CLIMATE change could prevent the U.S. from meeting the biofuel targets set in the renewable fuel standard (RFS), according to a study from Rice University and the University of California-Davis (UCD).
The study, which was published in the journal Environmental Science & Technology, suggests that in 40 years, a warmer planet will reduce corn yields by an average of 7% while increasing the amount of irrigation needed by 9%.
According to Pedro Alvarez, chair of the department of civil and environmental engineering at Rice University, those effects would likely preclude the U.S. from meeting its goal of blending 15 billion gal. of ethanol into the fuel supply by 2022, as mandated by the RFS.
Furthermore, he said the implications for water usage could outweigh the environmental benefits of replacing petroleum with biofuels.
"Whereas biofuels offer a means to use more renewable energy while decreasing reliance on imported oil, it is important to recognize the trade-offs," Alvarez said. "One important unintended consequence may be the aggravation of water scarcity by increased irrigation in some regions."
Alvarez has questioned the wisdom behind the RFS before.
Alvarez previously published a white paper with Rice's Baker Institute for Public Policy that reported "no scientific consensus on the climate-friendly nature of U.S.-produced corn-based ethanol." The paper concluded that U.S. biofuel policy had numerous economic, environmental and logistical shortcomings.
In announcing the new study, the authors referred to a 2009 article in the same journal that suggested that the volume of water used to produce ethanol is already unsustainable. That article noted that it takes 50 gal. of water to grow enough corn in Nebraska to produce the amount of ethanol needed to drive a single mile.
The Renewable Fuels Assn. (RFA) questioned that logic, however. Citing data from the Water Footprint Network, RFA compared the volume of water used to produce ethanol to the water requirements for producing other sources of energy.
"The average dry-mill ethanol biorefinery uses 2.7 gal. of water per gallon of production; that's 47% less than in 2001," according to the RFA website. "By comparison, it takes 40 gal. of water to produce one cup of coffee, 4 gal. for a pound of hamburger, 11.6 gal. to produce a pound of chicken and 300 million gal. to produce just one day's worth of the newspapers across the country."
Running computer simulations based on crop data from the nation's top 10 corn-producing states, the Rice and UCD researchers overlaid the crop data with climate change models predicting regional levels of atmospheric carbon dioxide, temperature and precipitation to project how those factors might affect corn production. They concluded that Corn Belt states will be subject to more intense but less frequent precipitation during the growing season.
Maintaining crops in that environment would require a 5-25% increase in irrigation. For corn-producing states that already rely on irrigation, the report claims that crop yields will decline regardless of increased irrigation. The researchers further noted that the 2012 drought greatly damaged cropland in the Great Plains and suggested that aquifers used for irrigation are beginning to run dry.
The nation's corn growers were not impressed with the Rice/UCD study. The National Corn Growers Assn. (NCGA) pointed out that Alvarez has long been a critic of the RFS and noted that the policy only covers renewable fuels for the next nine years, not the 40 years projected in the Rice/UCD study.
"Looking back 40 years, corn farming was so different in 1973 than it is today, and it's a difference that could not have been predicted then," NCGA president Pam Johnson said. "The fact of the matter is, it's not only naive to assume that corn yield will not increase as it has been, but our current average yield is already sufficient to produce the 5 billion bu. needed to meet the full conventional RFS volumes."
Johnson pointed out that even in the face of the historic drought in 2012, farmers harvested the eighth-largest corn crop on record and saw a significant yield increase over the last significant drought year.
"We encourage academics to get out of their ivory towers and learn what farmers are really doing instead of simulating information that is basically useless," she said.