Recycling

Metals, glass, building materials, clay ceramics and most plastics are made from limited natural resources. Some items made from these materials can be reused. This saves the most energy and reduces the impact on the environment. For example, glass bottles only need to be washed and sterilised before they can be filled again. Other products cannot be reused in this way but they can be recycled.

Advantages of recycling

The advantages of recycling compared to producing materials and objects from natural resources include:

  • fewer quarries and mines are needed to extract finite reserves of metal ores
  • less crude oil needs to be extracted from the crust as a raw material for making plastics
  • less energy is needed for recycling compared with making a new product from natural resources, so the emission of greenhouse gases is reduced
  • the amount of waste that is disposed of in landfill is reduced

Worked example

Question

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

Metal Energy 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 melted and cooled to form new products

The amount of sorting required depends on the purity of the mixture of metals/materials, and also on how pure the final recycled metal needs to be. For example, copper for electrical wiring requires a very high purity, so if wiring is made from recycled copper, the waste copper will need processing before being melted again into copper for wiring.

However, steel used in construction doesn't need such a high purity. This means that scrap iron can easily be added to the steel furnace when steel is being made. This reduces the cost of making steel from iron ore.

Question

Describe a simple way to separate aluminium from iron.

A magnet or electromagnet will attract iron but not aluminium.