New study highlights advantages of renewable natural gas projects on NC hog farms
RALEIGH (JUNE 3, 2024) — With a growing number of hog farms across eastern North Carolina interested in generating renewable natural gas on their farms, a new study from a University of Tennessee professor illustrates the significant benefits these projects deliver. Benefits include a significant decrease in greenhouse gas emissions, reduced odors on farms, and less potential for flooding during hurricanes or heavy rain events.
The study from Dr. Robert T. Burns, a distinguished professor in biosystems engineering and soil science, considered the specific conditions present on North Carolina hog farms and concluded that renewable natural gas projects produce a 90% decrease in methane emissions and a 51 percent decrease in odor unit emissions.
The vast majority of renewable gas projects in North Carolina involve the use of a covered digester that enables farmers to capture methane emissions and convert them into clean, renewable energy.
“Adding an impermeable cover to manure storage is firmly accepted as a preeminent method to reduce ammonia, hydrogen sulfide, and odor from that manure storage,” Dr. Burns states in the 2023 study, Swine Manure Anaerobic Digestion Impact on Carbon & Macronutrient Fate Including Changes in Air & Odor Emissions.
His study found a 67% decrease in on-farm hydrogen sulfide emissions and an 8% decrease in nitrogen, an 11% decrease in phosphorous, and a 0.5% decrease in potassium in the storage lagoon due to settling in the digester. Ammonia levels increased by less than 1% due to leakage from the digester cover.
The largest renewable natural gas project in North Carolina is Optima KV, which came online in 2018. It uses covered digesters to collect methane from five hog farms in Duplin County. Together, those farms generate 11,100 megawatt-hours of electricity, enough energy to power about 880 homes a year. Align RNG, a joint venture between Dominion Energy and Smithfield Foods, is currently developing projects in Sampson and Duplin counties that will involve more than 50 farms and generate enough energy to power 7,200 homes.
RNG BENEFITS LOCAL COMMUNITIES AND ENVIRONMENT
Renewable natural gas projects represent a substantial financial commitment from the pork industry to continue making improvements that better protect the environment and benefit the surrounding community. These benefits include:
Reducing Emissions: Capturing methane is a positive development that reduces greenhouse gas emissions. The NC Clean Energy plan states: “RNG can play an important role in reducing methane emissions, a potent GHG with global warming potential 25 times greater than carbon dioxide. Reducing methane emissions can have a larger impact on the environment than other carbon reduction initiatives....” The Burns study concludes that methane emissions are reduced by 90%.
Minimizing Odors: While some argue that biogas projects don’t effectively address odors on farms, the EPA highlights “odor reduction” as one of the primary benefits of biogas systems on hog farms. On North Carolina farms that have installed lagoon covers, it’s estimated that they block 85% of odor from the lagoons.
Preventing Flooding: Record-breaking hurricanes, including Hurricane Matthew (2016) and Florence (2018), dumped massive amounts of rain in eastern North Carolina and raised concerns about the potential for flooding on hog farms. While hundreds of lagoons located in flood-prone areas have been closed over the past 20 years, covered digesters provide additional protections. The covers keep rainwater out, helping maintain low lagoon levels and minimizing potential for flooding on farms.
Income Opportunities For Family Farmers: The growth of the biogas industry is making technology more affordable. When farmers invest in the infrastructure needed to generate renewable natural gas on their farms, they can share in the steady, long-term revenue RNG projects can produce.
North Carolina is a national leader in biogas production. The NC Clean Energy Plan highlights the state’s potential to increase biogas production, specifically noting the potential of capturing methane gases on hog farms.
The EPA’s AgSTAR program touts the benefits of digester systems on farms, highlighting that digester systems reduce odors. The EPA reports that in 2022, anaerobic digesters generated more than 2.4 million megawatt-hours of electricity and reduced greenhouse gas emissions by more than 10.4 million metric tons of CO2 equivalent (MMTCO2E). MMTCO2E is a measurement used to compare emissions from various greenhouse gases based on global-warming potential.
Generating renewable natural gas on pig farms is a win-win for North Carolina farmers and their neighbors, the environment, and the State of North Carolina. Embracing renewable natural gas projects allows North Carolina pig farmers to continue doing what they do best — making continuous improvements on their farms and in their communities.
About the North Carolina Pork Council
The NC Pork Council is the voice of North Carolina’s pork industry, advocating for the family farmers and industry partners who work hard every day to produce quality pork the right way — safely, responsibly, and sustainably. North Carolina is one of the top pork-producing states in the country, ranking third nationwide and contributing $10.8 billion to our state’s economy each year. Whether through advocacy, education, or community outreach, the NC Pork Council works to support responsible, smart farming practices and to ensure the continued success of the industry. Learn more at www.ncpork.org.