A review of recent advances in the synthesis of environmentally friendly, sustainable, and nontoxic bio-lubricants: Recommendations for the future implementations

Conventional petroleum-based lubricant resources are depleting rapidly, and their utilization severely threatens the environment. Environmental sustainability emphasizes the need for an alternative to petroleum resources. The lubricants play a significant role in machinery’s adequate energy-saving performance. Therefore, the tribological aspects of machinery’s maximum efficiency should be considered. The current study reviews the part of bio-lubricants towards environmental sustainability. This review has been conducted according to the PRISMA approach, where the sources of bio-lubricants, tribological performance, the role of additives and nanoparticles, benefits and disadvantages, production techniques, economic aspects, and future scope were explored and discussed. Bio-lubricants possess a better viscosity index, lubricity, biodegradability, and non-toxic and renewable nature than petroleum lubricants. However, lower thermo-oxidative stability and higher pour points due to moisture content require further improvements. Food security is another significant concern for bio-lubricants. Consequently, it emphasized the importance of algae-based bio-lubricant sources in reducing the threat to food security, water purification, and greenhouse gas mitigation. Further improvements and optimization of production methods are required to increase lubricant yield rates and promote sustainability. The importance of new (algae-based) bio lubricant substitutes with details of their physicochemical properties for a sustainable future is highlighted in this review research.