MUMBAI: In a landmark for carbon financing in India, the municipal corporation of Greater Mumbai has earned Rs 26 crore for the scientific closure of a garbage dumping ground.

The cheque from the Asia Carbon Fund of the Asian Development Bank (ADB) is an advance for future delivery of carbon credits. The money essentially is for the capture and combustion of methane gas emanating from the dump which results in a substantial reduction of greenhouse emissions. Before giving the money though, the ADB had the project scrutinised by independent validators.

Carbon credit consultants say the deal is one of the largest Carbon advances under the Clean Development Mechanism to a municipal corporation. "We hope to earn a total of Rs 73 crores from the Gorai dumping ground carbon credits, which would be Rs 11 crores above the entire cost of the project,'' said additional municipal commissioner R A Rajeev, who drove the project from start to finish.

As heartening as the cash-from-trash bargain is the transformation of the 50-acre dumping ground, more than twice the size of the Oval Maidan, from a stinking mountain of garbage into a contoured, landscaped hill. The initial plan for a golf course here seems too optimistic but it can surely serve as a public park after three to fours years by which time the settlement underneath will be complete.

Garbage was being dumped at this plot adjoining the Gorai creek since 1972. Thirty-five years later when the dump was closed in December 2007, it was receiving 2,200 tonnes of refuse a day and the 2.3 million tonnes of accumulated waste had stacked up to 32 metres, as high as an 11-storey building.

By this time, the urban sprawl had reached the edges of the dump and pressure from local residents in the form of agitations and law suits played its part in expediting its closure.

The municipal corporation had signed an Emission Reduction Purchase Agreement with the ADB, wherein the three lakh Certified Emission Reductions (CERs) generated at the Gorai dump would be sold to it.

The contractors, United Phosphorus Ltd (UPL) and their joint-venture partners, Vanderwiel Strotgas BV, basically flattened the top of the garbage mound and created gentler slopes after which it was sealed in three layers of dense plastic at varying depths. The plastic sheets prevent the seepage of rainwater and the formation of leachate, a cocktail of highly toxic compounds.

Over the topmost plastic sheet is a two-feet layer of construction rubble topped by one foot of earth which supports foliage in the form of grass, shrubs and small trees with shallow roots.

"An intricate subterranean network of pipes collect the gases, 70% of which is is methane, from the rotting garbage and relays it through 40 wells to a chimney where it is flared,'' explained Sundar Balasubramanian, UPL's vice-president, Environment Business. One tonne of methane is equivalent to 21 tonnes of carbon dioxide in terms of global warming potential.

To prevent the leachate from seeping into the creek, a seven-metre deep concrete wall has been built into the edges of the dump. Whatever leachate is formed because of the existing moisture is channelised into a processing tank to neutralise its toxicity. "Earlier, the mangroves ringing the dump had turned brown because of the water pollution but now they have regenerated,'' said P S Awate, executive engineer of the civic corporation's solid waste department, pointing to the dark green foliage on the fringes of the dump.

What are Carbon Credits

Carbon credits are a key component of global attempts to mitigate the growth in concentrations of greenhouse gases. One Carbon Credit is equal to one tonne of Carbon. Carbon trading is an application of an emissions trading approach. Greenhouse gases are capped and then markets are used to allocate the emissions among the group of regulated sources. The idea is to allow market mechanism to drive industrial and commercial processes in the direction of low emissions. Since greenhouse gases mitigation projects generate credits, this approach can be used to finance carbon reduction schemes between trading partners round the world.