Currently, 77% of Brazilian biodiesel is made from soya beans, 21% from animal fat and 2% from other sources, including mamona (the seed of the castor oil plant), sunflowers, dendê (palm oil), cotton and jatropha. Soya beans account for between 40-60% of the cost of bio-diesel production, Laviola says, and a weed such as jatropha - which does not compete with food crops - could be a solution.