Second-generation biofuels are fuels manufactured from various types of biomass. Biomass is a wide-ranging term meaning any source of organic carbon that is renewed rapidly as part of the carbon cycle. Biomass is derived from plant materials, but can also include animal materials.
Whereas first generation biofuels are made from the sugars and vegetable oils found in arable crops, second generation biofuels are made from lignocellulosic biomass or woody crops, agricultural residues or waste plant material (from food crops that have already fulfilled their food purpose). The feedstock used to generate second-generation biofuels thus either grows on arable lands, but are just byproducts of the actual harvest (main crop) or they are grown on lands which cannot be used to effectively grow food crops[19] and in some cases neither extra water or fertilizer is applied to them. Non-human food second generation feedstock sources include grasses, jatropha and other seed crops, waste vegetable oil, municipal solid waste and so forth.
This has both advantages and disadvantages. The advantage is that, unlike with regular food crops, no arable land is used solely for the production of fuel. The disadvantage is that unlike with regular food crops, it may be rather difficult to extract the fuel. For instance, a series of physical and chemical treatments might be required to convert lignocellulosic biomass to liquid fuels suitable for transportation.