A Farmscape Ecology Program Consumer Education Project from around 10 years ago (please note that it has not been updated with more recent information)
'Food Miles' refer to the distance that your food has been transported between its source farm and where you buy it. (Actually, you should add the distance from store to home onto that mileage or else eat it in your car or use a bicycle.) Food miles are one measure of the amount of energy used to transport your food and the consequent pollutants released by that transport. Estimates vary, but transport may account for 10-20% of the total energy use associated with the provision of a given food item. Foods with much higher total energy input (e.g., grain-fed meat) have a lower proportional transport cost (say, <10%), while foods requiring relatively low inputs and no preparation (e.g., fresh apples) have a higher proportional transport cost (e.g., >50%).
As such, Food Miles are a relatively simple (yet certainly incomplete) statistic that can be used to demonstrate the ecological importance of local foods. They can also serve as an indicator of "localness", which, in turn, may be tied to socio-economic aspects aside from those related to energy use. As the numbers above suggest and a recent debate in the press has highlighted (e.g., recent NY Times commentary), food miles alone do not fully describe the energy consumption and resulting pollution associated with a food's 'life cycle'. One can come up with scenarios under which a distant food has a lower overall energy requirement than a similar local one. This was done in the study at the heart of the NYT article. Researchers found that for a Brit, pasture-raised New Zealand lamb was a more energy conscious choice than the native grain-fed British lamb. True enough, although, as others have pointed out, locally pastured British lamb would, due to the transportation, likely win out over the New Zealand equivalent. Furthermore, examples of foods for which transport costs are a key determinant of the most ecological choice are well-documented, if less frequently cited of late.
A full Life-Cycle Analysis of the energy-use and pollution consequences of a food would certainly paint the most complete picture of its environmental repercussions. However, those calculations are complex and daunting. Although one English supermarket chain has said it will calculate the carbon footprint of all its foods, food miles remain a useful statistic for us mere mortals and, as mentioned, also serves to describe how local a food is, a factor with broader implications. The issues highlighted in the paragraph above suggest that we should not be too lazy in accepting food miles as a complete descriptor of food quality, but it's a worthy descriptor just like all the nutritional details appearing on a packaged food.
The Farmscape Ecology Program has been developing an in-store food mileage education and research program to help customers understand this aspect of their purchasing habits. Our goal is to make each customer (or at least some customers) informal sociological researchers, giving them the tools to follow and change their own buying habits. We want to provide them with the information and incentives to reduce their dependence on non-local foods.
Any move towards increased marketing of local foods will need to be a two-way process with markets providing the possibility for such purchasers and customers providing the demand. Our emphasis is not on creating guilt (which might deter customers), but rather on presenting the issue and then proposing the purchase of local foods as an attractive and highly possible solution. To help encourage this process, we have designed several tools. You are invited to review the materials provided here and give us your feedback. Thanks!
For further information on these concepts, we highly recommend the work of Rich Pirog and associates, and the detailed discussion presented by the Life Cycles Project.
Our Food Mileage Tools (click on the title link for more information):
The Green Checkout Report - The idea is to give each interested customer feedback on their purchases - their average food mileage and the associated energy use and pollutant production. In addition, we also provide information on their contribution to local economics and a map of their purchase sources. This is a rather complex form that may only be used in conjunction with educational programs. Currently, we are exploring the possibility of simply adding food mileage to the traditional register receipt, and then providing incentives for reducing that value. The form shown in this link is now the "second edition"; we tried to revamp our earlier, drier, more number-heavy report into something that was more positive and more directly related to encouraging local purchases.
Mockup of Green Checkout Receipt - While the above report has lots of information, it's probably unrealistic to assume that any store would ever consider printing it out for their customers. But how about just incorporating the food miles information into the store's receipt? While we haven't conquered all the technological glitches of integrating such information into a POS (point-of-sales) system, it should not, theoretically at least, be difficult. POS systems are the industry name for those checkout systems that spit out a total and receipt after your items have been scanned. This draft is still a bit nerdy but heck, if you're going to read your receipt... This poster explains how to read the receipt; values used in the calculations are listed in the caveats below.
