR]

Abstract: A comparative life-cycle energy and emissions (greenhouse gas, CO, NOX, SO2, PM10, and VOCs) inventory is created for three U.S. metropolitan regions (San Francisco, Chicago, and New York City). The inventory captures both vehicle operation (direct fuel or electricity consumption) and non-operation components (e.g., vehicle manufacturing, roadway maintenance, infrastructure operation, and material production among others). While urban transportation inventories have been continually improved, little information exists identifying the particular characteristics of metropolitan passenger transportation and why one region may differ from the next. Using travel surveys and recently developed transportation life-cycle inventories, metropolitan inventories are constructed and compared. Automobiles dominate total regional performance accounting for 86–96% of energy consumption and emissions. Comparing system-wide averages, New York City shows the lowest end-use energy and greenhouse gas footprint compared to San Francisco and Chicago and is influenced by the larger share of transit ridership. While automobile fuel combustion is a large component of emissions, diesel rail, electric rail, and ferry service can also have strong contributions. Additionally, the inclusion of life-cycle processes necessary for any transportation mode results in significant increases (as large as 20 times that of vehicle operation) for the region. In particular, emissions of CO2 from cement production used in concrete throughout infrastructure, SO2 from electricity generation in non-operational components (vehicle manufacturing, electricity for infrastructure materials, and fuel refining), PM10 in fugitive dust releases in roadway construction, and VOCs from asphalt result in significant additional inventory. Private and public transportation are disaggregated as well as off-peak and peak travel times. Furthermore, emissions are joined with healthcare and greenhouse gas monetized externalities to evaluate the societal costs of passenger transportation in each region. Results are validated against existing studies. The dominating contribution of automobile end-use energy consumption and emissions is discussed and strategies for improving regional performance given private travel''s disproportionate share are identified. [Copyright &y& Elsevier]

Abstract: In recent years, the reduction of freight truck trips has been a common policy goal. To this end, policies aimed at influencing load consolidation have been suggested and implemented, resulting in higher gross vehicle weights. The purpose of such policies has generally been to mitigate congestion and environmental impacts. However, trucks cause most of the damage incurred by pavements. The supply chain associated with pavement maintenance and construction releases significant air emissions, raising the question of whether increased vehicle weights may cause unintended environmental consequences. This paper presents scenarios with estimated emissions resulting from load consolidation and changes in load factors. These scenarios reveal several points having to do with the tradeoff between tailpipe versus pavement supply-chain emissions. In some cases, unintended emissions from the pavement supply chain are found to be significant. [Copyright &y& Elsevier]

Computational logic, in the form of semiconductor chips of the complementary metal oxide semiconductor (CMOS) transistor structure, is used in personal computers, wireless devices, IT network infrastructure, and nearly all modem electronics. This study provides a life-cycle energy analysis for CMOS chips over 7 technology generations with the purpose of comparing energy demand and global warming potential (GWP) impacts of the life-cycle stages, examining trends in these impacts over time and evaluating their sensitivity to data uncertainty and changes in production metrics such as yield. A hybrid life-cycle assessment (LCA) model is used. While life-cycle energy and GWP of emissions have increased on the basis of a wafer or die, these impacts have been reducing per unit of computational power. Sensitivity analysis of the model shows that impacts have the highest relative sensitivity to wafer yield, line yield, and die size and largest absolute sensitivity to the use-phase power demand of the chip. [ABSTRACT FROM AUTHOR]

Life-cycle air emission effects of supplying water are explored using a hybrid life-cycle assessment For the typically sized U.S. utility analyzed, recycled water is preferable to desalination and comparable to importation. Seawater desalination has an energy and air emission footprint that is 1.5-2.4 times larger than that of imported water. However, some desalination modes fare better; brackish groundwater is 53-66% as environmentally intensive as seawater desalination. The annual water needs (326 m3) of a typical Californian that is met with imported water requires 5.8 GJ of energy and creates 360 kg of CO2 equivalent emissions. With seawater desalination, energy use would increase to 14 GJ and 800 kg of CO2 equivalent emissions. Meeting the water demand of California with desalination would consume 52% of the state's electricity. Supply options were reassessed using alternative electricity mixes, including the average mix of the United States and several renewable sources. Desalination using solar thermal energy has lower greenhouse gas emissions than that of imported and recycled water (using California's electricity mix), but using the U.S. mix increases the environmental footprint by 1.5 times. A comparison with a more energy-intensive international scenario shows that CO2 equivalent emissions for desalination in Dubai are 1.6 times larger than in California. The methods, decision support tool (WEST), and results of this study should persuade decision makers to make informed water policy choices by including energy consumption and material use effects in the decision-making process. [ABSTRACT FROM AUTHOR]

Cooling buildings with large airflow rates of outside air when temperatures are favorable is an established energy-saving measure. In data centers, this strategy is not widely used, owing to concerns that it would cause increased indoor levels of particles of outdoor origin, which could damage electronic equipment. However, environmental conditions typical of data centers and the associated potential for equipment failure are not well characterized. This study presents the first published measurements of particle concentrations in operating data centers. Indoor and outdoor particle measurements were taken at eight different sites in northern California for particulate matter 0.3–5.0μm in diameter. One of the data centers has an energy-efficient design that employs outside air for cooling, while the rest use conventional cooling methods. Ratios of measured particle concentrations in the conventional data centers to the corresponding outside concentrations were significantly lower than those typically found in office or residential buildings. Estimates using a material-balance model match well with empirical results, indicating that the dominant particle sources and losses have been identified. Measurements taken at the more energy-efficient site show nearly an order of magnitude increase in particle concentration when ventilation rates were high. The model indicates that this increase may be even higher when including particles smaller than the monitoring-equipment size limitation. Even with the increases, the measured particle concentrations are still below concentration limits recommended in industry standards. [Copyright &y& Elsevier]

