Biomass production by desert halophytes: alleviating the pressure on food production

Desert plants, i.e., plants that are adapted to grow under extreme desert conditions were studied with the aim of identifying new sources for energy crops. Such crops should not compete with conventional agriculture for valuable resources of fertile soil and fresh water. In order to obtain the high yields necessary for having an economically viable operation the plants must be amply irrigated, but can use reclaimed sewage and brackish water. Several types of salt cedar (Tamarix spp.) trees were grown in an experimental field at the Southern Arava Valley of Israel, under extreme desert conditions and were irrigated with reclaimed sewage and brackish water. Results have shown that such trees can be utilized under shortrotation type of agro-forestry to yield 26 to 52 tons/ha/y of organic biomass, that is not less then that obtained for common cash crops on arable land. An intensive screening of additional species of trees is under way with the aim to identifying more tolerant and faster growing lines. Another plant, the so called "pencil tree" (Euphorbia tirucalli), is being investigated as a possible source of secondary metabolites that can be converted into fuel substitutes.