An ugly, smelly weed called jatropha may be another piece of the energy puzzle. According to a Slashdot article, the weed produces a seed that can have up to 40% oil content, which can be easily converted to a biofuel for diesel engines. Jatropha apparently grows easily, requires little water or fertilizer, and can be grown on marginal lands that would not support energy intensive crops like corn and soybeans.