This paper builds on previous research on end of life of products by synthesizing some of the theories proposed in the literature and presenting a method for environmental decision-making related to buildings. This is achieved through different solutions, but most significantly through the use of hybrid life-cycle assessment and the definition of allocation boundaries in a way that decreases the uncertainty associated with technological forecasting. Results show that there is no significant difference between the results of two major end-of-life assessment approaches (attributional and consequential), and that the choice between the use of one or the other for buildings may not be a critical decision. Assessing the impacts of recycling polices requires accounting for product substitutions, market analysis, and the full supply chain impacts of the recycling chains. Increasing the recycling of concrete from deconstructed buildings from the current 27% rate to 50% could yield a 2-3% (2.7-5.6 million metric tons of CO2 equivalents) reduction in buildings' greenhouse gas emissions, or the equivalent of removing 408,000-847,000 typical cars from U.S. roads. [ABSTRACT FROM AUTHOR]

Sewage sludge management poses environmental, economic, and political challenges for wastewater treatment plants and municipalities around the globe. To facilitate more informed and sustainable decision making, this study used life-cycle inventory (LCI) to expand upon previous process-based LCIs of sewage sludge treatment technologies. Additionally, the study evaluated an array of productive end-use options for treated sewage sludge, such as fertilizer and as an input into construction materials, to determine how the sustainability of traditional manufacturing processes changes with sludge as a replacement for other raw inputs. The inclusion of the life-cycle of necessary inputs (such as lime) used in sludge treatment significantly impacts the sustainability profiles of different treatment and end-use schemes. Overall, anaerobic digestion is generally the optimal treatment technology whereas incineration, particularly if coal-fired, is the most environmentally and economically costly. With respect to sludge end use, offsets are greatest for the use of sludge as fertilizer, but all of the productive uses of sludge can improve the sustainability of conventional manufacturing practices. The results are intended to help inform and guide decisions about sludge handling for existing wastewater treatment plants and those that are still in the planning phase in cities around the world. Although additional factors must be considered when selecting a sludge treatment and end-use scheme,this study highlights how a systems approach to planning can contribute significantly to improving overall environmental sustainability. [ABSTRACT FROM AUTHOR]

Life-cycle air emission factors associated with road, rail, and air transportation of freight in the United States are analyzed. All life-cycle phases of vehicles, infrastructure, and fuels are accounted for in a hybrid life-cycle assessment (LCA). It includes not only fuel combustion, but also emissions from vehicle manufacturing, maintenance, and end of life, infrastructure construction, operation, maintenance, and end of life, and petroleum exploration, refining, and fuel distribution. Results indicate that total life- cycle emissions of freight transportation modes are underestimated if only tailpipe emissions are accounted for. In the case of CO2 and NOx, tailpipe emissions underestimate total emissions by up to 38%, depending on the mode. Total life-cycle emissions of CO and SO2 are up to seven times higher than tailpipe emissions. Sensitivity analysis considers the effects of vehicle type, geography, and mode efficiency on the final results. Policy implications of this analysis are also discussed. For example, while it is widely assumed that currently proposed regulations will result in substantial reductions in emissions, we find that this is true for NOx emissions, because fuel combustion is the main cause, and to a lesser extent for SO2, but not for PM10 emissions, which are significantly affected by the other life-cycle phases. [ABSTRACT FROM AUTHOR]

Abstract: With the emergence of extended producer responsibility regulations for electronic devices, it is becoming increasingly important for electronics manufacturers to apply design for recycling (DFR) methods in the design of plastic enclosures. This paper presents an analytical framework for quantifying the environmental and economic benefits of DFR for plastic computer enclosures during the design process, using straightforward metrics that can be aligned with corporate environmental and financial performance goals. The analytical framework is demonstrated via a case study of a generic desktop computer enclosure design, which is recycled using a typical US “take-back” system for plastics from waste electronics. The case study illustrates how the analytical framework can be used by the enclosure designer to quantify the environmental and economic benefits of two important DFR strategies: choosing high-value resins and minimizing enclosure disassembly time. Uncertainty analysis is performed to quantify the uncertainty surrounding economic conditions in the future when the enclosure is ultimately recycled. [Copyright &y& Elsevier]

