Vermicomposting

Dr. Gautam Kumar Meghwanshi

Department of Microbiology
MGS University, Bikaner
 Introduction
• Vermicomposting is a mesophilic biooxidation and
stabilisation process of organic materials that involves the
joint action of earthworm and microorganism.
• Compared with composting, vermicomposting has higher
rate of stabilisation and it is greatly modifying its physical
and biochemical properties, with low C : N ratio and
homogenous end product.
• It is also costeffective and ecofriendly waste management.
• Due to its innate biological, biochemical and
physicochemical properties, vermicomposting can be used
to promote sustainable ruminant manure management.
• Vermicomposts are excellent sources of biofertiliser and
their addition improves the physiochemical and biological
properties of agricultural soils.
• In addition, earthworms from the vermicomposting can be
used as source of protein to fishes and monogastric animals.
 COMPOSTING AND VERMICOMPOSTING INTEGRATION
• Composting is the process of aerobic decomposition of organic
waste through microorganisms, whereas vermicomposting involves
the combination of both the microorganisms and the earthworms.
• Some studies propose that vermicomposting process lacks the
ability to kill pathogens, hence it is considered as the major
drawback of vermicomposting process when compared with
thermophilic composting.
• The optimum temperature for earthworms in vermicomposting
process is considered up to 35˚C, whereas in conventional
composting (including thermophilic composting), it may reach up to
70˚C.
• Therefore, vermicomposting process does not attain the favorable
temperature to kill pathogens, and if the temperature exceeds
35˚C, it may lead to the death of earthworms which further stop
the process of vermicomposting.
• Biologically, vermicomposts contain diverse nature of microbial
populations that are more diverse and larger when compared with
the thermophilic composts
• In this scenario, an integrated approach has been
introduced composed of both composting and
vermicomposting processes to achieve better
output.
• There can be two possibilities that are generally
proposed for integrated approach of composting
and vermicomposting: (i) prevermicomposting
followed by composting or (ii) precomposting
followed by vermicomposting.
• By using the second approach, Gajalakshmi et al.
[26] achieved better output by high-rate
composting of water hyacinth before
vermicomposting.
VERMICOMPOSTING THROUGH CODIGESTION OF ORGANIC
WASTES
• Earthworms’ have considerably less survival ability
in industrial wastes, and they need some nutrient-
rich organic source, such as cow dung, biogas
plant slurry, and poultry droppings, (known as
organic amendments) to be mixed with industrial
wastes to enhance the vermicomposting by
providing sufficient amount of nutrients and
inoculums of microorganisms.
• A number of organic amendments are presented
in Table 1.
 Table 1. Initial physicochemical characteristics of some
widely used organic amendments

• Cow dung has been reported as the most suitable Amendment.

• They amendments are also reported to help achieving the suitable
C:N ratio. e.g. when cow dung was added to the waste of citronella
plant, it significantly enhanced the process of vermicomposting with
decrease in C:N ratio up to 87.7%.
• Addition of Amendments also help in vercomposting of toxic
substrates like tannery waste, which otherwise are100% toxic for
earthworms.
Table 2. Vermicomposting with suitable organic
amendment
 VERMISYSTEMS AND VERMIDIVERSITY
Table 3. Different vermitechnology systems
• In all these vermin systems, the diversification of
worms may play a crucial role in overall processing of
the vermicomposting.
• In this way, the selection of appropriate earthworm
species for organic waste degradation is a great matter
of concern and is important for getting better results.
• The adaptability to waste, minimal gut transit time,
fast growth rate, and high reproductive potential of
earthworms are some general characteristics which
should be under consideration before starting the
activity of vermicomposting.
• Earthworms are terrestrial invertebrates broadly
categorized as anecic, endogeic, and epigeic (Table 4)
on the basis of their behavior on natural environments
 Table 4. Classification of earthworms

The vermicomposting of organic waste using diverse range

of earthworms is given in Table 5.
Table 5. Vermicomposting of organic wastes using diverse
earthworms
• Eisenia fetida, also termed as banded worms, are the
most widely used species for the degradation and
stabilization of different types of organic wastes,
including neem leaves, dung of cow, buffalo, horse,
donkey, sheep, goat, and camel, biogas slurry, cow
dung, vegetable market waste, wheat straw, kitchen
waste, agroresidues, and institutional and industrial
wastes, cow manure, and textile mill sludge mixed
with poultry dropping.
