Society for the Advancement of Animal Wellbeing

- Protecting Animals and Conserving the Environment

The Easiest and Most Effective Solution


What is the single most effective way of reducing carbon dioxide and greenhouse gas emissions in an effort to stop global warming and the climatic changes associated with it?

Although transportation and the cars we drive have a huge impact on the environment, larger still is the burden our diet is placing on the Earth. What we consume as individuals causes more global warming than all the cars, planes and other transportation in the whole world put together that’s according to the authoritative UN Livestock’s Long Shadow report.

As global warming has become a more pressing issue that is affecting people on all continents from all walks of life, there has been a trend toward studies by various scientific bodies on the relationship between our diet and the environment, let’s take a look at some of these studies.

The Japanese Study

 In Japan a study by Akifumi Ogino from the National Institute of Livestock and Grassland Science has assessed the effect of cattle raising for meat on the environment. The researchers paid particular attention to animal management as well as the production and transportation of feed.

Their calculations showed that to produce a single kilogram of beef produced the equivalent greenhouse gas (GHG) emissions to 36.4 KG of carbon dioxide and requires 169 mega joules of energy if we convert that to something more understandable we could say that to produce 1 Kg of beef emits the same amount of CO2 as driving an average European car for 250 km and uses enough energy to light a 100-watt bulb for 20 days.

The study did not take in to account the transportation of meat and so the actual CO2 values would be much higher still.


The University of Chicago Study

Another study conducted by Dr. Pamela Martin and Dr. Gidon Eshel assistant professors of Geophysical Sciences at the University of Chicago, looked at the energy usage as well as the carbon footprint of five different diets including a typical American meat based diet as well as a lacto-ovo vegetarian diet (includes milk and eggs).

The report entitled “Diet, Energy and Global Warming” showed that an individual consuming an average of 3,774 calories per day on a meat based diet will have a carbon footprint 1,485 kg per year greater than a person on a plant based diet. The research showed that diets based on red meat and fish were the most inefficient. To catch larger predatory fish involves long voyages in big fishing vessels which burn huge amounts of fuels.

Doctors Martin and Eshel also took in to account non-carbon greenhouse gases released during the production of meat, predominantly these are methane and nitrous oxide. Methane is produced in the intestines of ruminant livestock that is animals that eat grasses. It has been estimated that a single sheep can produce 30 liters of methane per day whilst a dairy cow can produce more than 200 liters per day.

Currently methane emissions are approximately 100 million tons per year 71% of which is from cattle, when considering that kilo for kilo methane is 23 times stronger than carbon dioxide as a global warming gas this has become a significant problem. In fact methane release from livestock is estimated to be 3% of Britain’s total greenhouse gas emissions. The manure and waste from livestock also produces methane as well as host of other gases including nitrous oxide from pig waste. Nitrous oxide is 296 times more warming to the atmosphere than CO2.

Even though the total volume released of these gases are small in comparison to CO2, their effects molecule to molecule are stronger and atmospheric levels of these gases have dramatically increased due to the massive increases in meat production. From 1961 to 2007 consumptions of meat jumped from 71 million tons a year to 284 million tons currently, in real terms that’s 55 billion animals slaughtered per year for food. Dr. Gidon Eshel commented “We say that however close you can be to a vegan diet and further from the mean (average) American diet, the better you are for the planet. It doesn’t have to be all the way to the extreme end of vegan. If you simply cut down from two burgers a week to one, you’ve already made a substantial difference.”

Using the results from this study researchers have estimated that if every person in America changed their eating habits and made one of their weekly meals plant based it would be the equivalent of taking 5 million cars of the road. If they ate plant based meals for one day a week it would be the same as taking 8 million cars of the road that is assuming the population to be 300 million and the average daily car emissions of CO2 to be 35 pounds per day.

Now if the same could be done in every country around the world then the carbon savings would be substantial enough to help offset the present rate of global warming. Even cutting out a couple of burgers a week or a couple piece of sushi or sausages would help significantly.

The Sweden Study

In another joint research study conducted by Annika Carlsson-Kanyama from the Department of Systems Ecology, Stockholm University, Sweden and Mireille Faisy from the Swiss Federal Institute of Technology, an in depth calculation was made to identify the carbon impact of a single cheeseburger which includes the meat, buns, cheese, onions and pickles.

The calculation took in to account every step of production and transportation of the meat, bread and other ingredients. The final result showed that to produce one cheeseburger emits anywhere from 766 grams of carbon to 3,000 grams of carbon depending on the production method, this does not include the carbon cost of running the restaurant nor the methane output of the cows. When including methane and extraneous factors the carbon impact of a single burger ranges from 3.6 to 6.1 kg per burger the average of which is 4.35 kg of CO2 per burger.

The average US citizen eats between 1 and 3 burgers weekly, assuming again a population of 300 million that means that just from eating burgers alone not including meat from other meals during the week; the US creates between 65.25 million to 195.75 million metric tons of equivalent CO2 output. Putting this in terms easier to understand, A Hummer SUV which is known as a heavily polluting vehicle emits 10.1 tons of CO2 over a year, so the yearly burger consumption produces the same amount of greenhouse pollution as 6.5 million to 19.6 million SUVs per year. This is just for one country, so having one less burger a week could have a huge difference.

Amazon Rainforest and Deforestation

Apart from transportation and methane emissions caused by the meat industry one of the main reasons for its huge carbon foot print is the on-going mass deforestation associated with feeding cattle. According to the 400 page Livestock’s Long Shadow” report by the U.N. Food and Agriculture Organization 18% of all global warming causing gases come from Livestock.

In addition the report states that 70% of the former Brazilian rainforest is devoted to animal agriculture, the land is used to grow crops to feed livestock or as grazing lands. In fact 30% of the world’s entire land surface is dedicated to raising animals for food. In order to provide the fodder to produce meat the forests are being cut down at alarming rate.

In 2007 approximately 7,000 square kilometers of Brazil’s forest was cut down that is an area the size of the Spanish Capital, Madrid. Globally the world loses 1.5 acres of rainforest per second and as trees have the ability to sequester and absorb CO2 from the atmosphere as well as produce oxygen, the world’s forests are important in reducing and balancing the amount of Carbon dioxide in the air.

In a report authored by the UN Food and Agriculture organization entitled the Global Forestry Resources Assessment (FRA 2005), approximately 2 billion tons of carbon is released in to the air annually due to deforestation. 


So the relationship between what we eat and put on our plates and the state of our environment is very closely linked. A meat based diet has dire consequences for the future of the planet, the most immediate of which is global warming. Switching to a Vegetarian or vegan diet is simple nowadays as there are plenty of healthy and delicious foods to choose from as well as an array of vegan and soy products to enjoy. To find out more visit our go veg page.


 Return to the main page of the Environmental section.

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