It is not all that easy to fill a compost tunnel for phase II or phase III. If the filling procedure is not carried out correctly, a well made and well mixed phase I compost can be ruined on the spot.

Uneven compost temperatures during levelling, wet spots in the compost after pasteurisation and difficulties to clear ammonia are only some examples of problems that can occur when the filling process of the tunnel has not been optimal.

How to fill a compost tunnel correctly?

First of all the tunnel has to be filled as kind of a brick wall. So with a minimum of 2, but preferably 4 layers of compost on top of each other, especially in the case of higher filling rates over 1000 kg per square meter. A lot of companies claim to be filling in different layers, but the distance between the bottom of the first and the top of the second layer is only 0,25 to 0,5 meters. The minimum distance between the different layers should be at least one meter. In this way the air cannot float in between the layers.

To permit a proper airflow it is also important to fill the compost loose. The compost has to fall from above over the layer that has already been filled. The falling distance can be 0,5 to 1 meter. In this way the compost stays loose. If the compost drops down from a higher altitude or gets blown into the already filled amount by the filling cassette, it will be pushed into each other. When this happens, air will have difficulties penetrating through the material and the process is jeopardised.

Also the tunnel has to be equally filled from the beginning until the end. This seems easy, but too often the people that operate the machinery are on the floor of the tunnel. In this way they do not have an overview over the compost. Fitting the seat that the operator sits on in a higher position can solve this problem and make sure the filling is done equally.