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Page added on June 25, 2014
More on the Energetics of Food Distribution
In The Energetics of Food Distribution I explored the energy demand associated with transporting food based on estimates of gallons of fuel burned per ton of food moved. This is a perfectly reasonable unit, but a departure from calories of input energy per calorie of edible food, the unit I use in The Energy Cost of Food, The Energy Basis of Food Security and much of my other analytical work in food system energetics. Calorie input/output is a useful framework for studying energy flow in food systems because it affords an intuitive means of gauging the efficiency of transforming input energies – commonly from nonrenewable resources – into edible food energy. In this post I’ll revisit my earlier analysis of food distribution through this calorie input/output lens.
It’s common to talk about food as if it were a homogenous commodity. It’s not. There are many types of foods, and some pack more bioavailable energy into a given weight than others. Take bacon for instance: according to US Department of Agriculture data there’s about 420 kilocalories of food energy in 100 grams (3.5 ounces) of bacon [1]. While there are certainly foods that are more calorie dense – butter contains over 700 kilocalories per 100 grams while lard, which is nearly pure fat, packs over 900 – most foods are much less so. Carrots, a staple in veggie trays and at summer farmer’s markets, yields only 40 kilocalories per 1oo grams, and lettuce yields fewer than 20.
Given this wide variation in the calorie density of food, it should come as no surprise that the energy input/output ratio – or perhaps more accurately the energy input/food throughput ratio – of food distribution depends not just on how food is moved and how far, but also on what type of food is being moved. An energy intensive mode of distribution that moves a very calorie dense food might yield an energy input/throughput ratio comparable or even superior to a far more efficient mode of transport that moves a less energy dense food. The devil, as they say, is in the details.
Say we want to move comparable weights of bacon and carrots 100 miles via semi truck and pickup truck. Which is more efficient? Assuming the semi carries 40,000 pounds of food at 6 mpg and the pickup carries 1,000 pounds at 18 mpg, it’s clear that by far the most efficient option is to move the calorie dense bacon via semi, and by far the worst is moving carrots via pickup. Moving carrots via semi enjoys a slight advantage energetically over moving bacon via pickup, but the high calorie density of bacon cancels out much of the efficiencies of scale that come with moving larger quantities of carrots with a much larger diesel engine. In general it’s easier to make a case for transporting calorie dense foods such as meat, cheese and even eggs regardless of mode of transport, since less calorie dense vegetables and fruit require more fuel energy input per unit of food energy moved.
Much of the discourse in the local food movement revolves around the assertion that by buying food produced nearby we reduce the amount of fuel burned in the service of food transport. As I note in The Energetics of Food Distribution this can be true, but given the efficiencies of scale seen in moving larger quantities of food it isn’t always true. Another wrinkle worth adding to food distribution discussions, as I’ve hopefully demonstrated here, revolves around what type of food is being transported, particularly whether we’re choosing between shipping bacon and other calorie dense, animal-derived foods or more calorie diffuse foods such as vegetables and fruit. As long as fuel remains cheap the practical differences between these foods are small, but rising energy prices may compel us to be more discerning about what types of food we ship.
Notes
- ‘Calories’ are simply units of heat, and for those unfamiliar with metric prefixes ‘kilo-‘ means 1,000. In popular literature it’s common to speak of nutritional calories, and a nutritional calorie is actually a kilocalorie, which is 1,000 thermal calories.
5 Comments on "More on the Energetics of Food Distribution"
yellowcanoe on Wed, 25th Jun 2014 12:06 pm
I’d expect the energy consumed by shoppers traveling in their personal vehicle to purchase a small amount of groceries far outweighs the energy used in transporting the food to the super market.
redpill on Wed, 25th Jun 2014 7:46 pm
So there it is, I’m eating the next person that comes near me.
Good thing I don’t leave the house in the morning without my handy packet of Human Helper (bacon-bits).
Davy, Hermann, MO on Wed, 25th Jun 2014 8:38 pm
Well, a pickup has a much smaller footprint in the embedded energy arena, maintenance cost comparisons, financial ownership costs, cost to support the driver. The two vehicles have different applications. Try to compare a train to a truck to a pickup. A train is by far the most efficient but try to deliver salad material to my door with a train. Food density is important but nutrition is also important. The industrial food is the worst because it is not nutritious, has high embedded energy and must be shipped somewhere. Much of the cost of getting food to the human stomach is in that trip to the grocery store and the whole grocery store “complex”. Then we must consider the greatest portion of the energy is in preparation, storage, and disposal at home. There are many issues with food. The issues will be mute when the descent hits and hunger and food insecurity are present. Most likely it will be local and seasonal. Eventually there will be little or no FF calories in our food and it will be “non-industrial” food. Today we see the organic label. No one will notice that the food of the future is “non-industrial” because any food will be good food. We are near this time. If you were wise you would learn how to grow something.
Makati1 on Wed, 25th Jun 2014 8:55 pm
Was a time that the grocery store for a town of 20,000 would fit in a building 40 X 150 feet with an additional warehouse area in the back for deliveries. It had enough variety for anyone and only in season or canned veggies and fruits. Strawberries in the spring. Watermelon late summer. A big watermelon from the Carolinas was 50 cents and was at least 2 feet long.
Ah, the olden days. But, they are coming back. Do you know how to can and have the materials and equipment? I do.
green_achers on Wed, 25th Jun 2014 10:26 pm
This is silly. You don’t eat carrots for calories. It probably takes more calories to pull, wash, cut up, cook, chew and digest a carrot than you get out if it. So what? Carrots give us vitamins, minerals, fiber, and taste good.
So, if we really want to be energy efficient, we should eat nothing but bacon?
Obviously a pickup is less efficient than a semi, otherwise Walmart would employ a fleet of pickups (OK, that’s stretching, I’m not counting labor). But not too many small farmers produce 40,000 lbs of carrots in a year, much less a load. Heck, if you ship the 1000 lbs at a load, you’re hardly a small farmer, and are unlikely to have a strictly local market.
So yes, small farms are inherently less efficient, in just about every way, else the farm belt would be dotted with small farms, and here I am serious. Analyses like this one serve little purpose. They start from the assumption that BAU is a given. Thousands of carrots need to be shipped hundreds of miles, so what’s the most efficient way to do that? The given for me, with an understanding of our energy predicament, is that BAU is not an option.