Jatropha is a flowering plant that has never been cultivated or domesticated to any great extent prior to interest in it as a biofuel. Most of the members of the Jatropha genus are succulents, which means they grown well in dry, nutrient poor environments.
There are somewhere on the order of 170 different species of Jatropha, which makes selecting a plant for the climate of a given region easier. Jatropha can be found in most tropical regions including Central and South America, India, Cambodia, the Philippines, and Indonesia.
The seeds of the Jatropha plant are contained within a large green pod. Each pod holds several black seeds about the size of a small grape. The seeds, in turn, contain 27 to 40% oil by weight. It is this oil that is attractive for conversion to biofuels like biodiesel. In fact, in some countries the oil is burned directly in lamps to produce light.
The other thing that makes Jatropha attractive is its low nutrient and land area requirements. Jatropha requires less land than corn, soybean, switchgrass, and almost every other biofuel feedstock. In fact, the only production systems that use less land area are algae and Camelina.
One of the problems that has been demonstrated with Jatropha is that even though the plant grows okay in poor climates, it does not produce a great deal of oil in those settings. As it turns out, decent soil is required to get Jatropha to produce the 27-40% oil content per seed. This means that it does, in fact, threaten the food supply if Jatropha is to be used for any substantial portion of our energy needs. It can probably be used to meet the needs of the aviation industry, but anything beyond that is going to impact the food supply and lead to drastic land use changes.
Approximately 2.7 million square kilometers of Jatropha would need to be harvested each year to meet the demands of the aviation industry. Given that the aviation industry makes up only 10% of the total consumption of crude oil, we can extrapolate a bit to find that we would need about 27 million square kilometers of land area to completely replace oil.
To put that into perspective, we would have to plant all of the country of Argentina in Jatropha just to meet the needs of the aviation industry. To meet all of our fuel needs, we would have to cover an area the size of the United States about three times over.
Besides the direct land use changes and impact this would have on the food supply, plowing under that amount of land would also lead to indirect land use changes that could release nearly 500 times more CO2 than using Jatropha for fuel would save us. Planting enough Jatropha to meet all of our energy needs would worsen global warming substantially.