Explained | Why do landfills catch fire and what can we do about them?

The Navy and the Air Force sprayed water from the air over the smouldering garbage at the Brahmapuram landfill.
| Photo Credit: Special Arrangement

The Kochi landfill site around Brahmapuram that caught fire earlier this month was a stark reminder that Indian cities need to be prepared for more such incidents as summer approaches. The fires emit greenhouse gases even as people living around the site were advised to stay indoors and don N95 masks until the fire was put out. These are very short-term measures; preventing these fires altogether requires long-term measures, including thorough and sustained interventions from municipalities.

Why do landfills catch fire?

India’s municipalities have been collecting more than 95% of the waste generated in cities but the efficiency of waste-processing is 30-40% at best. Indian municipal solid waste consists of about 60% biodegradable material, 25% non-biodegradable material and 15% inert materials, like silt and stone.

Municipalities are expected to process the wet and dry waste separately and to have the recovered by-products recycled. Unfortunately, the rate of processing in India’s cities is far lower than the rate of waste generation, so unprocessed waste remains in open landfills for long periods.

This openly disposed waste includes flammable material like low-quality plastics, which have a relatively higher calorific value of about 2,500-3,000 kcal/kg (compared to around 8,000 kcal/kg for coal), and rags and clothes. In summer, the biodegradable fraction composts much faster, increasing the temperature of the heap to beyond 70-80° C.

Higher temperature + flammable material = a chance for the landfill to catch fire. Some fires have been known to go on for months.

Is there a permanent solution?

There are two possible permanent solutions to manage landfill fires.

One: Completely cap the material using soil and close landfills in a scientific manner. This solution is unsuitable in the Indian context as the land can’t be used again for other purposes. Closed landfills have specific standard operating procedures, including managing the methane emissions.

Two: Clear the piles of waste through bioremediation – i.e. excavate old waste and use automated sieving machines to segregate the flammable refuse-derived fuel (RDF), such as plastics, rags, clothes, etc., from biodegradable material. The recovered RDF can be sent to cement kilns as fuel, while the bio-soil can be distributed to farmers to enrich soil. The inert fraction will have to be landfilled.

However, implementing a bioremediation project usually takes up to two or three years, necessitating a short-term solution for landfill fires in the summer.

What are some immediate measures to manage landfill fires?

Landfill sites span 20-30 acres (depending on the size of the corresponding city), and have different kinds of waste.

The first immediate action is to divide a site into blocks depending on the nature of the waste. At each site, blocks with fresh waste should be separated from blocks with flammable material. Blocks that have been capped using soil are less likely to catch fire, so portions like these should also be separated out.

Ideally, the different blocks should be separated using a drain or soil bund and a layer of soil should cap each block. This reduces the chance of fires spreading across blocks within the same landfill.

Next, the most vulnerable part of the landfill – the portion with lots of plastics and cloth – should be capped with soil.

The fresh-waste block shouldn’t be capped but enough moisture should be provided by sprinkling water. The material should also be turned regularly for aeration, which helps cool the waste heap.

Once a site has been divided into blocks, the municipality or the landfill operator should classify the incoming waste on arrival to the site, and dispose in designated blocks rather than dumping mixed fractions.

Already segregated and baled non-recyclable and non-biodegradable waste should be sent to cement kilns instead of being allowed to accumulate at the site. Dry grass material and dry trees from the site should also be cleared immediately and disposed of separately.

In addition, the following precautionary measures will help prevent untoward incidents:

  • Sites should be equipped with water tankers with sprinklers for immediate action.
  • The municipality should work with the nearest fire department and have a plan of action in advance.
  • Waste-processing workers (plant operators, segregators, etc.) should have basic fire-safety and response training.
  • People around landfill sites should also be trained and equipped to safeguard themselves during fires.
  • The municipality should have routine round-the-clock video surveillance of the most flammable portion of the landfill.
  • Flammable material like chemical waste, match sticks, and lighters should not enter the site.
  • Machines at the site, like sieves and balers, should be cleaned and moved away from the flammable material.
  • On-site staff and security personnel should be housed away from the flammable portion.

While these measures can help reduce the fires’ damage, they’re far from ideal and not long-term solutions. The permanent and essential solution is to ensure cities have a systematic waste-processing system where wet and dry waste are processed separately and their by-products treated accordingly (recycling, soil enrichment, etc.). This will need multiple stakeholders, including municipalities and waste-processing unit operators, to cooperate.

For the already-piled-up waste, bioremediation and clearing the site of RDF is the permanent solution.

Considering India’s summer has already begun, municipalities must implement short-term measures to prevent fire outbreaks while also focusing on long-term solutions to improve solid waste management.

Pushkara S.V. is a practitioner at the Indian Institute for Human Settlements. He has provided advisory services on solid waste management to 75 urban local bodies on waste management and has headed operations at a 750-tonne-capacity waste processing facility.

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