Bio-Digesters in India: Nothing Wasted, A Lot More Gained


In the tropical green south Indian state of Kerala, there is a fresh strategy of dealing with an old problem of waste: specially designed, efficient organic 'digesters' that turn solid waste into energy.

Beginning in 1994, a local NGO called Bio-tech pioneered the development of their 'integrated waste recycling plant,' where large amounts of organic waste generated by the markets, slaughter houses, and restaurant kitchens are treated and converted into methane (cooking gas) and fertilizer.

Saji Das, the man behind Bio-tech, then chose town of Kadakkal in Kollam district (which fortuitously had the largest dump in the state) as the location for the first integrated recycling plant. Today, the plant is capable of digesting daily one tonne of waste — producing three kilowatts of energy — enough to power 120 street lamps.The conversion process begins with the manual segregation of wet waste, dry biodegradable waste and recyclable solids like glass, metal and plastic. The plant utilizes five technologies in order to complete the transformation of waste to energy in the form of biogas, namely biomethanization, biocineration, leach beds, waste water treatment and vermicomposting.

Wet waste — including blood and other waste matter from the slaughter house — is critical in producing biogas and is actually run through a pre-digester in order to boost the bacterial action that will break the waste down further. Once the process is complete, it generates biogas that can be used as fuel, in addition to electricity used for lighting and organic NPK (Nitrogen-Phosphorus-Potash mix) fertilizer.

No waste is left behind, as the different components of the Bio-tech integrated recycling plant are designed to address specific types of waste, which distinguishes them from traditional, less-efficient treatment plants. For instance, the biocinerator unit is designed to handle wastes that degrade slowly, such as paper, dry leaves and plants, while the biomethanization unit processes all organic waste. The leach beds dispense with vegetable matter. Anaerobic waste treatment takes place in another separate unit and the final process incorporates earthworm action in a vermicompost unit.

Back at Kadakkal, this thorough efficiency is reflected in the reuse of water that is extracted and recycled so that it can be sent back to flush out abattoirs. Electricity produced by the plant is used to run all the equipment, while the incinerator runs only on the biogas produced by the methanization unit.

Das has now set up ten such integrated plants all over Kerala. In towns such as Kumbalangi, environmentalism and tourism have joined forces in transforming it into a "model tourism village" where, with government support, 140 Biotech domestic units have been designed to run on human waste from lavatories, in addition to 800 units that convert biogas from other wastes. Other municipalities, such as the tourist-friendly Kovalam, are following suit as well.

In the larger scheme of things, these integrated recycling plants make conventional, centralized garbage disposal systems look like, well, junk. There is no need to address the challenges of collection and transportation and all maintenance happens on-site. The units themselves can be tailored to suit the requirements of the customer and the domestic version only needs one square metre of space — and manages both solid and liquid waste at the same time. Costs to imported Liquefied Petroleum Gas (LPG) for cooking are saved.

In a state where its 'Annual Economic Review' published by the government shows that only 50 per cent of the 2,500 tonnes of waste created per day in Kerala is collected for disposal — and where the tourism industry generates additionally one tonne of waste daily — the bio-waste digesters are looking like an ecologically-effective and versatile way around the looming spectre of the waste problem in India and beyond.::InterPress Service
::The Hindu

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