The city’s sewage treatment plant takes what people send down their drains and toilets and turns it into water clean enough to put in the Neuse River and something euphemistically called biosolids, which is used as fertilizer.
In a few years, the treatment process will also create a third product: compressed natural gas, enough to run up to 50 GoRaleigh buses a day.
City and state officials held a ceremony Wednesday to begin a $148 million upgrade to the Neuse River Resource Recovery Facility, which treats sewage from Raleigh and several other Wake towns served by the city’s utilities department. The part of the plant that treats solids and gets them ready to use as fertilizer is about 25 years old and needs to be replaced.
The city decided to go with a relatively new technology called thermal hydrolysis, which heats the solids under pressure, like a pressure cooker. Combined with traditional anaerobic digestion, the process will produce about half the biosolids as the current system, plus methane gas that can be cleaned and used as fuel.
“Our real goal here is to reduce the volume of biosolids,” said Ed Buchan, environmental coordinator with the city utilities department.
The city’s treatment plant, off Battle Bridge Road about 10 miles southeast of downtown, handles about 75 million gallons of sewage a day, producing more than 21,000 tons of biosolids a year, said Nathan Howell, the plant’s operations supervisor. The city spreads some of that on pastures and fields around the plant, but most of it is handled by contractors the city pays to deliver biosolids to farmers across the state, Howell said.
Most of the attention at Wednesday’s ceremony was on the natural gas the plant will produce to run GoRaleigh buses, two of which were parked outside. Robert Massengill, the city’s public utilities director, said the power the plant makes at peak production will reduce greenhouse gas emissions equivalent to taking 4,000 cars off the road each day.
“To us, this really is an exciting project,” Massengill said.
Mayor Nancy McFarlane said the idea of producing and harnessing natural gas from the wastewater plant seemed like a long shot, a “dream project,” when it was first talked about in 2012, but that it became a priority for the city’s utilities, transportation and sustainability departments. McFarlane noted that the City Council has set a communitywide goal of reducing greenhouse gas emissions 80% by 2050.
“This project .... puts some muscle behind city and state goals to reduce greenhouse gas emissions,” she said.
The environmental benefits of the project helped the city qualify for a $50 million no-interest loan from the state’s Clean Water State Revolving Fund. Secretary of Environmental Quality Michael Regan attended Wednesday’s ceremony and praised the city’s commitment to energy efficiency. When the upgrades are finished in 2022, Raleigh’s will be one of only a handful of sewage treatments plants in the country that uses thermal hydrolysis.
“This is a game changer,” Regan said. “We’ll be sharing this story with the rest of North Carolina as we continue to think about how we reduce our greenhouse gas footprint.”
Forty of GoRaleigh’s 100 buses now run on compressed natural gas, and the agency expects that number to increase to 75 as buses are replaced in the coming years, said transit administrator David Eatman.
At one point, Eatman said, the city contemplated trucking the gas from the treatment plant to GoRaleigh’s garage off Poole Road. But Dominion Energy North Carolina plans a pipeline near the plant that will take in the gas, giving the city credit against what it uses for buses at Poole Road.
The city’s main sewage treatment plant opened in 1974, with a capacity of 40 million gallons per day; it replaced a plant on Sunnybrook Road, where the Walnut Creek Athletic Complex is now. Buchan said the city gets about 11,000 new wastewater customers each year and expects to treat about 100 million gallons per day at the Neuse River plant by 2040.