Food miles have come into vogue as a way of assessing the sustainability of our production systems. Food miles are good, but it helps to turn it around too, and take a look at how much food it would take to keep society functioning. In hunter/gatherer times a very simple equation governed our food supply. Basically the amount of energy you got from your food had to be more than the amount of energy you spent getting it. Oh, we cooked it at times, and preserved it in various ways. But overall that equation had to hold.

We blew that constraint out of the water when fossil fuels were discovered. But now here comes the rub: we can't keep using fossil fuels to lubricate our economy quite the way we have been.

In any case, I thought it would be valuable to put things in perspective by converting our fossil fuel usage into a tortilla equivalent. A 15 cm (6 in) corn tortilla has 45 food Calories in it. (That's less than half of a same size flour tortilla, but I'll stick with the corn since that's the most common in the developing world.) The average adult requires 2000 to 2500 food Calories per day, or the equivalent of 45 to 55 tortillas worth of energy to live. So we can figure 50 tortillas as a sort of minimum amount of food to keep a person alive.

Food calories, of course, are actually kilocalories, i.e. the nutritionist's 'Calorie' is actually 1000 of the engineer's 'calorie.'

Given all this, it's just a matter of converting units. I won't bore you with that. Let me just present some findings.

1. If you had a neon sign made of eight forty watt lamps (kind of an average size sign for a largish grocery store window) that was on for 10 hours a day all year, it would consume 1,168 kwh of electricity. That's 20,000 tortillas a year, or about the same amount it takes to keep a person alive for a year.


2. According to Stuart Brown of Fortune Magazine, the average Fedex truck makes 100 stops a day, and travels 1500 miles (2400 km) per month. No wonder that Melanie Warner reports in Fast Company that Fedex trucks get a dismal 6 miles per gallon ( 2.5 kilometers per liter). On the average day then, a Fedex delivery truck consumes 8.33 gallons of diesel. This translates into 5822 tortillas, or enough to keep a person alive for almost 4 months. Something to think about if you are getting your online grocery order delivered to your home as well.


3. On a five hour flight, New York to London say, a Boeing 747 consumes 18,000 gallons (75,000 liters) of fuel. This is over 12.5 million tortillas, or enough to feed a quarter million people for a day. Or to keep 10 people alive their whole lives. Assuming 500 passengers, this amounts to 25,000 tortillas per passenger to make the trip. (Not counting the 50 it takes to keep you alive.)


4. Flying strawberries up from Buenos Aires to sell in New York in January? 27,051,000 tortillas. Enough to feed half a million people for a day. (I don't know how many strawberries you can fit in a 747.)

I've focused only on energy requirements here. Obviously it takes more than tortillas to keep a person alive. But, still, I think putting our energy consumption in the units of food is pretty sobering. I don't think that we'll be going back to hunter/gatherer days any time soon. Economic systems, and large companies in particular, are amazingly creative when it comes to profits and survival. But anyone thinking that we can just keep operating the way we are is seriously mistaken.