Determining efficiency for chemical recycling processes is a complex problem for which no uniform rules exist. In close cooperation with the European Commission's Joint Research Centre (JRC), OVAM's plastics team has developed a mathematical model to determine the efficiency of such processes. The model was published in the JRC research report "Towards a better definition and calculation of recycling". With this document OVAM provides a scientific basis on which the European Commission can work to develop European standards for determining recycling efficiency.