Published September 2018
A serious issue, from both a risk and cost perspective, comes from the thick, sludgy foam produced in AD. This is a natural by-product of the biological reaction that converts waste to biogas, but its behaviour can be unpredictable and difficult to manage. In fact, foaming is a persistent, complicated issue for many biogas producers.
As previously stated, foaming is a normal part of the microbial reaction that produces biogas. However, research has shown that the problems caused by excess foam can actually reduce overall gas production by up to 40%. This level of productivity loss can be seriously detrimental to the profitability of an AD plant – and that doesn’t even consider the additional risks that can arise from foam in the process.
As biodigesters are sealed units, it is hard for operators to monitor what is happening inside. If foam in an anaerobic digester gets out of control it can cause serious, even catastrophic problems:
- Damage to gas compressors, pumps and other sensitive process equipment
- Congestion and blockage of safety valves and pressure relief valves
- Rupture and destruction of digester tanks and domes, leading to:
- High repair or replacement costs
- Months of downtime with associated loss of earnings
- Severe pollution hazards and clean-up costs
- Environmental fines
- Damage to company and site reputation
- Potential revoking of operating permits
