Some survivors of last week’s deadly incident reportedly heard some explosions from the direction of some of the buried houses before the collapse of the landfill. On Tuesday this week in parliament, Kyadondo East MP, Haroon Muwada Nkunyingi advanced the possibility that a blast from the garbage might have triggered the incident.
“The witnesses are reporting that it was a blast that blew up the sand and garbage and the smoke. That is the narrative from the residents. They even continue to allege that they saw Chinese installing pipes in the heap of garbage because there were two heaps,” said Muwada.
“We don’t want to imagine and assume that it was a mere slide by the landfill. There is more likelihood that it was either an accident or an intentional mistake or negligence by the Chinese or KCCA,” said Muwada.
State Minister for Kampala, Minsa Kabanda, in response, dismissed allegations that Chinese nationals were operating near the Kiteezi landfill and days before the incident had been seen laying down some pipes. She did not directly comment about the blast. The state minister for Disaster, Lillian Aber did not also address allegations of the explosion. Kiteezi site was developed mainly as a land raise with only limited basal engineering reportedly carried out before landfill development.
Methane gas explosions at landfills are not unprecedented. In 1986, a significant landfill gas explosion in Loscoe, England, injured three people when methane gas accumulated in a bungalow. The explosion was attributed to a lack of understanding of landfill operations and necessary controls, making it a direct consequence of the landfill’s mismanagement.
Another tragic incident occurred in Turkey on April 28, 1993, when an explosion at the Ümraniye-Hekimbaşi open dump displaced a large mass of solid waste, engulfing houses and killing at least 39 people.
Early warnings and risk assessments
Concerns about methane gas explosions at the Kiteezi landfill were documented as early as 2008, under the management of the defunct Kampala City Council (KCC). An Environmental Impact Assessment (EIA) report, prepared by KCC for a gas-flaring project funded under the UN Framework Convention on Climate Change’s Clean Development Mechanism (CDM), warned of the potential for a methane explosion.
The CDM project was part of the World Bank-funded Kampala Institutional and Infrastructure Development Project (KIIDP), which aimed to manage solid waste and reduce harmful greenhouse gas emissions and explosions. The EIA report highlighted the risk of subsurface migration of landfill gas, particularly at older, unlined landfills like Kiteezi.
The report also revealed that the Kiteezi landfill had already outlived its operational lifetime by 2008 and had experienced a collapse on the southeast side, likely due to the subsurface migration of landfill gas. Fortunately, this earlier collapse did not result in widespread exposure to harmful non-methane organic compounds (NMOCs) since there was no habitation on that side of the site.
Landfill gas also includes small amounts of nitrogen, oxygen, ammonia, sulfides, hydrogen, carbon monoxide, and non-methane organic compounds (NMOCs) such as trichloroethylene, benzene, and vinyl chloride.
“Since landfill, gas contains approximately 50 per cent methane (a potentially explosive gas) it is possible for landfill gas to travel underground, accumulate in enclosed structures, and ignite,” said the EIA report.
The report further warned that possibly the biggest health and environmental concerns were related to the uncontrolled surface emissions of landfill gas into the air.
“Landfill gas contains carbon dioxide, methane, VOC, HAP, and odorous compounds that can adversely affect public health and the environment,” it said.
Landfill gasses (LFGS) mostly constitute methane (CH4) (50–60 per cent), carbon dioxide (CO2) (30–40 per cent), and the hazardous air pollutants (HAPs), THC, and volatile organic compounds (VOCs).
Science of gases at landfills
The decomposition of waste also brings about the generation of gases, mainly a mixture of methane and carbon dioxide (about 50–50 per cent in anaerobic conditions), known as ‘biogas’.
Methane is lighter than air and highly flammable. If it enters a closed building and the concentration increases to about 5–15 per cent in the air, a spark or a flame is likely to cause a serious explosion.
Why is methane a fire hazard?
Methane burns very easily and often is used as natural gas for cooking and heating. It is lighter than air and collects at the top of enclosed spaces. When it rises through the soil and enters buildings, it gets trapped in the lower parts of a building, such as the basement.
As more methane enters the building, the level in the air increases. When the methane level reaches 5 per cent of the air, it can cause a fire or an explosion if a spark or flame is present.
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