Gasification turns solid or liquid biomass material into a clean burning gas fuel. How does this happen? In thermal gasification, the hydrocarbons that make up the biomass material are heated, causing them to breakdown through pyrolysis into gases, liquids and char. The gases with lower ignition temperatures then begin to burn, combining with any oxygen present and generating more heat. As the temperature of the biomass increases, carbon char freed by the pyrolysis also begins to combine with oxygen, producing even greater heat. This describes the beginning of both the combustion and the gasification of biomass. In gasification, though, the amount of oxygen is restricted so that the gasses that are produced are not allowed to continue to fully combust. Instead, they are collected, cooled and cleaned.

The gas produced through this gasification process is known as producer gas. Its burnable components are carbon monoxide, hydrogen and methane with minor amounts of other hydrocarbons such as propane and ethane. The noncombustible components of the producer gas are mainly carbon dioxide, nitrogen and water vapor. Producer gas typically has an energy density of approximately 200 BTU/cu ft, which is about one fifth of the energy density of natural gas. However, since these gases exist in the gasification reaction at elevated temperatures, some of the energy of that reaction can be used to further enhance the energy density of the producer gas.

The heat from this reaction can be used to breakdown water vapor that is in the gas, freeing oxygen and hydrogen. The added hydrogen increases the energy density and therefore the useful value of the producer gas. With a high enough level of hydrogen in the gas, this hydrogen can be economically separated from the remaining gases to also be used as a liquid fuel.