A few different burnable gases can be made from biomass.
Wood gas, or smoke, can be made by heating biomass without air (pyrolysis).
Methane is made by anaerobic fermentation.
Syngas (Synthetic gas) is a mixture of Carbon Monoxide and Hydrogen. It is made by partially burning biomass, carbon or hydrocarbon with steam. It has less than half the energy density of methane.
|CH4 + H2O → CO + 3 H2|