In the elaboration of organic products, if it is desired to obtain a quality compost, theoretically a carbon/nitrogen ratio of 25-35 is adequate, but this will vary depending on the raw materials that make up the compost. If the ratio is higher than 35, there is not enough nitrogen for microbial growth, so biological activity will decrease and the process will be delayed. On the other hand, if it is less than 30, the nitrogen will be in excess and can be lost as ammonia (NH3), which will result in an unpleasant odor.
▶ As for the required moisture ratio, it is known that microorganisms need water as a means of transporting nutrients and other elements, and it is also a determining factor in gas exchange. In the composting process it is important that the moisture content reaches levels close to 40-60%. If the moisture content is higher, water will occupy all the pores and therefore the process will become anaerobic (without oxygen), i.e. putrefaction of the organic matter will occur.
If the moisture content is too low, the activity of the microorganisms is reduced and the process is slower. The moisture content will depend on the raw materials used. The moisture content of the pile can be tested manually by squeezing some compost. If some drops of water appear in the hand, the humidity is optimal, if on the contrary, after squeezing the material it does not disintegrate into small particles, it means that it lacks humidity.
Another point to keep in mind is that the composting process is an aerobic process, that is, it needs the presence of oxygen for the proper development of microorganisms, therefore aeration is an important factor in the composting process since oxygen is essential for the metabolism and respiration of the microorganisms involved in it.
Aeration has a double objective, first to provide sufficient oxygen to the microorganisms and, secondly, to allow the maximum evacuation of the CO2 produced. The oxygen concentration must be maintained at levels higher than 5% for an adequate activity of the microorganisms. For this reason it is common to carry out some management to improve the aeration of the pile, such as turning.
Additionally, as I have recommended in other publications, the temperature in the composting process reflects the biological activity of the microorganisms. The temperatures reached during the process are related to the size of the pile, its water content and the carbon/nitrogen ratio of the mixture. Thus, the lower the carbon/nitrogen ratio, the higher the temperatures reached. It is important to control the temperature throughout the composting process because, just as high temperatures allow the elimination of pathogens, parasites and weed seeds, they can also eliminate the microorganisms that carry out the process and increase the risk of fires in the pile.
