This report is a background report for the "Guideline for plastic sorting at recycling centres". It describes the methodology used in preparing the guideline. The report first presents information from existing systems and the stakeholders that can be used by the recycling centres in their decision process. Secondly, the report describes the importance of understanding and communicating with the purchasers about the expectations on purity of the plastic, as well as the traceability of the plastic delivered to the purchaser and further down the value chain. Thirdly, the importance of information to both the personnel and the users is presented.The report is part of the Nordic Prime Ministers' green growth initiative: “The Nordic Region – leading in green growth”. Read more in the web magazine “Green Growth the Nordic Way” at www.nordicway.org or at www.norden.org/greengrowth.