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The race is on to make commercial amounts of ethanol or other biofuels out of plant waste containing cellulose -- a fibrous component of plants that gives them structure. But some researchers are looking at a different option -- using cellulose to power microbial fuel cells, in which bacteria digest plant waste matter to create electricity directly.

These fuel cells could be used to charge batteries or power electrical devices.

Others are considering drawing power from microbes digesting human waste at wastewater treatment plants or manure from feedlot lagoons.

"Basically, we're converting cellulose into a different energy source than ethanol," said John Regan of Pennsylvania State University in University Park.

"It's not more efficient right now, but if you look at what's been done over the last decade, there has been about a five to six order-of-magnitude (100,000-1,000,000-fold) increase in power density."

What are Second Generation Biofuels?
Ethanol made from cellulose, as opposed to ethanol made from corn, is a second generation biofuel. The difference, and it's an important one, is that second generation biofuels use non-food residual biomass like the stems, leaves, wood chips, and husks, or they use non-food crops that can be grown without high energy inputs, like switchgrass.

Verenium's Cellulosic Ethanol Goals
Verenium wants to create cellulosic ethanol at $2 per gallon, which right now would make it fairly competitive with corn ethanol and regular gasoline.

But this demonstration plant is just the beginning: Next year, Verenium wants to built several commercial plants that would each produce 20 to 30 million gallons of cellulosic ethanol yearly. That's still a fairly small drop in the bucket of gasoline consumption, but it would be much better than corn ethanol, and certainly better than fossil fuels.

What to do with Corn Ethanol?
One question that remains is: What do we do with all that corn ethanol?

The best hope would be to convert corn ethanol biorefineries into second generation biofuel plants. That might or might not be possible on a technical level, but we suspect that on a political level it will be even harder. The farm lobby is very good at keeping subsidies forever. When food prices are low, they ask for subsidies, when prices are high (as now), they ask for more. So who knows if the fat corn ethanol subsidies will ever be repelled?

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