Tenn. Code § 65-28-208
The addition of refined landfill methane described in this part into any natural gas stream and the resulting use of the gas stream consisting in part of the refined landfill methane and in part of natural gas by any person purchasing or receiving the gas shall be considered for all purposes to be the use of natural gas within the meaning of any permit previously granted or granted in the future to the person by any agency of this state. It is expressly provided that this section does not authorize the use of raw, unprocessed or unrefined gas generated by decomposition at solid waste landfills to be sold or used as natural gas whether alone or in combination with natural gas. Any prohibition in any existing or future permit issued by this state applicable by its terms to the use of landfill gas shall be deemed to refer only to the use of the raw, unprocessed or unrefined gas generated by decomposition at solid waste landfills without treatment, refinement or purification as contemplated by this part; and any such prohibition applicable to landfill gas is expressly deemed to neither refer to nor prohibit the use of refined landfill methane as described in this part.
T.C.A. § 65-28-208