Fuel from germs


For years, we’ve been turning crops such as corn, wheat and sugar beets into fuel, using yeast to convert sugar into alcohol.

But there’s an obvious problem with this. That stuff we’re turning into fuel is also food for humans and feed for animals.

(And as an aside, how come we always call it “animal feed” as opposed to “animal food”? And why don’t we ever refer to “human feed”? Hmm?)

A lot of the plant is wasted when you grow crops for fuel or food. The leaves and stems, with their tough cell walls made of cellulose, hemicellulose and lignin, are more of a nuisance than anything else. Wouldn’t it be great if there were a use for what is now plowed under or burned?

There is, or there soon will be, thanks to research aimed at using bacteria to convert this “lignocellulosic biomass” into fuel in its own right.

A just-published article in Nature reveals the state of the art. Titled “Microbial production of fatty-acid-derived fuels and chemicals from plant biomass,” it describes the successful engineering of the common bacterium Excherichia coli–better known as E. coli and generally in the news when it contaminates water or meat and makes people sick–into a producer of biodiesel.

One of the co-authors of the research study is Jay Keasling, chief executive officer for the U.S. Department of Energy’s Joint BioEnergy Institute (JBEI). “We’ve got a billion tons of biomass every year that goes unused,” he says, adding that fuel produced from that biomass could make up for as much as half of U.S. oil imports, turning “the U.S. Midwest into the new ‘Mideast’.”

That’s not hyperbole: by one estimate, lignicellulosic biomass could produce more than 7,500 litres of renewable petroleum per acre.

The researchers modified the E. coli genome, inserting genetic code for the production of an enzyme called hemicellulase, which can break down hemicellulose into smaller sugar molecules which E. coli can then turn into fatty acids.

E. coli normally produces only as much of the fatty acids as it needs for its own cell membranes. But the researchers’ E. coli were further modified so that the fatty acids just kept coming, turning each bacterium into a microscopic biodiesel factory.

The process takes place in fermentation vats, into which the bacteria expel little drops of oil. Turn off the impellers, and the oil floats to the top, where it can be skimmed off.

Even better, by tweaking the process, chemical products ranging from solvents to lubricants to jet fuel could conceivably be produced.

Of course, it’s important to note that the research reported in Nature is just a proof of concept. There’s no commercially viable process for doing any of this yet–but Keasling hopes there will be within a very few years. Work will continue as the researchers search for ways to make use of even more of what’s in the feedstock–not just the hemicellulose.

There’s already a company standing ready to market fuels and other microbe-produced chemicals. Based in California, LS9, founded by a geneticist and a plant biologist, helped fund the research reported in Nature. LS9 points out that the crude oil produced by bioengineered bacteria has none of the contaminating sulfur of regular crude oil, so it’s cleaner. And despite its unorthodox origins, it can be refined like any other crude oil in a standard refinery.

There are other companies pursuing their own paths. Amyris Biotechnologies, for example, says it has also created bacteria capable of providing renewable hydrocarbon-based fuels. There are many more.

Why would this be preferable to ethanol production as it is currently carried out? Aside from the aforementioned fact that we’re presently turning food into fuel, hydrocarbon fuels are more efficient than ethanol, packing about 30 percent more energy into any given quantity. And even better, they take less energy to produce: ethanol production, which involves distilling, requires 65 percent more energy than hydrocarbon production does.

Perhaps the oil industry will slowly evolve away from the purview of drilling companies and into the realm of agriculture.

As for the marketing slogan for this new germ-produced form of fuel, I think I’ve come up with a winner: “E. coli. It’s not just for food poisoning anymore.”

What do you think?

Permanent link to this article: https://edwardwillett.com/2010/01/fuel-from-germs/

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