BREAK THE BAKER'S WINDOW:

... And Sewage, Too (ROSE GEORGE, 4/28/10, NY Times)

When it comes to harnessing energy from wastewater treatment, it sounds as if we are spoiled for choice. Then you look at the numbers. Of the 16,000 wastewater treatment plants in the United States, about 1,000 process enough gallons (five million daily) to be able to generate cost-effective energy using anaerobic digestion. Yet only 544 use anaerobic digestion, and only 106 of those do anything more with the gas produced than to flare it.

If those 544 treatment plants generated energy from their sewage, the E.P.A. concluded in a 2007 report, they could provide 340 megawatts of electricity (enough to power 340,000 homes), and offset 2.3 million tons of carbon dioxide that would be produced through traditional electricity generation. In the effort to reduce greenhouse gases, the E.P.A. said, this would be equivalent to planting 640,000 acres of forest or taking some 430,000 cars off the road.

Gasification, like anaerobic digestion, is an age-old process. It used to supply gas lamps in some American towns, too, before piped gas became the norm. The process — a thermal conversion at high temperatures — could probably be done in a garbage can. But the utilities haven’t been eager to push the technology. The sewage treatment process — essentially, filter, settle, digest — hasn’t changed much since the early 1900s, because it works. And drying out sludge enough to make it burnable takes money and energy. Pilot projects may take several years to pay for themselves, which can clash with short-term budget cycles.

Other factors may force the industry’s hand.