KEY CONCEPTS
• Researchers, formulators, ingredient manufacturers and end-users of lubricants are interested in more sustainable lubricants, especially biolubricants and additives for them. 
• Companies are looking especially for additives to biolubricants that will yield better performance and better bio- and oxidative stability, but more research is needed. 
• Demands from the manufacturing sector and government regulations requiring biorenewable finished products will drive additive manufacturers and lubricant manufacturers to put effort into developing and promoting these types of products.

Sustainability, renewable resources and reduced carbon footprints are current market drivers in many fields, and biolubricants can support achieving those goals. Industry needs biolubricants for direct use (e.g., food, marine environments), and there is a constant demand for greener solutions for hydraulic fluids, metalworking fluids and forming fluids, among other industries. Users and manufacturers of these fluids are seeing growing performance demands while facing stricter rules and bans. Examples of potential bans include the European Union’s (EU) CLP (classification, labeling and packaging) Regulation.

Given these concerns, researchers need to take a closer look at alternatives. Biolubricants show promise, but it is unclear how well prior lubricant formulation knowledge translates to this field. A majority of additives are fine tuned for fossil-based stocks. Finding the ideal additive package for water-soluble biolubricants is the next challenge, and understanding the chemical mechanisms of additives in these fluids will be required.

Definitions
Professor Dr. Joachim Schulz, chief scientist forming for ML Lubrication GmbH in Schweinfurt, Germany, notes that definitions of both sustainable lubricants and biolubricants need to be clarified. Schulz observes, “The term ‘bio’ is not protected or well defined.” Many people, even in the lubricants industry, are using these terms inconsistently and, thus, confusing people.

An example is the term environmentally compatible lubricant or biolubricant. Does that mean the liquid is biodegradable, non-toxic, based on vegetable oil or includes only natural ingredients? Schulz offers examples using definitions for the term “bio:”
• Biodegradable and biobased. The material is renewable and readily biodegradable (e.g., vegetable oil).
• Biodegradable. While the material will decompose naturally, it is not necessarily based on renewable raw materials (e.g., di-isotridecyladipate).
• Biobased. The material is renewable but not necessarily biodegradable (e.g., hydrocarbons from a biomass-to-liquid [BTL] process).
• Biocompatible. The material is neither renewable nor biodegradable (e.g., white oil for food-compatible lubricants).

Sustainable is another term that is often used in confusing ways. Schulz notes that the Brundtland Report of the World Commission on Environment and Development: Our Common Future has defined sustainable development as:

“Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” ¹

However, this still leaves questions as to the meaning of “sustainable” in commercial and marketing terms. Schulz questions whether it means only the use of renewable materials in the pure form, or if processed renewable materials also could be under this term. Also, Schulz questions whether biodegradable or renewable can play a role in sustainability if the materials are fully recycled.

Biolubricants
Schulz states, currently, “About 70% of lubricants are based on mineral oil, with 350,000 tons worldwide in 2019, with less than 1% of the total lubricant market being biolubricants.” The biomaterials employed were various vegetable oils or animal fats. Schulz identifies the raw materials as “rapeseed, palm, sunflower, castor and soybean oil, as well as beef tallow, among other sources.” The vegetable oils can either be used in their native form or converted into synthetic esters by chemical processes as needed for specific applications.

Additives
Jeffrey Yost, CEO and founder of BioRenewable Solutions, LLC in Atlanta, Ga., notes, “Using biobased additives is nothing new,” as they have been around for decades. Examples include “biobased additives like esters and alkanolamines, as well as oxidized (blown) oils, all comprised of canola, castor, distilled tall oil (DTO), high erucic acid rapeseed, oleic, tall oil fatty acid (TOFA), soy, etc.” 

Schulz notes that additives are used in lubricants for a number of reasons, including:
• Enhancement of existing base oil properties (e.g., wear protection, lubricity, corrosion protection)
• Generating new properties (e.g., cleaning, emulsifiability)
• Influencing physical/chemical properties of the respective base fluids (i.e., viscosity index, pumpability, foaming tendency, oxidation stability, high pressure load carrying capacity, etc.).

