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.
Project Updates
Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.
January 2025
On May 14, 2024, we installed all field equipment of pilot-scale bioreactors. These bioreactors began operation on the same day, and water quality samples were collected weekly until August 27, 2024. All samples have been analyzed for nitrate and GHG (CH4, N2O, CO2), and a subset of samples are in the process of being analyzed for Total Organic Carbon (TOC).
We continued to communicate with the corncob suppliers (Green Products Company and Bayer) to discuss the supply chain of corncobs and the potential to expand and streamline the corncob markets in Iowa, which would benefit the expansion of corncob bioreactors. On October 29, 2024, Barbara Tran and Leigh Ann Long visited the Monck Family during harvest at their farm near Monicello, Iowa. The Moncks secured a corn cob harvester (Vermeer) and demonstrated corn cob collection with the intention to use the cobs for cattle bedding. The Monck family has also identified a location on their farm for installation of a corn cob bioreactor. The bioreactor will be designed by Iowa State ABE Engineer Andy Craig, and IDALS has committed to funding the project with a target installation of fall 2025. This will be the first installation of a corn cob bioreactor using locally harvested cobs. Green Products Company continues to be an excellent and engaged collaborator. They donated corncobs for the installation of the four field-scale corncob bioreactors, funded through the NRCS Iowa Partners for Conservation Program. Two bioreactors are 50% corn cob followed by 50% woodchips while the other two bioreactors are both 100% corn cobs. These are the first field-scale corncob bioreactors installed on private property and will serve as a demonstration.
Related accomplishments and activities
2 field days
Below is a list of our currently funded bioreactor projects. While we did not submit any proposals this last quarter, we have received related funding from a variety of sources including:
- A new project with USDA NIFA. • Machine Learning Algorithm for Woodchip Bioreactor Optimization. USDA NIFA AFRI. J Charbonnet, S. Laflamme, A. Arenas, M. Soupir. $300,000. 9/1/24 – 8/31/26.
- Forestry on Tap: Using local woodland resources to unlock the microbiome of bioreactors to improve water quality. USDA NIFA AFRI. M. Soupir, J.Y. Law, B. Beck, A. Howe, J. Comito. $749,939. 7/1/24 – 6/30/29.
- Increasing denitrifying bioreactor adoption by expanding carbon media options: corn cobs and small chips. NRCS Iowa CIG. M. Soupir, J.Y. Law, W. Beck. $135,701 (+$150,059 cost share). Duration: 9/16/23 to 9/15/26. Added to existing NRCS IPC contract
- Unlocking the bioreactor microbiome for nutrient management and water quality. Iowa Nutrient Research Center. A. Howe, S. Hall, M. Soupir, J. Lee, L. Hartfiel. $133,009. 8/22 – 7/24.
- Forest-to-Farm: Innovative carbon media and supply network for enhanced bioreactor adoption and performance. NRCS IPC. M. Soupir, W. Beck, J.Y. Law. $336,106 (+128,402 cost share). 9/16/22 to 9/15/27.
- Forest-to-Farm: An innovative network to diversify wood product markets, encourage sustainable forest management, and enhance water quality USDA US Forest Service Wood Innovations Funding Program W. Beck, M. Soupir, J.Y. Law. $241,216 (+$241,216 cost share)