Worm Composting
Worm Composting
(Vermicomposting)
Introduction:
Vermiculture, or vericomposting is derived from the Latin
term Vermis, meaning worms. Vermicomposting is essentially the consumption of
organic material from earthworms. This speeds up
the process of decomposition and provides a nutrient enriched end product,
called vermicompost, in the form of worm castings.
For centuries, earthworms have been used as a means of
decomposting wastes and improving soil structure. Increasing numbers of
businesses world wide are successfully employing vermiculture technology and
marketing vermicompost as an excellent soil conditioner to farmers and
gardeners. The breeding and propagation of earthworms and the use of its
castings has become a very important method of waste recycling through out the
world. It is common to use earthworms on industrial scale to aerate, sanitize
and deodorize types of contaminated waste sludge. For instance, Japan imports
millions of tons of earthworms per annum for waste conversion. Worms are
odorless and free from disease. Vermiculture looks set to emerge as a
significant waste management technology.
Essentially, earthworms function as natural bioreactors. The techniques yields
organic fertilizers, permits safe disposal of certain organic waste and reduces
the requirement of landfills.
Vermicomposting can be conducted all year round, provided environmental
conditions remain within acceptable limits. For increased efficiency, care
should be taken to ensure that organic feed stock and conditions allow worms to
reproduce successfully and to withstand moisture and climate fluctuations. Given
suitable conditions, vermicomposting prepares to provide a relatively straight
forwards solution to the management of compostable organic waste.
Worm Species and Reproduction
Two species of red earthworms have consistently been used for commercial
composting or worm farming, due to their relatively high tolerance of
environmental variations: a) eisenia foetida The Red Wiggler; b)
Lumbricus rebellus The Red Worm.
Earthworms are hermaphroditic – that is, each worm is both male and
female and each can produce eggs and fertilize the eggs produced by another
rworm. Under perfect conditions a mature breeder will produce an eggs capsule
every 7 to 10 days, each containing over 1 doen hatchlings. Development takes
14-21 days and once hached, the newly-emerged worms reach maturity in
approximately four to six weeks, meaning that the worm population may double
each month.
In theory, 1 kilo of worms can increase to 100 kilo (approximately
one million worms0 in a year. However, in working condition 1 kilo may produce a
surplus of 10 kilo in one year, because hatching and capsules (cocoons or eggs)
are usually lost when the vermicompost is harvested. This rapid breeding rate
means the worm population easily adjusts to environmental conditions, feed
supply and the proportion of worm casts to feed and bedding.
Population Controls
Three basic conditions control the size of worm
population:
1.
Food availability
2.
Space requirements
3.
Fouling of their environment
When food waste is regularly fed to worms in a limited space, the worms and
associated organisms break down this waste, absorbing the nutrients they require
and excreting the rest.
As the worms reproduce, competition for the available food
increases. The density of the worm may exceed that favorable for cocoon
production, resulting in slower reproduction. In order for worm populations to
increase, they must be provided with increasing amounts of food, space and fresh
bedding.
Additionally, all the worms excrete castings, which have been shown
to be toxic to members of their own species. As more of the bedding is converted
to castings, worms will migrate, if possible, to areas with a higher proportion
of feedstock and a lower important consideration for municipal-scale composting,
as very large quantities of worms will need to be maintained, depending on the
quantity of organic waste arising and desired rate of throughput.
As previously highlighted, worm populations may increase rapidly
from a relatively small initial number. Once the required number of worms is
present, they should be regarded as a valuable asset, and viewed in terms of
replacement costs. In order to maintain worm numbers, it may be necessary to
harvest a slightly lower grade of vermicompost, before the proportion of
castings reaches toxic levels. Worms separated from the casts conditions, worms
may live as long as ten years.
Castings
When expelled, worm casts consist of granules, surrounded by mucus,
which hardens upon exposure to air. When granular castings are mixed into garden
or houseplant soils there is a low “time release” of nutrients. However, the
hardened particles of mucus do not readily break down. Instead, they serve to
break up soils, providing aeration and improving drainage Worm casts therefore
provide an organic soil conditioner as well as a natural fertilizer.
Nutrient Content
Vermicompost consists mostly of worm casts plus some decayed organic
matter. In ideal conditions worms may consume their own weight of organic matter
each day. One ton of worms may therefore process one ton of organic waste per
day. Vermicompost is organic, non-burning and rich in nutrients. Worm casts are
suitable for a wide range of horticultural uses. Vermicompost contains eight
times as many micro organisms as their feed, which promotes healthy plant
growth.