NOVELTY - Dual-purpose methane gas pond of double-hydraulic pressure straw dejection fermented by a self-circulation intermediate-temperature two-step method comprises a fermenting pond (1), a feed inlet (2) and a discharge opening (8). The fermenting pond with a big circular angle (12) at the bottom is a rectangular fermenting pond. The pond opening is buckled with a hydraulic pressure room (6) with an upper opening. The fermenting pond is sealed with hydraulic pressure room by a bolt, sealing material and respective flanges at buckling position to form a rectangular pond body with an upper opening.    USE - Used as a dual-purpose methane gas pond of double-hydraulic pressure straw dejection fermented by a self-circulation intermediate-temperature two-step method.    ADVANTAGE - The methane gas pond: increases the proper registered permanent residence of the methane pond to 100%; saves energy; reduces the discharge from methane gas pond; increases gas production efficiency; occupies less volume; is economical; convenient to transport and mount; and easily discharges the straw residue with the help of a push plate.    DETAILED DESCRIPTION - Dual-purpose methane gas pond of double-hydraulic pressure straw dejection fermented by a self-circulation intermediate-temperature two-step method comprises a fermenting pond (1), a feed inlet (2) and a discharge opening (8). The fermenting pond with a big circular angle (12) at the bottom is a rectangular fermenting pond. The pond opening is buckled with a hydraulic pressure room (6) with an upper opening. The fermenting pond is sealed with the hydraulic pressure room through a bolt, sealing material and respective flanges at the buckling position to form a rectangular pond body with an upper opening and placed on the floor. The rectangular air storage chamber is partitioned at the bottom of the hydraulic pressure room. The left vertical wall and the right vertical wall of the air storage chamber are in a certain distance from the left and right vertical walls of the hydraulic pressure room to form the feed inlet and the discharging opening. The push plate can be pulled or pushed up and down through certain distances. The top cover of the air storage chamber is distributed with five transverse rib plates. The bottom of the air storage chamber is low at the left and high at the right. The lower side is positioned at the side of the feed inlet and the higher side is positioned at the side of the discharging opening. The bottom of the air storage chamber comprises an arc-shaped partition board with an upward arc-shaped top. The plane of the partition board is drilled with multiple through holes and the joints of the structures are connected in a sealing manner.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the dual-purpose methane gas pond.    Fermenting pond (1)    Feed inlet (2)    Hydraulic pressure room (6)    Discharge opening (8)    Fermenting pond with a big circular angle (12)