Attempts to establish regenerative energy sources are still being rejected. Only since the oil crises, have regenerative energy sources been included in energy policy discussions. Compared with conventional sources of energy that have been used a much longer period of time, there appears to be a considerable lack of knowledge on regenerative sources of energy. In contrast, renewable sources of energy, such as irradiation and energies arising from it like wind, ambient heat, and bioenergy, have a very low energy density and therefore require a decentralized supply structure. Bio-energy is now accepted as having the potential to provide a major part of the projected renewable energy provisions of the future. There are three main routes to providing these bio-fuels, such as biological conversion, physical conversion, and thermal conversion. A number of primary and secondary products can be derived as gas, liquid and solid fuels, and electricity as well as a considerable number of chemicals. The basic conversion processes are summarized with their products and the main technical and non-technical barriers to implementation are identified.