Old French fry grease — long a fuel option for drivers of certain retrofitted cars — is now reducing the carbon footprint of a large wastewater treatment plant in Overland Park.
New treatment facilities that were added as part of the expansion of the Douglas L. Smith plant have been slowly digesting used grease and oil from area restaurants and converting the energy into electricity. The project, online since 2011, recently won an award from the National Environmental Health Association for innovation.
It works like this: Restaurants and institutions are required to pump out their waste grease so it doesn’t go into the storm sewers. When they bring the grease to the treatment plant, it goes into a large anaerobic digesting tank. Organisms there gradually break down the solids in the grease, giving off methane gas in the process. The methane is then burned in generators, creating electricity that goes back into powering the plant.
But that’s not all. As the generators are running, water circulates around them and collects heat, which is then used to keep the oils warm enough not to clog the pipes.
Powering the plant is no small feat. The Douglas L. Smith plant is a big facility in one of the county’s biggest electricity users. Johnson County wastewater officials figure the system has saved $250,000 a year by generating enough electricity to power half the plant, and Susan Pekarek, chief engineer, said it’s likely to save even more as the rest of the plant is expanded in coming years.
The plant, near Interstate 435 and Highway 69, was built in 1979. Five years ago, the county approved an upgrade that would increase its capacity from 12 million gallons a day to 14.5 million and also meet stricter rules about phosphorus and nitrogen effluent.
The digester system was added to handle the extra solids that would come in with the additional liquid capacity. The $18.3 million upgrade was designated a green project by the Kansas Department of Health and Environment and was one of the first “shovel ready” projects in the area authorized under the American Recovery and Reinvestment Act.
The use of anaerobic organisms to digest solids is not a new concept, Pekarek said. But it is a first for the Kansas City area.
In addition to innovation and sustainability, the National Environmental Health Association award cited commitment to environmental goals and the possibility of using the same concept in other ways.