Unlocking the energy in yard clippings, corn stalks and leaves may get much easier, according to a recent study.
That would help bioenergy producers switch to cheaper sources that cause fewer environmental headaches. What’s more, it may mean less reliance on plants that people eat.
The study treated plants with ammonia to convert them to fuel more quickly.
Converting second generation sources, like corn stalks and switchgrass, to biofuels is easier when they're pre-treated with ammonia, according to researchers. Photo: mae.noelle (Flickr)
Typically, extracting energy from plants is tedious, expensive and time-consuming.
To make ethanol, sugars are treated with enzymes.
Ammonia loosens the cell structure, making it easier for the enzymes to get to work, said Shishir Chundawat, a research associate at Michigan State University and lead author of the study.
The ammonia breaks through compounds that defend plants from tiny cellulose-seeking organisms, said John Greenler, director of education and outreach at the Great Lakes Bioenergy Research Center.
So what’s the big deal?
Most bioenergy is made from first generation sources, like vegetable and animal fats or starch from grains. That’s because they don’t have the rigid cellulose.
But there is a drawback to using them: They are also used for food.
“There’s a potential that this type of bioenergy production raises food prices,” Greenler said. “And if we can get away from these first generation biofuels, we can reduce greenhouse gas emissions and the releasing of nitrogen into the atmosphere.”
First generation sources rely on fossil fuels for things like fertilizer and tractors. And corn-based ethanol plants require coal and natural gas.
But using ammonia to help convert second-generation sources, like corn stalks, switchgrass and leaves, is much less energy intensive. And people don’t eat them.
Additionally, ethanol from cellulose reduces green house gas emissions by 90 percent, when compared to gasoline, according to the U.S. Department of Energy. Corn-based ethanol decreases emissions by approximately 10 to 20 percent.
Sometimes second-generation sources are treated with potentially toxic chemicals to loosen the cellulose bonds.
But the ammonia could help eliminate their use — making second-generation biomass much more efficient. It costs approximately $2.20 per gallon to produce ethanol from cellulose, which is twice as much as ethanol from corn, according to the U.S. Department of Energy.
“We really like that it (ammonia) doesn’t produce a lot of toxic compounds and should be easy to recycle,” Greenler said. “There won’t be a lot of expense or pollution.”
The idea of using ammonia isn’t entirely new. Manure contains ammonia and can be used as biomass.
“We don’t need ammonia, we use manures,” said Nick Nelson, president of Midwest Biogas. “When we use second generation sources we blow right past that step (adding ammonia) and co-digest stuff together.”
Manure works for methane production. But to make ethanol, the ammonia must be added to loosen the cellulose.
According to Greenler, the research is a “big step” towards getting away from first generation biofuels.
“First generation bionenergy, like corn grain for ethanol, has been a really important learning experience in this region but most people recognize that long-term potential is limited,” he said.
“We’ve hit a ceiling on what we can do and we need to look further forward to meet renewable fuels standards.”