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

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.

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.

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.

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.