Understanding the Carbon Footprints of What We Eat

Science & Food
By Science & Food
Nov 8, 2016 11:26 PMNov 19, 2019 9:43 PM


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Eat local. Avoid red meat. Beef is bad. The media is full of messages about food. Navigating the world of food choices can be challenging and overwhelming. Here is where some knowledge of food, and bit of science, can help. With science, we can identify the number of calories in a food item. We can also easily understand the amount of protein or fat to help us choose to eat – or avoid – particular foods. Need more vitamin C? Food labels can also help us identify vitamin contents. Want to know whether a product is clean label? Food labels have your answer! However, a lasting challenge we have as consumers is being able to identify and assess the environmental impact of foods that we eat. In comes the CO2 equivalent as a solution. CO2 equivalent, or CO2e, is a common unit of measurement that allows us to standardize greenhouse gas emissions. For example, is it worse for the environment to eat 118 apples or a quarter pounder burger? To standardize measurements of greenhouse gas emissions, grams CO2 equivalent (or CO2e) is a common unit of measurement. CO2e is calculated by multiplying the global warming potential (GWP) of the greenhouse gas (GHG) emissions produced by each food component by the amount of GHG produced. For example, beef production generates carbon dioxide, methane, and nitrous oxide. Since each of these three greenhouse gases has a different potency for environmental effects, they each of have their own pre-calculated global warming potential, or GWP. Thus, the relative effects of each GHG can be determined by multiplying this GWP factor by the amount of each GHG produced (ex. GWP(methane) x GHG(methane) = grams CO2e for methane). Then the CO2e for each GHG can be added together to yield the total grams CO2e for a particular food component [1]. By converting units to CO2e, we can easily compare the approximate carbon footprint of different foods. To illustrate the carbon footprint of a beef versus vegetarian food, see this infographic (Fig. 1) that we created together with Professor Jenny Jay and the UCLA Healthy Campus Initiative. It is remarkable to see how one beef burrito produces 896 grams of CO2 equivalent, which is just over ten times the amount of CO2 equivalent of a veggie burrito at 88 grams CO2e [2]. In fact, a quarter pounder burger has the same CO2 equivalent as 118 apples [3]. Livestock contributes a remarkable 14.5% to global GHG emissions [2], in addition to water pollution, destruction of land, and and species extinction. Beef production is particularly demanding, requiring on average 28 times more land, 11 times more water, and producing 5 times the GHGs than the average of any other type of protein such as pork or chicken [4]. What we take away from this information is ultimately our own personal choice. However, knowledge of how the foods we eat impact our environment can ultimately empower us to make informed decisions – allowing us to make a responsible and educated choice whether to dig into that burger or break out the veggie patty!

References Cited:

  1. Chamberlain, A. GHG emissions: demystifying carbon dioxide equivalent (CO2e). http://info.era-environmental.com/blog/bid/58087/GHG-Emissions-Demystifying-Carbon-Dioxide-Equivalent-CO2e

  2. Jay, J., Rowat, A., & Malan, H. (2016). What’s the ‘footprint’ of a burrito? http://healthy.ucla.edu/foodday/burrito

  3. Jay, J. (2016). Personal communication.

  4. Eshel, G., Shepon, A., Makov, T., & Milo, R. (2014). Land, irrigation water, greenhouse gas, and reactive nitrogen burdens of meat, eggs, and dairy production in the United States. PNAS, 11(33). Retrieved from http://www.pnas.org/content/111/33/11996.full

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