There are a number of technological options available to make use of a wide variety of biomass types as a renewable energy source. Conversion technologies may release the energy directly, in the form of heat or electricity, or may convert it into another form, such as liquid biofuel or combustible biogas. Various methods of conversion of biomass into useful energy gain can be explained as follows:

2.4.1 Direct Combustion Processes

Feedstocks used are often residues such as woodchips, sawdust, bark, bagasse, straw, municipal solid waste (MSW) and wastes from the food industry. Direct combustion furnaces can be divided into two broad categories and are used for producing either direct heat or steam. Dutch ovens, spreader-stoker and fuel cell furnaces employ two stages. The first stage is for drying and possible partial gasification, and the second is for complete combustion. More advanced versions of these systems use rotating or vibrating grates to facilitate ash removal, with some requiring water cooling.