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A Review of Developments in the Acid Hydrolysis of Cellulosic Wastes

The acid hydrolysis of cellulosic wastes has attracted the attention of many research workers around the world, especially in the last decade. This high temperature and pressure process results in the production of sugars which may be fermented to ethanol. By virtue of their cellulosic content, agricultural, industrial and municipal solid wastes may all be processed by acid hydrolysis with an end result of waste disposal and recycling/recovery of important energy sources. The complete process of the conversion of a cellulosic waste through to the end product and by-product utilization has to give due consideration to likely technologies. Some essential problems that have to be tackled are raw material storage, availability and preparation, the optimum acid hydrolysis and fermentation conditions and product separation methods. This paper is a review of the research that is taking place not only in the field of acid hydrolysis but also in the types of waste used, the concentration of the product sugars, the optimization of the fermentation conditions and the use of low-energy alcohol recovery methods to replace conventional distillation. Most research is at bench scale level with some pilot plants being reported. Also included is the authors' current work using a continuous reactor for the hydrolysis of newsprint.