Teaching overview

Learning points

  • Most food waste is dumped in landfill sites, where it rots and produces a greenhouse gas called methane.
  • In order to tackle this problem, the South Korean capital city of Seoul has introduced strict laws that require people to pay for any food waste they throw away.
  • In the US, San Francisco and Seattle now also require residents to keep their food waste separate from other types of rubbish – so it can be composted, for example.

Curriculum keywords

  • Recycling
  • Climate change
  • Waste management
  • STEM

Multimedia toolbox

Food waste video loop

Play the video loop as students come in and sit down to spark a discussion about what they think happens to leftover food.

Biogas visual

Display the visual after the film to prompt a discussion on how biogas is made. What are the advantages and disadvantages of biogas as an energy source?

Decomposed organic matter used to help fertilise plants.


Show the visual after the film to reinforce scientific terminology.

Consumption vs waste visual

Display this visual after the video and ask students why they think some types of food are more easily wasted than others. Could we reduce different types of food waste?

Spark a discussion

  • What happens to food waste that is not recycled?
  • Why do people in Seoul produce less food waste than people in the US?
  • What kinds of rules and regulations did different cities in the US introduce to waste less food?
  • How much food waste do you think you produce every day? What about your entire family?
  • What are some ways you can reduce how much food waste is produced from your home and school? Would it be difficult to make those changes?
  • Are meat-based leftovers suitable for a homemade compost heap? Why or why not?
  • What effect do you think it would have on the environment if we didn’t recycle any food waste?
  • Rotting food produces methane, a greenhouse gas. Why is methane bad for the environment?
  • What is biogas, and how is it made?
  • Can you come up with more ways of recycling or reusing food waste?


Wonky salad

MAKE a wonky vegetable salad with your students to show that food doesn’t have to look perfect to be delicious!

Open detailed instructions

Other activity ideas

  • CREATE an informational poster showing people the environmental effects of not recycling large amounts of food waste.
  • RECORD as a class how much food waste students and their families produce at home.
  • DRAW an annotated diagram showing the process of food waste recycling implemented in Seoul, South Korea.
  • DEBATE what supermarkets should do with the food that they don’t sell. Are there any alternatives to landfill?
  • DESIGN a local campaign for your neighbourhood encouraging people to reduce the amount of food they waste and recycle the food waste that they do produce.
Print this sheet

Wonky salad

Duration: 45 minutes


  • Large salad bowl
  • Bowl for food peelings
  • Wonky salad ingredients (sourced by students)
  • 4 small bowls
  • 4 forks
  • Peeler
  • Paring knife
  • Chopping board
  • Access to fresh water
  • Wooden spoon
  • Grater (optional)

Key Learning:

This activity will help students understand that food can be perfectly edible even if it doesn’t look cosmetically perfect. They will also understand that buying less attractive fruits and vegetables will help to reduce the amount of food that ends up in landfill.


Activity preparation: Around a week or so before the lesson, tell students that they are going to be making a wonky salad with ingredients that they source. You may wish to write a short note home to their parents or guardians requesting that, if possible, students join them for a trip to the supermarket. Ask them to pick out some cosmetically unattractive but otherwise edible fruit or vegetables to bring in to class. Set a date for the wonky salad.

Activity instructions:

