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Earning credit from garbage

mumbai Updated: Mar 25, 2011 01:46 IST
Snehal Rebello

Next year, when a landscaped garden opens in Gorai in suburban Mumbai, people will literally go for their morning walks over tonnes of rotting garbage. The manicured garden will be spread over a 35-metre hillock, which till about three years ago was the Gorai dumping ground where 2,200 tonnes of the city’s garbage was dumped every day.

After a rap from the Bombay high court in a petition highlighting the perils of the overflowing mounds of rotting garbage that emitted methane — a greenhouse gas that damages the ozone layer — the city’s civic body proposed a scientific closure of the open garbage dump site in 2007.

Today, as part of the Brihanmumbai Municipal Corporation’s (BMC) R45 crore closure plan, under the garden lie 36 wells that trap methane gas and toxic leachate water emitted from the 2.3 million tonnes of compressed garbage accumulated since 1972.

The captured Methane gas is flared (burned) at 800-1000 degree Celsius before being released into the environment as harmless air through a 20-foot chimney. This not only contributes to reducing greenhouse gas emissions but will also earn the BMC about R96.5 crore through carbon credits.

Carbon credits are a tradable permit scheme, which provides monetary incentives to developing nations to reduce greenhouse gas emissions. The BMC in 2009 became the first civic body in India to earn and encash carbon credits.


Carbon to credit

In September 2009, the BMC received its first advance cheque of R24.51 crore from the Asian Development Bank based on a 2008 Emission Reduction Purchase Agreement. According to this agreement, the bank would buy carbon credits – measured in units of Certified Emission Reductions (CERs) –generated at the Gorai dump where about 500 to 900 cubic metres of methane gas is flared every day.

One carbon credit is equal to a tonne of carbon. Flaring a tonne of methane is equal to reducing 21 tonnes of carbon. The Asian Development Bank pays $16 (approximately R720) in exchange for one carbon credit. A credit gives the owner the right to emit one tonne of carbon dioxide. “By 2015, the corporation is expecting to receive an additional R72 crore from carbon credits,” said Bhalchandra Patil, chief engineer, solid waste management department, BMC.

The gas released after flaring methane also holds the potential for an alternate source of energy. The BMC is exploring the option of setting up a one-megawatt power plant is at the site in 2012.

Hope stems India is one of the few countries still using open garbage dumping grounds for waste disposal. The success of Mumbai’s Gorai project could give hope to a solution replicable in cities such as Delhi, where huge garbage dumps in Jahangirpur and Ghazipur are a cause for environmental concern. Meanwhile in Gorai, with the mounds of garbage disappearing under the green manicured lawn, local residents are definitely pleased. “The closure has been a blessing,” said Shilpa Desai, local resident. Though the garden is laid, residents will have to wait till 2012 to begin their morning walks. “Within a year, it should be open for the public,” said Suketu Shah, UPL Environmental Engineers Limited, which is carrying out the project.


Wonder garden

In 2006, the Bombay High Court directed the civic body to stop discarding garbage at the Gorai dump yard from January 1, 2008. In 2007, walls with deep foundations were built around the dump yard to ensure that the groundwater from the compacted garbage did not flow into the adjoining Gorai creek.

The garbage was covered with two feet of construction waste. A geo-textile membrane, a high-density protective polythene layer that prevents percolation of rainwater, was laid over it and topped with another protective layer of geo-membrane. The interconnected underground wells can collect methane for 15 years and are connected to an extraction unit. Methane is flared and emitted into the environment. The leachate water is treated before being discharged.

In February 2010, the Gorai project was registered with the United Nations Framework Convention on Climate Change (UNFCC) as part of the Clean Development Mechanism under the Kyoto Protocol. Since then, UNFCC started taking the reduction of greenhouse gas emission into consideration.

Till now, the Gorai project has earned three lakh Certified Emission Reductions (CER) at $16 per CER and 1.25 lakh Voluntary Emission Reductions (VER) at $ 8.81 per VER. Similar to carbon credits, VERs are emission reductions in one of the greenhouse gases that has been achieved voluntarily.

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