Current status and prospects of alternate liquid transportation fuels in compression ignition engines: A critical review

Many research projects have been undertaken by the researchers to address the global energy crisis, fossil fuel depletion, over-reliance on crude oil, improvement of performance and emission, and waste management issues, with promising and remarkable results. Exploration of alternate fuels is one of such outcomes. Alternative fuels are preferred because they are renewable in nature. They are also environmental friendly in use and cost-effective in production. They are attractive from waste management perspective. These fuels are intended to provide improved performance and lower emissions. They do not impact engine functionality. To maintain a balance between fuel production and consumption, countries must explore alternative sources. They can provide the best possible outcomes to resolve the energy security and environmental crises. This paper highlights the use of several alternative fuels as a diesel replacement in compression ignition engines, with a focus on plastic oil, which has recently received a lot of interest from researchers. It summarises the source, general properties, benefits, and demerits of five different diesel fuel substitutes: bioalcohols, biodiesel, green diesel, bio-oil, and plastic oil, with wide literature support. The major contribution of the review includes the extensive description of the research outcomes on the utilization of plastic oil in diesel engines undertaken by different investigators, along with some potential future scope for the improvement of the performance of the oil, which would give a direction to the prospective researchers.