Municipal solid wastes converted to
cooking gas
The Financial Express, Tuesday, 02 October 2012
Management systems for municipal solid waste disposal
Mushfiqur Rahman
Solid waste management has been a major problem in our urban life. With
increasing population and growth of per capita income, the volume of solid wastes
is increasing. Also, the nature of solid waste is changing over time and with
development. The study reports in different countries of the world suggest that one
per cent increase in population is associated with 1.04 per cent increase in solid
waste generation and a one per cent increase in per capita income is associated
with 0.34 per cent increase in total waste generation in the developing countries.
Municipal solid waste management in our country will face greater challenges in
future due to the rapid urbanisation and economic growth. The typical problems in
solid waste management are associated with low collection coverage and irregular
collection services, crude open dumping and burning without the considerations of
air and water quality control, the breading of flies and vermin and the handling of
informal waste picking or scavenging activities. Traditionally, municipal authorities
have been carrying out the responsibilities for solid waste management in the cities
and towns.
In Bangladesh, solid waste management is generally based on collecting the waste,
transporting those to the waste dump/land fill area and disposing the wastes there.
The conservancy departments of the city corporations and municipal authorities
use their manpower and logistics supports for collecting the wastes dumped at the
roadside dust beans which accumulate wastes from all possible sources of solid
waste generations including from the households. The wastes, if not collected
timely and disposed of safely, can pollute the surface and groundwater sources,
generate foul odours and serve as sources of diseases and discomfort and threat to
public health. The waste dumps are becoming increasingly difficult to find. Several
studies conducted earlier reveal that people rank improper solid waste disposal in
the cities and towns as the top environmental problem.
In view of the above, progressive solid waste management based on so-called '4R
technology', e.g., reduce, re-use, re-cycle and recover, has been encouraged. A
study conducted few years back suggests that average per capita waste generated
in urban areas of Bangladesh is 0.41 kg. In Dhaka, the waste volume generated
daily is 0.56 kg/capita. In the Paurasava or municipal towns, the daily waste
generated on average is 0.25 kg/capita. Physical composition of solid wastes
indicates that 60-70 per cent of the solid wastes generated in the urban areas of
Bangladesh are food and vegetable wastes. Altogether approximately 80 per cent
of the urban wastes represent bio-degradable organic substances including food,
vegetable, papers, wood, grass, leaves, textile, jute, rags etc. The balance is
inorganic solid wastes comprising of rocks and dart, plastics and rubber, glass and
ceramics, metals etc.
The example of Gaibandha: Gaibandha municipal town is no exception in managing
the challenges of solid wastes. The Gaibandha Pourashava comprises of 10.58 sq.
km area where 12,388 holdings are registered. Approximately one hundred
thousand people live in the town. Compared to many other district towns,
Gaibandha is not a densely populated town and there are open spaces around the
households which people used to use as easy dumping grounds for household
wastes.
But one recent initiative for solid waste management has made the Gaibandha
municipal authority different from others and that put an example forward for
others to replicate. A local non-governmental organisation (NGO), Commitment,
with the technical assistance from an international NGO, Practical Actions, and with
financial support from UK Aid and UNICEF have taken the unique and innovative
solid waste management project in the town. The community workers from the
NGOs made household surveys and identified volumes of generated solid wastes
everyday and identified the habits of waste disposal by the town dwellers.
Gradually the 'Commitment-Practical Action' team members organised cluster
meetings with the participation of household owners. They discussed the impacts
and hazards of the prevailing domestic waste management practices, possible ways
for better management of solid wastes including with segregation of organic and
non-organic wastes, coordinated and convinced the municipal authority for
developing a new system of waste management which is a win-win option for all
the parties concerned.
As a result, a unique solid waste management technology has been developed with
active and enthusiastic participation of the Gaibandha Pourashava dwellers,
municipal authority and the implementing NGOs. Thus, Gabandha has become the
first municipal town which has successfully constructed, and is operating, a bio-gas
plant suitable for processing 1,200 kg solid wastes daily to produce cooking gas
sufficient to meet the need of daily cooking fuel of 40 families. The residual waste,
slurry, suitable for agriculture has been planned for use as organic manure in the
fields. Already a number of rickshaw vans, equipped with green uniformed garbage
collector, roam around in the town. The garbage collectors go door to door, blow
whistle and someone from the households delivers the domestic solid waste to the
van in front of the house daily. The van operator paddles the waste carrying van to
the bio-gas plant installed at the Baniarjan area of the town (the bio-gas plant is a
doom like structure having 6.0 meter diameter and a capacity of 80 cubic meter)
with van full waste. The van is unloaded at the sorting shed which later is
segregated, weighed, shredded and then only the organic waste is put in the
feeding chamber for bio-gas production an anaerobic environment.
The workers pour the shredded organic waste with equal amount of water into the
inlet to the digester for effectively producing bio-gas from the plant. A mechanical
agitator is set to mix the waste and to avoid clogging in the digester. This agitation
facility also allows consistent gas output and process stability, prevents scum
forming as well as settling of sludge at the bottom of the digester. The
decomposition of organic wastes in the closed chamber produces gas which is
collected through a pipe, put at the top of the chamber. The produced bio-gas at
the plant is supplied to nearby households and feed their cooking stoves.
The slurry coming out from the bio-gas plant is a good quality organic fertiliser and
now is planned for supply to the farmers. Generally cow dung and poultry litters
are used in Bangladesh as feed for bio-gas plants. Practical Action Bangladesh and
Commitment were earlier successful in producing bio-gas and organic compost
through processing municipal wastes in Faridpur district, but the plant could supply
bio-gas for cooking only to four nearby households. But the scale of operation in
Gaibandha Paurasava is significantly bigger. The success of bio-gas production
from municipal solid wastes and supplying the gas for cooking to the willing
customers (each of the customers pay BDT 650 per month for getting cooking gas
supply for six hours a day through pipelines) have made both the recipients of gas
and the municipal authority very happy. At the same time, domestic waste
collections from the door steps for feeding the bio-gas plant made the municipal
waste management authority relieved as it has reduced pressure for waste
management for the conservancy department and the town cleaners.
The Gaibandha Pourashava Mayor Shamsul Alam logically considers now the need
for replicating the experience of the installed bio-gas plant and is thinking about
installing more bio-gas plants at different sites of the municipal area for processing
solid waste to cooking gas as well as for wise use of the solid waste of his town.
The writer is a mining engineer. He writes on energy and environment issues.
mushfiq41@yahoo.com