The invention relates to a
methane-producing composite microbial inoculum and a preparation method thereof, which can solve the long-standing difficult problems that the existing
biogas digester is lack of high-efficient
methane-producing
bacteria, thereby resulting in long initial start-up time of
biogas production and poor stability of the
biogas production. Methanosarcina acetoacidophilum DSM-N0.2834, methanobacterium formicicum DSM-No.1535, methanobrevibacter arboriphilicus DSM-No.1125, methanolobus tindarius DSM-No.2278 and methanothrix concilii DSM-No.6752 collected in German collection of microorganisms and
cell cultures are adopted and inoculated in a
liquid methane bacterial culture medium under the anaerobic condition, the independent enlarged culture is carried out grade by grade respectively, and bacterial liquid after the cultured
methane bacteria is mixed together according to the volume ratio, thereby preparing a
liquid methane-producing composite microbial inoculum; and the
liquid methane-producing composite microbial inoculum can also be prepared into a
solid methane-producing composite microbial inoculum. The method has reasonable design and adopts the high-efficient strains with the
optimal combination and the rapid propagation technology, and the developed high-efficient methane-producing composite microbial inoculum can significantly accelerate the start-up time of the
biogas production when in new construction of the biogas digester and large material change, and improve the efficiency and the stability of the
biogas production of the biogas digester.