Vegan, vegetarian, omnivore: What does practice tell about the carbon footprint of our diet?

Guest writer:
Réka Szöllősi 
food policy consultant
elelmiszervilag.hu

Conversations have already started in Hungarian professional circles about the need to make our food supply and diet more sustainable. The time has come to think in terms of diets in connection with sustainability. BBC Future has recently conducted its own experiment with a group of voluntary vegan, vegetarian and omnivore consumers and two renowned experts, to see what the carbon footprint of each dietary pattern is for the “average” consumer, based on their two-week food diaries.

The footprint of cooking

A 2020 study from the University of Manchester found: for vegetables in particular, it may be true that more than 60% of their emissions come from home cooking. With pre-baked and pre-cooked products, finishing the preparation at home accounts for around 42% of their emissions. It also matters how we bake and cook, as turning on the oven is clearly the least efficient, and to reduce the environmental footprint of our meals, it is best to opt for more efficient methods such as heating on the stove or in the microwave.

It should also be kept in mind that the proportion of the footprint associated with the preparation of a dish depends very much on the carbon footprint of the ingredients. The higher the latter, the smaller the proportion of the preparation will be in the final figure. To illustrate this with a practical example: if you cook a vegan Bolognese sauce from lentils, you will have a ratio of 80/60 of raw material to cooking, but if you prepare the same dish from beef, you will have a ratio of 4500/60 in carbon dioxide equivalents.

The carbon footprint of cooking largely depends on the carbon footprint of the ingredients

Origin is more important than shipping

Calculations made for the study proved that the distance from which food is transported before consumption makes only little contribution to their full ecological footprint. The only problematic food category in this respect is quickly perishable foods shipped by air, but transporting these is so expensive that it is only done when very necessary, e.g. raspberries, strawberries, peas, etc. This study also revealed that consuming animal-based foods increases the environmental footprint of eating. One of the new findings was the role of portion sizes – it is worth paying attention to these, together with the differences between different product varieties, e.g. more milk is used in making hard cheese than with soft cheese types.

Composting instead of throwing away!

The BBC study also shed light on how big the problem of food waste is. To put it simply: it is essential to prevent food waste, because if we eat the food, its environmental footprint ends there, but if we throw it away, the emission process lasts until the food fully decomposes. It is best if we compost the food that we don’t eat, since the greenhouse gases emitted this way are only 14% of the gases that would be emitted if the food ended up in the bin. It might be surprising, but the environmental footprint of eating in a restaurant isn’t necessarily bigger than that of home eating.

Vegan diet has the smallest footprint

When the three types of diets were compared, it turned out that on a weekly basis vegan diet’s emission level was 9.9 kg CO2e, for the vegetarian diet it was 16.9 kg CO2e, and for the omnivore diet the emission was 48.9 kg CO2e. We can say that this experiment also justified the results of earlier scientific research: a plant-based or mostly plant-based diet generates smaller emissions. According to the study, there are five fundamental principles to follow if we wish to reduce the environmental footprint of our diet:
1. eating less animal-based food;
2. focusing on food type instead of delivery distance;
3. choosing an energy-efficient cooking/baking method;
4. cooking/baking bigger portions;
5. preventing food waste. //