Crops Insights

Perspective: Is corn production a villain or hero in our economy?

jack dewitt


“Growing Corn Is a Major Contributor to Air Pollution, Study Finds.” No kidding. That was the headline of an NPR story on April 1. The source: A study published in Nature Sustainability — “Air Quality-related Health Damages of Maize” by Jason Hill, et al. The authors estimate “4,300 premature deaths can be attributed to corn production.” I repeat, “estimate.” To arrive at their estimated deaths, they also estimate PM2.5 (Particulate Matter of 2.5 micrometers in diameter or less) emissions from corn production, fertilizer and pesticide production, and transportation of production inputs.

I estimate it’s mainly another attempt to trash corn production and change what we grow for food.

There is no doubt that excessive PM2.5 particles in the air can cause health problems (they are about 1/10th the diameter of a human hair). They can evade, at least for a time, the defenses of the respiratory system that prevent entry or evict pollutants. But concentrations of less than 12 particles per cubic meter is not considered unhealthy, and up to 35 particles is only a moderate risk. A clear day generally means particles are five per cubic meter or less. I have not been to the Midwest in summer, but I am guessing the frequent rains and winds would keep the air relatively clean except around big cities. In the real world, I estimate the health risk from PM2.5 near corn fields is nil.

Trashing corn is a favorite subject of many researchers and journalists. Corn gets blamed for obesity, colon cancer, ruining our soils, and destroying family farms and small towns, among other things, all unfairly in my opinion. Michael Pollan spends 1/3 of his bestselling book, “Omnivores Dilemma,” denigrating corn. So I’m going to spend the rest of this column defending corn and its place in our economy.

Pollan says it takes 50 gallons of oil to grow an acre of corn, using one Calorie of fuel energy to grow one Calorie of food, and it’s “too bad we can’t simply drink the petroleum directly.” He is correct about the amount of oil it takes to grow an acre, but not much else. No writer seems to understand the gift in energy equivalent growing corn gives us.

Notice I capitalized “Calorie.” That stands for kilocalorie, or 1,000 calories. (A calorie is defined as the energy needed to raise the temperature of one gram of water by one degree Celsius, or 1.8 degrees Fahrenheit.) The Calories stated on food packages are kilocalories. Since that unit is familiar to most people, that is the unit I am going to use in the following discussion. Energy in any form — oil, electricity, photosynthetic — can be converted to Calories.

University of Iowa ag engineers have calculated the energy cost of growing no-till corn using diesel as the energy unit. They calculate it takes 23 gallons of diesel to manufacture the fertilizer needed for one acre, and 2.5 gallons to plant, spray and harvest. Pesticide manufacturing requires 1 gallon per pound of active ingredient, so the engineers added 3 gallons for pesticide manufacture. Growing, processing, and distributing seed consumes another gallon, and we need to allow 2 gallons for machinery manufacturing and maintenance.

So far we have consumed 31.5 gallons of diesel. Drying corn from 22 percent moisture to a safe storage level requires 0.09 gallons per bushel, or about 14.5 gallons for a 160 bushel crop. Total gallons to grow an acre of Iowa no-till corn, then, comes to 46 gallons of diesel, which is roughly equivalent to the energy in 1.1 barrels of crude oil. The oil industry says on average it takes one barrel of oil to extract and refine 10 barrels, so add 0.1 barrels to our total and convert to Calories — 1,752,000 Calories to grow an acre of no-till corn.

Now, how much sun energy did that 1.2 barrels of crude oil capture? A pound of corn kernels contains 1,550 Calories. There are 56 pounds in a bushel and we are growing 160 bushels, well below the average of recent years. Total pounds per acre computes to 8,960, which multiplied by 1,550 gives a total Calorie production of 13,880,000. Dividing Calories of corn produced by Calories in a barrel of crude oil (1,460,000) equals the equivalent barrels of crude oil captured by photosynthesis: 9.5! But wait, there’s more. It takes a pound of stover (foliage and cobs) to produce a pound of kernels, and the stover contains as much energy per pound as the grain, so double the output to 19 barrels. And for every pound of stover, add a quarter pound of roots — another 2.3 barrels of captured energy.

So the 1.2 barrels of expended energy captured a total of 21.3 barrels of photosynthetic energy! An output-input ratio of 17.8 to 1! One Calorie of oil energy produced 9.5 Calories of food energy (grain only) and 11.8 Calories of refuse energy (roots and stover) to feed the soil biota and sequester some carbon in organic matter. If only 10 percent of the refuse energy is permanently stored as recalcitrant organic matter (humus), more carbon will have been returned to the earth than was removed to grow the corn.

The net energy from the grain, 8.4 barrels per acre, can now enter the economy as new wealth to be exploited for food, feed, ethanol and miscellaneous products for the benefit of consumers. If all acres were no-tilled, the energy gain from the 90 million acres American farmers normally grow would mean a whopping energy input into the economy equal to 756 million barrels of oil. New wealth, sustainably produced when grown using the best modern technologies, to be used in over 10,000 different products. Not all acres are no-tilled, but if energy input is increased 10 percent to 1.32 barrels the net energy gain is only reduced 11 barrels. In my view, corn is a hero of our economy, not a villain.


Jack DeWitt is a farmer-agronomist with farming experience that spans the decades since the end of horse farming to the age of GPS and precision farming. He recounts all and predicts how we can have a future world with abundant food in his book “World Food Unlimited.” This article was republished from Agri-Times Northwest with permission.

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