April 20, 2004

Researchers Turn Hog Manure Into Oil

You've heard of Big Oil. How about Pig Oil?, reports the New York Times. The process is far from perfected, but an agricultural engineer at the University of Illinois in Urbana-Champaign has reported success in turning hog manure into oil.

"Scientifically, yes, we did convert manure to oil," said Dr. Yuanhui Zhang, a professor in the department of agricultural and biological engineering. "But to compete with Mobil and Amoco, we still have a long way to go."

Dr. Zhang, who has been researching manure conversion for eight years, subjects a waste slurry to heat and pressure in a process called thermochemical conversion. Long hydrocarbon chains break down into shorter ones, and along with some methane, carbon dioxide and water, oil is produced, "though it's not as good quality as the sweet crude we buy, yet," he said.

He has finished a batch process, converting about half a gallon at a time. He said it had a good energy return: "for every one portion of energy in, you get three portions of energy out."

The next step is to develop a continuous process, then build a prototype conversion plant. Dr. Zhang envisions a future where every hog farm has one or more converters, about the size of a home furnace, producing oil that is trucked or piped to a central facility for further refining.

Thermochemical conversion of waste to fuel was in vogue among researchers during the oil-crisis years of the 1970's, when scientists tried to make fuel from wood sludge and other materials. It proved too costly then, but there are now some other waste-to-fuel projects around.

Dr. Zhang said he undertook the research partly to find a way to produce alternative fuel but also because it provided a potential solution to the disposal of waste on modern hog farms. "It's a no-cost material or even a negative-cost material," he said.

Dr. Zhang said manure had another advantage over other raw materials like wood sludge: the pig has already done much of the work. "It's easier to process because it's been preprocessed biologically," he said.

His process would also work with chicken or cow manure, though it would have to be modified. Human waste would work with little or no modification.

"Humans eat similar things," Dr. Zhang said. "People hate to hear that, but indeed humans are much closer to pigs."

"I mean physiologically," he added.

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