Ethan Warner

Renewable Energy in the Context of Sustainable Development

See next page for additional authors Follow this and additional works at: http://ecommons.udayton.edu/phy_fac_pub Part of the Environmental Education Commons, Environmental Health and Protection Commons, Environmental Indicators and Impact Assessment Commons, Environmental Monitoring Commons, Natural Resource Economics Commons, Natural Resources and Conservation Commons, Natural Resources Management and Policy Commons, Oil, Gas, and Energy Commons, Other Environmental Sciences Commons, Sustainability Commons, and the Water Resource Management Commons

Life Cycle Greenhouse Gas Emissions of Nuclear Electricity Generation Systematic Review and Harmonization

A systematic review and harmonization of life cycle assessment (LCA) literature of nuclear electricity generation technologies was performed to determine causes of and, where possible, reduce variability in estimates of life cycle greenhouse gas (GHG) emissions to clarify the state of knowledge and inform decision making. LCA literature indicates that life cycle GHG emissions from nuclear power are a fraction of traditional fossil sources, but the conditions and assumptions under which nuclear power are deployed can have a significant impact on the magnitude of life cycle GHG emissions relative to renewable technologies. Screening 274 references yielded 27 that reported 99 independent estimates of life cycle GHG emissions from light water reactors (LWRs). The published median, interquartile range (IQR), and range for the pool of LWR life cycle GHG emission estimates were 13, 23, and 220 grams of carbon dioxide equivalent per kilowatt‐hour (g CO‐eq/kWh), respectively. After harmonizing methods to use consistent gross system boundaries and values for several important system parameters, the same statistics were 12, 17, and 110 g CO‐eq/kWh, respectively. Harmonization (especially of performance characteristics) clarifies the estimation of central tendency and variability. To explain the remaining variability, several additional, highly influential consequential factors were examined using other methods. These factors included the primary source energy mix, uranium ore grade, and the selected LCA method. For example, a scenario analysis of future global nuclear development examined the effects of a decreasing global uranium market‐average ore grade on life cycle GHG emissions. Depending on conditions, median life cycle GHG emissions could be 9 to 110 g CO‐eq/kWh by 2050.

Modeling biofuel expansion effects on land use change dynamics

Increasing demand for crop-based biofuels, in addition to other human drivers of land use, induces direct and indirect land use changes (LUC). Our system dynamics tool is intended to complement existing LUC modeling approaches and to improve the understanding of global LUC drivers and dynamics by allowing examination of global LUC under diverse scenarios and varying model assumptions. We report on a small subset of such analyses. This model provides insights into the drivers and dynamic interactions of LUC (e.g., dietary choices and biofuel policy) and is not intended to assert improvement in numerical results relative to other works. Demand for food commodities are mostly met in high food and high crop-based biofuel demand scenarios, but cropland must expand substantially. Meeting roughly 25% of global transportation fuel demand by 2050 with biofuels requires >2 times the land used to meet food demands under a presumed 40% increase in per capita food demand. In comparison, the high food demand scenario requires greater pastureland for meat production, leading to larger overall expansion into forest and grassland. Our results indicate that, in all scenarios, there is a potential for supply shortfalls, and associated upward pressure on prices, of food commodities requiring higher land use intensity (e.g., beef) which biofuels could exacerbate.

2016 Survey of Non-Starch Alcohol and Renewable Hydrocarbon Biofuels Producers

In order to understand the status of the industry for non-starch ethanol and renewable hydrocarbon biofuels as of the end of calendar year 2013, the National Renewable Energy Laboratory (NREL) conducted the first of what is anticipated to be an annual survey of U.S. non-starch ethanol and renewable hydrocarbon biofuels producers. This report presents the results of this initial survey and describes the survey methodology. Subsequent surveys will report on the progress over time of the development of these facilities and companies.

Potential Reductions in Emissions and Petroleum Use in Transportation: Perspectives from the Transportation Energy Futures Project

The use of energy-efficient technologies and renewable energy sources in transportation could reduce petroleum use and greenhouse gas emissions, but these approaches may face challenges in consumer adoption, infrastructure requirements, and resource constraints. The Transportation Energy Futures project of the U.S. Department of Energy reviewed opportunities for significant reductions in petroleum use and greenhouse gas emissions. On the basis of that review, a diverse set of strategies is explored: reduced energy intensity of transportation modes, lower use intensity of motorized transport, and reduced carbon or petroleum intensity through the use of electricity and hydrogen from renewable energy as well as the use of biofuels. Energy efficiency and demand-side approaches could stop the growth in total transportation energy. In the light-duty vehicle sector, growth in energy use already is projected to flatten; the deployment of technologies for energy efficiency could limit growth in the non-light-duty sector. Travel reduction and built environment changes could moderate personal transportation demand. Freight mass reductions and mode switching could slow or stabilize freight demand. Vehicles using electricity or hydrogen could enable access to renewable energy resources other than biomass. Challenges in fueling infrastructure expansion and market uptake of advanced vehicles are considered. Competition for biomass also is explored, considering markets for electricity, gasoline, diesel, jet fuel, and bunker fuel. The potential for the implementation of these strategies to displace U.S. petroleum use and reduce greenhouse gas emissions in the transportation sector is discussed along with the barriers to realizing this potential in the market.

Estimating biofuel feedstock water footprints using system dynamics

Increased biofuel production has prompted concerns about the environmental tradeoffs of biofuels compared to petroleum-based fuels. Biofuel production in general, and feedstock production in particular, is under increased scrutiny. Water footprinting (measuring direct and indirect water use) has been proposed as one measure to evaluate water use in the context of concerns about depleting rural water supplies through activities such as irrigation for large-scale agriculture. Water footprinting literature has often been limited in one or more key aspects: complete assessment across multiple water stocks (e.g., vadose zone, surface, and ground water stocks), geographical resolution of data, consistent representation of many feedstocks, and flexibility to perform scenario analysis. We developed a model called BioSpatial H2O using a system dynamics modeling and database framework. BioSpatial H2O could be used to consistently evaluate the complete water footprints of multiple biomass feedstocks at high geospatial resolutions. BioSpatial H2O has the flexibility to perform simultaneous scenario analysis of current and potential future crops under alternative yield and climate conditions. In this proof-of-concept paper, we modeled corn grain (Zea mays L.) and soybeans (Glycine max) under current conditions as illustrative results. BioSpatial H2O links to a unique database that houses annual spatially explicit climate, soil, and plant physiological data. Parameters from the database are used as inputs to our system dynamics model for estimating annual crop water requirements using daily time steps. Based on our review of the literature, estimated green water footprints are comparable to other modeled results, suggesting that BioSpatial H2O is computationally sound for future scenario analysis. Our modeling framework builds on previous water use analyses to provide a platform for scenario-based assessment. BioSpatial H2Os system dynamics is a flexible and user-friendly interface for on-demand, spatially explicit, water use scenario analysis for many US agricultural crops. Built-in controls permit users to quickly make modifications to the model assumptions, such as those affecting yield, and to see the implications of those results in real time. BioSpatial H2Os dynamic capabilities and adjustable climate data allow for analyses of water use and management scenarios to inform current and potential future bioenergy policies. The model could also be adapted for scenario analysis of alternative climatic conditions and comparison of multiple crops. The results of such an analysis would help identify risks associated with water use competition among feedstocks in certain regions. Results could also inform research and development efforts that seek to reduce water-related risks of biofuel pathways.