We know that food gives us energy to work, play and live our lives. We also know that food produces energy and that all foods can be measured for its energy content which we express as calories, kilocalories (Kcals), or joules.
But did you know that the reverse is true, that energy produces food? Yes, when you look at what it takes to produce food, whether it is a head of lettuce or a big steak you can express the inputs that were necessary to produce that meal as energy.
It takes food to produce human energy and it takes energy to produce food.
Let's dig a little deeper.
Growing foods such as wheat, apples, and chickens requires energy to produce and then to move from the farm to your plate. Depending on the food you choose there might be fertilizers, water delivery, pesticides, energy for farm machinery and processes such as canning, freezing, packaging and transportation. Each step of the way is part of the life cycle – from farm to fork.
Scientists can measure the energy needed to complete the lifecycle but in fact it is only the energy that produces greenhouse gases (GHGs) that typically are concerned in a lifecycle analysis (LCA). Solar energy from the sun for example does not contribute to climate change, nor does the wind- or water power that drives a grain mill. But the energy needed to produce fertilizers such as nitrous oxide or diesel pumps used for irrigation contributes GHGs and have environmental impacts.
If you buy food at your local farmer’s market it probably does not have packaging and has not traveled far, so it will have a lower carbon footprint from frozen or canned foods traveling from abroad. The same is true for organic foods that do not use industrial fertilizers.
The amount of GHGs used to produce our food is substantial, as much as 30% of all emissions. But not all choices are equally GHG-intensive.
If you live in the UK and drink four cups of black tea a day boiling only the water you need over a year you will use 30kg of CO2. That’s what it would take to drive a typical car 40 miles.
But if you drink 3 large lattes a day you will use enough energy to fly halfway across Europe. Why the difference? It’s all in the milk. Ruminant cows belch a lot of methane while chewing their cuds to digest grass. Methane is an especially damaging greenhouse gas.
If you are interested in the carbon footprint of the foods you eat take a look at Mike Berners-Lee’s book How Bad are Bananas? The Carbon Footprint of Everything. I believe you’ll stop buying out-of-season air-freighted asparagus.
References and Further Reading
Mike Berners-Lee 2010. How Bad are Bananas? The Carbon Footprint of Everything. London: Profile Books.
Parikh, JK. And S. Syed. 1988. “Energy use in the post-harvest food (PHF) system of developing countries.” Energy in Agriculture 6 (4)
Elin Röös, Cecilia Sundberg and Per-Anders Hanson. 2010. “Uncertainties in the carbon footprint of food products: a Case Study on Table Potatoes.” International Journal of Life Cycle Assessment Vol 15:478-488.