Roanoke Gas breaks ground on RNG project in Virginia

By RGC Resources Inc. | May 17, 2022

The Western Virginia Water Authority (Authority) and Roanoke Gas Company (Roanoke Gas), a subsidiary of RGC Resources, Inc., have entered into a cooperative agreement to produce commercial quality renewable natural gas, or RNG, from biogas produced at the Roanoke Regional Water Pollution Control Plant. This RNG product, the first of its kind in the Commonwealth, will necessitate construction of a digester gas conditioning system and interconnect facility at the Water Pollution Control Plant (WPC Plant). Representatives from the Authority, Roanoke Gas and the community will break ground on this project Tuesday, May 17 at 2 p.m. at the Roanoke Regional WPC Plant.

Biogas, also known as digester gas in wastewater treatment, a mixture of methane (63 percent) and carbon dioxide (37 percent), is produced as a by-product of the anaerobic digestion treatment process as bacteria consume the organic solids that are removed earlier in the wastewater treatment process. Anaerobic digestion is employed at the WPC Plant as it is a much more energy efficient way to treat solids compared to other methods such as aerobic digestion and heat drying. “While this gas has been used as a fuel source at the facility over the years, this exciting next generation of resource recovery of digester gas will utilize a new approach to maximize the benefit to the broader community,” according to Michael McEvoy, executive director Western Virginia Water Authority.

Utilizing an advanced membrane separation system, raw digester gas will be refined to commercial quality natural gas for use within the greater Roanoke community, creating the potential for the protection of the environment and complete recycling of waste at a level only imagined a decade ago. This cooperative project is an example of another area for energy recovery beginning to be realized within the wastewater treatment industry and will have far reaching benefits within our community and beyond. At full buildout, the proposed digester gas conditioning system will have the ability to treat a biogas design flow of 550,000 cubic feet per day (cfd) to create commercial quality RNG.

The initial treatment of the biogas includes a pretreatment step which removes hydrogen sulfide, moisture, siloxanes, and VOCs. A membrane filter system will remove the carbon dioxide (CO2) and help polish the gas to commercial quality. In the design of this particular installation, a third stage of membranes, located inside the digester gas conditioning system, will further treat all the produced tail gas and recover residual methane. Compression is required to boost the digester gas to pipeline pressure at the interconnect facility.

Multiple treatment technologies were evaluated and the selected company, Unison Solutions, is a recognized industry leader in biogas treatment technology. Unison has a demonstrated history of success providing the treatment technology for similar gas treatment projects as this market emerges within the United States.

“We are thrilled to have the opportunity to partner with the Western Virginia Water Authority on such an impactful and needed project,” stated Paul Nester, president and CEO of Roanoke Gas Company. “Our shared desires to improve the environment, utilize the best technology and most importantly, serve this community, have spurred approximately $16.5 million dollars of combined investment and added a much needed source of safe, clean natural gas.” Roanoke Gas projects this new supply source will provide enough natural gas to heat 500 homes on a cold, winter day.