  1. A week before the wonky salad date, explain to students that they are going to be making a salad in class. Ask them to think about food items that they would like to put in this salad and write these up on the whiteboard. Guide suggestions away from foods that have to be cooked, such as eggs or potatoes, and towards fresh foods that can be eaten raw, such as cucumbers, tomatoes, red onions, herbs, carrots, lettuce, avocados, spring onions, radishes or lemons (for a simple dressing). You could also research which fruits and vegetables are in season, and try to include more of these.
  2. Tell students that you would like them to think about these ingredients when they choose what to buy at the supermarket. Emphasise that they should look for food that isn’t perfect. Ask them to look out for an undersized or wonky carrot, a tomato with imperfections on its skin, or a puckered and lumpy lemon. Clarify that they should never choose food that has mould on it – just food that is considered ugly.
  3. A week later, when students bring in their fruit and vegetables, set everything on a table at the front of the classroom and ask the following discussion questions:
    • Why do you think that this food hadn’t been chosen by anyone else at the supermarket?
    • Do you think it will taste as good as “normal” fruit and vegetables?
    • What happens to the food that nobody buys at the supermarket?
    • Can you think of a better use for wasted food than landfill?
  4. If they didn’t already, do you think that the person who bought this food for you will buy wonky fruit or vegetables in the future?
  5. Divide students into groups of 4 and distribute the wonky fruit and vegetables among each group. Remind students to wash their food before they begin preparing it. 
  6. Ask students to prepare their food the way they like to eat it. For example, they could peel their carrots, or leave the skins on. They could cut their carrots into discs or long thin sticks – or they could grate them. Encourage creativity! Explain that they should add each ingredient to the large salad bowl. Peelings and inedible parts should go in a separate bowl, to keep everything tidy.
  7. Once a group has added all of its prepared salad ingredients to the salad bowl, ask one student to stir it all up with the wooden spoon and then serve it into the four smaller bowls. If one of the students brought in a lemon, demonstrate how it can be squeezed over the salad as a tasty, easy dressing.
  8. Tuck in! 

Background information

  • Across the world, roughly one third of all food produced is wasted. This has a cost of about $1 trillion / £760 billion per year.
  • The United Kingdom is throwing away £13 billion worth of food each year, with thousands of tons coming from supermarkets that have overstocked their shelves. Supermarkets often focus on buying and selling fruit and vegetables that look attractive, forcing farmers to throw away edible produce that looks wonky or that doesn’t fit size specifications. This is especially problematic given that 12% of people in the UK struggle to afford meals.
  • Methane is a harmful gas produced by farm animals, fossil fuel extraction and landfill sites. It’s a greenhouse gas, which means it’s harmful for the environment – it travels into Earth’s atmosphere and traps heat, contributing to global warming. Methane doesn’t stay in the atmosphere for as long as carbon dioxide, but it is more dangerous as it absorbs heat far more quickly. Humans have steadily been producing more methane every year since 2007.
  • The South Korean government came up with a selection of effective policies to reduce domestic food waste. Separate bins for food were introduced, and each household was charged an amount of money dependent on the weight of their food waste. Food waste was banned from landfills and made into compost, biogas or animal feed instead. Restaurants were also encouraged to decrease the number of small dishes as they tend to produce more waste during food preparation. In 1995, only 2% of food waste in South Korea was recycled, compared to a staggering 95% in 2009.
  • Biogas is a type of biofuel made naturally from decomposition of organic matter. It is an environmentally friendly resource, as it doesn’t rely on non-renewable fossil fuels, and uses the natural processes of organic matter to produce energy. Biogas doesn’t produce any harmful substances into the environment, as it converts the methane produced by rotting organic matter into a much safer carbon dioxide.
  • Home composts are an easy way to turn food waste into natural fertiliser for a garden. A composting bin should be set on soil on a flat surface to allow insects, worms and microbes access to the decomposing waste. Most fruits, vegetables, coffee grounds, flowers, weeds, grass, nettles, eggs, cardboard, and straw are amongst many items you can put in a composting bin as they all rot quickly and make a compost full of nutrients. You shouldn’t include items such as food packaging, meat and fish leftovers, bones, dog food, cat litter or dairy products. Paper, cans and other non-organic man-made materials won’t decompose properly and might add toxins to your compost, while the smell of rotting meat and dairy will attract parasites, rats and raccoons. The addition of meat to a compost bin also slows down the composting process. While this means that meat and dairy aren’t ideal home-compostible materials, they can still be put into government-collected food bins for recycling away from urban areas.


Greenhouse gases
Gases in Earth's atmosphere that trap heat close to the planet's surface.
Decomposed organic matter used to help fertilise plants.
A type of fuel made from discarded organic matter.

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