Construction of commercial buildings consumes significant amounts of energy and produces lots of emissions and waste. Where should environmental improvement efforts be focused during design and construction? The Construction Environmental Decision-Support Tool allows designers and industry practitioners to quantify energy use, emissions, and waste generation rates due to the construction phase of commercial buildings. A case study of the Bren School at the University of California, Santa Barbara, and several relevant construction scenarios are analyzed. When considering the complete building over its entire life cycle, the construction phase comprised 2% of energy consumption, 1% of CO2 emissions, 7% of CO emissions, 8% of NOx emissions, 8% of PM10 emissions, and 1% of SO2 emissions. This is due to the dominance of the long-term use phase (50 years) compared to a relatively short construction phase (2 years). Scaling up to the national level, however, construction impacts of projects are significant. In each of the categories studied (temporary materials, equipment and materials transportation, equipment use, waste generation), there are actions that can be taken by designers and builders to improve construction phase environmental effects. In structural frame construction, particular areas of concern include material and equipment selection and temporary material use. Energy use and air emissions are primarily due to equipment use, which accounts for at least 50% of most types of emissions. The major contributors are concrete mixer trucks, concrete pumps, cranes, and air compressors. A single feasible decision, such as using a concrete mixer truck with a 335 hp engine instead of one with a 565 hp engine (but having the same capacity) would reduce total construction energy demand by 12%, and the emissions of CO, NO2, PM10, SO2, CO2, and HC by 3, 12, 8, 10, 12, and 10%, respectively. The use of significantly older equipment can have a formidable effect on construction phase emissions. In general, equipment larger that 175 hp made prior to 1996 tends to have significantly greater emissions of HC, CO, and NO2 than more recent models. The majority of waste generated during construction of the structural frame consists of concrete and wood. [ABSTRACT FROM AUTHOR]

Environmental awareness is increasingly important to society, government, and industry, and there is a strong demand for sustainable development practices. The importance of supply chain management is critical, as it characterizes and influences the life cycles of all products. Within the major logistics trends, outsourcing has a significant potential to increase sustainability in the supply chain as third-party logistics providers (3PLs) focus on improving resource utilization and making processes more efficient. However, their motivation is largely economic, and an environmental perspective is rarely seen in 3PLs. As consumers demand greener alternatives and, subsequently, environmental regulatory measures are implemented, 3PLs will have to become more environmentally and socially aware in order to develop sustainability goals. This study compares two scenarios using life-cycle assessment (LCA): one where logistics functions are handled in-house, and an alternative scenario where such functions are outsourced to a 3PL. The impacts of logistics outsourcing on energy utilization, global warming potential, and fatalities are first quantified in the supply chain of an automobile. Even though vehicle operation, responsible for most of the impacts considered, is outside the domain of logistics functions, logistics outsourcing nonetheless has the potential to reduce energy use and global warming potential by 0.4–2% and fatalities by 0.8–3.3% throughout the entire life cycle of a typical automobile. Road and air transportation are found to account for most of the impacts in all selected metrics. Analyzing logistics outsourcing in the other sectors of the U.S. economy revealed the same trend as observed in the supply chain of an automobile. [ABSTRACT FROM AUTHOR]

No other industry in the United States uses more materials by weight than the construction industry. Because of its economic strength and societal importance, it is also a significant polluter and a target of growing stakeholder scrutiny. This review offers an extended, supply chain inclusive framework for the study of the construction industry that serves all the life-cycle stages of society's infrastructure systems, and it summarizes selected literature on the life-cycle environmental assessment of construction materials, designs, and processes. On the basis of identified knowledge gaps, a research agenda is discussed for lesser-studied questions in order to first understand and then eventually reduce the environmental impacts of construction materials, processes, and activities. [ABSTRACT FROM AUTHOR]

Wireless information technologies are providing new ways to communicate, and are one of several information and communication technologies touted as an opportunity to reduce society's overall environmental impacts. However, rigorous system-wide environmental impact comparisons of these technologies to the traditional applications they may replace have only recently been initiated, and the results have been mixed. In this paper, the environmental effects of two applications of wireless technologies are compared to those of conventional technologies for which they can substitute. First reading newspaper content on a personal digital assistant (PDA) is compared to the traditional way of reading a newspaper. Second, wireless teleconferencing is compared to business travel. The results show that for both comparisons wireless technologies create lower environmental impacts. Compared to reading a newspaper, receiving the news on a PDA wirelessly results in the release of 32-140 times less CO2, several orders of magnitude less NOx and SOx, and the use of 26-67 times Less water. Wireless teleconferencing results in 1-3 orders of magnitude lower CO2, NOx, and SO2 emissions than business travel. [ABSTRACT FROM AUTHOR]

The 1 billion gal of used oil generated in the U.S. each year are managed in three primary ways: rerefined into base oil for reuse, distilled into marine diesel oil fuel, and marketed as untreated fuel oil. Management of used oil has local, regional and global impacts. Because of the globally distributed nature of fuel markets, used oil as fuel has localized and regional impacts in many areas. In this paper, the human health and environmental tradeoffs of the management options are quantified and characterized. The goal of this study was to assess and compare the environmental impacts and benefits of each management method in a product end-of-life scenario using a life- cycle assessment (LCA) approach. A life-cycle inventory showed that 800 mg of zinc and 30 mg of lead air emissions may result from the combustion of 1 L of used oil as fuel (50- 100 times that of crude-derived fuel oils). As an example, up to 136 Mg of zinc and 5 Mg of lead air emissions may be generated from combustion of over 50 M gal of California- generated used oil each year. While occurring elsewhere, these levels are significant (of the same magnitude as reported total stationary source emissions in California). An impact assessment showed that heavy metals-related toxicity dominates the comparison of management methods. Zinc and lead emissions were the primary contributors to the terrestrial and human toxicity impact potentials that were calculated to be 150 and 5 times higher, respectively, for used oil combusted as fuel than for rerefining or distillation. Low profits and weak markets increasingly drive the used oil management method selection toward the untreated fuel oil market. Instead, both the rerefining and distillation methods and associated product markets should be strongly supported because they are environmentally preferable to the combustion of unprocessed used oil as fuel. [ABSTRACT FROM AUTHOR]

Assesses the greenhouse gas emissions from building and operating electric power plants in the upper Colorado River Basin in the U.S. Amount of global warming effect (GWE) in a wind farm and a hydroelectric plant; Use of the life cycle assessment method; Measurement of GWE.

