There are two types of biomass: raw or primary biomass and secondary biomass. Raw biomass consists mainly of trees and shrubs from forests, or crops such as grasses, legumes, oilseeds, cereal grains, rushes etc. It can also be aquatic materials such as kelp, seaweed or algae. It can even be animal manure. Raw biomass is also obtained from energy crops that are grown specifically to provide biofuels. Typical energy crops include hybrid poplars, willows, grasses.