Biochemical conversion of biomass

Biomass arises in many forms and can be converted readily into SOLID, LIQUID or GASEOUS fuels. Most commonly, wood is chopped into chunks or chipped for ease of handling or even pelletised so that it can be pumped. Biomass can also be 'pyrolysed' or 'gasified' in specific ways to give liquids or fuel gases. All forms of biomass can in turn be burnt to raise HEAT (such as hot water or steam) or to produce ELECTRICITY or both in a combined heat and power (CHP) facility. Some biomass is far too wet to be burnt successfully and so biological fermentation processes are used. Here, using containers that exclude air, biomass is 'digested' to produce a methane rich gas called 'biogas' or fermented to produce alcohols or other specialised chemicals.
There is increasing interest in using biofuels for transport and the number of alcohol or biodiesel-fuelled vehicles around the world is growing.

Many believe that HYDROGEN used in FUEL CELLS will be the ultimate clean method of transport since using this fuel produces virtually nothing more then water vapour. Biomass may have a key role to play in the long term future through producing hydrogen directly by biological processing or through providing sustainable energy for other methods of production (e.g. electrolysis).

Thermochemical conversion technologies, like combustion, gasification and pyrolysis, are well suited for biomass feedstock material with relatively low moisture content. Even though the latest technological developments increase the limit of moisture content that can be present, for very wet biomass materials the only alternative for conversion into suitable energy carriers is biochemical conversion. The most common biochemical process to convert high-moisture biomass is anaerobic digestion, where bacteria produce biogas. Several liquid biofuels (bioethanol, biodiesel, biomethanol,...) can also be produced by biochemical conversion.

Biogas car		Biodiesel can be produced from rape seed oil		Small CHP plant on biogas in Switzerland