- The Dhapa landfill, Kolkata’s main municipal dumping ground since 1987, has been causing frequent fires and subsequent air quality deterioration in the city.
- Dhapa has been undergoing biomining and bioremediation, the methods chosen by the National Green Tribunal for clearing legacy waste, which allows extraction of usable materials from the waste.
- Though the project began in 2019, as of February this year, 0.78 million tonnes of the 4 million tonnes of legacy waste has been processed, with the COVID-19 pandemic landing a blow to the progress.
- Landfills are known to greatly contribute to global warming, as they produce methane, a greenhouse gas that possesses global warming potential over 21 times that of carbon dioxide. Municipal solid waste landfills are considered the third-largest source of methane generated from human activities. Methane facilitates fires, which worsen air quality.
The Dhapa landfill, a major unsegregated solid waste dumping ground in Kolkata, has been growing for over three decades, since 1987. It is set to be cleared by June 2024, a target strongly recommended by the National Green Tribunal (NGT). However, there is much left to be done and given the clearing pace, there is concern over whether the state can meet the recommended NGT deadline.
The state government’s latest submissions to the NGT, in April 2023, reveals that about 20% (or one-fifth) of the total four million tonnes of waste has been processed in the one-and-a-half year between August 2021, when the work started and February 2023. This duration is about half of the total period of three years (August 2021 to June 2024), that the state proposed and NGT approved, for the project.
This leaves about a year to clear the remaining 80% of waste, if the state is to meet the recommended end date. It is uncertain what will happen if the deadline is not met – in similar cases, an extension or a fine, from the NGT, is common.
Dhapa has witnessed frequent fires, causing breathing difficulties and eye irritation in people living in the vicinity. According to 2021 findings by the West Bengal Pollution Control Board (WBPCB), the PM10 concentration at the Dhapa site was more than four times higher than the prescribed standard.
Till date, 4,500 tonnes of waste are being dumped at the site daily. Landfills are known to greatly contribute to global warming, as they produce methane, a greenhouse gas that possesses global warming potential over 21 times that of carbon dioxide, according to the Central Pollution Control Board (CPCB). An April 2023 report by the National Oceanic and Atmospheric Administration (NOAA) in the U.S.A, discussing atmospheric methane, says it is far less abundant but much more potent than CO2 at trapping heat in the atmosphere and that, “Methane levels in the atmosphere are now more than two and a half times their pre-industrial level,” it notes. Municipal solid waste landfills are considered the third-largest source of methane generated from human activities. Methane facilitates fires, which worsen air quality.
The Dhapa land was originally part of the East Kolkata Wetlands, which serves as Kolkata’s natural sewage treatment system and was designated a Ramsar site in 2002, as a wetland of global importance.
Dhapa is spread over 35 hectares – a little over half the size of Eden Gardens cricket ground. Of this area, 12 hectares have been closed, capped and covered with grass after covering the waste with geo-textile membrane, with support from a World Bank project. Another 23 hectares are currently active, with new waste coming in while legacy waste still being processed. This area is set to be reclaimed after the waste is processed through bio-remediation (stabilisation and drying) and biomining, a method in which trommels and ballistic separators segregate the stabilised waste for reuse.
The CPCB, in 2019, estimated that “more than 10,000 hectares of urban land is locked” in the form of ‘legacy wastes’ in landfills across the country. Apart from generating methane and causing fires that lead to air pollution, they also produce leachate, a liquid generated by airless waste that pollutes soil and groundwater.
Read more: Tracking methane emissions for mitigation
The journey of Dhapa’s biomining project
Concerned about the environmental impacts of legacy waste (mounds of years-old waste) at landfills across the country, the NGT asked the CPCB to prepare a guideline in January 2019. The CPCB obliged and subsequently released it in April 2019 for all states. On the basis of the guideline the NGT declared biomining and bioremediation as the preferred method for landfill management in July 2019 and asked states to start work immediately.
The biomining project in Dhapa was initiated in 2019, but lockdowns induced by the COVID-19 pandemic delayed its progress. It was formally inaugurated on July 30, 2021, by Kolkata mayor Firhad Hakim, after some experiments at the site. The work began that August and June 2024 was set as the deadline (proposed by the state and accepted by the NGT) for the project to complete processing of waste. Jadavpur University’s civil engineering department was roped in to monitor its implementation.
