Biogas holders are an essential part of an anaerobic digestion system providing a biogas storage buffer and a constant system pressure.
The traditional methods of biogas storage on wastewater treatment sites where anaerobic digestion is used have been:-

• A steel fabricated floating roof located on top a concrete digester tank
• A stand alone biogas holder comprising of a concrete tank filled with water, to provide a gas seal, and;
• A steel fabricated floating ‘bell’

Both the roof/bell rise and fall as biogas is produced and used with the weight of the structure providing a constant pressure in the biogas pipework collection and delivery system. The movement of the roof/ bell is monitored by an ultrasonic level sensor which is used to control the operation of gas utilisation plant such as boilers, CHP engines and flares.

Many of these existing steel bells have now gone beyond their design life and are causing operational problems. Replacing with a membrane gas holder offers an economical solution and allows the concrete asset to be retained.