Recycling

When evaluating whether it is viable to recycle materials it is necessary to consider:

  • balancing the use of the raw materials, such as finite resources like crude oil or metal ores, with the need to conserve their supply
  • availability of the material to be recycled
  • economical and practical issues with collecting the material
  • removal of impurities
  • energy use for transport and processing
  • environmental impact of the processes
  • level of demand for the recycled material

Recycling metals

Recycling a metal involves collecting used metal items and producing new metal from them. The steps usually needed are:

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

Advantages of recycling

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.

Question

This 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 metals from one another
  • the sorted metal may need to be transported to where it can be turned into ingots
Question

Describe a simple way to separate aluminium from iron.

A magnet or electromagnet will attract iron but not aluminium.