“The heaps at Dhapa that you see will all be cleared within three years (from 2021 when the inauguration happened). We will process and utilise the waste. We are not subsidising anything. We have only given the land plot. Private enterprises will turn waste into wealth on profitable basis and we’ll get a share of the profit,” said Debabrata Majumdar, member-mayor-in-council of Kolkata Municipal Corporation (KMC), who is in charge of solid waste management, at the inauguration event. Hakim said it was his dream to see a Dhapa free from waste.
However, a recent affidavit submitted by the government to the NGT on April 12 this year reveals that the biomining project managed to process 0.78 million tonnes as of February 28, 2023. Given that it took about 19 months (August 2021-February 2023) to process 0.78 million tonnes of waste, processing the remaining 3.22 million tonnes by June 2024 – or in about 16 months – may pose a challenge.
Mongabay-India requested the municipal authorities for a site visit over email, but was declined. Municipal commissioner Vinod Kumar did not respond, while MMIC Majumdar replied, “We do not allow anyone on the biomining site due to safety and other reasons.”
A KMC engineer who does not wish to be named added, “Since the project is under scrutiny from litigants and the NGT, allowing the media is risky.” The engineer suggested that the government’s submissions before the NGT are the only authentic version of the government’s claims.
“The work picked up pace in the past six to seven months. It will take another couple of years,” Majumdar told Mongabay-India over the phone.
An anonymous government official said that work slows down during monsoon, as the process of segregation becomes difficult. “Ideally, the project should have processed about 4,000 tonnes of waste per day to clear 4 million tonnes in three years. However, the quantity keeps fluctuating due to various reasons and 4,000 tonnes a day is rarely achieved.”
Read more: Assam’s North Lakhimpur treats 40 years of legacy waste in just nine months
The scale of legacy waste and biomining
Six different types of biomining components are being segregated at Dhapa – recyclables, combustible as refuse derived fuel (RDF) materials, C&D waste as non-combustible materials, coarser fraction as filler materials, bioearth or good earth as compostable or soil conditioner and process rejects as residual, stated a 2022 research paper titled Probabilistic Resource Recovery of Legacy Waste in Dhapa Landfill: An Approach of Bio-mining in Kolkata.
Its co-authors analysed a sample material weighing 100 kg and found that 25-30% of the components were non-combustible materials, 10-15% combustible materials, 1-2% recyclables, 15-20% bio-earth, 20-30% coarser organic fraction, 5-10% process rejects and 15-25% evaporated moisture.
Amit Dutta, a professor of environmental engineering at Jadavpur University and a co-author of the study, told Mongabay-India, “Even if dumping of waste is stopped at a legacy waste site, it would take another 25 to 30 years for the emissions from waste to stop on its own. The emission intensity would remain quite high for 15 years at least. Capping has other limitations and associated hazards. Bio-mining, if properly done, can address environmental concerns in a realistic and economically feasible manner.” Dutta is also part of the team from Jadavpur that monitors the Dhapa project.
He said that work has been satisfactory so far, regarding scientific methods of processing and disposal.
Maps by Technology for Wildlife Foundation.
Reusing and recycling segregated waste materials
From the biomining site, the RDF is being sent to cement manufacturing industries and power plants, recyclables are being transferred to WBPCB-authorised recyclers, non-combustible waste to construction agencies and coarser organic fractions are being utilised in non-structural construction in infrastructural projects.
Under ideal circumstances, RDF from the site should be sold to the nearest factory. However, in Dhapa’s case, there is no such facility nearby. This means the fuel must travel 300-600 km. away to factories in Odisha and Chhattisgarh – a redundant practice from an environmental perspective as it increases the carbon footprint when fuel is transported. However, there is no legal mandate regarding the same. “In Odisha, the government encouraged local industries to make changes in their boilers so that RDF can be used as fuel. In West Bengal, no such initiative has taken place as of now,” said a KMC official.
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Banner image: Fire incidents are commonplace in Dhapa. Photo by Snigdhendu Bhattacharya/Mongabay.
