Vermicomposting

What is Vermicomposting?

• The term vermiculture refers to the cultivation or production of earthworms.
• Vermicomposting is the method by which worms are used to turn organic materials (usually waste) into a humus-like substance known as Vermicast.
•  The term vermicast is also termed as worm castings, worm manure, worm feces and worm humus.
• Vermicompost includes not only worm castings, but also bedding materials and organic waste in different phases of decomposition.
• It also includes worms that are at different stages of development and microorganisms involved  in the composting process.
• In the home garden, earthworm castings often contain between 5 and 11 times more nitrogen, phosphorous, and potassium than the surrounding soil.
• Vermicompost also adds soil with humic acid that helps link soil with minerals and nutrients.
• Chemical fertilizers can rapidly improve the growth and development of plants, but will not develop soil.
• Studies suggest the best growth in plants with 10 to 40 percent vermicompost content in a soil mix.
• Many beneficial microbes are destroyed by the heat of daily compost.
• Vermicompost is aerobic and therefore can have up to 1000 times the normal compost microbial activity.
• Better disease tolerance indicates increased microbial activity in the soil.
• Vermicompost can be generated within 1/3 of the normal compost period.

What are the requirements for the preparation of the vermicomposting?

1. Breeder worms (Earthworms)
2. Feeding materials: Any type of biodegradable waste: vegetable waste, crop residues, weed biomass, dead leaf litter, agro-industry waste, urban and rural biodegradable portion of waste
3. Bedding materials
4. Production systems (a container or pit in a shady place)

What role does earthworm plays in vermicomposting?

• Physical/Mechanical:
  • As the earthworm moves inside the substrate, it helps in the aeration of substrate, as well as it grinds the substrate.
  • This keeps the organic wastes aerated and cooling is aerated.
  • It also saves costs required for mechanical process units for mixing that are used in conventional composting.

• Biochemical:
  • Microbial decomposition of substrate takes place in the intestines of the earthworm.

• Other roles:
  • They maintain aerobic conditions in the mixture and ingests solids from the substrate.
  • A portion of the organic materials is converted to worm biomass and respiration products.
  • The remaining partially stabilised matter is expelled as discrete material i.e. termed as castings.
  • worms and aerobic mesophilic organisms act symbiotically and fastens the decomposition of the organic matter.

Types of vermicomposting worms:

• On the basis of their feeding habits, they are classified as detrivores and geophages.
• Detrivores feed on plant litter or dead roots, and other plant debris or on mammalian dung on or near the soil surface.
• These worms are referred to as humus formers and comprise the epigeic and anecic forms.
• Some examples of detrivorous worms are  Perionyx excavatus, Eisenia fetida, Eudrilus euginae, Lampito mauritii, Polypheretima elongata, Octochaetona serrata and Octochaetona curensis.
• Geophagous worms, feed below the surface and intake greater quantities of organically rich soil.
• It comprise the endogeic earthworms. Metaphire posthuma and Octochaetona thurstoni are two general examples of geophages.
• Epigeics are surface dwellers who feed on the surface of the soil with organic matter.
• Endogeic earthworms spend much of their time mainly in the mineral layer of the soil and burrow.
• For use in the vermicomposting process, the epigeics and anecics were harnessed.
• Eisenia fetida, the tiger or branding worm, is one of the most widely used worldwide.
• Lumbricus rubellus, Eudrilus eugeniae and Perionyx excavatus, an Asian genus, and Eisenia andrei are other suitable species.
• Redworm species in both Eisenia fetida and Lumbricus rubellus are composters, living naturally in soils that contain a lot of organic matter.
• For this reason, they are often used together, with Eisenia fetida on the surface and Lumbricus rubellus farther down, in vermicomposting systems.

