The ethanol business is a booming market, buoyed by several years of high gas prices. While hampered somewhat by falling petrol costs, the market is seeing support from big investors like GM and is producing millions of gallons fuel yearly, with pumps expanding across the country.
However, while most agree that moving away from reliance on insecure, depletable oil is a good thing, there are also significant downsides to corn ethanol production, the current primary form of ethanol produced. As discussed previously at DailyTech, corn ethanol is cited for higher food costs. Additionally, it may not be as green from a carbon perspective as people think.
Companies like Coskata are looking to use alternatives such as quick growing grasses or wood waste to fuel their ethanol production. Now a new study shows that not only does such production help to normalize food prices, it also helps cut down on excess atmospheric carbon.
A study from the University of Illinois confirms that some sources of biofuels can actually increase emissions of carbon dioxide, while others can decrease them. The key is what you grow and where you grow it.
The study compiled soil carbon information from dozens of other studies in order to get the big picture. What it observes is that the amount of carbon that exists in the soil is increased by letting decomposing plant matter sit and eventually be absorbed into the earth, while tilling and plowing decreases the carbon in the soil, releasing it into the atmosphere.
Explains Evan DeLucia, a professor of plant biology at Illinois, "From the time that John Deere invented the steel plow, which made it possible to break the prairie sod and begin farming this part of the world, the application of row crop agriculture to the Midwest has caused a reduction of soil carbon of about 50 percent The biggest terrestrial pool of carbon is in the soil. The top meter of soil holds more than three times the amount of carbon stored in either vegetation or the atmosphere, so if you do little things to change the amount of carbon in the soil it has a huge impact on the atmosphere and thus global warming."
Corn ethanol increases emissions, according to the study, because corn must be constantly replanted, and replanting requires tilling the fields. Switchgrass, Miscanthus, and other fast-growing grasses, however, require no tilling and can grow wild, greatly increasing the soil's carbon and decreasing emissions.
Furthermore, these sources have more carbon density than corn, so once cost-efficient ways are created to process them, cellulosic ethanol should require much less land to produce than corn ethanol.
The study is significant, says Professor DeLucia as currently 20 percent of the U.S.'s corn crop goes to ethanol. He describes "so we began with the hypothesis that it might be good for soil carbon to put a perennial biofuel crop on the landscape instead of corn."
From there they delved into massive amounts of information on soil carbon levels on land growing corn, sugar cane, Miscanthus, switchgrass and native prairie grasses, taking into consideration many factors.
They found that sugarcane, used greatly by Brazil's ethanol industry, is the worst offender when it comes to biofuels. Sugarcane planted on native land slashes the carbon content, releasing vast amounts of carbon into the air. Whereas perennial grasses add to soil carbon's base level each year, sugarcane land would require a century just to recover to the base level.
Corn showed similar, but lesser problems. These problems could be alleviated somewhat by leaving more of the corn stover (plant waste) on the field, but the carbon was still cut significantly.
Losses from the initial planting of Miscanthus, switchgrass or native perennial grasses by on converted corn or sugarcane land took very little time to be neutralized thanks to great yearly gains in soil carbon. Professor DeLucia states, "Consistent with our hypothesis, the perennial feedstocks like Miscanthus and switchgrass start building soil carbon very, very early on. From a purely carbon perspective, our research indicates that putting perennial biofuel crops on landscapes that are dominated by annual row crops will have a positive effect on soil carbon."
These conclusions, he says, walk the study unintentionally "seems to walk you right into the food for fuel debate". But he says that it just makes sense to plant grasses as biofuel feedstocks, even from a purely carbon-conscious perspective.
The research will be featured in the journal Global Change Biology Bioenergy next month.
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