Food Hygiene and Safety Techniques
Senior 1 · Home Science
Food Hygiene and Safety Techniques
Lesson 5 of 5
20 min
Let's begin
Reducing, reusing and recycling shrink the pile of refuse, but something is always left: peelings, broken items, dirty packaging, a used battery. What a family does with that last part decides whether it becomes a useful fertiliser or a source of flies, poisonous smoke and polluted water.
In this lesson you will learn the main methods of disposing of household refuse, how to make compost and a safe refuse pit, why burning refuse is harmful, and how to deal with hazardous and liquid waste.
Composting is the controlled rotting of biodegradable waste by micro-organisms, with air and moisture, to make compost: a dark, crumbly material that feeds the soil. It is the best method for the largest part of household refuse.
A compost heap needs two kinds of material:
Composting works fastest when there is about 25 to 30 times as much carbon as nitrogen, which in practice means mixing plenty of browns with the greens.
Making a compost heap or pit, step by step:
Do not compost: meat, fish, bones, fat and cooking oil, or milk products (they smell and attract rats and dogs); plastic, glass and metal; charcoal ash; faeces of people, dogs or cats; diseased plants.
In towns, refuse is collected, usually for a monthly fee, and taken to a landfill. In a sanitary landfill the waste is spread, pressed down and covered with soil every day, which keeps away flies, rats and birds. Well-built landfills also have a lining and drains to catch leachate (the polluted liquid that seeps out of rotting waste) and pipes to collect the gas. An open dump, where waste is simply piled up, has none of these protections.
Where there is no collection service, waste that cannot be composted or recycled can be buried in a refuse pit:
Burning refuse in the open may look like a quick way to make it disappear, but the smoke contains poisonous gases, including carbon monoxide and dioxins, as well as soot (black carbon) and metals, and some of these also stay in the ash. Burning plastic makes especially thick, black, harmful smoke. Open burning also starts bush fires and adds to climate change. It should be avoided, and plastic should never be burned.
| Waste | Safe disposal |
|---|---|
| Expired or unused medicines | Return them to a pharmacy or health centre; do not throw them in a pit or a toilet |
| Used needles and razor blades | Put them in a hard, closed container and take it to a health centre |
| Batteries, old phones and chargers | Keep them apart and take them to an e-waste collection point; never burn them |
| Used cooking oil | Let it cool, pour it into a closed container and put it with the general refuse; never pour it down a sink or drain, where it sets and blocks the pipe |
| Greywater from washing | Let it drain into a soak pit (a pit filled with stones where water soaks into the ground), or use soap-free rinse water on the garden; do not let it form pools where mosquitoes breed |
Task: A family in a rural area without refuse collection has: (a) sweet potato peelings; (b) a broken plastic basin; (c) expired painkillers; (d) the oil left after frying mandazi; (e) dry maize stalks; (f) a flat torch battery. Choose the best method for each and give a reason.
| Item | Method | Reason |
|---|---|---|
| (a) Peelings | Compost (or feed to animals) | Biodegradable green material, rich in nitrogen |
| (b) Plastic basin | Recycle if a collector takes it; otherwise refuse pit | Does not rot; burning it would release toxic smoke |
| (c) Painkillers | Return to the health centre or pharmacy | Medicines can poison children and animals and pollute water |
| (d) Frying oil | Cool, seal in a container, general refuse | Blocks drains and attracts rats in compost |
| (e) Maize stalks | Compost | Brown material that adds carbon and lets air into the heap |
| (f) Battery | Store apart; take to an e-waste collection point | Hazardous metals leak into soil and water |
Tip
Memory hook for compost: "Greens give nitrogen, browns bring carbon, and air and water keep it working."
Exam technique: for a disposal question, always name the method AND give a reason linked to the type of waste (does it rot? can it harm?). Remember that burning is almost never the best answer.
Classify each as a green or a brown compost material: (a) cabbage leaves; (b) dry banana leaves; (c) goat manure; (d) sawdust.
Solution: (a) green; (b) brown; (c) green; (d) brown.
Why should meat and bones be kept out of a home compost heap?
Solution: They smell as they rot and attract rats and dogs, which dig up the heap and spread germs.
State two differences between a sanitary landfill and an open dump.
Solution: In a sanitary landfill the waste is pressed down and covered with soil every day, and the site has a lining and drains to catch leachate. An open dump has no daily cover and no protection against polluted liquid.
Give two reasons why refuse should not be burned in the open.
Solution: The smoke contains poisonous gases such as carbon monoxide and dioxins, which harm health; burning can start bush fires (or: it adds soot and greenhouse gases to the air).
A compost pit is 1.5 m long, 1 m wide and 1 m deep. What volume can it hold?
Solution: 1.5 × 1 × 1 = 1.5 m³.
Summary
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
