May 18, 2020. The City of Longmont, Colorado, has completed a project begun in 2018 that converted the wastewater treatment plant into a renewable natural gas (RNG) plant. The captured gas is then compressed in order to prepare it to power 11 trash trucks, according to information provided by the city. The facility can produce natural gas that is equivalent to 400 to 500 gallons of diesel fuel daily.

“Eventually, we want to replace all 21 waste trucks with RNG,” said Cara Wilwerding, public relations specialist with the city. She said the city hopes to make that happen by 2024 as existing diesel trucks are due for replacement.

The project is the first along the Front Range.

The 11 RNG trucks offset use of about 100,000 gallons of diesel fuel annually, reducing greenhouse gas emissions by about 1,000 metric tons of carbon dioxide per year. Prior to the plant’s installation, Longmont would capture the natural gas but flare it, according to Cory Kahler, field operations manager for the contractor, CGRS Inc.

Wilwerding said the cost for the design, construction and equipment for the biogas conversion part of the project was $5.2 million, with the Colorado Department of Local Affairs providing a $1 million grant to offset some of the cost.

Cost to construct a waste services building in connection with the project was an additional $3.1 million.

Trash trucks capable of operating on compressed renewable natural gas cost about $350,000, a $45,000 premium over the $305,000 cost of diesel trash trucks. The Regional Air Quality Council paid 80% of the differential between the two types of trucks, Wilwerding said.

Trash trucks are housed in a new, 22,680-square foot waste services building on Martin Street in Longmont, near the wastewater treatment plant. Truck drivers connect their vehicles at the end of their shifts to one of 16 fueling posts in order to have the trucks ready to go in the morning.