UC Davis engineers, plant scientists and geneticists are heading a Chevron-sponsored project to develop the Jatropha curcas plant as a crop for biodiesel production in California. The three-year collaborative research program, now nearing its first year of completion, focuses on plant domestication, yield improvements and harvest optimization.
Oil extracted from jatropha seeds can be processed to fuel diesel engines while the plant’s remnants can be used to power electricity plants and create other practical byproducts including fertilizer.
Biodiesel reduces carbon dioxide emissions by nearly 80 percent compared with petroleum diesel, according to the U.S. Department of Energy.
The hardy jatropha plant, resistant to drought and pests, yields over four times more fuel per hectare than soybean and over 10 times more than corn. These major boons have boosted the plant’s status as one of the most promising renewable energy source substitutes for fossil fuels in India and other countries in Asia and the Americas.
“In my opinion, the major advantage of this crop is that it can grow on marginal land without displacing prime food growing land,” said Shrini Upadhyaya, a professor of biological and agricultural engineering at UC Davis who, along with department colleague Uriel Rosa, is developing techniques to mechanically harvest jatropha fruit.
There is an overall consensus that mechanical harvesting needs to be developed to establish jatropha as a sustainable biofuel crop, Rosa said.
Factors that affect seed yield, which can vary with the growing environment and with genetic diversity among plants, are also key issues being addressed by the collaborative studies.
Sham Goyal, a UC Davis plant scientist, is testing how effectively jatropha can grow on two-acre plots near Davis, Bakersfield and El Centro, three major crop growing areas that represent the varied climates in California’s northern, central and southern regions. According to Goyal, the plants are less than one year old but seem to be faring well in all the locales so far.
Jatropha typically starts to bear fruit roughly two years after planting and continues producing for about 40 years.
Besides the practicality of growing jatropha as an energy crop in California, concerns include seed toxicity and the plant’s potential to invade indigenous habitat.
“Jatropha is considered poisonous but not the kind where people or animals would potentially be dying left and right,” Goyal said.
If consumed, the kidney bean-sized seeds can cause some diarrhea and vomiting in adults as well as serious health problems in small children and infants.
It is not known to be an invasive species, meaning that it will not threaten native plants.
“I don’t believe that there is any evidence to show that it is invasive,” Goyal said. “In India, people have grown jatropha for about 500 years, and no one over there has told me that it is invasive. This is not to say that it could not be invasive in California though. We will simply have to watch closely.“
Goyal explained that jatropha should still be considered a “wild species” with room for much improvement.
“The plant needs to be domesticated,” he said. “Selection, breeding and other genetic manipulations must be done in order to enhance the plant’s potential for … higher yield and oil content, cold tolerance and de-toxification. To start with, we will be doing some [DNA] ‘finger-printing‘ to investigate the level of genetic variability.“
Genetic modification is also needed to improve the timing of fruit ripening so that fruits on the same branch mature simultaneously, which would make mechanical harvesting easier.
“We are thankful to Chevron for making it possible for us to do this research, which is cutting-edge and exciting,” Goyal said.
The $25 million five-year Chevron collaborative research investment, which began in 2006, is helping advance bioenergy research at UC Davis through the sponsorship of a number of projects.
“In my instance, [Chevron has] funded the purchase of farm and research equipment to help researchers around the state carry out applied work on biomass feed stock crops,” said Stephen Kaffka, executive director of the California Biomass Collaborative.
The statewide partnership of government, industry, environmental groups and educational institutions is administered for the state by UC Davis to enhance sustainable technologies for producing renewable energy and biofuel from plants and other biological material.
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