Finding power in pig waste

UNC chemist works to extract fuel, gases for electricity from stinky stuff nobody wants

Special CorrespondentJanuary 18, 2010 

  • Name: Jeffrey Macdonald

    Age: 48

    Job: Associate professor of biomedical engineering

    Family: Lives in Chapel Hill with his wife, Janet, and their daughters, Jade, 12 and Haley, 15

    Outside interests/hobbies: Skiing, surfing and sailing

    Why he's a scientist: "I love discovering and inventing new things."

  • N.C. hog farming

    The state's hog population more than tripled in the 1990s and has remained at about 9 million to 10 million since then. Eastern North Carolina is home to about 97 percent of them. Packed in football-field-sized warehouses, the animals produce nearly 19 million tons of waste per year, which is stored in about 4,000 open lagoons and sprayed on farmland and pastures as fertilizer.

In Eastern North Carolina, pig manure is serious business. Hogs outnumber people 3-to-1, and long-standing controversies about the environmental impact continue.

Now, a UNC-Chapel Hill associate professor has come up with a way to eliminate the noxious odor and recycle the waste into fuel alcohol and gases that can be used to make electricity.

The technology still is not cost-effective, but as the U.S. focuses on alternative sources of energy and utilities face requirements to tap renewable resources, the manure produced by 9 million pigs annually is looking, well, more attractive.

"Here is a resource going to waste," said Jeffrey Macdonald, a UNC associate biomedical engineering professor with a penchant for environmental causes.

After Macdonald became co-scientific director at the marine research institute in Beaufort two years ago, an idea germinated during his weekly 3-1/2-hour drives to the coast as sweet-and-sour hog manure odor permeated his car. Barack Obama was running for president, and green technology was a campaign issue. Gas prices topped $4 per gallon, and the marine research institute was in need of research funds.

So, Macdonald and one of his graduate students, Andrey Tikunov, went to work on the idea.

They designed a bioreactor and built a prototype using pipes filled with water and bacteria to separate and digest the many oils and nutrients in the hog manure. To improve the bioreactor's efficiency, they dressed up in rubber boots, body suits, gloves and masks to collect manure samples and analyzed them with the help of nuclear magnetic resonance spectroscopy, a tool used to diagnose cancer.

In May, Macdonald formed a startup company called BioRxn. UNC owns a small piece of the company and stands to earn royalties if and when the first bioreactors are sold and installed on hog farms. Once the research funding is approved, BioRxn will hire its first employees. For now, the work is supported by three researchers from Macdonald's UNC laboratory in Chapel Hill and a consultant, Michael Van Hoy, whose day job is technology manager at BD Technologies, New Jersey-based Becton Dickinson's corporate research center in Research Triangle Park.

"I think Jeff and the team have the technology and the expertise to address the problem better than others," Van Hoy said.

North Carolina's hog manure lagoons and sprayfields are heavily regulated. Despite the regulations, spills have killed fish. Sprayfields have fouled drinking wells. Nitrogen pollution has caused algal blooms and shellfish diseases, threatening streams and estuaries.

Little change on the farms

In 2000, the two largest hog growers in Eastern North Carolina agreed to fund a five-year, $17 million initiative to devise new waste management technologies.

In 2007, North Carolina became the first state to ban the expansion and construction of lagoons. The legislature also encouraged electric utilities to start looking at renewable energy resources. But on hog farms, not much has changed, said Mike Williams, who heads the animal and poultry waste management center at N.C. State University and oversaw the initiative.

"The main issue is cost," Williams said.

An analysis by RTI International, a research institute in Research Triangle Park, figured that technologies targeted by the initiative would have been up to four times more expensive than lagoons and sprayfields and could have required a reduction of the state's swine herd by as much as 50 percent.

Enter the new bioreactor. Macdonald and Tikunov conceived their bioreactor with the water cleaning mechanism of a fish tank in mind.

The design is elegant - simple yet versatile.

A set of pipes and tubes are assembled in a module shaped like the letter "m." The BioRxn bioreactor consists of three modules, each with a specific purpose. Van Hoy compared what happens to the grayish-brown hog manure as it is vacuumed through the pipes to what happens to food as it passes through the mouth, the stomach and the intestines.

In the first module, bacteria zero in on cellulose, the fibrous scaffolding that strengthens plant cells. Hog manure is full of cellulose. Bacteria in the second module help turn the cellulose into ethanol, or fuel alcohol, and in the third module, they produce two gases from the remaining material - carbon dioxide, or CO {-2}, and methane.

A BioRxn bioreactor to produce ethanol, methane and CO {-2} from the waste of about 1,000 pigs would fit into a one-car garage.

"We take the waste and create higher-value products," Van Hoy said. The goal is to come up with an efficient bioreactor that doesn't cost the hog farmers more than they gain from it, he said.

The hog farmers could sell the CO {-2}, which is used for many industrial purposes, including cooling and storing, pharmaceutical production and metal hardening. Methane can be burned to generate electricity, which the farmers could use on the farm or sell to the grid. Ethanol could be used as fuel for machinery and vehicles.

Water and fertilizer also remain. But the odor is gone.

Making it pay for farmers

The development of the bioreactor is in the early stages, and crunching the numbers is on the BioRxn team's to-do list next. The parts for it are not expensive. But Van Hoy acknowledged that without carbon credits or a better payoff for selling electricity to the electric grid, farmers aren't likely to spend money on new technologies.

Hog farms have had an opportunity for some time to capture methane, a potent greenhouse gas that forms naturally in the lagoons, said Vernon Cox, chief of the technical services section at the state Division of Soil and Water Conservation.

"But the economic incentive is not adequate to generate widespread adoption," Cox said.

His hope rests on another state law the legislature passed in 2007. It requires utilities to generate a small percentage of retail sales from power made with renewable sources, including hog and chicken waste. The requirements will take effect in 2012.

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