Unit 11 Waste materials and their effective management
Key unit competence: Apply effective ways to manage waste materials.
Key ideas
- Waste is any material that is no longer useful to its owner and is thrown away. Types: solid (plastics, paper, metal, glass), liquid (sewage, used oil), gaseous (smoke, exhaust), organic/biodegradable (food, leaves) and non-biodegradable (plastics, glass, metals), and hazardous waste (batteries, medical waste, chemicals, e-waste).
- Sources: homes (domestic), schools, markets, hospitals (medical), farms (agricultural), factories (industrial), mines and construction sites.
- School waste: paper, plastic bottles, food leftovers, laboratory chemicals and broken glass. Manage by sorting into labelled bins, composting food waste, recycling paper and bottles and safe disposal of chemicals.
- The waste hierarchy: Reduce (use less), Reuse (use again), Recycle (make into new products), Recover (energy, compost, biogas), and Dispose safely (sanitary landfill) as the last option.
- Hazards of poor waste management: breeding of flies, rats and mosquitoes, diseases (cholera, malaria), blocked drains and floods, polluted soil and water, bad smells, air pollution from burning and harm to animals that eat plastics.
- Rwanda banned non-biodegradable plastic bags in 2008 and holds Umuganda (community work) to clean the environment. Organic waste can be turned into compost or biogas.
Common misconceptions
- "Burning waste makes it disappear safely." No: Burning releases harmful smoke and gases; the pollution moves into the air.
- "All waste is useless." No: Many wastes can be reused, recycled or turned into compost and biogas.
- "Plastics rot quickly in the soil." No: Most plastics are non-biodegradable and remain for hundreds of years.
Worked examples
Example 1. Explain the 3 Rs of waste management with one example each.
Solution
Reduce: use less material, e.g. buy products with less packaging.
Reuse: use an item again, e.g. reuse jars for storage.
Recycle: process waste into new products, e.g. turn plastic bottles into new plastic items.
Example 2. Describe how a school can manage its waste effectively.
Solution
Place labelled bins for organic, paper, plastic and glass waste.
Compost food waste for the school garden.
Sell or give paper and plastic to recycling companies.
Dispose of laboratory chemicals and broken glass safely, and train students through a clean-school club.
Practice questions
Define waste.
Show answer
Any material that is no longer useful to its owner and is discarded.
Common mistake: Saying 'only dirt'.
Give two examples of non-biodegradable waste.
Show answer
Plastics, glass, metal cans (any two).
Common mistake: Naming paper, which is biodegradable.
Name three sources of waste.
Show answer
Homes, schools, markets, hospitals, farms, factories (any three).
Common mistake: Giving types of waste instead of sources.
What is compost?
Show answer
Decomposed organic waste used to fertilise soil.
Common mistake: Saying it is burnt waste.
Give two diseases linked with poor waste management.
Show answer
Cholera, typhoid, malaria, diarrhoea (any two).
Common mistake: Naming non-infectious diseases.
State two benefits of recycling.
Show answer
Saves raw materials and energy; reduces waste in landfills; creates jobs (any two).
Common mistake: Saying it increases waste.
Why should hazardous waste be handled separately?
Show answer
It can poison, burn or infect people and pollute the environment.
Common mistake: Saying it is heavier.
Explain how Rwanda's plastic bag ban helps the environment.
Show answer
Less plastic litter, fewer blocked drains, less harm to animals and soil.
Common mistake: Saying it reduces air pollution only.
Give two ways in which waste can be turned into energy.
Show answer
Biogas from organic waste; burning in controlled incinerators to generate electricity; briquettes from sawdust/charcoal dust (any two).
Common mistake: Saying open burning.
A market produces 2 tonnes of waste per day, of which 70% is organic. Calculate the mass of organic waste per week.
Show answer
0.70 × 2 = 1.4 t per day; 1.4 × 7 = 9.8 t per week.
Common mistake: Forgetting to multiply by 7 days.
Matching and drag-and-drop
Matching
Match each item in column A with the correct answer in column B. Write the letter next to each number.
Column A Column B 1. How should broken glass from a laboratory be disposed of? a. Using both sides of paper and refillable water bottles 2. Which waste should go into a compost pit? b. Vegetable peelings 3. Which practice combines reducing and reusing at school? c. In a labelled, separate container for glass 4. What does 'recycle' mean? d. Process waste into new products Show answer
1 → c (In a labelled, separate container for glass) · 2 → b (Vegetable peelings) · 3 → a (Using both sides of paper and refillable water bottles) · 4 → d (Process waste into new products)
- A separate container protects cleaners and allows recycling.
- Organic waste decomposes into compost.
- Less waste is produced and items are used again.
- For example, old paper is pulped to make new paper.
Drag and drop
Choose the correct word or phrase from the box for each gap. One word in the box is not needed.
recycling · reusing · methane · old phones and computers- Decomposing organic waste can produce biogas, which is mainly .
- E-waste includes .
- Using a shopping basket many times instead of new bags is an example of .
Show answer
1: methane · 2: old phones and computers · 3: reusing
- Bacteria break down waste without air and produce methane.
- Electronic waste contains metals and toxic substances.
- Using the same item again is reuse.
Matching
Match each item in column A with the correct answer in column B. Write the letter next to each number.
Column A Column B 1. A school produces 40 kg of waste per week: 24 kg food, 10 kg paper, 6 kg plastics. What percentage could be composted? a. 60% 2. Which waste is biodegradable? b. Used syringes and bandages 3. Umuganda in Rwanda helps waste management by: c. Banana peels 4. Which waste comes mainly from hospitals? d. community cleaning and environmental work Show answer
1 → a (60%) · 2 → c (Banana peels) · 3 → d (community cleaning and environmental work) · 4 → b (Used syringes and bandages)
- Food waste: 24 ÷ 40 × 100 = 60%.
- Micro-organisms can decompose food waste.
- Citizens clean streets, drains and public places together.
- Medical waste is hazardous and needs special disposal.
Drag and drop
Choose the correct word or phrase from the box for each gap. One word in the box is not needed.
fresh air · flooding during heavy rain · 2008 · flies and rats that spread disease- Plastic waste in drains can cause .
- Heaps of uncollected rubbish encourage .
- Rwanda banned non-biodegradable plastic bags in .
Show answer
1: flooding during heavy rain · 2: flies and rats that spread disease · 3: 2008
- Blocked drains overflow, causing floods.
- Pests breed in rubbish and spread germs.
- The ban helped keep Rwanda clean.