Replacing Toxic Lubricants in Farming

Modern farmers use many different machines to help seed their fields. 

But inside all of those machines, you’ll likely find one of only two commercially available solid lubricants — talc or microplastics — which keep the seeds from clumping and clogging the spreader. And one thing talc and microplastics share in common is that both materials can pose risks to human health and the environment. 

“Lubricants are essential to modern farming, but existing approaches are contributing to toxicity in our farmlands that affect farmer health, soil health and pollinators that are essential to our food supply,” says Dhanush Udayashankara Jamadgni, a Ph.D. student at NC State University.

Thanks to recently published research, though, farmers might one day be able to opt for the first-ever nontoxic solid lubricant. 

“There is a growing body of research that suggests microplastics are problematic for both human and environmental health,” says Martin Thuo, a professor of materials science and engineering at NC State and co-corresponding author of a paper on the work. 

So with financial support from John Deere and the Center for Complex Particle Systems (COMPASS) — funded by the National Science Foundation and headquartered at the University of Michigan — Thuo says the research team set out to create a new lubricant that was safe and biodegradable.

“We ended up with something that is also relatively inexpensive, efficient, and makes use of sustainable, readily available materials.”

Derived from cellulose — a biodegradable, plant-based material — the new lubricant consists of millions of fibers so small, they’re measured in terms of millimeters and microns. The fibers’ surface is grafted with water-repelling particles. To the naked eye, the lubricant looks like powder. 

Not only does the new lubricant appear effective, but in proof-of-concept tests, it actually outperformed the best talc and microplastic lubricants on the market. In field trials with corn and soybean seeds, it performed at least five times better than commercial talc lubricants — and 25 times better than microplastic lubricants. 

“And the new lubricant outperforms commercial lubricants by even more when using smaller seeds, such as mustard and canola, or when there is high humidity,” says Udayashankara Jamadgni, who was a co-lead author of the paper, “Graph Theory Based Bioderived Solid Lubricant.”

In fact, it’s in high humidity or wet weather when the new lubricant might shine the most. 

“We’ve tested our cellulose-derived lubricant in wet conditions — up to 80% humidity — and it works beautifully. That was confirmed by farmers who used our new lubricant in blind field testing,” Thuo says. 

When mixed with seeds, the new lubricant reduces friction in two ways. First, since the fibers’ surface is smoother than the surface of the seeds, the fibers can slip between the seeds, thereby reducing the mechanical friction from seeds rubbing against each other. Second, the hydrophobic particles on the surface of the fibers repel adsorbed water on the surface of the seeds, making the fibers even more slippery. 

“Our lubricant handles wet conditions so well because the hydrophobic particles repel water on the surface of the seeds and stay slick,” Thuo explains.

But that’s not all. On top of being biodegradable and working better than the best talc and microplastic lubricants — especially in wet conditions — the new lubricant showed some potential benefits that the researchers didn’t expect to see. 

Most seeds used in crop agriculture have a thin coat of nutrients and pesticides. With conventional lubricants, some of this coating gets scraped off — and can then be released from the planting machinery’s exhaust system. 

That creates a “toxic cloud that poses risks for pollinators, birds and farmers,” Udayashankara Jamadgni says. “We were surprised to find that our cellulose-derived lubricant drastically reduces this problem — very little of the seed coating is scraped off. This is actually the topic of our next paper.”

What’s more, the researchers found that their new lubricant might even be reusable.

“We found that we are able to filter out the cellulose-derived fibers in the lubricant from the vacuum system used in farming machinery to plant the seeds,” Thuo says. “This means that very little of the lubricant itself is released into the environment — and the lubricant can actually be reused or properly disposed of. That will be in the next paper, too.”

This article is based on a news release from NC State University.

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“Graph Theory Based Bioderived Solid Lubricant,” published Oct. 7 in the journal Matter, was co-authored by Andrew Martin and Alana Pauls, postdoctoral researchers at NC State; Souvik Banerjee and Boyce Chang of Iowa State University; Xiong Ye Xiao and Kien Nguyen of the University of Southern California; and Anastasia Visheratina and Nancy Muyanja of the University of Michigan. Paul Gregory of ISU is co-lead author of the paper, and co-corresponding authors are Paul Bogdan, an associate professor of electrical and computer engineering at USC, and Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Chemical Engineering at U-M.

Multiple patents have been filed worldwide with regard to this technology; some have been granted, and others are pending. Thuo, Udayashankara Jamadgni, Kotov, Gregory and Chang are all listed as inventors on the U.S. patents.