Scientists Work to Clean Up Hog Waste 'Lagoons'

by 5m Editor
10 June 2004, at 12:00am

US - When Hurricane Floyd hit the state of North Carolina in 1999, it left more than rain puddles in its wake. The downpour caused lagoons of hog waste to overflow. North Carolina is the second largest hog producer in the United States. Its 10 million pigs generate 19 million tons of waste a year.

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While the industry is tightly regulated and a moratorium has halted the construction of any new lagoons, public concern over the impact of waste on water, soil and air prompted the state's two largest hog producers to put $17.3 million into the development of new ways to limit and treat waste. Researchers at North Carolina State University are evaluating sixteen technologies. The hog industry is hoping the results provide new options that are both environmentally sound and economically feasible. VOA's Rosanne Skirble visited a full-scale demonstration project in Clinton, North Carolina.

Goshen Ridge Farms is a typical swine production farm in North Carolina. It houses 13,000 hogs, which live tightly together in close quarters in indoor pens over metal grates. Their waste is flushed into large pits or lagoons, where it biodegrades naturally. Excess water from the process is sprayed onto fields as fertilizer. The problem is the waste smells. It pollutes groundwater and it spreads pathogens.

About two years ago, Ray Campbell was charged with implementing a radical new plan that would address these issues. The idea was to eliminate the lagoon. Mr. Campbell is Vice President for Research and Development at Super Soil Systems USA, the company that designed the project combining technologies developed in Spain, Japan and at the U.S. Department of Agriculture (USDA). Ray Campbell says the process begins at the hog house with the separation of the solids and liquids.

"There is solids removal technology, nitrogen removal technology and phosphorus removal technology," Mr. Campbell explains. "There is a pond of water under the floors that are suspended over it. They collect the solids. That pit has water in it. We collect it and flush it. That water is then pumped over to a storage tank that you see right here and it is mixed before the processing. The wastewater is then pumped into the solids removal or modular system as we call it. A polymer is injected. It is mixed just right and then we screen off those flocs (clumping of suspended solids into larger particles) and collect them in the trailer. They are the solids that we are removing right now."

Next, the solids are trucked to a central plant where they are blended with other organic waste materials for composting. Sixty days later, it is ready for processing into potting soil or fertilizer.

The water that remains after the solids have been removed, goes to the second stage of treatment where harmful ammonia emissions and odors are further reduced by converting the remaining nitrogen to harmless nitrogen gas.

Ray Campbell: After that component the water goes through a third component which is the phosphorus removal system. That water after nitrogen removal in fact is ready to be used to refill the pits in the houses for the next waste collection. So this particular water represents what in the past was released to the lagoon for treatment. One thing that is a very significant improvement in this process is that the farmers traditionally used the same lagoon water to refill the waste collection pits, where we are using clean water for that so it is a clean environment.

Skirble: Right now we are looking at what once was a lagoon.

Ray Campbell: Yes, and this lagoon now, when we get a little closer to it is very clear looking and it is turning into a holding pond. Dr. Vanotti has taken samples of that lagoon for over a year and I'll let him share what he has learned about the nutrient content.

Matias Vanotti is a soil scientist with the USDA Research Service who is testing the new technology.

"Typically these lagoons contain anywhere from 400 to 700 parts per million of ammonia. After one year of discharging clear water from this process into the lagoon, the concentration of ammonia was reduced to less than 20 parts per million," he said. "We are also looking at a variety of water quality parameters including pathogens and all of these have been substantially reduced."

In addition to treating the hog waste, Mr. Campbell says the scientists want to go one step further, to totally clean out the lagoons.

Ray Campbell: We're going to pump the solids out of the bottom of this lagoon and demonstrate that this solids removal component could be mobilized, that is put on wheels and moved from farm to farm to clean up these lagoons that have either been abandoned or are near capacity as far as the solids that they can hold.

Skirble: What do you see as the direction and value of what is happening with this new technology?

Ray Campbell: The big difference here is that we are not only learning how to manage the nutrients in the waste, but we are removing the nutrients and moving them off the farm to areas where they are needed for crop production and food production. In most of these counties, where intensive animal production exists, there is not enough land to absorb all the nutrients in normal crop production. So, in addition to cleaning up the wastewater, we are removing the nutrients off the farm site, and in addition to that we are creating value-added products which is the ultimate solution to this problem.

The three-component operation is housed in a two-story building. The researchers have already built a much smaller unit that could fit into a 12-meter trailer. North Carolina State University's evaluation of the new technology is expected by July. After that the state must decide how to best implement these and other new practices on hog farms across North Carolina.

Source: Voice of America - 9th June 2004

5m Editor