Recycling is a process by which the materials of which a product is made up at the end of its life cycle (generally industrial or household waste) may be reused in part or in whole. They are thus subjected to their original production cycle.
Different kinds of recycling
Recovery of raw materials
If a product is essentially made up of one or several raw materials that can be easily separated or reused, it can be recycled. For example:
glass bottles can be melted to make new ones;
once sorted, paper and cardboard products (newspapers and magazines,…) can be recycled to make similar products;
worn tyres can be used to make flower pots, trestles, sound-proofing panels, floor covering materials, rubber asphalt…
any aluminium collected can be used to manufacture cans, packaging paper, car parts (cylinder heads, wheel rims, gear boxes), etc;
any steel collected can be used to produce cans motor parts, tools, tins…
any plastics collected can be used to produce plastic bags, recipients and lids for products other than food, garden furniture, clothes, toys, street furniture, fences and pipes, car parts (bumpers, batteries, etc), road sign supports, cone markers…
- water is also treated in purification plants so that it can be re-used:
By recycling materials, we curtail the need to extract raw materials:
- Recycled steel saves iron ore.
- Every tonne of recycled plastic saves 700 kg of crude oil.
- Recycling 1 tonne of aluminium saves approximately 8 kg of bauxite, 4 kg of chemical products and 14 kilowatts/hour of electricity.
- Every tonne of cardboard recycled saves 2.5 tonnes of wood.
- Every sheet of paper recycled saves 1 litre of water and 2.5 Wh of electricity and 15 g of wood.
In theory, all materials are recyclable. In practise, the lack of a profitable field of activity means not all of them are recycled. It is for this reason that recycling proves to be a more costly process for electrical goods such as computers, as the many components need to be separated before they may be recycled to make different products.
Within the European Union, legislators of electrical and electronic goods require the latter to be recovered and recycled.
Converting one product into another
In some cases (with fermentable materials in particular), products cannot be recycled in their initial form or in the form of a raw material. These may nonetheless be reused once composted or fermented to make fertiliser and/or fuel (mainly natural gas or biogas). This is called recovery.
When it is not possible to recycle a product by any of the aforementioned processes, if the product is able to produce energy by combustion, it can be burnt to recover this energy: This is known as incineration of refuse. This is not, however, a recycling process in itself. It is “energy recovery”, as opposed to “material recovery”.
Another technique can be used for organic household waste (food waste, sewage sludge, etc.), which involves transforming these materials into a biogas that produces combustible and transportable gases: Methane.