- Goal is to produce farnesane biodiesel from drought-tolerant guayule, sweet sorghum
WOOSTER, Ohio -- Ohio State University's Ohio Agricultural Research and Development Center (OARDC) will play a key role in the engineering of a novel plant-based fuel, funded by a $5.7 million grant from the U.S. Department of Energy.
The grant, awarded by DOE's Advanced Research Projects Agency-Energy (ARPA-E) under the Plants Engineered to Replace Oil (PETRO) program, includes a $1.2 subcontract to OARDC. Leading the project is Chromatin Inc., a Chicago-based developer of energy-crop feedstocks. Other partners include San Diego-based Allylix and Kansas State University.
The three-year project, titled "Plant-based Sesquiterpene Biofuels," involves the production of a hydrocarbon from two drought-tolerant plants: guayule, a woody shrub native to the southeastern U.S. and Mexico, and sweet sorghum, a crop similar to sugar cane that is grown in southern U.S. regions. This hydrocarbon can be easily extracted and cheaply converted into a renewable transportation fuel.
OARDC's role in the project involves the engineering of these two crops at the genetic level so they can boost the production of farnesene, a natural plant oil that can be converted into a diesel-like fuel. Farnesene is one of many sesquiterpenes, compounds that are associated with essential oils and resins in plants.
"We will use guayule as a model to study and perfect production of the farnesene molecule inside the plant," said Katrina Cornish, Ohio State's endowed chair in bioemergent materials and a guayule expert. "Guayule is a very good model because it already produces and stores a lot of hydrocarbons in the form of resin in its stems and branches."
A commercially grown source of hypoallergenic latex, guayule produces both rubber and hydrocarbon-rich resin. Cornish and colleague Josh Blakeslee, an OARDC biochemical physiologist, will genetically manipulate this plant so that it diverts more resin into farnesene. As this model is optimized, research partners at Chromatin will be simultaneously applying it to sweet sorghum to try to yield the same results.
"Sorghum makes very little of this hydrocarbon naturally," said Blakeslee, an assistant professor in the Department of Horticulture and Crop Science. "So the overall plan is to engineer the plant so that it diverts carbon from energy stores of sugar into farnesene. This is accomplished by activating the isoprenoid synthesis pathway, which is responsible for making more of this hydrocarbon in the plant."
The project's goal is to have guayule and sweet sorghum engineered to produce an estimated 20 percent of the plant's dry weight as farnesene, which is then extracted and hydrogenated to farnesane fuel.
Farnesane fuels have many advantages over existing biofuels, project partners said. Because the hydrocarbon is produced in the stalks and branches of target plants, these crops can generate much higher yields than conventional biodiesel crops such as soybean and canola, which use only their seeds to produce vegetable oil that is later turned into fuel.
Likewise, guayule and sweet sorghum could produce more than twice the comparable energy yield of ethanol from corn -- and do it in a way that bypasses the intensive process of starch milling, mixing with water and enzymes, fermentation, and distillation involved in making this biofuel.
"We are trying to have the plant make its own readily accessible liquid biofuel," Blakeslee said. "This will allow for a straight extraction process, basically squeezing the fuel out of the plant. Additionally, hydrocarbons burn better than alcohol fuels such as ethanol. This fuel will be more comparable to petroleum-based diesel in its performance."
Additionally, guayule and sweet sorghum can be farmed on up to 271 million acres (much of it marginal land) in two geographically distinct areas of the U.S., thus diversifying biofuel feedstock supply and land use with minimal impact on food crops. Both plants require little water or fertilizer, allowing for more economical and sustainable production systems.
Estimates indicate farnesane fuel could cost less than $50 per barrel of petroleum equivalent. Utilizing the full 271 million acres could theoretically produce 30 percent of U.S. annual energy needs, according to project partners.
OARDC is the research arm of Ohio State's College of Food, Agricultural, and Environmental Sciences.