5.1 Initial Testing

Some of the biogas systems can have a theoretical lifespan of up to 20 years. Technical issues are often named as one of the main challenges. These can be avoided, given that adequate operation and maintenance of the system is ensured.

Once the system is constructed, it is important for all individuals involved to receive proper training, as either the users or a designated responsible person may perform operational tasks and minor maintenance activities.

Before starting the digester, it’s crucial to conduct a tightness test once the system is built.

To demonstrate the testing process, a protocol for an underground fixed dome digester was selected. Please note that each type of digester has its specific testing protocol that ideally is provided by the implementer, a biogas expert, or can be found in the literature.

Protocol for an underground fixed dome digester

To ensure the tightness of underground digesters after construction, water and pressure tests are conducted.

Below is a step-by-step guide on how to perform these tests.

To ensure efficient operation, the tasks involved in running a biogas plant can be divided into categories, such as the initial start-up phase and daily, weekly, monthly, or annual activities. 

Step 1 – Water Test:

Fill the digester with water: Inject water until the water level reaches the zero-pressure line. It’s essential to stop adding water once the level reaches this point.

Mark Water Level: After the digester is full, mark the water level line and observe for 12 hours.

Check for Leakage: If there is no significant change in the water level during the observation period, it indicates no leakage, and the digester is ready for the pressure test.

Step 2 – Pressure Test:

Inflate with air: Inflate the digester with air until the pressure barometer reaches the design working pressure. Once the desired pressure is reached, turn off the air supply and close the valve.

Observe for 24 Hours: Observe the air pressure for 24 hours.

Check for Leakage: The digester meets requirements if the drop-out value of the barometer is <3% of the design pressure.