Environmental and Economic Performance of Hybrid Power-to-Liquid and Biomass-to-Liquid Fuel Production in the United States.

Power-to-liquids are a class of liquid drop-in fuels produced from electricity and carbon dioxide as the primary process inputs, which have the potential to reduce transportation's climate impacts. We quantify the economic and life cycle environmental characteristics of four electrofuel technology pathways that rely on the Fischer-Tropsch synthesis but produce synthesis gas via different schemes: power-to-liquid (PtL) via electrolysis and a reverse water gas shift (RWGS) reaction; PtL via co-electrolysis; gasification of biomass-to-liquid (BtL); and a hybrid power- and biomass-to-liquid (PBtL) pathway. The results indicate that the hybrid PBtL pathway is the most environmentally and economically promising option for electrofuel production, with results highly dependent on input electricity source characteristics such as cost and emissions. The carbon intensities of electricity generation that must not be exceeded for electrofuels to have lower life cycle emissions than conventional diesel are 222, 116, and 143 gCO2e/kWh for PBtL, PtL electrolysis + RWGS, and PtL co-electrolysis, respectively. We characterize the PBtL pathway in more detail by combining spatially resolved data on biomass cultivation, electricity generation, and cost-optimized hydrogen production from renewable electricity in the United States (US). We find that the private emissions abatement cost for PBtL fuels varies between 740 and 2000 $/tCO2e, depending primarily on the location of fuel production.

Air pollution impacts of COVID-19-related containment measures.

Responses to the COVID-19 outbreak resulted in one of the largest short-term decreases in anthropogenic emissions in modern history. To date, there has been no comprehensive assessment of the impact of lockdowns on air quality and human health. Using global satellite observations and ground measurements from 36 countries in Europe, North America, and East Asia, we find that lockdowns led to reductions in NO2 concentrations globally, resulting in ~32,000 avoided premature mortalities, including ~21,000 in China. However, we do not find corresponding reductions in PM2.5 and ozone globally. Using satellite measurements, we show that the disconnect between NO2 and ozone changes stems from local chemical regimes. The COVID-related lockdowns demonstrate the need for targeted air quality policies to reduce the global burden of air pollution, especially related to secondary pollutants.