Renewable Natural Gas Iowa Facility

Sioux City Wastewater Treatment Plant


As Sioux City’s selected wastewater treatment program manager, Bartlett & West recommended improving the city’s existing anaerobic digestion system using DMT’s fully integrated system. The advantage of using both the Sulfurex® CR and Carborex® MS for the client is one contract, one supplier, as well as easy mechanical, electrical and software integration. The Sioux City WWTP conditions and upgrades 800 scfm of biogas into 99.5% pure RNG for pipeline injection.

  • $4-7 million in city income over five years
  • Integrated Drying and Cooling
  • 99.5% methane recovery using 3-stage membranes


Year: 2020
Location: Sioux City, IA
Product: Sulfurex®CR & Carborex®MS
Biogas Inlet: 800 SCFM
H₂S concentration: 1600 to < 1.5 ppm
Biogas Source: WWTP
Application: Pipeline Injection

About the RNG Project in Iowa

The Sioux City Wastewater Treatment Plant (WWTP) in Iowa notably treats approximately 15 million gallons of wastewater per day. The facility also serves more than 30 industries and five communities from three states including Iowa, Nebraska, and South Dakota.

Construction on the renewable natural gas (RNG) plant in Iowa began in 2018. Firstly, Sioux City selected Bartlett & West as the wastewater treatment program manager. This entails leading teams of consultants and individuals to design several improvement projects for the City. Bartlett & West then recommended improvements to the City’s existing anaerobic digestion system using DMT’s fully-integrated system. This included the Sulfurex®CR, a chemical desulfurization unit, to remove hydrogen sulfide (H2S), as well as the three-stage Carborex®MS, a membrane separation technology, to extract carbon dioxide (CO2) from the methane (CH4) stream. Despite an ongoing pandemic, the RNG Iowa facility was operational in 2020.

“By partnering with experienced technology suppliers such as DMT, we help water resource recovery facilities like Sioux City conceptualize projects that contribute to their energy management goals while meeting compliance and performance targets.”

Randy Kenyon, Senior Project Manager of Bartlett & West
Sulfurex CR and Carborex MS in Sioux City, Iowa - RNG Wastewater Treatment Plant
Within the same building is the Sulfurex®CR for H₂S removal as well as the Carborex®MS for CO₂ removal.

Project Results

Sioux City’s WWTP is the second renewable natural gas plant in the state of Iowa. The facility converts 800 SCFM of biogas to produce up to 99.5% pure RNG for direct pipeline injection. In doing so, this project generates enough renewable energy equivalent to replacing 1.5 million gallons of gasoline annually.

Previously flared, the biogas generated from this WWTP now creates a revenue stream for Sioux City. This revenue will help pay for the project itself. Sioux City also hopes to use this revenue to offset any increase in gas rates for the communities it serves. It’s estimated that this $11 million renewable energy project will generate $4-7 million in city income after five years. Creating a circular economy, this RNG facility is a great return on investment for the state of Iowa and its people.

“This project positions Sioux City as a leader in the Midwest region. We are proud to reduce our carbon footprint working with companies like Bartlett & West and DMT Clear Gas Solutions to make it happen.”

Mark Simms, Utilities Director for Sioux City

Customer Service

DMT continued to commission this project during the COVID-19 pandemic, receiving high remarks in customer service and support by the client.

This RNG facility uses the Sulfurex®CR & Carborex®MS.

For key biogas contaminants, DMT offers one or a combination of technologies. The technology selection is based on an analysis of your biogas composition, inlet gas flow, pollution load and RNG application. Based on your CAPEX, OPEX and/or TCO needs, we provide our customers with an innovative, economical solution.