Sunday, November 19, 2006

Enzymes for Alcohol

Making alcohol for drinking or fuel is easy if you start from sugars. However, currently alcohol production for fuel consumes almost 20% of America's corn crop. Which is not nearly large enough to meet demand. The answer is enzymes which can break down cellulose into sugars.

The burgeoning U.S. ethanol industry will consume about 18 percent of this year's corn harvest.

By 2009, that figure will grow to 30 percent, officials said last week at the Kansas Agri Business Expo in Wichita.

"It is becoming clear that the growth in the industry cannot be sustained with grain production," said Scott Kohl, technical director for Colwich-based ICM, the nation's leading designer and builder of ethanol plants. "The industry will be driven toward cellulosic feedstock to continue to grow to meet the fuel demand."

Cellulosic, or biomass, feedstock includes residue from agricultural crops -- such as wheat straw and corn stalks -- grass clippings, wood chips and municipal trash. It offers an abundant, inexpensive feedstock and assures that grain production can continue to support biofuels and supply food for humans and animals.

But it is not without challenges.

Amy Ehlers, manager of Bio, a national trade association of the biosciences industry, said new processes are being developed that will make conversion of biomass to fuel more efficient.

"The current challenge is that the sugars contained in cellulosic materials are tightly bonded," she said. "Work is being done on enzymes that will help break those bonds and make the sugars available for fermentation into ethanol."
That means grass clippings, wood chips, and crop stalks (did I mention hemp?) can be converted into liquid fuel.
One of the advantages of cellulosic ethanol, she said, is that the raw materials needed are in good supply in all 50 states. That would allow the industry to become more spread out than grain ethanol production, which is concentrated in the Midwestern farm belt.

There are no commercial-scale cellulosic ethanol plants in operation, but three are planned, Ehlers said.

Iogen is running a pilot plant making cellulosic ethanol in Canada and plans to build a commercial plant sometime in the next two years, possibly in the United States, she said.

Abengoa, a Spanish company, is set to be first online with a commercial-scale plant in Spain, possibly as early as the end of this year. Abengoa owns a grain-fed plant in Colwich and plans to build another 110-million gallon plant there next year.

And Celunol has announced plans for a Louisiana plant that will make ethanol from sugarcane and hardwood residue sometime in 2007.

Richard Nelson, Kansas State University extension engineer, said one of the challenges to cellulosic ethanol is the need to leave some residue on the soil to hold moisture and prevent erosion.

"In reality, only about 30 percent of the residue from agricultural production will be available to use," he said.

Another reality, he said, is that no matter what form, biomass is cumbersome and not easy to transport.

"You have a huge amount of bulk to move," he said. "It takes about a ton of biomass to make 100 gallons of ethanol. And while the process will get more efficient, that's a lot of stuff to move."
The shorter the distance to be moved the greater the net energy gain. Which would tend to favor the enzyme process which can use feedstocks from anywhere.

If the methanol fuel cell ever gets to market it could be the foundation for an ethanol fuel cell which could make ethanol competitive on a dollars per mile basis with gasoline.

1 comment:

linearthinker said...

At last a sensible use for junk mail. What's the energy balance between delivering junk mail and fermenting it? Fertile ground for DOE researchers here. I sense a blizzard of tech bulletins is in the offing.