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  • Rights: University of Waikato
    Published 9 November 2018 Referencing Hub media

    Take a look inside the materials recovery facility (MRF) to see how glass, paper and cardboard, aluminium, steel and plastics are sorted into their different types.

    This is the second of three videos used to explore the recycling process with levels 1–4. The videos have a focus on Auckland recycling but are also relevant for students across New Zealand.

    Related content

    This video is part of a series of three videos, the other videos are:

    The teaching and learning activities that use these videos can be found here.



    Here, inside the MRF, recyclables are then sorted into their different types – glass, paper and cardboard, aluminium, steel and plastic. Some ingenious technology is used to sort these recyclables as well as many more people throughout the process.

    Rotating cylinders called trommels sift out bottles, containers and cans and separate paper and cardboard from the other recyclables. Each trommel has holes in its walls to allow items to fall through. The holes in each trommel are different sizes to sift out different types of recyclables.

    Paper and cardboard is further sorted using star screens. These steep screens are made up of rows of star-shaped discs, which flick up the paper and cardboard items, causing them to catch the air and flitter up to the top while heavier items fall off the bottom.

    Steel items are extracted using a huge magnet. As materials pass under the magnet, all steel items are picked up and then pushed off onto another conveyor. Aluminium items are removed from the mainstream by a different kind of magnetic system called an eddy current, which causes these items to be propelled onto a separate conveyor.

    Plastic bottles and containers are sorted by an optical sorting machine, which uses infrared light and smart cameras to read the plastics type, then air jets push individual pieces into the correct chutes.

    Glass gets broken down into smaller pieces while passing through the first few sorting machines and then goes to the glass plant where it is sorted into brown, green and clear colours using an optical sorting machine, much like the one that sorts the plastics.

    Finally, sorted recyclables are compacted into large bales ready for transport to processing facilities ready to be made into new products. Some of these recyclables will stay in New Zealand while others will go overseas to the type of facilities that can reprocess them. Glass is the exception because it can’t be baled. It is kept in holding bunkers until it is ready to be taken by truck for reprocessing.

    These resources have been produced by Cognition Education for Visy Industries and Auckland Council.

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