What it shows
Food thrown away takes land, water and energy to produce, and it makes methane when it rots in a landfill. Weighing waste every day shows how much is wasted and where it comes from.
The science
Waste that was edible, such as leftover rice or a whole fruit, is avoidable, while peels, bones and tea leaves are unavoidable. When food waste decomposes without air in a landfill it gives methane, a greenhouse gas about 28 times stronger than CO2 over 100 years. Composting with air gives mostly CO2 and a useful manure. Saving food also saves the water, fertiliser and fuel used to grow and transport it. Counting and graphing the waste is the first step to cutting it.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A kitchen scale reading to 5 g
- Two plastic buckets with lids and labels (avoidable and unavoidable waste)
- Disposable gloves
- A notebook or spreadsheet
- A hand wash soap
- A permission note from the cook or canteen
- Chart paper
Safety
For this project: Wear gloves, wash hands with soap after weighing and keep the buckets lidded. Do not eat or sort food waste with bare hands. Take permission from your family or canteen staff.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Agree with your family or the canteen to measure waste for 14 days at the same meal times.
Weigh the empty bucket and write its mass. After each meal put the leftovers into the correct bucket, avoidable or unavoidable, and weigh it.
Subtract the empty bucket mass to find the waste of each meal and write it in a table with the date and meal.
Note why the food was wasted: cooked too much, did not like it, spoiled, or extra serving.
Plot a bar chart of the total waste for each day and a pie chart of the reasons.
Work out the average waste per person per day and multiply by 365 to find the yearly waste.
Choose the biggest cause and try one change for a week, such as smaller first servings, and measure again.
Compare the first week and the changed week, and calculate the percentage of waste saved.
What you should see
A chart showing the daily mass of food waste, a list of the main reasons, and a measured reduction after one change, for example 20 to 30 per cent less.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is avoidable food waste?
Edible food that was thrown away, such as leftover rice or bread.
2Why does food waste in a landfill harm the climate?
It rots without air and makes methane, a strong greenhouse gas.
3Why is composting better?
With air it gives mostly CO2 and a useful manure, with much less methane.
4How can a canteen reduce waste?
By offering smaller portions with free second helpings and planning meals from the number of students.
Take it further
Start a compost pit with the unavoidable waste and track the temperature and the volume as it turns into manure.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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Your Science Exhibition Guide
Choose a project, build it, present it and answer the judges with confidence
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Investigatory Projects for Class 11 and 12
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