Sunday, June 24, 2012

Why not to compost meat and dog crap

I have done two experiments in composting since my first post. Both took about a month. The first was a traditional mix of stuff that I showed pictures of in the last post. Weeds, hay, paper shavings, kitchen scraps. The second one was one I called "toxic waste" and consisted of frozen chicken carcasses (that I was going to turn into stock, but ran out of freezer space), dog crap, and paper scraps.

Ill post my findings on my "toxic waste" experiment. Everyone always says not to put these things in compost, but usually don't say why.


Meat and crap cause disease and can  infect the compost, it is unknown how long till the compost is safe. Rats, cats, coons and flies, oh my. Flies appear and reproduce even if you use a sealed tumbler composter. The compost will stink horribly for 2-3 weeks depending on size, surface area, amount of out-door greenery and ratio of meat/crap to "other". Time to completion was not different than a traditional/vegitarian compost, about 1 month.

First, it can cause DISEASE. 

Things that rot meat can make you sick, whereas thing that rot vegetables usually don't. Same goes for crap. Crap of herbivores usually can go into compost no problem (e.g. rabbit, horse, cow), but that from carnivores (e.g. dogs, cats, people) can carry disease that makes carnivores (e.g. people) sick. I knew this before I started and used gloves before touching the bin, and didn't really touch the compost while it was cooking. Afterwards, I left the gloves (made of canvas and suede) in the sun, and washed my hands immediately. Last I heard, no one has done a study to determine under what conditions omnivore crap is safe for composting/laying on crops.

Second, PESTS. 

My composter is a tumbler typer, sealed and off the ground, so I didn't have to worry about rats, cats and coons. If you have a pile on the ground, this is the number 1 concern (your probability of getting sick is less because the rats will eat all your meat and dog crap every night). You will feed every omnivoric mammal in your neighborhood. I did get a lot of flies. I now know the full life cycle of a common house fly and what they look like at each stage.

Third, it SMELLS. 

Coincidentally, before I started this experiment, I was on the wikipedia article for "fragrance" and it mentions Cadaverine and Putrescine.Well, I now know what they smell like. It's bad, although it gives you a keen appreciation of which way the wind is blowing based solely on your relation to the composter in your yard. It takes about 1-3 days to get started and lasts for 10-14 days for the 10-20 picked over chicken carcasses I used. I tried to turn it a lot, and add more brown matter (then wet it), which usually makes things stop stinking, but it didn't work. Brown matter + stink usually makes it better, because the stink is ammonia, which is a sign that nitrogen is degassing. It is degassing because there is not enough brown matter for the flora (bacteria and fungi) to use and turn into dirt, so bacteria just eat the nitrogen and fart it out as ammonia. Not an answer for cadaverine and putrescine. Apparently, dead animals are best left to animals (e.g. worms, cats, maggots, hyenas) to dispose of, leaving it to microflora is just a huge mistake. I have put chicken bones and small amounts in normal compost without ill effects, I guess the difference is quantity - 2 chicken carcasses in a cubic yard of compost isn't a big deal, 20 in a new batch definitely is.

Fourth, People say it takes a LONG TIME. I think this is a LIE. 

This experiment basically took the same amount of time as a traditional (vegitarian) compost, about a month with my rig. A problem I ran into is that because of the low amount of outside greens in mine (hay, leaves etc.), mine took a long time to get started on something approaching aerobic respiration. Paper is what I use for brown matter, since I really only have 1 tree on my property. Paper is VERY clean, it doesn't get moldy nearly as fast as people with drywall in their basements seem to think it does. Hay on the other hand, is filthy, it has lots of spores and bacteria and fungus on it, and is great composting material since it contains green matter and brown matter and living things. Experiment: wet some hay, straw and paper, and put in a dark aerated place, see which grows mold fastest (A: the hay). Since I didn't have any hay for this experiment, or any real outdoor starting material, mold (the white fuzz I'm used to) took a long time (3 weeks) to form. What does make things take a long time is fat and salt. Fat coats things and is air tight, I think this is the reason it cant rot (because any cell that is coated in fat cant get water (because water is heavier than fat) or air (because fat is heavier than air). Putting fat in your compost will inhibit the beneficial aerobic flora you want (which work faster and don't stink), or worse yet, inhibit decomposition totally. Salt you don't want in your compost for the same reason you put it on food - it removes water from cells (of a tomato to make it taste like a tomato and not like water, and of a bacteria so that it doesn't rot your hard caught cod fillet).


I have put chicken bones, and bits in the compost before, and I think it's fine as long as there is enough other stuff in there. Boiled chicken bits produced only ammonia for a few days, so I will continue to dump that into a compost that has established for about a week. We have a dog, and have been feeding him the cartilidge from bones, so bones going into the compost have much less meat than they used to (the stuff that we stuck in the freezer and then went into this experiment). The dog crap I dont think I will put into the compost again.