LIFE-CYCLE ASSESSMENT OF NET GREENHOUSE-GAS FLUX FOR BIOENERGY CROPPING SYSTEMS

摘要: Bioenergy cropping systems could help offset greenhouse gas emissions, but quantifying that is complex. crops carbon dioxide emissions by converting atmospheric CO2 to organic C in crop biomass and soil, they also emit nitrous oxide vary their effects on soil oxidation of methane. Growing the requires energy (e.g., operate farm machinery, produce inputs such as fertilizer) so does harvested product usable fuels (feedstock conversion efficiency). The objective this study was quantify all these factors determine net effect several bioenergy greenhouse-gas (GHG) emissions. We used DAYCENT biogeochemistry model assess GHG fluxes yields for corn, soybean, alfalfa, hybrid poplar, reed canarygrass, switchgrass Pennsylvania, USA. results were combined with estimates fossil provide agricultural machinery fossil-fuel offsets from calculate each system considered. Displaced fuel largest sink, followed sequestration. N2O source. All considered provided sinks, even when assumed reach a new steady state sequestration not counted. Hybrid poplar .200 g CO2e-Cm � 2 yr 1 ethanol, .400 gasification electricity generation. Compared life cycle gasoline diesel, ethanol biodiesel corn rotations reduced ;40%, canarygrass ;85%, ;115%.