Current Trends 

The grease industry is actively pursuing sustainability by exploring and developing eco-friendly alternatives to traditional petroleum-based greases. A significant focus is on utilizing biobased and biodegradable materials, as well as innovative processes that align with environmental sustainability goals. 

One prominent trend is the use of biobased and biodegradable thickeners in grease formulations. Materials such as polyester-based thickeners, lignin nanofibers and cellulose derivatives are being explored as sustainable alternatives to conventional thickeners. These biobased thickeners not only offer excellent performance characteristics but also contribute to the overall sustainability of the grease formulation. For instance, electrospun lignin nanofibers and CAB gels demonstrate superior tribological properties and biodegradability, making them suitable for a wide range of applications. 

Additionally, the incorporation of natural additives and renewable materials is being explored to enhance the performance and sustainability of greases. For example, polysaccharide gums like GA and GG have shown significant improvements in EP performance. The use of biodegradable materials, such as CAB for low-temperature greases, highlights the industry’s commitment to reducing environmental impact. 

Moreover, the adoption of eco-friendly manufacturing processes is being emphasized to further minimize the environmental impact of grease production. Techniques such as waste minimization, the use of renewable energy sources and environmentally friendly production methods are being implemented to minimize the carbon footprint and promote sustainability throughout the grease product lifecycle. 

Despite lubricating greases representing only about 3% of total lubricant volumes, their contribution to global energy savings in tribological systems is significant, accounting for around 16% of the global energy savings. By integrating these practices, the industry is moving toward creating high-performing, environmentally conscious greases that meet the demands of various industrial applications. 

Real-Life Quests for Sustainable Raw Materials

As sustainability penetrates the lubricants and grease industry more every day, formulators are working double time to find viable alternatives to traditional components. Below, we outline some of the real-life work that is being done to craft more sustainable greases. 

Thickeners. By synthesizing biobased and potentially biodegradable greases using polyester-based thickener systems and castor oil as the base oil, Seyedmohammad Vafaei and coauthors explored alternatives to conventional petrochemical lubricants. The developed greases, particularly those with DDS-BD (dodecanedioic acid and 1,4-butanediol) and BS-BD (succinic acid and 1,4-butanediol) thickener systems, demonstrate superior film formation and lower friction coefficients at speeds up to 100 millimeters per second compared to petrochemical urea grease. These biodegradable greases showed comparable tribological characteristics to the petrochemical urea grease, suggesting their potential as sustainable alternatives.

Last year, Maria Borrego and team investigated the tribological performance of electrospun lignin nanofibers as thickeners in castor oil. The study found that homogeneous, bead-free lignin nanofiber mats—particularly those produced with polyvinylpyrrolidone (PVP) as a co-spinning polymer—exhibited superior friction and wear reduction compared to nanostructures with particles or beaded fibers. The best results were achieved with a 10%-30% wt. concentration of lignin nanofibers, where reducing the lignin-to-co-spinning polymer ratio or increasing the polymer solution concentration enhanced the fiber diameter and reduced porosity. This homogeneous network effectively retained and released castor oil under load, maintaining lubrication and minimizing wear. Although friction and wear increased with higher thickener concentrations, the study highlights that well-developed lignin nanofiber networks can serve as cost-effective, renewable thickeners. 

In 2021, Svetlana Gorbacheva and team introduced a novel method for creating biodegradable low-temperature greases using cellulose acetate butyrate (CAB) dissolved in acetyl tributyl citrate (ATBC) that forms a gel upon cooling due to phase separation. The study found that CAB gelation significantly reduces the wear coefficient by tenfold when using ATBC as a lubricant, although it increases the friction coefficient. To enhance the tribological properties, various solid particles were assessed as additives, with polytetrafluoroethylene (PTFE) at a 10% concentration proving most effective in improving the grease’s characteristics. This approach diverges from traditional grease formulations by leveraging the gel properties imparted to the base oil, resulting in greases with superior tribological performance due to the softer, swollen polymer phase. The research highlights the potential of these gel greases to maintain their rheological properties at low temperatures, making them suitable for a wide operating temperature range. The optimal formulation identified includes 10% CAB, which creates stable gel systems with minimal syneresis and enhanced tribological performance. 

