There are two separate challenges of solid waste management in our cities: One, managing the continuous flow of solid waste on a daily basis, and two, dealing with the legacy of neglect which has resulted in garbage hills having been built up at dumpsites that were meant for waste processing and landfills.
The sites for landfills were originally located outside of the cities, but as the cities have expanded the dumpsites are now almost inside the cities. Delhi’s open dumps at Ghazipur (69 metres high), Okhla (55 metres high) and Bhalswa (56 metres high), for example, are all much higher than the permissible height limit of up to 20 metres, and way past their capacity for holding the amount of waste for which they were set up. It is estimated that more than 10,000 hectares of urban land is locked in these dumpsites in India.
In the absence of exposure to air, the high-rises of rotting mixed waste on these sites generate methane (a greenhouse gas) and other landfill gases which contribute to global warming. They also produce leachate (liquid generated by airless waste), which pollutes groundwater. Frequent outbreaks of fire at the dumpsites lead to air pollution. What is more, the presence of these dumps encourages further dumping at these sites even though they are filled beyond capacity.
Many municipal authorities across the country are opting for “capping” as a solution to the legacy of mixed waste. In Delhi itself, the South Delhi Municipal Corporation is working on capping the Okhla site and hopes to complete this task by the end of 2019. It is important, therefore, to study the environmental and financial implications of choosing capping of a dumpsite as opposed to bio-remediation and bio-mining, particularly since the Solid Waste Management Rules 2016 (the Rules) have clearly indicated that bio-treatment of the legacy waste is the preferred way.
Bio-remediation and bio-mining are clearly specified as the first choice under Rule 15 (zj) of The Rules for the Safe Treatment of Legacy Waste in all open dumpsites and existing operational dumpsites in India. We had earlier described the simple low-cost solution of bio-remediation and bio-mining in our column, ‘A city laid waste’ (IE, June 28, 2017), explaining how it effectively reduces the volume of the waste, addresses the issues of pollution and global warming, and also frees up land for beneficial uses. Rule 15(zk) of the Rules specifies that only when bio-remediation and bio-mining of dumpsites are not possible, should the waste be scientifically capped as per landfill capping norms.
The problem arises because the Rules do not specify any criteria for determining whether bio-remediation and bio-mining are possible or not. An obvious constraint will be imposed by geography: Waste thrown down steep narrow valleys in hill towns, for example, may not be accessible for bio-treatment. A possible criterion could be whether the organic content of the waste is less than 10 per cent in the total mixed waste, which would suggest that the waste has already stabilised and has very little organic substance left for microbial action and does not require bio-remediation and bio-mining. Just as the Rules define combustible waste suitable for waste to energy, the Rules could also define the quality of waste suitable for bio-remediation.
In the absence of clear technical norms and a lack of clarity on the exemption for geographical constraints, municipal authorities are left with the discretion in dealing with the mounds of legacy waste. The result is that capping is being projected in Indian cities as a solution to the challenges posed by our unlined open dumps even where bio-remediation and bio-mining are feasible and desirable. In doing so, municipal authorities often draw a false parallel with the closure of scientifically engineered landfills abroad, which start with underground pits that have good bottom and side liners, and proper piping and gas extraction systems to prevent the escape of leachate and gases. Capping unsegregated waste, which has been lying at the dumpsites for decades with an impermeable layer of gravel, high-density polyethylene and soil, and not exposing it to air, is very different from scientific closure.
The danger of capping of untreated dumpsites without adequate precautions was driven home (or was it?) by what happened at the Mindspace Commercial Complex built to international standards at Malad in 2007. The complex was built on what was a dumpsite in a low-lying area. Neither was the site treated/capped, nor was it left alone for the mandatory period of 15 years without building on it. When MNCs and other high-end companies moved into the complex, they encountered constant disruptions in the functioning of their office equipment. Corrosive landfill gases (containing methane, hydrogen sulphide, mercaptans and other sulphurous compounds) were being released from the unscientifically closed dump into the basements of the buildings nearby. After technicians failed to zero in on the cause of the constant breakdown of computers and air-conditioners in the Mindspace office complex, it was Amiya Sahu, an environmental scientist and president of the National Solid Waste Association of India, who discovered through air testing in and around the office complex that the culprit was the unscientific closure/capping of the dumpsite and premature construction of buildings on the site
Another capping disaster is at Bengaluru, where the Bagalur quarry, full of untreated waste, has been covered with a garden. Landfill gases are bubbling vigorously up through leachate almost at ground level in six unused leachate extraction wells.
By contrast, Ambikapur, a small town with a population of 150,000, in Chhatisgarh provides a good example of how to go about correctly capping a dumpsite. In 2016, C Srinivasan of Vellore first set up a decentralised waste management system in Ambikapur to prevent any fresh waste reaching a 40-year-old dumpsite of nine hectares. Next, the legacy waste on the dumpsite was fully stabilised. For aeration, it was moved in six-inch layers to the boundary of the site, and inoculated with a natural bio-culture of cow dung, cow urine and jaggery before adding and inoculating another layer, up to a total height of nine meters. The boundary wall was thus replaced by a 900-metre-long bund with a 15-metre-wide base, 7.5-metre-wide top and stable 45-degree slopes. The area was seeded with 100 kg of ragi seeds mixed with 100 kg sand, then fully covered with porous jute netting. This prevented birds from eating the seeds and retained the moisture from sprinklers. The heap has naturally shrunk to half its original height and is a wonderful green hillock of dense self-seeded ragi grass covering an area of 1.2 hectares. The remaining area is now a popular Sunday picnic park that replaced a stinking landmark beside the highway into town.
The Ambikapur example illustrates what we have often pointed out. Good things are happening in small experiments, but they are not being used to set larger policies right. The Ministry of Environment and Forests and the Central Pollution Control Board should swing into action immediately to issue guidelines on the capping of dumpsites, taking account of health, environment and financial perspectives. And what is more, they should strictly monitor compliance.