Base Stocks

Biobased Grows, as do Hurdles


Vegetable based lubricants and greases are only a small part of todays lubricant arsenal, but technological, economic and regulatory trends may at last be aligning in their favor, says Lou A.T. Honary, director of the National Ag-Based Lubricants Center at the University of Northern Iowa.

In a keynote address to the National Lubricating Grease Institutes annual meeting, the Waverly, Iowa, based professor pointed out that biobased lubricants are of strong interest in Midwest states with large agricultural bases.

Researchers are using several approaches to improve seed oils durability, even as biobased market opportunities are growing. On the minus side of the ledger, some big end-use segments – such as engine oils – remain out of reach, prices are not always competitive, and seed oils face a battery of misconceptions, Honary acknowledged. He also provided a glimpse of a promising concept for grease manufacturing – using energy-saving microwaves instead of traditional kettles.

Sources of biobased oils for lubricants include soy-beans, which have global production of 6.5 billion gallons per year, Honary said. Palm oils, the second-largest source, accounts for 4.8 billion annual gallons, and canola (called rapeseed in Europe) accounts for 2.8 billion gallons. Other vegetable oils – such as corn, sunflower and coconut – have also been tried as lubricant base oils, but soy and canola are the leading types so far, the gathering in Tucson, Ariz., heard in June.

Industrial applications for seed oils are not new, but of late there has been negative publicity that they compete for space to grow what otherwise would be food crops. Last year when food prices went up, we saw the issue of food-versus-fuel, Honary said, with biodiesel vilified in particular. It was blamed for starving people, for the destruction of the Amazon, and so on.

One solution to this conflict would be to use non-food oil seeds for lubricants, because these do not take agricultural lands out of food cultivation. Perhaps soy is just a stop-gap until these alternative oils are developed, Honary suggested. Eventually we could have nonfood oils grown in the desert.

He hopes the controversy can be resolved soon though, because vegetable oils have many advantages as lubricants. They are naturally a better lubricant, and have a better natural viscosity index at 220, versus only 95 for mineral base oils. They also can have better extreme-pressure performance, and offer good film strength. Their volatility properties are also good.

Still, not all vegetable oils are created equal, and most require genetic or chemical alteration to improve their performance. If untreated, vegetable oils lack oxidative stability. And also if untreated, they have higher pour points than mineral base oils. (Pour point is the lowest temperature at which a base oil will flow; the lower the better, generally.)

Also, biobased oils generally have been more expensive than petroleum, although now many biobased oils are about $1 per pound lower in cost than some competitive products, Honary added. The other big drawback is they are relatively unknown to industry. People and users dont know and are uncertain about them; they dont want to try them.

Honary began working on biobased lubricants in 1991, with a project focused on creating soy based hydraulic oils. Immediately, it became clear that oxidation stability was going to be a performance issue; researchers at UNI spent four years trying to overcome conventional soy oils oxidation limitations but had little luck in pushing its ability to withstand heat and oxygen.

For soy, 150 degrees C appears to be the magic number. When you get past that temperature, the oil begins to deteriorate rapidly, he said.

Things changed, he continued, around 1995 when researchers at Dupont developed a high oleic content soybean variety which solved some of the oxidation issues. Fortunately for lubricant suppliers, this strain lately has caught the attention of the food industry in its search to find a frying oil that doesnt need hydrogenation (a process which is linked to unhealthy transfats). This means the high oleic soybeans are much more widely available now, he said, with large volumes now being planted in Iowa and Canada.

Beyond genetically enhancing oils to develop high oleic varieties, researchers are also trying other avenues, Honary related. These include plant breeding techniques, chemically modifying the oils, and using biodegradable additives which are more available now.

Testing of vegetable base oils shows that high oleic (versus conventional) soy gave good performance in an extended-life ASTM D2271 hydraulic pump test (see page 18), run for a punishing 1,000 hours at 79 C, Honary told the NLGI meeting. Both mineral and vegetable based hydraulic oils were run in this industry-accepted wear-protection test.

