With debates over ethanol heating up on the Hill again, the National Corn Growers Association offers a comparison the environmental impacts of ethanol and petroleum as transportation fuels. Scientifically examining a wide array of environmental factors, this side-by-side evaluation offers insight into the important differences between these fuels.

Which fuel is renewable and why is that important?

  • Today, ethanol is primarily made from corn, which is produced annually and thereby renewable.

When corn grows, it takes carbon dioxide from the air and converts it into glucose and then starch, from which ethanol is produced. Corn production returns nutrients to the soil through its roots and decomposing stalks, thus giving back to the land used in its production.

  • Petroleum and natural gas were made over millions of years ago from decayed plants and animals. The amount present in the earth is limited, and it cannot be replenished.

As it takes tens of thousands of years for the planet to create more petroleum, it simply runs out once the current supply is exhausted. Once removed, the molecules containing carbon and other substances, like sulfur, are released into the environment. Unlike ethanol, petroleum is simply a product extracted from the planet and not one that gives back a valuable resource. 

From a scientific standpoint, what actually makes up these fuels? What affect do they have on life prior to being used as fuel?

  • Ethanol is a tiny single substance that is non-toxic. It can be enjoyed by adults in alcoholic beverages or as a transportation fuel.
  • Petroleum is a mixture of hundreds of different molecules. It is toxic to biological organisms.

How does production of the fuel's feedstock impact the environment and the global population?

  • Corn used for ethanol in the United States is grown on approximately five percent of our nation's cropland. For perspective, ethanol production uses less than three percent of all grain crops grown over the entire world.
  • Petroleum is mined across the entire globe and must be extracted from deep underground. In order to collect petroleum, landscape fragmentation and the generation of toxic, hazardous and potentially radioactive waste streams often occurs.

Understanding that the distance the feedstock must travel from production to where it will be made into a useable fuel requires fuel use, how does the environmental impact of ethanol and petroleum production compare? What does it really take to make the fuel?

  • Most corn-to-ethanol production facilities are located within 15 miles of the farms where the crop was produced.

Yeast, similar to that used to make bread, converts the corn starch into ethanol. In addition, two co-products, corn oil and distillers grains, are produced. These co-products are used in multiple places, including biodiesel production and animal feed.

  • Since petroleum extraction happens across the globe wherever deposits can be found, it must be shipped to a facility where it can be refined. Once there, the energy intensive refining process separates these various molecules into fractions; each fraction can be used for many purposes.

What sort of air and water pollution do these fuels cause?

  • Since 2005, non-toxic ethanol has replaced groundwater contaminant MTBE as the fuel ingredient used to increase octane.
  • Petroleum refiners use quite a bit of energy to separate aromatic components and very high boiling fractions for the octane needed for fuel. Many of the substances produce particulate substances leading to asthma and other health-related problems.

What type of waste is produced in the manufacture of these fuels? How do they compare in respect to the greenhouse gases emitted in the production of these fuels?

  • Based on the results of scientific testing, the EPA considers corn starch ethanol as producing 23 percent less greenhouse gas emissions compared to making and burning gasoline from petroleum. Recent evidence shows multiple ways of producing ethanol with 50 percent or less GHG compared to gasoline production.
  • The U.S. oil and gas industry generates more solid and liquid waste than municipal, agricultural, mining and other sourcescombined.

Since the RFS was first enacted how has increased ethanol use benefitted the United States?

In 2005 and again in 2007 with the enactment of the Energy Independence and Security Act, the government chose to promote the increased production of ethanol for several reasons including lower its GHG emission properties, its renewable nature and as it decreases reliance on foreign oil. Ethanol production and use is estimated to have reduced greenhouse gas emissions by 100 million metric tons in 2012. In one year, that reduction is equivalent to removing 20.2 million light duty vehicles from the highways.  Draft studies estimate a cumulative reduction of over 150 million tons of carbon dioxide emissions in the United States between the enactment of the original RFS legislation in 2005 and 2012.

  • Since the enactment of the original RFS in 2005, America's oil demand has decreased, and national oil import dependence has fallen from 60 percent to 45 percent.

In 2010, U.S. oil imports fell below 50 percent for the first time since 1997. Multiple factors contributed to the decrease in petroleum usage including the increased use of ethanol, the high cost of oil and increased vehicle efficiencies.

Looking at how the production of these fuels compares side-by-side, it becomes evident that ethanol is truly renewable and produced in a greener manner than its fossil fuel counterparts. Where petroleum creates reliance upon a fuel pulled from the ground and imported from abroad, ethanol improves our environment while increasing our national and energy security.