The Energetics of Food Distribution
On June 11 Vermont Public Radio aired a brief piece called Running the Numbers on Local Vs. Long Distance Food wherein Jane Lindholm interviewed me about the work I do studying the energetics of food systems. The segment focused on the efficiencies typically associated with long distance food transport that can make national or even global food distribution more energy efficient relative to localized food distribution systems. The numbers I presented didn't make the local option sound particularly appealing, so I thought it worthwhile to explore the nuances of this issue a bit.
First, realize that the efficiencies associated with moving larger quantities of food in larger delivery vehicles are pretty unequivocal. When comparing the fuel needed to move a ton of food 100 miles using three alternative methods of motorized transport, a semi trailer is more efficient than a mid-sized delivery truck, which itself is substantially more efficient than moving food in the back of a pick-up truck or similarly sized vehicle . This comparison assumes the semi truck moves 40,000 pounds of food and gets 6 miles per gallon, the mid-size truck moves 10,000 pounds and gets 9 mpg and the pickup moves 1,000 pounds and gets 18 mpg, all reasonable assumptions. If rail or barge shipping had been included, their figures would be lower still.
The pickup truck requires 13 times as much fuel as the semi truck to move the same amount of food, meaning that food can be delivered from 13 times further away via motorized freight and use the same amount of fuel. Put another way, a ton of food shipped the 3,000 miles from California to Vermont via semi truck requires the same amount of fuel as an equivalent ton shipped 220 miles round trip in the back of a farmer's pickup. But what if food is shipped by semi from further afield, or shipped by pickup from the next town over? This is where the nuance begins.
The question of whether locally distributed food requires more or less fuel in its delivery revolves around how we define local. If local is within 300 miles, food that starts at the outer edge of that radius and is delivered in a small vehicle might well require more fuel than something trucked in from 3,000 miles asunder. On the other hand, if we restrain our definition of local to under 100 miles, it's likely that we are enjoying some fuel savings over food shipped from across the continent. I say 'likely' because it's not guaranteed; a small delivery vehicle that leaves for its destination only half full will double the fuel burned per unit of cargo. The arithmetic that goes along with minimizing fuel use per unit of transported food will be tedious, but we'll need to dive into it to really understand the implications of local food distribution systems.
In The Energy Cost of Food I note that, in the US food system, long distance freight only requires about 0.4-0.5 calories of energy per calorie of consumed food, which is less than 4 percent of the total food system energy demand. People make a big deal about the fuel use associated with food miles, but in reality this is such a small proportion of the total energy embodied in the food we eat that there are certainly lower hanging fruit to tackle in hopes of seeing substantive energy savings. Beyond this, those with an eye towards the future might realize that the best distribution system is one that doesn't require motorized transport at all, and instead dedicates plots of land throughout towns and cities - including people's yards - to food production so that citizens can easily walk to where they pick the freshest produce money can buy. If we could accomplish this lofty goal, I suspect we'd have solved many other food problems along the way.
- Robert King, et al. (2010) Can local food go mainstream? Choices, Vol. 25, Article 1.
Teaser credit: Charlotte Albright on Vermont Public Radio website.
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