Wattala Pradeshiya Sabha tackles degradable waste
Nandana Edirisinghe from NERD
R. Shanmugapriya, Zonal Manager,
Colombo Zone of WMA
The issue of waste management is a major problem faced by many local
government bodies as dumping of collected solid waste has created
health, social and environmental issues in Sri Lanka.
With the on-going development and programs to beautify the country, a
proper mechanism to manage this waste has become an urgent requirement
for Local bodies.
They are compelled to implement a sophisticated solution to address
this issue especially in densely populated areas instead of just looking
for dumping grounds.
Although there is a demand for a proper waste management system, lack
of mechanisms to tackle this issue has put many of the local authorities
in dilemma. At the same time, the lack of a system to address these
issues has also put the costly efforts made by some institutes to waste.
The bio-gas generation plant in Dickowita in the Wattala area
implemented by the National Engineering Research and Development (NERD)
Centre initiated in 2002 under World Bank funding is one such project
that did not yield the anticipated results.
It is considered to be the biggest-ever bio-gas plant by NERD to
manage degradable waste collected from the Wattala Pradeshiya Sabha, the
administration of the plant was shifted from pillar to post but is now
under purview of the Waste Management Authority of the Western
This plant has 16 digesters (tanks), each with a capacity of 40
metric tonnes to produce bio gas out of the market waste collected from
the area. However, the absence of a proper mechanism to separate
degradable waste to feed this plant, the NERD centre handed over the
plant to the Wattala Pradeshiya Sabha for operational purposes.
The Wattala Pradeshiya Sabha handed it over to a private institute
called Burns Environmental Technologies (Pvt) Ltd in 2004 due to
operational problems and it is now abandoned for years since there was
no proper mechanism to feed the plant with separated market waste.
Garbage being filled into garbage tanks
Digesters being filled with degradable waste.
Pic: Chinthaka Kumarasinghe
It was in such a backdrop under the directive of the Chief Minister
of the Western Province and on the initiative taken by the Wattala
Pradeshiya Sabha, Chairman Thiyagaratne de Alwis the bio-gas plant was
taken under the Waste Management Authority of the WPC in July 2011", R.
Shanmugapriya, Zonal Manager, Colombo Zone of WMA said explaining the
present situation of the bio-gas plant.
The bio-gas plant is now gradually becoming operational as the
required mechanisms are put in place to provide a permanent solution to
the garbage issue in the Wattala Pradeshiya Sabha and the Wattala Urban
Since it was abandoned the tanks were corroded and the automatic
systems were not operational by the time WMA took over the project.
We had two objectives at the time we took over the project. We had to
repair the tanks and had to create a mechanism to separate garbage at
the site to make the plant operational, explaining the challenge faced
by the WMA Shanmugapriya said.
Since it is operated as dry digesters it has to be fed with market
and degradable waste and once the tank is full it has to be covered and
sealed it with water. In a week it emanates methane gas under anaerobic
digestion of the degradable waste and for three months it will generate
Microbes have to be introduced into the tanks and we use cow dung as
the source of mechanisation bacteria. We get about a half feet layer of
cow dung at the bottom of the tank before filling degradable waste into
the tank, she added.
The Wattala Pradeshiya Saba and the Wattala Urban Council has
initiated a (Green Basket); project to collect only separated degradable
waste directly from households and bring it into the bio-gas plant.
The biggest problem faced by waste management is that people are not
yet used to waste segregation in their homes. They dump waste without
segregation and it is difficult to manage the waste. With the
introduction of this Green Basket program this bio-gas plant is in the
process of receiving the separated waste directly to the plant.
We started the green basket program from Alwis Town, Convent road and
Hendala Road and distributed these baskets requesting them to put only
degradable waste into these baskets. If polythene is put into these
baskets we cannot make use of the degradable waste for bio-mechanisation
as polythene is harmful to microbes.
We have set up committees and educated labourers about the mechanism.
