Is hydrotreated vegetable oil a superior substitute for fossil diesel? A comprehensive review on physicochemical properties, engine performance and emissions

Abstract

To achieve carbon neutrality in the near future, there is a need for a solution to sustainable mobility with a high technology readiness level. One option is to use biofuels in existing vehicles powered by internal combustion engines. This review aims to present the competitive edge of hydrotreated vegetable oil (the second generation biosourced fuel used in compression ignition engines) over fatty acid methyl ester (the first generation counterpart) and fossil diesel. Emphasis is placed on the comparison between neat hydrotreated vegetable oil and fossil diesel. Recent works on hydrotreated vegetable oil are covered, ranging from the explorations of spray-combustion characteristics with various forms of combustion chambers to the analysis of the performance and emissions of compression ignition engines. Structural presentation is adopted rather than just stacking data found in various publications to help readers conceptualize the performance and emissions of hydrotreated vegetable oil used as a fuel in compression ignition engines as well as its fundamental chemical and physical properties. The discussion of works involving engines is divided into two sections for engines with pump-line-nozzle injection and modern injection technologies because of the vast differences in combustion environment and the trends of experimental results. Also, the production and lubricity issue of hydrotreated vegetable oil are briefly discussed.