Ethanol stirring concerns along Gulf Coast Ethanol stirring coastal concerns

As production rises, so does the threat of the Gulf's dead zone

The recent passage of the mammoth energy bill could have unintended consequences for the Gulf of Mexico that have nothing to do with oil and gas platforms.

Under the law, production of ethanol is set to increase five-fold to 36 billion gallons a year by 2020.

Some environmentalists are worried that the shift to ethanol — viewed as a home-grown alternative to foreign oil — could enlarge the northern Gulf's "dead zone," an 8,000-square-mile area so devoid of oxygen that fish, shrimp and other sea life cannot survive.

Already ethanol, by doubling corn prices since 2002, has driven corn production to its highest levels since World War II. Growing corn requires considerably more nitrogen-based fertilizer than most crops. When the fertilizer runs off fields in the Midwest, it drains into the Mississippi and eventually reaches the Gulf of Mexico.

"This year's dead zone is the third highest on record, and I think we're already seeing an impact from increased ethanol use," said Donald Scavia, a University of Michigan professor who studies farm practices and hypoxia, or low-oxygen water.

Scientists say the Gulf's dead zone has grown larger since its discovery more than 20 years ago. According to Nancy Rabelais, a professor with the Louisiana Universities Marine Consortium who annually surveys the area, the dead zone has been about 15 percent bigger in the last five years than normal.

But not all scientists are ready to blame increased corn farming for that growth, at least not yet.

"It's something we should be wary of and keep an eye on, but it's not something we should jump to conclusions on," said Steven DiMarco, an assistant professor at Texas A&M University who specializes in dead zone research.

"It could be a number of years before the nitrate makes its way from the Midwest into the Gulf. And once there, it may make the dead zone bigger, or last longer. Or it may do nothing at all. We just don't know yet."

Nitrates reaching the Gulf set into motion a chain of events to create a dead zone, DiMarco said.

The excess nitrogen produces booming populations of algae, which feed upon the nutrient. This algae then dies and sinks to the bottom of the sea, where it decays and is eventually consumed by bacteria that breathe oxygen. The bacteria population multiplies, depleting the oxygen available for other species.

The Gulf's dead zone typically forms near the Mississippi River's mouth because, in addition to nitrate, an influx of fresh river water is required for its creation. Fresh river water is less dense than salt water, and the two, like oil and water, don't mix. For that reason, oxygen at the surface is not transported to the salt water below where marine organisms live.

Dead zones are most prominent in summer, when winds, which aid in mixing, are weakest. Strong frontal systems in the fall generally break them up.

A report published by the National Academy of Sciences in October, Water Implications of Biofuels Production in the United States, concluded that hypoxia is among the chief water-quality concerns raised by ethanol production.

"If not addressed through policy and technology development, this effect could accelerate," the report concluded.

Jon Devine, a clean water specialist with the environmental group Natural Resources Defense Council, said the new energy law contains provisions to monitor and study the environmental aspects of ethanol, including hypoxia.

"As the bio-energy economy starts to expand, it's going to be important for Congress to invest in making sure we're not trading one set of environmental harms for another," he said.

To that end, Devine said new farming legislation should beef up programs to manage water quality, such as providing funds to create buffer zones around large corn farms and restore wetlands, which can naturally remove nitrogen from the water before it reaches large rivers.

eric.berger@chron.com