Biofuel research. Bottles of various products in the stages used to produce biodiesel from a plant oil. The initial oil is extracted from the seeds of the Jatropha curcas plant. The bottle at left is the product after the oil has passed through the methanol-refining stage. This is then passed through an alkali-refining stage to produce the oil at centre. This is then processed to produce the final product of biodiesel (right). This 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.