Therefore, the effects of compost on the soil and the plants require studies on:
- its nutrient contents to contribute to the plant nutrient requirement
- its organic contents for the calculation of the humus balance
- its protection of the soil against erosion
- its activation of soil microbes
- its potential content of contaminants such as heavy metals.
A joint project was initiated in 1997 in cooperation with the Bergischer Abfallwirtschaftsverband, Engelskirchen, and the Landwirtschaftskammer Rheinland to examine the above effects of composted digestates on soil ecosystem and to elaborate a regional recommendation for its utilisation.