Finally: Recycling NYC Sewage for Energy
by Mireya Navarro, NEW YORK TIMES, February 8, 2011
New York City’s sewage presents a daunting and costly challenge: it creates foul odors and often contaminates waterways.
But the city is now casting its sewage treatment plants and the vast amounts of sludge, methane gas and other byproducts of the wastewater produced by New Yorkers, as an asset — specifically, as potential sources of renewable energy.
For the city’s Department of Environmental Protection, which is to issue its strategy on Wednesday, it is a shift. Until now, the agency has mainly played the role of water utility and environmental steward rather than energy producer.
But like other cities around the country looking to reduce both the costs of sewage treatment and disposal and the heat-trapping greenhouse gases emitted in the process, New York is beginning to look at its waste as an untapped resource.
Heating fuel can be extracted from sludge and butanol, an alternative fuel to gasoline, from the algae generated by wastewater. Sewage treatment plants could sell methane gas to provide power to homes. Such projects represent a more sustainable long-term approach to managing a wastewater treatment process that costs the city about $400 million annually, not including capital investments.
“There’s nothing in here that’s pie in the sky,” Caswell F. Holloway, the city’s commissioner of environmental protection, said of the plan. “While we’re early in the process, it’s real.”
New Yorkers currently produce some 1.3 billion gallons of wastewater daily. The agency is seeking vendors to find uses for the resulting daily yield of 1,200 tons of sludge, a residual that is currently sent to landfills in Suffolk County, N.Y., and Virginia.
City officials, who hope to have a contract by 2013, said the solid could be harvested for gases that produce clean energy and could be used in more traditional ways, too, as fertilizer or as paving and building materials.
The biggest potential source of energy, officials said, is the methane gas from sewage treatment plants’ digesters. About half of the methane produced by the city’s plants is already used to meet about 20 percent of the energy demands of the city’s 14 sewage plants, whose electric bills run to a total of about $50 million a year. Now the city wants to market the other half, which is burned off and wasted. [Read rest of story]