MODEL RELEASED. Biofuel research. Dr George Wake in his laboratory, holding samples of a plant oil (dark brown, left) and biodiesel (yellow, right). The oil is extracted from Jatropha curcas seeds (bottom) and refined using equipment like that at right to produce the biodiesel. Biodiesel is a form of biofuel that is suitable for use in a conventional diesel engine. Biofuels such as biodiesel are clean, renewable sources of energy, and have less impact on the environment than fossil fuels such as diesel, petrol and coal.