Some Corn Math
Feb 12, 2010
How much CO2 does the U.S. corn crop remove from the atmosphere? Let's do the math. The molecular formula of starch and cellulose is C6 H10 O5. The molecular weight of carbon is 12, the molecular weight of hydrogen is 1, the molecular weight of oxygen is 16. Thus for C, 6 X 12 = 72; for H, 10 X 1 = 10; for O, 5 X 16 = 80 and the total weight of this molecule is 162. The percentage of carbon in this molecule is 44.4%. The molecular formula for carbon dioxide is CO2. Thus for C, 1 X 12 = 12 ; for O, 2 X 16 = 32 and the total weight of this molecule is 44. The percentage of carbon in this molecule is 27.2%.
For plants to produce a tonne of starch and cellulose, they would have to source 888 kg of carbon. Farmers do not fertilize with carbon or carbon dioxide. They get this carbon from the air in the form of carbon dioxide. To get 888 kg of carbon from the air would require (44.4 divided by 27.2 equals 1.63) 2000 X 1.63 = 3264.7 kg of CO2. A fat molecule of C55 H98 O6 would be 77% carbon requiring 1545 kg of C from the air to produce a tonne of fat. This would require 2.83 X 2000 = 5661 kg of CO2 from the air.
This year, American farmers produced 13,000,000,000 bu. or 330,000,000 million tons of corn. They will have produced (330,000,000 - 39,600,000 [of moisture]) = 290,000,000 tonnes of starch, cellulose, fat, and protein. Protein has significant quantities of carbon. When the starch and cellulose figures are used, they suggest that 290,000,000 X 1.63 = 473,000,000 tonnes of CO2 from the air. That's 1½ tonnes of CO2 removed from the atmosphere for every person in the U.S. Corn plants also have roots, stems and leaves, which are also made of cellulose, which is 44% carbon. This may double the amount of CO2 taken from the air. The carbon in these forms is released as CO2 when these plants decompose in the soil.
Carbon has a cycle. American farmers also produce soybeans, wheat, grass for beef, forage for dairy, grain for eggs and chicken, barley for beer, apples, vegetables, racehorses and other products. Perhaps American farmers are taking 2,000,000,000 tonnes of CO2 from the air. The carbon that we consume in the form of wheat gets released back to the atmosphere in the CO2 that we exhale. True, carbon sinks are not that common. Injecting CO2 into the earth may keep it there for a while. Carbon can be captured in the form of limestone rock. This is a slow process which could see the end of carbon-based life forms. Some people talk about the carbon loss when the prairie soils were broken up. A nitrogen-deficient, root-bound patch of prairie sod will not consume nearly the quantity of CO2 that a well-managed crop of corn will.