Due to its high content of humic substances, compost from bio-waste improves the structure and fertility of soils serving also as a sink for CO₂. But compost is also contaminated with numerous compounds, for example, plastics, glass particles, etc., mostly due to incorrect sorting by the waste producer, that is, households. The contamination even increases when covering areas of a high population density as is also evident from experience in Germany with a steadily increasing proportion of bio-waste. Only compost with high quality and minimum contamination is an acceptable fertilizer. A structured interview of experts investigated which measures or combinations of measures are best suitable to reduce the rate of misplaced materials in the organic waste. Only responsible persons were interviewed whose municipalities extensively collect separately bio-waste since years and have a low rate of unwanted materials. The questions focus on the identification of the misplacements according to their kind and quantity, the respective collection system, the regional statutes and their enforcement as well as the kind and extent of public awareness measures. The respective necessary measures are being discussed. This systemic approach can be transferred to other regions that intend to collect large quantities of bio-waste separately.