Monday, March 10, 2008

Corn ethanol production will worsen the Dead Zone

A new paper by my colleague Chris Kucharik and I looks at the new US Energy Policy, will calls for growing more corn to produce ethanol, will affect the "Dead Zone" in the Gulf of Mexico. For a quick summary, see Reuters, the CBC or AFP (or my 15 Minuten ruhm on German ARD). Wired and Scientific American go into more detail.

The Mississippi dumps a massive amount of nitrogen, largely in the form of the soluble ion nitrate, into the Gulf each spring. It promotes the growth of a lot of algae, which eventually sinks to the bottom and decomposes. This consumes much of the oxygen in the bottom waters, making life tough for bottom-dwelling fish and creatures like shrimp. The Dead Zone has reached over 20,000 km2 in recent years.

The primary source of all that nitrogen is fertilizer applied to corn grown in the Midwest and Central US. Reducing the Dead Zone to less than 5000 km2 in size, as is suggested in US policy, will require up to a 55% decrease in nitrogen levels in the Mississippi.

The new US Energy Policy calls for 36 billion gallons of renewable fuels by the year 2022. Of that, 15 billion can be produced from corn starch. Our study found meeting those would cause a 10-34% increase in nitrogen loading to the Gulf of Mexico.

Meeting the hypoxia reduction goal was already a difficult challenge. If the US pursues this biofuels strategy, it will be impossible to shrink the Dead Zone without radically changing the US food production system. The one option would be to dramatically reduce the non-ethanol uses of corn. Since the majority of corn grain is used as animal feed, a trade-off between using corn to fuel animals and using corn to fuel cars could emerge.


Anonymous said...

Suggestions to fight the"Dead Zone":
1-Collect the algae before it dies and decomposes. Use it to fertilize fields or to feed animals.
2- Use buoys with pumps attached to them to either cause turbulence or pump air into the water. They could be powered by wave, current, wind or solar energy.

Anonymous said...

Simon, does this help?

Steve G.

Anonymous said...

The final 3 letters of the URL
are .htm

Steve G.

Simon Donner said...

Thanks for the link Steve. Our study is not an indictment of ethanol or biofuels, rather an analysis of the environmental effects of the preferred means of current ethanol production in the US (corn). If biofuels were being produced on marginal lands without chemical fertilizer or from wastes, the story would be very different.

garry peterson said...

Hi Simon

Cool paper, but your links don't work or are incorrect.

Simon Donner said...

The link is fixed - Thanks.

Jim's Words Music and Science said...

Simon, yuo state that your study is not an indictment of biofuels per se, but it really is. Farmers have using quit crop rotation in an effort to keep benefiting from ethanol subsidies. This leads to more artificial fertilizer being used, which leads to more runoff (and the dead zone). I have a number of related posts at Chemistry for a sustainable world. Best wishes, Jim