Recycling today usually refers to mechanical recycling. Plastic waste is collected, sorted, shredded and cleaned before being melted down and processed into new products. The basic chemical structure of the plastics remains unchanged. The purer and cleaner the plastic waste that is fed into the process, the higher the quality of the end product. This means that the waste streams must be pre-sorted accordingly. For example, many PET bottles, which generally only consist of one type of plastic, or lightweight packaging materials are well suited.