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| Fig. 1: Food waste is not an uncommon sight, especially in developed countries. (Source: Wikimedia Commons) |
Not very often does a person throw out food and calculate, or even contemplate, the amount of energy that would have been available for our cells had we eaten that food. Perhaps even less often does a person throw out food and calculate the amount of energy that was used in order to grow the food that ends up in the dumpster. However, these energy statistics should matter because in developed countries such as the United States of America or much of Europe, scenes like Fig. 1 are not uncommon. The current food system and norms surrounding production and consumption create inefficient uses of energy.
The unit of food energy is the Calorie (with a capital C), also known as kilocalorie. A calorie (with a small c) is the amount of energy required to heat 1cm2 of water by 1°C, which is equivalent to 4.184 Joules. By extension, a Calorie is the equivalent of 4148 Joules. Barclay has estimated about 141 trillion Calories of food go to waste each year. [1]
The energy we throw into the landfill each year is quite substantial. Based on the assumption that lifting something that weighs 2.2 pounds one meter off the ground requires 10 Joules of energy, Barclay points out that something that is only 26 Calories, like a small piece of chocolate, has enough energy to lift an 8,600 pound SUV six feet in the air. [2]
For another example, let use the data point that Britain has 300g of food waste per capita per day. [3] If we assume all 300g happen to have the same caloric makeup as our chocolate morsel example - 1.3 grams of fat, 0 grams of protein, and 3.6 grams of carbohydrates for 26 Calories - we can calculate how much energy is in this food that is wasted: [2]
If the nutritional makeup of all food in Britain was resemblant of a chocolate morsel, there would be 27 million Joules of wasted energy per capita per day in Britain, and only 10 Joules needed to lift 2.2lbs of food waste one meter out of the trashcan and into the dog's dish.
It is important to note that different types of food demand different amounts of energy to be produced. Table 1 below outlines the energy efficiency of different types of food.
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| Table 1: Energy Use and Efficiency of Food Products. [3] |
Because beef is among the least efficient food products, it can be used as an example to show some of the worst case scenario effects of food waste. In 2015 the United States produced 23.7 billion pounds of beef. [4] The New York Times estimates that about 40% of all food is wasted in the United States. [5] This gives us:
The amount of energy used to produce beef that is eventually wasted is quite significant. Returning to the analogy of per capita annual energy consumption in the U.S., energy used to fuel the 9.4 billion pounds of wasted beef alone is equivalent to the annual energy needs of 2.4 million Americans. If we added all the energy used to produce all other wasted food products as well, it would be even more obvious that there is a massive amount of energy being used quite inefficiently.
Both food and energy are two things that are precious, valuable, and necessary in the lives of humans, especially in the 21st century. Wasted food is wasted energy, and in the future when energy efficiency becomes key to our survival, it will be important to redesign our food systems.
© Michaela Crunkleton Wilson. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. 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] E. Barclay, "US Lets 141 Trillion Calories of Food go to Waste each Year," NPR, 27 Feb 14.
[2] M. Kramer, "Twenty-Six Calories Can Lift an SUV," NPR, 16 Nov 06.
[3] D. MacKay, Sustainable Energy Without the Hot Air (UIT Cambridge Ltd, 2008).
[4] "Overview of the United States Slaughter Industry 10/27/2016," U.S. Department of Agriculture, 27 Oct 16.
[5] S. Sengupta, "How Much Food Do We Waste? Probably More Than You Think ," New York Times, 12 Dec 17.
