**Official Rulings:** - Gasification of lignite - Transformation of pipeline natural gas into compressed natural gas (CNG) off mine site
This class includes: - production of gas for the purpose of gas supply by carbonation of coal, from by-products of agriculture or from waste - manufacture of gaseous fuels with a specified calorific value, by purification, blending and other processes from gases of various types including natural gas
This class excludes: - production of crude natural gas, see 06.20 - operation of coke ovens, see 19.10 - manufacture of refined petroleum products, see 19.20 - manufacture of industrial gases, see 20.11