Sustainability of Biofuels: A Glimpse at the Magnitude of Fuel Consumption, Agricultural Production

To help frame the ongoing discussion of biofuel sustainability and the food-versus-fuel debate, we will present statistical information in terms that may help readers form their own opinions on the issue. We will use the USDA's most recent data, from 2006.

Let's begin with annual transportation fuel usage in the United States. According to the U.S. Energy Information Administration, approximately 138 billion gallons of gasoline and 53 billion gallons of No. 2 diesel fuel were sold in 2006.

Since ethanol as a gasoline replacement is pretty well known, we'll address it first. Two retail gasoline-with-ethanol products are typically sold: gasoline with 10 percent ethanol (E10) and gasoline with 85 percent ethanol (E85). The amount of ethanol required if all of the gasoline consumed in 2006 were either E10 or E85 would be approximately 13.8 billion gallons and 117.3 billion gallons, respectively. Assuming 1 bushel of corn is required to make three gallons of ethanol and assuming a yield of 150 bushels of corn per acre, approximately 31 million acres of cropland would be required in the E10 scenario and 261 million acres in the E85 scenario.

In 2006, the United States produced almost 5 billion gallons of ethanol, and at press time 9 billion gallons was projected to be produced in 2008. Knowing these production numbers leads one to believe that the E10 scenario is certainly achievable, if not a foregone conclusion. However, the E85 scenario would still be an extremely daunting challenge.

Another way to consider ethanol production is that, based on the crop yield and conversion numbers, corn yields approximately 450 gallons of ethanol per acre.

Now let's address biodiesel as a replacement for its petroleum counterpart, No. 2 diesel fuel. As presented earlier, the United States consumed approximately 53 billion gallons of No. 2 diesel fuel in 2006. Assuming each gallon of biodiesel requires 8 pounds of soybean oil, a soybean crop yield of 40 bushels per acre and 11 pounds of soybean oil in each bushel of soybeans, approximately 964 million acres of cropland would be required to replace all 53 billion gallons of No. 2 diesel fuel with biodiesel. These numbers translate into 55 gallons of biodiesel per acre of soybeans.

To further put these numbers into perspective, the USDA estimated the total U.S. cropland and active Conservation Reserve Program acres in 2006 to be approximately 455.6 million acres and 36.7 million acres, respectively.

The Energy Independence and Security Act of 2007 set a production goal of 36 billion gallons per year of biofuels by 2022, 21 billion gallons of which must be from cellulosic ethanol and other advanced biofuels. The question of whether we have enough land for food and fuel feedstock growth is left for further debate, but the answer probably lies in the level of the blend and the type of feedstock. Therefore, February's column will focus on nonfood types of biofuel feedstocks and the role they may play.

Brad Stevens is a research manager at the EERC. Reach him at or (701) 777-5293.