Keywords:combustion emission factor industrial ecology life cycle assessment meta-analysis subcritical supercritical Supporting information is available on the JIE Web site SummaryThis systematic review and harmonization of life cycle assessments (LCAs) of utility-scale coal-fired electricity generation systems focuses on reducing variability and clarifying central tendencies in estimates of life cycle greenhouse gas (GHG) emissions. Screening 270 references for quality LCA methods, transparency, and completeness yielded 53 that reported 164 estimates of life cycle GHG emissions. These estimates for subcritical pulverized, integrated gasification combined cycle, fluidized bed, and supercritical pulverized coal combustion technologies vary from 675 to 1,689 grams CO 2 -equivalent per kilowatt-hour (g CO 2 -eq/kWh) (interquartile range [IQR] = 890-1,130 g CO 2 -eq/kWh; median = 1,001) leading to confusion over reasonable estimates of life cycle GHG emissions from coal-fired electricity generation. By adjusting published estimates to common gross system boundaries and consistent values for key operational input parameters (most importantly, combustion carbon dioxide emission factor [CEF]), the meta-analytical process called harmonization clarifies the existing literature in ways useful for decision makers and analysts by significantly reducing the variability of estimates (−53% in IQR magnitude) while maintaining a nearly constant central tendency (−2.2% in median). Life cycle GHG emissions of a specific power plant depend on many factors and can differ from the generic estimates generated by the harmonization approach, but the tightness of distribution of harmonized estimates across several key coal combustion technologies implies, for some purposes, first-order estimates of life cycle GHG emissions could be based on knowledge of the technology type, coal mine emissions, thermal efficiency, and CEF alone without requiring full LCAs. Areas where new research is necessary to ensure accuracy are also discussed.

SummaryThis research provides a systematic review and harmonization of the life cycle assessment (LCA) literature of electricity generated from conventionally produced natural gas. We focus on estimates of greenhouse gases (GHGs) emitted in the life cycle of electricity generation from natural gas-fired combustion turbine (NGCT) and combined-cycle (NGCC) systems. The smaller set of LCAs of liquefied natural gas power systems and natural gas plants with carbon capture and storage were also collected, but analyzed to a lesser extent. A meta-analytical process we term "harmonization" was employed to align several system boundaries and technical performance parameters to better allow for cross-study comparisons, with the aim of clarifying central tendency and reducing variability in estimates of life cycle GHG emissions.Of over 250 references identified, 42 passed screens for technological relevance and study quality, providing a total of 69 estimates for NGCT and NGCC. Harmonization increased the median estimates in each category as a result of several factors not typically considered in the previous research, including the regular clearing of liquids from a well, and consolidated the interquartile range for NGCC to 420 to 480 grams of carbon dioxide equivalent per kilowatt-hour (g CO 2 -eq/kWh) and for NGCT to 570 to 750 g CO 2 -eq/kWh, with medians of 450 and 670 CO 2 -eq/kWh, respectively. Harmonization of thermal efficiency had the largest effect in reducing variability; methane leakage rate is likely similarly influential, but was unharmonized in this assessment as a result of the significant current uncertainties in its estimation, an area that is justifiably receiving significant research attention. Keywords:combined cycle combustion turbine fossil fuels industrial ecology life cycle assessment (LCA) meta-analysis Supporting information is available on the JIE Web site

