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Tons of Manure Converted to Electricity and Fertiliser

by 5m Editor
30 December 2011, at 8:21am

NORTH CAROLINA, US - Duke University has helped a North Carolina pig farm turn tons of manure into electricity and fertiliser in what it says is one of the the cleanest waste-to-energy systems.

Loyd Bryant used to pump manure from his 8,640 hogs into a lagoon, where it raised an unholy stink and released methane and ammonia into the air. The tons of manure excreted daily could not be used as fertilizer because of high nitrogen content.

According to Los Angeles Times, the solution to Mr Bryant's hog waste problem was right under his nose – in the manure itself.

A new waste-processing system – essentially a small power plant – installed on his 154-acre farm uses bacteria to digest the waste and burns methane to produce electricity. It also converts toxic ammonia into forms of nitrogen that can be used as fertiliser for more profitable crops.

Waste-to-energy systems have been around for at least 15 years. But Duke University, which helped develop and pay for Mr Bryant's system, says this one is the cleanest in existence – and virtually the only one that tackles all of the environmental problems created by animal waste.

The system was built with off-the-shelf parts and simple design plans that are free for the asking. It is poised to become the standard for a cleaner waste-to-energy model that brings together farmers, utilities and private companies in an environmentally friendly effort.

"It does it in a way that is not overly complicated and stands to yield many more benefits beyond energy production and environmental protection," said Tatjana Vujic, director of Duke University's Carbon Offsets Initiative.

The $1.2-million project is funded by the university, Duke Energy and Google, which operates a data center in nearby Lenoir, North Carolina. All three, along with Mr Bryant, will benefit.

Mr Bryant saves money on electricity and gets a cleaner farm. Improved air quality in his hog barns also means his pigs will have lower mortality rates and convert feed more efficiently, fattening Mr Bryant's profits.

Duke University and Google earn carbon offset credits from the system. And Duke Energy gets renewable energy credits in a state where a new law requires utilities to produce a small percentage of electricity from renewable resources beginning next year. North Carolina is the only state that will require a portion of that "set-aside" to include electricity produced from hog waste.

Mr Bryant, whose family has farmed the rolling Piedmont of central North Carolina for four generations, says the 65-kilowatt turbine generates enough electricity to power the system — and five of Mr Bryant's nine hog barns, where giant fans hum day and night. The digester captures methane equivalent to 5,000 metric tons of carbon dioxide per year and produces enough electricity to power 35 homes a year.

"It's cut my electric bill in half, and it's going to make it so I can grow corn and wheat and beans," said Mr Bryant, 71.