Evaluates the direct and indirect effects of the service industries on the economy and the environment in the United States using an Economic Input-Output Life Cycle Assessment model. Indirect consumption effects; Comparison of the economic output of the service industry with those of the manufacturing sector; Differences in terms of environmental emissions.

Estimates the major commodity and service inputs, resource requirements and environmental emissions and wastes for four major United States construction sectors. Reduction of construction's environmental effects to promote sustainable development; US Department of Commerce's definition of construction sectors; Sectors' use of resources and rates of environmental emissions and wastes .

Focuses on life-cycle assessment (LCA), with emphasis on process and product models and environmental sciences. Defintion of LCA; What are process and product models used for; Importance of LCA.

Contrasts the one-to-one ranking of the Toxics Release Inventory data with a ranking based on relative toxicity using the `threshold limit value' (TLV) indices. Approaches to toxicity weighing systems; Comparison of releases and toxicity; TRI as data source for the evaluation of potential environmental and health effects of industrial plants.

In recent years, cities in some water stressed regions have explored alternative water sources such as seawater desalination and potable water recycling in spite of concerns over increasing energy consumption. In this study, we evaluate the current and future life-cycle energy impacts of four alternative water supply strategies introduced during a decade-long drought in South East Queensland (SEQ), Australia. These strategies were: seawater desalination, indirect potable water recycling, network integration, and rainwater tanks. Our work highlights the energy burden of alternative water supply strategies which added approximately 24% life-cycle energy use to the existing supply system (with surface water sources) in SEQ even for a current post-drought low utilisation status. Over half of this additional life-cycle energy use was from the centralised alternative supply strategies. Rainwater tanks contributed an estimated 3% to regional water supply, but added over 10% life-cycle energy use to the existing system. In the future scenario analysis, we compare the life-cycle energy use between “Normal”, “Dry”, “High water demand” and “Design capacity” scenarios. In the “Normal” scenario, a long-term low utilisation of the desalination system and the water recycling system has greatly reduced the energy burden of these centralised strategies to only 13%. In contrast, higher utilisation in the unlikely “Dry” and “Design capacity” scenarios add 86% and 140% to life-cycle energy use of the existing system respectively. In the “High water demand” scenario, a 20% increase in per capita water use over 20 years “consumes” more energy than is used by the four alternative strategies in the “Normal” scenario. This research provides insight for developing more realistic long-term scenarios to evaluate and compare life-cycle energy impacts of drought-adaptation infrastructure and regional decentralised water sources. Scenario building for life-cycle assessments of water supply systems should consider i) climate variability and, therefore, infrastructure utilisation rate, ii) potential under-utilisation for both installed centralised and decentralised sources, and iii) the potential energy penalty for operating infrastructure well below its design capacity (e.g., the operational energy intensity of the desalination system is three times higher at low utilisation rates). This study illustrates that evaluating the life-cycle energy use and intensity of these type of supply sources without considering their realistic long-term operating scenario(s) can potentially distort and overemphasise their energy implications. To other water stressed regions, this work shows that managing long-term water demand is also important, in addition to acknowledging the energy-intensive nature of some alternative water sources. [ABSTRACT FROM AUTHOR]

Nitrogen standards for discharge of wastewater effluent into aquatic bodies are becoming more stringent, requiring some treatment plants to reduce effluent nitrogen concentrations. This study aimed to assess, from a life-cycle perspective, an innovative decentralized approach to nitrogen recovery: ion exchange of source-separated urine. We modeled an approach in which nitrogen from urine at individual buildings is sorbed onto resins, then transported by truck to regeneration and fertilizer production facilities. To provide insight into impacts from transportation, we enhanced the traditional economic and environmental assessment approach by combining spatial analysis, system-scale evaluation, and detailed last-mile logistics modeling using the city of San Francisco as an illustrative case study. The major contributor to energy intensity and greenhouse gas (GHG) emissions was the production of sulfuric acid to regenerate resins, rather than transportation. Energy and GHG emissions were not significantly sensitive to the number of regeneration facilities. Cost, however, increased with decentralization as rental costs per unit area are higher for smaller areas. The metrics assessed (unit energy, GHG emissions, and cost) were not significantly influenced by facility location in this high-density urban area. We determined that this decentralized approach has lower cost, unit energy, and GHG emissions than centralized nitrogen management via nitrification-denitri&cation if fertilizer production offsets are taken into account. [ABSTRACT FROM AUTHOR]

Public transit systems with high occupancy can reduce greenhouse gas (GHG) emissions relative to low-occupancy transportation modes, but current transit systems have not been designed to reduce environmental impacts. This motivates the study of the benefits of design and operational approaches for reducing the environmental impacts of transit systems. For example, transit agencies may replace level-of-service (LOS) by vehicle miles traveled (VMT) as a criterion in evaluating design and operational changes. In previous work, we explored the unintended consequences of lowering transit LOS on emissions in a single-technology transit system. Herein, we extend the analysis to account for a more realistic case: a transit system with a hierarchical structure (trunk and feeder lines) providing service to a city where demand is elastic. By considering the interactions between the trunk and the feeder systems, we provide a quantitative basis for designing and operating integrated urban transit systems that can reduce GHG emissions and societal costs. We find that highly elastic transit demand may cancel emission reduction potentials resulting from lowering LOS, due to demand shifts to lower occupancy vehicles. However, for mass transit modes, these potentials are still significant. Transit networks with buses, bus rapid transit or light rail as trunk modes should be designed and operated near the cost-optimal point when the demand is highly elastic, while this is not required for metro. We find that the potential for unintended consequences increases with the size of the city. Our results are robust to uncertainties in the costs and emissions parameters. [ABSTRACT FROM AUTHOR]

Presents a response by Bob Boughton to a letter to the editor referencing his article "Environmental Assessment of Used Oil in Management Methods," published in previous issue of "Environmental Science & Technology."

