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  Sierra Magazine
  May/June 2006
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Decoder: Miles to Go Before You Eat
Why it pays to buy locally grown food
by Paul Rauber

Posted May 31, 2006; amended May 2009
Editor's note: Subsequent to the publication of this feature, Sierra learned that there was a calculation error in the original paper on which the article was based, "The Load Less Traveled" (Leopold Center for Sustainable Agriculture, 2002). In addition, Sierra's own calculations failed to account for the differing fuel-energy values of gasoline (light truck), diesel (commercial truck), bunker oil (ship), and jet fuel (air). We also neglected to cite the weight of our example produce; e.g., the potato was large, weighing one pound. Together, these errors led us to significantly overstate the amount of fuel needed to move the items to market.

On May 31, 2006, we posted the Leopold Center's recalculations of the fuel requirements to transport various produce to market. Unfortunately, we recently learned that those calculations were also in error. The figures below are the center's new calculations using a different (and, they think, more reliable) estimate of the energy requirement by mode of transportation. By chance the results are very similar to the miscalculated totals. Please note that for the purpose of this example, the "market" was designated to be Des Moines, Iowa.

Calculations for estimating energy (fuel) requirements to transport various produce:

  1. Use estimates for transport of goods by various modes of transport: http://www1.eere.energy.gov/ba/pba/intensityindicators/trend_data.html.

  2. Mode of transport:

    Mode of transport Energy requirement
    Ship 511 BTU/ton-mile
    Single-unit truck (gas) 4,828 BTU/ton-mile
    Combination truck (diesel) 2,801 BTU/ton-mile
    Air 21,976 BTU/ton-mile

  3. Mode of transport:

    Ship: 50 kcal/ton/mile
    Truck: 510 kcal/ton/mile
    Air: 4,372 kcal/ton/mile

  4. Input distances traveled by produce and mode of transport--from source to Des Moines, Iowa, food store:

    • Apple (Iowa) 60 miles by light truck (gas)
    • Apples (Washington) 1,722 miles by commercial truck (diesel)
    • Grapes (California) 1,887 miles by commercial truck (diesel)
    • Grapes (Chile) 5,585 miles by ship; 1,683 miles by commercial truck
    • Potatoes (North Dakota) 558 miles by commercial truck (diesel)
    • Potatoes (Idaho) 1,246 miles by commercial truck (diesel)
    • Pineapples (Costa Rica) - 1,211 miles by ship (residual fuel oil); 1,466 miles by commercial truck (diesel)
    • Pineapples (Hawaii) - 2,551 miles by plane (kerosene jet fuel); 1,683 miles by commercial truck (diesel).

  5. Calculate the BTU needed per pound of produce transported:

    • Apples (Iowa) 145
    • Apples (Washington) 2,412
    • Grapes (California) 2,643
    • Grapes (Chile) 1,427 by ship; 2,357 by truck
    • Potatoes (North Dakota) 770
    • Potatoes (Idaho) 1,745
    • Pineapples (Costa Rica) 309 by ship; 2,053 by truck
    • Pineapples (Hawaii) 28,030 by plane; 2,357 by truck

  6. Use fuel-energy values of fuels:

    Thermal conversion factors, Energy Information Administration: http://www.eia.doe.gov/emea/aer/pdf/pages/sec13_1.pdf

    • Oxygenate gas (single-unit truck) 123,000 BTU/gallon, or 961 BTUs/fluid ounce fuel
    • Distillate fuel oil - #2 diesel (combo truck) 139,000 BTU/gallon, or 1,086 BTUs/fluid ounce fuel
    • Kerosene jet fuel (plane) 135,000 BTU/gallon, or 1,055 BTUs/fluid ounce fuel
    • Residual fuel oil (ship) 150,000 BTU/gallon, or 1,172 BTUs/fluid ounce fuel

    Conversion: 1 BTU = 0.252 kcal

  7. Fluid ounces of fuel per pound of produce transported:

    • Apples (Iowa) 0.15
    • Apples (Washington) 2.2
    • Grapes (California) 2.4
    • Grapes (Chile) 1.2 by ship; 2.2 by truck (3.4 total)
    • Potatoes (North Dakota) 0.7
    • Potatoes (Idaho) 1.6
    • Pineapples (Costa Rica) 0.3 by ship; 1.9 by truck (2.2 total)
    • Pineapples (Hawaii) 26.6 by plane; 2.2 by truck (28.8 total)

  8. Number of produce itmes per pound:

    • Apples (Iowa) 2.5 per pound
    • Apples (Washington) 2.2 per pound
    • Grapes (California) one "bunch" per pound
    • Grapes (Chile) one "bunch" per pound
    • Potatoes (North Dakota) 3 per pound
    • Potatoes (Idaho) 3 per pound
    • Pineapples (Costa Rica) 0.286 pineapples per pound
    • Pineapples (Hawaii) 0.286 pineapples per pound

  9. Volume of fuel per produce item:

    • Apples (Iowa) 0.06 ounces
    • Apples (Washington) 1.1 ounces
    • One-pound bunch of grapes (California) 2.4 ounces
    • One-pound bunch of grapes (Chile) 3.4 ounces
    • Potatoes (North Dakota) - 0.2 ounces
    • Potatoes (Idaho) - 0.5 ounces
    • Pineapple (Costa Rica) - 7.7 ounces
    • Pineapple (Hawaii) - 100.7 ounces

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