Biomass is a collective name for different types of sustainable raw materials that can be used to generate renewable electricity. Most forms of green energy are obviously renewable: a wind turbine produces nothing but 100% renewable electricity. But that is not always the case with energy generated from biomass. Fossil fuels may be used in the same plant, along with biomass. The residual heat may also be used. That is why there are extra requirements for labelling energy generated from biomass.