Manufacturing accounts for 37% of the global energy demand. Few researchers have conducted a holistic energy assessment of factories where energy beyond production equipment is accounted for, and environmental impact assessments of machine tool manufacturing are even more limited. All the while, factories need to understand where energy is used, how to allocate it to their products, and where savings lie. This paper quantifies the energy consumption and greenhouse gas emissions of a machine tool manufacturer located in Iga, Japan. Six plants within the factory are investigated whose primary operations range from precision machining to product assembly. Furthermore, a model of the energy consumption of each plant's HVAC system is developed and used to evaluate the environmental impacts and operating costs at alternative sites in China, Germany, and the US. Location was found to have a significant influence on the environmental impacts and resulted in changes in the annual energy consumption relative to the Iga baseline that ranged from −10% to 8%. Additionally, opportunities for improvement were identified by comparing the energy intensities of the equipment within the plants to industrial averages. Since the plants in this study use widespread manufacturing processes and varied climates were investigated, the methods and strategies that were developed can be extended to other discrete manufacturing facilities to identify opportunities for cleaner production. [ABSTRACT FROM AUTHOR]

The water-energy nexus is of growing interest for researchers and policy makers because the two critical resources are - interdependent. Their provision and consumption contribute to climate change through the release of greenhouse gases (GHGs). This research considers the potential for conserving both energy and water resources by 5 measuring the life-cycle economic efficiency of greenhouse gas reductions through the water loss control technologies of pressure management and leak management. These costs are compared to other GHG abatement " technologies: lighting, building insulation, electricity generation, and g passenger transportation. Each cost is calculated using a bottom-up approach where regional and temporal variations for three different California water utilities are applied to all alternatives. The costs and abatement potential for each technology are displayed on an environmental abatement cost curve. The results reveal that water loss control can reduce GHGs at lower cost than other technologies and well below California's expected carbon trading price floor. One utility with an energy-intensive water supply could abate 135,000 Mg of GHGs between 2014 and 2035 and save-rather than spend-more than $130/Mg using the water loss control strategies evaluated. Water loss control technologies therefore should be considered in GHG abatement portfolios for utilities and policy makers. [ABSTRACT FROM AUTHOR]

Abstract: Concrete is one of the most widely used building materials with a global consumption rate approaching 25gigatonnes per year. Consequentially, its environmental burden is significant in terms of resource use and environmental emissions. There is a diverse audience of decision makers and manufacturers who are interested in understanding and lowering the environmental impact of concrete and other buildings materials, which requires a life-cycle assessment (LCA) approach. A critical first step in any LCA is the compilation of a credible life-cycle inventory (LCI), upon which subsequent life-cycle impact assessment (LCIA) can be based. This article reviews the strengths and weaknesses of concrete LCIs to date, and offers a research roadmap to improve the quality of future cement and concrete LCIs and meet the needs of major LCA users. [Copyright &y& Elsevier]

Passenger cars in the United States (U.S.) rely primarily on petroleum-derived fuels and contribute the majority of U.S. transportation-related greenhouse gas (GHG) emissions. Electricity and biofuels are two promising alternatives for reducing both the carbon intensity of automotive transportation and U.S. reliance on imported oil. However, as standalone solutions, the biofuels option is limited by land availability and the electricity option is limited by market adoption rates and technical challenges. This paper explores potential GHG emissions reductions attainable in the United States through 2050 with a county-level scenario analysis that combines ambitious plug-in hybrid electric vehicle (PHEV) adoption rates with scale-up of cellulosic ethanol production. With PHEVs achieving a 58% share of the passenger car fleet by 2050, phasing out most corn ethanol and limiting cellulosic ethanol feedstocks to sustainably produced crop residues and dedicated crops, we project that the United States could supply the liquid fuels needed for the automobile fleet with an average blend of 80% ethanol (by volume) and 20% gasoline. If electricity for PHEV charging could be supplied by a combination of renewables and natural-gas combined-cycle power plants, the carbon intensity of automotive transport would be 79 g CO2e per vehicle-kilometer traveled, a 71% reduction relative to 2013. [ABSTRACT FROM AUTHOR]

Abstract: This article uses life-cycle assessment to evaluate the role of long-life pavements in achieving environmental goals. The success of such pavements in reducing environmental impacts over their life cycle hinges on their ability to serve their intended purpose for their design life. Those pavements that do serve for their entire design life offer extreme longevity at only a marginal environmental cost. However, the return on the initial environmental investment occurs after many decades of use and is often beyond conventional analysis periods. Evolving performance expectations and demand create uncertainty regarding the ability of long-life pavements to reach environmental goals because time-dependent factors, such as technology shifts and functional obsolescence, affect their ability to serve for their entire design life. [ABSTRACT FROM AUTHOR]

