Trees and shrubs in arid and semiarid regions, especially around the equator, are of vital importance for the human population in developing countries. Due to global warming, erosion, and droughts there is an alarming reduction in the number of trees. This has resulted in increased desertification. As an example, the Sahara desert and the Sahel area towards the south are expanding and causing havoc at the cocoa plantations in Ghana, Cameroon, and the Ivory Coast. In China, Beijing lies in the middle of a desert and in April the capital is covered under sandstorms.

Soil erosion is caused by wind and water, and droughts and floods as well as reduced water supply cause decreasing soil fertility. I have seen how in Ethiopia the fertile top soil is blown away by frequent desert storms.

Traditionally, shrubs and trees in the wild serve many purposes ([1], p. 6):

1. Food and drinks for humans (e. g. in hot climates you can buy a coconut on the street and drink fresh coconut milk, in Brazil street vendors press sugar juice from sugarcane before your eyes, and on the island of Lanzarote the cactus plant is cultivated because the juice is the feedstock for Campari!).

2. Browsing fodder for livestock and wildlife.

3. Beekeeping and honey production.

4. Sources of energy (firewood and charcoal).

5. Building and fencing material (skyscrapers in Asia could not be build without bamboo).

6. Fiber for cloth, rope, and handicrafts (my best jacket is made of bamboo!).

7. Tools for agriculture and cottage industry.

8. Handicraft, art, and religious objects.

9. Dye and tanning.

10. Drugs, medicinal, and veterinary uses) I remember an Indian woman saying: "my garden is my pharmacy”).

11. Shade and shelter for plants, animals, and humans.

12. Protection against erosion, and maintenance of soil fertility and productivity.

13. Water storage.

Now, however, agriculture has become a high-tech industry. I estimate that well over $20 billion has already been invested in research to develop enzymes and promote the cultivation of crops that adapt well to arid and semiarid conditions. We can now identify interesting plant species as energy sources. Some plants grow only around the equator, but other sources like waste, algae, or woodchips are not bound to tropical climates.

Scientists think that around 200 plant species can be processed into a diesel fuel substitute and even biokerosene. In Brazil, in the state-owned institute EMBRAPA, more than 5000 scientists are working in plant research. In particular, a few plants like sugarcane, Camelina, Pongamia, Crambe, and Jatropha have captured the interest of these scientists. In this plant category, the following properties ofJatropha curcas (the tropical physic nut) have won over great interest: it adapts well to semiarid marginal sites, its oil can be processed for use as a diesel fuel and jet fuel substitute, and it can be used for erosion control. The challenge is to domesticate the plant, improve the yields per acre or hectare, improve resistance against diseases, reduce water intake, optimize the plant’s DNA, and develop large amounts of feedstock.

Although a consensus exists that Jatropha is of Mexican and Central American origin, it has been cultivated for centuries as a hedge between properties in many other Latin American, Asian, and African countries. It has been documented that Jatropha was an important export product from the Cape Verde Islands between 1900 and 1950. Jatropha is not a new discovery. The Japanese army had its tanks running on crude Jatropha oil in Indonesia in World War II. Today, the trains between Mumbai and New Delhi run on Jatropha oil, with the plants growing along the railroad track!

The genus name Jatropha derives from the Greek iatros (doctor) and trophe (food), which implies medicinal uses ([1], p. 9). It has been used to treat indigestion.

Numerous vernacular names exist for J. curcas ([1], p. 9), including physic nut, purging nut (English); pourghere, pignon d’Inde (French); purgeernoot (Dutch); Purgiernuss, Brechnuss (German); purgueira (Portuguese); fagiola d’India (Italian); yu-lu-tzu (Chinese); and mundubi-assu (Brazil).

3.1.3