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article imageDuke Energy turning waste from hog farms into electricity

By Karen Graham     Mar 31, 2018 in Technology
Charlotte - A Duke Energy power plant is using renewable natural gas from North Carolina-based hog farms to produce electricity – the first application of the technology from in-state farms.
The newly-completed renewable energy project in Duplin County, North Carolina, called Optima KV, will help Duke Energy to comply with North Carolina’s Renewable Energy and Energy Efficiency Portfolio Standard law (REPS), established in August 2007.
The law mandates that all investor-owned utilities in the state must supply 12.5 percent of 2020 retail electricity sales from eligible energy resources by 2021. Headquartered in Charlotte, North Carolina, Duke Energy’s Gas Utilities and Infrastructure business unit distributes natural gas to around 1.6 million customers in the Carolinas, Ohio, Kentucky, and Tennessee.
The Optima KV project was first announced in 2016 when Duke Energy and Optima Bio got together on the project. It is expected to yield about 11,000 megawatt-hours of electricity—enough to power about 1,000 homes.
This is one of many designs for digesters that are used to capture biogas. RCM Digesters feature wha...
This is one of many designs for digesters that are used to capture biogas. RCM Digesters feature what is called plug-flow system.
RCM Digesters
Basically, the process captures methane gas from hog waste at five local hog farms. The project uses a technology called digesters installed at the pork farms of Smithfield Foods in Kenansville, North Carolina. Digesters hold the waste in heated, airtight tanks, which creates ideal growing conditions for bacteria that consume the manure and release methane gas.
Using more than 42,000 feet of in-ground piping, the methane is moved to a central location where the gas is cleaned and converted to pipeline-quality natural gas. The cleaned natural gas or renewable natural gas is then injected into the Piedmont Natural Gas system where it's piped to Duke Energy’s Smith Energy Complex in Richmond County and converted into electricity.
Optima KV completed its interconnection to Piedmont Natural Gas last week, according to a news release from Duke Energy.
Waste from hog farms is being used to produce renewable natural gas.
Waste from hog farms is being used to produce renewable natural gas.
"This is a major breakthrough for renewable energy in North Carolina," said David Fountain, Duke Energy's North Carolina president. "This project allows for the capture of emissions from hog operations and converts the renewable natural gas to electricity for customers. We look forward to continuing our work on future projects."
The use of renewable natural gas
"Historically, renewable natural gas has been used by smaller, on-site generators that are connected to the overall energy grid," according to Duke Energy. However, the utility points out that having more efficient plants allows more renewable energy to be created with the same amount of renewable natural gas.
Swine-waste-to-energy is starting to take off in other areas, as well. In October 2017, Virginia-based Smithfield Foods announced the launch of Smithfield Renewables, a new environmental initiative to accelerate the company’s carbon reduction and renewable energy efforts. Smithfield is the world's largest pork processor and hog producer.
Smithfield processing plant in Smithfield  Virginia
Smithfield processing plant in Smithfield, Virginia
"Because we operate a lot of hog farms, we have a lot of manure,” William Gill, vice president of environmental affairs at Smithfield Foods, said at the 2017 Environmental Leader Conference and Energy Management Summit. “We’ve partnered with tech providers and utility experts, and we have a manure farm in Utah that actually creates electricity from manure.”
While there is the cost to build infrastructure for renewable natural gas, the concept has taken off. Projects are proliferating, driven by renewable energy requirements and corporate GHG reduction targets.
More about Duke energy, renewable natural gas, North carolina, hog farm, Methane gas
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