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  • County, Southwest Gas project converts wastewater gas into clean-burning methane

    Oct 22, 2021 | Read More News
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    Biogas opening
    Photo (left to right): Bobby DeAngelo, Pima County Regional Wastewater Reclamation; Jackson Jenkins, Director, Pima County Regional Wastewater Reclamation; Rex Scott, Pima County District 1 Supervisor; John Hester, Southwest Gas President and CEO; Sharon Bronson, Chair, Pima County Board of Supervisors; Chuck Huckelberry, Pima County Administrator; Jeff Prevatt, Pima County Regional Wastewater Reclamation; Ignacio Garcia, muralist; Julie Williams, Southwest Gas Vice President Southern Arizona Division.
    Pima County Regional Wastewater Reclamation Department, in partnership with Southwest Gas, will start delivering clean-burning renewable natural gas made from biogas, a byproduct of wastewater treatment, to homes and businesses throughout the community.

    County officials and Southwest Gas held a dedication ceremony Oct. 21 to mark the opening of the Tres Ríos Renewable Gas Center biogas cleaning facility. This site will produce 552,000 cubic feet of 99-percent pure renewable natural gas each day and patch it directly into the Southwest Gas conveyance system bringing major benefits to our environment and taxpayers.

    “By finding a way to utilize a waste product and further the County’s sustainability goals, this innovative project exemplifies the commitment and forward-thinking of our Pima County departments,” Pima County Board of Supervisors Chair Sharon Bronson said.Biogas process

    Biogas is the byproduct of a secondary wastewater treatment process. The gas produced in this process had previously been flared off as a waste product that was too high in moisture, carbon dioxide, and other impurities for commercial viability. The new refinery removes most of the impurities leaving a clean-burning, renewable fuel.

    Built with the coordination and partnership of Southwest Gas, the Tres Ríos facility is the first of its kind in Arizona to connect into a gas delivery grid. Southwest Gas President and CEO John Hester said incorporating gas from renewable sources like the one at Tres Rios was a growing part of the company’s mission.

    • The daily production of RNG at Tres Rios is the equivalent of:

      4,358 gallons of diesel and gasoline each day or 1.59 million gallons per year.

    • As a clean-burning, renewable fuel source RNG:

      Emits 30 percent less carbon dioxide than diesel or gasoline
      Emits 50 percent less carbon dioxide than coal when burned for power generation.
      RNG produced at wastewater treatment facilities emits 95 percent less carbon emissions than processes that produce diesel and gasoline.

    • Sale of the byproduct gas corresponds also with the County’s and RWRD’s sustainability goals. These include:

      Biosolids, processed waste used as organic fertilizer at area farms
      Phosphorus harvesting from struvite.
      Treated water reused to irrigate parks and other public spaces.
      Discharged water into the Santa Cruz River sustains a growing ecosystem and ultimately infiltrates the surface to recharge groundwater stores.

    “Renewable natural gas is a really big priority for Southwest Gas,” Hester said.

    Pima County plans to sell its gas production at market rates to Southwest Gas, creating a revenue stream that will help offset the costs of the facility and postpone the need for future sewer rate increases for Pima County residents.

    In addition, Tres Ríos RNG qualifies for federal Renewable Fuel Standard (RFS) program incentives. Participation in the program helps to achieve the goals of reducing greenhouse gas emissions and expanding the use of renewable fuels.

    “We have, through the leadership of the Board of Supervisors, an ethic of sustainable energy and conservation,” Pima County Administrator Chuck Huckelberry said.

    The biogas project is a part of Pima County’s ongoing efforts to preserve unique desert environments and reduce greenhouse emissions, Huckelberry added, noting the County’s fleet of 100 electric vehicles and numerous solar generation facilities that allow the County facilities to receive 20 percent of its power from the sun.

    The technology at the Tres Rios facility uses Carborex®MS three-stage membrane separation technology developed by DMT Clear Gas Solutions.

    “DMT is proud to bring the Tres Ríos RNG Center in Arizona to market. I am especially thankful to Pima County, our internal team, and all partners involved for its successful completion,” said Theo Zuijdwijk, CEO of DMT.

    Prior to completion of the biogas cleaning facility, RWRD used about 20 percent of the gas produced onsite for heating and other fuel uses. The new facility allows for 100 percent utilization, producing clean-burning gas.