He explains that the early work into green gasoline production built off the advancements made in the catalytic refining of petroleum. The direct application of the petroleum industry’s tricks was not appropriate for bio-oil, however, so modifications were made to reaction conditions and different catalysts were used. “It’s complementary to the existing petroleum refining approach but it uses different catalysts and conditions,” Stevens explains.

“In the past three to five years, the pyrolysis community has made a lot of progress in the functional upgrading of biocrude to fuel products,” Stevens says. “We could do it in the past but we’ve gotten a lot better at it.”

This is not the only pathway to green gasoline. In a recent paper in the journal ChemSusChem, which features research at the interface of chemistry and sustainability with energy research, materials science, chemical engineering and biotechnology, Huber’s team of chemical engineers reported a breakthrough in the process. In the new work, the researchers show that pure sugar feedstocks can be converted into certain components of gasoline in a single step. By adding a zeolite catalyst, a solid catalyst, which consists of aluminum and silicon, to the pyrolysis process, cellulose can be directly converted to aromatics that make up a quarter of the chemical components found in gasoline. With further treatment, a liquid can be produced that is indistinguishable from gasoline.

“This is a new concept to make sustainable biofuel—a new route,” Huber says. The process, however, features a catalyst common to petroleum refining. “We started working with these catalysts because they are already used in the petroleum refinery and they are very inexpensive,” he explains. “They work well for petroleum refining and work reasonably well for biomass feedstocks.”

Now the team is designing catalysts specifically for biomass conversion. Although the team is currently producing green gasoline on a milligram scale, the research objective over the next few years is to scale up. “Our goal is to be able to have a process that can produce 50 gallons of aromatics from 1 metric ton of biomass,” Huber says. “We anticipate that this technology will have a significantly lower capital investment than cellulosic ethanol and syngas conversion technologies.”

Although it might be some time before Huber’s process is producing a significant amount of green gasoline, the approach PNNL, UOP and NREL have been working on is nearing that advancement. “We’re at the stage now where we’re [upgrading bio-oil] in several liter quantities,” Stevens explains. “It’s still at the bench top but we believe that in another year or two we’ll be at the position where if someone like the Department of Energy announced a demonstration-type solicitation, it would be time for us to do one of those.”

Picking one approach to reign now is shortsighted, however. “We’re excited and enthusiastic about Dr. Huber’s approach,” Stevens says. “All of these approaches are important. If we’re going to get to our [mandated] 36 billion gallons of fuel by 2022, I think you have to consider multiple approaches, multiple fuels, and part of those have to be infrastructure compatible because if we try to do it all with ethanol we have to have a huge infrastructure investment.”

What’s certain is that those invested in the domestic production of second-generation biofuels are ramping up their efforts. The road map edited by Huber sums up the current state of these efforts to produce fuels from nonfood biomass that are cost competitive with petroleum-based fuels: “At this stage, there are many more questions than answers but the tremendous potential for domestic production of essential fuels and products compels us to work diligently to develop the technologies necessary to realize this potential.”

Jessica Ebert is a Biomass Magazine freelance writer. Reach her at jebertserp@yahoo.com.

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