• Generally, Eisenia fetida is widely used all over the
globe, whereas Eudrilus eugeniae is popular in
tropical and subtropical countries
 ROLE OF VERMICULTURES IN VERMICOMPOSTING
• Earthworms play an important role in organic waste system
by colonizing organic waste along with consumption,
digestion, and assimilation of high rates of organic wastes.
• They also have the ability to tolerate a wide range of
environmental stresses with high reproductive rates.
• In an organic waste system, earthworms ingest, grind, and
digest organic waste with the help of aerobic and anaerobic
microflora present in the gut of earthworms.
• The physical and biochemical actions are performed in
waste system by earthworms.
• The example of physical actions includes substrate aeration,
mixing, and actual grinding.
• Biochemical actions by earthworms include microbial
decomposition of substrate in the intestine of earthworms
• As a result of this activity, rapid mineralization and
humification process start, which convert the unstable
organic matter into relatively stable and microbially
active material.
• During this stabilization process, chelating and
phytohormonal elements are released, which make the
organic matter into stabilized humic substances with
high microbial content .
• Earthworms ingest organic waste as well as soil which
pass through their body where it mixes with digestive
enzymes and reduced by the grinding action.
• The material that is excreted by the worms after
digestion is nutrient rich and termed as “castings.”
• All these roles are better played in moist soil and well-
aerated soils with low acidic value.
• Vermicomposts produced after digestion and excretion by
earthworms are actually nutrient-rich organic soil
amendment and has considerable potential in crop
production.
• Vermicomposts are peat-like material with high porosity,
aeration, drainage, water-holding capacities, and low C:N
ratios.
• The resulting worm castings (worms manure) are reported
to be rich in microbial activity, plant growth regulators, and
fortified with pest repellents.
• The enzymes secreted through the digestive epithelium of
gut of earthworms are cellulase, amylase, invertase,
protease, and phosphatase, responsible for enhanced N, P,
and K contents in vermicomposts.
• Earthworms get their nourishment from microbes, whereas
microbial activity is influenced by the casts produced by
worms
Figure 1. Mutualistic relationship shown by earthworm
and microbes.
Table 6. Factors with optimal range for
vermicomposting
 FACTORS AFFECTING VERMICOMPOSTING
Feeding
• Enhances growth and reproduction of earthworms and
production rate of cocoon.
• The feeding rate is influenced by moisture, particle size, and
substrates organic content and feed pretreatment.
• High organic matter reduces the activity of worms,
therefore enhancing anaerobic activity of microorganisms
which creates anaerobic and foul odor conditions.
• Toxic metals if present in the organic feed become fatal for
worms.
• Different types amendments such as cow, sheep, horse, and
goat dung may result in better vercomposting producing a
better organic manure.
 pH
• Neutral pH is suitable for the proper working of worms,
but the favorable range reported is 4.5–9.0.
• It mostly depends on earthworm sensitivity and
physicochemical characteristics of the waste.
• The difference in physicochemical characteristics of waste
mainly alters the pH of vermicomposting process.
• The microbial activity changes physicochemical
characteristics of waste during decomposition process
along with mineralization of nitrogen and phosphorus
into nitrites/nitrates and orthophosphates.
• Some intermediates are produced during
vermicomposting, such as ammonium and humic acids,
alter the change of pH.
• Types of substrates also affect the pH of the
vermicomposting system and the overall pH in
vermicomposting process drops from alkaline to
acidic nature.
• This is due to the evolution of CO2 and the
accumulation of organic acids
 Temperature
• The optimum temperature range may be 25–37˚C
which favors the activity, growth, metabolism,
respiration, reproduction, and cocoon production for
earthworms and also favors the microorganisms
associated with earthworms.
• Different earthworm species showed different
responses against temperature. For example, Eisenia
fetida grows optimally at 25 ˚C with 0–35 ˚C
temperature tolerance, whereas Dendrobaena veneta
showed optimum growth at lower temperature and
found less tolerance of extreme temperatures.
• Eudrilus eugeniae and Perionyx excavatus also showed
optimum growth at about 25˚C; however, their
tolerance temperature range was generally found
between 9 and 35˚C.
• From this studies, we may conclude that different
earthworm species showed diverse response
against diverse temperature ranges.
• Vermicomposting systems, when compared with
composting process, are greatly affected by
extreme temperature conditions, that is, low or
high temperature.
