Saturday, September 10, 2016

Picking up Phosphorus Grenades

It has been shown that the microcystis aeruginosa bacteria that is associated with algal blooms occurring in Lake Lariat (among many other lakes in the U.S.) is responsive to reductions in phosphorus, but not to efforts targeted at nitrogen reduction. Since dog and cat feces contain more than the usual amount of phosphorus (compared to cow manure, for example), and dogs and cats produce manure close to their own body weight every month, there is probably about 20,000 lbs of manure and about 300 lbs of phosphorus being spread by dogs and cats around the "critical area" of Lake Lariat every month, assuming owners are already sending half of their pets' manure to the landfill. That comes close to 2 tons of phosphorus every year. Unlike nitrogen, phosphorus gets consumed slowly in the soil, so it is more likely to end up in the Lake, where it may accumulate to trigger algal blooms.
Photo by Minnesota Pollution Control Agency
One thing to note about picking up dog crap in one's yard is that it should be done frequently, but at least prior to rain events. Letting it dry for a day or so is OK, if no rain is forecast. I like to time my pile pick-up rounds to coincide with rain-barrel draining when a storm is due the next day. As for dog walking, I've learned to take a couple of poop pickup bags and to have a plastic grocery bag to drop those into. The bigger bag gets tied on my belt until I can dump the contents in a trash can. I would consider composting these, but dog poop bags on the market aren't made for compost piles. Even the vegetable-based bags don't break down quickly or thoroughly enough. (Exceptions exist, e.g. Bio Bag)

For cat owners, the eco-opportunity is greater since cats are often given to going in a litter box. The key is finding a compostable litter. The late Gene Logsdon addressed this idea in chapter 3 of Holy Shit: Managing Manure to Save Mankind. A great odor absorbing material to mix into the litter is ground up biochar. It is not going to break down much in the composting process, but it should enhance composting temperature and time. I'm thinking about hosting an Amazon giveaway with Logsdon's book as the prize. It could be a way to get agriculturally oriented people in my community thinking about manure composting.

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