Viable alternative: Engineer works to turn waste management byproduct from hog farms into fuel source
Dr. Jay Cheng is working on a number of processes to convert cellulose into ethanol.
Photo by Becky Kirkland
Finding new management alternatives for agricultural wastes - and particularly those associated with hog production - was seen as one of the state's biggest issues during the 1990s. While today's headlines are more likely to highlight another problem - that of rising energy prices - N.C. State University's Jay Cheng believes that in the coming decade, one problem might help solve the other.
Cheng is an associate professor with the College of Agriculture and Life Sciences' Department of Biological and Agricultural Engineering. In recent years, he's been applying his knowledge of chemical, biological and environmental engineering to find ways to convert wastes of animal production into valuable energy sources such as methane and ethanol.
In North Carolina, most hog farms get rid of manure by allowing it to digest in lagoons, then spraying it onto fields to fertilize Bermuda grass that's been planted there. The Bermuda grass removes nutrients from the waste, keeping it out of water in underground aquifers and out of surface water sources such as lakes and rivers.
Cheng knows of one swine producer who then bales the hay and gives it to a neighbor, who in turn uses it to enhance his soil. But most farmers haven't figured out anything useful to do with the hay, he says.
"The problem is that there is almost no market for Bermuda grass in the eastern part of North Carolina, where most hog farms are," he says. "In the western part of the state, there is a small market for Bermuda grass for the dairy industry. But they usually get hay from the Midwest.
"So that led me to think, 'What can we do with the Bermuda grass?' And in 1999 I started work on a process of converting Bermuda grass to ethanol."
Over the years, he developed a three-stage process of pretreating plants, breaking down their cellulose into sugars and then fermenting the sugars to convert them into ethanol.
It worked, but there were problems that kept it from becoming a commercially viable process for creating alternative fuels. Petroleum-based fuels were cheaper, and so was ethanol derived from the starch in corn.
Today, a changed competitive environment allows Cheng to see new opportunities for cellulose-derived ethanol: While there's increased interest in expanding ethanol production to meet the demand for clean-burning and affordable fuel, most of the world's ethanol is produced by converting starch from corn. And there's only so much land where U.S. farmers can produce corn for food, feed and fuel to compete with the petroleum market, Cheng says.
Plants rich in cellulose, such as switchgrass and Bermuda grass, on the other hand, can grow on marginal lands. And there is already an abundant supply that isn't being tapped, he says. In addition to the Bermuda grass grown as part of hog-farming operations, forests represent yet another vast potential source for cellulose-derived fuel.
Meanwhile, Cheng explains, an enzyme-producing company in the Research Triangle Park has found ways to reduce by eightfold the cost of producing enzymes needed to turn cellulose into ethanol. And that savings moves the potential for cellulose-based energy closer to being commercially viable.
Cheng is now working with that company to test the new, genetically engineered enzymes. And he's working with other scientists and engineers on different processes to convert cellulose into ethanol.
In addition, Cheng is exploring the possibility of bringing his technology out of the lab and applying it on a larger scale in a more real-world setting. Such a pilot project will allow scientists to fine tune the process while also giving them the chance to better evaluate the production costs.
While there's much work to be done, Cheng says he's "pretty confident" that the technology can be developed to the point where it will be economically feasible.
"Sometimes with one stone you can hit two birds," he says. "On the one hand, our producers have almost no market for Bermuda grass, and this would create a market. And sooner or later, crude oil will be gone, and so we have to find some viable alternatives."
- Dee Shore
Cheng is an associate professor with the College of Agriculture and Life Sciences' Department of Biological and Agricultural Engineering. In recent years, he's been applying his knowledge of chemical, biological and environmental engineering to find ways to convert wastes of animal production into valuable energy sources such as methane and ethanol.
In North Carolina, most hog farms get rid of manure by allowing it to digest in lagoons, then spraying it onto fields to fertilize Bermuda grass that's been planted there. The Bermuda grass removes nutrients from the waste, keeping it out of water in underground aquifers and out of surface water sources such as lakes and rivers.
Cheng knows of one swine producer who then bales the hay and gives it to a neighbor, who in turn uses it to enhance his soil. But most farmers haven't figured out anything useful to do with the hay, he says.
"The problem is that there is almost no market for Bermuda grass in the eastern part of North Carolina, where most hog farms are," he says. "In the western part of the state, there is a small market for Bermuda grass for the dairy industry. But they usually get hay from the Midwest.
"So that led me to think, 'What can we do with the Bermuda grass?' And in 1999 I started work on a process of converting Bermuda grass to ethanol."
Over the years, he developed a three-stage process of pretreating plants, breaking down their cellulose into sugars and then fermenting the sugars to convert them into ethanol.
It worked, but there were problems that kept it from becoming a commercially viable process for creating alternative fuels. Petroleum-based fuels were cheaper, and so was ethanol derived from the starch in corn.
Today, a changed competitive environment allows Cheng to see new opportunities for cellulose-derived ethanol: While there's increased interest in expanding ethanol production to meet the demand for clean-burning and affordable fuel, most of the world's ethanol is produced by converting starch from corn. And there's only so much land where U.S. farmers can produce corn for food, feed and fuel to compete with the petroleum market, Cheng says.
Plants rich in cellulose, such as switchgrass and Bermuda grass, on the other hand, can grow on marginal lands. And there is already an abundant supply that isn't being tapped, he says. In addition to the Bermuda grass grown as part of hog-farming operations, forests represent yet another vast potential source for cellulose-derived fuel.
Meanwhile, Cheng explains, an enzyme-producing company in the Research Triangle Park has found ways to reduce by eightfold the cost of producing enzymes needed to turn cellulose into ethanol. And that savings moves the potential for cellulose-based energy closer to being commercially viable.
Cheng is now working with that company to test the new, genetically engineered enzymes. And he's working with other scientists and engineers on different processes to convert cellulose into ethanol.
In addition, Cheng is exploring the possibility of bringing his technology out of the lab and applying it on a larger scale in a more real-world setting. Such a pilot project will allow scientists to fine tune the process while also giving them the chance to better evaluate the production costs.
While there's much work to be done, Cheng says he's "pretty confident" that the technology can be developed to the point where it will be economically feasible.
"Sometimes with one stone you can hit two birds," he says. "On the one hand, our producers have almost no market for Bermuda grass, and this would create a market. And sooner or later, crude oil will be gone, and so we have to find some viable alternatives."
- Dee Shore