• For example, higher temperatures in
vermicomposting systems are responsible for the
loss of nitrogen as NH3 volatilization
• On the other hand, lower temperatures in
vermicomposting process fail to destroy
pathogenic organisms
 Moisture
• The growth rate of earthworms has been related to
the moisture level in the vermicomposting system.
• An optimum moisture range between 50 and 80%
has been considered for efficient vermicomposting;
however, up to 90% of moisture level has also been
considered efficient for vermicomposting process.
• Low-moisture conditions delay sexual development
of earthworms. The optimum moisture content for
Eisenia fetida has been reported as 70–80%.
• Some species of earthworms like Lumbricus
terrestris survive well in dry conditions, whereas
others like Allolobophora chlorotica, Allolobophora
caliginosa, and Aporrectodea rosea did not survive in
dry conditions.
 Stocking Density
• The density of earthworms is influenced by several
factors including initial substrate quality and quantity,
temperature, moisture, and soil structure and texture.
• The copulation frequency of earthworms is high at low
population density, whereas it decreases when the
density approaches the carrying capacity of the
substrate.
• It has been reported that the stocking density of 1.60
kg worms/m2 is optimum for vermicomposting.
• It has been reported that Eisenia andrei grew slowly
on higher population density with lower final body
weight.
 C:N Ratio
• The C:N ratio plays a critical role in cell synthesis, growth, and
metabolism of earthworms. For proper nutrition, carbon and
nitrogen should be present as substrates in appropriate and correct
ratio.
• C:N ratio is one of the most important indicators of waste
stabilization, which is widely used in the index for compost
maturation.
• The improved compost maturity is reflected with a C:N ratio less
than 20 when the initial C:N ratio of the substrate is 25.
• As a result of rapid mineralization and organic matter
decomposition, carbon is lost as CO2 in microbial respiration, and at
the same time, nitrogen is increased by worms in the form of
mucus, and the nitrogenous excretory material results in overall
decrease in C:N ratio.
• However, initial nitrogen contents in the substrate are mainly
responsible for the final N content of vermicompost and overall the
extent of decomposition. The decrease in pH also plays an
important role in nitrogen retention, as at high pH, nitrogen is lost
as volatile ammonia
 GROWTH AND COCOON PRODUCTION
• The growth rate of worms and the production rate of cocoon
during the vermicomposting process are vital for sustainable
progress of the process.
• Physicochemical and nutrient characteristics of the feed and
substrate are the main factors in determining the growth of
earthworms.
• High feeding generally results in high production rates of
cocoon which is also a reflection of the quality of the waste.
• Sometimes, there are factors which may lead to decrease in
cocoon production and growth rate of worms.
• For example, the production rate of cocoon and the
reproduction rate of worms decrease with the increasing
concentration of distillery sludge in the vermicomposting
system owing to the presence of higher growth-retarding
compounds like metals, higher salt concentration, and
grease in the initial feed of worms.
• The reduction in worm’s efficiency was attributed to
the presence of toxic metals. The toxic copper ions
enter the cocoon by diffusion as cocoon membrane is
permeable, and these copper ions interact with the
proteinaceous material and reserve for developing
embryos of worms.
• Similarly, chromium ions across the cell membrane
reduce the transport capability of essential
metabolites due to electrode potential reduction,
which might be the cause of toxicity for developing
embryo.
• Lead also affects during cocoon production by
entering into cocoon through clitellar muscles and
disturbs embryo development.
• Stocking density of worms in vermicomposting system
is another important factor which affects both growth
rate and rate of cocoon production.
• The higher stocking density results in reduced
earthworm growth and cocoon production even at
appropriate physicochemical conditions.
• The worm population of 27–53 worms per kilogram
and 4–8 worms per gram/feed mixture is optimum as
stocking density for effective vermicomposting system.
• It has been reported that the production rate of
cocoon and the performance of earthworm were high
at high-stocking density load, whereas the individual
biomass production was high in low-stocking density
• loads.
• Substrate type also affects the growth rate of worms and
the production rate of cocoon.
• Effects of different animal dungs like from cow, buffalo,
horse, donkey, sheep, goat, and camel have been studied
and varying results have been obtained. Mainly the dung
which were better source of nutrients supported higher
growth rates of worms and rate cocoon formation.
• However, presence of toxic substances along with feed
interfered with both growth and cocoon formation.
