Wood Chip Bioreactor Controls Tile Line Nitrate Load

The Dudley Smith research farm in Illinois is tiled and wired. Todd Gleason has more on how the University of Illinois is doing nitrogen loss research near Pana.

Farmers gathered this week for a peek at the nitrogen loss control methods installed in Christian County. It’s a farm that rolls just a bit, but is pretty typical for the area other than the pastures on a portion of it. They came to hear from Laura Christianson. She’s a University of Illinois Crop Scientist, “At the Dudley Smith farm we have a wood chip bioreactor installed. A wood chip bioreactor is a little mini water treatment plant to clean nitrate out of tile drainage. The thing that makes the Dudley Smith bioreactor different is that is has baffles inside it. So, rather than the water just running straight through the wood chips, like most bioreactors, this bioreactor has baffles in it to make the water move in more of an S shape to improve how much nitrate is taken out of the drainage water”.

Early indications are the baffle is working as hoped. Wood chip bioreactors, even without the baffles, can remove between 20 and 40 percent of the annual nitrate load from a tile line. It’s technology farmers are interested in seeing and hopefully, says Christianson, deploying, “I think farmers are interested in wood chip bioreactors because it is something they can do that doesn’t impact their production practices. It is an edge of field practice, so you can keep on in the field however you are comfortable, but this catches that nitrate at the edge of the field before it goes down stream”.

A bioreactor is pretty simple to build. Use a backhoe to make a trench near the end of the tile, put a plastic liner in the trench, fill it with wood chips, be sure to have control structures on the inlet and outlet, and cover it with dirt. The chips will need to be replaced about every 10 years.