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| Fig. 1: Corn undergoes ethanol fermentation and distillation. (Courtesy of the USDA) |
Biofuels offer the opportunity to use organic material as an energy source. Unlike fossil fuels, plants are a renewable resource. Biomass can be converted into ethanol which is an alcohol that can be converted into energy.
Corn can be converted into ethanol as seen in Fig. 1. Corn-based ethanol is the most common type of ethanol. The fermentation of the sugars present in corn kernels produces the ethanol. The process starts with corn being harvested and milled to break down the kernels. The corn is then liquefied into a slurry and enzymes are added to break down the starch into fermentable sugars. During fermentation, yeast or bacteria is introduced to consume the sugars and produce ethanol. Once distilled, the ethanol can then be added to gasoline or other fuel blends.
In order to investigate corn ethanol's utility, we must consider how many acres of corn would be needed to power North America
In 2022, North America required a primary energy of 113.7 exajoules (1.137 x 1020 J). [1] A liter of ethanol contains 21.2 MJ (2.12 x 107 J). [2] From this we can calculate the liters of ethanol that will be produced.
| 1.137 × 1020 J 2.12 × 107 J L-1 |
= | 5.36 × 1012 L of ethanol |
We can then convert liters of ethanol to gallons of ethanol and then convert gallons of ethanol to acres of ethanol with the conversion rate of 462 gallons/acre: [3]
| 5.36 × 1012 L ×
0.264 gal L-1 462 gal ac-1 |
= | 3.06 x 109 ac |
As can be seen from my calculations, North America would require a staggering amount 3.06 × 109 acres of land to produce enough corn ethanol to be powered. To put things in perspective, the entire United States Corn Crop is 9.4 × 107 acres. [4] This includes corn grown for consumption as well as for biofuel. The amount of arable land in the United states is limited and is needed to produce food. Due to the large amount of land required to produce corn ethanol, it becomes difficult to balance growing biomass for ethanol production and food for consumption. It is important to recognize this limitation that comes with biofuels. As technology progresses, it may become possible to grow corn more efficiently, lowering the required acreage and making corn ethanol a much more feasible option.
© Shay Nair Sharma. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "BP Statistical Review of World Energy 2022," British Petroleum, June 2022.
[2] R. Prakash, A. Henham and I. K. Bhat, "Net Energy and Gross Pollution From Bioethanol Production in India," Fuel 77, 1629 (1998).
[3] D. Hofstrand, "Brazil's Ethanol Industry," Iowa State University, January 2009.
[4] "Acreage," U.S. Department of Agriculture, June 2023.d