Recycling

Recycling involves collecting used materials, such as metal, glass or paper and using them to produce new samples of the material. The steps usually needed are:

  • collecting used items
  • transporting the used items to a recycling centre
  • breaking up the items and sorting the different materials

The next steps will depend on the material being recycled. For a metal, the following steps would be carried out:

  • melting the metal and removing impurities from the molten metal
  • solidifying the metal in ingots (slabs of metal)

The ingots can then be used to manufacture new metal items.

Glass is recycled by melting the objects being recycled. The molten glass can then be used to make new bottles or other objects.

Paper is recycled in a different way, as it cannot be melted. Instead, it is broken into smaller pieces, with water. The slurry of water and paper can now be reformed to make new sheets of paper.

Advantages of recycling metals

The advantages of recycling compared to producing metals from metal ore include:

  • fewer quarries and mines are needed
  • less noise, dust and heavy traffic are produced
  • smaller areas of natural habitats are damaged
  • metal ores are conserved so will last longer

In addition, less energy is usually needed to produce a metal by recycling than is needed to produce it from an ore.

For glass and paper, the amount of energy needed to recycle the materials is less than the energy that would be needed to make them from their raw materials. For glass and paper, the energy saving is smaller than for metals. This is because metal extractions need a lot of energy through electrolysis or carbon reduction.

Question

The table shows the percentage of energy saved by recycling compared to extraction from a metal ore.

MetalEnergy saved
Iron70%
Aluminium92%

Suggest an explanation for the difference.

Aluminium is extracted from its ore using electrolysis but iron is extracted by heating with carbon. Electrolysis uses more energy, so more energy is used to extract aluminium in the first place. Aluminium has a lower melting point than iron, so less energy is needed to melt it during recycling.

Disadvantages of recycling

Disadvantages of recycling arise from the recycling process itself:

  • the collection and transport of used items needs organisation, workers, vehicles and fuel
  • it can be difficult to sort different materials from one another
  • the sorted materials may need to be transported to where they can be processed

Other disadvantages relate to the materials themselves:

  • many metallic objects are made from alloys, which cannot be separated
  • some metals are difficult to separate from each other
  • recycled paper is often low quality and has limited uses, eg lavatory paper
  • paper can only recycled a small number of times before the fibres break down and the paper is too weak to use
Question

Describe a simple way to separate aluminium from iron.

A magnet or electromagnet will attract iron but not aluminium.

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