For at least the third year in a row the predictions of a record sized dead zone in the Gulf of Mexico have failed to appear. Researchers were predicting that the dead zone would measure 8,500 square miles this year and many articles proclaimed that the sure to be record was because of increased ethanol production.
According to figures released today by NOAA the zone encompasses about 3,000 square miles (7,770 square kilometers), less than half the size scientists had forecast last month, when they estimated it would be as large as 8,500 square miles, or about the size of the state of New Jersey, NOAA said in a release. That is a long way from the record set in 2002 which was also 8500 miles. Makes you wonder what kind of science those guys are using.
It looks like 2009 will be a record year for ethanol production and the latest figures even suggest a possible record for consumption. The theory that corn ethanol is the cause of the large Gulf Dead Zones is nothing more than a theory.
When you look at the real facts there is also no clear evidence of a relationship between nitrogen used for corn and the size of the seasonal hypoxic zone. In recent years, as corn production has become more efficient and yields have increased, the nitrogen removed from corn fields in the grain may equal or exceed the amount of nitrogen applied in the fertilizer.
Lets take a closer look.
There are several sources of nitrogen that contribute to algae growth in the Gulf.
1) Natural sources such as fixation, soil, etc.
2) Agricultural sources such as fertilizer application
3) Industrial sources such as waste water treatment
4) Municipal sources such as sewage, golf courses, and run-off from lawns, etc.
There has been considerable finger-pointing at agriculture as the source of N and, in particular, at corn because the total N application is relatively high.
However, since corn yield has increased considerably over the years then the nitrogen removed in the grain will have increased, thereby, resulting in a large increase in nitrogen use efficiency in corn.
It should be noted that between 1970 and 1980 the N removed was just over 50% of the applied N. However, as yields corn increased without a corresponding increase in applied N, the ratio gradually improved until, for 2007, the N amount removed in the grain is about equal to the N amount applied.
Therefore, under present day cultural practices, the net balance for N applied and N removed in corn is such that there is no excess N available due to fertilizer use. The conclusion then is that any change in N entering the Gulf, over time, is probably not related to the use of fertilizer N for corn.
OK, what about other possible sources?
The amount of N flowing through the Mississippi-Atchafalaya River Basin (MARB) that originates from sewage has likely increased by a considerable amount. While difficult to calculate the exact number, we can assume that N output per person is relatively constant, while the population within the Mississippi watershed increased by 22% between 1970 and 2000.
Another source that is linked to population and the expansion of homes is that from the N applied to lawns.
The estimated area for lawns, which includes golf courses and other commercial grass areas, in 2005, was ~64K sq miles = 41 MM acres across the U.S. We estimate that 60% of the area falls within the MARB, which would be 24.6 MM acres of lawns.
So as you can see there are many sources of N that may end up in the Mississippi watershed. But to lay the blame on corn ethanol is just plain wrong.
Of course we know the tactics of the anti-ethanol crowd. Spin and hype. So called studies that are nothing more than computer models filled with wild worse case scenarios that have never and never will happen.