Tuesday, May 3, 2011
Life cycle assessment (LCA) of biofuel production is crucial in order to comply with regulations and to avoid or mitigate negative environmental impacts. Critical gaps in current LCA methodology, in particular a limited or absent consideration of biomass storage, may have dramatic impacts on net greenhouse gas (GHG) and other emissions. Our prior work shows that storage losses can increase the life-cycle GHG emissions of ethanol from corn stover by 20% to 100%. In this study, we examine the impact of multiple biomass storage and supply systems on life cycle GHG emissions from sweet sorghum and switchgrass grown in Tippecanoe County, Indiana. We assess potential dry matter losses, compositional changes, ethanol yield, and direct GHG emissions during storage of bales and silage in centralized and decentralized processing systems. Net emissions and energy use were calculated using the GREET model framework, into which we incorporated storage losses and direct emissions from biomass. Results highlight the impact of logistics, storage, and management decisions on the environmental impacts of second-generation biofuel feedstocks, and the potential benefits of dedicated energy crops for large-scale ethanol production.