TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The hydrogenotrophic methanogens comprise hydrogenotrophic methanogenic archaea comprising microorganisms of class Methanomicrobia which comprises Methanosarcina barkeri, microorganisms of class Methanobacteria which comprises Methanobacterium thermoautotrophicum or Methanothermobacter thermautotrophicus, or microorganisms of class Methanococci which comprises Methanocaldococcus jannaschii, Methanocaldococcus fervens or Methanotorris igneus. The carbon monoxide metabolizing microorganisms comprise bacteria of class Clostridia comprising Carboxydothermus hydrogenoformans or archaea comprising microorganisms of class Methanomicrobia which comprises Methanosarcina barkeri and microorganisms of class Thermococci which comprises Thermococcus sp. strain AM4.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The method additionally comprises (a1) producing hydrogen by microbiologically reacting carbon monoxide present in the reactant gas mixture, with water, and (b1) producing methane by microbiologically reacting carbon monoxide present in the reactant gas mixture, with hydrogen. The step (a1) is carried out between the steps (a) and (b). The thermal gasification of carbon-containing starting materials, is carried out in a heat pipe reformer. The hydrogenotrophic methanogens convert carbon dioxide or carbon monoxide and hydrogen to methane at 20-110 degrees C. Carbon dioxide reacted in the step (b), is obtained by the thermal gasification of the carbon-containing starting materials, combustion of biogenic starting materials, or industrial- or agricultural processes with carbon dioxide emission. Hydrogen is produced by regenerative- or non-regenerative production, preferably electrolysis, in addition to the thermal gasification of the carbon-containing starting materials comprising biogenic materials. The method is carried out continuously. The waste heat obtained from the thermal gasification of the carbon-containing starting materials, is used for heating the fermenter and maintaining the reactor at reaction temperature. Preferred Components: The reactant gas mixture obtained in the step (a), comprises at least 20 vol.%, preferably at least 40 vol.% hydrogen. The nutrient medium comprises ash, ash mixture or a mixture of ash and coke, which are optionally used as an admixture with water. The ash and optionally coke are obtained by thermal gasification or combustion of biogenic substances. The method additionally makes use of volatile components comprising gaseous nitrogen and/or sulfur-containing compounds obtained by thermal gasification- or combustion of biogenic substances, for providing required nutrients for the microbiological methanation. EXAMPLE - No suitable example given.