San Antonio Generating Gas from Sewage
Published on September 11th, 2008
San Antonio, Texas is making use of its 140,000 tons of sewage generated each year to capture methane gas. The city’s utility board of trustees approved a contract this week to sell 900,000 cubic feet of natural gas derived from the sewage each day to Ameresco, a Massachusetts energy services company.
Though methane is a potent greenhouse gas, it has a variety of uses. The substance can be used for fuel in gas turbines or steam boilers, and it is also used as vehicle fuel in the form of compressed natural gas. Additionally, NASA is researching methane as a potential rocket fuel.
According to Steve Claus, the chief operating officer of the water system, San Antonio’s sewage generates 1.5 million cubic feet of gas each day—enough to fill seven commercial blimps or 1,250 tanker trucks. The facilities needed for the project will be ready in about two years.
San Antonio will get $250,000 a year for the methane—a sum that I hope will go towards more renewable energy efforts in the area.
San Antonio residents produce about 140,000 tons a year of a substance gently referred to as “biosolids,” which can be reprocessed into natural gas, said Steve Clouse, chief operating officer of the city’s water system.
“You may call it something else,” Clouse said, but for area utilities, the main byproduct of human waste – methane gas – will soon be converted into natural gas to burn in their power plants.
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,” Clouse said.
The gas will be sold to power generators, he said.
Some communities are using methane gas harvested from solid waste to power smaller facilities like sewage treatment plants, but San Antonio is the first to see large-scale conversion of methane gas from sewage into fuel for power generation, he said.
Following the agreement, more than 90 percent of materials flushed down the toilets and sinks of San Antonio will be recycled, he said. Liquid is now used for irrigation, many of the solids are made into compost, and now the methane gas will be recycled for power generation.
(Reporting by Jim Forsyth, Editing by Chris Baltimore and Lisa Shumaker)
The utility already sells for reuse a portion of the water that’s cleaned up at its wastewater treatment plants. It also has contracts to turn up to 80 percent of biosolids into compost that’s sold for use in yards and gardens.
“As far as we know, SAWS is the only city in the United States that has completed the renewable recyclable trifecta,” Clouse”.
Clouse said it will take 18 to 24 months for construction of facilities needed for the contract.
Not so delicate post
For this the third entry in the annals of excellent excrement (after cow and E. coli poop), we will have to travel deep down into the heart of Texas…and then even farther down into the sewers of San Antonio. So don your rubber body suit, gas mask, and sense of humor, for sewage is no longer just stuff to be dumped and forgotten.
No, San Antonio is out to prove that sewage, and specifically the methane that it gives off oh so (i.e., too) naturally without any bother or cost to us, can be used as a source of alternative fuel…I mean it is natural gas, after all.