The Hindu Business Line : Bio-reactor landfill is the solution for solid waste management

Chennai, June 16 Once upon a time, there was a beautiful lake in the heart of Chennai city. It was not big enough to be a source of water, but it formed a pleasant feature in the landscape, a favourite dip-spot for birds and children. But some time in the early 1970s, they began dumping city wastes into it.

The water disappeared yielding place to garbage. However, over time, the Government sealed it and built a monument for the ancient Tamil poet-sage, Thiruvalluvar. The monument is called Valluvar Kottam.

If only the lake was there today! In fact, there were a few other smaller lakes — or large ponds — in the neighbourhood, and they all disappeared in the same fashion.

What happened to them underlines the challenges posed by a problem that has been engaging the attention of the intelligentsia for some time — sustainable solid waste management. The lakes are gone, but the city has grown and there is more garbage and, hence, more need for dumpsites.

Urban Asia generates around 750,000 tonnes of solid waste each day and this is estimated to rise to 1.8 million tonnes by 2025. The only way to tackle this is to recycle.

Of the many researches that have been working on this is one called Asian Regional Research Programme on Environmental Technology (ARRPET), conducted jointly by four institutions in China, Thailand, Sri Lanka and India, and funded by the Swedish International Development Agency. The Indian agency is the Anna University, Chennai.

The programme, which began in 2001, has gone into many ways of waste containment and recycling and is now nearing the conclusion of the second phase. The experiments involved simulating landfills in tanks called ‘lysimeters’ and observing them over many years.

After seven years, the four-nation study has scientifically validated something that is intuitive — that the use of bio-reactor landfill is the way to go about it — but in the process has also determined that there is a good business model behind it.

The problem with open dumpsites is that when it rains, the leachate seeps through the soil and contaminates the neighbourhood. In a bio-reactor landfill, the leachate is trapped and put back into the dump.

The micro-organisms in the leachate help faster degradation of the waste — in about three years. If this degradation happens in the absence of oxygen (anaerobic), then landfill gas — mainly methane — will come out, which could be piped away for use.

The degraded waste could be scooped out, making room for fresh wastes. And out of the scoops, all that is not degraded could be separated. There is value here.

For example, it was found that plastics could be extracted and made into briquettes that could be used as fuel. “The ‘refused derived fuel’ was found acceptable for industrial combustion processes,” says Dr R. Nagendran, Professor at the Centre for Environmental Studies, Anna University.

The experiment also found that useful metals could be extracted out of e-wastes. Using pyrometallurgy (or extractive metallurgy, the science of thermal treatment of substances containing metals to recover valuable metals), experiments also determined that it is viable to produce copper and gold from e-wastes.

All the bio-degraded substances could be used to surface soil anywhere, say parks.

According to Dr Nagendran, there are bio-reactors in many parts of the world, but India is yet to have its first. Such engineered landfills are the crying need of the hour, not only because it is increasingly becoming difficult to find adequate dumpsites near cities, but also in view of the health hazards the open landfills pose.

For example, the study, which also looked into the toxicity of the leachate and particulate matter in ambient air at the Kodungaiyur and Perungudi dumpsites near Chennai, found that the toxic compounds in the leachates exceeded allowable levels.

“Similarly, the particulate matter in air samples varied from 211 to 900 a cubic metre of air, far exceeding the upper limits of 150 prescribed by the Central Pollution Control Board of India,” a report of the study says.

Now, as the ARRPET initiative prepares to enter the third phase, scientists believe that it will produce enough tools for the policy makers for sustainable solid waste management.

Above all, the initiative has provided for a multi-nation network of researches working as a team.

“This exceptional networking has avoided competition among researchers, maximised resources and efficiently used expertise of scientists,” notes Dr Kurian Joseph, another Anna University professor, who was involved with the project.

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More Stories on : Environment | Tamil Nadu

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