October 19, 2021

From gas to green

Methane engine at Cortland Wastewater Treatment Plant saves, makes money

Travis Dunn/contributing photographer

Brian Suozzo of Cedarwood Engineering, right, and Bruce Adams, city superintendent of wastewater, talk about how the new methane engine at the Cortland Wastewater Treatment plant generates electricity to run the plant as well as 200 kilowatts of additional power sent to the electrical grid.

The roar inside the engine room is deafening, even if you’re wearing ear protection. It’s a low bass drone that drowns out almost everything except a piercing, high-pitched whine that feels like it’s inside your head.

These are the sounds of the newest piece of machinery at the Cortland Wastewater Treatment Plant – a methane engine that burns gas from the plant to generate electricity.

That electricity – 325 to 350 kilowatts per year – is now used to run the plant. That’s about $300,000 of electricity per year that the city will no longer has to buy, said Bruce Adams, city superintendent of wastewater. Instead, the engine will now export 150 to 175 kilowatts of power to the electrical grid annually. The engine could pay for itself in a few years, although the city has not yet been provided with a rate payment schedule for its exported electricity, Adams said.

The engine, as well as the overall system of methane capture and filtration, cost $2 million, all of which was covered by a grant from the New York State Energy Research and Development Authority, said Mack Cook, city director of administration and finance.

On Thursday, to no fanfare, the engine became fully operational.

In appearance, it doesn’t look much different than any other other internal combustion engine. And it isn’t, said Brian Suozzo, head engineer of Cedarwood Engineering of Oneonta, who designed the methane-generation system that includes the engine.

It looks impressive, housed in its own building and run by computers, but basically it’s just a straight eight-cylinder engine.

“It’s a big car engine that runs on methane,” Suozzo said.

Adams and Cook presented the idea of building a methane engine to city officials in 2012. But even after the engine became a reality in 2018, it sat idle for a year while officials negotiated state regulatory hurdles.

“It was a very protracted approval process,” Suozzo said.

Initially, the engine was supposed to make the plant energy independent. But according to Adams, National Grid said that if the city wanted to choose this option, the city would also have to buy 100 kilowatts annually from National Grid. City officials thought this defeated the purpose of a self-sufficient system, and instead opted for a bigger engine that puts out electricity to the grid, Adams said. Moreover, the engine also produces excess heat that can be used by the plant’s digesters – the devices that use bacteria to consume biological waste and give off methane as a byproduct – as well as for heating buildings.

The engine also has environmental benefits, he said. By reducing the amount of fossil-fuel-generated electricity the city has to buy, the engine reduces the plant’s carbon footprint by the equivalent of taking 660 cars off the road.
The methane engine is a final piece of a project that uses bacteria to generate methane from wastewater sludge and whey trucked to the plant from Byrne Dairy’s yogurt factories in Cortlandville and Syracuse, as well from Chobani’s yogurt facility in Chenango County.

“It’s been a long road, but it’s definitely been a success,” Suozzo said.

The plant is producing more methane than the engine can use, Adams said.

Suozzo said one of the design problems he faced was the size of the engine: If the city bought an engine that was too big, it would not run at peak efficiency because it wouldn’t have enough methane.

The current engine size, said Adams, was based on predictions of the quality of methane the plant would generate. But those numbers shot up unexpectedly, he said, when the digesters began generating much higher quality methane than anticipated.

The plant is now considering ways to make use of the excess methane, Adams said. A sludge-drying process that uses methane is one option being considered, he said. In the meantime, the excess methane is being burned off.