Biogas losses can be a costly expense in the Anaerobic Digestion process. The first reason is when the biogas escapes the system it cannot then be turned into electricity or injected back into the grid. The second reason is the cost of environmental damage. If the extent of damage to the environment can be proven then the process owner is liable to incur large fines.
Losses can occur under normal operating conditions from particular points in the process or they can occur when certain variables or parts of the process start to change. This being said there are common circumstances where biogas is lost. These are:
- Emissions from tanks downstream e.g. holding tanks
- Leaks from the gas system e.g. fixings, joints and valves
- Emissions and venting from safety devices e.g. Pressure relief valve
- Emissions from open or semi-open digestate storage tanks or lagoons
- Emissions from Combined heat and power units, engines and boilers
How Can We Reduce Biogas Losses?
There are a few methods used to prevent biogas losses depending on the circumstances. If for example, the biogas losses are from the gas system such as joints and valves then we can introduce a regular inspection and maintenance procedure on these components to ensure they are fit for use and if not, then any work is carried out correctly.
If the losses are being caused by open or semi-open tanks and lagoons, then we can look to introduce a fixed solution to ensure all gas is retained in the tank. This coincides with tanks that may be used for digestate.
Regular inspection and maintenance should be carried out on CHP units as per the manufacturer’s guidelines. This will help prevent unnecessary biogas losses when the CHP unit is in operation.
We can also use system monitoring to spot gas leaks in the process. Given the benchmark data that we could expect to see at any given time, we can compare this to the actual data. If we know that we are putting the same amount of feedstock into the process and getting less biogas out, then we know there is a problem somewhere. This could be a biogas leak somewhere in the system or biological inhibition within the digester.
