UASB Tank for Biogas Project: The Reactor, Not the Gas Holder A UASB reactor is not a tank that happens to make biogas - it is a hydraulic machine whose entire performance rests on keeping a bed of granular sludge suspended in an upward flow, while the gas those granules produce is separated from the liquid and the solids before any of it leaves the vessel. Get the upflow velocity right and the bed fluidises gently and retains biomass measured in tens of grams per litre. Get