How Long Will Corncobs Improve Nitrogen Removal in Bioreactors?

Issue

Denitrification bioreactors are conservation practices designed to remove nitrate-nitrogen from tile drainage waters. Drainage water is routed through a long narrow subsurface chamber filled with a carbon substrate (typically woodchips) and denitrifying microorganisms, and then the treated water is discharged into a waterway. In 2013, the Iowa Nutrient Research Center (INRC) funded our proposal to install nine experimental woodchip bioreactors at the Agricultural Engineering Research Farm near ISU’s main campus. The reactors allow us to control the flow, nutrient concentration in the drainage, and carbon materials. In 2018 we replaced the first 25% or 75% of the length of the pilot-scale woodchip bioreactors with corncobs, and our monitoring has shown that the (and availability) of corncobs as a carbon source compared to woodchips. 

Objective

In this project, we will evaluate corncobs as a long-term alternative carbon source in denitrification bioreactors. 

Approach

We will monitor nitrate removed by the bioreactor, the ability of the corncob bioreactors to support good flow conditions and the potential for dissolved greenhouse gas production.also disseminate findings broadly through an extension publication, engage landowners through a farmer-focused field day,and identify long-term supply sources of CC. We are currently working with a corncob supplier, Green Products, to evaluate new methods of securing corncobs from field sites, in addition to the seed corn resources that we are already exploring.