The type of additives that are essential for lubricants in general, and for biolubricants in particular, depends on the lubricants’ application. Schulz notes that for metalworking fluids, a specific lubricant product, a relatively high content of antiwear (AW) and extreme pressure (EP) additives are needed. As the lubricating properties of biolubricants tend to be better than of oil-based lubricants, they require fewer additives to support lubricating properties. However, Schulz says, “Biolubricants show a stronger tendency to oxidation and hydrolysis and, thus, require a higher demand for additives to improve durability/stability.”

Obstacles to finding the right additive package Yost sees the biggest challenge in using anything biobased being the materials’ inherent instability, as well as the poor oxidative stability. However, “the current push to become carbon neutral is a catalyst for innovation to create superior bioadditives and biolubricants that will be based upon sustainable, no-food grade product streams.”

Schulz notes a rule of thumb for finding the right additive package for biolubricants: “like dissolves like,” which “means that an additive dissolves best in a solvent (i.e., base fluid) that has a similar polarity.” While this is a very simplified approach that ignores certain additional interactions, it is still useful. Additives such as viscosity index improvers (VII), pour point depressants (PPD) and antioxidants (AO) are typically relatively non-polar, making them readily soluble in non-polar base oils. In contrast, all surface-active additives, such as metal deactivators (MD), corrosion inhibitors (CI) and EP/AW additives, are polar; therefore, their solubility in non-polar base fluids (i.e., polyalphaolefins [PAOs]) must always be confirmed.

Schulz notes that additives interact by absorption with metal surfaces, which means the additives need a polarity. In other words, polar additives compete for the metal surface. Base oils for biolubricants also are polar, meaning they are in competition with the other additives. As the metal surfaces have a finite size, the number of additives that can come into direct contact with the metal surface is limited. Too much additive limits the product’s effectiveness as polar substances can push each other out, resulting in suboptimal coverage. The additive industry has mostly focused on developing additives for mineral oil-based lubricants, which Schulz says means the industry needs to rethink approaches with biolubricants.

Yost notes that while the major obstacles to using biolubricants in the past have been bio- and oxidative stability, a few additive companies are looking at these issues. However, more research and in- novation are needed. Yost says, currently, “The choices for biobased EP additives are limited to nonexistent.” Another obstacle Yost mentions for biolubricants is their price compared to prices for petroleum-based lubricants. When crude oil is relatively cheap (e.g., $60 per barrel), innovation is discouraged, especially when incentives are lacking.

STLE member Cathy Novak, managing director of Novak Services, LLC in Detroit, Mich., sees the major obstacles regarding the use of biolubricants to be “compatibility with existing additives, couplers and emulsifiers.” Long-term, Novak notes that demand from customers could be an issue unless customers are “willing to consider alternatives to the existing lubricant chemistries.” Without market willingness to consider alternatives, “there is no incentive for the small compounder blender to develop new products.” Novak sees specific challenges regarding the composition of biolubricants to include oxidation, boundary lubrication and EP.

Regulations
Yost notes that the EU is offering higher governmental incentives and penalties, coupled with specific timeline benchmarks based on the EU Renewable Energy Directive II (RED II). Under the RED II, the EU’s overall target for renewable energy sources consumption by 2030 has been raised to 32%.² Yost says, “The EU is mandating to reach carbon neutrality by 2050.” In contrast, the U.S. is just beginning to implement change.

Demand
Yost says, “Currently there are increasing demands for biofuels from nonedible feedstocks like soy, rapeseed, crude tall oil (CTO), TOFA, palm, etc.” In the EU, new biorefineries are emerging in the Nordic countries, with outputs as high as 500,000 metric tons per year. Yost says, “This is impacting the availability and pricing for various biobased lubricants.” Yost provides the example of “the pricing for various pine-based products has increased every quarter over the last two years.” The pressure to produce more biolubricants will continue to increase.



Fields with the most biolubricant potential
Schulz says, “Vegetable oils are used in their native form or they are converted into synthetic esters by chemical processes and, thus, modified for the respective application for chainsaw oils, hydraulic oils, marine oils, concrete release/mold release/formwork oils and wire rope lubricants.” He sees loss lubrication as having potential for biolubricants.

Beyond those industries, Schulz says, “Biolubricants also can and should be used in other applications in the lubricants industry.” The reduced CO₂ footprint and the higher power density of biolubricants compared to mineral oil explains the value of biolubricants. Beyond that, Schulz notes that recycling needs to be clarified. He says, “All lubricants that are used in a system should have the same raw material base and be fully compatible with each other,” which would greatly simplify recycling. In addition, the additives industry needs to develop biocompatible additives.

