Asphalt: It’s everywhere and it’s expensive. And its production is tough on air quality. But a researcher at Washington State University may have a better way: asphalt made from waste cooking oil. "Rock Doc" Kirsten Peters explains.
Dr. Haifang Wen grew up in a rural area of Shandong province, in eastern China. In his youth there were not many paved highways in the Chinese countryside.
“Lots of the roads were gravel,” he told me recently. “They were muddy when it rained. I remember riding a cow on them, or going along in a wagon pulled by a donkey.”