February 20th, 2007
Can wild grass produce clean fuel?
As many other countries, the U.S. want to reduce their dependency on oil by increasing the production of renewable and alternative fuels. Today, the main source of biofuel is ethanol distilled from kernels of corn, with a production of 5 billion gallons a year. As current targets for biofuels have been pushed to 7.5 billion gallons by 2012 and 35 in 2017, using corn ethanol alone would require to convert the combined size of Kansas and Iowa into farmland. But researchers have studied other solutions. And the best one could be to use cellulosic ethanol as the fuel of the future. The main advantage of using a wild grass named miscanthus is that you can produce ethanol from the whole plant body as opposed to corn where you can only use the grains. The other one is that you would need to grow this plant only on an area of the size of Massachusetts — an area 18 times smaller. But will farmers follow this advice? Time will tell.
This suggestion comes from Chris Somerville, professor of biological sciences at Stanford University and director of the Carnegie Institution's Department of Plant Biology, who studies how polysaccharides, such as cellulose, can be used as a source of biofuel for a number of years.
First, let's look at a chart comparing the respective profits you could expect from the utilization of corn, switchgrass and miscanthus to produce ethanol (Credit: Chris Somerville). This chart comes from slide #55 of a presentation that Somerville gave at the Carnegie Institution in Washington on May 6, 2006, "The future of Biofuels" (PowerPoint format, 58 slides, 18.9 MB).
Now, why did he focus his research on this perennial grass?
The body of a plant is composed of polysaccharides, such as cellulose, which can be converted to ethanol by fermentation. Using the entire plant body as a starting raw material will result in a higher yield of fermentable sugar per unit of land, Somerville said. The ideal plant for producing cellulosic ethanol, he added, is Miscanthus, a perennial grass native to subtropical and tropical regions of Africa and southern Asia, which is used as an ornamental plant in the United States.
And here are some more reasons to use miscanthus.
"It uses less water per gram of biomass produced than other plants," he said. "For example, to make a pound of alfalfa or spinach requires about 600 pounds of water, while to grow a pound of Miscanthus requires only about 200 pounds of water." According to Somerville, Miscanthus produces about twice as much biomass per acre without irrigation than other grasses, and reaching the president's target of 35 billion gallons of biofuels annually would require putting far fewer acres of land into Miscanthus production.
Obviously, this research work has been widely commented by the media. As an example, here is a link to an article from ScienceNOW, "Using the Body, Not the Seed."
And if you want to know more about miscanthus, here are two pages carrying lots of references, the first one at Wikipedia and the second one at Oak Ridge National Laboratory.
Sources: Stanford University news release, February 16, 2007; and various other websites
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