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Many frontline communities experience adverse health impacts from living in proximity to high-polluting industrial sources. Securing environmental justice requires, in part, a comprehensive set of quantitative indicators. We incorporate environmental justice and life-cycle thinking into air quality planning to assess fine particulate matter (PM 2.5 ) exposure and monetized damages from operating and maintaining the Port of Oakland, a major multimodal marine port located in the historically marginalized West Oakland community in the San Francisco Bay Area. The exposure domain for the assessment is the entire San Francisco Bay Area, a home to more than 7.5 million people. Of the more than 14 sources included in the emissions inventory, emissions from large container ships, or ocean-going vessels (OGVs), dominate the PM 2.5 intake, and supply chain sources (material production and delivery, fuel production) represent between 3.5% and 7.5% of annual intake. Exposure damages, which model the costs from excess mortalities resulting from exposure from the study's emission sources, range from USD 100 to 270 million per annum. Variations in damages are due to the use of different concentration-response relationships, hazard ratios, and Port resurfacing area assumptions. Racial and income-based exposure disparities are stark. The Black population and people within the lowest income quintile are 2.2 and 1.9 times more disproportionately exposed, respectively, to the Port's pollution sources relative to the general population. Mitigation efforts focused on electrifying in-port trucking operations yield modest reductions (3.5%) compared to strategies that prioritize emission reductions from OGVs and commercial harbor craft operations (8.7-55%). Our recommendations emphasize that a systems-based approach is critical for identifying all relevant emission sources and mitigation strategies for improving equity in civil infrastructure systems.

An exposure-based traffic assignment (TA) model is used to quantify primary and secondary fine particulate matter (PM 2.5 ) exposure from on-road vehicle flow on the Chicago Metropolitan Area regional network. PM 2.5 exposure due to emissions from light-duty vehicles, heavy-duty trucks, public transportation, and electricity generation for electric vehicle charging and light-rail transportation is considered. The model uses travel demand data disaggregated by time-of-day period and vehicle user class to compare the exposure impacts of two TA optimization scenarios: a baseline user equilibrium with respect to travel time (UET) and a system optimal with respect to pollutant intake (SOI). Estimated baseline PM 2.5 exposure damages are $3.7B-$8.3B/year. The SOI uses exposure-based vehicle rerouting to reduce total damages by 8.2%, with high-impacted populations benefiting from 10% to 20% reductions. However, the SOI's rerouting principle leads to a 66% increase in travel time. The model is then used to quantify the mitigation potential of different exposure reduction strategies, including a bi-objective optimization formulation that minimizes travel time and PM 2.5 exposure concurrently, adoption of a cleaner vehicle fleet, higher public transportation use, particle filtration, and exposure-based truck routing. Exposure reductions range between 1% and 40%, but collective adoption of all strategies would lead to reductions upward of 50%.

This work develops an exposure-based optimal power flow model (OPF) that accounts for fine particulate matter (PM 2.5 ) exposure from electricity generation unit (EGU) emissions. Advancing health-based dispatch models to an OPF with transmission constraints and reactive power flow is an essential development given its utility for short- and long-term planning by system operators. The model enables the assessment of the exposure mitigation potential and the feasibility of intervention strategies while still prioritizing system costs and network stability. A representation of the Illinois power grid is developed to demonstrate how the model can inform decision making. Three scenarios minimizing dispatch costs and/or exposure damages are simulated. Other interventions assessed include adopting best-available EGU emission control technologies, having higher renewable generation, and relocating high-polluting EGUs. Neglecting transmission constraints fails to account for 4% of exposure damages ($60 M/y) and dispatch costs ($240 M/y). Accounting for exposure in the OPF reduces damages by 70%, a reduction on the order of that achieved by high renewable integration. About 80% of all exposure is attributed to EGUs fulfilling only 25% of electricity demand. Siting these EGUs in low-exposure zones avoids 43% of all exposure. Operation and cost advantages inherent to each strategy beyond exposure reduction suggest their collective adoption for maximum benefits.

