Emissions, Renewables

Swine Waste: Generates Electricity in North Carolina

Issue 11 and Volume 118.

A fully remote controlled Guascor SFGLD 480 gen-set provided by Dresser-Rand produces 600kW of power
A fully remote controlled Guascor SFGLD 480 gen-set provided by Dresser-Rand produces 600kW of power. Biogas from Storms Hog Farm is combusted in the engine/generator to produce enough power for nearly 300 average North Carolina homes. The new power plant has been operating at full capacity since June 2014. Photo courtesy: Dresser-Rand

By Chris Nagle, Dresser-Rand

Bladenboro is a small town in Southeastern North Carolina with just under 2,000 residents. Originally known for its timber and turpentine, it is now in the heart of hog country.

Some 10 million pigs can be found in the southeastern region just east of Interstate 95, making North Carolina the second leading hog producer in the United States.

Many of the residents in Bladenboro can thank the nearly 30,000 hogs that live at Storms Hog Farm for power that is now generated from North Carolina’s largest swine waste-to-energy system-the 600-kW Storms Hog Power Plant.

Manure collected daily from the hogs is biologically decomposed in an oxygen-free, 1.2-million gallon reinforced concrete vessel, or tank, known as an anaerobic digester. The bacteria in the digester metabolically break down the waste and generate biogas, while destroying nearly all of the pathogens and odor.

The biogas is combusted in an engine/generator, sending enough clean renewable electricity to the local utility to offset the electricity consumption of nearly 300 average-size homes in the area. The new power plant has been operating at full capacity since June 2014.

The bacteria in the digester metabolically breaks down the waste and generate biogas, while destroying nearly all of the pathogens and odor. Photo courtesy: Dresser-Rand
The bacteria in the digester metabolically breaks down the waste and generate biogas, while destroying nearly all of the pathogens and odor. Photo courtesy: Dresser-Rand

History of Hog Waste Management

Southeastern North Carolina’s hog farms historically stored more than 350,000 gallons of manure produced each week in open-air lagoons and mixed with off-site agricultural wastes, which were previously either land-applied or destined for a landfill.

When designed correctly, the sewage in a lagoon quickly decomposes through exposure to sunlight and oxygen. The challenges that can arise from such an arrangement include the strong potential for noxious odors and flooding from storms which could potentially contaminate water supply.

A New Direction

The concept for the waste-to-energy project evolved from a grant for four swine farm renewable energy pilot projects administered by the North Carolina Department of Energy. These grants were applied for in May 2010 by Storms Hog Farm.

The farm ultimately hired AgPower Partners LLC to develop the project, which in turn enlisted DVO, Inc. for its anaerobic digester experience and Martin Machinery/GenTec for its biogas engine/generator turn-key services.

Some of the preliminary plans to generate energy at the farm started with biogas boilers that operated through the anaerobic digesters and ultimately flared gas. Known for his interest in renewable energy, William R. Storms, the farm owner and operator, initially had a desire for the power plant to produce 1,200 kW of electricity.

Ultimately it was determined that a 600kW power plant would be the best path to take because of the incentives that come by developing a waste-to-power plant through the Power Purchase Agreement with North Carolina.

The team decided to reduce the size of the power plant to 600kW because they wanted to be sure it would work on a smaller scale before ultimately expanding later to a 1,200kW plant.

DVO installed its patented Two-Stage Mixed Plug Flow anaerobic digester and Martin Machinery/GenTec highly recommended the installation of a fully remote controlled Guascor SFGLD 480 gen-set provided by Dresser-Rand to produce the 600kW output.

The new power plant was designed to collect manure from the hog barns and then transport the waste by truck then conveyor belt, into the digester which holds 1.2 million gallons of wastewater. Inside the enclosure, bacteria decompose the manure, producing methane that’s collected to combust the electric generator.

Specifically developed to work with natural gas, biogas from landfill, sewage and anaerobic digestion processes, or gases from biomass gasification processes, Dresser-Rand’s Guascor SFGLD engines are equipped with air-fuel ratio controls and adaptable to any type of low heat value (LHV) gas.

Dresser-Rand’s Guascor SFGLD engine series has been tested successfully with product gases from many different sources, including: landfill, waste water treatment plants, animal manure digestion processes, farm waste, cassava, starch, wine dredges, palm oil mill effluent (POME), and more.

The SFGLD engine was chosen primarily for its long history of performance and reliability. There are over 300 Guascor units installed across North America, with a success rate measured in runtimes of 95 percent or more. The outstanding performance and reliability of the Guascor engine in other locations was a key selling point for the farm. It was also chosen with a possible expansion in mind. If the unit was successful in its uptime performance, then another unit would later be installed at the facility, doubling the size to a 1,200 kW plant.

Biogas from Storms Hog Farm is piped to the utility building housing the generator set used to produce 600 kW of power. Photo courtesy: Dresser-Rand
Biogas from Storms Hog Farm is piped to the utility building housing the generator set used to produce 600 kW of power. Photo courtesy: Dresser-Rand

The new anaerobic digester and renewable energy-generating system, along with an enhanced animal waste extraction and collection systems that uses scrapers instead of flush water to remove manure from the houses, greatly reduced the negative environmental impacts of the lagoon and manure management systems. The result is cost-effective generation of renewable energy.

The digester produces wastewater that is free of pathogens and odors and the power plant’s new nutrient recovery technologies allow for the practical removal of additional phosphorus and ammonia nitrogen. Some excess gas is flared at the site.

Storms Hog Power now sells its electricity output to the N.C. Electric Membership Corp., and Duke Energy buys renewable energy certificates from Storms Hog Power which can be accumulated to meet the state’s mandate for clean energy. Other benefits from the power plant include reduced diesel consumption for power generation.

With the success and high performance of the 600kW plant, Storms Hog Farm is currently in the process of expanding and doubling the electrical output. A new Dresser-Rand Guascor SFGLD 480 gen-set provided by Martin Machinery will be the unit of choice.

Author

Chris Nagle is the general manager for engines and small gas turbines in North America at Dresser-Rand.

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