B. B. Ghosh and Ahindra Nag

7.1 Introduction

The increasing industrialization and motorization of the world has led to a steep rise in the demand of petroleum products. Petroleum-based fuels are stored fuels in the earth. There are limited reserves of these stored fuels, and they are irreplaceable. Figure 7.1 shows the difference in demand and supply of petroleum products, and how this depletion will create a problem before the world within a decade or two.

Geologists throughout the world have been searching for further deposits. Although the present reserves seem vast, the accelerating con­sumption is challenging the world to create new types of fuels to replace the conventional ones. New oil reserves appear to grow arithmetically while consumption is growing geometrically. Under this situation, when consumption overtakes discovery, the world will be heading toward an industrial disaster.

Apart from the problems of fast-vanishing reserves and the irre­placeable nature of petroleum fuels, another important aspect of their use is the extent and nature of environmental pollution caused by com­bustion in vehicular engines. Petroleum-fueled vehicles discharge sig­nificant amounts of pollutants like CO, HC, NOx, soot, lead compounds, and aldehydes.

A light-vehicular engine (car engine) discharges 1-2 kg of pollutants a day, and a heavy automobile discharges 660 kg of CO a year. CO is highly toxic, and exposure for a couple of hours to concentrations of 30 ppm can cause measurable impairments to physiological functions.

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Figure 7.1 Difference in demand and supply of petroleum products.

Oxides of nitrogen and unburned hydrocarbons from exhausts cause environmental fouling by forming photochemical smog. Their interac­tion involves the formation of certain formaldehydes, peroxides, and peroxyacylnitrate, which cause eye and skin irritation, plant damage, and reduced visibility. Present day leaded gasoline contains lead com­pounds. Lead coming out with the exhaust finds its way into the human body, and causes brain damage in infants and children.

Vehicular exhaust fouling of the environment has already become a serious problem in Western countries and is a growing menace in devel­oping countries like India [1]. They exhaust huge quantities of harmful pollutants in urban areas. Everyday, vehicles running in Delhi dis­charge about 240 tons of CO, 30 tons of HC, 20 tons of NOx, and 2 tons of SO2. The disastrous effect of these pollutants on human health, animal and plant life, and property are well known.

In view of these problems, attempts must be made to develop tech­nology to produce alternative, clean-burning synthetic fuels. These fuels should be renewable, should perform well in the engine, and their poten­tial for environmental pollution should be quite low.

Various fuels have been considered as substitutes for petroleum fuels used in automobiles. The most prominent of these include ethanol, methanol, NH3, H2, and natural gases [2]. The suitability of each of these fuels for internal combustion (IC) engines used in automobiles has been under investigation throughout the world. A few of them are already in use in different countries. This chapter introduces different types of uncon­ventional fuel such as ethanol and methanol, their burning properties when used in IC engines, their performance characteristics compared
with conventional engines, the modifications required in the engine if used in practice, and their environmental pollution characteristics.