Bert's anaerobic (absence of free oxygen) digesters apply the patented 'Power of Nature' (PON) mixing technology, which is based on the principle of communicating vessels. The left schematic shows that the downforce created by the expanding biogas (B) volume in compartment V2 pushes the digestate high up in V1 due to the open valve in V1. By closing the valve in V1 and releasing the biogas in V2 the digestate will flow back into V2, thus restoring the balance (center schematic). The principle is then applied in a reversed order (right schematic), and so on. No other biogas system is using this continuous natural process as consequently as does Bert!