Paving roads with soybeans — the future of asphalt

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Soybeans can be used for many things. The versatile bean produces everything from healthy cooking oils to sustainable fuel, household products and animal feed.

That list is about to get longer if the Iowa Soybean Association and Iowa State University (ISU) are successful in helping soybean asphalt become a viable option for road construction and maintenance.

Farmers attending the 2022 Farm Progress Show at Boone, Iowa, caught a glimpse of the potential future of pavement when they visited the show’s Varied Industries Tent, which featured a 42,560 sq. ft soybean asphalt base.

This Farm Progress paving project is an extension of research conducted by ISU into the formulation of high-oleic soybean oil as a replacement for other expensive, highly volatile compounds commonly used in the creation of asphalt products. Using a cold-in-place technology, the project combines 100 percent recycled asphalt pavement mixed with a soy-based polymer. Creating the base for the Varied Industries Tent required more than 2,300 lbs. of soybean oil, or 215 bushels of soybeans. On average, each soybean bushel yields nearly 10.7 lbs. of oil.

Eric Cochran, professor at ISU’s department of chemical and biological engineering, says the university’s research and testing continues to focus on commercialization of a product that could create demand for soybeans, enable construction of more cost-efficient infrastructure, and benefit the environment.

“Every time an aging road is slated for demolition and reconstruction, a big milling truck is going to come and grind the top few inches of asphalt off the top of that pavement. It generates this gravel-like mixture that we call RAP — reclaimed asphalt pavement. Any paving contractor is going to have these stockpiles of asphalt that are waiting for a new home,” says Cochran.

The soybean-oil based polymer allows the RAP to be reconstructed into a new pavement by binding those gravel particles together. Crushed asphalt is sprayed with the soybean polymer and a compactor then presses the oil into the asphalt to make the final product.

Compared to hot mix asphalt pavement, Cochran says the soybean product can divert significant asphalt from landfills — saving the associated costs. He notes that asphalt also requires extreme heat in the mixing process. This process effectively uses soybean oil to replace the heating requirement and the energy needed to generate it. (Story continues below video)

Comparing the cost of hot mix and soybean asphalt, Cochran says the Varied Industries Tent project is somewhere between four and five times less costly. “Depending on how the soybean asphalt is formulated it can be between three to 10 time cheaper.”

In the big picture, Cochran says soybean asphalt likely fits best in creating an opportunity to expand infrastructure, helping to pave unpaved roads —including rural roads and farm access roads — at a drastically-reduced cost without a huge environmental impact.

In the interview, Cochran also discusses how the product could be a good fit for Canada. Research indicates that the soybean polymer has proven highly effective in making asphalt more crack resistant in cold weather climates.

Work on soybean asphalt began in 2013 and Cochran says the push to commercialization continues as research has moved from laboratory-scale experiments to pilot-scale manufacturing conducted at ISU’s BioCentury Research Farm. “We moved from that manufacturing facility into a full-scale chemical manufacturer last year.”

Click here for more Farm Progress Show coverage.

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Farm Progress Show (view all)Season 9 (2022) Episode 6
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