USDA field pilots have found that when most of the woodchips inside nitrate-removing bioreactors are replaced by corn cobs, farm drainage water is cleaned faster. In a study led by Iowa State University with USDA-ARS scientist Gary Feyereisen, published online in December 2022 in the Journal of Environmental Management, bioreactor beds built with 75 percent corn cobs removed nitrate at 1.6 to 10 times the rate of an all-woodchip bed. Woodchips have been the default material in these systems for over a decade, so a result like this points to a change in how farms across the Midwest could treat drainage water more effectively and, at a lower cost.
What is a nitrate bioreactor, and why should you care