Additives. Another study published in volume 200 of Renewable Energy introduced a pioneering approach to enhancing the EP performance of vegetable oil-based greases using polysaccharide gums, gum acacia (GA) and guar gum (GG), as additives. By incorporating GA or GG in concentrations ranging from 0.5% to 10% w/w, Ankit Saxena and team demonstrated a significant improvement in extreme pressure performance, up to approximately 60% better than traditional mineral oil-based greases. 

Figure 1.
(a) Average coefficient of friction and (b) average spot diameter of experimental greases (Mobil SHC 461WT lithium complex grease) mixed with four different additives.

This remarkable enhancement was attributed to the formation of a polymer-layered silicate nanocomposite tribofilm at the interface, facilitated by chemisorption with GA and physisorption with GG. The innovative use of natural, eco-friendly polysaccharide gums offers a sustainable and economical alternative to harmful petroleum-based lubricants, challenging the notion that only synthetic chemicals can achieve high performance in industrial applications. Future studies comparing the performance of GA and GG to traditional EP additives at the same treat rates would provide further support for these findings. 

Han Peng and coauthors addressed the optimization of tribological performance in wind power lubricating grease to reduce carbon emissions and enhance efficiency. The study used a lithium composite grease mixed with four different additives. Results showed that the addition of these additives significantly reduced both the average coefficient of friction and the average diameter of wear spots. In particular, the sample that used molybdenum dialkyl dithiocarbamate additive (461+RFM3000) reduced the friction coefficient by 74% and wear spot diameter by 64%. Additionally, the sample that used polysiloxane viscosity modifier (461+PV611) exhibited the most significant reduction in wear spot diameter, at 69%. 

These findings highlight the potential of both novel and traditional additives to improve the lubrication performance of greases for wind turbines. By reducing friction and wear, these additives can contribute to several sustainability benefits. Lower friction translates to improved efficiency in energy conversion, meaning wind turbines can generate more electricity from the same wind resource. This reduces reliance on fossil fuels and lowers overall carbon emissions. Also, reduced wear extends the lifespan of wind turbine components, minimizing maintenance requirements and the associated environmental impact. 

Future Outlook

The outlook for sustainable grease formulations is promising, driven by the increasing demand for environmentally friendly and high-performing lubricants across various industries. As the world continues to shift toward more sustainable practices, the development and adoption of biobased and biodegradable greases are expected to accelerate. In the coming years, research and development efforts will focus on optimizing the performance and cost-effectiveness of sustainable grease formulations. Advancements in materials science and biotechnology may lead to the discovery of novel biobased materials with superior tribological properties, making them viable alternatives to traditional petroleum-based greases.

Furthermore, the integration of nanotechnology and advanced additives is anticipated to play a crucial role in enhancing the performance and longevity of sustainable greases. The incorporation of nano-additives, such as graphene, molybdenum disulfide and other engineered nanoparticles, could potentially improve properties like load-bearing capacity, anti-wear characteristics and thermal stability. 

As environmental regulations and sustainability initiatives become more stringent, the demand for biodegradable and eco-friendly greases is expected to rise across various sectors, including automotive, industrial, marine and aerospace applications. This will drive further innovation and the development of specialized formulations tailored to meet the unique requirements of different operating environments. 

Moreover, the outlook for sustainable grease formulations is closely tied to the adoption of eco-friendly manufacturing processes and sustainable supply chains. Grease manufacturers will prioritize the implementation of renewable energy sources, waste minimization techniques and environmentally conscious production methods to reduce their carbon footprint and promote a circular economy. 

Overall, the future of sustainable grease formulations holds great potential for innovation, performance enhancement and widespread adoption, driven by the increasing demand for environmentally responsible lubricants and the commitment to achieving a more sustainable future across industries.  

Raj Shah is a director at Koehler Instrument Company in New York, United States, where he has worked for the last 28 years. He is an elected Fellow by his peers at IChemE, CMI, STLE, AIC, NLGI, INSTMC, Institute of Physics, The Energy Institute and The Royal Society of Chemistry. He can be contacted at rshah@koehlerinstrument.com

Angelina Precilla is a part of a thriving internship program at Koehler Instrument Company.