More than a quarter of methane emissions in Mumbai – which generates the most solid waste among India’s metro cities – originate in its landfills, a study has shown. Methane is a potent greenhouse gas and tackling emission sources that can potentially be mitigated, and reduce global warming, is crucial.

Apart from causing a major health and social impact, such as contamination of water, fire outbreaks and a rotting odour, landfills emit methane when organic waste such as food scraps, wood and paper decompose. It is estimated that, globally, 30-70 million tonnes of methane is emitted from landfills each year. In India, the waste sector accounts for about 20% of methane emissions, as per the Global Methane Tracker 2022.

Methane is a greenhouse gas 28 times more potent than carbon dioxide at warming the atmosphere over a 100-year period and is responsible for almost a quarter of global warming. Reducing methane emissions is a priority for curbing climate change, IndiaSpend reported in July.

Climate change mitigation, according to the United Nations Framework Convention on Climate Change, refers to efforts to reduce or prevent emission of greenhouse gases. Waste-related emissions, such as methane, can be mitigated through the use of new technology like waste-to-energy plants; making existing units, such as waste management facilities, energy-efficient or by changes in behaviour, such as less wastage of food.

A study published in August by researchers from SRON Netherlands Institute for Space Research and GHGSat Inc., a global emissions monitoring platform from Canada, found that more than a quarter of methane emissions (26%) in the metropolitan city of Mumbai originated in landfills. For national capital Delhi, landfills accounted for 6% of methane emissions.

The waste problem

Every day between the years 2016 and 2020, Greater Mumbai generated between 6,500 and 9,400 million tonnes of waste, as per a June 2021 report published by the Praja Foundation, a Mumbai based not-for-profit working on accountability and governance issues. Most of this waste is dumped in three main landfills of Mumbai: the Deonar dumping ground, Kanjurmarg and Mulund dump yards. While the Mulund dumpyard has been closed for waste disposal since 2018-’19, the Deonar and Kanjurmarg dump yards received up to 1,700 and 5,500 million tonnes of waste, respectively, in 2019-’20.

“In India we don’t have many landfills made in a scientific manner. Landfills are basically dumpsites outside city boundaries; they eventually become bigger landfills. But under Central Pollution Control Board, there is a provision on how landfills need to be treated, which many cities do not follow,” said Pratima Singh, senior research scientist at the Center for Study of Science, Technology and Policy, a Bengaluru-based think-tank, where she leads the air pollution domain.

“When your wet waste and dry waste is not segregated and dumped in an open area, this in presence of oxygen gets degraded further – through a process called aerobic decomposition–with help of microorganisms, and in 20-21 days the decomposition starts releasing methane,” she added.

In 2021, the per capita per day solid waste generation across 28 selected cities of India was in the range of 190 gm to 990 gm, with the average being 390 gm, as per a joint study by the Niti-Aayog and the Centre for Science and Environment. Bigger and more affluent cities have been adding more waste per day, the study noted.

With increased urbanisation and unabated consumption, the waste we generate is expected to grow in the coming years. India will, in a couple of decades, generate nearly thrice the waste it currently does – “165 million tonnes by 2030 and 436 million tonnes by 2050”, according to a June 2021 report by the Ministry of Housing and Urban Affairs. Only 22%-28% of the waste now collected is processed or treated.

Estimating landfill emissions

No government authority is continuously monitoring methane emissions from landfills. For reporting purposes, they collaborate with other organisations for a specific period of time, experts told us.

For instance, in 2006, the Central Pollution Control Board, in collaboration with National Environmental Engineering Research Institute, Nagpur, and the Indian Agricultural Research Institute, Delhi had made an attempt to assess the status of methane emissions from dump sites. Most data are also dependent on satellites, experts added.

Using satellite data to detect methane emissions is still relatively new, but it is being brought to use more widely. It also means that several independent organisations are tracking greenhouse gases, data on which were earlier only provided by the government.

IndiaSpend’s Chasing Methane is one such attempt to track methane emissions across sectors from India. In the first phase, the project presents data from the European Space Agency’s Sentinel 5-P satellite at 1110-metre resolution, along with an emissions inventory from the Copernicus Atmosphere Monitoring Service. The data gathered between January and September 2022 show that metro cities like Mumbai, Pune and Bengaluru are some of the highest methane emitting cities in the waste sector in India.

Apart from satellite data, the Intergovernmental Panel on Climate Change provides two models to estimate methane emissions from landfills: the default method and the first order decay method.

