How is the Carbon Footprint of Recipes Calculated?

The estimated carbon footprint of each recipe (all recipes here) is an important part of “Climate-Friendly Cooking”. You want to understand how this estimate is calculated? No problem, this article should help you! 📏

One thing up front: It is important to emphasize that the footprint is an estimate. The exact carbon footprint depends on many factors, from the use of fertilizer in growing vegetables to the energy efficiency of your cooking pot. It is simply not possible to map all of this exactly. The main goal is to get the order of magnitude right and to enable comparisons.

Many of the recipes here on the blog are designed for two servings. This has proven to be practical: if you live as a couple, you have a full meal. If you live alone, you have a warm-up or take-away portion. For additional people, you can easily adjust the quantities upwards.

The estimated carbon footprint mainly refers to the emissions generated by the ingredients and the preparation. In the following sections, I will go into each of these parts in a little more detail. At the end, there is an overview of what is not included in this estimate.

Photo by Neon Brand

The carbon footprint of ingredients

To calculate the carbon footprint of the individual ingredients, I use an overview with data on CO₂ equivalents from publicly available scientific studies. These are usually determined in the form of so-called life cycle assessments and refer to the emissions that arise from production to sale at the shop counter.

We have collected an overview of life cycle analyses of food ingredients. These are sometimes available in different varieties - for example, conventionally grown lentils compared to organic lentils or outdoor tomatoes compared to greenhouse tomatoes.

The list is extensive, but not complete: For example, I have not yet found a study that compares the carbon footprint of basil with thyme. In such cases, I use estimates for higher-level categories such as “herbs and spices”, which also come from these studies. This is particularly the case for ingredients that are only used in relatively small quantities: even if there is a very large difference between basil and thyme, this is unlikely to make a real difference to the carbon footprint of the recipe.

Life cycle assessments estimate a certain amount of emissions for each food, but in fact this value also depends on how the food was produced (source). For the calculation, I therefore assume a typical carbon value, but of course there is a fluctuation around this value. In addition, I sometimes have to combine data from several different sources for a recipe, whereby the methodological approaches of these studies differ slightly. This also leads to a further source of inaccuracy.

The carbon footprint from the overview always refers to one kilogram of this ingredient. In the next step, I convert this to the quantities actually used in the recipe.

Other projects do not use specific quantities of ingredients for a recipe, but rather proportions of ingredients in a typical diet or in the daily calorie requirement (e.g. Poore and Nemecek 2018 or “All You Can Eat” by Greenpeace Switzerland and Eaternity). This approach is helpful when the focus is on a total carbon footprint for a longer period of time. Here on the blog, however, it’s about individual recipes that you can incorporate into your everyday diet. It therefore makes more sense for us here to concentrate on each individual recipe and the ingredient quantities required for it.

Photo by Conscious Design

The carbon footprint of preparation

Unfortunately, the study situation for the emissions generated during the preparation of the recipes is not quite as good as for the ingredients: I mainly use a study from Switzerland that deals with the electricity consumption of various cooking and baking methods (source).

I have created a small calculator from the data in this study to be more flexible: For example, a pizza is baked in the study and the electricity consumption for preheating the oven and the actual baking is measured. I have broken this down into its components and can therefore also estimate the effect of a different baking time. You can find the table with the calculations here.

The study itself is based on a specific stove and oven model: it is the Electrolux SB7 stove with a ceramic hob and an oven capacity of 70l. In individual cases, this will probably be different for you. If you happen to know of other scientific papers on this topic, please let me know at kontakt@klimafreundlicher-kochen.de.

To get from electricity consumption to the carbon footprint, I use this with the carbon emission factor in the German electricity mix, which the Federal Environment Agency estimated at 366g carbon per kilowatt hour for 2020 (source).

What is not included in the carbon footprint?

The focus for the carbon footprint is on the ingredients and their preparation. In principle, there are a few other sources of carbon emissions from our diet that I cannot consider here:

• your way to the supermarket: It makes a difference which means of transport you use to get to the store - but in individual cases it also depends on how often and how much you buy. It is very difficult to map this in general. (I personally walk to the store.)
• Storage of food: You will probably store some things in the refrigerator and some in a kitchen cupboard. However, distributing the annual consumption of your refrigerator among the individual foods is complicated: it depends on the one hand on how big and how full your refrigerator is, and on the other hand on how long you store a food in the refrigerator.
• your kitchen appliances, your cooking utensils, your dishes and cutlery: These are all consumer goods that are often used for a very long time. Even if you can estimate the carbon emissions for the construction of a stove, it is complicated to apply this to every single cooking process (especially with a useful life of more than 10 years).
• your visit to this website: The use of the Internet also has a certain carbon footprint. Specifically, it is only a few grams here.

Summary

The carbon footprint of the recipes here on the blog provides an approximation, but is certainly not perfect. I try to cover the consumption components for ingredients and preparation. Here I hope to be roughly correct on average and to show a typical carbon footprint for this recipe. In individual cases, however, this will certainly not be accurate to the gram. I hope these explanations were helpful for you to understand what is behind the carbon footprint for each recipe here on the blog.

Would you like to see all the recipes? This way! 🥑

Or are you looking for the recipes sorted by their estimated carbon footprint? You can find them here! 🍳

Do you have any specific suggestions and data that could be used to improve this estimate? Feel free to send me an email at hello@climate-friendly-cooking.com.