In general, the biomass releases energy through its conversion into simpler com­pounds. This conversion can be carried out by chemical or biological methods. In this way, the biomass can be employed for producing solid, gaseous, or liquid bio­fuels. The biomass itself can be used as a solid biofuel for electricity production. In this case, the biomass undergoes combustion with or without coal as an auxiliary fuel (co-combustion). The biomass can also be used as a feedstock for producing gaseous fuels. For this, the biomass undergoes thermal treatment in the presence of a reduced amount of oxygen (partial oxidation) or by steam. The aim of these kinds of processes (pyrolysis, thermal gasification) is to obtain a gaseous fuel that can be mixed in a better way with the air leading to a cleaner and more complete combustion than is the case of the solid biomass. Moreover, the biomass can be converted into biogas, a mixture of CH4 and CO2, using anaerobic bacteria that assimilate the organic matter contained in the biomass forming more bacterial cells and releasing methane and carbon dioxide as a result of the methanogenic metabolism in absence of oxygen.