The Composting Process

The following article explains in detail the composting process. It explains the bilogical and chemical changes that take place during the composting process.

In the composting process, microorganisms, break down complex organic molecules (proteins, amino acid, lipids carbohydrates, and cellulose) into simpler ones ( mostly cellulose and lignin ). The microorganisms require an aqueous or moist environment and oxygen. The exothermic reaction in the composting process is depicted below:

                Complex molecules + O₂ + microorganisms

→compost + new cells + dead cells + heat +CO₂ + H₂O + NO₃ + SO₄

In the process of composting living organisms, which make up about 5% to 10% of the organic material, releases the energy and nutrients stored in the tissues of the plant and animal residues in the starting compost material. There are several different kinds of organisms, and each has a specific substrate on which it works. An entire food chain develops during the compost process:

·         Microorganisms such as bacteria, antinomycetes  ( slime molds ), fungi, and algae break down the bulk of organic material. Their population, commonly referred to as the “microbial biomass,” is most crucial to the process.

·         Protozoa, nematodes, and some other small organisms such as mold mites (Acari ) and springtails ( Collembola ) feed on the microorganisms.

·         Beetles and other insects feed on the mold mites, springtails, and other small organisms.

·         Larger organisms such as earthworms, flatworms, centipedes, millipedes, snails, slugs, and sowbugs feed on the decaying plant materials. They speed up the compost process by mixing the materials and reducing the size of particles.

    The carbon/ nitrogen (C/ N) ratio is the most important measure of nutrient balance in the compost. Microorganisms use carbon as a source of energy, and both carbon and nitrogen are used for building cell structures. The C/N ratio declines as the composting process proceeds. More carbon is required than nitrogen; a typical final C/N value is approximately 22:1 (MOE, 1991 ).

    The C/N value determines how the finished compost affects the soils to which it is applied. If C/N is greater than 25:1, the microorganisms in the compost will complete with the crops for available nitrogen. At compost levels below 20:1, the energy source, carbon, is less than needed for conversion of nitrogen into proteins. In this case, the compost microorganisms remove excess nitrogen as ammonia, denying it to plants and thus inhibiting plant growth. The C/N ratio in compost can be controlled by adding either highly nitrogenous materials like grass clippings and green vegetation, or highly carbonaceous materials like hay and dry leaves.

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