After a review of a decade’s worth of biofuel research, Environmental Protection Agency scientists have concluded that knowledge gaps will likely prevent experts from adequately assessing the full environmental impact of increased biofuel use (Environ. Sci. Technol., DOI: 10.1021/es2023253). Caroline E. Ridley of EPA’s National Center for Environmental Assessment and her colleagues searched literature databases and identified more than 1,600 biofuel research citations from 2000 to 2009. They assigned each study to one of four themes, such as the environment or economics, and then to topics within those themes, such as greenhouse gas emissions or costs of production. The team found that the most common topics, with a few hundred papers each, were fuel production, feedstock production, and greenhouse gas emissions. At the bottom of the list, 80 studies examined how biofuel production affects biodiversity, and only 15 studied the human health impacts of increasing levels of air pollutants produced by burning bioethanol. Ridley’s team warns that these holes in basic research mean that expanded use of biofuels could lead to unanticipated problems. Ridley suggests the citation analysis could offer a guide to decisionmakers when allotting research funds for future studies.