|Scatterplot of Net GHG and Net Energy Value results from the EBAMM model. Note Cellulosic ethanol to the right. Click to enlarge.
A new analysis by researchers at the University of California, Berkeley concludes that the production of ethanol from corn uses less petroleum energy than the production of gasoline. However, they also conclude that the reduction in greenhouse gases derived by using corn ethanol as a fuel is smaller than some thought—between 10% to 15%.
The researchers note that new technologies now in development such as those for the production of cellulosic ethanol promise to make ethanol a truly green fuel with significantly less environmental impact than gasoline.
The UC Berkeley study, published in this issue of Science, deconstructed six separate high-profile—and contradictory—studies of ethanol. They assessed the studies’ assumptions and then reanalyzed each after correcting errors, inconsistencies and outdated information regarding the amount of energy used to grow corn and make ethanol, and the energy output in the form of fuel and corn byproducts.
It is better to use various inputs to grow corn and make ethanol and use that in your cars than it is to use the gasoline and fossil fuels directly. The people who are saying ethanol is bad are just plain wrong.
But it isn’t a huge victory—you wouldn’t go out and rebuild our economy around corn-based ethanol.—Dan Kammen, co-director of the Berkeley Institute of the Environment and UC Berkeley’s Class of 1935 Distinguished Chair of Energy
The goal of the UC Berkeley analysis was to understand how six studies of fuel ethanol could come to such different conclusions about the overall energy balance in its production and use. Kammen and Alex Farrell of the Energy and Resources Group at UC Berkeley, with their students Rich Plevin, Brian Turner and Andy Jones along with Michael O’Hare, a professor in the Goldman School of Public Policy dissected each study and recreated its analysis in a spreadsheet where they could be compared side-by-side.
The studies reviewed were:
Fossil Energy Use in the Manufacture of Corn Ethanol; Dr. Michael S. Graboski, Colorado School of Mines, Prepared for the National Corn Growers Association (2002)
The Energy Balance of Corn Ethanol: An Update; Hosein Shapouri, James A. Duffield, and Michael Wang; U.S. Department of Agriculture, Agricultural Economic Report No. 814 (2002)
The 2001 Net Energy Balance of Corn Ethanol; Shapouri, H., Duffield, J., Mcaloon, A.J.; Proceedings Of The Conference On Agriculture As A Producer And Consumer Of Energy, Arlington, VA (2004)
The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model, version 1.6; Michael Wang, Transportation Technology R&D Center, Argonne National Laboratory
“Thermodynamics of the Corn-Ethanol Biofuel Cycle”; Patzek, T.W.; Critical Reviews in Plant Sciences 23(6), 519-567 (2004)
“Ethanol as Fuel: Energy, Carbon Dioxide Balances, and Ecological Footprint”; Marcelo E. Dias de Oliveira, Burton E. Vaughan, and Edward J. Rykiel, Jr.; BioScience, 55(7), 593 (2005)
“Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower”; David Pimentel and Tad W. Patzek; Natural Resource Research, 14(1), 65-76 (2005)
The UC Berkeley team has made its spreadsheet model, the Energy and Resources Group Biofuels Meta Model (EBAMM), available to the public on its Web site.
The team said it found numerous errors, inconsistencies and omissions among the studies, such as not considering the value of co-products of ethanol production—dried distillers grains, corn gluten feed and corn oil—that boost the net energy gain from ethanol production. Other studies overestimated the energy used by farm machinery.
On the other side, some studies ignored the use of crushed limestone on corn fields, which can be a significant energy input because of the need to pulverize the rock. Farrell noted that some numbers needed for the analysis, such as the amount of limestone applied, are just not known reliably. On the other hand, some of the studies used outdated data when more recent numbers were available, making ethanol look worse.
The UC Berkeley team calculated a Net Energy Value (Output energy - Input energy) for corn ethanol of 4.5 MJ/Liter. Cellulosic ethanol fares much better, with a calculated Net Energy Value of 22.8 MJ/L.
Farrell, Kammen and their colleagues considered not only the energy balance of corn ethanol production, but also the effect on the environment through production of greenhouse gases. While corn ethanol came out marginally better than gasoline in terms of greenhouse gas production, Farrell noted that corn production has other negative environmental impacts associated with fertilizer, pesticide and herbicide use. These need to be taken into account when considering the balance between corn ethanol and gasoline, though emerging cellulosic technologies using waste would push the equation more toward ethanol.
Two things are going to push the commercialization of cellulosic technology. One is driving the cost down, which is mainly research and development; the other is that environmental concerns are increasingly entering into commercial calculations about biofuels."—Alex Farrell
Kammen estimates that ethanol could replace 20% to 30% of fuel usage in this country with little effort in just a few years. In the long term, the United States may be able to match Sweden, which recently committed to an oil-free future based on ethanol from forests and solar energy.
Kammen last year published a paper, also in Science, arguing that even Africa could exploit its biomass to build a biofuel industry that could meet energy needs for the poor and develop a sustainable local fuel supply, a future much better than using fossil fuels.
“Ethanol can contribute to energy and environmental goals”; Farrell, A.E., R.J. Plevin, B.T. Turner, A.D. Jones, M. O’Hare, and D. Kammen; Science, 311. 506 - 508 (2006)