Biomass resources can be classified according to the supply sector, as shown in the table below. One basic difference between bioenergy and other renewable forms of energy (hydro, wind, solar) is that in the first case, the primary resource must be produced and/or collected, with its corresponding cost, while for the other systems, the "fuel" (water, wind, solar radiation) is available for free.

Biomass is a primary source of energy for close to 2.4 billion people in developing countries. Easily available to many of the world’s poorest regions, biomass provides vital and affordable energy for cooking and space heating.

The share of biomass energy in total energy consumption varies across developing countries, but generally the poorer the country, the greater its reliance on traditional biomass resources (see figure).

Over two billion people cook by direct combustion of biomass, primarily in rural areas. Such traditional use of biomass fuels is typically inefficient, relying largely on low-cost sources such as forests and other natural vegetation.

Biomass utilization in industrialized countries contrasts sharply with that in developing countries. On average, biomass accounts for 3 or 4% of total energy use in the former, although in countries with supportive policies (e.g., Sweden; Finland; Austria) the biomass contribution reaches 15 to 20%. Most biomass in industrialized countries is converted into electricity and process heat in cogeneration systems.