You’ve started your compost, been adding to it for a few weeks…. Now how do you tell when it is… done?
The short answer is: When it looks and smells like dirt. When the biological breakdown of the organic material has reached its final stages, the compost will look like the rich, dark soil that you buy in the bags at gardening supply store. Another way to tell if it is finished is if it no longer heats up after you turn it. The exothermal reaction will begin to wane as the compost reaches maturity.
Once there is insufficient bio matter to be broken down, no more reactions can occur to produce heat. However there will always be some matter to be broken down so eventually it just comes down to making a personal call on if your compost is “ready.” The typical process can take from several months up to a year to be completely ready, that being the case it is in your best interest to begin composting sooner rather than later. I also recommend starting a second batch a few months after your first one, so that you can rotate them out as they mature.
Another way to tell is to screen your compost. Give your compost pile a good turn, and then pour some into a screen made from chicken wire stapled into a small wooden frame. When sifted, if the majority of the compost falls through the chicken wire it should be safe to use. If you are utilizing the two batch method, sift the entire batch and then throw whatever did not fall through into the second bin. You can now reuse the first compost bin and start the process over again.