How is the carbon footprint of recipes calculated?
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The estimated carbon footprint of each recipe (all recipes here) is an important part of “Climate-Friendly Cooking”. Want to understand how this estimate is calculated? No problem, this article will help you! 📏
It’s important to note that the footprint is an estimate and depends on various factors, such as the amount of fertiliser used to grow vegetables and the energy efficiency of your cooking pot. It is not possible to map everything exactly. The main goal is to arrive at the correct order of magnitude and enable comparisons.
Many recipes on the blog are designed for two portions, which is practical for couples or individuals who want leftovers. The quantities can be easily adjusted for more people.
The estimated carbon footprint is primarily related to the emissions generated by the ingredients and preparation. The following sections provide more detail about each of these parts. Finally, there is an overview of what is not included in this estimate.
The carbon footprint of ingredients #
To calculate an ingredient’s carbon footprint, I use publicly available scientific studies that provide data on carbon equivalents. These studies are typically in the form of life cycle analyses, which measure emissions from production to sale at the checkout.
Some of these are available in different varieties, such as conventionally grown lentils versus organic lentils or field-grown tomatoes versus greenhouse tomatoes. The list is extensive but not exhaustive. For instance, there is no study comparing the carbon footprint of basil to thyme. In such cases, I use estimates for broader categories, such as ‘herbs and spices’, which are also based on these studies. This is especially true for ingredients used in small quantities. Even if there is a significant difference between basil and thyme, it is unlikely to affect the recipe’s carbon footprint.
Life cycle analyses estimate emissions for each food, but the actual value depends on the production process (source). For the calculation, I assume a typical carbon footprint value, acknowledging that there may be some variation around this value. Additionally, I sometimes need to combine data from multiple sources for a recipe, and the methodological approaches of these studies may differ slightly, leading to another source of inaccuracy.
It is important to note that the carbon footprint provided in the overview refers to one kilogram of the ingredient. In the next step, I convert this to the quantities actually used in the recipe.
Other recipes do not specify exact amounts of ingredients, but rather use proportions based on a typical dietary style or daily calorie requirement (e.g. Poore and Nemecek 2018 or “All You Can Eat” by Greenpeace Switzerland and Eaternity). This approach is useful for calculating an overall carbon footprint over a longer period of time. However, this blog focuses on individual recipes that can be easily incorporated into your daily diet. Therefore, it is more sensible to concentrate on each recipe and the necessary ingredients.
The carbon footprint of the preparation #
Unfortunately, the studies on the emissions generated by the preparation of recipes are not quite as good as those on the ingredients: I mainly use a study from Switzerland that looks at the electricity consumption of different cooking and baking methods (source).
I have created a small calculator from the data in this study in order 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 cooker and oven model: It is the Electrolux SB7 cooker with a ceramic hob and an oven capacity of 70 litres. Your individual case will probably be different. If you happen to know of any other scientific work on this topic, please let me know at hello@climate-friendly-cooking.com.
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 has estimated at 366g carbon per kilowatt hour for 2020 (source).
What is not included in the carbon footprint? #
The focus of the carbon footprint is on the ingredients and their preparation. In fact, there are more sources of carbon emissions from our food, but I cannot look at them here:
- Your trip to the supermarket: It makes a difference which mode of transport you use to get to the supermarket - but it also depends on how often and how much you shop. It’s very hard to generalise. (I usually walk to the shop.)
- Storing food: You probably store some things in the fridge and some in the cupboard. However, allocating the annual consumption of your fridge to each food item is complicated: It depends on how big and how full your fridge is, and how long you keep a food item in the fridge.
- Your kitchen appliances, your cooking utensils, your crockery and cutlery: These are all consumer goods that are often used for a very long time. Even if you can estimate the carbon emissions involved in making a cooker, it is difficult to allocate them to each cooking process (especially if it is used for more than 10 years).
- Your visit to this website: Using the internet also has a carbon footprint. In this case, it is only a few grams.
Summary #
The carbon footprint of the recipes on this blog is estimated but not perfect. I aim to cover the carbon emissions from ingredients and preparation, providing a typical carbon footprint for each recipe. However, please note that this is an approximation and may not be accurate to the gram in individual cases. I hope these explanations have helped you understand the carbon footprint of each recipe on the blog.
Want to see all recipes? This way! 🥑
Or are you looking for the recipes sorted by their estimated carbon footprint? You can find them here! 🍳
Do you have specific suggestions and data that could be used to improve this estimate? Feel free to send me an e-mail to hello@climate-friendly-cooking.com.