Examining the value of carbon sequestration in a dynamic model, the authors demonstrate that unless the sequestration is permanent, it is only a fraction of the value of emission abatement. The magnitude of the fraction increases in the duration of sequestration, the natural decay rate of carbon, and the discount rate. The authors also show that sinks should be used as early as possible in order to optimally reduce the carbon stock. Finally, the authors propose and assess three mechanisms for efficiently introducing sequestration into a carbon permit trading market: a pay-as-you-go system, a variable-length-contract system, and a carbon-annuity-account system. All are efficient, but all may not be equally feasible to implement.