Renewable energy from biomass is conventionally thought to avoid emissions of the greenhouse gas CO2 by replacing the roles of fossil fuels. We show that if the off-gases produced during the fermentation of sugars to fuel-ethanol were captured and, for example, injected deep underground to keep them from the atmosphere, then the production of ethanol could lead to the net removal Of CO2 from the atmosphere in addition to avoiding gasolinerelated CO2 emissions by using the ethanol as a transportation fuel. We give estimates of net CO2 emissions for current systems for the production of fuel-ethanol, these systems modified to sequester fermentation CO2, and gasoline-related CO2 emission offsets. We consider future developments that might affect the scope and economic feasibility of the sequestration of fermentation CO2. © 2004 Elsevier Ltd. All rights reserved.