There is increasing interest in evaluating the environmental performance of urban agriculture (UA), primarily using life cycle assessment (LCA). However, LCA has been applied to UA inconsistently, making it difficult to confidently compare or draw conclusions from existing studies. This article outlines the key challenges of applying LCA to UA and recommends concrete steps to bring consistency and comprehensiveness to the topic. The research questions that LCA can address are framed before providing practical recommendations for performing LCAs of UA, considering several of its unique aspects that require special attention by practitioners. These include crop diversity, data availability, modeling compost, soil carbon sequestration, producing growing media, distribution of crops, and variability and uncertainty. Next, the article proposes future research areas that will benefit LCA generally and its application to UA, such as framing UA as urban green infrastructure, evaluating at the city scale, accounting for ecosystem services, and including social dimensions of UA. By following these recommendations, future LCAs of UA can be more consistent, comparable, and holistic, and will help build knowledge and inform policy-making and practices around UA. [Display omitted] • Life cycle assessment can address key societal issues relevant to urban agriculture. • Its application to urban agriculture raises multiple and unique challenges. • Handling of composts, crop distribution and growing media create large uncertainties. • Practical recommendations were derived to improve the reliability of LCAs. • Accounting for ecosystem services and social dimensions should be prioritized. [ABSTRACT FROM AUTHOR]

Abstract This paper, which is a contribution to the UNEP series on Eco-Efficient Cements, examines the role of material-based solutions to reducing CO 2 emissions from cement production considering factors that could influence implementation. Global urbanization has led to an increase in demand for cement and cement-based materials. With its growth in consumption, the associated CO 2 emissions from its production are raising concern. However, the role of mitigation strategies in a global context that account for regional material availability and degree of market adoption have yet to be considered. This work shows that the 2 °C scenario targets for 2050 can be met through increased use of calcined clay and engineered filler with dispersants. The introduction of new Portland clinker-based cement alternatives, use of alkali-activated materials, and improvement of efficiency of cement use could further contribute to reduction goals. There are currently-available technologies for reduction that could be rapidly implemented. [ABSTRACT FROM AUTHOR]

Public transit systems with efficient designs and operating plans can reduce both total costs and greenhouse gas (GHG) emissions. Total costs are a sum of user cost and agency cost. In previous work, we explored in various hypothetical city scenarios possible tradeoffs between GHG emissions and total costs for optimally designed transit systems. However, most current transit systems were not designed to minimize total costs. This study aims at finding the potential emission impact when optimizing the total costs of such a system, the MUNI bus network for the city of San Francisco. The continuum approximation (CA) method is used to obtain a stylized representation of the network. Total costs and emissions are derived as functions of system attributes such as headways and spacing. We analyze the optimal total costs and emissions and the corresponding attributes. Our result shows that a significant reduction in GHG emissions is achieved when total costs are reduced simultaneously. The cost-optimal MUNI bus system has a total cost of 0.15 billion $/year and emits 1 680 metric tons of greenhouse gases. These figures amount to about half of the cost and a third of the emissions in the current MUNI bus system. The optimal system has a lower spatial availability but a higher temporal availability of bus service than the current system, which highlights the potential benefits of providing more frequent express bus services. [ABSTRACT FROM AUTHOR]

In this research, formulae for predicting compressive strength and global warming potential (GWP) per cubic meter of concrete are proposed. These equations allow for prediction of properties based on the water-to-binder ratio for concrete mixtures containing cement as the only binder, as well as for concretes containing Class F fly ash (FA) and ground granulated blast furnace slag (GGBS) as partial cement replacement. To meet multi-criteria demands of mechanical properties and lower GWP, a method for obtaining the optimal water-to-binder ratio, for given replacement level, is presented. In this research, optimization is based on a direct ratio of GWP to compressive strength, but the methodology has the potential to be extended to other environmental impact categories and material property relationships. For the classes of concrete examined, the analyses showed that high levels of cement replacement with GGBS may provide the best, hence resulting in the lowest, ratio of GWP to compressive strength for the mixtures examined. Additionally for the classes of concrete examined, the results showed that optimal water-to-binder ratios for the best ratio of GWP to compressive strength occurred at relatively high strengths (∼50–70 MPa). Yet, the majority of concrete used in countries such as the U.S. is lower strength concrete (<∼35 MPa). For the mixtures examined, it was shown that the concrete mixtures of low compressive strength (i.e., high water-to-binder ratios) containing only cement as the binder provided a lower ratio of GWP to compressive strength than some of the mixtures containing large quantities of replacement binder suggesting replacement of cement as a binder may not always be the most sustainable solution for low strength concretes. [ABSTRACT FROM AUTHOR]

As awareness and concern for greenhouse gas emissions grow, methods for reducing a significant industrial emission source, the production of cement for use in concrete, have been appearing. Assessments of these methods typically do not take into account the influence of material properties and environmental impacts concurrently. When both are considered, rarely are properties considered other than concrete strength. In this research, methods for assessing environmental impacts with mechanical properties concurrently for design of non-reinforced concrete are presented. Tools for assessing environmental impacts based on the volume of material needed as defined by several material properties and design parameters, such as required moment of inertia and cross-sectional area, are investigated. The indices for comparison developed in this research are applied to a database containing 190 concrete mixtures with varying constituents both with and without Supplementary Cementitious Materials (SCMs). For the mixtures and comparison indices examined, concrete mixtures containing SCMs consistently offered the best combination of associated global warming potential (GWP) and material properties. However, for several cases, it was shown that the use of Portland cement as the sole binder could provide comparable indices of GWP and material properties to concrete mixtures containing replacement binder. [ABSTRACT FROM AUTHOR]

