Construction is more than halfway finished on the City of Boulder’s biogas use enhancement project, located at the city’s water resource recovery facility (WRRF).

Biogas produced from wastewater digesters will be converted into renewable natural gas (RNG) for vehicle fuel, delivered to community partners for use after injection into the Public Service Company of Colorado (PSCo) pipeline. Construction began in January and is scheduled for completion later this summer.

The city has contracted with Tetra Tech and CGRS Inc. to design and build the biogas-to-renewable-natural-gas (RNG)-conditioning system, which will replace the WRRF’s cogeneration system, which is at the end of its useful service life. The project is one of only a handful of similar projects in Colorado.

Pasadena, California-based Tetra Tech is providing engineering, procurement and construction (EPC) services to the City of Boulder. Fort Collins, Colorado-based CGRS is serving as general contractor and design-build partner, overseeing and performing the majority of on-site construction work.

Western Disposal has agreed to purchase the RNG to fuel a portion of its vehicle fleet, approximately 31 trucks. The project will also enable the city to take advantage of revenues available to renewable fuel producers under the U.S. EPA’s Renewable Fuel Standard, which will drive a projected return on investment in the next 10 to 15 years.

“The biogas use enhancement project is the next logical step toward making the WRRF more environmentally sustainable as well as economically viable,” says Chris Douville, wastewater treatment manager for the City of Boulder. “We’re pleased to realize the positive impact on the community’s climate goals through production and use of RNG as vehicle fuel, as well as the city’s financial ability to support other renewable energy and sustainability projects in the future through sale of RNG.”

The work includes installing a BioCNG gas conditioning system; demolishing the existing cogeneration engines and heat recovery systems; installing one new boiler; and upgrading the hydronic system used to heat the digesters and other buildings.

“CGRS is excited to lend our design-build expertise in renewable natural gas facilities to Tetra Tech and the City of Boulder on this innovative project,” says CGRS project manager Greg Steed, PE. “Not only will this project reduce another Front Range community’s environmental footprint, it will also enhance services to Boulder residents, and we are honored to be a part of it.”