Biodiesel: An Alternative Fuel for Compression Ignition Engines

Abstract

Biodiesel is an alternative fuel for diesel engines that is produced by chemically combining vegetable oils and animal fats with an alcohol to form alkyl esters. Extensive research and demonstration projects have shown it can be used pure or in blends with conventional diesel fuel in unmodified diesel engines. Interest in biodiesel has been expanding recently due to government incentives and high petroleum prices. This paper reviews the history of biodiesel development, production practices, and the technology to utilize the fuel without problems. A technical consensus has developed that quality is the most important criterion of successful biodiesel use and that fuel should meet the ASTM specification for biodiesel, D6751. When the fuel meets this standard, it has been shown to provide improved lubricity, higher cetane number, lower emissions of particulate, carbon monoxide, unburned hydrocarbons but higher level of oxides of nitrogen. While the current availability of vegetable oil limits the extent to which biodiesel can displace petroleum to a few percent, new oil crops could allow biodiesel to make a major contribution in the future.