Perspectives On Line

NC State University

Spring 2001 Contents Page Features Where the Rare Things Grow Approaching the Green Coast GuardsAn Energetic Solution College Profile Noteworthy News Giving Alumni From the Dean College of Agriculture & Life Sciences  




























The belt system addresses
problems in the barn,
where they first occur, un-
like other waste manage-
ment technologies that
deal with waste after it
leaves the barn.









An Energetic Solution
  Photo by Herman Lankford

team of College of Agriculture and Life Sciences researchers is studying the feasibility of turning pig manure into ethanol, which could be used as fuel for automobiles.

If the strategy the researchers have mapped out proves feasible, they believe it will address many of the waste management headaches the North Carolina swine industry now faces and perhaps produce a new industry for rural parts of the state.

At the heart of the plan is a process called gasification, said Dr. Jeanne Koger, project director. Other members of the team are Dr. Theo van Kempen, a swine nutritionist, and Dr. Ada Wossink, an economist.

Gasification, Koger explained, is the process of burning a substance in a low-oxygen environment to convert complex organic compounds to gases. Koger and van Kempen plan to gasify pig manure, releasing gases such as methane, carbon monoxide and hydrogen. The gases will be collected and used to make fuel-grade ethanol.

Koger said there is a ready market for ethanol in state-owned vehicles that have been converted to run on ethanol, which burns more cleanly than gasoline. Indeed, some of the funding for the project is coming from the state Energy Office, which is looking for ethanol sources.

But the project encompasses considerably more than gasifying manure. Before manure can be gasified, it must be relatively dry, Koger said. That’s a problem in North Carolina, where swine waste is usually diluted with water in lagoons.

Koger said manure must be 60 to 80 percent dry matter before it can be gasified successfully. The manure in a lagoon is typically about 1 percent dry matter, while fresh feces are about 30 percent dry matter.

The barns in which pigs are raised usually have slotted concrete floors. Swine waste drops through the slots to a pit below. From there, the waste is flushed into a lagoon. The researchers propose using a belt system to collect and dry manure. The belt, located under the slotted floor, acts as a conveyer, moving manure to the end of the barn, where it can be collected.

Koger said it should be possible to retrofit swine barns with plastic belts. The belts will be positioned at an angle so that urine runs off while solid waste remains on the belt. When solid waste is separated on the belt, it dries fairly quickly, Koger said. The researchers have already experimented with a pilot system that treated waste from 15 pigs. Using the pilot system, they were able to produce manure that was 55 to 75 percent dry matter.

Belt manure collection systems are already in use in Europe, van Kempen said, and some of the support for the project is coming from a company that makes belt systems.

Koger said using a belt system should address two major headaches for hog farmers: odor and ammonia emissions. Both odor and ammonia are produced by the action of fecal microbes on the manure constituents, she said. If urine and solid waste are separated and the feces dried, odor and ammonia emissions should be reduced dramatically. Based on previous research, ammonia reductions of at least 80 percent are expected from a belt system. The belt system addresses these problems in the barn, where they first occur, unlike other waste management technologies that deal with waste after it leaves the barn.

Ammonia is a problem because it can volatilize and move into the atmosphere. It may later come back to earth dissolved in rain water. Ammonia is a form of nitrogen, which is a nutrient. Excess nitrogen in waterways can fuel algae blooms. The algae then die, and decomposition of the plants depletes the oxygen in the water, which can lead to fish kills.

The researchers have satisfied themselves that pig manure can be gasified. They sent manure samples to ThermoChem, a Baltimore company, which successfully gasified the samples.

Koger, van Kempen and Wossink see a number of advantages to the waste treatment system they envision. They describe the system as “holistic,” explaining that it uses all the wastes from a swine operation without negatively affecting the environment.

The system should provide substantial odor and ammonia emission control. It will not be seasonal in nature, as is the lagoon-and-spray-field system now used by most North Carolina farmers. Lagoon liquid is sprayed on fields as a fertilizer, but the plants that use the nutrients in the waste grow more actively and take up more nutrients during the growing season. Ethanol can be manufactured and used year round.

Because manure would be dried and taken to a gasification facility, the system requires relatively little land for waste storage or treatment. And the system would not require an open waste storage or treatment facility, like a lagoon.

Koger said the system should be particularly suitable for areas like Sampson and Duplin counties, with large swine populations in a relatively small area. Were gasification facilities to be located in these counties, there should be no shortage of manure (each county has around 2 million pigs). At the same time, the distance from any given farm to a facility would be minimal, so the cost of moving manure should be reasonable. Gasification facilities also would represent a new industry for the area.

The researchers see one other potential benefit from the system. In addition to producing gases, gasification also makes ash. The ash contains the minerals that were in the manure, van Kempen said, and should have value as either a fertilizer or an animal-feed supplement. The ash might end up going back to the hog farms from which it came, where it would become part of the pigs’ diet. The ash would be completely safe to use as a feed supplement, van Kempen pointed out, because any pathogens in the manure would be destroyed by the extreme temperatures (in excess of 1,100 degrees F) used to gasify the manure.

The researchers plan over a two-year period to determine the feasibility of retrofitting barns with belts, then collecting, drying and gasifying manure. The next step, which is being funded by the Animal and Poultry Waste Management Center at N.C. State, is to build and test a prototype belt collection system.

Koger said that they anticipate the system will manage waste from approximately 120 pigs. The prototype will be located either on N.C. State’s campus or at the university’s Lake Wheeler Road Field Laboratory, just south of Raleigh. Using data from the prototype, Wossink will determine if the strategy is economically feasible.


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