Automatic recognition of plastic packaging coming from post-consumer selective collection

The European Commission, in the Sixth Environmental Action Program, has indicated the necessity to reduce the volumes of waste generated through improved waste prevention and recycling initiatives. The targets of the European Commission are the reduction of the quantity of waste going to final disposal by around 20% by 2010 compared to 2000, and in the order of 50% by 2050 (European Commission, 2001). It is therefore of great importance to develop technologies that allow to recycle waste that cannot be prevented in order both to reduce the volumes of waste going to landfill and the demand for virgin raw materials. Different typologies of waste can be suitable for recycling processes. Industrial scraps and composite waste materials, like waste electronic equipment or end of life vehicles, can be suitable for precious elements recovering, while single material waste, like glass and plastic packaging coming from selective collection, can be reintroduced, after proper treatments, to the origin flow materials. A limiting factor to this last category of waste recycling is that, most of the time, recycled materials loose the physical-chemical characteristics of the origin materials and are, therefore, used for lower quality products (Hudgin,1998). Separately collected waste belongs to this last category since it consists of a single material stream in which it is possible to find different typologies of the same material, like different plastic polymers or different colored glasses, and the market of their recycled material is often of low value. The possibility of recognizing and separating different typologies of plastic packaging waste coming from selective collection has been investigated. Plastic waste is usually collected as a single material stream even when recyclers request for waste typologies identified both on the polymeric composition and on the physical properties (density, color). To reach high standards for recycled products, the different plastic types have to be separately processed. In Italy, waste plastic packaging collection, selection and recycling is managed by the Consortium for Collection, Recovery and Recycling of Waste Plastic Packaging (COREPLA). The COREPLA organization foresees that the plastic waste coming from selective collection is sent to transfer stations where waste is packed and distributed to the selection and storage centers. In the selection and storage centers the plastic waste is separated into three different classes depending on the plastic polymer: polyethylene (PE), polyetylenterephthalate (PET) and polyvinylchloride (PVC). The PET class is then divided on a color basis. The selected plastic wastes are then sent to recyclers in order to produce high quality plastic materials. The critical step of the COREPLA system is constituted by the selection processes. Selection processes are often based on manual selection that is neither efficient nor economical. A research has been carried out in order to set up a process for automatically recognizing and classifying plastic packaging waste coming from selective collection (Huth-Fehre et al., 1995). To this aim, samples of waste plastic packaging coming from selective collection have been considered and an image-based procedure has been set up.