Abstract: A system and method for producing refined biomethane gas from a renewable natural gas source. The method may include receiving, by a vessel, processed biogas, the processed biogas having been processed from a renewable natural gas source. The method may include receiving, by a nitrogen rejection vessel assembly comprising a nitrogen rejection vessel, gas from the vessel. The method may include separating, by the nitrogen rejection vessel assembly, at least some nitrogen-containing molecules from the received gas. The method may include outputting, by the nitrogen rejection vessel assembly, nitrogen-removed gas. The method may include compressing, by a compressor, the nitrogen-removed gas. The method may include removing, by a dehydration vessel, at least some moisture from the compressed nitrogen-removed gas. The method may include outputting, by the dehydration vessel, refined biomethane gas.