South Platte Renew Gas Recovery Facility and Pipeline Injection Project

Owned and operated by the Cities of Littleton and Englewood, South Platte Renew (SPR) is the third largest publicly owned treatment works in the State of Colorado.

In 2016, SPR contracted Carollo Engineers to evaluate sustainable and cost-effective options to beneficially reuse their Water Resource Recovery Facility’s (WRRF) energy-laden biogas, a key focus area of their 2014 Energy Improvement Program. After evaluating a variety of alternatives, Carollo Engineers recommended that SPR install a new biogas-upgrading system that treats their plant’s biogas into high-quality renewable natural gas (RNG), which is then injected directly into a nearby natural gas pipeline owned and operated by the Public Service Company of Colorado, a subsidiary of Xcel Energy.

In spring 2018, Carollo Engineers began preparing the design and procurement services for SPR’s Pipeline Injection Project. The design includes a two-pass membrane biogas-upgrading system that removes hydrogen sulfide, moisture, siloxanes, and carbon dioxide from the WRRF’s biogas to meet Xcel Energy’s RNG quality requirements. The cleaned RNG is compressed prior to injection into Xcel’s natural gas pipeline while the tail gas from the biogas-upgrading system is combusted using a new regenerative thermal oxidizer.

Following a project delivery evaluation, SPR elected to proceed with a construction manager at risk (CMAR) delivery model. Carollo Engineersassisted in developing the procurement documents and selecting J. R. Filanc, a California-based construction company, as the project’s CMAR contractor and the environmental firm BlueSource as the carbon broker. Carollo Engineers worked closely with J.R. Filanc during construction to inspect the work and provide engineering services.

Since being commissioned in October 2019, the new biogas-upgrading and pipeline-injection systems have successfully met Xcel Energy’s stringent gas quality requirements, which has allowed SPR to offset the equivalent of 2,000 gallons of gasoline per day and more than 13.5 million petroleum-fueled passenger vehicle miles per year. This translates to a reduction of more than 5,000 metric tons in fossil-fuel-based carbon-dioxide emissions per year.

Beyond its environmental merits, pipeline injection also provides a relatively rapid return on investment thanks to incentive credits from the U.S. Environmental Protection Agency’s Renewable Fuel Standard Program. Just in 2020, SPR’s Gas Recovery Facility earned approximately $1.5 million in revenue and, at this rate, is expected to have an overall project payback of six years.