NEWLY ESTABLISHED DROUGHT-TOLERANT PLANTS AS RENEWABLE PRIMARY PRODUCTS AS SOURCE OF BIOENERGY
Drought-tolerant plants, also called xerophytes, have developed during evolution a huge spectrum of morphological, physiological and metabolic adaptations to a shortage of water. Due to global climate change large areas of land are threatened by increasing water limitation and therefore drought stress. In addition, energy becomes limiting for an increasing world population and renewable local energy sources are needed. The major food and fodder plants such as wheat, rice, corn and soybean do not show high drought tolerance. There are a number of genetic approaches to increase drought tolerance of these species; some of the genetically modified plants show good results in the greenhouse but when the plants are challenged by field conditions the promising results cannot be reproduced. One option to overcome the problem is to develop new crop plants from already highly drought-tolerant plants. We would like to focus on drought-tolerant plants grown on non-arable land as primary source of bioenergy. Some plants species are already locally used. Promising ecotypes could be used in breeding programs to improve the agricultural and economic values of these plants. For the selection and the development of new crops plants as sources for bioenergy the description of an optimal plant could be the starting point. It will be reported about promising preliminary results and economic uses of xerophytes from the genera Jatropha, Balanites and Euphorbia as new crop plants for the production of ethanol, biodiesel, biofuel, biogas and biomass-to-liquid. Finally, the pros and cons of plants as source of bioenergy in water-limited areas will be discussed.