There has been a recent growth of interest in the potential for using straw as an energy source to generate electricity and/or heat. The energy balance of this process is important as a measure of the sustainability of such an activity, while the CO2 emitted and that saved by offsetting the need to produce energy by other means are also important, given the U.K.＇s obligations to reduce CO2 emissions. An existing methodology is adopted to calculate estimates of primary energy inputs and CO2 outputs. Results of calculations are presented and considered in the context of their implications for potential uses of straw represented by four scenarios. One scenario is the use of straw as a fuel in commercial scale power only, heat only and combined heat and power (CHP) plants. Overall, CHP production provides the most favourable energy and CO2 balances. Results are compared with those for alternative uses or disposal methods for straw, represented by other scenarios, and with those for producing electricity and/or heat by conventional means. Conclusions are drawn concerning the contributions to the energy and carbon balances of using straw as a fuel and recommendations are made for further work.