Since 2008, the city’s Columbia Boulevard Wastewater Treatment Plant has been collecting methane – a stinky greenhouse gas that also doubles as a relatively clean-burning hydrocarbon fuel – produced by bacteria as it decomposes solid waste in sewage. It currently captures about 77 percent of the methane generated there, and uses some to generate electricity, and sells the rest. The other 23 percent is essentially wasted, as it’s flared off, producing carbon dioxide.
But Portland now wants to use 100 percent of the methane produced at the treatment plant, turning it into renewable natural gas for use in vehicles. City Council approved a plan to build a CNG fueling station at the site, and convert or replace diesel vehicles. The plan could make a significant impact, too, as the