Chapter 19 - An overview of current trends and future scope for vegetable oil–based sustainable alternative fuels for compression ignition engines

Abstract

The elevated demand and limited sources of fossil fuels, along with the increasing levels of pollution, have generated intense interest in the development of renewable and cleaner sources of energy. A number of alternative-energy technologies are emerging worldwide, but most of these are still in the early stages of development and are uneconomical, and therefore unable to replace fossil fuels. One such renewable source of energy is “vegetable oils,” which are carbon-neutral and with a life cycle of a few years, in contrast to fossil fuels with a life cycle of millions of years. The aim of this technology is to replace diesel with vegetable oils in compression ignition engines, which are used for mass transportation. The vegetable oils, however, cannot be used directly in the engine due to various short-term and long-term effects, such as coking at the injector tip and the formation of carbon deposits. The vegetable oils are therefore processed before use, mainly to reduce the viscosity. Common methods of treatment include transesterification, hydrotreatment, blending, and emulsification, where the final products are biodiesel, hydrotreated vegetable oil, or green diesel, blends, and emulsions and microemulsions, respectively. These methods improve the combustion characteristics and also reduce the emissions. However, there are some limitations as well, and thus further work needs to be done to develop economical and environmentally friendly technologies on a commercial scale.