Fuel from plastic wastes and chemicals from grains: researchers in UK experiment with innovative substitutes
john Dwyer, head of Centre for Microporous Materials in Manchester, uk, has introduced several projects to conserve natural resources ( Spectrum , No 255). One such project is distillation of fuel from dirty, mixed plastic waste -- hardest of all waste products to recycle. This would help replace petrol.
Dwyer has developed zeolites -- crystalline aluminium silicates -- for producing fuel. Engineering zeolites makes it possible to use them as catalysts in the distillation of fuel from wastes. Since it would contain no lead but still have a high octane rating, this gasoline-type fuel has been named 'green fuel'. This would also help solve the environmental problem of disposing off this non-biodegradable waste.
The distillation process involves heating of plastic in an oxygen-free environment to prevent it from burning; the hydrocarbons are distilled off as vapours which are collected after they cool. But since plastic exists as polyvinyl chloride (pvc), it pro-duces hydrochloric acid when heated. Dwyer's team has shown that this acid can be broken down into a harmless compound by adding an appropriate zeolite catalyst during distillation.
Till now, the use of zeolite crystals in such roles was limited due to their high cost and the time needed (12 hrs) to produce the crystalline materials in the right forms. Manchester Centre researchers have now shown that zeolite crystals can be made by microwaving just for 15 minutes in a giant oven, thus cutting the cost of production and of the final product, that is, lead-free fuel.
Another relatively new arena for environmental research is the University of Manchester Institute of Science and Technology's (umist) Satake Centre for Grain Process Engineering, set up in uk in collaboration with Japan, which focuses on the use of grain to produce industrial chemicals. Starch, which is already being used in pharmaceuticals, paints, plastics and agrochemicals is now being experimented with to be used as a carbohydrate energy source in fermentation processes in biotechnology. Colin Web, director of the Satake Centre, says that in the near future it will be possible to extract industrial products (such as oil and starch) directly from grains.
Web and his colleagues envisage the emergence of a complete processing concept in which wheat, for example, will be used for processing non-food products rather than being blended into higher-value streams. The key to this would be the development of a fermentation medium from which a wide range of fermentation products could be produced by biotechnology. A process has been developed that produces separate glucose-rich and nitrogen-rich streams. Improved fuels and biodegradable plastics are among the products that are likely to emerge from this continuing research.
Another project that aims to conserve resources by substituting a limited natural resource by a waste product has been undertaken at the umist's paper sciences department. The department plans to replace wood pulp with straw as the raw material for paper.
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