NOVELTY - The feed chamber (2) is united with the digester (8) at one end face, and separated from it by partitions (5a, 5b). The upper partition (5a) is spaced from the base (15) below a set minimum level (23) of the suspension in the digester. With the lower partition (5b) it forms a passage (16). The lower partition is sealed with the base, forming a retention volume of the feed chamber, separated from the fermenter and with an overflow into it. The inlet chamber has a filling opening (17) at the top, where biomass and water are charged, displacing the suspension contained, the level (23) being lower than the upper edge of the digester wall (1).    USE - A biogas plant in which a biomass-water suspension is supplied to a horizontal, stirred digester tank.    ADVANTAGE - The new arrangement is compact and economical. It is also readily transported. The design accelerates breakdown of biomass and optimizes gas production. No pumping or additional conveying equipment is required. At the same time the gas-lock design positively prevents gas escape via the feed chamber.    DETAILED DESCRIPTION - The fermenter is trough-shaped, covered by a gas-tight covering (7). The cross section of the trough is angular or rounded at the base. It is single- or double-walled. The horizontal shaft (14) of the stirrer (10) is carried in bearings mounted in the far end wall, and in one partition. The passage is situated below, above or at the height of the shaft bearing. The upper opening of the digester is a sheet, a swinging- or removable cover. At the top a gas removal hood or line is fitted. The feed chamber is of the same cross section as the digester. An outlet opening in the base or a wall, removes digested biomass. A stirrer and/or cutter in the feed chamber forms a suspension. Suspension is fed into the digester only by equalization of levels. The outer end face of the feed chamber is angled or vertical. Further details and variants of the basic design are provided. A digester heating circuit is included.    DESCRIPTION OF DRAWING(S) - A vertical cross section seen in side view, shows an implementation of the fermenter.    digester wall (1)    feed chamber (2)    upper partition (5a)    lower partition (5b)    gas-tight covering (7)    digester (8)    stirrer (10)    horizontal shaft (14)    base (15)    passage (16)    filling opening (17)    set minimum level (23)