The viability of using gasoline-integrated biodiesel–diesel mixtures in engines as a solution to greenhouse gas emissions: a review


 The implementation of alternative fuels, such as biodiesel, in engines has been shown to be a feasible strategy to control greenhouse gas (GHG) emissions. The blending of biodiesel with diesel can reduce emissions of carbon monoxide (CO) and carbon dioxide and reduce soot formation. Nonetheless, biodiesel combustion comes with low thermal efficiency, elevated emissions of nitrogen oxides (NOx) and carbon deposition issues. Recently, the addition of gasoline to diesel–biodiesel blends has been proposed to compensate for the downsides of biodiesel combustion. In the current review, the viability of using this ternary fuel blend in engines is thoroughly reviewed. The review first assesses the environmental and health issues caused by conventional fuels, mitigation schemes to control GHG emissions and alternative fuels as a decarbonizing technology. The combustion and emissions characteristics of diesel–biodiesel–gasoline mixtures are discussed in detail. Finally, the status, challenges and prospects of applying the alternative fuel mixture in engines are appraised. This work has revealed that the mixing of gasoline with diesel–biodiesel blends brings about elongated ignition delay, increased heat release rate and in-cylinder pressure at high loads. Additionally, by adding gasoline, the combustion duration is shortened and soot, CO and unburned hydrocarbon emissions are suppressed, while NOx emissions are slightly increased. Combustion stability is found to be partially disrupted in the presence of gasoline whereas fuel economy (at medium and high loads) is improved by the addition of gasoline. To support the wider deployment and commercialization of this fuelling strategy in the transportation sector, favourable legislation and/or fiscal incentives are needed in countries around the world. This would encourage researchers, fuel producers and engine manufacturers alike to solve challenges such as biodiesel feedstock costs, fuel quality, fuel storage management and engine warranty issues.