Once the feedstock for biofuel has been harvested, it must be processed. Two processing techniques have been approved so far — biomass to liquid (BtL) and hydroprocessed esters and fatty acids (HEFA). In the HEFA process, biomass such as algae, jatropha or camelina are pressed to extract the oils inside. These plant oils are then refined into jet fuel, with the remaining plant material converted for other uses, such as for fertilizer or animal feed. The BtL process, meanwhile, breaks down the feedstock through gasification, a process during which the biomass is heated to extremely high temperature, cracking the molecules and producing gases. The gas is converted to liquid fuel through the Fischer-Tropsch process.