Eisenia fetida in Vermicomposting:

• The genus Eisenia is named after a naturalist from Sweden.
• The name of the genus fetida (foul-smelling) derives from the pungent liquid exuded when roughly handled.
• They are are more generally referred to as red Wigglers, brandling worm, panfish worm, trout worm, tiger worm, red Californian earth worm, etc.
• They are identified by the yellow stripes in between the segments.

Process of vermicomposting:

1. Feeding materials:

• Worms can eat dung from animals, agricultural waste, residues from vegetables, waste from the food market, waste from the flower market, agro-industrial waste, waste from the fruit market and all other bio-degradable waste.
• Before being used for vermicompost production, cattle dung should be dried in open sunlight.
• Depending on the feedstock being used, temperature, moisture levels and the density of the worm population, the exact loading rate (at which raw feedstock will be applied to a worm bed) can differ.
• Proper loading rates require no inclusion of new feedstock until the bulk of the feedstock previously introduced has been decomposed.
• A high protein feedstock such as grains, mash, or cottonseed meal is added if worms are not growing.

2. Bedding materials:

• As bedding products, certain agricultural residues may be used, such as plant waste and solid composted manure.
• In general, because of bedding content’s effect on increasing soil pH, which is harmful to worms, the bedding content should maintain moisture, stay loose and aerated, and be low in protein and nitrogen.
• The bedding content should be varied to provide the earthworms with a variety of nutrients and to create richer compost.
• Suitable bedding materials include:
  • 1. coir waste
  • 2. cardboard
  • 3. shredded fall leaves
  • 4.  sawdust
  • 5. chopped straw
  • 6. mulched paper such as newspaper
  • 7.  semi-composted solid manure
• Sieving and shredding:
  • By shredding raw materials into small pieces, decomposition can be accelerated.

3. Blending:

• To achieve a near optimal C/N ratio of 30:1-40:1, carbonaceous substances such as sawdust, paper and straw can be combined with nitrogen-rich products such as sewage sludge, biogas slurry, and fish scraps.
• Good quality compost, rich in main and micro nutrients, is produced by a varied mixture of substances.

4. Pre-composting/Half digestion:

• In order to avoid worm systems from feeling so much sun, manure feedstocks and bedding should be pre-composted.
• When introduced into the worm systems, fresh manures produce a lot of energy that transfers into additional heat.
• Strong heat in the beds of worms can be deadly.
• The bedding and feeding materials are then combined, watered and allowed to ferment for approximately two to three weeks.
• It is necessary to hold the raw materials in piles to allow the temperature to exceed 50-55^o C.
• The substance is overturned 3 to 4 times during this phase to get the temperature down and to aid in uniform decomposition.
• It is passed to the vermicompost production method as the material becomes very fragile, and worms are inserted into it ranging from a few days to a few weeks old.

5. Moisture, temperature and pH:

• 50-60 percent is the optimal moisture level for maintaining aerobic conditions.
• The temperature should be within 25-30^o C of the stacks.
• The activity of microflora and earthworms can be decreased by higher or lower temperatures.
• The height of bed can help to regulate the increase in temperature.
• The raw material’s pH should not be greater than 6.5 to 7.

Methods of vermicomposting:

• A 1 meter by 1 meter by 0.3 meter container carries about 30-40 kg of bedding and feeding materials.
• It is possible to prepare a vermiculture bed or worm bed (3 cm) by putting dust or husk or coir waste or sugar cane garbage in the bottom of the tub/container.
• The culture bed can be spread with a sheet of fine sand (3 cm) followed by a layer of garden soil (3 cm).
• A15-20 cm sheet of organic waste material (pre-composted/half digested) can be spread on the worm bed. 
• It is sprinkled with rock phosphate powder (to increase the content of phosphate) if required.
• Soil or cow dung is used to cover the organic layer with (sprinkle cow dung slurry).
• The selected earthworms are released through the cracks created (1000-1500).
• In order to prevent birds from eating the earthworms, cover the ring with wire mesh or gunny sack.
• Water is sprinkled to maintain adequate humidity and temperature regularly/daily.

