Basic elements of biomass accumulation Bioenergy from crops is a renewable and sustainable source of energy that may be close to carbon neutral, although greenhouse gas mitigation potential and carbon footprints of these crops may vary widely. Solar energy drives the growth of green plants, in the process of photosynthesis, resulting in the production of simple and complex carbohydrates. These carbohydrates can be used as feedstock in a plethora of thermochemical, biological and gasification processes, producing a whole range of energy sources. It has been estimated that some two billion people rely on biomass for primary energy of cooking and space heating. This is mostly in the developing countries of Africa, Asia and Latin America, and wood fuels account for some 14 per cent of global primary energy (OECD and FAO, 2007).