NOVELTY - Converting organic material to methane rich gas (P1) involves: a) vaporizing the organic material in an enclosed chamber free of oxygen and mixing the vaporized organic material with an excess amount of hydrogen gas and, optionally superheated steam at 450-650 degrees C to form a first mixture; b) heating the first mixture to temperature of 600-900 degrees C in presence of excess amount of hydrogen gas and superheated steam to form a gaseous mixture containing methane, hydrogen and acid; and c) neutralizing the gaseous mixture with a base.    USE - For converting organic material to methane rich gas (claimed). Also useful as clean burning fuels e.g. the methane rich fuel gas can be used as a fuel sources in energy-generating system, gas-fired turbines, steam-fired turbines and other engines, hydrogen power generation systems.    ADVANTAGE - The method minimizes the greenhouse gas emissions, and converts available carbon monoxide and hydrogen in the gas to methane and water, thus does not increases the overall fuel value of the gas but the higher methane to hydrogen and carbon monoxide ratio is desirable for certain applications such as vehicle use.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) reaction, mixing or milling apparatus (A1) comprising vessel rotatable about an axis, where the vessel includes a first end having a coaxial inlet or outlet for introducing or discharging materials from the vessel, the first end includes flange section having a generally radially extending first face, closure member arranged adjacent to the first end, the closure member includes generally radially extending second face in generally opposed relation to the first face, and inner and outer sealing elements arranged between the first and second faces, the inner and outer sealing elements defining a generally annular space, the annular space enclosing a sealing fluid for forming a seal between the vessel and the closure member; and    (2) combination (C1) comprising the apparatus (A1), and separation apparatus containing cyclonic chamber in fluid connection to and tangentially aligned with the outlet of the vessel for receiving discharged materials, exit conduit positioned above the cyclonic chamber for collecting gaseous materials from the cyclonic chamber, and hopper positioned below and connected in fluid connection with the cyclonic chamber for collecting liquid and solid materials from the cyclonic chamber.