# Using Resources and Sustainability
Humans rely on Earth's resources for everything — building materials, fuels, food, water, and the chemicals that make modern life possible. But many of these resources are finite (will run out). Chemistry plays a crucial role in developing sustainable approaches to resource use. This guide covers resource types, water treatment, life cycle assessments, and key industrial processes.
1. Natural Resources and Products
Types of Resources
| Type | Definition | Examples |
|---|---|---|
| Finite (non-renewable) | Will run out; cannot be replaced in our lifetime | Fossil fuels (coal, oil, gas), metal ores, minerals |
| Renewable | Can be replaced at the same rate as used | Wood, crops, water, wind, solar |
Sustainability
Sustainable development means meeting the needs of the present without compromising the ability of future generations to meet their own needs.
Chemistry contributes through:
- Developing alternative fuels and materials
- Improving recycling processes
- Reducing waste and pollution
- Making processes more energy efficient
2. Water Treatment
Water is essential for life. In the UK, water from rivers, lakes, and reservoirs must be treated to make it safe to drink (potable water).
Potable Water
Potable water is water that is safe to drink. It is NOT pure water (it still contains dissolved minerals), but it has:
- Low levels of dissolved substances
- Sufficiently low levels of microbes (bacteria)
Water Treatment Steps
- Sedimentation — large particles settle out
- Filtration — water passes through sand/gravel beds to remove fine particles
- Chlorination — chlorine is added to kill bacteria and other pathogens
Alternative Methods
- UV treatment — ultraviolet light kills microbes
- Ozone treatment — ozone () kills microbes
Distillation for Pure Water
If very pure water is needed (e.g. for chemical analysis), water can be distilled:
- Heat water until it boils
- Collect and condense the steam
- This removes ALL dissolved substances
- Very energy-intensive (expensive)
Waste Water Treatment
Sewage and industrial waste water must be treated before being released:
- Screening — remove large objects (rags, grit)
- Primary treatment — sedimentation produces sludge and effluent
- Secondary (biological) treatment — aerobic bacteria break down organic matter
- The treated effluent is safe to release into rivers/seas
- Sludge is treated anaerobically → produces biogas (methane) for energy
3. Life Cycle Assessments (LCAs)
A life cycle assessment evaluates the environmental impact of a product throughout its entire life.
Four Stages
- Raw materials — extracting and processing materials
- Manufacturing — making the product; energy used; waste generated
- Use — energy and resources used during the product's life
- Disposal — landfill, recycling, incineration; pollution caused
What Is Assessed?
- Energy consumption at each stage
- Water use
- Greenhouse gas emissions
- Waste produced
- Pollution (air, water, land)
Limitations of LCAs
- Some impacts are hard to quantify (e.g. loss of biodiversity)
- Different LCAs may give different results depending on assumptions and boundaries
- Can be used selectively to support biased claims (greenwashing)
- Data collection can be incomplete
Example: Paper vs Plastic Bags
| Factor | Paper Bag | Plastic Bag |
|---|---|---|
| Raw materials | Trees (renewable) | Oil (finite) |
| Energy to make | High | Lower |
| Reusability | Low (tears easily) | Higher (if reused) |
| Biodegradable? | Yes | No (unless biodegradable type) |
| Recycling | Easier | Possible but limited |
Neither is clearly "better" — it depends on how many times each is used.
4. Reduce, Reuse, Recycle
Why Recycle?
- Conserves finite resources (ores, fossil fuels)
- Saves energy (recycling aluminium uses 95% less energy than extraction)
- Reduces landfill waste
- Reduces pollution and greenhouse gas emissions
Metals
- Metals can be melted down and reformed
- Aluminium and steel recycling saves huge amounts of energy
- Copper can be recycled from old wiring
Polymers (Plastics)
- Mechanical recycling — shredded, melted, remoulded
- Chemical recycling — broken down into monomers (feedstock recycling)
- Challenge: different plastics must be sorted first
- Some plastics produce toxic fumes when burned
Glass
- Can be melted and reformed indefinitely
- Different colours must be separated
- Saves energy and raw materials (sand, soda, limestone)
5. Alternative Methods of Metal Extraction
Phytomining
Using plants to absorb metal compounds from soil:
- Grow plants on low-grade ore or contaminated land
- Plants absorb metal ions through their roots
- Harvest and burn the plants
- The ash contains metal compounds which can be processed
Bioleaching
Using bacteria to extract metals from low-grade ores:
- Bacteria feed on the ore
- Chemical reactions produce a solution containing metal ions (leachate)
- The metal is extracted from the leachate (e.g. by displacement or electrolysis)
Both methods are useful for extracting copper from low-grade ores (ores with a low concentration of metal) and from mine waste.
Advantages
- Less environmentally damaging than traditional mining
- Can extract metals from very low-grade ores
- Less energy needed
Disadvantages
- Very slow compared to traditional methods
- Produces less metal per batch
Worked Example: Water Treatment
Question: Explain why chlorine is added to water during treatment.
Chlorine is added to kill bacteria and other harmful microbes/pathogens in the water. This makes the water safe to drink (potable) by preventing the spread of waterborne diseases.
Worked Example: LCA Comparison
Question: A company compares paper and plastic packaging. State two factors they should consider in their LCA.
They should consider: (1) the energy used in manufacturing each type of packaging, and (2) the disposal method — whether each can be recycled or biodegraded, and the environmental impact of disposal.
Worked Example: Recycling
Question: Explain why recycling aluminium is beneficial.
Recycling aluminium uses 95% less energy than extracting it from bauxite ore by electrolysis. This reduces electricity costs and greenhouse gas emissions. It also conserves finite aluminium ore reserves and reduces the environmental damage from mining.
7. Practice Questions
- Explain the difference between potable water and pure water.
- Describe the three main steps in making water safe to drink.
- What are the four stages of a life cycle assessment?
- Give two limitations of life cycle assessments.
- Explain how bioleaching works to extract copper.
Want to check your answers and get step-by-step solutions?
8. Common Misconceptions
| Misconception | Reality |
|---|---|
| Potable water is pure water | Potable water contains dissolved minerals — it's safe to drink but not chemically pure |
| Recycling uses no energy | Recycling uses energy, but much less than extraction from raw materials |
| All plastics can be easily recycled | Different plastics need sorting; some are difficult or uneconomical to recycle |
| Paper bags are always better than plastic | LCAs show it depends on usage — paper bags have higher manufacturing energy |
9. Exam Tips
- Know the difference between potable and pure water
- For LCA questions, mention all four stages and be balanced in your evaluation
- Recycling questions: mention energy savings, resource conservation, and reduced landfill/pollution
- Phytomining and bioleaching are for low-grade ores — mention this in answers
Summary
- Resources are finite (non-renewable) or renewable
- Potable water is safe to drink; made by sedimentation, filtration, and chlorination
- LCAs assess environmental impact across a product's entire life
- Recycling saves energy, conserves resources, and reduces waste
- Phytomining and bioleaching extract metals from low-grade ores
- Sustainable development balances current needs with future generations' needs