Pig Poop’s Starring Role in the Biofuel Movement
Farmers are turning a stinky problem into a solution. What’s next: making it more affordable and even cleaner.
When Tom Butler switched his North Carolina farm from tobacco to 8,000 hogs two decades ago, he was appalled at the amount of waste the hogs produced, quickly filling massive lagoons with more hog manure than he knew what to do with.
“We decided to look into any kind of innovation to see if we could lessen the impact on community,” he said.
It took more than ten years, but he found a way to reduce methane emissions and odor from the lagoons by turning all that pig poop into renewable natural gas that he sells back to his local electric cooperative. Now 77 years old, Butler is still pushing to make Butler Farms cleaner by working with the electric cooperative to use his farmland to help power a microgrid.
Hog farms have a massive impact on the environment and local communities. They contribute to climate change by releasing large amounts of methane a greenhouse gas more than 25 times more potent than carbon dioxide, into the atmosphere. They disproportionately impact low-income communities of color that have to live and breathe next to them. And, they create an expensive, smelly problem for farmers like Butler, who are often just trying to make a living. If done properly, turning livestock manure into biogas can help reduce those impacts.
“It will take investment by the major integrators,” said Maggie Monast, senior manager of agricultural sustainability for the Environmental Defense Fund’s North Carolina office. “But that’s happening, so I think we are about to see much more rapid and large scale implementation of biogas.”
Most hog farmers store the animals’ waste in large lagoons, which are basins filled with manure and water that are toxic and can contaminate groundwater and air. When it’s covered, some of these greenhouse gases and pollutants can be prevented from escaping, but many farmers spray the mixture as a fertilizer on their crops.
That’s where the idea for biogas comes in. Closed-off lagoons capture some of the methane emitted from the manure, and an anaerobic digester installed on the farm turns the rest into biogas using a chemical process where bacteria decompose it. The resulting methane is essentially scrubbed to pipeline quality renewable natural gas so it can be piped to a power plant. The leftover liquid and solid residue is often used for fertilizer.
“Getting started and understanding the system seems complicated, but it’s not,” Butler said. “Mother Nature does most of the work for you.”
However, it’s expensive. Full systems, with the digester, pipes, and other parts, cost hundreds of thousands of dollars, Monast said. With the help of federal and state grants, Butler installed the digester and system on his farm in about six months, and said it’s been about a 10-year payback plan. His system is 180 kilowatts and runs 40 to 60 percent of the time. About 6,000 tons of carbon dioxide and methane is burned as fuel and the leftover gas is burned into the atmosphere, Butler said, and he sells the power back to the grid and purchases it from the electric cooperative—not an ideal situation, but much more profitable than running his farm off the grid.
“It’s still an air quality issue but about 90 percent less than what were producing before,” Butler said. Back in 2011, the technology wasn’t advanced and regulations and best practices were unclear, so Butler said his system never worked as efficiently as it should. He is currently updating his system and wants to eventually have a 500-kilowatt generator that can break down food waste from the community along with animal waste.
To scale this technology, large agricultural companies have to invest in it. That’s starting to happen, Monast said. Smithfield Foods, the largest producer of pork in the world, has biogas projects in Missouri and Utah. The Optima KV project in North Carolina uses five digesters to transform hog waste from three local farms into renewable natural gas. Duke Energy announced earlier this year it is purchasing the gas, and the utility expects to get to 11,000 MW hours out of the project — enough to power about 1,000 homes a year.
That’s less than 1 percent of what the gas-fired plant is using, but it helps Duke meet North Carolina requirements to rely on hog waste for 0.2 percent of retail electric sales by 2023.
“It’s expensive still, probably multiple times more expensive than regular natural gas, but it’s a good environmental story,” said Randy Wheeless, a Duke Energy spokesman. “I hope the technology gets cheaper over time.”
To scale up, renewable natural gas would have to compete with natural gas, which is cheap and in excess because of the pipeline boom in places like Appalachia and Texas. Since that’s likely a long way off, Monast said farmers can sell gas back to the grid or sell it for other industrial applications to grow jobs in rural economies. Eventually, she added, it could be used for transportation fuel.
Growing this technology also has to be done with local communities in mind, said Jamie Cole, environmental justice, air, and materials Policy Manager for the North Carolina Conservation Network. Communities have been trying for decades to get agriculture companies and hog farmers to clean up their operations. Cole said that these new biogas systems don’t always meet the environmental standards for new technologies as outlined by the state to improve hog farm operations, and communities have little or no say in the changes being made that could affect them.
“No one has a problem with biogas in itself, but it’s being touted as solution that is not really solution dealing with historical trauma of people living near these properties,” Cole said. “Until there’s serious investment in technology to clean up the operations, it’s going to be really hard for communities to accept a technology that falls short of real clean-up and doesn’t give anything back.”
She added that in addition to the digesters, communities want developers to look at other technology to reduce odors and the need for field spraying.
That benefits neighbors as well as farmers. “I’m not an activist, I’m an advocate for better waste management,” Butler said. “I love what I do, I love hog farming. I just think [the industry] can do better and owes that to neighbors and to the state.”