|Patrick Sutter (Dane County), Melissa Malott (Clean Wisconsin) and Jeff Endres (Farmer) discussing nutrient conservation plans in Wisconsin.|
Last month it was my great pleasure to be shown around Dane County farmland by county conservationists Patrick Sutter and David Merritt, and Melissa Malott of the conservation group Clean Wisconsin. Wisconsin is one of the many states that contribute to the nutrient pollution of the Mississippi and the Gulf of Mexico dead zone. With new state numerical limits on phosphorus pollution in waterways some interesting partnerships are forming. The water authorities must reduce the amount of phosphorus they release from sewage treatment, and there is a chance that it may pay for them to ask farmers to take action to reduce run off from their land.
One of the most interesting things I saw last month was a community nutrient digester run by a nice man called Monte Lamer, from the company Clear Horizons. Its basically a municipal sewage treatment works for cows, but with a twist. So each cow, I recall, produces the same amount of poo as 18 or 19 humans. So if you have thousands of cattle in an area (and Wisconsin does make a lot of cheese) you have a huge volume of manure, and nowhere to put it. On my tour one of the conservationists mentioned that some farmers had so much of the stuff that this year they were renting land just to store the vast quantities of manure their cows had produced.
Traditionally one spreads manure on the land. That is fine if cattle are at low densities. But these days with high-intensity farming and big agribusiness hard at work growing food all along the Mississippi watershed, there is more than the land can cope with in some places. Enter the manure biodigester. The basic idea is that the poo from all the cattle in an area is put into giant vats and fermented. This produces methane which is burnt to produce lots of lovely energy. Then the remaining bits of poo are dried into little bits which can then be applied as fertiliser to land that has insufficient nutrients.
Its an incredibly neat idea, and it is being partly funded by Dane County. You can see the response to the announcement by Clean Wisconsin here. And you can find out more about how the biodigester works here. It will be interesting to see how the economics work out. Ultimately, the best outcome would be if these units produce enough energy to actually generate money, which would justify their expansion elsewhere.
So last week, Jon Fasman, our Atlanta correspondent, and myself had a piece published in The Economist about nutrient pollution along the Mississippi. I've since received a letter pointing out that if municipal sewage authorities produce only 10% of the nutrient pollution then they can only trade with farmers to reduce this amount of agricultural output. This is a flaw I'd not considered before. Please someone let me know if there is a solution to this.
Nutrient pollution is a growing problem all along the Mississippi
Jun 23rd 2012 | CHICAGO AND THE MISSISSIPPI RIVER DELTA | from the print edition
Too much of a good thing SOUTH-EAST of New Orleans, where the Mississippi empties into the Gulf of Mexico, the North American land mass does not end so much as gently give up. Land subsides to welts of green poking up through the water, and the river grows wider and flatter until it meets the ocean, where a solid line divides the Mississippi’s brown water from the gulf’s blue. On its long journey south the water has scooped up nutrients such as nitrogen and phosphorus, mainly from the fields of the Midwest. So much so that agriculture’s gift to the gulf is a “dead zone”.
The excess nutrients cause algae to bloom, consuming all the available oxygen in the sea, making it hostile to other forms of marine life. Creatures that can swim away, such as shrimp and fish, do so; those that cannot, die. In the four decades since the dead zone was discovered it has grown steadily. Today it covers 6,700 square miles, an area larger than Connecticut. [More...]