Xerophytic species evaluated for renewable energy resources

Previously, the USDA Northern Regional Research Center has examined 600 plant species in 88 families for their multipurpose, energy-producing potential. About three-fourths of these species have been from central and southern Illinois, but only about 2% have been from arid or semiarid regions of the United States. For this report, 100 species collected from Arizona were evaluated, bringing the total number of species evaluated at this Center to 700 in 96 families. Plant specimens were analyzed for yields of fractions referred to as "oil," "polyphenol," "hydrocarbon," and protein and were examined for botanical characteristics. Oil and hydrocarbon fractions of selected species were partially characterized. Ten species gave high yields of oil and/or polyphenol. For example, Asclepias linaria yielded 8.7% oil (dry, ash-free sample basis) + 11.7% polyphenol (1.9% hydrocarbon). Rhus choriophylla yielded 7.0% oil + 20% polyphenol (0.4% hydrocarbon) and Juglans major yielded 7.0% oil + 9.4% polyphenol (0.2% hydrocarbon). Pittosporum tobira gave the highest yield of hydrocarbon (2.3%). Fourteen species contained at least 18% protein. In general, the percentages of species yielding substantial amounts of oil and/or polyphenol were considerably higher for the Arizona species than for those 600 species previously analyzed. Complete analytical data are presented for 38 species and are discussed in relationship to the 600 species previously reported.