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ABSTRACT Radiation dosimetry data for Three Mile Island are re-analyzed in order to obtain revised esti- mates of the noble gas releases and attendant population doses during the March 1979 accident. A statistical treatment, distinctive to the present analysis, of the field dosimetry data and their uncertainties, enables the extraction from sparse data of maximal information about the release rates and projected doses. The release pattern giving a best fit to the dosimeter data yields an estimate of 820 (-310 +220) PBq for the noble gas,activity released over the first day and a half of the accident. The corresponding estimate of population dose is 37 (-9 +7) person-Sv within 50 miles of the plant. The major uncertainties reflected in these estimates are due to the unknown,venting temperature of the release (which affects the plume rise), possible errors in the wind direction measurements, less than fully resolved release timing, and calibration errors for TLD response. These uncertainties are more precisely stated as well as greatly narrowed,in comparison with previous assessments of the acci- dent. The meteorological dispersion and dosimetry model applied for this analysis includes

This report was compiled during the academic year of 2019-2020 for the University of Michigan (U-M) President's Commission on Carbon Neutrality by the Mobility Electrification Subgroup. Through its work, the Mobility Electrification group investigated the benefits and challenges of shifting U-M's buses and other vehicles to electric battery technology, explore strategies to encourage electric vehicle (EV) use by U-M commuters through expansion of on-campus EV charging infrastructure. The report details the group's recommendations which focus on pursuing the transition to an electric Blue Bus fleet, expanding U-M EV charging infrastructure to support EV use by long-distance faculty and staff commuters, and developing and implementing an educational program to raise EV awareness, benefits, incentives, fuel savings, and charging availability. This publication is a result of work sponsored by the U-M President's Commission on Carbon Neutrality to inform the PCCN's final recommendations to U-M President Mark Schlissel. This publication does not reflect Commission-level recommendations and should not be interpreted as being recommendations of the PCCN nor carrying its endorsement.

Public support is growing for policy initiatives to spur a transition from a fossil to renewable energy portfolio in the electricity sector. Some utilities in the United States offer programs that allow consumers to voluntarily pay premiums (0.1–7.0 ¢/kWh) for electricity from renewable sources. However, it is unclear whether public support translates to paying for green electricity if given the option. Our analysis employs data from two national, longitudinal surveys on energy attitudes and willingness to pay for renewables to investigate whether environmental concerns and stated preferences for renewable energy translate to consumer behavior as measured through ratepayer participation in voluntary utility renewable energy programs known as utility green pricing. We find higher green pricing program participation rates in areas where consumers have stronger feelings about the environmental impacts of energy. Consumers in high-participation areas also have a higher stated willingness to pay for renewable energy, on average, than consumers in low-participation areas. We also find income, homeownership, and home value explain some of the difference between high- and low-participation programs. Further, program participation is lower in areas where utilities charge higher green pricing program premiums. These findings suggest that green power programs—such as utility green pricing—offer a market-based mechanism for consumers to realize their desire to purchase renewable energy. Policymakers may use these results to support further expansion of green power programs in areas where customers currently lack accessible and affordable options to act on their environmental beliefs and concerns.

A growing literature suggests that widespread travel conducted through driverless connected and automated vehicles (CAVs) accessed as a service, in contrast to those personally owned, could have significant impacts on the sustainability of urban transportation. However, it is unclear how the general public currently considers willingness to travel in driverless vehicles, and if they would be more comfortable doing so in one personally owned or one accessed as a service. To address this, we collected travel survey data by intercepting respondents on discretionary or social trips to four popular destinations in a medium-size U.S. city in the spring of 2017. After collecting data on how the respondent reached the survey site and the trip’s origin and destination, survey administrators then asked if respondents would have been willing to make their current trip in either a personally-owned driverless vehicle or through a driverless vehicle service. Over one-third expressed willingness to use both forms, while 31% were unwilling to use either. For those that considered only one, slightly more favored the personally-owned model. Consideration of an existing mobility service was consistently a positive and significant predictor of those that expressed willingness to travel in a driverless vehicle, while traveling downtown negatively and significantly influenced consideration of at least one form of driverless vehicle. These findings highlight the diverse public views about the prospect of integration of CAVs in transportation systems and raise questions about the assumption that travelers to central city locations would be early adopters of automated vehicle mobility services.

