Engine generator sets can be quickly started when wind speeds drop below levels required for wind power generation. The engine generator set provides a degree of flexibility in the choice of fuel burned. Most commonly diesel fuel is used, but this fossil fuel is a poor choice from a renewable energy perspective. Biodiesel is manufactured from oils extracted from soybeans. Producer gas is the product of gasifying any of a number of biomass materials, including wood chips, switchgrass or other grass crops, and agricultural residues such as cornstover or corn cobs.
Biogas gas is obtained from anaerobic digestion of high-moisture biomass such as manure.
Biodiesel will not degrade diesel engine performance. Biogas and producer gas contain contaminants that make them better suited for spark ignition engines. Since biodiesel is chemically similar to diesel fuel burned in vehicles today, it can be used in the conventional diesel engines without degradation in engine performance or engine components. However, biogas and producer gas are both relatively low-grade fuel that contain contaminants that may be harmful to an engine. Therefore spark ignition engines are often recommended for use with these fuels.