Plant-derived sustainable fuel sources could contribute to near-term U.S. energy security and independence. However, weather conditions could greatly affect crop yields. In this study, researchers examined the effect of weather on biofuel production by comparing switchgrass and corn stover harvested after a year of major drought and after 2 years of normal precipitation. They found that the plants produced more sugar, but the sugar changed during pretreatment and produced toxic compounds rather than the desired fuels.