Well, according to the Wikipedia entry on Jatropha:"The plant yields more than four times as much fuel per hectare as soybean, and more than ten times that of maize (corn)."and later:"Goldman Sachs recently cited Jatropha curcas as one of the best candidates for future biodiesel production. However, despite its abundance and use as an oil and reclamation plant, none of the Jatropha species have been properly domesticated and, as a result, its productivity is variable, and the long-term impact of its large-scale use on soil quality and the environment is unknown. However, because jatropha is not edible, and because it can grow in harsh climates, it can be planted in areas where it won't compete for resources needed to grow food."