Green is the new smell of shit. If plans concretize, San Antonio could become the first U.S city to draw methane gas from human waste on a commercial scale for conversion into clean-burning fuel. Methane gas which is the chief by-product of human excrement can be combusted to power fuel furnaces, power plants, and other gas-based generators. At hand will be about 140,000 tons of waste produced in a year by San Antonians. This is a potentially rich source of biosolids for deriving methane gas.

Steve Clouse, chief operating officer of the city's water system says,
"The private vendor will come onto the facility, construct some gas cleaning systems, remove the moisture, remove the carbon dioxide content, and then sell that gas on the open market."


Power generating plans would be the first ready consumers of the supply. The city sealed a deal where Massachusetts-based Ameresco Inc will convert the city's biosolids into natural gas.  Their projected target is about 1.5 million cubic feet of gas per day. Now with this landmark agreement, more than 90 percent of excreted waste, both human and organic flushed down the sewers of San Antonio will be recycled.

Waste finds its way into sewage processing plants where the filtration systems separate chunks of the sludge into three constituents - liquid is used for irrigation, many of the biosolids are made into compost, and now the methane gas will be recycled for power generation. This would not only allow the Texas city to recycle this greenhouse gas, but hopefully bring down it’s power dependency on non-renewable systems.

In this sense, it is not at all a novel concept but the uniqueness lies in San Antonio being the first in the U.S to adopt the use of generated methane gas for power production.

Methane is a potent greenhouse gas by itself and one of the chief components of natural gas. Though non toxic, it is highly inflammable and is combustible in nature. Vis-à-vis other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released. Of course, its use as compressed natural gas and as a fuel in vehicles is well documented.

Cities around the world will be watching the San Antonio experience for a possible solution to their energy needs. As Steve Clouse says - we might call our waste something else...but if it powers up our homes, we would gladly give it a more refined nomenclature.

Source: Reuters
Image: Flickr.com