Scientists keep banging away at it – converting wood or woody fibers to ethanol (cellulosic ethanol) or other useful fuel. It’s difficult, plant materials that contain sugars are easy (for example, fermentation for alcohol) but woody fibers (cellulose) don’t have much of that kind of organic material. By nature, wood is tough stuff and doesn’t break down easily into volatile carbon compounds that make up fuels. Nevertheless, because there is a lot of woody fiber in the world, and because using it wouldn’t compete with plant material needed for food, it’s a worthy challenge. One school in the U.S.A., the University of Wisconsin (Madison) has been working with the conversion of plant material to ethanol and other fuels for many years. Recently researchers there announced an important improvement in the conversion of woody material.
The general problem with using woody biomass (cellulose plant material) hasn’t been the chemistry, but the cost of the chemistry. There are well-known enzymes that can break down fibrous material into simpler compounds – but they are expensive, about 10 times more expensive than enzymes used for starchy (food) plant material. When used in bulk, as it would have to be for successful fuel replacement, the processing costs are uncompetitive.
The approach taken by the research team, led by Rajai Atalla, founder of Cellulose Sciences International, is to pre-process the woody biomass with both physical (such as shredding or maceration) and chemical (using an inexpensive mix) techniques so that much less of the expensive enzymes can be used to break it down into sugars (mostly glucose). From there it’s a relatively standard process to convert the sugars into ethanol.
Atalla’s involvement with research on cellulose dates to the 1960s, but it was a recent experience that inspired much of his focus on ethanol from cellulose rather than corn. In 2007, he read about people in Mexico struggling with the high cost of corn due to increased demand for corn to make ethanol.
“It got me thinking,” Atalla recalled. “I thought, ‘This is ridiculous.’ If we can produce what we need from cellulose, rather than starch, we won’t need to compete with food products. But we faced huge obstacles. The enzymes needed to use cellulose cost about 10 times more than those used for converting corn. With the treatment we’ve developed, though, we may be able to cut the enzyme cost to about the same range as it is for corn, which would make cellulose a much more viable biomass substrate for the production of biofuel.”
Current testing shows that approximately 80% more cellulose is converted by the new method than by previous techniques. The process is still undergoing refinement and will need to be scalable (make big quantities) before passing the manufacturing requirements. There are cellulose conversion projects occurring all over the world. Sweden, for example, has committed to a completely oil-free economy by 2020; its emphasis is cellulosic ethanol as a replacement.