The promise and peril of energy from cellulose

There’s been progress, but we’re still far, far away from the day when cornstalks and switchgrass will yield enough fuel at a reasonable cost to make a difference in the energy economy.

As you may or may not know, in the last five or so years there’s been a major shift in thinking and policy on alternative fuels, particularly ethanol. Today, nearly all U.S. produced ethanol – gasoline made from plant material – is made from corn. Last year, U.S. ethanol producers made around 9 billion gallons. The problem, as has been well documented by the media, is that corn is also food. It may or may not be the case that corn-based ethanol raises the price of corn-based feed for cows and chickens and the price of any food that’s in any way dependent on corn (which is a lot of food). But, in some general sense, the food vs. fuel debate has been largely decided in favor of food.

Which is why, in the past few years, there’s been a major shift toward “cellulosic” ethanol – that is, biofuel made from non-edible plants. The federal government has earmarked billions of dollars for cellulosic ethanol research and development, meaning that scientists and entrepreneurs around the country are racing to figure out how to make fuel from switchgrass, corn stover and other plants we don’t eat.

There’s just one problem: it’s extremely difficult to extract cellulose from green plants, isolate its sugars, and ferment them into alcohol that can then be refined into biofuel. Think of it this way: for millions of years, plants have evolved to ward off insects, disease and other threats that want to break them down and siphon off their juice. That’s why cellulose is such a tough substance, composed of linked carbohydrates woven into a kevlar-like web meant to bolster and protect plant cells. Scientists are literally battling against nature and millions of years of plant evolution to figure out how to break down cellulose into its constituent parts.

There’s been progress, but we’re still far, far away from the day when cornstalks and switchgrass will yield enough fuel at a reasonable cost to make a difference in the energy economy. And that’s not for a lack of effort. Scientists I spoke with at the University of Illinois and the University of Kentucky – Mark Crocker and Hans Blascheck, respectively – described dozens of projects involving new cellulosic biorefineries, more efficient ways to convert cellulose to fuel, ways to transport biomass from forests and other sites to refineries.

This work is happening all over the country. But the truth is that we’re only at the beginning of what will probably be a long, uncertain journey toward renewable fuels. I think we’ll get there, but it will take a while.

EarthSky