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EPA Science Advisory Board Suggests Revisions to Ethanol Incentives Necessary to Reduce Gulf of Mexico “Dead Zone”

The Mississippi and Atchafalaya River Basin is one of the largest river systems in the world, drains approximately 40% of the contiguous Unites States and is the largest contributor of freshwater and nutrients to the northern Gulf. Click to enlarge. Source: Rabalais.

A draft report from the Science Advisory Board (SAB) to the US Environmental Protection Agency suggests that changes to the current structure of economic incentives favoring corn-based ethanol may be necessary to prevent a dramatic increase in nutrient loadings in the Mississippi and Atchafalaya River Basin (MARB) that would lead to an expansion of the annual “Dead Zone”—a hypoxic region in the Northern Gulf of Mexico (NGOM).

For more than 20 years, scientists have been documenting the annual appearance and expansion of a hypoxic zone—an area of low dissolved oxygen (<2 mg/L) that cannot support marine life—in the Gulf. The average size of the zone is increasing, with the exception of heavy hurricane years (such as 2005 with Katrina and Rita).

The hypoxic zone in July 2007. Click to enlarge. Source: LUMCON

Marine species either die or flee the hypoxic zone, so the spread of hypoxia reduces the available habitat for marine species which are important for the ecosystem as well as commercial and recreational fishing in the Gulf.

To address this problem, the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force asked the White House Office of Science and Technology Policy to conduct a scientific assessment of the causes and consequences of Gulf hypoxia through its Committee on Environment and Natural Resources (CENR). In 2000 the CENR completed An Integrated Assessment: Hypoxia in the Northern Gulf of Mexico, which formed the scientific basis for the Action Plan for Reducing, Mitigating and Controlling Hypoxia in the Northern Gulf of Mexico. The plan called for a reduction in the size of the zone to 5,000 km2 by 2015. The task force committed to implement ten management actions and to assess progress every five years; it began its first reassessment in 2005.

As part of that reassessment, EPA’s Office of Water, on behalf of the task force, requested the SAB to convene an independent panel to evaluate the state of the science regarding hypoxia in the Northern Gulf of Mexico and potential nutrient mitigation and control options in the MARB.

Area of the mid-summer hypoxic zone. Click to enlarge.

According to the draft SAB report, while the scientific understanding of the causes of hypoxia have grown, actions to control hypoxia have lagged. Mapping by the Louisiana Universities Marine Consortium (LUMCON) in July 2007 determined that the size of the zone had increased to 20,500 square kilometers (or 7,900 square miles), similar to the size of New Jersey. The low oxygen waters extended from near the Mississippi River across the Louisiana/Texas border towards Galveston.

The long-term average since mapping began in 1985 increased with this year’s measurement to 13,500 square kilometers (or 5,200 square miles). The goal to reach the 5,000 km2 target size continues to remain far off, concluded LUMCON.

In its report, the SAB panel found indications that the Gulf of Mexico has undergone a regime shift with hypoxia such that the system is more sensitive now to inputs of nutrients than in the past, with the resulting induction of a larger response in hypoxia.

To reduce the dead zone to the target size of 5,000 km2, the SAB draft report recommends a dual nutrient strategy targeting at least a 45% reduction in riverine total nitrogen flux and at least a 45% reduction in riverine total phosphorus flux.

However, the report cautions, “certain aspects of the nation’s current agricultural and energy policies are at odds with the goals of hypoxia reduction and improving water quality”—specifically, the emerging national strategy on renewable fuels that grants economic incentives to corn-based ethanol production.

Existing incentives could lead to corn production on an additional 16 million acres, which would “dramatically” increase nitrogen loadings to the MARB. The SAB report identifies the most significant five opportunities for reducing nitrogen and phosphorus loading in the Mississippi:

  • Conversion to alternative cropping systems (e.g., using perennials or alternative rotation systems) and promotion of environmentally sustainable approaches to biofuel production in targeted areas of the basin;

  • Improved management of nutrients by emphasizing infield nutrient management efficiency and effectiveness to reduce losses;

  • Construction and restoration of wetlands as well as criteria for targeting those wetlands that may have a higher priority for reducing nutrient losses;

  • Introduction of tighter nitrogen and phosphorus limits on municipal point sources;

  • Improved targeting of conservation buffers, including riparian buffers, filter strips 40 and grassed waterways, to control surface-borne nutrients.

The Science Advisory Board will vote on approval of the draft report in December.



Rafael Seidl

You could substantially reduce fertilizer input by equipping harvesting machines with GPS receivers and creating high-resolution maps of crop yields. Even on a single field, there are variations in how much fertlizer is actually needed at any given location. Improved packaging mechanisms for the fertlizer pellets would also be welcome, e.g. variations on the slow-release technologies used in certain detergents and pharmaceuticals. Surface run-off would also be reduced if fertilizer were applied at the time of ploughing, rather than concurrently with seeding. Plants do a decent job of ferreting out nutrient-rich pockets of soil with their root systems.

Or, you could ramp down the subsidy of $0.51 per gallon of ethanol and the $0.54 per gallon tariff on imported ethanol. Both of these are politically popular in the region but severely distort the market for biofuels, to the point of causing food prices in Mexico to skyrocket and fisheries on the Gulf coast to effectively disappear.

Someone Who's Worked on a Farm

Your suggestions are completely unrealistic. It's impossible to determine the cause of variations in yield in a single field in a commercial setting. Was it not enough fertilizer? Was it not enough water? Was it pests or volunteer crops? Were the seed bad (the seed farmers buy is not guaranteed 100% uniform)? In addition, a lot of farming is done via no-till and thus there is no ploughing of the land. Furthermore, if you fertilize at plough you have to plant very soon after unless you want volunteer (weeds) to make use of the fertilizer instead of your crop. That implies more equipment and labor to farm a given area of land and more weather risk.


Could we park some large barges in this zone and start harvesting algae? Mine it for biodiesel. At the same time get rid of the farm subsidies that make corn so bloody profitable.


GPS receivers on mobile farm equipment have been used for almost ten years here. An aquaintance who sells tractors etc tells me that satellite imaging of the fields can detect shifts in color that infer different crop yield with a resolution of several yards. Data is supplied to farmers that is interpreted by the on board computer in conjunction with data from the GPS. With the tractors driven at constant speed the seed drills will speed up and down depending on the data from last years photo-images. There is similar bio-feedback practised with the fertilising operation so that the more fertile land is not over fertilised. As you would guess the aim is to get a more uniform crop yield.

I don't know how effective all this is or how they separate the variables. I am just reporting that farmers are getting with the program.


Good news for cellulosic ethanol.


They had an article on the PBS News hour about how corn ethanol is good for farmers income and how much water it takes to grow and the distillers dry grain produced. It was a pretty good overview for a few minutes and they talked about cellulose ethanol as well. I thought that I would mention this to show that some education of the general population IS getting out there.


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