NOVELTY - Sequestering (M1) carbon dioxide in a subterranean formation involves identifying an indigenous methanogenic microorganism in the subterranean formation and/or introducing an exogenous methanogenic microoganism into the subterranean formation; introducing carbon dioxide into the subterranean formation; and promoting metabolic conversion of the carbon dioxide to methane by hydrogen-oxidizing and carbon dioxide-reducing methanogenic microorganism.    USE - For carbon dioxide sequestration and microbial methane production in subterranean formation (claimed); methane gas is used as fuel.    ADVANTAGE - The process utilizes natural microbiological methods of sequestering carbon dioxide and to promote its conversion to methane under suitable environmental conditions.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) method (M2) for carbon dioxide sequestration and microbial methane production in a subterranean formation where a natural source of hydrogen indigenously produced is available in the subterranean formation involving (a) analyzing at least one component of the formation to determine characteristics of the formation environment; (b) detecting the presence of a microbial consortium comprising a carbon dioxide-reducing methanogenic microorganism (C1) within the formation; (c) assessing (C1) in the consortium are currently active or whether exogenous microorganisms or other stimulants are needed; (d) determining whether the microbial consortium comprises a methanotrophic microorganism (C2); (e) determining at least one characteristic of (C1) or (C2) and comparing with a known microorganism using information obtained from steps (a) to (e) to determine an environment that promotes carbon dioxide sequestration and in situ microbial generation of methane; (f) modifying the environment to promote carbon dioxide sequestration and in situ microbial generation of methane; and (g) introducing carbon dioxide into the formation before, after or during any one of steps (a) to (e); and    (2) producing (M3) methane using methanogenic microorganisms involving introducing methanogenic microorganisms into a surface reactor containing hydrogen generating rock media; introducing carbon dioxide into the surface reactor; promoting generation of hydrogen from the rock media in the reactor; introducing additional hydrogen from a subterranean formation or other natural or industrial source into the surface reactor as required; and promoting metabolic conversion of the carbon dioxide by the methanogenic microorganisms to methane.