Utile have recently designed and installed a sequential batch digester gas mixing system, for retrofit on one of four digester tanks at their Westwood AD Plant. This system has given the site reliability, much reduced maintenance and above all, increased gas yield over their original multiport system. The digester now operates with a single, Utile L175HP oil lubricated sliding vane gas compressor, feeding 18 injection points at a time. The 4No. rotary valves have been removed to provide simplicity and satisfaction to the client.