The use of bioenergy has grown rapidly in recent years, driven by policies partly premised on the belief that bioenergy can contribute to carbon dioxide (CO2) emissions mitigation. However, the experience with bioenergy production and the pressure it places on land, water, biodiversity, and other natural resources has raised questions about its merits. Recent studies offer a lesson: Bioenergy must be evaluated by addressing both the stocks and flows of the carbon cycle. Doing so clarifies that increasing the rate of carbon uptake in the biosphere is a necessary condition for atmospheric benefit, even before considering production-related lifecycle emissions and leakage effects due to land-use change. To maximize the role of the biosphere in mitigation, we must focus on and start with measurably raising rates of net carbon uptake on land—rather than seeking to use biomass for energy. The most ecologically sound, economical, and scalable ways to accomplish that task are by protecting and enhancing natural climate sinks. Rather than prioritizing bioenergy production, researchers and policymakers should pursue carbon management initiatives such as the reforestation project pictured here. Such efforts are much more likely to significantly reduce atmospheric CO2 concentrations in the near and medium term. Image courtesy of Lisa M. Dellwo (photographer). Hence, a major reprioritization of climate-related research, policy, and investment is urgently required, a move away from bioenergy and toward terrestrial carbon management (TCM). Researchers and policymakers must pursue actionable mitigation approaches that have the best chance of significantly reducing atmospheric CO2 concentrations in the near and medium term. When the biosphere is engaged, the emphasis should shift toward large-scale natural climate solutions, including the protection, restoration, and enhancement of forests and other terrestrial carbon sinks. As energy researchers and policy analysts have confronted the global warming problem over the past several decades, industrial-scale … [↵][1]1To whom correspondence should be addressed. Email: DeCicco{at}umich.edu. [1]: #xref-corresp-1-1

This research demonstrated quantitative methods of geospatial analysis applicable to carbon sequestration and storage in the conterminous United Sates. We identified national-scale NEP (net ecosystem production) changes for conversions to and from crop, and land in frequent conversion among forest, wetland, pasture and rangeland. The trend showed an increase in the margins of the Corn Belt states and coincided with land conversion from previous non-cropland to cropland in the United States. This research will not only improve the engineering understanding of carbon dioxide removal options involving the terrestrial biosphere, but will also inform decision-making in the carbon emission impacts. Therefore, it will provide a spatio-temporal reference for analyzing the national-level carbon exchange systems in the United States.

This study develops geospatial analysis of terrestrial carbon exchange for the conterminous United State and estimates large-scale NEP (net ecosystem production) dynamic from 2008 to 2013. We apply land-use and land-cover data in order to coherently include cropland, forest, wetland and other ecologically active landscapes in the mapping. Our results show a distribution of high harvest carbon release in the Corn Belt states, in addition to hot spots around the US in areas like Southern California and Arizona. Harvest carbon is low in areas in the southern United States, and central/southern Appalachian Mountains. We identify NEP changes for coupled agricultural, forest and other high-carbon-uptake ecosystems systems, conversions to and from crop, and land in frequent conversion among forest, wetland, pasture and rangeland. Findings from this study will provide important information to support and promote the co-production of science and decision-making.

Questions regarding the net effect of biofuels on carbon dioxide (CO2) emissions have been difficult to resolve because of methodological uncertainties. One method of choice is lifecycle assessment (LCA), which takes a fuel product system as its object of analysis. LCA uses a static system model, with carbon flows averaged over a defined "lifecycle". Although it may evaluate some carbon stock changes, the LCA convention of treating biogenic CO2 emissions as fully offset by the carbon embodied in a biofuel's feedstock renders its results independent of the dominant portion of carbon uptake on the land from which the feedstock is sourced. An application of material flow analysis termed annual basis carbon (ABC) accounting captures system dynamics and is fully sensitive to changes in carbon uptake. This paper compares the LCA and ABC methods, and contrasts their respective results for a case study of real-world biofuel production. It highlights the large impact of baseline carbon uptake, which can affect the sign of the results from either a likely decrease or a likely increase in net CO2 emissions even before considering economically-induced effects. Implications include the need for further methodological work, new program-scale model development, an empirical re-analysis of biofuel systems, and a reconsideration of existing public policies and research priorities.

The impact of substituting biofuels for fossil fuels on carbon dioxide (CO2) emissions has been debated for many years. A reason for the lack of resolution is that the method widely used to address the question, lifecycle analysis (LCA), is subjective. Its results irreducibly depend on untestable assumptions, notably those pertaining to system boundaries but also those for representing market effects. The best one can do is empirically constrain estimates of net CO2 impact using data that characterize important aspects of the overall system. Our 2016 paper, “Carbon balance effects of U.S. biofuel production and use,” took such an approach, using field data to estimate the direct CO2 exchanges for a circumscribed vehicle-fuel system over the 2005–2013 period of expanding US biofuel use. De Kleine and colleagues criticize our work because it does not follow LCA conventions, arguing in particular for the primacy of the assumption that biofuels are inherently carbon neutral. This response refutes their critique; it reminds readers why the lifecycle paradigm fails for a dynamic system involving the terrestrial carbon cycle, stresses the need to bound an analysis of key carbon exchanges, and explains why the circular logic of LCA can be so beguiling.

