Mumbai's degraded waste at Kanjurmarg will produce electricity from April. The Rs 4.5 crore Guascor engine from Spain, to convert methane gas into electricity, will arrive at the landfill site on March 25 and the project will be commissioned next month.
If it succeeds, it will be the city's first waste-to-energy project. The earlier one at the Gorai dumping ground for which the BMC even won an award, did not take off. "The engine is already in use in sugar factories, distilleries and even at the Solapur dumping ground where it generates 5MW electricity and is connected to the state electricity board's grid. It will surely work," said Shiju Antony, director, Antony Lara Enviro Solutions. The company has been awarded a 25-year contract for the landfill site.
Of the 141 hectares of salt pan land allotted to the BMC for a landfill site, it has been allowed to use only 66 hectares. Last month, Maharashtra Coastal Zone Management Authority (MCZMA) permitted use of an additional 52.5 hectares of Coastal Regulation Zone-III land for waste processing.
The current technology being used at the landfill site is a bioreactor. Around 3,000 metric tonne of mixed waste is dumped in a 12-hectare cell that has been further sub-divided for proper dumping of waste. When a section is filled with 10,000 metric tonne of it, which takes three days, waste on the fourth day is dumped into a new section. For every four-metre height of waste, two parallel pipes are laid—one to collect the leachate and the other, a perforated one, to collect gas.
The gas is brought to a flaring point where, at present, it is flared so that it does not escape into the atmosphere and catch fire. Once the engine is installed, the pipe will be connected to it and the methane will be converted into electricity.
"Initially we will use it as a captive power plant. The electricity generated will be used by us for street lights at the dumping ground. At present, 3,000 metric tonne of mixed waste daily generates round 380 cubic metre of gas. In the long term, it is estimated to generate 12MW of electricity. Our requirement is 2MW, the rest can be sold by the BMC to generate revenue," said Antony.
It was estimated that methane's release would begin only after 18 months; though, in fact, it started being released within six months. "The quality of waste reaching the dumping ground is largely wet waste and hence the quick generation of methane. There are a lot of plastic bags less than 50 microns and huge quantities of chindi(small pieces of cloth). Plastic bottles and metal are all picked up by rag-pickers, dumper drivers and cleaners as they have monetary value. Very little of it reaches the dumping ground," said Antony. The liquid that drains out from the garbage called leachate has been prevented from seeping into the ground by laying six layers of different materials on the bed of the cell on which the garbage is dumped. Beside the bottom, at every four metres, pipes have been laid to capture the gas and the leachate.
That the leachate does not percolate into the ground is regularly monitored by National Environmental Research Engineering Institute and Maharashtra Pollution Control Board. The leachate is collected in a leachate pond. A leachate treatment plant with a capacity to treat 250 cubic metre of the liquid has also been set up. Some of the raw leachate is recirculated into the garbage depending on the moisture required. The remainder is treated and the water is used for gardening and dust suppression. "This keeps down suspended particulate matter," said Srinivasan Chari, business development manager. The company was awarded the contract in 2009 and is paid Rs 600 per tonne of garbage as tipping fee. Work on waste processing could start only last year as the matter was caught in litigation. Activists had raised issues of mangrove destruction.
At the time, it had said a composting plant would be set up at the site. While the equipment was brought in 2011, work could not start due to court cases. The technology called windrow is being now installed on 12 hectares of landfill site. It will treat another 1,000 metric tonne of waste. "It allows segregation of waste. The plant consists of a material-recovery facility where all recyclable and inert material is separated from biodegradable waste. The latter is put into various cells where the temperature is maintained at 70 degrees centigrade. After 28 days, it will be converted into pure compost."
The dumping mound is maintained at 35 metres on account of aviation restrictions. It's covered with soil so there is no visible garbage except in the area where dumping is on. While stench continues to be a problem though enzymes are sprayed to neutralize it, contractors have set up a citizens helpline (8080032282) to call if affected by it. "We immediately spray the enzymes," said Chari.
Expert's Comment
The waste to energy can be the future of Indian energy source. The potential is huge in the country and with the Govt.initiatives it can become huge business.
It also supports the mission of swachh bharat of the Govt.of India.
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