Learn about the super science behind the separation of the contents of your mixed recycling bin!
The contents of the mixed recycling bin have to be separated before being sent on to be reprocessed into new products. The separation process takes place at the Materials Recovery Facility (Commonly known as “ The MRF”) which is in South Manchester.
The MRF uses technology to separate each of the groups of items by material type.
Have a go at our Sorted by Science activity to help explain how the MRF uses clever science to separate the mixed recycling.
This activity introduces how materials are sorted in the MRF using their properties. It is a good activity for your STEM curriculum topics.
Give or display the following selected items to each group:
Steel can
Aluminium can
Plastic bottle PET (Clear)
Plastic Bottle HDPE (opaque)
Glass jar
Foil
Display the clue sheets on the whiteboard or wall:
• Magnet
• Hammer
• Sieve
• Bellows/bike pump
• Torch
Encourage the group to think about the materials and properties of each item:
• Light or heavy
• Transparent or opaque
• Breakable
• Magnetic
Ask the group to discuss how the items in the bag could be separated mechanically. The clues should prompt some ideas.
The aim at this stage is to keep it simple and allow creative problem solving ideas. It would be unlikely that they would know how to separate aluminium.
To sum up – The MRF does have a series of machines to carry out each method of separation.
Watch our Education officer explaining the answer in the video opposite.
Firstly, the recycling is tipped onto a conveyor belt. This passes through a hand sorting cabin where workers try to remove large, wrong items that might break the MRF machinery.
Then the recycling passes under a magnet. The steel food cans are magnetic due to the iron content of the steel, so they are attracted up towards the magnet. A rotating belt sweeps the cans sideways into a container.
Next the recycling drops into the Glass breaker machine. Rotating rollers break the glass up into smaller pieces which drop down through holes onto a different conveyor underneath.
A machine called an Eddy Current Separator next removes the aluminium cans using technology similar to repelling magnetism. In a way, the cans get charged up and repelled off the conveyor belt.
Finally the two types of plastic bottles are separated by infra red lasers called Aladdin! The first Aladdin laser detects the opaque or coloured bottles and a powerful air jet blows it onto a different conveyor. A second Aladdin detects the clear or transparent bottles and directs them with the air jet onto another belt.
These machines work on the material and properties, they do not know if it is a wrong item such as a steel handlebar, pottery mug that smashes, aluminium saucepan, clear plastic strawberry punnet, opaque plastic food tray, so items like these will contaminate the recycling streams and may reduce the price.
We need to encourage people to not put wrong items in the bin in the first place.
Watch the film opposite to see what happens when you put wrong items in the mixed recycling bin.
Set a challenge for your group to find online films to show exactly how each item is reprocessed into new products and materials. The video opposite shows how cans are recycled.
Individuals will be able to explain how their mixed recycling is separated and the implications of putting wrong items into the bin.
