In fact, more utilities are thinking of buying the gas outright. Pacific Gas and Electric has agreed to transport gas from a big digester that Microgy, a digester manufacturer, is building in California. Right now Microgy plans to sell the gas on the open market, but Robert Howard, vice president for gas transmission and distribution, said P.G.& E. may buy some gas itself. “This technology provides pipeline-quality gas and reduces carbon emissions, so of course we’re in favor it,” he said.
The environmental boons are many. According to Agstar, digesters are already keeping 66,000 tons of methane from escaping each year into the atmosphere, while generating enough energy to power more than 20,000 homes.
And technologies, some of which have been around for decades, have finally grown more reliable. “There’s been a lot of time and energy spent on making these as effective and efficient as possible, so anaerobic digestion will be a growing business,” said Daniel J. Mannes, vice president of Avondale Partners, a securities research firm that recently initiated coverage of the Environmental Power Corporation, the company in Portsmouth, N.H., that owns Microgy.