Lubes from vegetable oils become affordable
Vegetable-oil-based lubricants are now technologically ready and cost-competitive with petroleum products.
To run trains, cars, and other everyday machines, the U.S. consumed about 2.5 billion gallons of petroleum-based lubricants in 2005. More than a third of that quantity ended up in the environment through various channels—pipe or drum leaks, accidental spills, and people discharging oil into drains.
Lubricants made from vegetable oils, such as soybean, corn, canola, and rapeseed, offer a safer, biodegradable alternative for many applications. Researchers have been working on these bio-based products since the 1980s, but they were initially cast off because they did not work as well as petroleum products or were more expensive. Over the past decade, technological advances have improved the performance of bio-based lubricants, and in the past 5 years, with increasing oil prices and energy security needs, they have become cost-competitive with traditional petroleum lubricants.
“The time has come that we’ll see more rapid growth for these,” says Lou Honary, founder of the University of Northern Iowa’s National Ag-based Lubricants (NABL) Center. He expects the products to be in widespread use “in a window of 2 years.”
In bio-based formulations, vegetable oils replace a mineral oil as the base, which is typically 90% of a lubricant. Fatty acids make vegetable oils naturally more slippery than mineral oils, and their polar molecules make them stick to metal surfaces better, says Fu Zhao, a postdoctoral researcher at the University of Michigan.
But bio-based lubricants also have drawbacks, the most obstinate one being their inclination to oxidize because of their highly reactive carbon–carbon double bonds. Much of the recent technology developments in vegetable-oil-based lubricants have been chemical processes, additives, or genetic modifications that increase their resistance to oxidation.
Like conventional lubricants, bio-based lubricants also need additives to resist hydrolysis, improve corrosion resistance, and inhibit microbial growth, and these add to the product’s cost says Girma Biresaw, a chemist at the U.S. Department of Agriculture’s Agricultural Research Service (ARS).
Cost-competitive bio-based products for select applications are already available on store shelves. Most big lubricant manufacturers, including Shell, Exxon/Mobil, and BP, offer their own bio-based products containing different percentages of vegetable oil, but these companies focus on their petroleum-based products. The Statue of Liberty’s elevators use ARS’s hydraulic lubricant. The NABL’s spin-off company offers products ranging from railway track grease to food-processing-machinery lubricant, and estimates that it has sold about 1 million gallons. For some applications such as railroad grease, Honary says that these products cost less—$1.50 per pound compared with $1.75 per pound for petroleum-based grease. However, they can cost much more for other applications. Hydraulic fluids, for instance, range from $4 to $6 per gallon for petroleum products, while soy versions cost $7–10 per gallon. “People seem to be willing to pay $1 more a gallon if there’s an improvement in the process,” he says.
When Alcoa tested an ARS-developed soybean oil lubricant at its Reno, Nev., aluminum rolling mill, the aluminum company found that the new lubricant worked better than the petroleum product it had been using, says Ronald Reich, a technical consultant at Alcoa. The fluid also cuts costs and volatile organic compound emissions by more than half. The Reno mill has switched to using the bio-based lubricant, and the company plans to test it at other locations, says Reich.
In all, bio-based lubricants garner less than a 5% share of the market, Biresaw says, for two reasons. “First, there are some technical issues that need to be resolved in a cost-competitive way,” he says, such as increasing resistance to microbial growth. The lubricants also remain inadequate for use in cars, aircraft, and heavy machinery.
According to Honary, a key to better-performing yet low-priced bio-based lubricants is creating genetically modified oils that give required properties without the cost of additives or chemical modifications. The NABL already uses modified soybeans composed of more than 80% oleic acid, compared with regular soybeans that have 20%. Oleic acid, a mono-unsaturated fatty acid, has only one double bond between carbon atoms, and this makes it more resistant to oxygen. “Why not have a genetic variety of soybean that could work down to –50 °C? Then you could go into aviation hydraulics,” Honary says.
Government laws leave it up to users to switch to vegetable oils, and some companies, such as Alcoa, have taken the step because of the environmental benefits and reduced emissions. But low costs, which will come with better technologies, will eventually drive the popularity of these products. “The bottom line is the cost,” Reich says. “Today, if the cost was higher, we wouldn’t be putting these [lubricants] in.”
