Ethanol Update: Switchgrass, Corn, And … Watermelon?
20 May 2009 US-based Ceres Inc., which develops and markets high-yielding energy crops for cellulosic ethanol production and biopower, announced that switchgrass can produce substantially more biomass than previously reported. Additionally, average yields — used to forecast bioenergy economics and environmental benefits — could be far too conservative.
Yield results from Ceres’ nation-wide network of field trials showed that average biomass yields among last season’s switchgrass tests were as high as 50% over the government’s projected yields for 2022.
California reported the highest yield, where a Ceres experimental variety produced 19 tons per acre. Proprietary varieties sold under the company’s Blade Energy Crops brand were consistently the highest yielding varieties across multiple trial locations, with average yields nearly 10 tons. Ceres switchgrass product manager Cory Christensen, Ph.D., predicted that “through trait development, better genetics and improved crop management practices, we can continue to increase average yields for many years to come.” Even using the government’s conservative projections, switchgrass sequesters more carbon than any other raw material evaluated by EPA, which released its official analysis on advanced biofuels earlier this month, says Ceres.
Current studies assume yields as low as two to four tons per acre for switchgrass. One highly regarded biofuel study co-authored by Sandia National Labs used a conservative six tons of biomass per acre for energy grasses, similar to estimates by the US Environmental Protection Agency (EPA). The new Ceres results could cause policymakers to re-think energy crop production assumptions. Ceres chief executive Richard Hamilton says that Ceres needs additional data before formally proposing new benchmarks, but said the “writing was on the wall.” He added: “These results are not surprising when you look at the impact that utilizing modern biology has had on food crop yields, like corn, which has seen a five-fold increase since the first hybrids were introduced.”
EPA Proposals Draw Scorn
In what could be good news for switchgrass but bad news for corn and other crop-based ethanol sources, biofuel proposals by EPA have had lawmakers on both sides of the aisle frowning, reports Platts. The agency’s plan to assess the “indirect effects” of biofuel production drew bipartisan condemnation from House representatives from farm states, who fear EPA’s standard could put an end to corn-based ethanol production. EPA’s proposed plan includes controversial measurements associated with land use, as the agency expressed desire for croplands to be used for food over fuel. Production and transportation of certain fuels, including ethanol and biodiesel — known as “significant indirect” emissions — also figure into the proposed plan.
“You are going to kill off the biofuels industry before it gets started,” Representative Collin Peterson, a Minnesota Democrat who chairs the full Agriculture Committee. Peterson vowed not to vote for any climate-change legislation unless corn-ethanol producers were protected. Representative Jerry Moran, a Kansas Republican, said he planned to introduce legislation that would prohibit EPA from using such an “indirect effect” standard until the science is better proven. “This industry is struggling to survive,” Moran said, adding that the indirect land use standard: “is one more nail” in the coffin of the industry.
Margo Oge, EPA director, said that under the proposed rule, 15 billion gallons of first generation corn-ethanol production was “grandfathered” in, and would not be trimmed back under the Renewable Fuels Standard. “We are very optimistic of the future of the second generation of biofuels,” she said, a telling referral to ethanol produced from cellulose and other farm waste, rather than corn-based ethanol. Critics say that corn-based ethanol actually creates more emissions than it removes from the environment.
Watermelon Could Diversify Sources
Adding another possible source to biofuel portfolios, US Department of Agriculture scientific agency Agricultural Research Service (ARS) studies have shown that simple sugars in watermelon juice can be made into ethanol. As opposed to growing the crop specifically for fuel, which could cause problems under the new EPA proposals, biofuel would be made from waste watermelon left after the food crop is harvested. In 2007, growers harvested four billion pounds of watermelon, while around 800 million pounds — 20% of the total — were left in fields to be plowed under because of external blemishes or deformities.
Chemist Wayne Fish’s ethanol studies at the ARS South Central Agricultural Research Laboratory in Lane, Oklahoma, US, showed ethanol can be fermented from the glucose, fructose, and sucrose in waste-stream juices — what’s left after nutraceuticals lycopene and citrulline are extracted. Making ethanol offers the potential benefits of helping to defray sewage treatment costs associated with nutraceutical extraction, says ARS, as well as providing watermelon growers with a new market for their crop.
On average, a 20-pound watermelon will yield about 1.4 pounds of sugar from the flesh and rind, from which about seven-tenths of a pound of ethanol can be derived. To extract all the possible sugars, Fish is seeking to degrade the rind with chemical and enzyme treatments. He’s also evaluating different combination of temperatures, yeasts, antifoaming agents, and pH levels to optimize the system.
Lane scientists also are examining annual ryegrass, sorghum and other crops that could be rotated with watermelons to furnish processing plants with a year-round supply of nutraceuticals or ethanol.
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