Nature's Filter

Picture of Gary Feyereisen and BioreactorEvery problem has a solution.

Finding it is just a matter of where and how you look.

CFANS sees what other's can't. And when it comes to clean water, we make farms part of the solution.

Nitrate is a vital nutrient for plants and modern farming practices have helped us provide food for a hungry world. But when nitrates leach from our fields, it can poison our drinking water and contribute to the dead zone in the Gulf of Mexico, harming marine life.

By using what farmers have readily available, agricultural residue like corn cobs, we can remove excess nitrates before they enter our waterways. Bioreactor technology has been developing for years using materials like wood chips as the medium. Soil, Water, and Climate professor  and USDA-ARS agricultural engineer Dr. Gary Feyereisen and his team are testing agricultural residue materials more readily on hand for farms for use in the bioreactors.

"We found that these materials, corn cobs, specifically, performed better than wood chips," said Feyereisen. The difference in the performace was even more notably in colder temperatures, an importanct facor in places like Minnesota.

"We know that in the Upper Midwest, especially in Minnesota, much of the farm field drainage occurs during April and May when the ground temperatures are cold and the water is cold," explains Feyereisen. The bioreactor relies on microbe colonies in the agricultural residue to filter the nitrates out of the water. The microbes use the nitrate for respiration, turning it into gaseous nitrogen which is release harmlessly into the atmosphere.

The project will undergo field testing to evaluate performance and collect data outside of the lab in real world conditions. The project is funded by AURI, Minnesota Corn Research & Promotion Council, and the U.S. Department of Agriculture's Agricultural Research Service (USDA-ARS). The University of Minnesota provides space and materials for the research.

Agricultural residue types

Researchers by Bioreactors

Top: Various types of media/agricultural residue tested in the bioreactors.

Bottom: Gary Feyerisen, Todd Schumacher and University of Minnesota student Elizabeth Selvik work to test fibers in a denitrifying bioreactor.

Photos by Rolf Hagberg Photography and used with permission from AURI.