Composting Mechanism
Segregation: A thorough segregation is most vital part for achieving pollutant free, well decomposed quality compost. If the quantity is larger than 50 ton/day the use of sieving machine is a must. It is a paradox that we have not been able to impress each household to separate the biodegradable material, recyclable material, civil works material, etc. for which we should use the electronic media, social workers, NGO and others, at the generating and collecting stage.
The Seven Stages of Composting Process as depicted in the flow chart are:
1. Mesophilic Phase: For regular observation and monitoring such as proper aeration, turning the mass, watering, addition of bio-inoculum etc. Desired length x width x height varies, but should not be more than 2 m height and 2.5 m width. Temperature is in the range of 15-45 C, moisture 50-60% by volume, different microbial communities depending upon the substrate are sprayed under aerobic condition. Total period is not more than 10 days and then turning is performed and if required the inoculum is added again.
2. Thermophilic Phase: During this phase temperature reaches from 45 C to 70 C, lasting around two weeks. Turning must be done as it is a aerobic process.
3. Second Mesophilic Phase: Ensure that during last stage the decomposition process is apparent and some steam is released while turning. In this stage too, add some inoculum if required and maintain moisture at 50%. The mesophilic organisms, often dissimilar to those of first mesophilic phase, recolonize the substrate. This phase last for one week or so.
4. Cooling Phase: The bacterial/micro-organisms activity may have decreased by 50% but their taxonomic and metabolic diversity increase. Detailed analysis revealed that organic oxidizers have degraded natural complex polymers such as cellulose, hemicellulose, lignin, wax, fat and others.
5. Maturation Phase: During this phase the main activity which takes place is degradation of the more resistant compounds and getting them partly transformed into humus. These compounds are lignin, lignocellulose and other recalcitrant components of tree bark, yard wastes, agricultural wastes, etc. Paper may contain up to 20% of lignin. Most of the fungi, predominant cellulose and lignin degraders, are responsible for their decomposition and enzymatic activity.
6. Screening: The well decomposed material is passed through 4mm sieve and air classiflication machine. It has to be ensured that no pollutant is passed through those sieves and also glass pieces are removed through air classification system.
7. Humification Stage: Synthesis of humus during composting in which organic compounds of natural origin are transformed into relatively stable compounds. Humus is the end product of composting, which is black brown, high molecular weight, high CEC and is a store house of plant nutrients. During humification aliphatic compounds of waste materials changes into
aromatic compounds upon microbial action. Humus is composed of fulvic acid and humin, matured humified compost is characterized by high content of humic acid and is largely responsible for clay-humus complex, which in turn responsible for nutrient supply, water holding capacity and soil aggregate formation.
credits : ICAR-IISS
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