The Best of Both Worlds
The lubricants industry is constantly looking for viable replacements for traditional mineral oil-based lubricants. In recent years, biodegradable soybean oil has become a key ingredient in many lubricants used in industrial and other applications as concerns about environmental safety, climate change and sustainability grow.
Proponents of soybean oils say that the oils can increase the environmental friendliness of driving activities, since they can be used in a variety of applications. These applications include asphalt used for road construction, rubber used to make all-weather tires and—most important to the lubricants industry—base stocks used to formulate motor oils.
The United States alone can cultivate 89 million acres of soybeans annually, and roughly 4 million metric tons of soybean oil is directed to industrial uses, according to the United Soybean Board’s Market View Database.
“Soybean oil has proved a versatile material that can perform well at both high and low temperatures, making it a business and customer favorite in durability,” said John Jansen, vice president of the United Soybean Board.
The United Soybean Board is a group of soybean farmers that researches and promotes soy products. It consists of 73 volunteer farmer-directors who oversee the investments of the soybean checkoff—a congressionally mandated assessment on soybeans.
High oleic soybean oil can be used as a base stock in several different applications, one of which is biodegradable synthetic motor oil. Indianapolis-based Biosynthetic Technologies is a major marketer of such products, with its focus on producing engine oils and industrial lubricants from technology originally developed by Terry Isbell and Steven Cermak with the U.S. Department of Agriculture.
Working with soybeans that generate high levels of a fatty acid known as oleic acid, Isbell and Cermak devised an approach for coupling these oleic acid molecules to produce long-chain molecules known as estolides.
“Soy-derived estolides have chemical properties that naturally make them very slippery, with a branched structure that also prevents them from gelling together,” Isbell said. “So now you can maintain it as a liquid at much colder temperatures.”
Biosynthetic Technologies boasts the performance capabilities of its soy-based engine oil, which was successfully tested in a fleet of Las Vegas taxicabs “in the baking daytime heat and deep nighttime chill of the Nevada desert from 2012 to 2014.” But the company also touts the oil’s low environmental impact.
“Plant-based oils offer a much safer alternative,” Mark Miller, chief operating officer of Biosynthetic Technologies, told Lubes’n’Greases. “If it gets into the environment, it readily biodegrades. If a river or sea fish eats it, it’s nontoxic.”
Biosynthetic Technologies has also made a case for the overall soybean oil manufacturing process—including the growing process—which achieves much greater net sustainability. For instance, the company noted that more than eight metric tons of carbon dioxide are absorbed by the plants for every ton of oil generated from them.
As “demand for soy products grows, the increased acreage of this crop will result in improved carbon capture and reduced greenhouse gas emissions,” Jansen said. This is “a double win for product users and for efforts to slow and prevent climate change.”
As for performance, soybean oils are becoming increasingly competitive with mineral oils. “Soybean oil-derived estolides are a versatile material,” Miller said. “Anywhere petroleum is used, I see these products being used instead.”
Motor oil operates in especially rigorous conditions. It must allow engines to run smoothly in both subzero and boiling hot operating temperatures; car and truck engines typically generate temperatures around 100°C.
Further, contemporary motor oils are expected to deliver stable performance for up to 10,000 miles. This expectation poses a challenge for biologically derived lubricants, though. Some often begin to break down when they encounter water, or they degrade at high temperatures because of increased oxidation.
Fortunately, estolides from high-oleic soybean oil can withstand this level of abuse. “Without much effort, we could get an oxidative stability that would perform at the same level as current engine oils,” Isbell confirmed.
Biosynthetic Technologies exclusively sources soy with fatty acid content that is at least 70% oleic acid. These strains provide a more concentrated source of raw material as feedstock, supporting subsequent chemical modifications. By tweaking its proprietary estolide synthesis process, the company said it can modulate the viscosity of the resulting oil.
The process yields products optimized for different operating conditions and performance requirements. Some of the company’s formulations maintain the desired viscosity, even at temperatures as low as minus 50°C. Up to 90% of the resulting motor oil is biodegradable.
In Biosynthetic Technologies’ Las Vegas field tests, soy-derived engine oil was put to the test in a head-to-head comparison against a conventional petroleum-based motor oil. Over the course of the two-year demonstration, each cab in the two fleets traveled 150,000 miles with their respective oil formulations, with oil changes every 7,500 to 10,000 miles. The company’s engineers observed reduced friction and wear in the engines that received the soy-based oil, which could contribute to greater fuel efficiency.
Biosynthetic Technologies’ oil then passed the American Petroleum Institute’s rigorous testing requirements, leaving less engine residue than traditional oils.
The company is now developing industrial lubricants and metalworking fluids. It has previously developed hydraulic oils.
“We are getting incredible performance in terms of sustainability, biodegradability and oxidation stability,” Miller said. “We are able to have oxidative stability equivalent to that of petroleum oils.”
Boris Kamchev is a staff writer with Lubes’n’Greases. Contact him at Boris@LubesnGreases.com