Putting The "Carbon Footprint" of Farming in Perspective

no-till corn

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When thinking about “carbon footprints” it helps to have real numbers to put things in perspective. The EPA estimates that for the US, agriculture represents about 8% of total human-related greenhouse gas emissions. The following is a list with a little of the detail of what makes up the footprint of an acre of a rain-fed Midwestern corn crop with a few other things thrown in for comparison. Since we grow 80-90 million acres of corn its something that matters. The values are all expressed as pounds of CO2 equivalents. If you want Carbon equivalents multiply by 12/44

Some “Carbon Footprints”

  • embedded carbon in the seed treatment chemicals that help get the corn growing strong – 0.56
  • Embedded carbon in a fungicide sprayΒ  – 2.7
  • The gas to drive 2 miles each way to the grocery store for a car that gets 20 mpg – 3.9
  • Running a 2-stroke lawn mower for an hour – 6.1
  • Fuel to drive a sprayer over an acre to make a pesticide application – 7.3
  • Fuel to drive the no-till planter in the spring – 31
  • All the embedded carbon for a pest control program on the acre that would really optimize corn yield – 52
  • Fuel to run the combine over the acre at harvest – 59
  • Fuel for all the farming operations on that acre if it is no-till – 169
  • Fuel for all the farming operations if it is conventional till – 231
  • Embedded carbon in a synthetic fertilizer program (120 lbs N, 40 lbs P, 35 lbs K) – 502
  • Nitrous oxide emissions if 1.5% of the applied nitrogen gets converted to that gas (fairly typical range) – 823
  • Fuel to harvest a processing tomato crop (for a vegetable crop comparison) – 1,348
  • The total carbon footprint of an acre of no-till corn not counting carbon sequestration – 1,829
  • Methane emissions from stored manure for 120 lbs of N (1.5% conversion) for an acre of Organic corn – 1,936
  • All the fuel to grow an acre of the processing tomato crop – 3,627
  • The EPA estimated average annual household carbon footprint – 22,880

In the acre of no-till corn was also “cover-cropped” on the order of 1,100 lbs of carbon dioxide could have been removed from the atmosphere. This sort of corn might produce 225 bushels/acre so the carbon footprint if farmed with conventional tillage comes out to 0.15 lbs CO2/lb corn. In the no-till with cover crop scenario that is dropped to 0.059 lbs CO2/lb corn. If this isn’t something you’ve seen before I would be interested to know what did or didn’t fit your expectations about the relative “footprint” of different farming elements.

Cornfield Photo by 1 Riverrat

Written by sdsavage

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