Biomass is an attractive energy source under a carbon limited regime since the cycle of production and combustion can, potentially, be managed to release little net carbon. Another attractive technology is the capture and geologic storage of carbon dioxide (CCS), which has the potential to substantially reduce the costs of emissions mitigation. CCS options have most commonly been investigated in connection with fossil fuel use for electric power generation and hydrogen production. Here we examine the potential contribution of the combination of these two technologies, biomass CCS, to lower the cost of a climate stabilization policy. Sequestration of carbon from sustainably produced biomass would result in negative carbon emissions, which might be of substantial value in a carbon regime.