Excel Spreadsheet for Food Mile Checkout Receipt - This spreadsheet prints out the above receipt. It is meant to help teachers (or even retailers who want to teach) explore food miles. It is somewhat clumsy but I am working on annotating it.
Create Your Own Food Miles Demonstration - This page contains a more detailed description of the spreadsheet and steps to follow for those considering setting up a food miles checkout demonstration. Updates, corrections and alternate versions are welcome. We'll be glad to post additional versions so that they can shared.
A Map Study of the New York City Foodshed (8 MB pdf file) This is a series of maps that we assembled illustrating the location of various farms or other food producers who sell in NYC via Farmers' Markets or CSA's. The maps help explore the factors affecting the locations of these farms. They are meant to illustrate, in part, the importance of understanding one's foodshed not just as the area from which food 'flows' to a given point (e.g., NYC) but also as the area where farm production is affected by 'flow back upstream' from that given point.
Food Miles Poster (click on it for a full size image): Illustrates roughly how much gas and carbon dioxide are used by various food transport methods.
What Food Miles Can & Can't Tell You Poster (click on it for a full size image): Food Miles aren't the whole story, but they are part of the story. This poster is meant to communicate that.
Some Caveats: There are a few cautions that need to be included when discussing this issue and these calculations.
1) As noted, transport is almost never the largest block of energy use associated with a product. Even with organic produce, substantial fossil fuels are often used during cultivation and harvesting. Once the product is purchased, cooking can also add significant energy use and energy expended in the act of shopping can be appreciable. For this reason, more complete forms of analysis have been designed. Two common approaches have been Ecological Footprints and Life-cycle Assessment (links are to the web pages of other organizations). While these methods are certainly more complete and are necessary for certain applications, we felt food-miles were most appropriate in our case because of their simplicity and direct linkage to the "localness" of a product.
2) Actual energy use and pollution values are of course painful to derive. We did not go out and ride the roads with all the store's produce while attaching some fancy air sniffer to the truck's exhaust pipe. Instead, we relied on an online road distance calculator (Mapquest) and published estimates of the fuel use and carbon dioxide production associated with different modes of transport (see references in Rich Pirog's work). We do not have the expertise to look at efficiencies in more detail (e.g., we did not try to take into account potential differences in efficiencies between local and long distance transporters). Furthermore, we need to do more work identifying the shipping methods for international cargo; whether something comes by air or sea makes huge differences in the associated transport energies. We can guarantee you that our fuel estimates are precisely wrong, we can only hope that they are roughly right. Because they do not take into account refrigeration during transport, the fact that most transport does not take the most direct route but weaves amongst stops, and many delivery vehicles spend part of their time travelling empty, we believe that, if anything, we have underestimated actual energy consumption and CO2 generation. Our most current estimates of gallons of gas equivalents used per ton carried per 1000 miles travelled are 185.5, 26.7, 4.3 & 2.7 for airplane, truck, boat & train, respectively; likewise, for pounds of CO2 generated per ton carried per 1000 miles, we used 4554.0, 590.2, 94.4 & 51.3. These values differ slightly, but probably not significantly, from those illustrated in our poster. We used these values for the calculations appearing on our receipt.
3) Currently our work has been limited to produce and dairy items. While we could also calculate food miles for more processed foods, this value seems somewhat meaningless given the energy involved in the processing itself and the unknown distances that the ingredients have already been transported by the time they reach the processing plant. However, see estimates for Strawberry yoghurt out of the Leopold Center.
4) Even with something as simple as fruits and vegetables, it is sometimes not possible to know where an item comes from with any precision. Certain distributors now mark their cartons with simply "Product of the USA or Mexico". In our part of the country, such doubt makes little impact on food miles considerations since "USA" almost always means California. However, if organic fruit and vegetable producer-distributors (e.g. UNFI) extend their national and international reach, consumers will need to pressure for good source accounting if they want to know where their food comes from.
Any ideas or comments are welcome. Please contact us if you have questions or input. Enjoy!