Temperature should be controlled to a 140-150 degrees F upper limit. Above these temperatures even thermophilic microbes either self-destruct or become less effective. Moisture is removed naturally from the compost medium. Over two-thirds of the original water content of compost may be lost during decomposition. Often water must be added during the process to maintain activity.
Carbon dioxide is a product of the biochemical reactions that are part of composting.
This gas must be removed from the compost microenvironment to avoid toxic concentrations that inhibit the process. Oxygen must be available to microbes in sufficient quantities to ensure vitality of the aerobic types and to minimize odors. The amount and type of bulking agent added during preparation of the compost determines the free air space in the pile. Air may be forced through the pile to speed up the process. However, forced aeration adds complexity to the process.