Fueling America Without Petroleum

By Laura McGinnis | November 13, 2007
The demand for alternatives to petroleum-based fuels is steadily rising. Corn and soybeans—the dominant feedstocks for ethanol and biodiesel production in the United States—grow well in the central regions of the country. However, are these the only available sources? What options exist for U.S. growers in other regions? How can corn and soybean feedstocks be improved?

Scientists at the Eastern Regional Research Center (ERRC) in Wyndmoor, Pa., are answering these and other questions about renewable fuels production. Their research focuses on four major areas: ethanol, biodiesel, thermochemical processes and cost analysis. "For years, ERRC has been a committed participant in alternative fuels research," says center director John Cherry. "This is a particularly exciting time because so much of our research work is being adopted and used by industry."

Beyond the Corn Belt
Affordable, available and easy to work with, corn is the main feedstock for ethanol in the United States. As ethanol production increases—USDA chief economist Keith Collins estimates the United States could produce 12 billion to 13 billion gallons in 2009—so does the demand for suitable feedstocks. To avoid overburdening the corn market, ethanol producers have two options: increase conversion efficiency or use an alternative crop. Several ERRC research projects have demonstrated how it can be done.

Food technologist David Johnston is investigating new processes using protease enzymes from microbial and fungal sources to more efficiently produce ethanol. In trials, Johnston found that adding enzymes during fermentation sped up the process and increased ethanol yields. "The enzymes make more nutrients available for the yeast," Johnston says. "They expedite the fermentation process and can also make it easier to separate liquid from solids after the ethanol has been removed. This is important because the more efficiently you separate the free liquid from the solids, the more energy efficient the process can be."

Corn isn't the only available feedstock for ethanol. Research leader Kevin Hicks is collaborating with biotechnology company Genencor International, Virginia Tech in Blacksburg, Va., and members of the barley industry to explore barley's potential as a feedstock in regions of the United States where corn is not the principal crop.

Hicks estimates that barley grown in North America could supply approximately 1 billion gallons of ethanol per year. The crop is well suited to the Mid-Atlantic, where it could be grown as a winter crop in rotation with soybeans and corn in two-year cycles.

Currently, barley yields less ethanol than corn, and the ethanol from barley is more expensive to produce. Barley's physical properties—an abrasive hull and low starch content—impede production efficiency, but Hicks and his colleagues are overcoming these hurdles with research.

With Genencor, the researchers are developing new enzyme technology that could improve the speed, efficiency and cost of barley-based ethanol production.

They also collaborated with Virginia Tech researchers to develop barley varieties with higher starch content and a loose hull that generally falls off during harvest or grain cleaning. Initial studies suggest that such varieties have promise as a feedstock. In one study, a hull-less barley produced 2.27 gallons of ethanol per bushel, whereas hulled barley produced 1.64 gallons per bushel. The scientists are now studying which conditions will promote the most cost-effective production of barley-based ethanol.

Breaking Down the Biomass
There are two main processes, or "platforms," for making fuels from biomass: sugar and thermochemical conversion. The sugar platform involves breaking down complex carbohydrates in the biomass—materials such as sawmill waste, straw and cornstalks (stover). Then, yeasts metabolize, or consume, the simple sugars to make alcohol.

Breaking down those complex carbohydrates requires a lot of energy, Hicks says, and special microorganisms are required to convert some sugars into ethanol. Ironically, the process creates a lot of carbon dioxide—the greenhouse gas that's helping to spur the biofuels movement.

The thermochemical platform involves heating the biomass in a reactor and converting it into liquid (bio-oil) and synthetic gas (gaseous fuels comprising carbon monoxide, hydrogen and low-molecular-weight hydrocarbon gases such as methane and ethane).

Chemical engineer Akwasi Boateng has led much of the ERRC research on this process. In a study with research leader Gary Banowetz and colleagues in Corvallis, Ore., Boateng converted grass seed straw into synthetic gas using small-scale gasification reactors. Built to serve a farm or small community, these reactors could provide an environmentally friendly and economic use for the 7 million tons of straw produced by the grass seed industry every year in the Pacific Northwest.

Neither the sugar platform nor the thermochemical platform has been perfected yet, Hicks cautions. "Each one has technical and economic hurdles that must be solved through research," he says. "We're trying to compare the processes and determine which, if perfected, would give the most useful energy from a given amount of biomass. We're working with international experts to make intelligent decisions on where to focus our efforts."

A Model Approach: Cost Analysis
Price is one of the major factors inhibiting the spread of biofuels. Reducing production costs would make them more competitive with petroleum-based fuels—but where can scientists cut costs?

Engineers Winnie Yee and Andy McAloon create technical models to guide research efforts toward economically feasible processes. With the models, they analyze every aspect of a biofuel production process and determine where cost-cutting would be most effective. This allows researchers to pinpoint the exact steps in the process that need to be modified. "It's important to know that our research makes economic sense, that these processes will be competitive enough for industry to accept them," McAloon says.

Biochemist Mike Haas used one of McAloon's models to analyze his efforts to create biodiesel from soy flakes. The model estimated that by first drying out the moist flakes, Haas could reduce the amount of methanol required later, thereby reducing the cost per gallon from $2.83 to $2.66. Haas and his colleagues are currently working to reduce that cost even further to a point of commercial competitiveness.

For about 10 years, ERRC has been providing these technical models for ARS scientists. Developing a model from the ground up is time-consuming, McAloon says, but once developed it can be modified to meet the needs of a specific product or process. He estimates that within the past year ERRC has produced several hundred copies of their models for researchers within ARS and around the world.

"Our scientists are approaching biofuels research from many different angles that allow us to come up with comprehensive solutions," Cherry says. "We've made some great discoveries here at ERRC that have helped improve biofuel production, and I'm confident that we'll see even more improvements in the future."

Laura McGinnis is a member of the USDA ARS information staff. Reach her at laura.mcginnis@ars.usda.gov or (301) 504-1654. This article was adapted from the April 2007 issue of Agricultural Research magazine.

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