Bioenergy may include wood, wood waste, straw, manure, sugarcane, and many other products from a variety of agricultural processes. One of the interesting aspects of bioenergy is that it is often a by-product, residue or waste-product of other processes, such as farming, animal husbandry and forestry. Even industrial and municipal biological waste can be used as biofuels. However, costs are usually a limited factor. The research within bioenergy economics studies the link between biomass used for energy generation and the development of the energy sector. However, land use, existing biomass industries and relevant conversion technologies must be considered when evaluating suitability of developing bioenergy options. Bioenergy is a renewable energy source based on the carbon cycle, unlike other natural resources such as petroleum, coal, and nuclear fuels. Biomass can be converted to other usable forms of energy like methane gas or transportation fuels like ethanol and biodiesel. The methods employed include: optimisation; linear and non-linear programming; econometrics and; partial and general equilibrium.