A plant for generating biogas from organic biodegradable material containing liquid and solid components, such as waste products, in particular liquid manure from agricultural enterprises, comprises a biogas generation container (9) having a feed for the degradable material and a biogas collection zone (6) having a biogas outlet, and a flotation separation unit having a microbubble generation unit (15) for separating off the solid components from the liquid components of the degradable material. The flotation separation unit comprises a chamber region (14) which is delimited in the interior of the biogas generation container and essentially active in the direction of gravity and having a closed bottom and an open upper end arranged below the liquid level of the biogas generation container. Clarified liquid form the chamber region and a gas, in particular the biogas from the biogas collection region, can be fed to the microbubble generation unit for charging the liquid with gas. The outlet of the microbubble generation unit is connected to an inlet (18) of the chamber region in order to recycle microbubble-forming clarified liquid to the chamber region. Near the bottom of the chamber region, an outlet (116) for clarified liquid from the chamber region is provided. The flotation separation takes place in the chamber region in countercurrent flow to the ascending microbubbles.