Harvesting of vermicompost:

• In about 3 months, the vermicompost is ready (may vary depending on organic waste used as substrate).
• It will be black, granular, lightweight and humus-rich.
• Vermicompost harvesting requires manual isolation of worms from the castings
•  Watering is stopped for two to three days before emptying the beds to facilitate the removal of the worms from the compost.
• The worms will be pushed to the bottom of the bed by this.
• For new culture beds, the worms are collected.
• To retrieve the cocoons, young worms, and unconsumed organic waste, the gathered vermicompost is dried and passed through a 3 mm sieve.
• For seeding the new culture beds, cocoons and young worms are used.

Storage and packing of vermicompost:

• The harvested vermicompost should be stored in dark, cool location.
• It should have moisture of at least 40 percent.
• Sunlight should not fall on the content being composted.
• At the point of sale, packaging can be done.
• Periodic sprinkling of water can be done to retain the level of moisture and also to maintain a beneficial microbial population if it is kept in an open location.
• Vermicompost may be preserved for a duration of one year without loss of quality if the moisture level is kept at 40%.

What are the precautions to be taken while preparing vermicompost?

• In vermicompost preparation, only plant-based materials such as hay, leaves or vegetable peelings can be used.
• Animal products such as eggshells, beef, bone, chicken droppings, etc, are not appropriate for vermicompost preparation.
• For the rearing of earthworms, toxic plant species like tobacco are not appropriate.
• It is necessary to protect earthworms from birds, termites, ants and rats.
• During the process, sufficient moisture should be maintained.
• The earthworms could die by either stagnant water or lack of moisture.
• The vermicompost should be withdrawn from the bed at periodic intervals after completion of the process and replaced by fresh waste materials.

Vermicompost production system:

1. Beds and/or Bins:

• The most popular small-scale device is bins.
• Bins may be built with a drain hole at the bottom of many materials, such as wooden crates, cardboard buckets or other reusable containers.
• The bottom of the tub is designed to slope like a structure to drain the vermicompost unit from the waste water.
• Bins can measure between 8 and 12 inches deep.
• The size would depend on the available amount of feedstock and bedding.
• As a rule of thumb,  at least 1 square foot of surface area per pound of feedstock should be provided.

2. Pits below the ground:

• There are 1 m deep and 1.5 m wide pits made for vermicomposting.
• As required, the length varies.

3. Windrows (Heap above the ground):

• Windrows are longitudinal stacks of either covered or exposed feedstocks placed at ground level.
• The windrow is initiated by extending a layer 12 to 18 inches deep of organic materials.
• Next, at a rate of up to one pound per square foot, redworms may be added.
•  2 to 3 inches a week on top of the existing pile is layered to apply feedstock to the windrow.
• For ease of management, the pile should not reach 3 feet in height.
• Harvest worms using the light technique.

4. The wedge system:

• This system is a modification of the windrow method by adding feedstock at a 45 degree angle to the current windrow.
• The redworms would move towards the “fresh” pile by creating a “wedge” next to the actual windrow being used.
• Organic materials are applied to this new pile until a height of 3 feet is achieved, then a new wedge starts.
• Worms can pass across the piles laterally.
• We would finally be able to harvest the first pile and subsequent piles after 2-3 months.

5. Continuous flow reactors:

• These are systems with elevated beds that have side walls and mesh bottoms that are either 2 inches by 4 inches or 2 inches by 2 inches with openings.
• To preventbedding from slipping through, place a material such as newspaper on the mesh.
• About 12 inches of bedding is spread on top of the newspaper.
• Redworms are placed at a rate of 1/2 to 1 pound per square foot of surface area on top of the bedding.
• Feedstocks are then inserted on top of the bedding in layers.
• By scraping a thin layer just above the mesh to allow material to fall into the catchment chamber, Vermicompost can be harvested.
• Such systems work better under cover.