Biological CH4 is produced by the process of syntrophy between fermenters and methanogens. CH4 from biological waste products is produced by complex syntrophic systems, which additionally include aerobes and facultative anaerobes jointly working to convert various organics to substrates for the fermenters. However, as a result of complexity of the constituents, these systems are prone to environmental changes,,such as those in-the O-2 concentration and pH. Furthermore, H2S from sulfur-containing organics is corrosive to metals in the equipment. Here; we studied the principles of biological CH4 production through establishment of a system where combustible H2S-free CH4 can be produced daily: Toward this objective, we applied a solid-phase cultivation method, using dacite pumice, to a simple syntrophic system-of Thermosipho globiformans and Methanocaldococcus jannaschii. Dacite pumice, used as a solid support for anaerobic co-cultivation of-these microorganisms, was the inoculum for-solid phase carried-over cultivation (SCC): When SCC was conducted with an aerobic medium under gas phase (air), H2S-free CH4 was produced. Microporous structures of the dacite pumice preserved the anaerobic environment, and H2S from microbial metabolic activities-made the bulk liquid phase anaerobic. This was scavenged by O-2 in the air. When CO2 was removed by placing solid NaOH, separated from the medium, the CH4 concentration increased to a combustible level after 24 h of aerobic SCC. Manual decompression of the gas phase by Sucking with a syringe-further enhanced the CH4 production. These results together indicate that the removal of O-2 and CO2 had effects similar to that of decompression. We; therefore, conclude that the system developed in this study would be useful for urgent, local CH4 production.