This report catalogs by sector-buildings, transportation, industrial, and power-energy efficiency policies at the federal, state, and local levels, and identifies some prominent policy trends. Four key findings emerged from this report: 1) leadership on energy efficiency is necessary-and is found-at each level of government; 2) there is no widely accepted methodology for evaluating energy efficiency policies; 3) coordination among the three levels of government-and across sectors-is increasingly important, and there are opportunities to significantly improve policy performance through a unified strategy; and 4) there are efficiencies to be gained by informing policies in one sector with experience from others. Acknowledgments Executive SummaryThe benefits of energy efficiency are manifold-lower energy bills, improved air quality, reduced greenhouse gases, increased energy security, and a deferred need to invest in new infrastructure. Numerous studies document the prevalence of economically attractive, energy-saving opportunities that have yet to be widely adopted (McKinsey 2009, APS 2008, IEA 2009, IPCC 2007, Gigaton Throwdown 2009, UNEP 2007, WBCSD 2009). The failure to implement these opportunities indicates persistent market and other barriers to efficiency. Government policies should be designed to target these barriers and enable the benefits of energy efficiency to be realized.This report catalogues by sector-buildings, transportation, industrial, and power-energy efficiency policies at the federal, state, and local levels, and, where discernable, identifies policy trends. Four key findings emerged from this report: Leadership on energy efficiency is necessary-and is found-at each level of government.Policies initiated at state and local levels, within diverse political and economic contexts, can inform how similar policies can be employed and scaled-up in other places and jurisdictions. California, for example, has repeatedly designed efficiency programs that have served as models elsewhere. Federal leadership is also key, not only for the benefit of consumers and manufacturers, but also to provide the impetus for the country as a whole to realize its energy efficiency potential-to improve the economy, environment, and national security. There is no widely accepted methodology for evaluating energy efficiency policies.Measuring policy impact is critical for evaluating the effectiveness of policies at all levels of government. But such measurement is difficult due to the overlapping nature of policy implementation, the lack of coordination of intended impacts, and the challenge of calculating and attributing whether actual energy savings result from a particular policy. Coordination among the three levels of government-and across sectors-is increasingly important, and there are opportunities to significantly improve policy performance through a unified strategy.There is currently no comprehensive policy strategy for energy efficiency in the United States. Policies are conceived within narrow polit...

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This report catalogs by sector-buildings, transportation, industrial, and power-energy efficiency policies at the federal, state, and local levels, and identifies some prominent policy trends. Four key findings emerged from this report: 1) leadership on energy efficiency is necessary-and is found-at each level of government; 2) there is no widely accepted methodology for evaluating energy efficiency policies; 3) coordination among the three levels of government-and across sectors-is increasingly important, and there are opportunities to significantly improve policy performance through a unified strategy; and 4) there are efficiencies to be gained by informing policies in one sector with experience from others. Acknowledgments Executive SummaryThe benefits of energy efficiency are manifold-lower energy bills, improved air quality, reduced greenhouse gases, increased energy security, and a deferred need to invest in new infrastructure. Numerous studies document the prevalence of economically attractive, energy-saving opportunities that have yet to be widely adopted (McKinsey 2009, APS 2008, IEA 2009, IPCC 2007, Gigaton Throwdown 2009, UNEP 2007, WBCSD 2009). The failure to implement these opportunities indicates persistent market and other barriers to efficiency. Government policies should be designed to target these barriers and enable the benefits of energy efficiency to be realized.This report catalogues by sector-buildings, transportation, industrial, and power-energy efficiency policies at the federal, state, and local levels, and, where discernable, identifies policy trends. Four key findings emerged from this report: Leadership on energy efficiency is necessary-and is found-at each level of government.Policies initiated at state and local levels, within diverse political and economic contexts, can inform how similar policies can be employed and scaled-up in other places and jurisdictions. California, for example, has repeatedly designed efficiency programs that have served as models elsewhere. Federal leadership is also key, not only for the benefit of consumers and manufacturers, but also to provide the impetus for the country as a whole to realize its energy efficiency potential-to improve the economy, environment, and national security. There is no widely accepted methodology for evaluating energy efficiency policies.Measuring policy impact is critical for evaluating the effectiveness of policies at all levels of government. But such measurement is difficult due to the overlapping nature of policy implementation, the lack of coordination of intended impacts, and the challenge of calculating and attributing whether actual energy savings result from a particular policy. Coordination among the three levels of government-and across sectors-is increasingly important, and there are opportunities to significantly improve policy performance through a unified strategy.There is currently no comprehensive policy strategy for energy efficiency in the United States. Policies are conceived within narrow polit...