ShareThisIt's foul and untouchable, but also packed with energy and endless in supply.
Human waste may well become North Carolina's leading animal source of green fuel for generating electricity.
A wastewater-treatment plant in Cabarrus County, N.C., expects to start burning processed human excrement as early as next year to generate its own electricity. Raleigh and Durham have waste-to-energy projects in various stages of planning, and others are expected to follow as the state continues adopting clean energy alternatives.
It's estimated that today fewer than two dozen wastewater treatment plants around the country convert human waste to electricity.
The N.C. Utilities Commission opened the door to adding North Carolina to the list by tapping the energy-rich human byproduct the commission declared was every bit as green as solar, wind and hydroelectric power. The ruling in February gives electric utilities the go-ahead to pay a premium price for this resource, which utilities can count toward meeting their state mandates for renewable energy.
"All responsible water utilities are contemplating this as part of their future planning," said Robert Rubin, a retired N.C. State University professor of biological and agricultural engineering. "We are looking at these societal byproducts as a resource."
For the past few years, talk of animal waste in North Carolina was focused on the vast potential of using pig dung and poultry droppings as a green fuel. But the cost of processing and transporting animal waste from scores of farms, along with pollution concerns associated with incinerating the stuff, has delayed or stalled projects.
Advocates say power generation at wastewater-treatment plants builds on accepted and safe methods of elimination: burning the waste or decomposing it with bacteria. The energy content of the man-made fuel is comparable to that of wood, Rubin said.
Even so, converting human waste into fuel could draw unwanted attention to the raw material involved, and run afoul of cultural taboos in some communities.
"Most people out there will tell you, you don't play with poop," said Rubin, who has studied human "biosolids" for about 35 years. "Waste treatment is a very emotional issue."
The Water and Sewer Authority of Cabarrus County, about 150 miles west of Raleigh, has been incinerating human waste for years. Officials recently concluded it made economic sense to capture the heat exhaust to power a small turbine and run a generator.
Their mini power plant, expected to be operating by late 2011 or early 2012, will generate 1.5 megawatts of power, about three-fourths of the authority's electricity needs. Retrofitting the incineration system will cost about $10 million and will produce $2 million a year in electricity, Cabarrus County officials estimate.
The source of fuel: roughly 300,000 North Carolina residents. Half of these fuel producers are served by the Cabarrus County Water and Sewer Authority; the rest of the fuel will come from neighboring wastewater-treatment plants that pay Cabarrus County to dispose of their waste.
"The sludge is being transported right now to either be land-applied (as fertilizer), which does smell (bad), by the way, or to some sort of landfill," said Jennifer Bell, a Raleigh engineering consultant for Cabarrus County. "Human waste has been a liability for decades and decades."
In North Carolina, only four wastewater-treatment agencies use incineration to eliminate human waste -- in Greensboro, High Point, Asheville and Concord. It's not clear whether any more waste incinerators will be built in this country. Aside from the controversy inherent in incinerating feces, this month the U.S. Environmental Protection Agency proposed much stricter pollution controls for the nation's 218 wastewater-sludge incinerators.
Most wastewater treatment plants in the country break down human waste using bacteria. One of the bacterial processes, anaerobic digestion, creates a valuable byproduct: methane, a gas that can be used to run electric generators.
The city of Raleigh Public Utilities Department is further along in the process and is planning to add anaerobic digestion equipment to create methane for power generating electricity. The power plant at the Neuse River Wastewater Treatment Plant, southeast of Raleigh, wouldn't be operating until 2017 at the earliest and would require final approval from the city council.
The planned generator and anaerobic digesters would cost as much as $30 million and offset one-third of the department's electricity needs. Payback could take anywhere from 10 to 30 years, said T.J. Lynch, the department's wastewater-treatment superintendent.
"At that point we'd change from being energy consumers to being energy producers," Lynch said. "It's a much more sustainable way to treat biosolids."
(E-mail reporter John Murawski at john.murawski(at)newsobserver.com.)
(Distributed by Scripps Howard News Service, www.scrippsnews.com.)
Must credit The News and Observer of Raleigh, N.C.
