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?

Fermenting the sugars found in corn or other grains into ethanol has been around for a long time, of course, and it’s pretty much a proven technology. On the other hand, do we really want to be turning food into fuel?

More promising have been recent advances in turning lignocellulose, the stuff that makes up the cell walls in plants, into ethanol and other fuels: that would allow us to use grasses, wood chips, straw and other non-food as biomass.

Now comes word of a fuel-producing technology that doesn’t require biomass of any sort: just carbon dioxide and sunlight. And no, I’m not talking about trees.

On Monday, a Massachussetts company called Joule Biotechnologies announced that it has the technology to convert carbon dioxide directly into transportation fuels and chemicals. Not only that, they say, “this eco-friendly, direct-to-fuel conversion requires no agricultural land or fresh water.”

The company was founded in 2007, and relies on something it calls “Helioculture” technology, mixing, as the New York Times’s article on the announcement puts it, “CO2, Slime and Sunshine.”

More specifically, the company grows genetically engineered microorganisms in specially designed bioreactors. The microorganisms are photosynthetic, able to use energy from the sun to convert carbon dioxide and water into ethanol or hydrocarbon fuels.

The process works well in the laboratory, so the real question is if it can be scaled up to an industrial-sized plant. To find out, Joule plans to break ground on a modular pilot plant early in 2010 that will produce ethanol (trademarked as SolarEthanol), and the following year hopes to begin construction on a commercial-scale operation that can also produce hydrocarbons and associated chemicals, “several of which have already been demonstrated at laboratory scale.

It’s looking for sites near CO2 producers such as coal-fired power plants and cement kilns, with locations in Texas, Arizona, Nevada and New Mexico, places with lots of sun and lots of space, under consideration

Open spaces are needed because a large plant would look a lot like a solar array: a huge field covered with panels, except these panels, rather than producing electricity, would produce liquid fuels

The company estimates that a single acre covered with its “SolarConverter” panels (flat, transparent, and about the size of a sheet of plywood) could produce 20,000 gallons of ethanol at a cost of $50 a barrel. (That makes it competitive with oil, although it’s worth noting that that price includes existing subsidies: what the unsubsidized cost would be, I don’t know.)

At that level of production, if you built enough plants to cover, in total, an area the size of the Texas panhandle, you could meet all of the United States’ transportation fuel needs.

In Technology Review, writer Kevin Bullis notes that the company’s technology sounds similar to that of biofuels produced by algae—but the company says it is not using algae, and its stated production estimates are an order of magnitude greater than algae-based biofuels, which are estimated to have potential yields of only 2,000 to 6,000 gallons per acre.

Its estimated cost of production is also only a fraction of that of algae-based biofuels, which currently would require crude oil to rise to $800 a barrel in order to be competitive.

Besides, algae produces oils that have to be refined, whereas Joule says its microorganisms will produce ethanol or hydrocarbons directly. The Joule microorganisms also excrete the fuels, whereas algae has to be harvested and processed to extract oil.

Too good to be true? Maybe. But there are other companies in the race to develop the same kinds of technology. And with the push to reduce carbon dioxide emissions and move away from fossil fuels, that race is only going to get hotter.

So remember the name: Joule Biotechnologies.

Someday, its genetically modified critters could be cheerfully churning out the fuel that powers your car.