PROCESSING: TIME AND ACCELERATION
1. It is possible to get vermicompost in 5 to 6 weeks with high worm populations and frequent management; 2 to 3 months (60 to 90 days) under favourable conditions; but 4 to 6 months is a better estimate with minimal management of the worm beds.
2. With high volume flow through systems, it has been reported that a marker such as a coin placed on the surface of the bed will typically drop out the bottom of the bed in about 60 days.
3. With a high worm population, kitchen wastes or animal manure will be decomposed in 4 to 6 weeks. If the material is to be used in certified organic production systems, the required worm composting time for a batch system is four months (16 weeks).
4. Worm populations will clearly decline with no added feed for four months. Worms are extracted over a one month period. A low population of worms is left for up to one month prior to sieving the finished compost. This also allows time for additional worms to emerge from cocoons.
Maturity and Stability
Compost/vermicompost quality is assessed on the basis of its stability and maturity. Good compost would have the texture of moist loose soil homogeneous and aesthetic. The abundance of physical, chemical and biological changes occurred during aerobic or worm composting. Different parameters proposed to assess the maturity of the compost include the C/N ratios, water soluble carbon, cation ion exchange capacity, CO2 evaluation, NH4-N/NO3-N ratio, organic carbon content, and humus content. However, germination index (GI) measuring phototoxicity has been considered as a reliable parameter to quantify compost maturity. A coliform test gives indication of pathogen reduction.
Composting and Vermicomposting-A comparison
In contrast to composting, vermiculture has several distinct applications, with the potential to produce different grades of end product, depending on volume or time constraints:
1. The complete processing of organic wastes by this method produces the highest-grade end product, in the form of worm casts. These typically contain much higher concentrations of vital nutrients than standard composted material. Worm casts tend to be used as a high quality (and high value) soil conditioner within the horticultural sector, rather than as bulk compost or plant bedding material.
2. The partial processing of organic material, in order to accelerate the composting process or to provide a product of higher quality than standard compost.
3. Elimination of nuisance odours associated with the decay of organic matter, such as in forms of open air composting, which do not employ sealed ‘in-vessel’ equipment.
4. The energy requirements of vermicomposting are very small compared to the existing waste disposal systems and processing costs are negligible.
5. The breeding of worms. Although this is not of primary concern for a municipal composting installation, such a facility would require very large numbers of worms in order to operate satisfactorily. The maintenance and increase of worm numbers is therefore necessary, in order to increase initial worm numbers as the facility expands.
Process acceleration
1. Using Organic nutrients and other additives.
Literature survey on this area of research showed that only very few reports were available on the successful use of organic nutrients or other additives for enhancing the vermicomposting process. A recent article by Parray,et al, 2014 reported the use of Spirulina and Trichoderma as probiotic and microbial inoculants during pre-decomposition period in order to get qualitative and quantitative improvement vermicomposting. Studies by Vasanthi,et al, 2011 recommended the use of an organic nutrient, Jeevamirtham (a preparation using cow dung, urine, jaggery and black gram flour) for vermicomposting to enhance the functioning of the earthworm and to increase fertilizer value of vermicompost
2. Using Effective Microorganisms(EM)
EM is a multi-culture of co-existing anaerobic and aerobic beneficial microorganisms. (Higa, 1991;Fig.10).The major groups of the microbes present in EM are:
They are used directly in waste management programmes as they can grow and multiply in solid wastes and other residues under proper conditions and are capable of converting wastes into high-quality compost. Studies by the author in 2013 showed that EM can be used to convert different types of lignocellulosic residues from a large wood industrial complex into a reusable form (E.Sreenivasan, 2013b). Research works by this author, with the objective of enhancing the efficiency of the earthworm that is involved in the process of vermicomposting of wood waste, by fortifying the vermibed using an effective microbial suspension were successful during the initial trial. This work requires further experimentations to establish and recommend the utilization of Effective Microorganisms for enhanced functioning of the earthworms.
Fig.10: Sample of commercially available EM solution