The carbon foodprint of 5 diets compared

Comparing Carbon Foodprints

It is well understood that meat production has a big carbon footprint.

Numerous studies detail the climate impact of livestock, but just how big is it’s impact on a person’s foodprint?

This post compares the carbon footprints of five different American diets and finds that when it comes to foodprints vegan’s lead the way.

The carbon footprint of different diets

Even since the FAO announced that 18% of global emission result from livestock people have talked about the climate benefits of reducing meat consumption.

More recent studies show that food system emissions could account for as much as quarter of all human emissions.  That is 12% from agricultural production, another 9% from farming induced deforestation, and a further 3% from things like refrigeration and freight.

Such studies beg the question, what is the impact of meat on an individual’s foodprint?

This analysis tries to answer that question using data from the US.  In it we compare five different diets:

Meat Lover, Average, No Beef, Vegetarian and Vegan

For each diet we look solely at the emissions associated with food supply, so we do not include those from consumer’s transportation, storage or the cooking of food.  Nor do we consider land use change emissions.

Rather than bore you with the methodology let’s start with the results and work back through how they were calculated.

The results of our analysis look like this:

The Carbon Foodprints of Different Diets

A Vegetarian’s foodprint is about two thirds of the average American and almost half that of a meat lover.  For a Vegan it is even lower.  But perhaps most interestingly, eating chicken instead of beef cuts a quarter of emissions in one simple step.

An Average American’s diet has a foodprint of around 2.5 t CO2e per person each year.  For a Meat Lover this rises to 3.3 t CO2e,  for the No Beef diet it is 1.9 t  t CO2e, for the Vegetarian it’s 1.7 t CO2e and for the Vegan it is 1.5 t CO2e.  Each of these estimates includes emissions from food that is eaten, wasted by consumers and lost in the supply chain.

In the average diet animal products make up 60% of emissions despite accounting for just a quarter of food energy.  For the Meat Lover beef consumption causes almost half of emissions from just a tenth of food energy.  In the No Beef diet all the reductions from the Average foodprint come by switching from beef to chicken.  The difference between the Vegetarian and Vegan diets arises from dairy consumption being switched to a mix of cereals and vegetables.

Perhaps the most fascinating thing is that although the foodprints vary greatly, three fifths of each diet is identical.  In other words, 60% of food energy consumed is the same in each of these four diets.

The share that is constant accounts for 1550 kcal of food energy per day and about 0.7 t CO2e of each foodprint.  So all the variation depends on the remaining 1,000 kcal per day.  The Vegan gets these 1000 kcal for 0.8 t CO2e, the Vegetarian for 1 t,  No Beef for 1.2 t, Average for 1.8 t and the Meat Lover for 2.6 t.

The diets we compared

Each of these five diets are variations of the average American diet based on data from the USDA’s Economic Research Service.

For each of our diets we assume consumption of around  2,600 kcal of food energy each day, roughly equal to an average American.  This should not be confused with total food supply which is around 3,900 kcal each day.  In each diet food energy is split up among nine different food groups.

The five diets are all variations on the average diet.  We assume the Meat Lover eats more red meat, white meat and dairy in place of some cereals, fruit and vegetables.  The No Beef diet is just the average diet with all beef consumption switched to chicken.  The Vegetarian switches away from beef and chicken to fruit and vegetables, while also reducing oils and snacks.  The Vegan does much the same as the vegetarian while also eliminating dairy through further switching to cereals, fruits and vegetables.

In terms of food energy distribution the diets look like this:

The diets we compared

The food energy that remains the same is each diet is roughly 450 kcal of cereals, 80 kcal of fruit, 50 kcal of vegetables, 580 kcal of oils, 220 kcal of snacks and 180 kcal of drinks.

Comparing food group emissions

The reason that these five foodprints vary so much despite being so similar is that the carbon intensity of food consumption differs greatly between the food groups.

To estimate each foodprints we first calculated the carbon intensity of food consumption in each group.  This involved estimating the cradle to retail emissions of food production (kg CO2e/kg product), converting each to emissions per unit food energy produced, and then adjusting for food waste and supply chain losses.  This gives emissions per unit of food consumed (g CO2e/kcal).  For a more complete explanation see our shrink your food footprint page.

The carbon intensity of food consumption for each food group is as follows:

Comparing emissions of consumed food

These figures estimate the emissions produced in the process of supplying a kilocalorie of food energy for each food group.  They show on average how carbon intensive it is for Americans to get their energy from the different food groups.

Unsurprisingly red meat is the most carbon intensive way to get food energy, followed by dairy, fruit and chicken.  Cereals, oils and snacks are the least carbon intensive.  These factors are the reason why foodprints gets smaller as less red meat, dairy and chicken are consumed.

Although the carbon intensity of food production is the main driver in these figures, each is also influenced by how calorific foods are and what scale of supply chain losses and consumer waste they suffer.

For example oils, snacks and cereals are each highly calorific and have relatively low losses and waste, which results in them performing very well.  The opposite is true of fruits and vegetables which are less calorific per unit weight but have a very high share of consumer waste and supply chain losses.

