Andrew Seelaus

For the Bass Connections Campus Digester Team, the trip was an opportunity to see first-hand what a functional waste-to-energy anaerobic digestion system looks like.


Master of Business Administration and Master of Environmental Management '17

Project Team

What do renewable energy credits smell like?

Mmm. The COP21 in Paris was deemed a success, the Renewable Energy Investment Tax Credit has been extended, and the scent of clean energy is in the air. At least for one Bass Connections team it smells like bacon… err scratch that, it’s pigs. It definitely smells like pigs. This past fall, the Bass Connections Campus Digester Team took a trip to Loyd Ray Farms to see how hogs are cranking out some of North Carolina’s most valuable renewable energy credits (RECs) and carbon offsets. Through collaboration with Duke University, Duke Energy, and Google, Loyd Ray Farms has installed North Carolina’s first industrial scale swine waste-to-energy facility that meets the innovative swine waste management permit requirements. The farm represents one of the ways that Duke University has endeavored to meet its carbon neutrality and sustainability goals as outlined in the Duke Climate Action Plan. For the Bass Connections Campus Digester Team, the trip was an opportunity to see first-hand what a functional waste-to-energy anaerobic digestion system looks like.

Why swine farms?

In North Carolina, hogs are big business. The state is the second largest producer of pigs in the U.S., and boasts two counties who are first and second in overall hog sales in the country. The latest U.S. Census of Agriculture indicates hog farming represents $1.46 billion in gross state product and employs more than 20,000 North Carolinians. It is also a high waste industry. Large pig farming operations can result in significant air and water pollution if not treated properly. Projects like the Loyd Ray Farms anaerobic digestion system aim to convert the industry’s wastes into valuable products, turning swine feces into biogas, electricity, carbon offsets, and RECs.

How does it work?

Driving down the long gravel road that approaches Loyd Ray Farms, the facility looks like any of the other half dozen swine farms that the Bass Connections team passed en route to the site. Long white barns, easily more than half a football field each, lay next to each other with tall, automated feed silos at the end of each building. The site is neat and tidy with little indication that each barn contains nearly 1,000 hogs. That is, of course, until one stands downwind to experience the bombarding olfactory sensation of thousands of pigs accompanied with a bit of high-pitched squealing. Thankfully, the anaerobic digestion dramatically cuts the potency of the farm’s smell.


Around the back of the barns is where the magic happens. An enormous, heavy-duty plastic membrane billows above an in-ground digester about the size of a football field. Each of the barns is piped to the digester and the pig droppings are flushed once a week from the barns into the digester. In the digester, microbes break down the organic matter and eventually give off methane-rich biogas. The rising gas is caught by the membrane and is piped to a conditioning skid located just behind the barns. There, the gas is dried and filtered before being fed into a microturbine that generates electricity. In the hot summer months, when biogas production is especially high, excess gas is burned in a flare. The digester effluent is treated in an aeration basin and the resulting clean water is recycled through the system, flushing the wastes from the barns. Excess liquids are stored in the lagoon that previously served as the only means of waste treatment for the farm. The farmer periodically irrigates his crops with the nutrient-rich lagoon liquid

With a nearly closed loop process, the Loyd Ray Farms system produces enough electricity to power the treatment system, half the barns housing the pigs, and sometimes even enough to be sold to the local utility. Additionally, North Carolina law creates a carve-out for swine waste RECs in order to incentivize similar waste-to-energy projects. Power companies are required to have a minimum number of swine waste RECs apart from RECs collected from other renewable energy sources, like solar projects. With so few swine waste projects, the value of a swine waste REC can be well over $100, while solar RECs can trade for just a few dollars.

Challenges to hog farm investment

Perhaps one of the most interesting aspects of the pig industry is that the majority of North Carolina farmers don’t actually own the pigs they are raising. In many cases, Carolina hog farmers act as a contractor for larger, multinational companies that own thousands of hogs. Farmers are paid a fee per animal to raise the pigs during a particular portion of their lives. Some farms breed pigs, others are tasked simply with feeding them until maturity. In either case, margins for hog farmers are very slim, and the multinational companies who own the animals capture the majority of profits. With such low margins, many farmers may not have the resources to invest in an anaerobic digestion system like the one at Loyd Ray Farms to limit air and water pollution effects. REC and carbon offsets initiatives provide a means to incentivize outside developers to partner with farmers on projects that will not only reduce the green house gas emissions from farms, but can also be a financial boon for the farmers themselves.

Application to Duke’s Campus Digester Feasibility Study

For the Bass Connections team, one of the most helpful parts of the trip to Loyd Ray Farms was gaining an understanding of the scale required for significant anaerobic digestion operations. A critical question in evaluating the feasibility of a digester is understanding the true volume of organic material required to feed a digester. If Duke’s organic campus waste is insufficient to steadily feed a digester, like the pigs at Loyd Ray Farms, then the project may not be feasible. Alternatively, if the campus continued to expand its separation of organic waste, a campus digester may provide an attractive alternative to the status quo. These are all questions the Bass Connections Campus Digester Team is looking forward to answering this semester.