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The green, green gas of home

Updated Thursday 3rd April 2008

A biogas plant used in a home in Kerala, India, can teach the west some lessons about sustainability.

Some 50 metres from my hotel with its blue-tinted mirrored solar protection glass is a smart, two storied detached house surrounded by a garden with a lawn, trees, tomato plants and ornamental bushes. This is the sort of home that in the UK would easily cost upwards of £500,000. The gated driveway protects the garden from the cows that, as with anywhere in India, mingle with the traffic. However, unlike most cities and towns in India the tarmac street outside is free of litter - no plastic, no discarded food waste rotting in the sun.

I am in Kerala, a rich state in the southwestern edge of India. Kerala’s wealth is centuries old and based on the spice trade. Here black pepper, cardamom, tapioca, cashews, cloves, nutmeg, cayenne pepper, coffee, cocoa and tea are produced in abundance alongside bananas and coconuts. People here eat well and, unlike many parts of India, they have fish and meat in their diets.

Alongside this affluence Kerala is a “green” state. Road signs urge care for the environment, protection for wildlife and celebrate organic produce. There is legislation to restrict the use of plastic and everywhere bags made from hessian or coconut fibre are available. This is a state where “low tech” solutions are a matter of lifestyle choice and not necessity.

A prime example of this is the biogas plant in the garden of the house near the hotel. The unit costs a total (parts and labour) of around 6000 rupees (£75) and, by eliminating the need for bottled gas derived from fossil fuel, pays for itself in just over two years. Kitchen waste is fed in at one end along with waste “grey” water from washing food, clothes, etc.. Liquid fertiliser used for the garden is produced at the other end. A large reservoir floating over the digestion tank collects the methane produced as the organic material is “eaten’ by methane-producing bacteria.

A domestic biogas plant viewed from the waste entry point, showing the reservoir and gas pipe. Copyrighted image Icon Copyright: Bob Spicer
A domestic biogas plant viewed from the waste entry point, showing the reservoir and gas pipe

This reservoir is weighted down with a small concrete block to produce the pressure that drives the gas through a flexible hose to the kitchen. There is no unpleasant smell either in the garden or the kitchen. The methane, which is a greenhouse gas some 23 times more potent than carbon dioxide and which would otherwise vent to the atmosphere, burns with a pale blue smoke-free flame in a conventional stove and produces carbon dioxide and water vapour free of toxins.

Clearly everybody wins with this system. Organic waste is disposed of without littering the streets or requiring collection, and the garden is fertilised leading to more vigorous plant growth and carbon dioxide capture. The lack of rubbish leads to low rodent and other pest populations. There are no transport costs, carbon or otherwise, in delivering the gas or removing the waste, and above all the energy is free. No wonder that most houses in Kerala have such a system, a system encouraged by the State Government. Perhaps if we in the so-called developed world were to follow India in this instance we too would be financially and environmentally better off.


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