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Converting swine manure to oil:
U of I process faster, easier
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[MARCH 26, 2004]  URBANA -- Swine manure might just be the surprising key to reducing crude oil imports and creating a new industry in the United States.

Swine manure is being converted to crude oil at the University of Illinois using a thermochemical conversion process. But researchers have refined this existing process to make it more efficient and faster. The economic impact of such technology could be dramatic.

"If 50 percent of swine farms adopted this technology, we could see a $1.5 billion reduction in crude oil imports every year," said Yuanhui Zhang, U of I agricultural engineer. "And swine producers could see a 10 percent increase in their income -- about $10 to $15 per hog."

In addition, Zhang said, the environmental benefits of this research are numerous. Minerals are preserved in the after-treatment stream, odor is reduced and the oxygen demand of manure is reduced by 70 percent.

Thermochemical conversion, or TCC, is a chemical process that reforms organic compounds in a heated and pressurized enclosure to produce oil and gas. The process that Zhang has developed uses swine manure as the organic material and coverts it to crude oil using a small-scale batch TCC reactor developed by Zhang's research team.

According to Zhang, they conducted a series of experiments on variables that affected the oil conversion efficiency and oil quality. As result, they were able to define the desirable temperature range for the process and reduce the retention time to about 15 minutes. Retention time is the time required for the manure to remain in the TCC processor to allow oil conversion.

"The process we have developed is quite different from most conventional TCC processes," said Zhang. "There is no need for the addition of a catalyst, and our process does not require pre-drying of the manure. Swine manure containing 80 percent water can be fed directly into the reactor."


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Zhang said that although the presence of water requires more energy to heat up the media, most of that energy can be recovered with a heat exchanger.

With the batch reactor, researchers achieved an average of 70 percent conversion from swine manure volatile solids to oil. At that conversion efficiency, the manure excreted by one pig during the production cycle could produce up to 21 gallons of crude oil. What's more, a swine farm producing 10,000 market hogs per year could produce 5,000 barrels of crude oil per year.

"We further processed the TCC crude oil in our lab and obtained refined oil that had a heating value similar to that of diesel fuel," Zhang said.

The next step for Zhang's research team is to develop the batch process into a continuous-mode process.

"In a continuous TCC process, the heat generated from the process can be recycled more efficiently, reducing the operating costs," said Zhang. "Reactor volume can be reduced for the same capacity, which reduces the investment costs, and automated controls can be adapted more readily, which reduces the labor costs."

Eventually, Zhang hopes to develop a TCC pilot plant, which will increase production capacity and allow them to analyze the oil properties and seek alternative applications of the TCC oil, such as making plastics or ink.

"Developing a continuous TCC reactor will advance this technology one step closer to a TCC pilot plant," said Zhang.

Zhang's research proposal was approved for funding under the Grainger Emerging Technology Program in the College of Engineering and awarded $100,000.

[University of Illinois news release]


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