Our muck stinks. We grip our noses tight to avoid the stench and throw our garbage far away, hoping the odour doesn’t trace its way back. Sadly, there’s no escaping the muck monster as it comes back at us in unexpected ways, like climate change. Without good waste segregation practices, more than half of our garbage ends up in landfills—mountains of garbage lining the perimeters of our cities.
Landfills contain a melange of our household waste—wet, organic waste like kitchen scraps, dry recyclables like glass containers and plastic bottles, and hazardous waste like household chemicals and soil. “Since there is a demand for recyclables, the percentage of biodegradables at the landfill site generally increases to 70-75 per cent,” says Shyamala Mani, an independent researcher who has spent decades studying solid waste management in India.
Organic waste damages the planet when it turns up in landfills. As new layers of waste push older layers down in a landfill, the supply of oxygen is cut off from the lower layers of organic waste, forcing it to undergo anaerobic decomposition.
This process releases a cocktail of gases—methane, carbon dioxide, hydrogen sulphide, nitrous oxide, ammonia and others. Among them, methane and carbon dioxide are infamous greenhouse gases that warm up our planet and cause climate change—a driving force behind catastrophes like heatwaves, droughts and floods across the world.
“India is considered to be one of the world's largest methane emitters from landfills,” says Pooja Ghosh from the Centre for Rural Development and Technology, Indian Institute of Technology, Delhi, Methane alone constitutes approximately 29 per cent of the total GHG emissions in India as opposed to the global average of 18 per cent. “According to one estimate, India's total methane emissions are in the range of 669 million tonnes of CO2 equivalent (MtCO2e)”, says Mani, pointing out that landfills are currently the third largest human-generated source of methane.
Quantifying emission
So far, scientists and regulators in India have estimated and calculated methane emissions from landfills with ground-based measurement techniques, some of which are followed globally. However, in countries like India, “correct data is mostly unavailable. It leads to huge uncertainties regarding predicted methane emissions,” says Ghosh. Tracking emissions data at each landfill facility could be helpful in tracking emissions over time.
In a new study, an international group of researchers from the Netherlands, USA and Canada have, for the first time, proposed to detect and measure landfill methane emissions with satellites. The study, published in the journal Science Advances, has measured methane emissions from four landfills across the world—Norte III in Buenos Aires, Argentina; Lakhodair in Lahore, Pakistan; Ghazipur in Delhi and Kanjurmarg in Mumbai.
"We have been looking for methane hot spots around the world using the TROPOMI satellite instrument, among other things to guide targeted high-spatial-resolution observations from instruments like GHGSat," says Joannes D Maasakkers, from SRON Netherlands Institute for Space Research, The Netherlands, and the corresponding author of the study
"These [the four landfill sites] were some of the first urban areas we spotted and followed up with GHGSat who then found emissions from landfills using their high-resolution satellite observations," he adds.
The researchers gathered data about methane hotspots from TROPOMI—TROPOspheric Monitoring Instrument on board the Copernicus Sentinel-5 Precursor satellite—which provides daily methane concentrations in the atmosphere.
They further zoomed in on these hotspots with data from GHGSat, which offers a high-end spatial resolution of greenhouse gas emissions. The combination of two satellite-based datasets helped the researchers zero in on the exact locations of the local methane emission sources.
The study found astounding methane emitted from the four landfills, contributing about 6 per cent to 48 per cent of city-wide emissions, with the volume of emissions 1.4-2.6 times higher. This was even reported to the United Nations Framework Convention on Climate Change (UNFCCC), an international environmental treaty that aims to combat climate change. In Buenos Aires and Mumbai, individual landfills account for more than a quarter of the total urban emissions, while in Delhi, that number stood at 6 per cent and in Lahore, it was at 12 per cent.
“By having facility-level data, we can identify large emitters around the world, aid in targeting mitigation efforts, and track emissions over time,” says Maasakkers. “It’s hard to have that same coverage with ground-based efforts.”
Ghosh and Mani agree that satellite-based monitoring could complement collecting necessary data to have a grip on its emissions. However, such data have to take into effect seasonal and non-seasonal atmospheric changes that might interfere with emission measurements before adopting that as a standard, says Mani.
Tackling landfill emissions
The sight of our waste isn’t pretty from space, and neither is it on the ground. While there are proven methods to reduce methane emissions, like covering active landfills with soil, recovering the biogas produced and converting that into energy, eliminating organic waste from landfills could be the first best step.
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. However, not every city follows these rules by the book.
Besides causing climate change, the highly-flammable methane gas in landfills also fan fires, like those often seen in Ghazipur, Delhi. The inferno not only risks the lives of those who live nearby but also emits toxic gases and particulate matter, deteriorating air quality and posing a health risk in an already-polluted city.
With increased urbanisation and unabated consumption, the waste we generate is expected to grow in the coming years. Between now and 2050, landfill waste is predicted to grow at double the rate of the population in the world. “It is crucial to bring down methane emissions from landfills in India and everywhere else in the world because 11 per cent of methane emissions globally are from households,” says Mani. The first step is to effectively monitor current emissions and design policies that mitigate these emissions.
“Urban local bodies and state governments should refrain from investing in failing technologies and illegal and wrong concessionaire practices,” says Mani, suggesting they “instead look at practices like facilitating a circular economy and providing jobs to the informal sector.”