Washington State University civil engineering assistant professor Haifang Wen (pictured) has created a "bioasphalt" mixture from waste cooking oil that binds aggregate at a lower temperature and a lower cost than the common petroleum-based method, without sacrificing strength or reliability. Trials of the material could begin as early as this summer.
Credit: WSU News

A Washington State University researcher has developed an asphalt binding agent from leftover restaurant cooking oil that could be cheaper, more sustainable and just as reliable as its petroleum-based counterpart.

Developed by Haifang Wen, an assistant professor in WSU's Civil and Environmental Engineering department, the bioasphalt may soon find its way beneath the tires of Washington motorists.

"We are shooting for summer 2014 to construct a trial road"?uprobably at least a quarter mile long," Wen said in a WSU statement.

Asphalt binder, which holds crushed stone and sand together to form pavement, only accounts for about five percent of the final hot mix asphalt (HMA) that gets steamrolled into surfacing. Since HMA has to be tough enough to withstand the rigors of weather and heavy truck traffic, Wen subjected each component of his bioasphalt to a series of rigorous stress tests, including intense heat, freezing temperatures, compression and loading.

Increasing petroleum prices, new environmental regulations and changes to the crude oil refining process has made asphalt a costly commodity. Made from the residue left behind after production of gasoline, plastics, and other materials, asphalt commands $700-800 per ton, or half the price of gasoline at $1,500 per ton, Wen estimates.

"Every year in the U.S., we use about 30 million tons of asphalt binder for roads," Wen said. "In general, a one-mile road in a rural area costs at least a million dollars to build. With the waste cooking oil technology, we can reduce the cost of asphalt binder to under $200 per ton, making road building much cheaper."

Bioasphalt's potential for savings extends to energy use as well. Traditionally, asphalt has to be heated to 300 degrees to be applied properly. Using different mixtures, Wen's group is researching materials that need only be heated to 200 or 220 degrees, requiring less effort and energy for production, and keeping the fumes produced by traditional asphalt out of worker's lungs.

The Federal Highway Administration grant recently contributed $1 million to continue funding Wen's research, an investment that followed a $190,000 grant from the National Science Foundation. After four years of work with a chemist to "adjust the recipe," Wen believes that his sustainable asphalt is as good as the conventional, petroleum-based alternative.