We visited the houses and handed over these garbage bins to the people.
We deployed separate vehicles to collect these degradable waste", she
We started the program with 2,000 households and we have expanded it
to 6,000. The entire Hendala area comprises about 15,000 houses. This
year we hope to cover another 6,000 houses to bring the number to
12,000, she said.
The bio-gas plant needs eight metric tonnes of waste per day". We
started the program with two metric tons and now we get four metric
tonnes of garbage per day, she added.
The daily waste collection of the Wattala Pradeshiya Sabha is 35
metric tonnes while the daily collection of solid waste by the Wattala
UC is 22 metric tonnes. The Wattala Pradeshiya Sabha provides six metric
tonnes per day and the Urban Council provides two to three metric tonnes.
This will be a relief for the Wattala Pradeshiya Sabha and Wattala
Urban Council which faced a difficult situation due to the non
availability of a dumping site as the number of metric tonnes of
degradable waste is reducing as the bio-gas plant is expanding its
capacity by increasing the number of tanks with the support of the NERD
According to Nandana Edirisinghe, of NERD this bio-gas system is
based on the NERD design of dry garbage.
Now the WMA is of the view that it is feasible to deviate from the
dry batch system because it requires an open system for a longer time
but a bad odour emanates. They request to convert it to a continuous
system. The advantage of a continuous system is that it feeds the tanks
daily and has a water seal. As a research project NERD undertook to
convert two digesters to the continuous system, he said.
That is the project we have at present. We signed an MoU with WMA for
another project to make use of the bio-gas to generate electricity. At
the moment they are operating two or three digesters. We are trying to
use our own engine and bring it here and fix it as a research to operate
a chopping machine from the electricity that it generated by using the
gas", he said.
The plant needs to chop vegetable waste and the chopping machine
requires 11 kilo watts for this operation.
We want to see whether we can generate power and operate the chopping
machine. Based on the results of that project the WMA will try to expand
and generate its own power for lighting and other purposes.
That is the project we have undertaken at present".
We measure 50 to 55 percent of methane gas production from one tank
and that is acceptable to generate power. We have to clean the gas
emanating from the digesters, after removing the hydrogen sulphide", he
Initially, the plant needs 11 Kilowatts and we can increase it
operating two to three digesters simultaneously. That is enough to
generate power to operate the chopping machine. If it is successful we
can fill all the digesters and generate power from the power generator
and generating a maximum of 20 Kilo watt. Based on our research output
the WMA will purchase a better generator to produce more electricity, he
According to Shamugapriya the WMA is thinking of modifying the plant
further. At present we are operating only two digesters and at the end
of August based on the research findings we are going to develop another
three digesters, she said.
There is a huge demand for the collection of fish and meat waste.
This can't be done on our own because they are nitrogen sources and good
for bio-gas. But the problem is the odour. As the covers of these
digesters are open it will emanate a bad odour. At present we are only
concentrating on food and vegetable waste. Otherwise we can make use of
the other degradable waste and increase the efficiency of the bio-gas
Almost 55 metric tonnes of waste is generated both from Wattala PS
and Wattala UC area and out of that 60 per cent is degradable waste. In
the future we will be able to get more than 30 metric tonnes of
degradable waste both from Wattala UC and PS to develop this project and
to cover the entire Wattala area. So daily we can use 30 metric tonnes
of waste and the bio-gas plant can provide a solution for more than half
of the garbage collected from Wattala area.
That covers the entire degradable waste in Wattala area and after
that we have only polythene, plastic and other non degradable waste.
This is not a problem and people can store them for weeks. If they start
the segregation practice, waste is not a problem", she said.
The WMA has purchased a bail machine to crush plastic to be operated
by the electricity generated from the plant. "So the WMA will also be
able to accept the plastic and polythene also for this plant in future,
The incinerator that is being installed at the plant will provide a
solution for the waste collected from the area by making use of the gas
produced from the plant, she said.