The use of liquid biofuels has expanded over the past decade in response to policies such as the U.S. Renewable Fuel Standard (RFS) that promote their use for transportation. One rationale is the belief that biofuels are inherently carbon neutral, meaning that only production-related greenhouse gas (GHG) emissions need to be tallied when comparing them to fossil fuels. This assumption is embedded in the lifecycle analysis (LCA) modeling used to justify and administer such policies. LCA studies have often found that crop-based biofuels such as corn ethanol and biodiesel offer at least modest net GHG reductions relative to petroleum fuels. Data over the period of RFS expansion enable empirical assessment of net CO 2 emission effects. This analysis evaluates the direct carbon exchanges (both emissions and uptake) between the atmosphere and the U.S. vehicle-fuel system (motor vehicles and the physical supply chain for motor fuels) over 2005–2013. While U.S. biofuel use rose from 0.37 to 1.34 EJ/yr over this period, additional carbon uptake on cropland was enough to offset only 37 % of the biofuel-related biogenic CO 2 emissions. This result falsifies the assumption of a full offset made by LCA and other GHG accounting methods that assume biofuel carbon neutrality. Once estimates from the literature for process emissions and displacement effects including land-use change are considered, the conclusion is that U.S. biofuel use to date is associated with a net increase rather than a net decrease in CO 2 emissions.

Fuel cells operating on hydrogen are among the propulsion technologies seeing research, development and demonstration as an option for meeting transportation needs in a world that faces severe limits on net anthropogenic CO 2 emissions. This article describes fuel cell vehicles, their principles of operation and major components while discussing the progress made in advancing the technology, the challenges it faces and its prospects for the future. Although various fuel cells can use different fuels, polymer electrolyte membrane (PEM) cells that use pure hydrogen are viewed as the best choice for motor vehicles. Fully capable automobiles using PEM fuel cells have been demonstrated and significant cost reductions are in sight for the vehicles themselves. Technical and economic hurdles remain for on-board hydrogen storage, refueling systems and hydrogen supply infrastructure. Fuel cell vehicles will also face competition from ongoing improvements in gasoline vehicles, including hybrid-electric designs, and in small car segments from battery electric vehicles. The economics of all such options will be evaluated in a context that includes increasing vehicle connectivity and automation as well as progress in the control of energy sector CO 2 emissions and programs for offsetting CO 2 emissions, particularly from liquid fuel use. Nevertheless, because of the promise they hold for meeting energy and climate challenges, fuel cell vehicles have captured the interest of governments and transportation industries around the world, and may become a viable choice for mobility systems of the future.

Carbon‐based liquid fuels are highly valued for transportation; they are the world's largest form of commercial energy and second largest source of anthropogenic carbon dioxide ( CO 2 ) emissions. Strategies to address their CO 2 emissions have been shaped by fuel cycle analysis ( FCA ), a version of lifecycle assessment that examines fuel products and their supply chains. FCA studies have diverse findings and large uncertainties. Disagreements are particularly sharp for biofuels, which are seen as key replacements for petroleum fuels. A critical reading of the evolving literature reveals problems of model structure, including system boundary misspecification, flawed carbon cycle representation, and use of a static framework to analyze dynamic systems. New analytic paradigms are needed for liquid fuels, given their tradability, the realities of the carbon cycle, and the implausibility of capturing carbon from mobile sources. Logical decomposition of options shows that, beyond measures to limit fuel demand, CO 2 emissions from liquid fuels must be balanced by increasing the rate of net carbon fixation. Further analysis and discussion are needed of carbon accounting methods, energy research priorities, ways to link CO 2 removal options to fuel‐related mitigation efforts, and the transportation elements of climate policy. WIREs Energy Environ 2015, 4:98–114. doi: 10.1002/wene.133 This article is categorized under: Bioenergy > Climate and Environment Energy and Climate > Economics and Policy Energy Research & Innovation > Science and Materials

My name is John DeCicco and I hold a doctorate in mechanical engineering from Princeton. Before joining the University of Michigan faculty in 2009 I worked professionally on energy issues since 1977, including 21 years at major environmental organizations. However, the findings I'm presenting today are my own professional views as an independent academic and do not reflect those of the University of Michigan, my past affiliations or funders.