Method and apparatus for producing bio-gas employing technology for improving quality of raw material fed thereto

Disclosed are a method and an apparatus for production of bio-gas, capable of improving quality of a raw material to be fed thereto. Among the raw material, a part free from inhibitory materials is directly introduced an anaerobic digestion reactor while the other part containing the inhibitory materials is introduced into a first solid-liquid separator and separated into a solid-phase material free from the inhibitory materials and a liquid-phase material containing the inhibitory materials. The solid-phase material in the first solid-liquid separator is fed to the anaerobic digestion reactor after hydrolysis. A liquid waste in the anaerobic digestion reactor and a liquid-phase material in the first solid-liquid separator are concentrated by a sludge concentrator. Through solid-liquid separation of the raw material, only a solid-phase sludge removed from the inhibitory materials is fed to the anaerobic digestion reactor, thereby suitably maintaining desired activity of microorganisms used for producing bio-gas.