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No. 2361:
Cellulosic Ethanol

by Andrew Boyd

Today, we make moonshine. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The source of moonshine, goes the old pun, is a mystery still. But it's not a mystery any longer. Stills are popping up everywhere. And they're producing good quality moonshine – close to 100 percent pure grain alcohol. Only now we call it ethanol. Our new fuel source really is that old backwoods concoction. But when it's made for cars it's denatured. That simply means adding things to make it undrinkable. 

North American ethanol producers use corn because it's economical. That's caused a lot of concern. It's also made us go back and think about plant materials we should start with. As we know from the variety of distilled spirits, there are many ways to make ethanol. 

The first step is fermentation. Yeast likes the natural sugars found in plants. These sugars are abundant in the grain or fruit of a plant – like that tasty corn kernel. The rest of the plant is thrown on the compost heap. That's a lot of waste.


But the story may change. Cellulose is hiding in all that wasted plant material. It's the most common organic compound on earth, and makes up about a third of all the material found in plants. Cellulose is used to make paper, cardboard, and cellophane. It's also an important ingredient in those healthy breakfast cereals, where it's known as dietary fiber. The human body can't digest it. It's too tough to break down.

That's a good thing for your body, but it's a problem for ethanol makers. Breaking cellulose down into natural sugars and converting it to ethanol is expensive. In fact, it's too expensive to compete with corn kernels. Researchers, businesses, and governments are working to make the process cheaper. The prize is so big, it's worth the investment.

One big investment came in December 2007. That's when congress passed the Energy Independence and Security Act. It sets aside fifty million dollars for "cellulosic ethanol and biofuels research." It also mandates how much cellulosic ethanol we must produce in the future — sixteen billion gallons by 2022. That's about 10 percent of the fuel used by road vehicles in the United States last year.

Ethanol isn't a panacea, whether it's made from corn kernels or cellulose. We need an energy plan that includes wind, water, and solar power – and conservation. Ethanol's just one cobblestone in a path to sustainable energy – a path loaded with many new and exciting technologies.

Still, it's amazing when you think of what cellulose-to-ethanol technology means. Almost any organic material could be used to create fuel for our cars – wild grasses, trees, corn stalks. And from what we can see right now, the process would be good for the environment. If cars used ethanol made from cellulose, they'd produce fewer greenhouse gases. 

And what's most amazing is that the technology isn't a dream for the distant future. We're working on it now. And we should see regular progress, year by year. Whod've ever thought that new and cheaper ways to make moonshine would one day be an international priority.

I'm Andy Boyd at the University of Houston, where we're interested in the way inventive minds work. 

(Theme music)

Cellulolytic Enzymes. Technology Review, March/April 2008, 52-54.

Cellulosic Ethanol. Accessed March 31, 2008, from Wikipedia. 

The Energy Independence and Security Act of 2007. Accessed March 31, 2008. 

Ethanol Fuel. Accessed March 31, 2008, from Wikipedia. 

The illustration of elementary distillation is from A. Johnston, A Manual of Chemistry, 6th ed. (Philadelphia, Charles Desilver, 1856). 

The corn stalk photograph was taken from Google public domain pictures.

The switch grass photograph was taken from Google public domain pictures.