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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]

Research has separately existed for life-cycle costs and environmental assessment of photovoltaic systems. This study provides a framework for the identification of the optimal set of residential photovoltaic system options in terms of costs and selected air emissions by assessing the life cycle of the product from manufacturing to disposal. Analyzed air emissions include carbon, nitrogen oxides, sulfur oxides, carbon monoxide, and particulate matter. The study focuses on general residential installations within the San Francisco Bay Area of California. Pareto frontiers are determined for costs and emissions, and the best options for suppliers are identified in each case, including sensitivity analysis of the installation planning horizon. Choosing multicrystalline silicon modules over thin film modules has the greatest impact on cost reduction. The electricity mix with which the modules are produced has the greatest impact on the emissions. [ABSTRACT FROM AUTHOR]

Abstract: The rapidly expanding set of pavement life-cycle assessments (LCAs) available in the literature represents the growing interest in improving the sustainability of this critical infrastructure system. The existing literature establishes a foundational framework for quantifying environmental impact, but fails to deliver global conclusions regarding materials choices, maintenance strategies, design lives, and other best-practice policies for achieving sustainability goals. In order to comprehensively quantify environmental footprints and effectively guide sustainability efforts, functional units need to be standardized, systems boundaries expanded, data quality and reliability improved, and study scopes broadened. Improving these deficiencies will allow future studies to perform equitable and comparable assessments, thus creating a synergistic set of literature that continuously builds upon itself rather than generates independent and isolated conclusions. These improvements will place the body of pavement LCA research in a better position to confidently lead private industry and government agencies on successful paths towards sustainability goals. [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]

Abstract: Metal recycling from automobiles, appliances and scrap steel occurs at dedicated metal shredding operations. Shredder residue (SR) consists of glass, rubber, plastics, fibers, dirt, and fines that remain after ferrous and nonferrous metals have been removed. The over 3 million tonnes of SR generated in the U.S. each year are managed by landfilling. Material recovery or energy recovery alternatives to landfilling can be beneficial because of conservation of non-renewable resources and reduction of waste disposal. In this study, the human health and environmental impacts of landfilling and three recovery options (supplemental fuel and mineral feed for cement manufacturing, hydrolysis to light fuel oil, and material recovery for recycling) were quantified and characterized using a life-cycle assessment (LCA) approach. Comparisons were carried out after characterization of emissions relative to potential impact categories of global warming, freshwater aquatic toxicity, acidification, eutrophication, human toxicity, photochemical oxidant creation, and terrestrial ecotoxicity. SR recovery in cement manufacturing could result in 1 million tonnes of coal conservation each year for the U.S. Compared to landfilling, recovery of the fuel and mineral value of SR in cement manufacturing provides net benefits for all environmental impact characteristics considered primarily due to avoided coal mining and landfilling impacts. As much as 750,000tonnes of recyclable materials could be recovered from SR. Material recovery system impact results were very sensitive to process energy requirements as well as the assumptions of percent recovery and the specific material types recovered. Hydrolysis of SR could produce 250 million gallons of light fuel oil equivalent per year. The hydrolysis process requires a significant amount of electricity, the impacts of which are somewhat offset by the avoided impacts of producing fuels from crude oil resources. Primarily due to high electricity consumption, both the hydrolysis and material recovery scenarios yielded trade-offs (some net benefits and some net higher impacts) compared to landfilling. The results of this end-of-life impact assessment showed that the supplement for cement manufacturing option was environmentally beneficial to the current practice of landfilling and appears better in comparison to the other management methods studied. [Copyright &y& Elsevier]

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]

The production of equipment and materials used for transportation facilities and services can have significant environmental effects. Considerable effort is expended to reduce such effects as efficiently and effectively as possible. In this paper, we estimate external environmental costs resulting from the production of common transportation equipment, materials, and services. These external cost estimates only include the effects from air emissions of conventional pollutants, including carbon monoxide, greenhouse gases (or global warming potential), volatile organics, sulfur dioxide, particulate matter, and nitrogen oxides. The estimates include all the direct and indirect supply chain emissions, such as electricity generation and mining. The cost estimates are uncertain and are likely to be underestimates of total external costs. However, the estimates should be useful for an initial assessment of the total social costs of transportation projects, and to indicate products and processes worthy of additional pollution prevention efforts. In particular, we find that additional external environmental costs may range from as low as 1% to as high as 45% for transportation services. External environmental costs of transportation equipment manufacturing range between 0.3 and 11%, while the external environmental costs of transportation construction and operation materials are estimated to vary between 1 and 100%. [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]

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]

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]

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]