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Corn ethanol can cause more greenhouse pollution than gasoline

Since corn takes carbon dioxide from the air as it grows, returning that CO2 to the atmosphere by burning corn ethanol seems like it should cause no net greenhouse pollution.  However, the picture is more complicated than this.

For every 10 gallons of corn ethanol made, about 8 gallons’ worth of fossil fuel energy from coal, gas or oil is required to run farm machinery, make fertilizer, process corn into ethanol, and more.  That still makes corn ethanol about 20% more efficient than gasoline in terms of CO2 emissions—if the story were to stop there.

However, if new land is cleared to farm extra corn to make ethanol—or in response to the reduction in food crop acres caused by using corn for fuel instead of food—the carbon released by this activity could lead the emissions connected to corn ethanol to top emissions from simply using gasoline, depending upon the quantity and quality of the land cleared.