Recycling
Metals, glass, building materials, clay ceramics and most plastics are made from limited natural resourcesMinerals that have been made through the formation of the world that can be used for human benefit.. Some items made from these materials can be reused. This saves the most energyThe capacity of a system to do work or the quantity required for mechanical work to take place. Measured in joules (J). For example, a man transfers 100 J of energy when moving a wheelbarrow. and reduces the impact on the environmentThe immediate surroundings in which people live, or the natural world such as the land, air or water.. 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 recyclingReusing materials or reprocessing waste materials to produce new materials..
Advantages of recycling
The advantages of recycling compared to producing materials and objects from natural resources include:
- fewer quarryAn area of land that is used to remove rocks for use in industries. and mines are needed to extract finite reserves of metal ores
- less crude oilMixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms. 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 gasThe gases responsible for global warming - carbon dioxide, methane, nitrous oxide and CFCs (chlorofluorocarbons). is reduced
- the amount of waste that is disposed of in landfill sitesPlaces where refuse is buried underground. is reduced
Worked example
Question
The table shows the percentage of energy saved by recycling compared to extractionThe process of obtaining a metal from a mineral, usually by reduction or electrolysis. from a metal ore.
| Metal | Energy saved (%) |
| Iron | 70 |
| Aluminium | 92 |
| Metal | Iron |
|---|---|
| Energy saved (%) | 70 |
| Metal | Aluminium |
|---|---|
| Energy saved (%) | 92 |
Suggest an explanation for the difference.
Aluminium is extracted from its ore using electrolysisThe decomposition (breakdown) of a compound using an electric current. 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 electromagnetA magnet made by wrapping a coil of wire around an iron bar and passing an electric current through the coil. will attract iron but not aluminium.