Using Earth’s resources

We use the Earth's resources for warmth, shelter, food, transport and materials. Some, such as crude oil and metal ores, are finite and will run out; others, such as wood and cotton, are renewable. Chemistry helps us use resources sustainably: making water safe to drink, comparing products with life cycle assessments, and reducing, reusing and recycling.

Key facts

  • Finite resources (crude oil, natural gas, coal, metal ores) cannot be replaced as fast as they are used. Renewable resources (wood, cotton, wool, food crops) can be grown again.
  • Sustainable development meets the needs of people today without harming the ability of future generations to meet theirs.
  • Potable water is safe to drink. It is not pure: it contains small amounts of dissolved substances.
  • Fresh water is made safe by passing it through wire meshes, filtering it through sand and gravel beds, then sterilising it with chlorine, ozone or ultraviolet light.
  • Sea water can be made drinkable by distillation or reverse osmosis (desalination), but this needs a lot of energy.
  • A life cycle assessment (LCA) looks at a product's effect on the environment at each stage: raw materials, manufacture, use and disposal.
  • Reducing, reusing and recycling saves finite resources and energy and cuts waste. Metals and glass are recycled by melting them and making new products.

Worked examples

Example 1

Describe how water from a reservoir is made safe to drink.

  1. Wire meshes remove large objects such as twigs and leaves.
  2. Filter beds of sand and gravel remove small solid particles.
  3. Sterilising with chlorine, ozone or ultraviolet light kills microbes. The water is now potable.

Answer: screen it with wire meshes, filter it through sand and gravel, then sterilise it with chlorine, ozone or ultraviolet light

Example 2

Use these LCA energy figures (MJ) to decide which bag uses less energy: paper bag: raw materials 5, making 4, use 0, disposal 1; plastic bag: raw materials 3, making 2, use 0, disposal 2.

  1. Paper bag. 5 + 4 + 0 + 1 = 10 MJ
  2. Plastic bag. 3 + 2 + 0 + 2 = 7 MJ
  3. The plastic bag uses less energy, but an LCA also counts other things: plastic is made from crude oil (finite) and lasts a long time as litter, while paper comes from trees (renewable) and rots.

Answer: the plastic bag (7 MJ against 10 MJ)

Example 3

Why is recycling aluminium cans better than extracting new aluminium?

  1. Extracting aluminium needs mining the ore and lots of electricity for electrolysis.
  2. Recycling only needs the cans to be collected, sorted, melted and made into new cans.
  3. So recycling saves energy, saves the finite ore and keeps waste out of landfill.

Answer: it uses much less energy, saves the finite ore and reduces waste