On June 7, 2021 at dawn, a fire broke out in a slum named “Shaat Tola” in Mohakhali, which burnt 100 kacha houses. It is now becoming normal in Dhaka city and every few months’ interval fire breaks out in different slums and destroy everything. Various examples are there as on August 18, 2019 in Chalantika slum, March 11, 2020 in Rupnagar slum of Mirpur, April 21, 2021 in Balur Mat slum of Uttara and many more. A slight exception of this was the horrific and tragic fire and explosion incident at a mosque in Narayanganj on 6 December 2020, in which around 25 innocent people died and many others were burnt. Fire and explosions in the buildings in Moghbazar in 2021, Gulshan and Sciencelab areas (Mar 2023) are the recently added incidents to this.
For these incidents, we have always blamed the stoves, short circuits or air conditioners as the sources of fire outbreak but one thing is very clear that as soon as these fires start, it spread very quickly to the surrounding and burned down everything to ashes in many cases and sometime causes human death. It is obvious that the stove, short circuit or air conditioners are acting as a source of fire or ignite but there are other reasons behind the rapid spreading of the fire to the surrounding and burning everything to ashes at a glance which we have never thought of.
Scientifically, when household wastes are piled up in a place, various gases start to release after 7~10 days from there which is called the landfill gas. Among them, 90~98% is carbon dioxide and methane. Furthermore, nitrogen, hydrogen, sulphide, ammonia etc. gases are also released from the household waste throughout the next 30~50 years after dumping. Methane gas that emits from these sources can accumulate inside the rooms or buildings through different holes or openings of the floors and walls, if slums or buildings are constructed on the lands filled up by household waste.
On the other hand, every day around 2~2.5 million m3 of untreated sewage waste is discharged to the adjacent rivers and canals from the Dhaka city through open or underground sewerage line. During transportation of sewage, an anaerobic condition is developed when it clogged anywhere which can also releases methane gas which can be accumulated in the building through the sewer connection. Methane is a colourless and odourless inflammable gas which is comparatively lighter than oxygen and it can replace oxygen in a confined space. In the past, our buildings used to have ventilation system just below the roof in every floor which helped us to expel the accumulated light gases inside the room but nowadays there is no ventilation system in place in the buildings which causes the accumulation of methane at different places of the buildings or room.
In the case of Narayanganj mosque fire outbreak, it was clear from the different photograph that the air conditioners and ceiling fans were badly burnt which indicates that there was methane gas accumulation in the mosque from the top of the window to the ceiling and there was no ventilation system under the roof. In Moghbazar and Science lab incident, it was also seen that the explosion took place in the confined warehouse type building where there was big chance of methane accumulation. Not only that the methane emission is limited around the source of emission but it can travel up to 2-3 kilometres around these emission sources. So it is important to take necessary mitigation measures to deal with this issue before escalating into more serious disaster.
For example, in Europe, trespassing is prohibited in sanitary landfill area even after it is closed for operation for up to 25~30 years. Those landfills are designed in such a way that the released methane gas can be collected through pipeline for further use and the bottom layer is covered with impermeable layer so that the ground water is not contaminated by the leachate from landfill. It is important that the methane release is not only a fire threat, but also harmful for human body. It may cause life-threatening diseases like asthma, insomnia, diarrhoea, typhoid and even cancer.
According to a news of South China Morning Post on April 8, 2021, a Paris based organization named Keros Sus reported that they have analysed their satellite image and found that methane emissions have increased alarmingly over Bangladesh. Till now, no one has pointed out the methane accumulation as source of these fire and explosion incidents which could be due to unplanned dumping of municipal solid waste and sewage blockage but it is clear that those incidents happened due to the accumulation of methane there. So, it is high time that we should conceive proper management system in place for household solid waste and sewage disposal to prevent further disaster. Country wise for 180 million people, approximately 90 million kg (90000 tonnes) of household waste is being disposed every day, from which thousands of tonnes of methane and other hazardous gases are being generated every day. Now it is indispensable to take necessary initiatives for proper disposal of domestic waste in the country. Proper disposal of household waste will not only control methane gas, but will also lead to clean and healthy cities, reduce waterlogging, groundwater and surface water pollution, control water-borne diseases and improve overall public health.
The writer is an Environment and Waste Management Consultant based in the United Kingdom. Email: [email protected]
