No matter how you spin it, the business of raw sewage isn’t sexy. But in Colorado, the city of Grand Junction is making huge strides to reinvent their wastewater industry – and the result is like finding a diamond in the sludge.

 

The Persigo Wastewater Treatment Plant is processing 8m gallons of Grand Junction’s human waste into renewable natural gas (RNG), also known as biomethane. The RNG is then used to fuel about 40 fleet vehicles, including garbage trucks, street sweepers, dump trucks and transit buses.

 

It’s possible through a process called anaerobic digestion, which breaks down organic matter into something called raw biogas. The biogas is then collected and upgraded to RNG – at pipeline quality – and can be used as electricity, heat or transportation fuel.

 

Turning wastewater into biogas is not new in the US. For decades, biogas has been used for heating or to power generators and micro-turbines to produce electricity.

 

“But as far as we know, we are the only municipal wastewater facility in the nation producing biogas used as vehicle fuel,” said Dan Tonello, wastewater services manager for Grand Junction.

 

Tonello said their old method involved simply flaring off the raw gas into the atmosphere.

 

“Now, instead of letting it go to the flare, it goes to conditioning equipment that scrubs and cleans the gas and puts it into a pipeline,” Tonello said.

 

The environmental benefits are abundant for Grand Junction. According to Bret Guillory, utility engineer for the city, “we may be reducing greenhouse gases by as much as 60% to 80% … This is compared to the old process of flaring off the raw gas at the plant, and burning diesel and gasoline in some of our larger fleet equipment.”

 

Developed over 10 years, the project is worth $2.8m. The cost to produce and compress the RNG is around 80 cents per GGE, while it’s sold to the fleet department for $1.50 per GGE.

 

“The project will pay for itself in around seven years,” Guillory said. “Not a bad return on the investment.”

 

The underground pipeline is nearly six miles long and carries the RNG (in compressed form, not liquid) from the wastewater plant to the city’s fueling station. Fleet vehicles fill their tanks with RNG during the night – and by morning they’re ready to go.

 

Grand Junction had installed a compressed natural gas fueling station in 2011. So the infrastructure was already there, they just switched the natural gas to RNG.

 

Approximately 460 gasoline gallon equivalents (GGEs) are produced on-site daily. (The Guardian)

 

 

PHOTO: Vehicles wait to refuel at the Persigo Wastewater Treatment Plant in Colorado.

CREDIT: City of Grand Junction.