(Continued from Part 1. This concludes the article.)
After your pile is built you wait. The microbes do the work. One helpful tool in this part of the process is a compost thermometer that will probe temperatures 18”-24” into the pile. The internal temperature tells you what is going on inside the pile so you know when to turn the pile. We will only be turning the pile once.
As you can see this pile is cooking at around 140 degrees, which means my microbes are in turbo mode. You probably don’t want it much hotter than this. The lower portion of this pile is probably not that hot since the bottom of the pile is ~5 months old and has already decomposed quite a bit. If I were to insert a metal rod into this pile and pull it out after a minute, the end of the rod would be almost too hot to hold. This pile has been between 120-140 degrees for several months as I keep adding to it. This is why manure, weeds, and diseased plants can be put in compost. The heat, and beneficial microbes take over and wipe out most of the bad stuff. However, please use common sense, compost won’t kill everything, so don’t treat it like a hazmat disposal. If you know the material contains human or animal biohazard or a recurring soil disease/pest organism, find somewhere safe to dispose of it.
I checked the temperature about 6” from the edge of the pile on the same day in the same pile. The temperature was about 20 degrees cooler than the center, but that is still very warm. This means the material is decomposing all the way to the edge of the pile. This is why I used solid sides for my bins.
After I finish adding materials to a pile, I monitor the temperature of the pile. When the temperature drops to near ambient temperature I know the microbial processes are stabilizing and the pile is ready to turn. If you are not monitoring temperature actively you will want to wait 3-4 months from when you stopped adding materials to the pile. If the pile was finished in late fall, you will want to add a couple months since winter temperatures can slow the process down. The other major consideration while waiting for the pile to finish is moisture. If you live in a wet climate you may wait to cover your pile or build a roof over your bins. If the piles get soggy it will slow down the process, and might stink. If you live in an arid climate you may want to cover your pile to keep moisture in, and you will probably need to water your little microbe workers to keep them cranking away.
When the pile is ready to be turned, I take some of the sides off for easier access and fork the pile over into the adjacent bin, put the sides back on, and leave it for about three months. The pile will probably heat back up again due to all the extra oxygen, but will not get nearly as hot as the fresh materials did. After it cools, additional organisms that cannot survive the high heat of the initial pile will move in and help finish the pile (earthworms for example). It is important to allow time for this to happen.
You want a balanced finished compost. It is hard waiting for your first batch, but if you are always building new piles, you will be producing a continuous supply of compost. Some people advocate turning compost more often to speed up the process. It will certainly help break down the organic matter faster, but I expect there will be a tradeoff. If you are constantly turning your pile and keeping it in high heat mode, you will not get a balanced mix of microorganisms in your compost. Remember, we are trying to mimic the natural system which means a balanced mix of soil organisms. Most of them will not be present in a high heat environment.
This photo is of compost from a pile that is almost finished up. After the initial decomposition and turning it has compressed to half the initial volume. The compost has a fresh earthy smell, is moist and crumbles easily in your hand.Continue reading“Composting Your Black Gold – Part 2, by Hobbit Farmer”