Wood gas. Biogas. Syngas. Landfill Gas. Renewable Natural Gas. Production and use of renewable carbon-based gaseous fuels have a history stretching back centuries and even millennia, providing heat, light and power to support both rural development and urban industrialization. The processes used to generate these gaseous fuels can be separated into two categories: thermochemical and biological, producing syngas and biogas, respectively.  Thermochemical conversion processes produce a synthesis gas, abbreviated as syngas, which is a mixture composed primarily of hydrogen and carbon monoxide, but may also contain carbon dioxide and methane.