Food Hygiene and Safety Techniques
Senior 1 · Home Science
Food Hygiene and Safety Techniques
Lesson 4 of 5
18 min
Let's begin
Every home produces refuse every day: banana and potato peelings, a broken cup, an empty oil bottle, a torn exercise book, a used battery. Left in a heap behind the house, it feeds flies and rats, old containers collect rainwater where mosquitoes breed, and plastic blocks drains and stays in the soil for many years. Managed well, much of the same refuse becomes compost, animal feed or raw material for new products.
Household refuse is the solid waste thrown away from homes. In this lesson you will learn to sort it into types and to manage it using the waste hierarchy.
| Type | Meaning | Examples from a Rwandan home |
|---|---|---|
| Biodegradable (organic) | Rots naturally, broken down by micro-organisms | Peelings of matoke, potatoes and cassava; leftover food; banana leaves; eggshells; garden waste; plain paper |
| Recyclable | Can be collected and made into new products | Glass bottles and jars, tins and other metal, hard plastic bottles and containers, cardboard |
| Non-biodegradable residual | Does not rot and cannot easily be recycled | Broken plastic toys, crisp packets, rubber sandals, broken ceramics |
| Hazardous | Can poison, burn or injure people, animals or the environment | Batteries, expired medicines, used needles, insecticide and paint containers, old phones and chargers (e-waste), broken energy-saving bulbs |
| Sanitary | Carries germs from the body | Disposable nappies, used sanitary pads |
| Bulky | Too large for a bin | Old mattresses, furniture, broken jerrycans |
Households also produce liquid waste: greywater from washing, used cooking oil, and wastewater from toilets. These are dealt with in the next lesson.
The waste hierarchy puts the ways of dealing with waste in order, from the best choice for the environment to the worst. It is usually drawn as an upside-down pyramid:
Rwanda has acted at the top of the hierarchy: plastic carry bags were banned in 2008, which is why Rwandans shop with paper bags, baskets and cloth bags, and the monthly community work day, umuganda, often includes cleaning streets and clearing drains.
Sorting at the source means separating refuse into types in the home, at the moment it is thrown away, instead of mixing everything in one bin. It matters because mixed waste is dirty and hard to recycle, while sorted waste is clean and easy to use.
Task: The Mutesi family weighs its refuse for one week. The results are: food and garden waste 9.0 kg; paper and card 1.2 kg; plastic 0.9 kg; glass and metal 0.6 kg; other waste 0.3 kg. (a) Find the total. (b) What percentage is biodegradable food and garden waste? (c) Suggest how the family can use the waste hierarchy to cut the amount sent for disposal.
Solution:
(a) Total = 9.0 + 1.2 + 0.9 + 0.6 + 0.3 = 12.0 kg.
(b) Percentage = 9.0 ÷ 12.0 × 100 = 75%.
(c) The biggest part is biodegradable, so the greatest saving is to recover it: compost the peelings and garden waste and feed suitable scraps to animals. Plastic, glass and metal (0.9 + 0.6 = 1.5 kg) can be reused or recycled. Only the 0.3 kg of other waste, plus any paper that cannot be composted or recycled, then needs disposal. That is a cut from 12.0 kg to well under 1 kg a week.
Tip
Memory hook for the hierarchy: "Real Recyclers Rarely Reach the Dump": Reduce, Reuse, Recycle, Recover, Dispose (the dump comes last).
Exam technique: when you classify refuse, ask two questions: Does it rot? (biodegradable or not) and Can it harm? (hazardous or not). An item can be both, for example a used nappy is biodegradable in part but is also sanitary waste that carries germs.
Classify each item: (a) avocado skins; (b) a used torch battery; (c) an empty glass jam jar; (d) a disposable nappy.
Solution: (a) biodegradable; (b) hazardous; (c) recyclable (or reusable); (d) sanitary.
Give one example of each of reduce, reuse and recycle in a home kitchen.
Solution: Reduce: carry a basket to the market instead of taking packaging. Reuse: store beans in a washed glass jar. Recycle: give plastic bottles to a collector.
Why is sorting at the source better than sorting at the dump?
Solution: Sorted waste stays clean, so it can be composted or recycled. At the dump, the materials are mixed and dirty, and sorting them there is slow, unpleasant and unsafe.
A family throws away 20 kg of refuse a week, of which 14 kg is food waste. What percentage is food waste?
Solution: 14 ÷ 20 × 100 = 70%.
Summary
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
