Engineering Efficiency: How Unison Solutions Elevated RNG Production in Roanoke with U.S.-Made Precision

By Unison Solutions

Unison Solutions, an employee-owned company, is an industry leader in biogas upgrading and conditioning systems. Based in Dubuque, Iowa, we have designed and manufactured over 400 biogas systems throughout the U.S. and Canada.

Our extensive knowledge of the stringent safety regulations required in the municipal market has made us the manufacturer of choice.

In Roanoke, Virginia, a biogas upgrading plant—designed and built by U.S.-based manufacturer Unison Solutions has been successfully purifying raw biogas from a regional wastewater treatment plant into pipeline-quality RNG using SEPURAN® Green membranes since May 2023.

Once upgraded to RNG, the system feeds pipeline-quality product gas to the Roanoke gas pipeline, serving customers in the Northeastern U.S. region.

The Roanoke Regional Water Pollution Control Plant, part of the Western Virginia Water Authority, treats 37 million gallons of wastewater per day.

Biogas is formed through anaerobic digestion in the solids treatment process, which is then upgraded into RNG. Unison Solutions’ upgrading system filters out hydrogen sulfide, particulates, moisture, volatile organic compounds, and siloxanes prior to RNG upgrading.

The RNG system utilizes Evonik’s patented three-stage membrane system to remove carbon dioxide from a 280 scfm feed flow, achieving a methane recovery of over 99%.

This exceptionally high recovery rate is made possible by Evonik’s robust and high-performing SEPURAN® Green G5X hollow-fibre membranes.

These membranes have the highest CO₂/CH₄ selectivity available on the market, enabling the production of high-purity RNG with superior efficiency. Evonik’s patented three-stage process enables very high CH₄ recovery rates—over 99.5%—while using only one compressor.

The installation of Unison’s premium RNG system also includes a skid-mounted enclosure with a connected electrical room. The enclosure is temperature-controlled, with managed airflow throughout and internal safety monitors for operators.

To meet the project’s installation requirements, the electrical portion of the system was also designed to provide power to accessories and auxiliary equipment associated with the RNG site, such as the gas chromatograph, injection equipment, and outdoor lighting.

Made in the U.S., the system’s high-quality components, expert workmanship, thorough testing and inspection, and customization to meet site-specific requirements all contributed to the success of this project.

For more information, read our Efficiency Magazine.