The concept of converting crop debris — leftovers following a crop’s harvest — into biofuel is not new to the realm of renewable energy; but the process of breaking down cellulose and hemicellulose, the complex sugars responsible for the rigidness of grass, leaves, and plant stems, into simple sugars for use as an alternative energy source, is substantially more difficult. Making great strides in that area is a team of scientists headed by MAES engineer Bruce Dale, a chemical engineer and the associate director of Michigan State University’s Office of Biobased Technologies.

“We can produce ethanol and other transportation fuels from cellulosic materials,” said Dale in a recent update from MSU news. Dale and other MSU scientists have devised a process known as ammonia fiber expansion, or AFEX, which, Dale believes, will manifest as affordable biofuel at a per-gallon cost. “There are some studies that show we can produce cellulosic ethanol for about $1 per gallon when the technology is fully mature. We’re not there yet, but I believe we should be able to get cellulosic biofuels to the pump for about $2 per gallon in the relatively near future.”

Biomass after AFEX process
Image via MSU News

The AFEX process, which MSU has patented, entails pre-treating cellulosic biomass with ammonia, which reduces 90 percent of cellulose and hemicellulose into simple sugars. For comparison, Dale points out that breaking down complex sugars exclusively using enzymes allows only 15 percent of the cellulose and hemicellulose to be converted. Two additional boons are an increase in cellulosic materials for other uses, such as feed for beef and dairy cows; and the physical downsizing of cellulosic materials into popcorn-sized nuggets, which makes the materials significantly easier to transport.

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