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Soy asphalt now has a successful track record

Article cover photo
The United Soybean Board and Iowa State University sponsored a test section of soy asphalt at the National Center for Asphalt Technology in Auburn, Alabama. (Photo: Joseph L. Murphy/Iowa Soybean Association)

By Joseph L. Murphy, ISA communications director

The success or failure of a project is often determined on the test track. Take the Daytona 500 as an example. Teams arrived weeks before the race for exhaustive testing before the big event. The race teams know that a turn of the wrench can be the difference between the checkered flag and not even qualifying.

Earlier this month, an Iowa farmer joined a team of engineers, scientists and consultants and traveled to the National Center for Asphalt Technology (NCAT) in Auburn, Ala., to get answers about the success or failure of soy-based biopolymer asphalt.

The team found that the new bio-based polymer for asphalt is a success in every definition of the word.

"Like biodiesel, this is another opportunity to have a value-added product here at home to increase the profitability of raising soybeans and decrease the cost of animal production," said Rolland Schnell, a farmer and former Iowa Soybean Association (ISA) director visiting the test track.

About a decade ago, ISA directors voted to use $125,000 as seed money matched by the United Soybean Board (USB) to build a pilot plant at Iowa State University that experimented with the production of asphalt using bio-polymers produced with soybean oil. After years of work, high-oleic soybean oil was developed for use as a binder to hold aggregates together and make asphalt.

"I'm excited because when you start in a lab, you have a dream," said Chris Williams, a professor in the department of civil, construction and environmental engineering at Iowa State University. His team has worked on developing the product since the beginning. "To see this dream being realized today is exciting. I truly believe this is going to create immense value for the people of Iowa and across the United States," He said.

The polymer offers a lower-cost, less volatile and cleaner alternative to the traditional petroleum-based binding agents used in asphalt. The soybean oil also increases the reuse rate on asphalt grindings from 17%to over 30% according to USB data.

"This is a project that was started several years ago and now we see it taken from the theoretical to the application," Schnell said.

Rolland Schnell pauses for a portrait at the NCAT test track. After nearly three years of testing the soy asphalt continues to show that it is a superior product. (Photo: Joseph L. Murphy/Iowa Soybean Association)

Track testing

NCAT was established in 1986 as a partnership between Auburn University and the National Asphalt Pavement Association (NAPA) Research and Education Foundation to provide practical research and development to meet the needs of maintaining America's highway infrastructure.

"What they do here is realistic in an accelerated timely manner," Williams said." This partnership allows us to project our market opportunities to a much broader audience."

NCAT was created to ensure this industry's ability to provide pavements that are durable, sustainable, quiet, safe and economical. Industry sponsors fund research on the 1.7-mile oval in 200-foot test sections. The real-world laboratory allows experimentation while avoiding the risk of failure on actual roadways.

"I learned that there is a whole lot more to a blacktop road that I ever dreamt about," Schnell said of his time at the test track. "By being at the track and seeing the results, it gives me confidence that the soy-based asphalt is equal to or superior to other asphalt."

There are more than 4 million miles of paved roads in the United States that require significant upkeep, opening the door to significant opportunities for high oleic soybean oil and soy-based asphalt for years to come. Farmers interested in growing high oleic soybeans in 2020 are available now, with several elevators across the Midwest.

The initial three-year test for the soy-based asphalt is expected to be finished this fall, according to Randy West, NCAT director. After the test, 10 million equivalent single axle loads (ESAL) will have passed over the asphalt test section. ESAL converts damage from wheel loads of various magnitudes and repetitions to damage from an equivalent number of "standard" or "equivalent" loads.

"That is a way for us to normalize truck traffic to an 18,000-pound axle load," West said. Researchers at NCAT are monitoring the performance of the product, looking for things like rutting and cracking.

“Over the 15 months, it has performed perfectly, and we don't expect there to be any changes between now and the conclusion of the 10 million ESAL cycle," West said.

A sponsorship sign at test section W10 on the test track recognizes the United Soybean Board and Iowa State University. (Photo: Joseph L. Murphy/Iowa Soybean Association)

The average life span of asphalt depends on traffic use and the environment. Still, data suggests that the national average for asphalt pavement is about 15 to 20 years, according to NCAT data.

"The key benefit of the soybean polymer is about rutting resistance and it has some benefit in cracking," West said.

According to NCAT officials, cracking happens over the lifespan of the asphalt. Further testing outside of the current three-year test will be needed to determine just how good the soy asphalt is over time.

"The way it is performing on the test track is a reassurance and a verification that the new soy-based binder for asphalt is going to be successful in many ways," Schnell said. “Not only cost but in endurance and flexibility. There is no reason why it won't be implemented; it just needs to get the wheel rolling."

Hearing from NCAT researchers and watching the soy-based asphalt withstand the loads of trucks testing the durability of the product, Schnell felt proud.

"This makes me feel confident that the soy future is bright," Schnell said while standing on the soy asphalt test section at the test track. "This is not going to be an overnight deal where we see increased profitability and it may not be in my farming career, but the long-term profitability of soybeans is in good hands with things like this."

Look for additional information about the bio-based soy asphalt in the next episode of The State of Soy.

Contact Joe Murphy at

For media inquiries, permission to republish articles or to request high-res photos, please contact Katie James, ISA Public Relations Manager at © 2020 Iowa Soybean Association. All rights reserved.