Most of the biofuels on the market now fall into one of two categories: bio-alcohols, such as the ethanol made primarily from corn in the U.S., and biodiesels, which are made from fatty acids. Both are no more than additives in gas or diesel, unless an engine is specially designed to run on them.
The next wave of alternative fuel hopefuls could be synthetic analogues—fuels created by genetically engineered bacteria, designed to be completely compatible with engines that run on fossil fuel. Today in the Proceedings of the National Academy of Sciences, researchers at the University of Exeter led by John Love announced that they've produced one such biofuel with plans to push toward commercial application.
"Modern engines have coevolved with fossil fuels, and for an engine to function optimally, it needs high-quality fuel—fossil fuels offer that very high quality," Love tells PopMech. He says those biofuel additives hurt the fuel quality when added to gas, and so his research team set about to create a new synthetic fuel that could be just as good as petroleum-derived products and work with today's engines. "The challenge we faced," he says, "was finding a way to make the fuel that the retail industry needs biologically, rather than mining it from the ground."
First the team looked for an organism that might produce the same molecules that give a fossil fuel its energy—specifically, alkanes or saturated hydrocarbons. Lots of animals produce alkanes that are similar to what's in petroleum, usually for waterproofing. But after nine years of what Love calls bioprospecting, the researchers had come up short.
"Instead, we went the way of synthetic biology," Love says. "If nature hasn't designed such an organism, we can still design our process using parts designed by nature."
Ultimately, Love's team hijacked the process of fat production in strains of E. coli. This microorganism gets a bad rap because some strains can cause food poisoning and sickness in humans, but more versions are harmless and part of the natural bacterial system that lives in our guts. Because E. coli is so common in humans, scientists know a lot about it, and because scientists know a lot about it, the bacteria is a good candidate for this type of genetic tinkering.
By manipulating the natural metabolic system of the bacteria, tweaking up to 10 genes throughout the process, Love and colleagues converted bacterial food (usually sugar) into fat, which could then be engineered into alkane biofuel. "We were trying to specifically generate the molecules that the fuel industry needs," Love says, "and we have—albeit in a very small amount. At this point, it's just a proof of principle demonstration."
For now Love's team intends to compare the molecules they produced with their natural counterparts. They then hope to make the production process more efficient at the cellular level and boost the energy content of the resulting fuel. "Luckily enough," Love says, "we've got some money to do that with."
The researchers then must confront the issue that hounds every synthetic fuel researcher—scaling up. Numerous studies have outlined new ways to make new fuels in the lab, but it's an awfully tall order to imagine scaling up such a complicated chemical process to the level of our nationwide energy economy. Love says the next step after the basic research is a life-cycle analysis to see how efficient the production process is. Then a small demonstration plant—one producing hundreds, or perhaps thousands, of liters for several years—would precede a small, and then a full-scale, industrial plant.