• Other factors affecting these growth rate and rate of cocoon
production were Temperature – apropriate range was 25–
37˚C This has been attributed to accelerated sexual
maturity of earthworms with increasing temperature up to
30C.
• Moisture- The optimal moisture content of 65–70% was
considered good for worm growth and cocoon production
• BIOGAS PRODUCTION USING VERMICOMPOST
 BIOGAS PRODUCTION USING VERMICOMPOST AND
USE OF BIOGAS SLURRY
• Biogas is produced as a result of anaerobic digestion or codigestion of
animal wastes or organic wastes.
• Mostly, it is used in lighting and cooking by farmers in agriculture
based countries, which is produced in reactors known as biogas
digesters, and millions of people around the world get benefited by
this low-cost and environment-friendly technology.
• Generally, biogas is a composition mixture of 48–65% methane, 36–
41% carbon dioxide, up to 17% nitrogen, <1% oxygen, and 32–169
ppm hydrogen sulfide, and traces of other gases.
• In anaerobic digestion process, the yield of biogas is affected by many
factors, among which substrate composition is one important factor.
• Actually, it is the pretreatment requirement in anaerobic codigestion
process which enhances the production of biogas; however,
pretreatments are rarely discussed in the literature since the last
decade.
• Currently, intensive research has been carried out to explore the
pretreatment options for anaerobic codigestion and production of
biogas.
• Previously, pretreatment involved mechanical (33%),
thermal (24%), and chemical (21%) methods;
however, the focus has now been diverted toward
biological pretreatments, and the use of
vermicompost is one sound option.
• In fact, the chitin present in initial substrate
composition in anaerobic process is hard to be
degraded by anaerobic microorganisms.
• The vermicomposting process enhances the
degradability of chitin by hydrolysis to free N-acetyl-
D-glucosamine by a chitinolytic system consisting of
two hydrolases, chitinase and N-acetyl β-
glucosaminidase which act consecutively.
• The vermicompost also provides large surface area to
enhance nutrient retention for anaerobic
microorganisms responsible for biogas production.
• Degradation of chitin by vermicomposting made the
conditions favourable for anaerobic microorganisms
to readily attack the vermicomposted enwrapped
degradable organic matters and improved the
methane production.
• Improvement in Methane production using
codigestion with vermicomposting of corn stalks has
been reported when compared to the anaerobic
digestion process used alone.
• The improvement in cellulose destruction was also
observed by the addition of vermicompost.
• On the other hand, the byproduct of biogas termed as
“biogas slurry” can effectively be used for the
substrate amendment in vermicomposting systems.
 INDUSTRIAL PERSPECTIVE OF VERMICOMPOSTING
• Owing to the environmental issues and pollution problems
associated with conventional treatment methods for the treatment
of industrial wastes, vermicomposting has been growing as an
emerging cost-effective and environmentally sound treatment
option for a wide range of industries.
• Vermicomposting can effectively be used for industrial solid waste,
including palm oil mill, paper pulp, winery/beverage, sugar, textile,
food, thermal power plant, dairy, tannery, distillery, oil extraction ,
guar gum, and sago industries.
• Vermicomposting systems are less energy consuming, economically
feasible, and cost effective over conventional treatment
technologies and have more potential of nutrient recovery.
• According to a report. 20–25 million US dollars is required for the
constructionof engineered landfills and dumping of first load.
• On the other hand, vermicomposting provides profit when
compared with capital investment in terms of better growth of crops
and sales of vermicompost.
• The marketing and economic cost effectiveness of
vermicompost has been studied by Devkota.
• The authors collected information on the production
and marketing of vermicompost from vermicompost
producers of Chitwan, Nepal.
• The authors suggested that vermicompost total
production cost was Rs. 15.68 per kilogram compost
and Rs. 0.40 per earthworm with a net profit of Rs.
9.32 per kilogram.
• Total variable and gross cost was found to be 4.30 and
2.55, respectively, in view of undiscounted benefit
cost ratio. The payback period of capital investment
was suggested to be 1.72 years.
• This study revealed high feasibility enterprise for
vermicompost production.
 References
• Gajalakshmi, S., Ramasamy, E., & Abbasi, S. (2002).
Vermicomposting of paper waste with the anecic
earthworm Lampito mauritii Kinberg, Indian
Journal of Chemical Technology, 9, 306–311.