Process control systems currently available on the market for composting systems are suitable for measuring temperature, and in some - but not all - cases for measuring oxygen content. Based on the type of waste being composted, the process is regulated through preset aeration programmes or interval control that can be adjusted freely during the process. These measurement systems are suitable for the treatment of waste, or in other words, reaching a state where end-of-waste criteria are satisfied. However, they are not suitable for regulating composting processes where ensuring biological and biochemical quality is important. In the circular economy programme of the EU producing organic fertilizers from organic wastes is assigned a prominent role. Composts that are used for the production of such fertilizers have to satisfy quality criteria going beyond end-of-waste criteria (e.g. high humus content).