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Currently, the chemical composition of most lubricant additives is based on synthetic esters that can be harmful to the environment and expensive to produce. A tremendous amount of research over the past few years within the lubricant industry has looked into how environmentally-benign lubricant additives can assist in reducing the environmental impact of this industry. The shift towards replacing petroleum-based lubricants with eco-friendly lubricants has also supported the need to develop biodegradable lubricant additives.
The Function of Lubricant Additives
Lubricant additives, which can originate from either organic or inorganic sources, are dissolved or suspended as solids within oil. In fact, lubricant additives can ultimately comprise up to 30% of the total oil volume. The incorporation of an additive into a lubricant solution can serve to improve an existing base oil property, reduce the presence of an undesirable base oil property or incorporate novel properties into the lubricant.
For example, the addition of antioxidants and corrosion inhibitors, as well as extreme-pressure, anti-foam or demulsifying agents can be used to enhance current base oil properties. Additionally, the incorporation of extreme pressure (EP) additives, detergents, metal deactivators, tackiness, and anti-wear (AW) agents typically function to introduce new properties into the base oil.
Advantages and Disadvantages of Green Lubricants
Conventional lubricants, such as those which are petroleum-based, are well known for their ability to exert toxic effects on the environment. For example, the use of these types of lubricants has been associated with promoting air pollution by causing an excess production of greenhouse gas emissions into the atmosphere. As the global interest in preserving the environment continues to rise, the development of environmentally friendly lubricants that are not associated with causing these types of effects are well sought-after.
The replacement of petroleum-based lubricants with bio-lubricants has been shown to enhance lubricity, increase viscosity, equipment service life and load-carrying ability, as well as reduce evaporation rates. In an effort to improve the biodegradability and renewability of lubricants without compromising their tribological properties, various environmentally friendly lubricants have been developed, some of which include:
- Soybean oil
- Sunflower oil
- Jojoba oil
- Natural garlic oil
- Castor oil
While these lubricant alternatives exhibit noteworthy properties, there remains a considerable amount of room for improvement. This is especially true when these lubricants are being used as cutting fluids, or automotive, marine, pre-coat, metalworking, and gear oils. Bio-lubricants are also limited in their poor oxidative and hydrolytic stability, high-pressure sensitivity, poor cold flow properties, higher cost and potential for gumming effects to arise during their use. Researchers have therefore manufactured chemically or genetically modified vegetable oils that are better suited for lubricant applications; however, the widespread use of these lubricants is restricted due to the inability of these manufacturing processes to quickly meet bulk demands.
The Benefit of Green Lubricant Additives
Since petroleum-based lubricants continue to dominate the lubricant market, the incorporation of green lubricant additives into these solutions can still improve the environmental impact of applied lubricants. In addition, vegetable oil-based additives can also increase the lifetime of engines through enhancing multifunctional performances in lubricants. For example, several research studies have demonstrated that vegetable-oil additives, such as those derived from soybean and castor oil, significantly improve the viscosity index, thermo-oxidative stability, anti-wear and pour point properties of base oils.
Renewable LubricantsTM, which is a leading developer and manufacturer of high-performance biologically-based lubricants, has developed numerous green lubricant additives that have been shown to improve lubricant performance and extend the lifetime of high-performance machines. When incorporated into gas and diesel fuels, Renewable Lubricants’s additives have been shown to elicit clean and efficient combustion in fuel injected engines, all the while improving fuel economy, power, ignitability, and combustion.
Sources and Further Reading
- “Lubricant Additives – A Practical Guide” – Machinery Lubrication
- Nassar, A. M., Ahmed, N. S., & Nasser, R. M. (2015). Green lubricating oil additives. Pelagia Research Library 6(3); 100-107.
- Karmakar, G., & Ghosh, P. (2015). Soybean Oil as a Biocompatible Multifunctional Additive for Lubricating Oil. ACS Sustainable Chemistry & Engineering 3(1); 19-25. DOI: 10.1021/sc500685r.
- “Bio-Additives” – Renewable LubricantsTM
- “Gas and Diesel Fuel Additives” – Renewable LubricantsTM
- Singh, Y., Farooq, A., Raza, A., Mahmood, M. A., & Jain S. (2017). Sustainability of a non-edible vegetable oil based bio-lubricant for automotive applications: A review. Process Safety and Environmental Protection 111; 701-713. DOIL 10.1016/j.psep.2017.08.041.