Lou Licht, who received his PhD in the University of Iowa’s Department of Civil and Environmental Engineering, is using poplar trees to clean polluted water.

Licht started the Iowa-based company Ecolotree. This company installs forests of poplar trees near sites that leak pollutants. Through a process called phytoremediation, the roots of the poplar trees help filter some of the harmful pollutants, and keep them from contaminating the water and soil.

Ecolotree has worked with 110 sites in the U.S. and one in Europe.

Learn more about Licht and his company here.