On July 30, researchers from the Ishii laboratory at the University of Minnesota came out to the Market to demonstrate an innovative method for removing nitrogen pollution from water: woodchip bioreactors.

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When nitrates build up in our local waters, algae blooms can develop which alter the water chemistry and make it difficult for many other animals and plants to thrive. Agriculture often needs to use nitrate-based fertilizer to grow crops, so researchers have worked to find ways to remove this nitrate from water draining off fields. Woodchip bioreactors are a sustainable method to remove up to 50% of the potential nitrate pollution!

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A demonstration of a woodchip bioreactor: the nitrate-loaded water would drain into the woodchips full of nitrate-breathing bacteria; they would breathe out NO2 (nitrogen gas) and leave the remaining water less polluted. In a field, the woodchips are all buried!


The woodchips act as a home and food for many small bacteria (tiny organisms or microbes). As we need oxygen to breathe, the microbes use the potentially polluting nitrate and breathe out (respire) nitrogen gas (NO2), which isn’t a pollutant. Then the water can run-off to nearby streams and eventually lakes with far less nitrate!

The systems are constantly being improved. The Ishii lab studies the microbes to try and select bacterial types that are more efficient at removing nitrates. Other researchers study the best ways to move water through the systems. Many farms in Minnesota and elsewhere already have woodchip bioreactors in their fields.

Thanks to the microbiologists of the Ishii Lab!

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