Using Pig Poop to Create Energy

By Celeste Beley

Pig farms have a smelly reputation. From the ammonia and methane to the pathogens they produce, they’ve never been known as a pleasant place, but one farm in North Carolina is changing that. North Carolina law now mandates that some of its renewable energy be derived from chicken or swine waste, and The Loyd Ray Farm is the first to turn pig waste into energy. Partnering with Duke University, Duke Energy and Google (who provided initial investments as part of their corporate commitment to reduce their carbon footprint to zero), they converted a standard hog farm into a sustainable farm using a system designed by Cavanaugh Solutions.

The farm flushes 80,000 gallons of manure daily into a biodegester — basically a 174- by-218 plastic domed pit. Anaerobic bacteria convert the organic waste into methane, carbon dioxide and other chemical byproducts. The biodigester mixes liquid to keep the bacteria digesting at maximum efficiency, and also reduces pathogens without using synthetic chemicals. The gas that is harnessed generates enough electricity to run the entire waste treatment system plus lights and machinery for five of nine hog barns. Excess gas is burned to convert methane into carbon dioxide. Leftover liquid waste is then aerated, creating nitrate from the ammonia, and is used for flushing out the barns or as irrigation in the fields. As a bonus, the plants absorb the mixture faster since plants absorb nitrates more easily than ammonia. This results in less fume and odor emissions from the farm, something the Loyd Ray Farm neighbors were happy about and quick to note!