The formation of effective policies to reduce emissions from goods movement should consider local and remote life cycle effects as well as barriers for mode shifting. Using uni- and multimodal freight movements by truck, rail, and ocean-going vessel (OGV) associated with California, a life cycle assessment (LCA) is developed to estimate the local and remote emissions that occur from freight activity inside and associated with the state. Long-run average per tonne-kilometer results show that OGVs emit the fewest emissions, followed by rail, then trucks, and that the inclusion of life cycle processes can increase impacts by up to 32% for energy and greenhouse gas (GHG) emissions and 4,200% for conventional air pollutants. Efforts to reduce emissions through mode shifting should recognize that infrastructure and market configurations may be inimical to mode substitution. A uni- and multimodal shipping emissions assessment is developed for intrastate and California-associated freight movements to illustrate the life cycle impacts of typical trips for certain types of goods. When targeting GHG reductions in California, it should be recognized that heavy-duty trucks are responsible for 99% of intrastate goods movement emissions. An assessment of future freight truck technology improvements is performed to estimate the effectiveness of strategies to meet 2050 GHG reduction goals. Whereas aggressive improvements in fuel economy coupled with alternative vehicles and fuels can significantly reduce GHG emissions, to meet 2050 goals will likely require zero carbon emission vehicle technology. The value of using LCA in GHG reduction policy for transportation systems is explored. [ABSTRACT FROM AUTHOR]

Treatment and water reuse in decentralized systems is envisioned to play a greater role in our future urban water infrastructure due to growing populations and uncertainty in quality and quantity of traditional water resources. In this study, we utilized life-cycle assessment (LCA) to analyze the energy consumption and greenhouse gas (GHG) emissions of an operating Living Machine (LM) wetland treatment system that recycles wastewater in an office building. The study also assessed the performance of the local utility's centralized wastewater treatment plant, which was found to be significantly more efficient than the LM (79% less energy, 98% less GHG emissions per volume treated). To create a functionally equivalent comparison, the study developed a hypothetical scenario in which the same LM design flow is recycled via centralized infrastructure. This comparison revealed that the current LM has energy consumption advantages (8% less), and a theoretically improved LM design could have GHG advantages (24% less) over the centralized reuse system. The methodology in this study can be applied to other case studies and scenarios to identify conditions under which decentralized water reuse can lower GHG emissions and energy use compared to centralized water reuse when selecting alternative approaches to meet growing water demands. [ABSTRACT FROM AUTHOR]

This paper reports the composition and properties of highly flowable self-consolidating concrete (SCC) mixtures made of high proportions of cement replacement materials such as fly ash and pulverized limestone instead of high dosage of a plasticizing agent or viscosity-modifying chemical admixtures. Self-consolidating concrete mixtures are being increasingly used for the construction of highly reinforced complex concrete elements and for massive concrete structures such as dams and thick foundation. In this study, by varying the proportion of portland cement (OPC), Class F-fly ash (F), and limestone powder (L), SCC mixtures with different strength values were produced, and the properties of both fresh and hardened concrete were determined. For a comprehensive analysis and quantification of emissions and global warming potential (GWP) from concrete production, life-cycle assessment (LCA) was employed. We find that high volume, up to 55% by weight replacement of OPC with F, or F and L produces highly workable concrete that has high 28-day and 365-day strength, and extremely high to very high resistance to chloride penetration along with low GWP for concrete production. [ABSTRACT FROM AUTHOR]

Cellulosic ethanol can achieve estimated greenhouse gas (GHG) emission reductions greater than 80% relative to gasoline, largely as a result of the combustion of lignin for process heat and electricity in biorefineries. Most studies assume lignin is combusted onsite, but exporting lignin to be cofired at coal power plants has the potential to substantially reduce biorefinery capital costs. We assess the life-cycle GHG emissions, water use, and capital costs associated with four representative biorefinery test cases. Each case is evaluated in the context of a U.S. national scenario in which corn stover, wheat straw, and Miscanthus are converted to 1.4 EJ (60 billion liters) of ethanol annually. Life-cycle GHG emissions range from 4.7 to 61 g CO2e/MJ of ethanol (compared with ∼95 g CO2e/MJ of gasoline), depending on biorefinery configurations and marginal electricity sources. Exporting lignin can achieve GHG emission reductions comparable to onsite combustion in some cases, reduce life-cycle water consumption by up to 40%, and reduce combined heat and power-related capital costs by up to 63%. However, nearly 50% of current U.S. coal-fired power generating capacity is expected to be retired by 2050, which will limit the capacity for lignin cofiring and may double transportation distances between biorefineries and coal power plants. [ABSTRACT FROM AUTHOR]

