About 10 years ago, Ronnie “Geno” Kennedy began to wonder whether the same bacteria used to clean up oil spills would eat the sludge from the bottom of hog manure lagoons.
After all, petroleum and lagoon sludge both form under anaerobic bacterial conditions. They also form many of the same chemical compounds — methane gas, hydrogen sulfide gas, alcohol compounds, low-pH organic acids, and highly toxic phenols.
Kennedy was concerned because, in his line of work, helping North Carolina pork producers meet environmental regulations, he was seeing some problems with sludge buildup and a resulting lack of lagoon effluent capacity.
In 1995, he called a company in the Midwest that sold bacteria for oil spill cleanup and proposed his idea.
“They were busy selling huge amounts of their product to companies to clean up these big oil spills and hardly thought I was worth talking to,” he says. “But I told them about the hog industry in North Carolina and how many lagoons were out there. They got excited about the possibilities.”
The company brought a compressor and some diffuser lines to lay on top of the sludge to help stir the lagoon water, Kennedy explains. They also brought many buckets of their product, put it into the old lagoon and lowered the sludge from 5 ft. to 1½ ft. within just a few months.
“They used a lot of product,” he adds.
At that rate, Kennedy knew the biological process would not save much, if any, money above mechanical methods of sludge cleanout. So he began experimenting with lower bacterial rates, longer time frames, and higher rates of diffused air to stir the lagoon water.
Today, Kennedy believes he's arrived at a winning combination of time, bacterial supplementation, air movement and economics. His company, Agriment Services, Inc. (ASI) has 22 systems in operation in his home state of North Carolina.
He says his combination over a period of three to five years will reduce sludge volumes 25% to 75%, and reduce emissions of hydrogen sulfide, among the most offensive odors from lagoons. Kennedy also says lagoons undergoing his treatment will have lower levels of biological oxygen demand (BOD), chemical oxygen demand (COD), volatile fatty acid (VFA), ammonia, total suspended solids and volatile solids concentration, and a higher redox potential.
Kennedy offers two cost comparisons. In one, he says conventional stirring and pumping costs from 2-8¢/gal. of actual sludge removed. His biological/air mixture has driven system costs down to ¾-1½¢/gal. of actual sludge removed.
In another comparison, he offers cost estimates from a real lagoon. With a need to remove 44,400 lbs. of sludge, conventional removal would cost $10,384 compared to $3,248 with his process. Breaking it down further, conventional removal costs $233.87/1,000 lbs. vs. $73.15/1,000 lbs. with his process.
Kennedy's price estimate of $10,000 for conventional sludge removal via dredging, or agitating and pumping, may actually be low in North Carolina, says Patrick Fussell, an environmental specialist with one of the state's soil and water conservation districts.
The cost eight or 10 years ago for complete mechanical closure of a lagoon of the size required to serve two finishing buildings was $10,000. Today, the same size lagoon could cost $40,000 to $60,000 to close.
Fussell is careful not to endorse Kennedy's system because of the nature of his job, but says he's seen some positive results. “I can't endorse it, but I can't say anything bad about it, either,” he says. “I hope it works out because it will be a lot cheaper for the farmers.”
Several of Kennedy's customers see this process as a pre-emptive measure, a way to spend a little money upfront to avoid spending a large amount later.
“My sludge wasn't a major problem when I started, and I'm using the system more as a preventive maintenance program,” says Bud Rivenbark, a Rose Hill, NC, contract hog producer.
Rivenbark says he had 2.5 ft. of sludge in his lagoon when he started with Kennedy's biological program more than two years ago. Sludge levels have dropped 8-10 in., he says.
“I've seen some pretty positive results from it and it's certainly been worth the money,” he adds.
He plans to add the biological system to his other lagoon this year.
How it Works
Kennedy's system begins with the addition of compressor-driven air diffusers lying on or in the sludge layer of the lagoon. It oxidizes the hydrogen sulfide and turns it into sulfate. That initial process helps to detoxify the lagoon and prepare it for organic matter breakdown.