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Waste Concern is promoting
three types of technologies for composting of organic waste in
Bangladesh.. The technologies are:
Windrow Method with Passive Aeration (Under
Shed)
This
method is similar to windrow method of composting. However, the
only major difference is that the piles are aerated passively through
bamboo aerators. Compostable organic waste is heaped into piles
(under a covered shed of steel angle/bamboo posts and CI sheet roofing
on top), which allows the beneficial micro-organisms to decompose
the organic waste efficiently. In addition, the shed protects the
compost worker from rain and heat of the sun. Pile temperature of
55-65 degree Celsius is optimum for aerobic composting. To enable
the microorganisms to obtain sufficient oxygen, the pile is aerated
using bamboo aerators. In tropical countries, it is likely for the
piles to reach excessively high temperature. Turning along with
the use of bamboo aerators is the method used to maintain the required
pile temperature. Turning associated with watering maintains the
conditions for rapid decomposition and also moves the non-decomposable
materials from exterior of the pile into the interior, thus providing
new food source for the bacteria. Temperature of the pile determines
when to turn. The temperature is monitored and records are kept
of the temperature trends. It takes about 55 days (40 days for composting
and 15 days for maturing) to produce compost using this method.
The process of composting emits very little odor. Waste Concern
is using this method for composting kitchen waste in Mirpur area
of Dhaka City for last eight years.
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Fig
01: A view of windrow method of composting with passive aeration
being operated by Waste Concern in Mirpur, Section-2, Dhaka |
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Fig 02: Front view
of bamboo aerator used for passive aeration of the pile operated
by Waste Concern in Mirpur, Dhaka |
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Box Method of Composting (Under Cover)
This method is very
similar to windrow composting except that frequent turning
is not required for aeration. Air is supplied to the organic
material through perforated box and perforated vertical pipes
embedded in the pile. The vertical pipe provides chimney effect
created by the warm gases rising out of the windrow causes
air to flow through the pipes. Sorted organic waste is placed
in the perforated box, which decomposes aerobically in 40
days and takes another 15 days for maturing. Figure 3, 4,
5 & 6 shows the composting process. Waste Concern has
introduced this method of composting in Baily Road, Green
Road and Dholpur composting plant since 1999.
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Barrel Method of Composting (For Slums)
In this method of
composting, a specially designed 200 litre perforated green
barrel with perforation on the sides and bottom with a lid
is provided to slum dwellers. One green barrel is provided
to a group of six households and placed on a raised base with
concrete ring. The slum dwellers are imparted with training
and motivated to dispose their kitchen waste into the green
barrel. Waste decomposed aerobically into compost in three
months time period. Generally, in low-income settlements major
portion of the waste generated is biodegradable. Slum dwellers
are motivated to dispose their inorganic waste in the yellow
barrel, which is subsequently carried to nearby municipal
dustbins, for final disposal. It was found that from a one
200-litre barrel, compost worth between Tk. 1000-Tk.1200
(US$ 18-20) could
be produced each year. The households sharing the barrel can
also share the income from sale proceeds of the compost. This
model is successful in achieving a behavioural change by minimizing
littering of waste in the slum. The slum dwellers are quite
enthusiastic about the project as they are see the benefits
of clean environment, health benefit and earning extra income
from their waste, which was previously creating pollution
and nuisance in their slum. This model of barrel type composting
demonstrates how slum people can improve their environment,
health along with economic benefits. Waste Concern has introduced
this method of composting in several slum and squatter settlements
in Dhaka, Khulna and Sylhet.
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Fig 07: Sectional View of Barrel
Type Composting Method |
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