I was having a conversation with someone who's looking to convince their city council to allow urban chickens, and she said one of the council's concerns was the phosphorous runoff from all these incoming urban chickens.
Yes, it would easy to dismiss these concerns as folly (poppycock?), but to do so won't help get urban chicken ordinances passed. While we've got our own two hens in the back yard, I don't want to be measuring and weighing every piece of excrement that drops out their backside (we simply put it all in the compost bin).
So I did a little research to see just how much poop a chicken produces and what effect it has on the environment.
How much poop per chicken?
The University of Missouri Extension reports six commercial laying hens will generate approx 11 pounds of manure every week (1.5 gallons). The Fisheries and Aquatics Department cites 40g of excretia per chicken per day (that's 1.4 oz/day or 9oz/week which means six hens would put out 54 ounces in a week or just over 4 pounds).
For the sake of argument, let's go with the Mizzou stats of 11 pounds from six chickens each week. If the average urban chicken flock is 3 hens, we can cut that total in half to 5.5 pounds per week.
This seems to be the perfect amount for composting or including with the regular waste disposal at the curb or what have you (I dare say this quantity is comparable to what a cat owner puts into their trash each week?).
So, thoughts of being over-run by chicken poop seem a bit fantastical.
What about phosphorous run-off?
But let's go back to our six chicken flock and look at the phosphorus run-off concerns (a real concern when considering industrial chicken farming).
According to PoultryOne.com website, the average percentages (per total weight) of chicken manure is as follows: 1.8 nitrogen, 1.5 phosphate, and 0.8 for potash.
So, we've got six chickens producing 2.5 OUNCES of phosphate each week which makes ~8 pounds (2.5 x 52 weeks/ 16 oz per pound) of phosphate PER YEAR. Even if dumped directly into the nearest pond/lake, you're looking at miniscule changes to the phosphorous content of a lake for six birds.
If every household in medium-sized city (20,000 households) owned six birds each, you're still looking at a little over 160,000 pounds of phosphorous spread out across an entire city. Compare this to the industrial chicken industry practice of housing 150,000 birds in a single 500-ft long chicken house (that's 200,000 pounds of phosphorous from one chicken house), and you see it's an apples-to-oranges comparison regarding the concentration/disposal of the poop.
No wonder the industrial chicken houses stink to high heaven!
Mind you, all this build up of phosphorous in the urban chicken poop assumes there's no collection/composting/etc AT ALL from the backyard chicken coop (which I hope would signal neighbors to call animal control for cruelty charges to the owners). But that's another post entirely.
How much urban chicken poop are you dealing with and what do you do with it? Composting like me? setting it at the curb each week? throwing it under the shrubs? Please share!