McHenry County Bioreactor


Since 2015, IFB has contributed to an impressive statewide effort, the NLRS. Through leadership and participation from our farmer members across the state, IFB has been able to make meaningful contributions toward water quality improvements in Illinois. From 2016 to present, IFB has committed approximately $1.5 million of its own funding to build and maintain its sustainability programs. The NLRS is a science-based framework for using research, technology and industry experience to assess and reduce nutrient loss to Illinois waters and to the Gulf of Mexico. The NLRS sets forth a plan to leverage existing programs to optimize nutrient loss reduction while promoting collaboration, research, and innovation among the private sector, academia, non-profits, wastewater treatment agencies, the agricultural sector, and state and local government. The primary goals include reducing nitratenitrogen losses by 15% and reducing total phosphorus losses by 25% by the year 2025 from established baseline conditions. The NLRS was released in July of 2015 after multiple years of stakeholder discussions in which IFB actively participated. Since 2015, IFB has continued its participation in NLRS meetings and work groups in order to strategically guide the effort. In addition, IFB created new programs in 2015 to support farmer implementation of best management practices (BMPs) to help Illinois meet the goals of the NLRS. For the past several years, IFB has made it an organizational priority to lead on environmental issues, most notably, the NLRS. IFB’s NLRS efforts focus in four priority areas: 1) education and outreach to farmers, landowners and the general public; 2) supporting research of best management practices to reduce nutrient loss from agricultural fields; 3) supporting farmer implementation efforts across the state; and 4) demonstrating progress toward the long-term goals of the NLRS. The IFB Board of Directors committed significant financial resources and support from staff to accomplish some ambitious goals, allowing IFB to tackle environmental challenges head-on. IFB will continue to prove that voluntary, incentive-based conservation, based on science, will move the needle on water quality improvements in our state. The IFB Nutrient Stewardship Grant Program is one example of the many ways IFB is creating lasting impacts in implementing the NLRS across Illinois. This program funds CFB projects throughout the state focused on improving soil health and water quality. Since 2015, IFB has dedicated over $550,000 to CFBs to complete a wide range of unique projects, including planting test plots of cover crops, watershed planning, water testing, hosting education and outreach activities.




In 2020, the McHenry County Conservation District and the McHenry County Farm Bureau partnered up for the woodchip bioreactor field day at the site where the bioreactor was installed. Since Spring of 2021, MCCD volunteers have begun taking water samples at the inlet and outlet structures of the bioreactor, which were then delivered to research partners at the University of Illinois with the help of the McHenry County Farm Bureau. The pictures above show these partners gathering for a Nutrient Stewardship Field Day at the site of the bioreactor. The bioreactor project, initiated by the Illinois Farm Bureau, serves the purpose of standardizing the implementation of water-quality practices and prioritizing envirnomental sustainability. The woodchip bioreactor has proven to be successful in reducing nutrient loss, which is something that every farmer strives for. The Illinois Farm Bureau has already invested over $1.5 million toward nutrient loss reduction in Illinois. Below are videos surrounding both the 2020 Woodchip Bioreactor Field Day and the 2021 Woodchip Bioreactor Field Day.


2020 shortened version (click on image to open link):


2020 full length version (click on image to open link):


2021 shortened version (click on image to open link):


2021 full length version (click on image to open link):



The Science Behind It


Nitrogen is an element that is essential for life on this planet but excess amounts of nitrogen in water cause concern for human and environmental health. When excess amounts of nitrogen are found in water, such as tile drainage, a woodchip bioreactor is one option to clean the water before the nitrogen causes a problem downstream.

A woodchip bioreactor is a trench full of woodchips that cleans nitrogen from water by maximizing the process of denitrification. Denitrification is a natural part of the nitrogen cycle where native bacteria convert nitrate (a form of nitrogen) in the water to harmless nitrogen gas. It’s these bacteria that lend the “bio” to the name bioreactor. The woodchips serve as the bacteria’s food source, and as nitrate in the water flows by the bacteria, they convert the nitrate to nitrogen gas, thus cleaning the water.



With the assistance of an Illinois Farm Bureau (IFB) Nutrient Stewardship Grant and in partnership with McHenry County Farm Bureau (CFB), a 40 ft wide x 40 ft long bioreactor on a McHenry County Conservation District (MCCD) property was built in 2020 to clean nitrate in water from a 45-acre tile drained field. The drainage system outlet pipe was 12” in diameter, which was relatively large compared to the 6” or 8” outlet pipe size for which most conventional bioreactors are designed. Most of these conventional bioreactors are long and narrow trenches, for example, 10 ft wide x 50 ft long. However, because this outlet tile pipe was a larger diameter and would thus carry more water than most bioreactor situations, this bioreactor was purposely designed to be wider. Water that is not captured by the bioreactor bypasses to the stream and is untreated.



In summary, from April 2021 to April 2022, the bioreactor captured 78% of the flow and removed 170 pounds of nitrate-nitrogen. This means the bioreactor removed 11% of the nitrogen that would have otherwise gone downstream.



Devoted volunteers have collected samples of water entering and exiting the bioreactor at least weekly since April 2021. Every sample event shows that nitrate is being removed across the bioreactor. In other words, the nitrate concentrations in the water leaving the bioreactor (blue triangles in the figure) are all lower than the nitrate concentrations in the water entering the bioreactor (red circles) for samples collected on the same date.

