NOVELTY - Method for controlling an anaerobic fermentation process, involves providing an oscillatory flow reactor having a reaction tube (1) with baffles (7) along its length, introducing (3) fluid material into the tube, passing the fluid material through the tube at a speed that allows anaerobic growth and fermentation of the feed material, while causing or allowing the fluid to oscillate with respect to the baffles, and collecting the fermentation products.    USE - The method is useful for controlling anaerobic fermentation and obtaining products including fuels, microbial biomass, platform chemicals, extracellular enzymes (all claimed) and useful end products such as hydrogen, methane, volatile fatty acids such as acetate, succinate, ethanol and lactic acid.    ADVANTAGE - The method is rapid and provides a mimic of rumen ecosystem and to grow resilient consortium of obligately anaerobic microorganisms continuously and outside their natural ecosystem. The reactor has excellent potential and versatility and can be used for wide range of microbiological applications. The method is eco-friendly.    DETAILED DESCRIPTION - Method for controlling an anaerobic fermentation process, involves providing an oscillatory flow reactor having a reaction tube (1) with baffles (7) along its length, introducing (3) fluid material into the tube, where the fluid comprises a finely divided substrate material, facultative and/or obligate anaerobic organisms and feed material for the organisms, and where the feed is possibly being wholly or partly identical to the substrate, passing the fluid material through the tube at a speed that allows anaerobic growth and fermentation of the feed material, while causing or allowing the fluid to oscillate with respect to the baffles, and collecting the fermentation products. An INDEPENDENT CLAIM is included for oscillatory flow reactor.    DESCRIPTION OF DRAWING(S) - The drawing shows apparatus for controlling anaerobic fermentation.    Reaction tube (1)    Inlet (3)    Baffles (7)    Reservoir (21)