Biofuel success hinges on diverse feedstock
U. ILLINOIS (US)—A highly productive perennial grass that grows throughout Canada and the midwestern United States may offer the best bet to produce ethanol sustainably without taking up more of the land currently used for food and feed production.
Researchers believe Miscanthus, along with sugarcane, could produce enough ethanol to replace the US’s use of petroleum and reduce dependence on fossil fuels.
“As new technologies increase the efficiency and cost of ethanol production, possibilities are opening up to use a wider range of plants to create a larger renewable fuel supply,” says Stephen Long, professor of crop sciences at the University of Illinois.
“Instead of repurposing food and feed crops, we are looking for dedicated energy crops with high production and low inputs to develop a system that’s environmentally and economically sustainable.”
Details of the research appear in the Aug. 13 issue of Science.
“We have to avoid further competition with land currently producing food and feed while increasing the economic and environmental viability of our country,” Long says.
“Lignocellulosic biofuel production will create employment opportunities in areas where land has dropped out of productive use.”
In 2008, the world produced 87 gigaliters of liquid biofuels, equivalent to the amount of liquid fuel used that year by Germany, a country of 100 million people. Brazil and the United States produced 90 percent of the fuel supply from sugarcane and corn.
The current study shows it’s possible for Brazil to increase production of sugarcane ethanol considerably, up to 14 percent of expected global use by 2030.
“These results can be achieved in Brazil without impacting food production,” Long says. “In addition, it would create strong benefits in terms of greenhouse gas emissions, and generate 22 megawatt hours of renewable electrical energy from residues that cannot be converted to ethanol.”
While sugarcane has the greatest potential to produce biomass in the near future, the opportunity to develop sugarcane ethanol in the US is limited to Hawaii, Florida, Mississippi, Louisiana, Alabama, and Texas.
Miscanthus, on the other hand, can grow on marginal or non-crop land. It’s a close relative to sugarcane, but tolerates cold temperatures sufficiently enough to be grown throughout the Midwest and into Canada.
One of the best characteristics of Miscanthus is its ability to produce high biomass yields. Researchers report 17 tons per acre can be achieved in many locations in the Midwest and East.
“Miscanthus produces 60 percent more dry biomass than our best corn crops, but unlike corn it does it without any nitrogen fertilizer,” Long says. “Unlike corn, its yield is largely independent of soil quality, though it does have similar water requirements per unit land area.”
The incentive to discover high-yielding biomass crops stems back to the Energy Independence and Security Act (EISA) mandated by Congress in 2007. EISA mandates that by 2022, the United States will produce 36 billion gallons of ethanol per year.
EISA has raised considerable concern about the amount of land that would be required to achieve these goals. Some projections suggest that the land needed would exceed current crop areas.
Long says an area of Miscanthus equivalent to 5.5 percent of the current 360 million acres of land used for grain, oil seed, pulse, fruit, and fiber production, would be needed to meet these mandates.
This land requirement is about half of the area placed into the Conservation Reserve Program. An alternative is to utilize these lands accordingly to plant feedstocks for lignocellulosic biofuels.
“Miscanthus is not the only opportunity in the United States,” Long says. “In fact, it’s not suitable for dry areas in our country, and much of the land west of the Missouri River. It’s also not suitable to strongly sloped lands or rocky lands, where productive trees represent an important feedstock for cellulosic ethanol.”
In dry areas, agaves, a group of plants historically grown for alcoholic beverages and coarse fibers, can produce much more biomass per unit land area than Miscanthus, trees, corn, and other grain crops. Long says these feedstocks represent an important opportunity for utilizing the dry and abandoned lands of southwestern states.
In addition, miscanes (Miscanthus-sugarcane hybrids) are likely to produce high yields per acre in the southernmost United States. Woody biomass can also be harvested sustainably for lumber and paper, providing biofuel feedstock for some regions.
The greatest opportunity for lignocellulosic biofuel production is the diversity of available feedstock options, says Sarah Davis, adjunct assistant professor of plant biology.
“In any given location, crop feedstock choices can be based on the local environmental conditions, and species can be selected based on productivity and ecosystem services that may be unique to the region,” she says.
“New bioenergy crops that grow on otherwise unproductive lands may offer an economic opportunity for regions that lack other land-based resources.”
Researchers are currently studying Napier grass, which may be twice as productive as Miscanthus in the southern United States, reducing land requirements even further.
“The challenge remains that industry will need to invest in new plants that will last 30 years,” Long says. “Without a stable policy environment, these investments won’t be possible at the state and federal levels.”
Researchers from the University of California at Berkeley contributed to the study.
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