Yost sees the most potential for biolubricants in machining and grinding (M&G) “primarily using biobased base oils, which would consist of the major portion of the additive package, coupled with amines and esters, which also are biobased.” In addition, Yost says, “The automotive industry is making dramatic changes toward electric vehicles (EV) to help reduce greenhouse gases, and part of their manufacturing process should involve biobased lubricants.”

Market share
While the current market share for biolubricants is low, Yost foresees “a dramatic spike in demand for unique, sustainable biobased lubricants that will be used to help reduce many manufacturers’ carbon footprints” in the next five years. He also expects the EU to lead in these markets.

The current focus on biobased products also will help advance biolubricants. Yost reports, “The EU is on the cutting edge, so their demands will be higher.” To be a global player in the biolubricant field, Yost says, “U.S.-based companies will have to create new biobased lubricants and additives.”

In agreement with Schulz regarding confusing terms, Yost asks, “When does green become green?” He continues: “The global lubricant industry needs standardization regarding the classification of biolubricants and additives, coupled with the documented history of each product’s origin and sustainability.” This standardization will clarify when only a small percentage of a material is biobased yet marketed as ‘green.’ While using biobased materials “is a start toward more innovative products, one must consider the total cradle-to-grave carbon footprint that is generated.” Yost points out the fuel used to transport biobased raw materials adds to the carbon footprint of the resulting product.

Novak “can already see biolubricants being used in just about all regimes of lubrication, that is motor oils, marine lubricants as well as metalworking lubricants and greases.” Novak says, “As more and more manufacturing companies begin to reduce their carbon footprint and the demand for sustainable lubricants in the manufacturing sector grows, the small compounder blenders will be challenged to add a parallel product line to their existing, hydrocarbon-based, portfolios.”

EALs
Another area where Novak sees opportunities is in environmentally acceptable lubricants (EALs). The U.S. EPA acted on Dec. 19, 2013, to minimize the adverse impact of lubricant discharges on the aquatic environment through its updated “Vessel General Permit for Discharges Incidental to the Normal Operation of Vessels” (VGP).³ Under a VGP, commercial vessels greater than 79 feet in length have authorization to discharge under the National Pollutant Discharge Elimination System (NPDES) under the Clean Water Act. Vessels constructed after that date must use EALs in all oil-to-sea interface applications. Vessels constructed prior to that date will have to replace mineral oil or other lubricants with EALs in all oil-to-sea interfaces unless that is shown to be technically infeasible.

The Vessel Incidental Discharge Act (VIDA) was signed into law in 2018.⁴ Under VIDA, EPA is required to develop new national standards of performance for commercial vessel incidental discharges, and the U.S. Coast Guard is required to develop corresponding regulations.⁵

Looking ahead
Schulz believes that a general rethinking of industry and society is necessary. He says that if society continues to aim for “higher, faster, further and only thinks about maximizing profits, this runs counter to the goals that are set for a sustainable economy.”

Yost observes: “Innovation is driven by many incentives, ranging from internal goals the individual companies set for themselves, to governmental regulations coupled with tax incentives/penalties.” The current research environment for biobased products is a new world.

Novak notes: “The end-user drives this initiative.” In other words, what the end-user “wants/demands is what the additive suppliers will put effort into.” The manufacturing sector and government demands for biorenewable finished products will drive lubricant and additive manufacturers to put effort into developing and promoting these types of products.

REFERENCES
1. Brundtland G. (1987), Brundtland Report of the World Commission on Environment and Development: Our Common Future. United Nations General Assembly document A/42/427.
2. European Commission website. “Renewable Energy – Recast to 2030 (RED II).” Available here.
3. EPA (March 8, 2022), “Vessels – VGP.” Available here.
4. EPA (Jan. 4, 2022), “The Vessel Incidental Discharge Act (VIDA).” Available here.
5. Kovanda, J. (July, 2015), “VGP Compliance: How the Latest EPA Marine Lubricant Requirements Affect You.” Available here.

Andrea R. Aikin is a freelance science writer and editor based in the Denver area. You can contact her at pivoaiki@sprynet.com.