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Align RNG issued air permit for North Carolina biogas facility

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Align RNG, a joint venture between Dominion Energy and Smithfield Foods, has been issued an air permit for a proposed biogas gathering and processing facility in Duplin County, North Carolina (NC).

The NC Department of Environmental Quality’s (DEQ) Division of Air Quality (DAQ) issued the permit, which will see the facility classified as synthetic minor, meaning it will be required to comply with all applicable standards including the National Ambient Air Quality Standards.

The final permit includes several changes from the initial draft permit to address community concerns, including:

  • Hourly monitoring of the tail gas flow and hydrogen sulphide (H2S) concentration entering the ‘iron sponge’ sulphur removal control device

  • Daily record-keeping of the sulphur dioxide (SO2) emissions from the flares

  • An increased frequency of the analysis of the H2S concentration entering the facility to a monthly basis to account for potential seasonal variations

  • Specifies the maximum biogas flow limit for the facility

  • Requires an inspection, maintenance, and calibration plan for the facility’s air pollution control equipment and monitors to be submitted to DAQ for approval.


According to the DEQ, many of the concerns raised during the public process for the air permit related to the 19 animal feeding operations (pig farms) that plan to provide biogas to the facility. Any animal operation choosing to participate in the biogas project is required to submit a permit application to the Division of Water Resources. The facility will not process biogas until the animal operations receive the required permits.