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A Billion Dollars Flowing Down the Mississippi Annually

by December 20, 2011

In a recent post, I did a bit of research to update the picture of nutrient flows down the Mississippi due to runoff and other sources in its watershed. There’s been an ongoing debate about the source of the nutrients in the river that are directly linked to low-oxygen conditions in the Gulf of Mexico.

For a taste of the debate, check out the controversy a year ago surrounding the premier of Troubled Waters, A Mississippi River Story (link to view on Twin Cities Public TV). Among other activity, there was a heated back-and-forth on the opinion pages of the Minneapolis Star Tribune (first piece arguing that research for film was dubious, counter piece by producers about the research behind the film). The flare up nearly squelched the premier, although it ultimately took place.

Personally, I experienced how difficult it can be to establish a “consensus view” of how to describe nitrogen flows for the report on ecosystem indicators described in my previous post. There was a constant tension throughout the report process to “tell readers what to do with the information” rather than just “giving them the facts.” I believe we ultimately struck a good balance, however, we nearly had resignations of participants when we unintentionally pushed the line on the indicator dealing with the movement of nitrogen and got too close to pointing fingers.

For this post, I’m coming at the debate from a very different angle. Yes, there are multiple sources of the nitrogen in the Mississippi as it flows into the Gulf of Mexico. Sure, municipal sewage discharges should not be ignored, and I would argue they are not. Here’s a different question: if we had a way to dip a futuristic “nitrogen net” into the Mississippi just before it enters the Gulf, what would be the value of the recovered nitrogen (N)? A quick estimates suggests a lot: about one billion dollars worth of nitrogen!

Here’s the cost of anhydrous ammonia, the cheapest form of N-fertilizer (source: USDA’s Economic Research Service). These data are presented based on the cost of the N in the anhydrous (NH3). As an example, the 2011 cost of anhydrous is reported as $749 per ton; because each pound of NH3 has in it 82.4% N, then the cost of N per ton ends up being $910.

cost-of-anhydrous

So, let’s use a value of about $1000 per ton of N…the trend in cost suggests we might be there before too long. Looking back at the previous post, we saw that there were about one million metric tonnes of N flowing into the Gulf each year—here’s the graph again.

n-discharge-to-gulf

For this rough analysis, we can treat a metric tonne as equivalent to a regular U.S. ton (the conversion is 1.1). So, that means there’s about a billion dollars worth of N flowing into the Gulf of Mexico each year.

In a forthcoming post, I’ll dig into this further. Regardless of the source of this nitrogen, it seems like a huge opportunity. Either we need to figure out how to tighten things up so that the costly nutrients never make into our rivers, or some industrious soul should figure out that futuristic “nitrogen net” and reap dollars by the bushel.

Thumbnail image credit: U.S. Army Corps of Engineers on Flickr.


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