Larry Cahoon's Research Extracts Value from Waste

Larry Cahoon in his lab studying hog wasteLarry Cahoon, a marine biologist at UNCW, specializes in aquatic ecology. Two decades ago, he and colleagues began to notice unprecedented algae blooms along the North Carolina coast. The source of these bacterial blooms initially was a mystery, but soon Cahoon realized the changes in water quality coincided with an emergent local hog industry.

As swine production increased in North Carolina, so had swine waste. Farmers typically flush this refuse into waste lagoons, which are manmade, open-air ponds lined with clay to prevent contents from seeping into the surrounding soil. Lagoons can be as large as several acres and do not protect against even simple environmental factors, like rain. These days, waste production at a swine farm can equal that of a human town.

Cahoon became curious about finding solutions to the causes of the water impurity. But alternative uses for swine waste have been extremely limited. Possible disease transmission prevents farmers from using it to fertilize crops for human consumption and, even for unconsumed crops like cotton, swine waste does not contribute nutrients to soil. The hog industry has long searched for more effective methods to dispose of it. But Cahoon imagined a different scenario. What if, rather than eliminating swine waste, a serious use could be found for it?

In collaboration with colleagues at UNCW's biology and chemistry departments, researchers at Duke University and at the Animal and Poultry Waste Management Center at North Carolina State, Cahoon realized that waste lagoons were essentially bacterial cultures that had yet to be examined for the metabolic processes occurring within.

"The key to this," he recalls thinking, "is to find something valuable." With so many lagoons in the state-today there are at least 2,300-Cahoon knew that if he could find something of even modest value, the implications of his discovery would be considerable.

It turns out Cahoon was right. Much interesting science happens in waste lagoons. Some of the bacteria in swine waste are capable of photosynthesis, some can metabolize sulfur compounds and others can turn nitrogen in the atmosphere into amino acids. These metabolic processes yield a number of interesting compounds, including a particular antioxidant called spirilloxanthin. Antioxidants have a number of uses, especially in pharmaceuticals, health supplements and cosmetics. These compounds can also be used to enrich feed for other animals or as a preservative in biodiesel.

Early tests of spirilloxanthin suggest it is as effective an antioxidant as many currently on the market. Cahoon mentions there is "a whole array of potential uses" for it. He also believes additional compounds might still be found. "We would very much like to explore others," he says.

Larry Cahoon sampling hog waste from a waste lagoonBut even if no additional compound is discovered, spirilloxanthin alone has the potential to change the way people think about swine waste. It also has the potential to change the way that waste is handled. "Now you've got an economic rationale for managing the lagoons," Cahoon explains, and a meaningful disincentive against runoff or pollution.

"The potential here," Cahoon predicts, "is for everybody to win."

Cahoon plans to continue his research at UNCW, and to investigate more compounds that are likely present in the lagoons. His initial results have been published in Agricultural Sciences, and soon he hopes entrepreneurs and industry representatives will join in his work as they recognize its advantages.

By Benjamin Rachlin '15M