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Monday, 02 July 2007
India: Organic Digesters Turn Waste into Gas and Electricity

6/19/2007

 

Inter Press Service

Residents in the Indian town of Kadakkal have begun using an unusual energy source to power their street lamps: a wet slurry of garbage that includes food waste and blood from a local slaughterhouse.

Saji Das -- the engineer who created this electricity-generating waste system -- said he's looking forward to the day when people in the state of Kerala will compete over food waste and other rotting organic rubbish rather than holding their noses and walking away quickly.

Das, who developed special organic digesters capable of dealing with a variety of garbage, has become a pioneer of sorts within his state. Kerala, which is located at the southern tip of the Indian peninsula, has human-development indices that rival those of the developed world. Nevertheless, it has a ways to go when it comes to scientifically managing garbage.

Das' digesters are so efficient and clean that Biotech, a nongovernmental organization that he runs, has been named a finalist for Britain's 2007 Ashden Awards, which are sometimes called the "Green Oscars."

It all started in 1994 when Das decided he was tired of seeing mountains of stinking food waste lying about unattended in public places and crawling with flies, rats and other disease-breeding vermin. His strategy was simple: he decided to find cheap, earth-friendly ways to convert what seemed like an endless supply of rich organic matter into valuable methane cooking gas and fertilizer.

Once Das had perfected a digester that worked well on food waste, all he had to do was find the smelliest and biggest dumps in the state's urban areas. He struck gold in the town of Kadakkal in Kollam district.

"The fact that the public in Kadakkal was already agitated over garbage accumulation helped a great deal in seeing through the Biotech project," said M. Nazeer, an elected panchayat (local body) leader.

Workers manually separate the trash into separate piles of wet waste, dry biodegradable waste and recyclable solids such as glass, metal and plastic. For the biogas plant what is most valuable is wet waste -- a rich slurry, which in Kadakkal includes blood and effluents from the local slaughterhouse. The wet waste is run through a pre-digester to optimize bacterial action.

Biotech's integrated waste-recycling plant is equipped to deal with all types of waste generated by markets, slaughterhouses and restaurant kitchens. The success of the integrated plant is that it generates biogas for fuel, electricity for lighting and a valuable organic fertilizer called NPK, which stands for "nitrogen-phosphorus-potash mix. The plant employs five technologies -- biomethanization, biocineration, leach beds, waste water treatment and vermicomposting -- to complete the process.

While the biomethanization unit handles easily degradable materials such as food leftovers, fish and meat, the biocinerator is used to burn slow degrading wastes such as dry leaves, plants and paper. The plant uses leach bed technology to treat vegetables and green leaves. Anaerobic waste treatment is carried out in a special reactor, and the final part of the process employs earthworms in a vermicomposting unit.

"All this can be set up at a cost of just 1.6 million rupees ($40,000), as we know from experience at Kadakkal, which became the first panchayat in the state to produce electricity from solid waste." Das has now set up 10 such plants across the state.

Explaining the secret of his technique Das said: "The usual treatment plants installed in fish markets and slaughterhouses are not capable of dealing with dry leaves and plants. Treatment of fiber-rich vegetable matter creates scum in biogas plants, reducing their efficiency. Burning wastes using an incinerator creates pollution and is wasteful. The solution was to apply different technologies at appropriate stages."

At Kadakkal nothing is wasted. Water is extracted and recycled so that it can be sent back to the abattoirs to help flush them out. The electricity generated by the plant is used to run all the equipment, while the biogas produced by the methanization unit provides all the fuel needed for the incinerator.

Biotech's pride is the bio-waste treatment plant located at Sreekaryam, outside the Kerala state capital of Thiruvananthapuram. This efficient plant is capable of processing 250 kilograms of waste daily and produces 3 kilowatts of electricity.

A.P. Murali, president of the Sreekaryam panchayat, said: "Fish, fruit and vegetable waste generated by the market is fed into the treatment plant and converted into methane gas. Water used for the processing is recycled and fed back into the unit. The methane gas is passed through special biofilters and used to power a generator that supplies electricity to street lamps through a control panel. And the whole unit only cost 700,000 rupees" ($17,000).

Biotech units thrive on human waste. Kumbalangi, a town in the Ernakulam district, which has been declared a model tourism village, has 140 Biotech plants designed to run on waste from lavatories. Kumbalangi also has 800 plants that produce biogas from other wastes, set up with support from the central government and the tourism department.

Biotech plants have many advantages over the old centralized garbage disposal systems. There are no collection and transportation problems, and all the maintenance can be done on site. Plants can be designed and scaled up or down according to the needs of the customer. The popular domestic version needs just 1 square meter of space and manages both solid and liquid waste simultaneously.

Vizhinjam panchayat, in which the international tourist destination of Kovalam is situated, now has 575 homes with garbage digesters installed, and Biotech has a long list of orders.

J. Asuntha Mohan, president of Vizhinjam panchayat, said: "After installing the plants, people here have been able to save substantial amounts of money against expenses on imported liquefied petroleum gas that is used for cooking. We are now trying to install a large recycling plant at Kovalam that can tackle the 1 metric ton of garbage generated daily by the tourism industry."

In its "Annual Economic Review," the state government admitted that only about 50 percent of the 2,500 metric tons of waste generated per day in Kerala is collected for disposal. Every day, about 1,200 metric tons of waste are left to decompose on roadsides and in drains, canals, water bodies and open spaces, according to the review.

Well-known environmentalist and literary figure Sugathakumari said bio-waste digesters are a boon to Kerala. "Our local bodies have no pre-planning. They do not know how to utilize the bio-waste effectively while spending millions of dollars in the name of garbage removal," she said. "The integrated recycling plant solves the critical problem of garbage disposal while producing cooking gas, electricity and organic fertilizer. What more can you ask for?"
 
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