TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: The waste material from a waste-material storage tank is guided or induced to an anaerobic digestion tank, by waste-material piping, to perform thermophilic-digestion processing. The tank has digested-sludge circulation piping; contains partial digested sludge, which is circulated within the tank using the digested-sludge circulation piping; and has a digestion or sewage-gas piping for removing the generated gas. The method is performed with a high temperature anaerobic digestion apparatus. The apparatus guides or induces a digestive processed material from a processed-material storage tank by processed-material piping; and guides or induces the digestion or sewage-gas storage tank by providing the light emitting diode and allowing light transmittance partial or all to the digested sludge circulation piping, at least at the transparent part of the outer side of digested-sludge circulation piping; and the anaerobic digestion tank, at the transparent region of the outer side of the tank.Preferred Apparatus: The light emitting diode is confined to a transparent region besides the digested-sludge circulation piping and/or a transparent region besides the anaerobic digestion tank, which results in partial or all the light transmittance; or to a digested-sludge circulation pipe interior and/or an anaerobic digestion tank (preferably at the inside of the anaerobic digestion tank). EXAMPLE - An anaerobic thermophilic-digestion using a light emitting diode was carried out as follows. A glass bottle (500 ml) was filled with a mixture (400 ml) of a digested sludge and an acetic acid-glucose culture medium. Nitrogen was substituted fro the gas inside after sealing and the inside of a glass bottle was made anaerobic. From upper part, a light irradiation was carried out with the intensity of 1200 lux using blue light emitting diode. The glass bottle was cultivated for 28 days at 55degreesC. The digestion or sewage-gas production, which was accumulated in the gas back or bag was measured by a syringe, and the methane concentration was measured by gas chromatography. Comparative anaerobic thermophilic-digestion was carried out similarly as the test digestion, except that light irradiation was not performed. The methane gas production was determined. The methane gas (ml) produced in the test/comparative digestion was found to be 402/366 over 28 days. In the test anaerobic digestion, the enzyme reaction of methane-fermentation microorganisms was photoactivated and thus resulted in digestion or sewage-gas production, as compared to that from the dark filament affair. Further at a high temperature, the proliferation of photosynthetic bacteria was suppressed and a reducing power was not utilized for photosynthetic bacteria.