Search

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.

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.

In 2015, California established a mandate that requires on-road greenhouse gas (GHG) emissions to be reduced by 40% below 1990 levels by 2030. We explore the feasibility of meeting this goal by large-scale commercialization of drop-in biofuels. Drop-in biofuels, although not clearly defined, are a class of fuels that can be produced from biomass and blended with either crude oil or finished fuels without requiring equipment retrofits. This article focuses on thermochemical routes at or near commercialization. We provide a bottom-up, spatially explicit cost analysis to evaluate whether California can meet its 2030 GHG reduction target with drop-in fuels alone. A takeaway from our analysis is that drop-in fuels, if their performance is consistent with small-scale and simulated results, can be viable low-carbon substitutes for gasoline and diesel. We find that California can meet, and even exceed, its 2030 GHG emissions target for on-road vehicles with drop-in biofuels alone, but this requires use of biomass resources located outside the state. Meeting the 40% reduction target in a cost-effective manner requires pyrolysis of herbaceous agricultural residues (96% of total fuel output) and the conversion of woody residues via methanol-to-gasoline (4%). This scale of production would require 58 million metric tons of biomass feedstock, or 20% of total available biomass residues in the United States. For comparison, California is responsible for 11% of transportation-related petroleum consumption in the US. The approximately 5 billion gallons (19 billion liters) per year of drop-in fuel would displace 30% of gasoline and 60% of diesel demand in California. If electricity offset credits are eliminated, the target can be met with a similar scale of production, but methanol-to-gasoline becomes the dominant route (>99%), biomass requirements increase by 33%, and average production costs increase by 20%. Following this policy pathway would increase national biofuel production by 30% relative to 2015 production levels.

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: 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]

Goal, Scope and Background. This study provides a life-cycle inventory of air emissions (CO2, NOx, PM10, and CO) associated with the transportation of goods by road, rail, and air in the U.S. It includes the manufacturing, use, maintenance, and end-of-life (EOL) of vehicles, the construction, operation, maintenance, and EOL of transportation infrastructure, as well as oil exploration, fuel refining, and fuel distribution. Methods. The comparison is performed using hybrid life-cycle assessment (LCA), a combination of process-based LCA and economic input-output analysis-based LCA (EIO-LCA). Results are summed by means of a common functional unit of grams of air pollutant per ton-mile of freight activity. Results and Discussion. Results show that the vehicle use phase is responsible for approximately 70% of total emissions of CO2 for all three modes. This confirms that tailpipe emissions underestimate total emissions of freight transportation as infrastructure, pre-combustion, as well as vehicle manufacturing and EOL account for a sizeable share of total emissions. Depending on mode and pollutant, differences between tailpipe emissions and total systemwide emissions can range from only 4% for road transportations CO emissions to an almost tenfold difference for air transportations PM10 emissions. Conclusion. Rail freight has the lowest associated air emissions, followed by road and air transportation. Depending on the pollutant, rail is 50–94% less polluting than road. Air transportation is rated the least efficient in terms of air emissions, partly due to the fact that it carries low weight cargo. It emits 35 times more CO2 than rail and 18 times more than road transportation on a ton-mile basis. It is important to consider infrastructure, vehicle manufacturing, and pre-combustion processes, whose life-cycle share is likely to increase as new tailpipe emission standards are enforced. Recommendation and Outlook. Emission factors, fuel efficiency, and equipment utilization contribute the most to uncertainty in the results. Further studies are necessary to address all variables that influence these parameters, such as road grade, vehicle speed, and vehicle weight. A focus on regional variation, EOL processes, fuel refining processes, terminals, as well as more accurate infrastructure allocation between freight and passenger transportation would strengthen the model. [ABSTRACT FROM AUTHOR]