Increasingly stringent limits on nutrient discharges are motivating water resource recovery facilities (WRRFs) to consider the implementation of sidestream nutrient removal or recovery technologies. To further increase biogas production and reduce landfilled waste, WRRFs with excess anaerobic digestion capacity can accept other high-strength organic waste (HSOW) streams. The goal of this study was to characterize and evaluate the life-cycle global warming potential (GWP), eutrophication potential, and economic costs and benefits of sidestream nutrient management and biosolid management strategies following digestion of sewage sludge augmented by HSOW. Five sidestream nutrient management strategies were analyzed using environmental life-cycle assessment (LCA) and life-cycle cost analysis (LCCA) for codigestion of municipal sewage sludge with and without HSOW. As expected, thermal stripping and ammonia stripping were characterized by a much lower eutrophication potential than no sidestream treatment; significantly higher fertilizer prices would be needed for this revenue stream to cover the capital and chemical costs. Composting all biosolids dramatically reduced the GWP relative to the baseline biosolid option but had slightly higher eutrophication potential. These complex environmental and economic tradeoffs require utilities to consider their social, environmental, and economic values in addition to present or upcoming nutrient discharge limits prior to making decisions in sidestream and biosolids management.

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-denitrification if fertilizer production offsets are taken into account.

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 m 3 /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.

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.

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.

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 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 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.

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.

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.

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 fixed-outlet 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.

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.

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 CO(2)-e emissions, and 440 g of human intake of PM(2.5). By 2009, the marginal savings from enabling Iowa to surpass E10 would have exceeded 2.5 g CO(2)-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.

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 PM(10-2.5) (coarse particles), primary PM(2.5) (fine particles), and secondary PM(2.5) from SO(2), NO(x), and NH(3). Intake fraction values vary by orders of magnitude among conditions considered. For outdoor primary PM(2.5), 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 PM(2.5) intake fractions averaged over respective locations and stack heights are 0.89 (from SO(2)), 0.18 (NO(x)), and 1.7 (NH(3)). Estimated average intake fractions are greater for primary PM(10-2.5) than for primary PM(2.5) (21 versus 15), owing in part to differences in average emission height (lower, and therefore closer to people, for PM(10-2.5) than PM(2.5)). 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.

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.

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.

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.

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 technologicalforecasting. 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.

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 treatmenttechnologies. 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.

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.

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.

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.

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.

Telework is a growing phenomenon that is thought to save energy and air emissions. This paper applies a systems model to telework and nontelework scenarios in order to quantify greenhouse gas and other air emissions from transportation, heating, cooling, lighting, and electronic and electrical equipment use both at the company and the home office. Using United States data, a WWW-based, scalable decision-support tool was created to evaluate the environmental impacts of teleworkers. For a typical case reflecting United States teleworker patterns, the analysis found that telework has the potential to reduce air emissions. However, Monte Carlo simulation employed to perform a probabilistic analysis over a set of likely parameters has revealed that telework may not affect equally the emissions of all types of pollutants. It may decrease CO2, NOx, SO2, PM10, and CO but not N2O and CH4 emissions. Therefore, the scope and goal of telework programs must be defined early in the implementation process. Work-related transportation (commuting) impacts could be reduced as a result of telework; however, home-related impacts due to an employee spending additional time at home could potentially offset these reductions. Company office-related impacts may not be reduced unless the office space is shared with other employees during telework days or eliminated entirely. In states with high telework potential (California, Georgia, Illinois, New York, Texas), telework could save emissions, but it would depend on commuting and climatic patterns and the electricity mix. Environmentally beneficial telework programs are found to depend mainly on commuting patterns, induced energy usage, and characteristics of the office and home space and equipment use.

As demand for electricity increases, investments into new generation capacity from renewable and nonrenewable sources should include assessment of global (climate) change consequences not just of the operational phase of the power plants but construction effects as well. In this paper, the global warming effect (GWE) associated with construction and operation of comparable hydroelectric, wind, solar, coal, and natural gas power plants is estimated for four time periods after construction. The assessment includes greenhouse gas emissions from construction, burning of fuels, flooded biomass decay in the reservoir, loss of net ecosystem production, and land use. The results indicate that a wind farm and a hydroelectric plant in an arid zone (such as the Glen Canyon in the Upper Colorado River Basin) appear to have lower GWE than other power plants. For the Glen Canyon hydroelectric plant, the upgrade 20 yr after the beginning of operation increased power capacity by 39% but resulted in a mere 1% of the CO2 emissions from the initial construction and came with no additional emissions from the reservoir, which accounts for the majority of the GWE.