Dr. Thomas B. Reed shared the following on his Biomass Energy Foundation website:
This chart traces the various routes available for biomass conversion to fuels chemicals or heat. Sunlight plus carbons dioxide and water and fertilizer makes the biomass originally. It can occur naturally or be raised for food or forest products. Much of the available biomass is a by product of these activities. If the biomass is relatively dry (wood, MSW, etc.) it is a candidate for the thermal conversion processes, pyrolysis, gasification or combustion; if very wet it is more suited to the biological processes digestion or fermentation. Processes are available for converting biomass to fill all our human needs.