Total Environmental Impacts of Biofuels from Corn Stover Using a Hybrid Life Cycle Assessment Model Combining Process Life Cycle Assessment and Economic Input–Output Life Cycle Assessment

摘要

Studies on the environmental analysis of biofuels by fast pyrolysis and hydroprocessing (BFPH) have so far focused only onrnthe environmental impacts from direct emissions and have included few indirect emissions. The influence of ignoring somernindirect emissions on the environmental performance of BFPH has not been well investigated and hence is not reallyrnunderstood. In addition, in order to avoid shifting environmental problems from one medium to another, a comprehensivernassessment of environmental impacts caused by the processes must quantify the environmental emissions to all media (air,rnwater, and land) in relation to each life cycle stage. A well-to-wheels assessment of the total environmental impacts resultingrnfrom direct emissions and indirect emissions of a BFPH system with corn stover is conducted using a hybrid life cyclernassessment (LCA) model combining the economic input–output LCA and the process LCA. The Tool for the Reduction andrnAssessment of Chemical and other environmental Impacts (TRACI) has been used to estimate the environmental impacts inrnterms of acidification, eutrophication, global climate change, ozone depletion, human health criteria, photochemical smogrnformation, ecotoxicity, human health cancer, and human health noncancer caused by 1MJ biofuel production. Taking accountrnof all the indirect greenhouse gas (GHG) emissions, the net GHG emissions (81.8 g CO2 eq/MJ) of the biofuels are still less thanrnthose of petroleum-based fuels (94 g CO2 eq/MJ). Maize production and pyrolysis and hydroprocessing make majorrncontributions to all impact categories except the human health criteria. All impact categories resulting from indirect emissionsrnexcept eutrophication and smog air make more than 24% contribution to the total environmental impacts. Therefore, thernindirect emissions are important and cannot be ignored. Sensitivity analysis has shown that corn stover yield and bio-oil yieldrnaffect the total environmental impacts of the biofuels more significantly than the biomass transportation distance and biofuelrntransportation distance. Integr Environ Assess Manag 2018;14:139–149.