Using Earth's Resources and Sustainability
Natural Resources and Products
Humans use the Earth’s natural resources to provide warmth, shelter, food, and transport. Some resources are finite (non-renewable) — they will eventually run out (e.g. fossil fuels, metal ores). Others are renewable — they can be replaced (e.g. timber, cotton).
Sustainable development means meeting the needs of today’s population without compromising the ability of future generations to meet their needs. Chemistry plays a vital role in sustainable development by finding alternatives to finite resources and reducing waste.
Sustainable development: meet today’s needs without compromising the future. Strategies include using renewable resources, recycling, reducing waste, and developing new materials (e.g. bioplastics).
Potable Water
Potable water is water that is safe to drink. It is not the same as pure water — it contains low levels of dissolved substances. In the UK, potable water is produced from fresh water (rivers, reservoirs) by:
- Sedimentation — the water is left to stand so that fine particles settle out.
- Filtration — the water passes through filter beds of sand and gravel, which trap the solids that are left.
- Sterilisation — adding chlorine, or using UV light or ozone to kill bacteria and make water safe.
In areas with limited fresh water, sea water can be made potable by desalination. Methods include distillation (boiling the water and condensing the steam) and reverse osmosis (forcing water through a membrane that blocks salt). Both methods require significant energy, making them expensive.
UK potable water: fresh water → sedimentation → filtration → sterilisation (chlorine/UV/ozone). Desalination converts sea water but requires a lot of energy. Potable ≠ pure — it still contains some dissolved substances.
Waste Water Treatment
Waste water (sewage and industrial water) must be treated before release into the environment. The process includes:
Screening: large objects (rags, sticks) are removed by passing water through screens.
Sedimentation: solids settle out as sludge. The liquid effluent is separated.
Biological treatment: aerobic bacteria break down organic matter in the effluent. The sludge is also digested anaerobically by bacteria, producing biogas (methane) which can be used as fuel.
Final treatment: the cleaned water is tested and released back into rivers or the sea.
Life Cycle Assessments and Recycling
A life cycle assessment (LCA) evaluates the environmental impact of a product at every stage: extracting raw materials, manufacturing and packaging, use, and disposal (landfill, recycling, or incineration). LCAs help companies make products more sustainable.
Reducing, reusing and recycling materials conserves finite resources, reduces energy consumption, and decreases the amount of waste going to landfill. However, recycling has its own costs (collection, sorting, processing energy) and LCAs can be subjective.