Pig farms can create big, stinking messes. The animal feces releases greenhouse gases, can pollute rivers, streams and groundwater, and emits ammonia that can sicken pigs living within tightly enclosed spaces.
But Loyd Ray Farms in North Carolina—along with about 160 other pig, dairy and poultry farms across the country—is putting the waste to work by generating clean electricity through anaerobic digestion. For three years, Duke University and Duke Energy have been setting up the $1.2 million pilot system, being tested out by 9,000 hogs. Now Google is taking up some of the university’s operational costs as a way to offset its carbon emissions. (The company unveiled their carbon footprint for the first time last week.)
Jolanka Nickerman of Google’s Carbon Offsets Team writes on the Internet giant’s new green website:
There are lots of different flavors and styles of carbon offsets, so I review each project’s history, documentation and financials to be confident that the project we’re investing in results in greenhouse gas reductions that wouldn’t have happened without our investment. To be sure we’re buying what we think we’re buying, I also visit each site to get my hands dirty—to see the equipment and interview the staff. Finally, a third-party verifier makes sure the project is delivering the reductions claimed.
The reductions claimed equal 5,000 metric tons of carbon dioxide, though they are technically methane, a greenhouse gas 21 times as potent. In a closed circuit, wet manure travels from the pigpen to an anaerobic digester. Here bacteria break it down, producing biogas that is about 54 percent methane. A cover over the lagoon collects the methane, which then runs a micro-turbine. The waste continues on its way an aerobic nitrification basin. The next stop is the storage lagoon. The farm then flushes out the pig barns with the treated water and the process begins anew.
A boon for the farmers (besides electricity produced on site) is cleaner flush water. This makes for healthier (and heavier) pigs. But let’s not forget our veggies. If diluted enough, the water can irrigate food crops. Typically, farmers can spray lagoon water only on fields for hay or other grasses.
Some digester systems also capture waste heat to warm nearby buildings and heat water. In 2010, anaerobic digesters, according to the Environmental Protection Agency, cut methane emissions by 51,000 metric tons of methane (equivalent to 1.1 million tons of carbon dioxide) and prevented 264,000 tons of CO2 emission by using methane power instead of fossil fuels.
For its part, Duke Energy will receive 600 renewable energy credits each year to help meet North Carolina’s renewable energy standard. The state aims to cut carbon emissions by 12.5 percent by 2021.
There are more than 2,400 swine farms in North Carolina. If they all adopt similar projects as Loyd Ray Farms, Duke University estimates that 766,000 megawatt-hours could result. With the nation’s digesters collectively having generated 453,000 megawatt-hours last year, this would bring the state a blue ribbon for livestock power. While the goal is a fat one, their pigs wouldn’t have to fly for it to happen, just poop.
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Image: Flickr/sgs_1019, Wikipedia, Google Green Blog
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