Exemption of methane from effluent treatment systems removes excise duty liability under the central excise tariff. The Central Government exempts methane falling under sub heading 2711.29 and generated in effluent treatment systems from the whole of the excise duty leviable under the Schedule to the Central Excise Tariff Act, 1985, by notification issued under the rule making power in the Central Excise Rules, 1944.