Alternative fuels can substitute standard fuels directly, e. g., in coal-fired power plants, or indirectly, e. g., as gaseous or liquid fuels produced via thermochemical conversion. They range from untreated biomass and biogenic waste to fuels with biogenic components. The efficient use of biogenic alternative fuels is an important pillar in regard to the CO(2) reduction plan of the German Federal Government and its aim for a 100% renewable electric power supply. Based on a detailed fuel characterization the process specific requirements for co-firing in power plants are analyzed and the energetic efficiencies of various process chains are evaluated.