The Energy of Food

Eric Verso
November 9, 2015

Submitted as coursework for PH240, Stanford University, Fall 2015


Fig. 1: Carbon Equivalent Footprint (kg CO2e per Kg product) of ruminants (red) and other types of food (blue). (Source: E. Verso - after Ripple et al.. [8])

With election season coming, global warming and the environmental issues have become a hot topic. Penalties on corporations for carbon emissions, limits on watering laws, and subsidies for fuel-efficient and/or renewable energy cars have been talked about as solutions to our environmental issues. The energy of food, however, is rarely brought up. "Food production and agriculture contribute as much to climate change as transportation," says the U.N. Secretary-General Ban Ki-Moon. [1] The simple acts of switching out beef for chicken or other types of protein in our diets, and reducing food waste would go a long way in decreasing energy consumption and preserving our environment.

Environmental Impact of Meat

A surprisingly large portion of greenhouse gases comes from food. According to a nature report, " Global agriculture and food production release more than 25% of all greenhouse gases (GHGs)". [2] A large portion of these GHG emissions can be attributed to livestock, and in particular, from raising beef and dairy cattle. Globally, 14.5% of all greenhouse gas pollution can be attributed to livestock, and according to the U.N. Food and a 65% of the livestock industry's role comes from raising beef and dairy cattle. [3,4] This is because the carbon footprint of ruminant meats (beef and lamb) is about 10 times higher than chicken. Unfortunately meat is a staple in diets worldwide: The current global average meat consumption is 100 g per person per day, with about a ten-fold variation between high-consuming and low-consuming populations. [5]

Ruminant meats have emissions per gram of protein that are an incredible 250 times those of legumes (plant based foods). [2] The primary reason for this is burping. According to the FAO, 43% of global greenhouse gas emissions associated with beef cattle come from "enteric fermentation" (methane burping). [3] An average cow in North America, burps 117 pounds of methane (which has 25 times as much global warming potential as carbon dioxide) per year. [4] Additionally, the nitrous oxide in the fertilizer needed to grow the massive quantities of corn that feeds the cows is detrimental to the environment since nitrous oxide has about 300 times as much global warming potential as carbon dioxide. [4] Largely due to fertilizer, producing food such as corn for beef cattle accounts for 36% of greenhouse gas emissions from beef and dairy. [3] The good news is that these emissions are not as harmful as those released into the air by the fossil fuel industry. because the carbon and methane emissions are largely recycled by the plants and bacteria in agriculture ecosystem.

Fig. 2: Gallons of water used for 1 pound of each type of food. (Source: E. Verso - after Hallock. [9])

In addition to the GHG emissions, beef production takes a larger toll on other aspects of the environment. Producing just one pound of beef takes about 1800 gallons of water, an outlier when compared to other sources of protein (see Fig. 2). Producing 1 kg of protein from kidney beans requires approximately eighteen times less land, ten times less water, nine times less fuel, twelve times less fertilizer and ten times less pesticide in comparison to producing 1 kg of protein from beef. Furthermore producing 1 kg of beef generates five to six times more waste (manure) than producing 1 kg of protein of chicken and eggs. [6]

Food Waste

As large as green house gas emissions are due to beef production, food waste emissions are much larger. In the United States we throw away around 40% of what we produce; and globally, 28% of the land under cultivation grows food that ends up in landfills. [1] When we throw away food, all of energy, water, and the emissions from nitrous oxide from fertilizers used in production are wasted, which is compounded by the massive amounts of methane released in landfills. Despite this, we waste over 1 billion tons of edible food each year, which is more than a third of all food produced worldwide. As seen in Fig. 3, if "food waste" were a country, would be the third biggest polluter in the world behind only China and the United States. [1] Food waste accounts for almost half of all carbon dioxide emissions associated with waste in the UK, and it is estimated that the waste sector accounts for approximately 3% of global GHG emissions. [7]

Fig. 3: Total GHG emissions if food waste were a country. [10] (Courtesy of the FAO.)

Our generation has the unenviable task of greatly reducing green house gas emissions to avoid the inevitable devastating impact of global warming and rationing water before we run out of it. Unfortunately, it is difficult to rely on the government to implement meaningful large scale changes to reduce fossil fuel emissions because of the power and influence of the coal and oil industries. However we can make individual choices that collectively can have a huge impact on the environment, such as the amount of food and type of food that we eat. By switching from eating beef to other protein sources and eliminating food waste, we can individually do our part in saving the environment.

© Eric Verso. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] J. D. Sutter, "Why World Leaders are Eating 'Landfill Salad' and Cucumber-Butt Pickles," CNN, 1 Oct 15.

[2] D. Tilman and M. Clark, "Global Diets Link Environmental Sustainability and Human Health," Nature 515, 518 (2014).

[3] "Tackling Climate Change Through Livestock," Food and Agriculture Organization of the United Nations, 2013.

[4] J. D. Sutter, "Why Beef is the New SUV," CNN, 29 Sep 15.

[5] A. J. McMichael et al., "Food, Livestock Production, Energy, Climate Change, and Health," The Lancet, 13 Sep 07.

[6] J. Sabaté et al., "The Environmental Cost of Protein Food Choices," Public Health Nutr. 18, 2067 (2015).

[7] E. Papargyropoulou et al., "The Food Waste Hierarchy as a Framework for the Management of Food Surplus and Food Waste," J. Clean. Prod. 76, 106 (2014).

[8] W. J. Ripple et al., "Ruminants, Climate Change and Climate Policy," Nat. Clim. Change 4, 23 (2013).

[9] B. Hallock, "To Make a Burger, First You Need 660 Gallons of Water," Los Angeles Times, 27 Jan 14.

[10] "Food Wastage footprint Impact on Natural Resources," Food and Agriculture Organization of the United Nations, 2013.