The results
So, how did we do?
A few weeks after our experiment, BBC Future attends a grand unveiling over Zoom, during which our total emissions during the experiment are revealed.
- Vegan CO2e emissions per week: 9.9kg
- Vegetarian CO2e emissions per week: 16.9kg
- Omnivore CO2e emissions per week: 48.9kg
What do these figures this translate to in everyday terms? US Environmental Protection Agency's equivalencies calculator, provides some useful comparisons:
- Vegan, 9.9kg (21.8lbs): 24.6 miles (39.6km) driven in a petrol-powered car, or 1,204 smartphones charged
- Vegetarian, 16.9kg (37.3lbs): 41.9 miles (67.4km) driven in a petrol-powered car, or 2,056 smartphones charged
- Omnivore, 48.9kg (107.8lbs): 121 miles (194.7km) driven in a petrol-powered car, or 5,948 smartphones charged
As expected, our vegan scored the lowest emissions, coming in at less than two-thirds the emissions of our vegetarian and just one-fifth that of the omnivore's emissions.
If it were a competition, our vegan would certainly be the winner.
But the result is not quite as clear cut as we had imagined. It turns out that on some days, vegetarianism came out as the diet with fewer emissions:
- Vegan day: Toasted crumpets with beans, followed with a lunch of mashed potato and salad, rounded off with yoghurt and most of a bag of fennel taralli snacks: 1.9kg (4.2lbs) CO2e – or 231 smartphones charged
- Vegetarian day: A bowl of porridge with a splash of milk, an apple, a banana, a bowl of carrot and coriander soup with bread and butter, a bar of milk chocolate and a dinner of spinach and ricotta tortellini: 1.7kg (3.7lbs) CO2e – or 207 smartphones charged
It seems that having the lowest carbon footprint as a vegan isn't guaranteed – it depends on what you eat. What is clear from our experiment (and more importantly, from rigorous scientific research) is that on average a plant-based diet has significantly fewer emissions. Eating large amounts of meat, especially beef, is a sure way to increase your emissions many times over.
The tweaks to our diets that would result in the greatest fall in emissions were:
- Reducing animal products – eating fewer of them, or replacing with a plant-based alternative
- Focusing on what you eat rather than food miles
- Cooking efficiently, and saving ovens for special occasions rather than everyday use
- Batch cooking to prepare food using a fraction of the energy
- Avoiding food waste, through careful planning and creative cooking