9.7 - Reuse & Recycling

Why we reduce, reuse and recycle

• Most manufactured goods come from raw materials taken from the Earth, which are in limited supply (finite), such as metal ores.
• Extracting raw materials is damaging and expensive:
  • Uses large amounts of energy to extract and process them, mostly from burning fossil fuels.
  • Damages the environment through quarrying and mining, which scar the landscape, destroy habitats, and produce waste.

Three ways to conserve raw materials

1. Reducing - Using less of a material in the first place, saving raw resources, energy, and environmental damage.
2. Reusing - Using a product again in its current form, requiring far less energy than recycling because it isn't broken down or reprocessed.
3. Recycling - Breaking down a used product into its raw material to make something new.

All three approaches conserve finite resources, save energy, and reduce waste sent to landfill.

The economic case

• Processes that use less energy cost less to run, especially for materials that are expensive to extract.
• Recycling is an industry that creates jobs in collecting, sorting, and reprocessing waste.
• Recycling isn't always worth doing: the cost of collecting and reprocessing must be weighed against the cost of making the material from scratch.

Recycling metals, and reusing glass

• Extracting metals from ores requires large amounts of energy and causes environmental damage.
• Recycling metals avoids most of this:
  • Uses a fraction of the energy needed for extraction.
  • Conserves limited supplies of ores.
  • Cuts down on waste sent to landfill.

How metals are recycled

1. Sort the scrap metal.
   • The sorting required depends on the product: items requiring a pure metal must be carefully separated, while others can use a mixture.
2. Melt it down.
   • Scrap steel can be added directly to the molten iron from a blast furnace, reducing the amount of iron that needs extracting from iron ore.
3. Cast or reform it into new products.

Aluminium

• Extracting aluminium requires mining about 4 tonnes of ore for every tonne of metal, followed by electrolysis using large amounts of electricity.
• Recycling aluminium uses only about 5% of that energy, saving roughly 95% of the energy, four kilograms of ore per kilogram of metal, and substantial waste.
• This makes aluminium one of the most cost-effective metals to recycle.

Glass - Reused or recycled

• Reuse - Glass bottles can be collected, washed, and refilled without being melted down, using almost no energy.
• Recycling - Glass that can't be reused is:
  • Separated by colour and type.
  • Crushed and melted to be remoulded into new bottles, jars, or glass wool for insulation.

The problem with plastic waste

• Addition polymers are chemically unreactive and cannot be broken down by microbes; they are non-biodegradable.
• Because they don't rot, discarded plastics persist in the environment for centuries, creating over two million tonnes of plastic waste each year in the UK alone.

Three main problems

1. Landfill - Large volumes of plastic are buried because mixed plastics are difficult and expensive to separate. They occupy valuable space indefinitely.
2. Accumulation in oceans - Plastic litter washed into rivers and seas accumulates, harming marine ecosystems and wildlife.
3. Toxic gases from burning - Burning plastics releases useful energy, but produces harmful emissions:
   • Plastics containing chlorine, such as PVC, release hydrogen chloride gas, which must be removed from the exhaust gases.
   • Complete combustion produces carbon dioxide, a greenhouse gas that contributes to global warming.

Recycling plastics, and whether it is worth it

• Plastics are made from crude oil, a finite resource that is becoming increasingly scarce and expensive.
• Recycling plastics conserves crude oil for uses where no substitutes exist.

Why recycling plastics is difficult

• Different polymers must be separated by type before melting and remoulding.
• Sorting is labour-intensive and expensive; if unsorted plastics are melted together, the resulting material has poor properties.
• Plastics can only be recycled a limited number of times, as the polymer chains degrade and lose strength each time they're melted.

Advantages and disadvantages of recycling plastics