Outgrowing Corn Cellulosic ethanol made from ag and forest refuse

By E.M. Morrison

The next generation of Minnesota ethanol plants might be built from sticks and leaves.

Agricultural biomass could fuel a huge expansion of America’s ethanol industry. Cellulosic ethanol promises large supplies of renewable motor fuel, greater energy independence, less pollution and a stronger farm economy.

However, the effort to turn crop and forest residues into liquid fuel is in its infancy, says AURI biofuels expert Ed Wene. Cellulose conversion technology is still in the basic research stage. An efficient biomass handling and delivery system does not yet exist.

Yet, interest in cellulosic ethanol is running high, Wene says, and work on “alternative ethanol” is being backed by government and industry. “If we’re serious as a nation about reducing our dependence on foreign oil,” Wene says, “cellulosic ethanol is probably our best prospect.”

More demand than corn

High oil prices, surging global energy demand, and national security are driving the effort to find domestic substitutes for petroleum, Wene says. Because gasoline makes up half of U.S. oil consumption, development efforts have focused on transportation fuels, especially ethanol.

The United States will produce 8 billion gallons of ethanol within the next few years — nearly all of it from corn. In the coming decades, the need for alternative fuels is expected to climb by tens of billions of gallons. Federal renewable energy targets call for the nation to produce up to 60 billion gallons of ethanol a year by 2030.

There is nowhere near enough corn to meet this goal, Wene says. “We can only grow so much corn or starch-based grain or sugar.”  In fact, the entire U.S. corn crop could only produce enough ethanol to displace about 12 percent of current U.S. gasoline use. And growing corn taps other resources — not only fertilizer, pesticides and fuel — but all the water it takes to process corn for fuel, using existing technology, says Wayne Hansen AURI project specialist. More important, “We may need most of our corn for food and feed, especially in years we have a crop shortage,” he says.

All of this is sparking interest in making ethanol from biomass, which is much more plentiful than corn and available nearly everywhere. The federal energy agency estimates that the U.S. could produce 1.3
billion dry tons of biomass a year — enough to provide about 30 percent of U.S. petroleum needs. Biomass sources include corn stover, wheat straw, urban and forest wood waste, sugar cane and paper pulps, rice hulls, municipal garbage, and nonfood energy crops such as switchgrass, hybrid poplar and willow.

Biomass benefits
Like other biofuels, cellulosic ethanol could reduce America’s dependence on fossil fuels and curb emissions of carbon dioxide, a greenhouse gas, says Todd Reubold, assistant director of the University of Minnesota’s Initiative for Renewable Energy and the Environment.

Cellulosic ethanol would have other environmental benefits, too, Reubold says. Biofuel crops could be grown on land that’s unfit for food crops, using few inputs. He points to research at the U of M’s Cedar Creek field station, which found that mixed perennial native grasses produced high biomass yields without fertilizer or replanting.

Advocates say cellulosic ethanol would also create jobs and rev up the farm economy, just as corn ethanol and biodiesel plants are doing now. “In our discussions with farmers,” Reubold says, “many have been quite interested in cellulosic ethanol because they see it as another opportunity for rural areas.” In addition, Wene adds, “we could see ethanol production expand to areas of the country
where you can’t grow corn.”

Backed by Uncle Sam
Washington is pushing hard to make it happen. The 2005 Energy Policy Act mandates the use of 250 million gallons of cellulosic ethanol by 2013. The Act provides loan guarantees of up to $250 million per plant for biomass ethanol facilities, plus additional incentives such as tradable energy credits. It
also makes $1.2 billion available for cellulosic ethanol and biofuels research.

Last February, President George Bush announced the Advanced Energy Initiative, calling for greater reliance on domestic energy sources. The Initiative sets a national goal of making cellulosic ethanol competitive within six years. In October, the U.S. Department of Energy announced that it will provide
$250 million over the next five years to set up cellulosic ethanol research centers. AURI is helping to organize a bid for a Minnesota cellulose research center.

Private sector companies are also putting up money for cellulosic ethanol research — among them DuPont, Abengoa and Archer Daniels Midland, says U of M agricultural economist Doug Tiffany, a renewable energy expert. “Many companies want to be in on this. They think it’s going to grow and they don’t want to be left out.”

