ACR+ member ENT Foundation published a study in the Journal of Cleaner Production on "The impact of improper materials in biowaste on the quality of compost". They performed a statistical analysis of the factors that influence the quality of the compost produced in 20 plants in Catalonia, Spain, in particular, the effects caused by the presence of improper materials in biological waste.
 
The main results indicate that the presence of improper materials can lead to a negative impact on various quality composite parameters, in particular, heavy metal concentration, electrical conductivity, and maximum temperature in the self-heating test. The findings of this study support a necessary reduction in the quantity of improper materials, both through the improvement of waste separation at the source and at treatment plants prior to treatment.

Source: https://ent.cat