Abstract: Vehicular air pollutant emissions are characterized by a high degree of spatial variability that is correlated with the distribution of people. The consequences of the spatial association between emissions and exposed populations have not been fully captured in lifecycle and other impact assessments. The intake fraction (iF) quantifies aggregate air-pollutant exposures attributable to sources. Utilizing source–receptor (S–R) relationships derived from the US Environmental Protection Agency''s AERMOD steady-state plume model, we quantify the intake fraction of conserved pollutants emitted from on-road mobile sources and report here the first characterization across approximately 65,000 census tracts of the conterminous United States. Considering exposures out to 50 km from the source, the population-weighted mean iF is 8.6 parts per million (ppm). The population-weighted median generally increases with geographic scale, from 3.6 ppm for census tracts to 4.2 ppm for counties, and 5.1 ppm for states, while the population-weighted interquartile range (IQR) progressively narrows as geographic scale increases: 0.85–8.8 ppm for census tracts, 1.5–8.5 ppm for counties, and 3.2–7.5 ppm for states. Across the four US Census regions, the population weighted median iF varies from 2.2 ppm (South) to 7.5 ppm (West), and the census-tract IQR spans an order of magnitude in each region (2.1–17 ppm in the West; 0.55–6.9 ppm in the Midwest; 0.45–5.5 ppm in the South; and 1.8–18 ppm in the Northeast). The population-weighted mean intake fraction for populous urban counties is about two orders of magnitude greater than for sparsely populated rural counties. On a population-weighted average basis and considering the 50 km analysis range, 75% of the intake occurs in the same county as emissions. [Copyright &y& Elsevier]

Particulate matter (PM) is a significant contributor to death and disease globally. This paper summarizes the work of an international expert group on the integration of human exposure to PM into life cycle impact assessment (LCIA), within the UNEP/SETAC Life Cycle Initiative. We review literature-derived intake fraction values (the fraction of emissions that are inhaled), based on emission release height and "archetypal" environment (indoor versus outdoor; urban, rural, or remote locations). Recommended intake fraction values are provided for primary PM10-2.5 (coarse particles), primary PM2.5 (fine particles), and secondary PM2.5 from SO2, NOx, and NH3. Intake fraction values vary by orders of magnitude among conditions considered. For outdoor primary PM2.5, representative intake fraction values (units: milligrams inhaled per kilogram emitted) for urban, rural, and remote areas, respectively, are 44, 3.8, and 0.1 for ground-level emissions, versus 26, 2.6, and 0.1 for an emission-weighted stack height. For outdoor secondary PM, source location and source characteristics typically have only a minor influence on the magnitude of the intake fraction (exception: intake fraction values can be an order of magnitude lower for remote-location emission than for other locations). Outdoor secondary PM2.5 intake fractions averaged over respective locations and stack heights are 0.89 (from SO2), 0.18 (NOx), and 1.7 (NH3). Estimated average intake fractions are greater for primary PM10-2.5 than for primary PM2.5 (21 versus 15), owing in part to differences in average emission height (lower, and therefore closer to people, for PM10-2.5 than PM2.5). For indoor emissions, typical intake fraction values are ∼1000-7000. This paper aims to provide as complete and consistent an archetype framework as possible, given current understanding of each pollutant. Values presented here facilitate incorporating regional impacts into LCIA for human health damage from PM. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops the IMPACT North America model, a spatially resolved multimedia, multi-pathway, fate, exposure and effect model that includes indoor and urban compartments. IMPACT North America allows geographic differentiation of population exposure of toxic emissions for comparative risk assessment and life cycle impact assessment within U.S. and Canada. It looks at air, water, soil, sediment and vegetation media, and divides North America into several hundred zones. It is nested within a single world box to account for emissions leaving North America. It is a multi-scale model, covering three different spatial scales — indoor, urban and regional — in all zones in North America. Model results are evaluated against monitored emissions and concentrations of benzo(a)pyrene, 2,3,7,8-TCDD and mercury. Most of the chemical concentrations predicted by the model fall within two orders of magnitude of the monitored data. The model shows that urban intake fractions are one order of magnitude higher than rural intake fractions. The model application and importance is demonstrated by a case study on spatially-distributed emissions over the life cycle of diesel fuel. Depending on population densities and agricultural intensities, intake fractions can vary by eight orders of magnitudes, and even limited indoor emissions can lead to intakes comparable to those from outdoor emissions. To accurately assess these variations in intake fraction, we require the essential three original features described in the present paper: i) inclusion of the continental model within a world box for persistent pollutants, ii) addition of an urban box for short- and medium-lived substances (for grid size larger than 100 km), and iii) assess indoor emissions. This model can therefore be used to screen chemicals and assess regionalized intake fractions within North America for population-based human exposure assessment, life cycle impact assessment, and comparative risk assessment. The model can be downloaded at http://www.impactmodeling.org. [Copyright &y& Elsevier]

Life-cycle assessment (LCA) is a method for evaluating the environmental impacts of products holistically, including direct and supply chain impacts. The current LCA methodologies and the standards by the International Organization for Standardization (ISO) impose practical difficulties for drawing system boundaries; decisions on inclusion or exclusion of processes in an analysis (the cutoff criteria) are typically not made on a scientific basis. In particular, the requirement of deciding which processes could be excluded from the inventory can be rather difficult to meet because many excluded processes have often never been assessed by the practitioner, and therefore, their negligibility cannot be guaranteed. LCA studies utilizing economic input--output analysis have shown that in practice, excluded processes can contribute as much to the product system under study as included processes; thus, the subjective determination of the system boundary may lead to invalid results. System boundaries in LCA are discussed herein with particular attention to outlining hybrid approaches as methods for resolving the boundary selection problem in LCA. An input--output model can be used to describe at least a part of a product system, and an ISO-compatible system boundary selection procedure can be designed by applying hybrid input--output- assisted approaches. There are several hybrid input--output analysis-based LCA methods that can be implemented in practice for broadening system boundary and also for ISO compliance. [ABSTRACT FROM AUTHOR]