Like me, you probably often have a dozen eggs on your grocery list. And when you wake up bleary-eyed on a Saturday morning, you face the choice of how you will buy those eggs.
In some parts of the country, there are three choices for procuring eggs. You can buy them at a supermarket, at a local farmers market or directly from a local farm. If you want to support small farms – for any reason – then the second or third choice will be yours. But what if you care most intensely about what are increasingly being called “food miles” and how much energy is used bringing the food from the farm to your doorstep?
Food miles are the number of miles that food has traveled to reach you. It seems intuitively obvious that the lower the number of food miles, the less energy you are causing to be used for your groceries. It’s better to buy food produced near you than food grown across the country, right?
Sadly, intuition does not always agree with reason and arithmetic.
Jude Capper of the Animal Sciences department at Washington State University recently took me through the example of buying eggs from the three sources mentioned above. The numbers that follow are just an example – your numbers would vary.
Let’s say it’s 1.5 miles from a house to the supermarket, 7 miles from that house to the farmers market, and 27 miles from that same house to a local poultry farm that will sell to the public. (Those numbers fit my situation pretty well, although they were chosen by Capper for another location.)
Now let’s think of the food miles of the eggs themselves. In the case of the supermarket, Capper’s example has them coming from 800 miles away in an 18-wheeler. Add the 1.5 miles for a person to get to the store and that’s 801.5 miles of total driving around before the consumer first picks up the eggs.
“Obviously, on the first analysis, the food miles for the supermarket example are looking grim,” says Capper with a laugh.
Even if the semi-truck hauls other goods (like apples) back to where it came from, there’s a lot of traveling involved to get eggs and produce to us.
The farmers market example and the local poultry farm case do involve less traveling for each egg. But there are other issues we want to consider since our real concern likely isn’t food miles itself but how much energy is consumed getting the eggs from the chickens to our frying pans.
Here are two important facts. Let’s say the farmers market eggs get to their sales booth via a pickup truck, and I go back and forth to where I buy my eggs in a car.
I know it may not seem like it, but 18-wheelers are really quite fuel-efficient compared to pickups and cars when you consider all that they haul. Capper tells me they typically get about 5.4 miles on a gallon of diesel (plus, for a refrigerated truck capable of carrying eggs, they burn half a gallon of fuel per hour to keep everything cool). But the trucks move up to 23,400 dozen eggs!
Capper showed me the arithmetic that clearly shows the most energy efficient way for me to buy eggs for my household is to go to the supermarket, essentially relying on that highly efficient 18-wheeler. And that’s not even considering the notion that I’ll likely go to the supermarket anyway, to buy laundry detergent, light bulbs, toothpaste and bottles of eye-drops. (What can I say, I swim a lot.)
There are other reasons to buy locally produced eggs, Capper is quick to point out. You might want to support local agriculture, or you might prefer the taste of eggs from alternative systems. But if energy conservation is your primary concern in what groceries you buy, it pays to reason and go with the numbers rather than following your gut.
Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. Follow her on the web at rockdoc.wsu.edu and on Twitter @RockDocWSU. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.