Using food groups also hides great variation of carbon intensity within each group.  A hot housed tomato can have emissions 5 times higher than one grown in season, potatoes have tiny footprints compared to many other vegetables, and cheese has much higher emission than milk.  So by limiting ourselves to just nine food groups we greatly understate the potential that changing diet has to reduce food emissions.

What about my foodprint?

This analysis attempts to show the important role animal products, and red meat in particular, have in determining the scale of a person’s foodprint.  It’s relevance to your own foodprint will depend on what your own diet is like.

Because we use national averages for food consumption, production emissions, food energy content, food losses and food waste  our estimates may vary significantly from an individuals diet.

Such caveats aside, this analysis does highlight that a small share of the food we eat can cause the majority of our food emissions.  Beef, lamb and cheese are among the most carbon intensive things we can eat, while milk, out of season fruit and other meats can also have relatively high emissions.

Shifting some of your diet away from these foods towards cereals or in-season fruit and vegetables is a very effective way to shrink your foodprint.  If your aiming for a very low carbon diet, you won’t do much better that a seasonal vegan diet, particularly if you also limit food waste.

 

For further reading food emissions check out:

30 Day Shrink Guide
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  • Lugh Sulian

    I sincerely believe this study is flawed and inaccurate

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  • Peter

    How many people doing this to save the planet still jet away on summer holidays…..

  • Vaalea D

    Carbon footprint.. what about land footprint? when you start looking beyond carbon to the other environmental impacts you will see even stronger data for veganism.

  • Dom of Ebb & Flowmotion

    The numbers do not lie. It will be interesting to see if education or the onslaught of negative consequences is the final motivator; one can only hope that it is education, however I fear for the latter.

  • Diane Moffatt

    What are the comparitive carbon outputs of the humans in each group?

  • cyclodoc

    It should be clear that all those farm animals farting and pooping will increase the carbon footprint for everyone.
    A carbon footprint argument can be against keeping goldfish, a rabbit, or any pet.

  • Mattis Männel

    What about the gases that humans exhaust when they process their food?

  • Nojuan Especial

    Or just eat whatever the hell you want from a farm you actually personally live near.

  • Stef Scott

    I think it’s all a matter of stricter regulations on proper production of meat products. I found out while reading articles in Consumer Health Digest that there are in fact lots of ways safe practices in the meat industry.

  • SUDOisEvil

    The human body can be vegan, but the types of plants required to sustain the body away from certain habitats cannot be done without supplementation or very expensive and eco-unfriendly agricultural practices used to bring non-native plants to places they cannot otherwise survive. These hidden requirements, completely missed from the study, are a major contributor to energy consumption (through transportation and general local energy consumption to sustain otherwise unviable crops locally) were missed from this study.
    Drop meat, but embrace dairy and eggs if your body can tolerate them. 100% vegan, however, has a massive hidden CO2 cost.

    • D fong

      There is lots of evidence-based info on http://www.nutritionfacts.org advising of few health benefits from egg consumption. Check it out please. http://nutritionfacts.org/topics/eggs/

      Likewise, plenty of common plant foods are good sources of protein and calcium. There is hardly any evidence that we should have dairy for optimal health if we don’t eat other animal products.

      Many dietetic authorities around the world have advised that well-planned whole-food plant-based (WFPB) diets are healthful for humans for all stages of life. In fact, meat-based diets need to be as equally well planned as WFPB diets.

  • http://www.thegeekmemoirs.com/ Alex Tanner

    Whenever I see a study that uses ‘estimates’ (aka ‘I made this up because I want people to agree with my opinion’) for their statistics, I refuse to remotely support it.

    This ‘study’ was clearly done by a supporter of the vegan movement.

    Let’s just compare something for a moment. I eat meat. I am a full ‘carnivore’ and consume no plant foods whatsoever. I also only eat every one or two days, because I fast. My meals take minutes to cook and there is no waste, except for a small bone here and there (which can be re-used to make a broth).

    Given my diet and lifestyle, I am not responsible for the masses upon masses of production ‘footprints’. I even walk to my supermarket, so I do not add car fuel to the air. I also, where I can, buy naturally raised meat that has no toxins. There are many others like me.

    A vegan? Eat eat eat eat eat. Not to mention poop poop poop. Vegans are veritable methane machines, especially if they’re fruitarian. Then, there’s all those cores and skins that are toxic to eat so they too are thrown into the ground, releasing carbon. Fruit and veg go rotten quickly so imagine for a moment how much is thrown out because someone (not even vegans, just people who eat vegetables in general) forgot to eat it.

    Not to mention all those misshapen, ugly veggies and fruit (I think Nat Geo said 6 BILLION LBS get BINNED every year by stores because nobody will buy it).

    (Also while we’re on the subject, vegans bashing on about how meats are full of crap, your tasty little veggies and fruit are all genetically modified and do not remotely resemble their counterparts found in nature, technically your diet is more ‘fake’ than mine)

    Sorry, but this study is bullshit.