Trade associations in the US have conducted detailed research into improving the recycling of post-consumer packaging.
The work has prompted a series of recommendations for product designers, MRF operators, equipment manufacturers and local authorities.
Manufacturers, for example, are urged to carry out greater research and development to improve the behaviour of non-bottle plastics in the MRF and the wider use of optical sorting.
It is suggested that operators pay more attention to cleaning disc screens and reducing material compaction.
The MRF Material Flow Study was commissioned by five national associations: the American Chemistry Council, the Association of Postconsumer Plastics Recyclers, the Carton Council of North America, the Foodservice Packaging Institute and the National Association for PET Container Resources.
It considered how materials flow through different types of MRFs, where packages end up, why packages flow in certain ways and what potential changes to the sorting processes could improve recovery.
The report considered materials being typically processed and those that currently are not.
“Recycling is a complicated system of consumer behaviour, collection programmes, sorting at MRFs and end markets. All stages of the value chain need to be similarly examined to create a full picture of recyclability,” it says.
“Examining and solving material processing challenges at the modern MRF is a necessary step in achieving success for the recycling industry of the future.”
A standard methodology was used at each of the five MRFs tested (see box below). Each one set aside enough typical recyclable material to run the facility for three hours. Materials that are not commonly accepted for recycling were ‘seeded’ to the normal stream.
Sorters were trained to handle the seeded materials which were generally allowed to flow naturally within the facility. Seeded materials therefore flowed to existing MRF products; new product grades were not produced for the seeded materials.
Video cameras monitored the flow of materials and the actions of the sorters.
- Form, material and rigidity have a significant effect on a product’s ‘sortability’ in the MRF
- Lightweighting of plastics can decrease recovery in a single stream MRF due to loss to the paper streams
- More equipment steps (disc screen decks or other separation equipment) can improve accuracy of splitting two-dimensional from three-dimensional materials
- Properly maintaining the disc screens (cleaning and replacing discs) can significantly reduce loss of containers to the paper stream
- Minimising compaction to maintain the form/shape of incoming material improves separation
- Continually training sorters to recognise a wide range of acceptable packaging is of growing importance
MRF equipment designers
- Further research and development is needed to improve consistency of behaviour of non-bottle plastics in the MRF
- Further testing and refining of optical sorter programming is needed to effectively optically sort a wider range of packaging
- Regular communications with local MRFs is critical to understanding behaviour of materials currently accepted and identifying additional materials that could be added
- As more materials are accepted, continual education for residents is essential to keeping contamination to a minimum
- For single-stream programmes, education to the consumer not to crush materials can improve recovery
- Continually evaluate and match MRF product quality and end market capabilities to ensure true recovery
The five represent the wide diversity of facilities that currently process recyclables in the US.
- One dual-stream and four single-stream facilities
- Throughput range of 10-35 US tons per hour
- Four different equipment manufacturers
- Between none and five optical sorters
- Varying combinations of disc screens and other mechanical separation equipment