Well, I want to be clear that my cement mixer compost sifter is only used for sifting my chicken run compost. I don't compost anything in the cement mixer.
My chicken run litter is mostly leaves, grass clippings, and used chicken coop bedding. All the chicken poo gets mixed in with the coop litter, which for the past couple of years, I have been using paper shreds. When I clean out my coop, I toss all the used bedding into the uncovered chicken run where it is exposed to the weather. It takes a few months to compost in place, with the chickens scratching and pecking through it every day.
In my cement mixer compost sifter setup, the finished compost drops down into the black wagon and any chicken run litter that is too big for my composting screen gets reject out to the gray wagon.
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I can change out the compost screen inside the barrel. I have a 1/4 X 1/4 inch screen for fine potting and seed starting mixes. I mainly use my 1/2 X 1/2 inch screen for compost in my raised beds. And the outside screen on the barrel itself is 1/2 X 1 inch, which still gives a nice finished compost, but not as fine.
Of course, the smaller the compost screen used in the compost sifter means the finer the finished compost that goes into the black wagon, but more chicken run litter would be rejected with the smaller screens.
For the most part, I just dump the rejects in that gray wagon back into the chicken run for some more breakdown time. However, sometimes I use that rejected rough material as top mulch in my gardens.
I mentioned that I primarily use shredded paper as coop litter, which composts in probably less than 2 months when exposed to the weather outside. Wood chips would take longer, maybe around 4 months. In any case, since I converted my entire chicken run into a chicken run composting system, I can harvest as much compost as I need at any time with lots of ready to use compost left over. Last year, I filled 4 new raised beds, and top filled another 6 beds and used maybe only 10% of my available chicken run compost.
Bottom line, I don't even have to worry about how long it takes for my chicken run litter to compost in place because I now have more than I would ever use in a year. All that Black Gold compost sitting in the chicken run is like money in the bank!