Designer Biochar to Capture and Recycle Phosphorous from Tile Drainage Systems

The main goal of this project is to develop a system that prevents nutrient losses from farmland in order to increase agricultural sustainability.

About Phosphorus Fertilizers

Phosphorus is essential for plant growth and is heavily used in agriculture as a component of fertilizer to increase crop yields. Applying too much phosphorus to fields or applying it at not quite the right time for plant growth can negatively impact the bottom line and the environment through losses of costly fertilizer through surface runoff. Compounding the issue of phosphorus loss is the fact that many fields in the Midwestern U.S. are tile-drained. Tile drainage is good for organic-rich, poorly-drained soils because it removes excess water that might inhibit plant growth. However, the downside of this system is that it creates preferential flow paths for nutrients through the subsurface, making it easier for phosphorus and other chemicals to leave the farmland and enter nearby waterways.

Impact of Phosphorus on the Environment

Excess phosphorus entering into the aquatic environment causes greater yield in aquatic plants, especially algae. This growth can be seen locally in the summer when a pond’s whole surface is covered in green “slime,” which is called an algal bloom. Algal blooms can happen on larger scales as well. Phosphorus and nitrogen in runoff from agricultural fields and residential lawns as well in effluent from wastewater treatment plants contribute to algal blooms in the Great Lakes and the oceans. The seasonal nature of the fertilizer use contributes to rapid algal growth in the summer and then die off once the fertilizer season is over. Huge numbers of dead and decaying algae create oxygen-depleted waters, which have a negative effect on most aquatic life. One example of this phenomenon is the anoxic dead zone in the Gulf of Mexico where large numbers of fish and other organisms die each year from lack of oxygen.

Project Details

To combat this excess phosphorus runoff problem, Wei Zheng and BK Sharma of ISTC along with other colleagues from the University of Illinois at Urbana-Champaign, the Metropolitan Water Reclamation District of Greater Chicago, Water Warriors, Fulton County Farm Bureau, and Illinois Farm Bureau believe that they can engineer a solution to keep phosphorus within the agricultural system and out of the aquatic environment. They have proposed to combine a woodchip bioreactor with designer biochar to capture phosphorus within the biochar. Biochar is a charcoal-like product produced by the pyrolysis of biomass and is composed largely of carbon.

The biochar can be removed from the bioreactor system periodically and spread over the field as a form of slow release phosphorus fertilizer. The bioreactor/biochar-channel system will be tied into the tile drainage system to remove excess nutrients before the water is released to a nearby stream. The team also believes that the bioreactor system will reduce fertilizer expenses with the capture and reuse of excess phosphorus on the designer biochar.

This project is funded by the Illinois Nutrient Research & Education Council. Results are expected in spring 2023.

woodchip bioreactor system

Proposed nutrient removal system.