13 January 2011

If you thought that manure was just for spreading on fields or in the garden, or just to provide an interesting smell during a drive through the country, it’s time to learn a thing or two. For years progressive farmers have been harnessing a byproduct of their animals’ manure, methane, and turning it into electricity. Some farms with several hundred cows have even been known to power small communities. But what about our, ahem, byproducts, our own human manure? It is little different from that of a cow’s, save for perhaps a little less hay, and will produce methane in the right conditions, ripe for harvesting to be burned and used to generate power through natural gas plants. Several small projects already exist in the US, but the city of San Antonio, Texas, is the first to take on a project of commercial scale to do just that.

The process is quite simple, and we’re surprised that existing sewage treatment plants have not already adopted the practice as it would not only save them money, but also create an additional revenue stream, but it has now begun, and the city is planning on using the 140,000 tons of human waste to produce fuel to send to the open market. They estimate that this amount of waste will yield a massive 1.5 million cubic feet of natural gas (processed methane) daily. That’s a lot of gas, and one that will be an arguably close to carbon neutral, when burned in a natural gas power plant. Either way the combustion of the methane is a great thing for the environment. Instead of just letting the gas escape as it might do if unharnessed, it wil be used to provide electricity, offsetting the fossil-based natural gas that would otherwise take its place. Also, since methane is a much more dangerous emission than CO2 when it comes to retaining heat in the atmosphere, there’s another plus for cooling down the planet.

The city also expects to recycle about 90% of the material that goes down the drain in its bathrooms, the liquids being used for irrigation and solids into compost.

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