For example, Royal Dutch/Shell and Goldman Sachs are backing research by Iogen, a Canadian enzyme maker. In 2004, Iogen began operating a demonstration plant in Ottawa that uses patented enzymes and
special yeast to break down wheat straw for fuel alcohol. Recently Iogan announced plans to build a pilot plant in Idaho that will make ethanol from wheat and barley straw.

Unlocking cellulose’s promise

Yet the technical challenges of making ethanol from biomass are daunting, Wene says.

Today, ethanol is made from cornstarch, which is easily converted to sugar, then fermented with yeast to brew alcohol. Cellulose, an element of all plant cells, also contains usable sugars. But these sugars are
locked up in complex chains of molecules, making them difficult to separate and ferment.

Since the 1950s, scientists have been looking for enzymes and microorganisms that can efficiently tap the sugars stored in cellulose and quickly convert them to fuel. In the last few years, the federal government and private companies have invested more in this research. “But the technology is not yet
perfected,” Hansen says, “and the cost of producing it is too high.”

Cellulosic ethanol processing is almost twice as expensive as corn ethanol processing, assuming historical corn prices, according estimates by the National Renewable Energy Laboratory. And the cost of building a biomass ethanol plant is roughly triple that of a comparable corn dry mill, Tiffany says.

Challenges for farmers, too
Biomass handling is another challenge. Although farmers already own the equipment needed to harvest and haul crop residues, these materials are expensive to collect, transport and store. Dan Petrolia, an
agricultural economist formerly at the University of Minnesota, now at Mississippi State University, has studied corn stover collection costs. In most cases, he says, “You aren’t going to be able to harvest and deliver it for less than $50 per dry ton.”
 

Even at $50 a ton, Don Vogt doubts that there would be many farmers interested in harvesting their biomass. The Steele County, Minn. grower raises native grass seeds for the conservation market. He also cuts and bales switchgrass and big bluestem straw for mulch. He says it’s not profitable to
harvest the residue for less than $20 per 500-pound bale. This fall, he didn’t even bother because diesel prices were too high and mulch prices were too low, he says.

There are also timing and supply issues with crop residues, Petrolia says. The harvest window is only a few weeks. And it’s not yet known how much residue can be removed without affecting soil fertility and erosion control, he says. “For years and years, we’ve been telling farmers to leave this stuff on
the fields, and finally, they are doing it. Now, we’re going to tell them to take it off?”

There’s a thorny “Catch-22” with biomass, too, Petrolia adds. The high cost of transporting bulky plant material favors small, decentralized processing plants that use biomass produced close by. But small
plants lack economies of scale, which makes it harder for them to compete.

The economics of energy crop production are also untested, Wene says. Switchgrass plots, for example, suggest that “yields could reach 10 to 12 tons per acre,” Wene says. “This would be under ideal conditions and would not represent true capabilities for most fields, certainly not marginal CRP land.”

Outlook                                                                                                     
Many experts take a cautious view of cellulosic ethanol’s prospects, at least in the near term. Petrolia notes some critics complain that “this technology has been five years away for the past 20 years.”

“We’re closer now,” adds Wene, who first worked on cellulosic ethanol in the mid-1970s, “but it’s still a few years away.”

What’s needed now are demonstration plants to prove that this method can succeed on a commercial scale, Wene says. “That’s the next step, and several companies have plans to build these.” In October, for example, Dupont and Broin Companies announced intentions to produce ethanol from corn stover. Massachusetts-based Celunol is proposing to build a 1.4-million-gallon pilot plant at Jennings, Louisiana to convert sugar cane pulp to ethanol. Government research teams are also working on scale-up projects.
 

How soon could we see cellulosic ethanol for sale in the marketplace?

Tiffany says be patient, as the corn ethanol industry took 30 years to develop. “In the 1980s many ethanol plants failed because they faced times of cheap crude oil and we were unable to lower their production costs to remain competitive.”
 

“It will take some time for cellulosic ethanol to become competitive.”  ■