Biofuel targets conflict with plans to protect Gulf of Mexico

Fish and boxing gloveMeeting US goals for biofuel production will increase nutrient run-off to the Gulf of Mexico, making it more difficult to reduce the size of the gulf’s “dead zone,” scientists say in Environmental Science & Technology.

US energy policy dictates that 36 billion gallons of renewable fuel must be produced annually by 2022. But a task force led by the Environmental Protection Agency is also aiming to shrink the Gulf of Mexico’s hypoxic zone, a low-oxygen area that can reach 14,600 square kilometers. Excess nitrate from agricultural run-off is thought to play a large role in hypoxic zone formation, which kills and disrupts marine life each year.

The authors calculated the nitrate output of various crop combinations that could be used to meet the US biofuels mandate. Relying on crops for cellulosic ethanol, such as switchgrass, rather than corn would cut nitrate output by 20 percent, they found. But that still wouldn’t be enough to reach the EPA’s goal of reducing the hypoxic zone to 5,000 square kilometers by 2015, the team concluded.

To meet that target, the US will need to undertake an “aggressive nutrient management strategy,” they say. Possible solutions could include constructing wetlands or building buffer zones to intercept run-off. – Roberta Kwok

Source: Costello, C., Griffin, W., Landis, A., & Matthews, H. (2009). Impact of Biofuel Crop Production on the Formation of Hypoxia in the Gulf of Mexico Environmental Science & Technology DOI: 10.1021/es9011433

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