Ethanol’s Contribution to a Record-Breaking Dead Zone in the Gulf of Mexico

Earlier this month, the National Oceanic and Atmospheric Administration observed the largest “dead zone” in the Gulf of Mexico since record-keeping began in 1985. At 8,776 square miles, the dead zone is the second largest in the world and approximately the size of New Jersey.

Dead zones, also known as hypoxic zones, are areas in the ocean where algal blooms caused by pollution lead to low oxygen concentrations – causing marine life to suffocate and die. The algal blooms prevent sunlight and oxygen from reaching below the water’s surface, and are fatal to most aquatic life, including plants, fish, marine mammals, and shorebirds.

Contributors leading to these inhospitable conditions include excessive nutrient pollution, which often comes from nitrogen-based fertilizer runoff used in agricultural production. In particular, corn production is notorious for its significant contribution to the dead zone. Unlike other crops, corn cannot grow without fertilizer and thus has high volumes of nitrogen fertilizer runoff associated with its production.  Notably, scientists have been warning for years that increased production of corn-based ethanol would lead to a larger dead zone in the Gulf of Mexico.  

Corn production in the U.S. was at an all-time high in 2016, with domestic production reaching 15,148,038 bushels. The top corn-producing states in 2016 were Iowa, Illinois, Minnesota, Nebraska, South Dakota, Wisconsin, Texas, Ohio, North Dakota, Missouri, Kansas, Indiana, and Kentucky.  All of these states are located within the Mississippi watershed.  This means that nitrogen fertilizer runoff in these states flowing into local waterways will drain into the Gulf of Mexico.  

It is likely that increased production of corn, including corn for ethanol, has been a major factor in this year’s enormous dead zone. Of the total 2016 U.S. corn production, 36.5 percent (or 5.325 million bushels) was used for ethanol fuel and ethanol distillers dry grains (DDGs).  Indeed, production of corn-based ethanol has increased in the US since the Renewable Fuel Standard (RFS) was created in 2005.  Although the goal of the RFS, which mandates increased volumes of renewable fuels, was to replace carbon intensive petroleum-based transportation fuels with lower emission renewable fuels to address climate change, it has not achieved its climate change impact reduction goals and has had vast unintended adverse environmental impacts.  

Biomass-based diesel is one component that is not actually sustainable. In addition to the impact that corn production has on the dead zone in the Gulf of Mexico, producing corn for ethanol also has other adverse environmental impacts. Ethanol production is causing land conversion from other uses such as native grasslands and forests to cropland for corn production, leading to habitat and biodiversity loss. This includes loss of habitat for pollinators such as bees. In addition, a pesticide used in ethanol production, atrazine, is a suspected endocrine disruptor. The EPA has violated its legal duty to consult with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service on the impacts to federally protected species in connection with the agency’s  annual setting of renewable fuels volumes. For this reason, the Sierra Club has filed its notice of intent to sue the EPA over these issues.        

The U.S. Environmental Protection Agency has the capacity to address its violations. It also has the authority to reduce the mandated ethanol blend. Reducing the production of corn-based ethanol can restore habitats, protect biodiversity, and lessen the size of the dead zone in the Gulf of Mexico.   

Take action by telling the EPA to stop increasing the use of harmful corn ethanol.