Stage one: mesophilic
This takes a few days. Mesophilic bacteria begin to physically break down biodegradable substances.
Stage two: the temperature rise
The most obvious factor at this stage is rising temperature. If it is not closely monitored, the pile can heat to the point where the microorganisms are killed — a detrimental outcome for the batch.
Stage three: thermophilic
This happens when thermophilic bacteria exhaust the supply of biodegraded compound. It takes the longest of the three stages to complete.
Why controlled machines exist
Hot composting produces high-quality compost in a short period and is more likely to destroy pathogens. A machine keeps the process in that band deliberately rather than hoping a pile gets there.
