Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2002
Publication Date: N/A
Interpretive Summary: The exponential growth in the number of people, increases in the number of vehicles, and the sophistication of technology has increased an awareness of the need to discover new energy sources from diverse underutilized plant species. Hydrocarbons in plants, such as natural rubber (polyisoprene) have chemical structures similar to many hydrocarbons derived from petroleum. Natural rubber is the most common hydrocarbon polymer found in green plants. Low molecular weight natural rubber would be of interest as a plastic additive (processing aid) to rubber mixes, for making cements (adhesives), and if economically feasible as a hydrocarbon feed stocks. Such materials when fractured, will produce hydrocarbons of lower molecular weight which can be used as alternative energy sources for fuel and or chemical raw materials that are used in the manufacturing of a large number of products. Plants as a source of hydrocarbon and rubber have been investigated periodically for many years. However, during the last few decades the need for additional sources has resurfaced since the world production of natural rubber is expected to be insufficient for the demand. Our objective was to do a large scale screening of plants growing in the Western Ghats Region to assess their hydrocarbon production and the type of isoprene compounds present. Three species had 3% or more of hydrocarbons. Sarcostemma brevistigma had the highest concentration of hydrocarbons with 3.6%. Caralluma attenuata had the second highest concentration of hydrocarbons with 3.4%, while Jatropha multifida had 3%. The gross heat values of the screened species were comparable to well-known natural fossil fuel sources. The hydrocarbon fraction of Marsedenia volubilis had a gross heat value of 9739 cal/g, which is close to the calorific value of Mexican fuel oil. All the species screened, except for the herbs would need to be established only once and are suitable for annual pollarding. They grow profusely without any agronomic management in dry wastelands, which will reduce production costs. Moreover, its ability to flourish on marginal arid and semiarid soil is an added advantage since its commercial development will not compete with other conventional agricultural crops or croplands.
Technical Abstract: The decline in the world supplies of hydrocarbons has lead to the search for alternate sources of fuel and chemicals. Plant species are potential sources of hydrocarbons. Large-scale screening of plants growing in the Western Ghats, Tamil Nadu, India was conducted to assess the hydrocarbon production and the type of isoprene compound(s) present. Three species contained more than 3% hydrocarbon. Sarcostemma brevistigma had the highest concentration of hydrocarbon with 3.6%. Seven species contained more than 2% of hydrocarbons among the plant species screened. The hydrocarbon fraction of Ficus elastica-Indian rubber tree- leaf tissue had a gross heat value of 9834 cal/g, which is close to the caloric value of Mexican fuel oil. Six hydrocarbon fractions contained gross heat values of more than 9000 cal/g. Of the 13 species hydrocarbon fraction analyzed, seven species contained cis-polyisoprene compounds, while two species contained trans-polyisoprenes. Cis and trans polyisoprenes are potential alternative energy sources for fuel and/or as industrial raw materials. All species screened, except the annual herbs would need to be established only once and are suitable for annual pollarding. Moreover, their ability to flourish on marginal arid and semi-arid soil is an added advantage since their commercial development would not compete with other conventional agricultural crops or croplands.