Tribology of green lubricants: Environmental benefits and impacts

Abstract

The depleting fossil fuel reserves induce a hike in petrol prices, and this will remain increasing even after 2045 and will give rise to the prices of petroleum products. Globally, conventional lubricants are used in lubricating industries and transportation to minimize the wear and friction between interacting surfaces. However, these lubricants cause an increase in emission of greenhouse gases, different organic compounds, and environmental pollution. Therefore, sustainable energy sources such as green lubricants are needed in order to overcome such environmental issues, and in this context, vegetable oils emerge as a renewable raw material as these are biodegradable, less toxic, easily available, and their distinctive structure furnishes high flammability and favorable lubrication. Mahua oil has an advantage over vegetable oils as it has polar groups which is an important property in wear reduction, and it is available in surplus amounts therefore utilizing it in making green lubricant will reinforce the rural as well as domestic agricultural economy. The major section of this chapter will discuss the comparative analysis of different lubricants based on their feedstocks, their environmental impact, and the catalysts employed for their production. This chapter also discusses the conversion of mahua oil into diethylene glycol (DEG)-based bio-lubricant by cost-effective route and its environmental impact. This chapter also analyzed the physical properties of the DEG-based bio-lubricant of mahua oil methyl esters and showed that it has density, viscosity index, and acid value of about 0.94 g/ml, 134.14, and 1.13 mg KOH/g and it is safe for aquatic life, and hence it can be applied to the areas where direct contact of the bio-lubricant is expected with water.