Efficient management of waste disposal sites can curb air pollution
The practical way to deal with such legacy dumpsites, which are a source of local air pollution and fire accidents, is to stabilise the slopes. We must start recovering the landfill gas and then either flaring or harvesting it to be used as a potential fuel.
In 2016, India revised the Solid Waste Management Rules, banning dumping of mixed waste in low-lying areas and open dumps. Yet, many such waste disposal sites are still operational in Delhi and Mumbai. Many of them have gone beyond their permissible operational period because there are no alternative sites. Such sites are now as high as 50-60 m above the ground level, and have also become unstable because of garbage disposal. In October last year, one side of a Ghazipur waste disposal site, managed by the East Delhi Municipal Corporation, collapsed, killing at least two people.
However, the stability of the slope is not the only concern in terms of waste disposal sites. Combustibles such as rags, plastics, paper and wood often catch fire. These surface fires emit particulate matter, including black carbon or soot, which is a short-term climate pollutant with global warming potential. While dousing such fires is relatively easy, subsurface fires are not. This occurs when biodegradable waste degrades anaerobically and produces landfill gases. The main component of landfill gas— methane — catches fire when it comes in contact with air. It is often challenging to quantify the actual spread of fire in the subsurface.
Such fires, whether surface or subsurface, contribute to local air pollution. Waste disposal sites thus also contribute to an increased level of local air pollution and often add to the haze during the winter season. This phenomenon, which occurs every winter in Delhi, was also evident in Mumbai a few years ago. The ambient air quality monitoring around the active waste disposal sites has indicated higher levels of particulate matter, carbon monoxide (CO) and methane than the prescribed standards. Apart from these pollutants, emission of traces of hydrogen sulfide (H2S) from waste disposal sites is also a concern as even its small concentrations are toxic to humans. As per the TERI study, the landfill fires contribute to 0.4% of air pollution in terms of PM2.5 in winter season in Delhi.
The present practice of using fire tenders for dousing waste dumpsite fires not only introduces water into the landfill which later percolates through as leachate, but also washes away good quality soil cover from the top of the slopes thereby exposing the waste.
The practical way to deal with such legacy dumpsites, which are a source of local air pollution and fire accidents, is to stabilise the slopes. We must start recovering the landfill gas and then either flaring or harvesting it to be used as a potential fuel. Once these dumps have been stabilised and most of the landfill gas recovered, the dumps can be opened, and their content mined into compostable, combustibles and inerts. The combustibles can be further processed into refuse-derived fuel (RDF) and used as a source of energy, either in industries or cement kilns. This can be done cell by cell on the disposal sites. The emptied cells should be lined and converted into sanitary landfills so that scientific disposal of residues of waste processing can be initiated, in compliance with the waste management rules of 2016.
Suneel Pandey is director, environment & waste management, TERI
Source: Hindustan Times, 14/11/2018
