Attempting to chart a path forward for the beleaguered biofuels industry, a group of researchers at Lawrence Berkeley National Laboratory and the University of California, Berkeley, have devised what they describe as a novel method for producing renewable jet fuel. Using sugarcane and the sugarcane waste called bagasse, the new process (described in a paper in the latest issue of the Proceedings of the National Academy of Sciences) could enable green refineries to put out a range of products, including bio-based aviation fuel and automotive lubricant base oils.
The research appears at a time when biofuels have reached a crossroads. Shrinking government funding, investor disenchantment, low oil prices, and concerns over the loss of food cropland to grow corn and sugarcane for biomass have combined to bring the industry close to a standstill. Although production of renewable fuels in the United States doubled between 2007 and 2013, the use of biofuels as a percentage of overall transportation fuel has hardly budged. And while most major airlines have biofuel programs in some stage, aviation—which needs highly energy-dense, oxygen-free fuel—has proved an especially tough field to penetrate.
As a result, the future of the Renewable Fuel Standard, released in 2005 and expanded under the Energy Independence and Security Act (EISA) of 2007, has been called into question.
“The current first-generation biofuels mainly use food crops as feedstock and are either expensive or have modest [greenhouse gas] improvements over petroleum fuels,” concluded a report released in April by the Columbia Center on Global Energy Policy, written by James Stock, a professor of political economy at Harvard’s Kennedy School and a former member of the President’s Council of Economic Advisers. “The development and commercialization of low greenhouse gas second-generation biofuels—critical to the ultimate success of the program—has fallen far short of the very ambitious goals laid out in the EISA.”
To reach those goals and rejuvenate the biofuels industry, researchers are reëxamining the science of deriving fuel from biomass, seeking more efficient techniques that use nonfood crops, ones grown on marginal land, and waste by-products such as bagasse. A major barrier is pretreatment—breaking down cellular walls to release sugar, which can then be fermented and converted into fuel.
The Berkeley study, carried out under a public-private research partnership called the Energy Biosciences Institute (EBI), focuses on ketones, organic compounds derived from biomass that can be upgraded and treated to produce energy-dense compounds suitable for the production of jet fuels or base oils for automotive lubricants. Alexis Bell, one of the lead authors of the paper, describes it as the first process to create biofuels that can power existing jet engines without modifications. Designed for sugarcane production in Brazil, the process can be adapted to use crops grown on marginal land (thus reserving more productive land for food crops) and to use bagasse. With minor modification, it can also be adapted to produce renewable diesel, if future regulations provide support for the same, says Amit Gokhale, another of the lead authors.
“Sugarcane biorefineries today produce ethanol, sugar, and electricity,” Gokhale remarks. “Expanding the product slate to include aviation fuels, lubricant base oils, and biodiesel could allow operators to manage their market/price risks better.”
That’s a laudable goal, but implementing new techniques at commercial scale remains a significant challenge—as the Berkeley researchers acknowledge. Biofuel prices are likely to remain higher than those for fossil fuels for the foreseeable future, says Bell. Bringing those prices down will require moving further up the production chain and finding new, more powerful microbes that can streamline the process of converting biomass into fuel. Michelle O’Malley, who heads a biotechnology research group at the University of California, Santa Barbara, is working on combining microbes collected in the wild—in animal guts, mostly—into designed communities that can convert biomass directly into fuel, leapfrogging the pretreatment step to save time and costs.
“We’re trying to build synthetic partnerships to do things that not one of the individual microbes could do on their own,” says O’Malley. “The idea is to consolidate the entire process, from crude biomass to value-added products. That’s really what’s prohibited the economic production of biofuels to date.”
The result, she says, would be “a game-changing scenario.”
Changing the biofuels game is likely to take years, as first-generation ethanols give way to advanced biofuels produced by more efficient processes using more powerful microbial agents and catalysts. “It’s really about having the patience and persistence to stand up a new industry,” says Jonathan Male, who heads the U.S. Department of Energy’s Bioenergy Technologies Office. “When you start scaling up, the levels of complexity increase dramatically, as do the risks.”
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