Double motive
DYNAMOTIVE, a firm in Vancouver, Canada, has come with a path-breaking technology that utilises house- hold waste for removing noxious gases from the exhausts of coal-burning power plants. This technology could spread like wild-fire among the developed nations of the world (The Economist, Vol 339, No 7963).
Going by statistics, an average American generates about two kg of waste each day, 80 per cent of which is organic matter. The process of land- filling has become expensive. In the us, it costs US $30 per tonne (t). Apart from this, each person utilises one kw of electricity per day, much of which is generated by burning coal. To reduce pollution caused by the generation of electricity, scrubbers are needed. To generate 350 mw of electricity and maintain environmental standards, a power plant in a us city with a population of 350,000 would incur a cost of us $100 million, annually.
DynaMotive wants to cash in on this kind of a situation by solving both problems with a single solution. The first phase of the process involves the conversion of organic waste into fuel by burning it at a temperature of 500'c. This process of pyrolysis breaks down the larger organic molecules into simpler forms. The latter burns more easily. About 70 per cent of the organic waste is converted to a clean burning fuel called Ipyrocrude'. In the next stage, pyrocefide is mixed with water and lime to form what is called BioLime. When burnt along with coal, BioLime reacts with the sulphur dioxide (released by the power plant) and converts it into calcium sulphate. The efficiency of Biotime is greater than that of ordinary lime because of the advantages offered by its microscopic structure. BioLime's porous, sponge-like form provides a larger surface area for the sulphur to react, and it captures about 95 per cent of the S02 produced during power generation.
An additional factor favouring BioLime is that it can also remove nitrogen oxides (NOx) (another product of the coal-burning process). Current methods involving the addition of ammonia or urea are expensive. By burning BioLime in a limited oxygen environment, the oxygen from the Nox molecules is removed, leaving behind harmless nitrogen gas.
To prove its worth, the company is building a plant along with the us-based firm Babcock & Wilson, which will produce 25 t of BioLime a day. On approval, they will run a trial test at a coal-fired power station in the state of Ohio. The utilisation of farming and forest waste is also being encouraged.