• Energy Research

Coupling renewable electricity with corn stover biomass using electrocatalytic hydrogenation of pyrolysis bio-oil is potentially economically competitive vs. cellulosic ethanol.

AbstractThis Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) considers the interactive effects of solar UV radiation, global warming, and other weathering factors on plastics. The Assessment illustrates the significance of solar UV radiation in decreasing the durability of plastic materials, degradation of plastic debris, formation of micro- and nanoplastic particles and accompanying leaching of potential toxic compounds. Micro- and nanoplastics have been found in all ecosystems, the atmosphere, and in humans. While the potential biological risks are not yet well-established, the widespread and increasing occurrence of plastic pollution is reason for continuing research and monitoring. Plastic debris persists after its intended life in soils, water bodies and the atmosphere as well as in living organisms. To counteract accumulation of plastics in the environment, the lifetime of novel plastics or plastic alternatives should better match the functional life of products, with eventual breakdown releasing harmless substances to the environment.

The manuscript reviews the research on economic and environmental benefits of second-life electric vehicle batteries (EVBs) use for energy storage in households, utilities, and EV charging stations. Economic benefits depend heavily on electricity costs, battery costs, and battery performance; carbon benefits depend largely on the electricity mix charging the batteries. Environmental performance is greatest when used to store renewable energy such as wind and solar power. Inconsistent system boundaries make it challenging to compare the life cycle carbon footprint across different studies. The future growth of second-life EVB utilization faces several challenges, including the chemical and electrical properties and states of health of retired EVBs, the rapidly decreasing costs of new batteries, and different operational requirements. Measures to mitigate these challenges include the development of efficient diagnostic technologies, comprehensive test standards, and battery designs suitable for remanufacturing. Further research is needed based on real-world operational data and harmonized approaches.

We consider energy density, toxicity, emissions, ease of handling, and flammability and find that with a possible exception in marine applications the outlook for future use of ammonia as a transportation fuel is poor.

Ethanol blending into gasoline yields a wide range of octane rating responses, most frequently synergistic (i.e., greater than expected by linear blending), but also linear or antagonistic. A new a...

Expanded use of novel oil extraction technologies has increased the variability of petroleum resources and diversified the carbon footprint of the global oil supply1. Past life-cycle assessment (LCA) studies overlooked upstream emission heterogeneity by assuming that a decline in oil demand will displace average crude oil2. We explore the life-cycle greenhouse gas emissions impacts of marginal crude sources, identifying the upstream carbon intensity (CI) of the producers most sensitive to an oil demand decline (for example, due to a shift to alternative vehicles). We link econometric models of production profitability of 1,933 oilfields (~90% of the 2015 world supply) with their production CI. Then, we examine their response to a decline in demand under three oil market structures. According to our estimates, small demand shocks have different upstream CI implications than large shocks. Irrespective of the market structure, small shocks (-2.5% demand) displace mostly heavy crudes with ~25-54% higher CI than that of the global average. However, this imbalance diminishes as the shocks become bigger and if producers with market power coordinate their response to a demand decline. The carbon emissions benefits of reduction in oil demand are systematically dependent on the magnitude of demand drop and the global oil market structure.

AbstractInterest and investment in electric vertical takeoff and landing aircraft (VTOLs), commonly known as flying cars, have grown significantly. However, their sustainability implications are unclear. We report a physics-based analysis of primary energy and greenhouse gas (GHG) emissions of VTOLs vs. ground-based cars. Tilt-rotor/duct/wing VTOLs are efficient when cruising but consume substantial energy for takeoff and climb; hence, their burdens depend critically on trip distance. For our base case, traveling 100 km (point-to-point) with one pilot in a VTOL results in well-to-wing/wheel GHG emissions that are 35% lower but 28% higher than a one-occupant internal combustion engine vehicle (ICEV) and battery electric vehicle (BEV), respectively. Comparing fully loaded VTOLs (three passengers) with ground-based cars with an average occupancy of 1.54, VTOL GHG emissions per passenger-kilometer are 52% lower than ICEVs and 6% lower than BEVs. VTOLs offer fast, predictable transportation and could have a niche role in sustainable mobility.