NOVELTY - The biogas tunnel comprises a funnel-shaped anaerobic digestion tunnel, a pressure tank, an excrement feed tank, a pipe for guiding excrement into the anaerobic digestion tunnel, and a gas duct connecting a gas container with a gas utilizing unit. The anaerobic digestion tunnel is made of reinforced concrete. A wall of the anaerobic digestion tunnel has a trapezoidal vertical cross-section with a longer upper base. An upper surface of the anaerobic digestion tunnel is concreted integrally with the tunnel wall.    USE - Used as a biogas tunnel.    DETAILED DESCRIPTION - The biogas tunnel comprises a funnel-shaped anaerobic digestion tunnel, a pressure tank, an excrement feed tank, a pipe for guiding excrement into the anaerobic digestion tunnel, and a gas duct connecting a gas container with a gas utilizing unit. The anaerobic digestion tunnel is made of reinforced concrete. A wall of the anaerobic digestion tunnel has a trapezoidal vertical cross-section with a longer upper base. An upper surface of the anaerobic digestion tunnel is concreted integrally with the tunnel wall. The excrement along with washing water passes through the guiding pipe into the anaerobic digestion tunnel. A bottom of the anaerobic digestion tunnel slopes towards the pressure tank. The pressure tank includes a residue containing compartment, a filter compartment, and a wastewater containing compartment. The anaerobic digestion tunnel includes a low level outlet disposed close to the bottom of the anaerobic digestion tunnel to communicate with the bottom of the residue containing compartment of the pressure tank. A bottom of the residue containing compartment is recessed to contain sandy soil and residue flowing from the anaerobic digestion tunnel. The filter compartment retains the residue in the compartment such that the wastewater flowing to the wastewater containing compartment is clearer. The wastewater containing compartment deposits residue of wastewater so that the wastewater discharged to the environment is clearer.