Situated very close to the ecologically sensitive Pallikaranai wetlands, which is a part of the National Wetland Conservation and Management Programme, the Perungudi landfill is one of the two major dump yards managed by the Greater Chennai Corporation.
The dump yard is in the news since the government of Tamil Nadu recently told the Madras High Court that it will soon sanction Rs 400 crore to the Greater Chennai Corporation to clean up the Perungudi dump yard using bio mining.
This is not the first time that ‘bio mining’ has been chosen as the go-to method by the authorities to clear up dump yards. Bio mining had successfully helped Kumbakonam municipality to reclaim a landfill in 2016, while it was also announced in Coimbatore in 2019.
Bio mining is a process by which garbage is treated with bio organisms or natural elements like air and sunlight. Speaking to TNM, Satyarupa Shekar, Director for Urban Governance at the Citizen Consumer and Civic Action Group (CAG), says that municipalities would usually dump mixed waste – biodegradable and non-biodegradable – in the landfills over the years.
“The idea of bio mining is to expose this accumulated waste to bio organisms and to air and sun so that the biodegradable waste among the layers get decomposed through the natural process. Whatever is left over will be the non-biodegradable material, which has to be dealt with separately,” she says.
G Prakash, Commissioner, Greater Chennai Corporation, tells TNM that the project will help reclaim 150 acres of land in the landfill, with 100 acres left for dumping garbage. “Every day 5,000 metric tonnes of garbage is dumped in the Perungudi yard. We aim to increase the processing capacity to handle the entire quantity, thereby becoming a zero waste city soon,” he explains. Adding that the land thus reclaimed will be made into a waterbody, Prakash says that the project will achieve its goals in 24 months from the date of starting work.
The process is not as easy as it sounds. It involves a lot of planning with zero margin for error since one wrong step could lead to terrible consequences, such as contaminating the groundwater table or turning the soil in and around the dump yard toxic. There are other challenges as well, Satyarupa adds.
“One of the main challenges that is to be addressed while planning for remediation of landfills using bio mining is what happens to the residual waste,” she points out.
The waste generated by households in Chennai mainly consists of biodegradable, non-biodegradable and sanitary waste. According to Satyarupa, over the years the composition of household waste in Chennai has transformed from being dominated by organic waste to biodegradable and non-biodegradable waste in equal proportion.
While the biodegradable waste accumulated in the dump yard over several decades will be decomposed through bio mining, the non-biodegradable waste that is left behind will be treated separately. “Assuming that all the biodegradable waste has been dealt with using bio mining, what happens to the remaining waste that is non-biodegradable? Where is that going?” she questions.
Another major problem that arises out of remediation of landfills is the possibility of the residual products polluting or contaminating the surrounding areas. Since the products are a combination of chemicals, it is difficult to design a remediation plan that will ensure that there is no harm to the environment. “Without knowing what is in the waste, how can we design a way to know what chemicals are present in a location,” she says, adding that usually the design would be to target major chemicals present in discarded items.
“As a policy research group, we haven’t been able to identify what exactly the government is asking the contractees to do with the waste and what process is being adopted in clearing the waste. Hence that is also a big, open-ended question,” she explains.
Therefore it becomes imperative to ensure that bio mining is carried out in a well-planned manner.
Leo Saldanha, coordinator of the Bengaluru-based Environment Support Group, says, “The task of cleaning a landfill requires that the persons involved in cleaning are not affected adversely due to pathogens and other toxic materials. That’s why careful planning is required depending on the extent of the landfill and the amount of waste accumulated there over the years.”
Leo also points out that it is crucial to have the right equipment to excavate the garbage and segregate it. Another issue that he highlights around adopting bio mining to remediate landfills is the plan to contain the leakage that could occur during the process.
“There must be active efforts for containment so that the residual products don’t flow into the nearby water bodies or soil. There would also be a great amount of ash, which will be highly toxic. So the authorities needs to plan appropriately, keeping all this in mind,” Leo adds. It is recommended that the residue that arises out of bio mining be treated and used in growing flowers, landscaping and other activities where food is not involved.
Once waste is cleared off the land, the area should be filled with healthy soil and stabilised. Experts also recommend planting and growing grass on the soil so that it helps in recovering the nutrients in the soil. “Care must be taken to not let livestock graze on the grass for a few years, until the toxins are completely replaced,” Leo points out.