New Approach to Cellulosic Bio-fuels Should Make Biofuels from Biomass Easier

The main obstacle to wide-scale use of biomass to biofuels fermentation is the difficult and expensive task of breaking down cellulose to fermentable sugars. Michigan State University researchers have invented a new approach which promises to make the entire process significantly more economic and affordable.

A patented Michigan State University process to pretreat corn-crop waste before conversion into ethanol means extra nutrients don't have to be added, cutting the cost of making biofuels from cellulose.

The AFEX (ammonia fiber expansion) pretreatment process, developed by Bruce Dale, University Distinguished Professor of chemical engineering and materials science, uses ammonia to make the breakdown of cellulose and hemicellulose in plants 75 percent more efficient than when conventional enzymes alone are used. Cellulose in plants must be broken down into fermentable sugars before they can be turned into biofuel.

"Doctoral student Ming Lau and I have shown that it's possible to use AFEX to pretreat corn stover (cobs, stalks and leaves) and then hydrolyze and ferment it to commercially relevant levels of ethanol without adding nutrients to the stover," Dale said. "It's always been assumed that agricultural residues such as corn stover didn't have enough nutrients to support fermentation. We have shown this isn't so." _NewsMSU

If this new process can reduce the expense of the conversion of cellulose to fermentable sugars by 75% or more, the entire economic equation has just been shifted to favour biomass to biofuels fermentation.

The current best way of creating fuels from cellulosic biomass is via gasification or pyrolysis, plus thermochemical conversion. An inexpensive chemical conversion plus fermentation would save considerable energy involved in either gasification or pyrolysis. The final step of separation of fermented biofuels from the "mash" would likely require distillation, although various methods of membrane separation have been developed to increase fuel concentrations and reduce the energy required in separation.

There is much cellulosic biomass that goes to waste every year in forests, agricultural fields, and municipal landfills. And as we have seen here at AFE, the planet Earth itself is capable of growing many multiples of its current biomass crop if given the opportunity.