Technical Abstract: Life cycle greenhouse gas emissions from bioenergy crops Bioenergy cropping systems could help offset greenhouse gas emissions from energy use, but quantifying that offset is complex. We conducted a life cycle assessment of a range of bioenergy cropping systems to determine the impact on net greenhouse gas emissions. The findings were compared with the life cycle emissions of gasoline and diesel. When compared to these fossil fuels, ethanol and biodiesel from corn rotations reduced gas emissions by 40%; reed canarygrass reduced emissions by 85%; and switchgrass and hybrid poplar reduced emissions by more than 115%.