Monday, October 6, 2008
It is perhaps because of the deep-rooted Brahminical aversion among some Indians for all things polluting that India has been hesitant to explore the potential of animal and human wastes to provide energy for direct heating or for generating power. Although gobar gas from cattle dung had been strongly promoted in India’s rural areas with big subsidies, it was not a great success mainly because Indian workers were unwilling to properly maintain these plants. But other countries have fewer inhibitions. With an accelerating world shortage of power and rising costs of fuels, many have started using bio wastes. San Francisco is generating some power from pet poop while several large US farms utilise pig litter and San Antonio generates electric power from human faeces. The world’s seven billion people produce about 140 million tonnes of faeces every day and 25 per cent of this has the potential power to produce roughly 100,000 MW of energy. India, with oneseventh of the world’s population, could therefore generate over 12,000 MW or add almost 12 per cent to its sluggish power generation capacity. Further, as the technology is quite simple and cheap much of this potential can be made available in a very short time. In fact, the technology is so simple and cheap that Rwanda has installed 20 human waste power generating plants of 500 KW each at some of its big prisons where many thousands convicted of genocide are incarcerated. These now provide about half of its electricity requirements. For this initiative Rwanda earned the Ashden Award for Sustainable Energy with a cash component of $50,000. If little Rwanda can achieve this it is very clear that every Indian city and large village can do the same and save their environments from the chronic unhygienic stink that surrounds them. After extracting the methane, the digested human wastes make a virtually odourless fertiliser. Modern, largely automated plants are now available to greatly lessen human contact with bio wastes. If each community could sell the gas or power generated it would also earn enough to install a number of public toilets designed to efficiently collect the waste while also making the communities much more sanitary. But there could be a problem as the state electricity boards would have to accept this power and pay for it. However, as the capital costs are low and the fuel cost is negligible the sale of this power would be much more profitable than power from fossil fuels. And by cutting down the methane emissions that are 30 times more ozonedepleting than CO 2 , such plants could also earn valuable carbon credits. The process is very simple. The waste is first collected and fed into a silo from where it is pumped into a large closed tank or digester where it is simply stirred with electric paddles with a little water and air. The acids, enzymes and other stomach fluids continue the process of digestion releasing methane gas and leaving behind an almost odourless slurry that can be pumped into tankers with tractors to spread it on farm fields as a rich fertiliser. It can also be sun-dried and stored in sacks for use or sale. While the methane can be directly used as fuel, large quantities are difficult to store unlike electricity. Power from human waste will be especially valuable in urban areas but all farm wastes including poultry wastes can be effectively used. Suffolk in the UK has a power plant generating 12.7 MW of energy and consumes 125,000 tonnes of poultry litter per year. Encouraged by its success, it is now planning a human waste plant in Northamptonshire. Many entrepreneurs are discovering that there is gold in these bio wastes and some are trying interesting projects like producing N-Viro, a blend of waste coal dust and dried bio solids that are made into a solid cake that can be fed into a boiler or used as kitchen fuel. When people can lift the blinkers of their prejudices the scope for imaginative and profitable uses of bio waste is limitless.