Biomass can be converted into gas by heating at 1300°C in an oxygen-limited atmos­phere. The gas produced contains mainly hydrogen, carbon monoxide, methane, carbon dioxide and nitrogen and can be used in a boiler or turbine for the generation

of heat, steam or electricity. Small-scale gasification systems (up to 100 MWth; mega­watts thermal) have been developed for heat and power systems. Small fixed-bed gasifiers linked to diesel or gas engines (100-200 kW) have an electrical efficiency of 15-20% but as yet have not been installed. The variations in the biomass used for gasi­fication makes the small systems difficult to operate. Larger gasifiers over 100 MWth use a variety of systems, including circulating fluidized beds, atmospheric gasifiers (ACFB), integrated gasification/combined cycle (IGCC) (Faaij, 2006). An example of simple-cycle gas turbine and biomass integrated gasification combined cycle (BIGCC) is shown in Fig. 4.7. The efficiency of the simple-cycle gas turbine can be improved from 40 to 60% with a combined cycle turbine system (Rukes and Taud, 2004).