Senior Technician Bill Bray (front) and Master Technician Bob Lyons (back) and inspect and service the biomass pretreatment reactor in NREL's Integrated Biorefinery Research Facility. (Dennis Schroeder)
With the DOE, Virent, Inc., and the National Renewable Energy Laboratory (NREL) working together, planes may soon take to the skies using less petroleum. In June, DOE announced an award of up to $13.4 million dollars to Virent and its partners to develop a process to cost effectively convert cellulosic biomass - in this case the non-edible parts of corn - into jet fuel.

"This is all about making drop-in fuels or infrastructure-compatible fuels," NREL Manager for Bioprocess R&D Richard Elander said. "These are fuels that are close, if not identical, to the same molecules that are in gasoline, diesel fuel, and jet fuel. They are compatible with our existing vehicles and infrastructure in terms of engines, fueling and pipelines."

The end result of the combined NREL-to-Virent lignocellulosic conversion process is not ethanol. While ethanol is a reasonable substitute for gasoline, is not a substitute for jet fuel due to ethanol's lower energy density and other properties required for jet fuel.

"Rather than fermenting corn stover into ethanol, in this scenario, the biomass is appropriately deconstructed and then catalytically converted into energy dense hydrocarbon molecules that are indistinguishable from petroleum based jet fuel," Virent Senior Director for Feedstock Development Andrew Held said.

Idaho National Laboratory will provide the corn stover for the experiments. NREL will then use acid or other chemicals to pre-treat and deconstruct the biomass, creating a new compound, or hydrolysate, containing sugars and other forms of soluble carbon.

"One of the interesting features of the Virent technology is, not only can they uses simple sugars, they can also use slightly longer chain sugars, plus they can also use some of the 'undesirable' products from when we over-treat the biomass," Elandar said.

Over-treating happens in the lingocellulosic conversion process because the biomass has to be broken down enough to get to the hard-to-reach sugars. The process is not perfect, so some of those sugars can be over-treated and become sugar degradation products. According to Elander, "This particular process has the opportunity to use a wider range of sugars and other soluble carbon compounds that are generated in the deconstruction process than we've traditionally been able to, which is a good thing because it means potentially higher yields."

Virent will take the hydrolysates produced in NREL's Integrated Biorefinery Research Facility (IBRF) and use a proprietary catalytic conversion technology to make the final jet fuel. "We remove the oxygen to make the deconstructed biomass more amenable to further processing, ultimately turning the hydrolysates into the same hydrocarbons that make up ordinary jet fuel," Held said.

While NREL has an important role in the agreement in deconstructing the quantities of biomass needed for the project, the lab has two other equally important tasks. First, NREL will perform techno-economic analysis of the project to make sure it is financially feasible in the long run, and second, NREL will study the fundamentals properties of catalysts used in the process.