The default method is simple and it assumes that all methane emissions are released in the same year of waste disposal. It uses the quantity of waste generated and disposed to estimate the amount of methane released. The first order decay method looks at methane emissions across time periods.

These two methods also provide very different figures for methane emissions. For instance, a 2016 study by researchers from Delhi Technological University found that methane emissions at Ghazipur landfill in the year 2011-’12 under the Intergovernmental Panel on Climate Change default method was 3,845.20 gigagram per year, while under the First Order Decay method the emissions come up to 2,611.99 gigagram per year (1,000 gigagram equals 1 million tonnes). This is equivalent to emissions from 17-25 coal fired plants in a year.

The limitation in estimating methane emissions from landfills is the lack of data on municipal solid waste generation and actual disposal in landfills, said Singh. This is also exacerbated as legacy waste, or waste that has been collected and kept for years, is considered.

While methane capture at landfills is urgent, there are discrepancies between estimated methane emission provided by technology like satellites and what was happening on the ground, according to a Massachusetts Institute of Technology report. “A new airborne methane sensor deployed by NASA, for instance, found that California landfills have been leaking methane at rates as much as six times greater than estimates from the US Environmental Protection Agency,” the report noted.

Further, satellites with more precision are set to be launched in 2023, including the Environmental Defense Fund’s MethaneSAT, which aims to track not only the rate of methane emissions and location but also how those emissions are changing.

Earlier in November, at COP27 held in Egypt, the United Nations launched a high-tech, satellite-based global methane detecting system called Methane Alert and Response System. It was developed as part of the Global Methane Pledge, signed by 103 countries to cut 30% of methane emissions by 2030 from 2020 levels. The system is intended to provide data to governments and businesses and allow them to act on mitigating the emissions.

Policies on landfills

Between now and 2050, landfill waste is predicted to grow at double the rate of the population in the world. Experts noted the need to monitor emissions from landfills and design policies to mitigate these emissions.

Further, the government has also been implementing policies to deal with the waste problem in cities. For instance, the Solid Waste Management Rules of 2016 mandate segregation of waste at the household level and urban local bodies need to transport them separately in collection vehicles.

Policies for landfills are definitely there, but cities have failed to follow them, which is why we are dealing with the problem of legacy waste, said Singh. “Many cities are now trying to come up with solutions, like incineration, or transporting the waste to another area, which are not the solution. The first and foremost solution is that we segregate the waste at household level.”

We reached out to the Central Pollution Control Board and asked them if they maintain data on methane emissions from landfills and for comment on policy measures taken to contain these emissions. We will update this story when we receive their response.

“The regulatory framework on waste management has been very strong, but the implementation has been very poor,” said Priti Mahesh, chief programme coordinator at Toxics Link, a not-for-profit focussing on environmental issues. “There is also no monitoring of recycling facilities; whether any standards are being met or whether they are different from what was happening in the informal sector?”

Central Pollution Control Board’s annual report 2020-’21 shows that of 1,50,847 tonnes of waste collected each day, only 47% or 70,973 tonnes per day was treated in 2020-’21. Further, 27% or 40,863 tonnes of waste ended up in landfills and 25.8% or 39,010 tonnes each day was completely unaccounted for.

“While standards are being created by Central Pollution Control Board, enforcement is a state subject under state control boards. And, due to the lack of capacity in terms of resources available to them and knowledge of it, not much action is happening on ground,” noted Mahesh.

Furthermore, technology adoption to contain methane emissions in India is limited, as per studies. In the United States, landfill gas emissions declined by 40% from 1990 to 2016 through methane abatement strategies such as landfill gas collection and control systems, according to a March 2019 paper by Veera Pekkarinen, supported by the European Union’s ClimaSlow project. The study noted that there is potential to spread these technologies to developing countries.

The government has also initiated waste to energy plants for generating energy from municipal solid waste. But improper handling of organic waste has been identified as one of the root causes for failure of waste-to-energy technology, according to a 2017 study. Further, it has often been found that adoption of such practices have not only increased the cost of waste processing, but also bring environmental and health hazards if not managed properly.

“Measuring methane from landfill sites doesn’t specifically fall under the mandate of [a] municipal authority. Only when they are asked specifically by Central Pollution Control Board on emissions from the landfill sites, is there a study conducted,” noted Singh. “So there are no specific solutions that target the emissions apart from general solutions on treating the waste problem.”

This article first appeared on IndiaSpend, a data-driven and public-interest journalism non-profit.