The petroleum based hydraulic oil saw a viscosity gain of 1.5 percent in the test, Honary said, while a standard rapeseed (canola) based version changed 37.2 percent. A genetically modified canola did much better, shifting only 2.93 percent in viscosity, and a soy based formulation saw a 4.6 percent change. Most impressively, a 50/50 blend of soy and mineral oil actually gave excellent results, with only a 1.6 percent change in viscosity over the test duration. That was statistically in the same league as pure mineral oil based hydraulic oil. It also suggests that blending some types of vegetable and petroleum oils – once considered folly – can be done successfully.

One lubricant product is still out of reach for vegetable oils, Honary conceded: The holy grail is engine oil. But even that prospect is looking brighter. Estolides developed at the National Center for Agricultural Utilization Research in Peoria are showing very good RBOT [rotary bomb oxidation test] values, as well as pour points low as -40 F in some cases, he said. This at least may help deliver the low-temperature pumpability performance that engine oils demand.

Separately, the Association for the Advancement of Industrial Crops ( has taken a different approach. This group has been researching rugged plants that can be grown on relatively arid land, including castor, lesquerella, cuphea, jatropha, camelina and others. The benefit is that these broadcast crops dont compete with food, said Honary. And the oil yield can be very high. Camelina, for example, can yield 39 percent oil – more than twice the crush from soybeans, and all nonedible. Such industry-bound crops might be grown untended on undesirable land, then harvested using conventional combines and tillers, Honary suggested.

Looking at current products and applications, he observed that UNI-NABL has created more than 30 lubricant products, including hydraulic oils, chain bar oils, transformer coolant and greases. Its first commercial success was a railroad grease to reduce wheel-flange friction against the rails. More than 10 million pounds of rail grease are used every year in the United States, largely applied by wayside lubricators at rail curves, which means all the spent grease goes into the ground at these concentrated locations. At least with a biodegradable grease, this environmental impact is reduced, Honary said.

He believes theres even greater potential to use rail flange lubricants on straight sections of track. We have documented the fuel savings using tribometers and monitoring. It appears that you can get about a 10 percent reduction in diesel fuel consumption if you grease the entire track – which you can do if the grease is biodegradable and safe for the environment.

Honary also described some newer greasemaking processes, such as using preformed, dehydrated soap as the thickener system, or a preformed oily soap that thickens base oil under vigorous shearing. Polymer thickeners are also being used, he said.

Lately, NABL has tried another fresh approach: using microwaves to cook vegetable oil based grease. This is an intriguing alternative to using open or closed kettles, which typically rely on dangerous heat-transfer fluids, and is a line of work that rose from the smoking ruins of Environmental Lubricants Manufacturing. ELM, an Iowa lube company founded to bring the universitys vegetable lube products to market, burned to the ground two years ago. The cause of the fire was a heat-transfer fluid used in the grease plant – and it sent Honary on a quest to find a safer way to cook grease.

Speeding grease reaction times with microwaves was originally tried in the 1960, he found, but the equipment then was too expensive and the effort abandoned. In current research, Honary is finding microwaves appear ideal for making vegetable based greases; the reaction time and energy requirements are greatly reduced from conventional kettle cooking methods. Mineral oils dont seem to do as well in microwaves though, Honary said, because they dont seem to absorb energy the same way as polar vegetable oils do. With vegetable oils, we see the temperature rise at the same rate at every point in the vessel which ensures a consistent reaction. Whats more, commercial microwave technology has advanced greatly over the past 40 years, and the equipment is no longer exotic or prohibitive.

In closing, Honary reminded listeners that there are regulations in place now to promote the purchase and use of biobased, renewable lubricants by the U.S. government, making it the largest potential customer for these products. The federal policy is leadership by example, not by mandates, and this will encourage others to try vegetable based lubricants too. The U.S. Department of Agriculture maintains a list of approved biobased products which are to be given preference in all federal purchases, and they include many lubricants. The entire list of BioPreferred products can be seen at