reasons to be cheerful
“It’s extremely energy consumptive to treat wastewater,” says Dave Moldal, program manager at Energy Trust of Oregon. As the region grows in population, the more energy the wastewater plant requires. But what if increasing volumes of wastewater could provide the treatment plant with more energy rather than consume it? That’s exactly what’s been happening at Clackamas County’s Tri-City Water Resource Recovery Facility for the past seven months.
Since August 2021, the plant has been pumping out renewable power produced from methane, a natural byproduct of human waste decomposing in an oxygen-free environment. Now, this loop of green energy represents a powerful example of how waste can become something we benefit from rather than expend resources disposing of. By turning human waste into power, wastewater treatment facilities have the potential to become energy generators instead of consumers, while creating clean water that’s returned to the local ecosystem.
While clean water goes in one direction to disinfection, and ultimately, the river, the remaining biomass goes in another, to one of three anaerobic digesters, the newest of which is a 1.3 million-gallon tank that operates like a hulking metal stomach. Inside, naturally occurring microorganisms further break down organic matter in an oxygen-free environment that allows for the concentrated production of methane. The methane rises to the top of the digester and is transferred to a new 600 kW lean-burn co-generation engine, which converts it into heat and electricity. The co-generation engine creates heat for five of the buildings on site and an estimated 4,324 megawatts of electricity, providing about half of the facility’s energy usage.