The nitrate concentration reduction provided by the bioreactor (the difference between the circles and triangles) is impacted by how fast the water moves through the woodchips. When the bioreactor’s flow rate was less than 15 gallons per minute, like in late summer 2021, the bioreactor generally removed all the nitrate that entered. However, when drainage flows increased starting in October 2021, the difference between the nitrate concentrations for water entering and exiting the bioreactor was reduced. This is because the water was moving faster through the bioreactor, which gives less time for the natural bacteria to do their biological process of denitrification.

An additional compounding factor is that winter and spring drainage water flows are cooler than summer flow. Water temperature impacts all biological processes, including denitrification, with cooler temperatures slowing these processes.




McHenry County Conservation District Farm Management Program

McHenry County Conservation District (District) manages over 25,600 acres of open space graced with woodlands, prairies, wetlands, and savannas. Within its holdings, the District also leases roughly 5,400 acres in farmland and currently works with 70 different farmers as part of its Farm Management Program. All of the farm tracts are managed with District-approved conservation plans that ensure adequate protection and conservation of natural resources. Whether it’s District-owned parcels or fields of local farmers, both allow for scenic and cultural landscapes and provide relief from suburban sprawl. Agricultural land also helps to control flooding, protect wetlands and watersheds, absorb and filter nutrients, and provide groundwater recharge.

The District’s Farm Management Program helps to preserve tracts of land as open space and keeps it set aside for future improvements without the threat of development. It also preserves a way of life in the county, provides jobs, and builds a partnership with local farmers. Leasehold taxes are paid on District Agricultural Lands to maintain revenue to schools and other local government agencies.

The District has implemented Best Management Practices (BMP’s) such as field borders, filter strips, crop rotation, and grass waterways for many years. McHenry County, along with much of the Midwest, has experienced heavy rain events in recent years, which has led to an increase in erosion and flooding. The changing weather pattern, along with the goal of a more sustainable Agricultural program, has prompted the District to take a more aggressive approach to conservation. New leases require no fall tillage, and cover crops are required on highly erodible land. The District is conducting farm field assessments by measuring crop residue (Figure 1), shovel probes for soil health (Figure 2), and soil compaction (Figure 3) along with standard soil testing.

The recently implemented bioreactor project (Figure 4) is another step in proactively implementing a conservation practice. The bioreactor will not only treat drain tile water in a high-quality stream, but it will also give biologists and scientists an opportunity to study and correlate farm practices and environmental health.

We are ultimately tied to the land for food, water, wildlife, and clean air. Blending sustainable agricultural practices with natural areas gives the District the best chance for a healthy and productive landscape.

Woodchip Bioreactor Research

Agricultural productivity in the US Midwest is underlain by a foundation of more than 48 million acres of tile drainage networks, with approximately 10 million tile-drained acres in Illinois alone. After more than 150 years of improving land drainage in this way, this practice is fully integrated into the economy and culture of our crop production. However, in changing how water leaves our fields by installing tile pipes, we have also changed how nutrients can leave our fields. Nitrate is a particularly tricky nutrient because it does not “stick” to soil and is thus highly susceptible to leaching. Edge-of-field practices like woodchip bioreactors allow us to keep our tile drainage systems functioning for good crop production while also cleaning nitrate out of drainage water before it moves downstream.

A woodchip bioreactor is a woodchip-filled trench that cleans nitrate from tile drainage water. Bioreactors clean nitrate from water using the process of denitrification, which is a natural part of the nitrogen cycle where nitrate in the soil or in water is converted into benign nitrogen gas. This process of denitrification has been happening for millions of years on its own, and in a bioreactor, ideal conditions are created to enhance this nitrate conversion. One of the important aspects of denitrification is that the process is performed by bacteria. These denitrifying bacteria are the work horses of converting the nitrate in the water to harmless nitrogen gas. In other words, inside a bioreactor, the nitrate doesn’t stick to the woodchips or get physically filtered out of the water. It is biologically converted into nitrogen gas by these bacteria. It is this biological conversion of nitrate that lends the name “bio”- reactor.


From a research perspective, there are two main pieces of information needed to estimate how much nitrate a woodchip bioreactor has removed. Firstly, researchers collect water samples at the inflow control structure and at the outflow control structure. The water samples are brought to a laboratory and are analyzed to determine their nitrate concentrations. There should be a lower nitrate concentration in the water, leaving the bioreactor compared to the water flowing in. That means the bioreactor is working. Oftentimes automated samplers are used to do the water sampling, so research staff doesn’t have to be physically at the bioreactor to collect the samples over long periods of time.

However, simply collecting water samples does not provide the full picture of how well a bioreactor is working. The amount of water being treated in the bioreactor also needs to be quantified. The second component of bioreactor research is monitoring the water flow. Small hot-dog shaped pressure transducers are placed in the control structures to continuously record how much water is pushing down on them as the water flows through the structure. That water depth is logged and later related to a flow rate using an equation in the laboratory. A lot of water pushing down on the pressure transducer is related to a high flow rate, whereas relatively shallower depths of water pushing down on the pressure transducer are related to relatively slower water flow rates.

One of the most commonly asked questions about bioreactors is: “How long do the woodchips last?” Practical observation and research across the US Midwest have shown woodchips in a bioreactor last approximately 7-12 years before the woodchips need to be replaced (or, “recharged”). Another common question involves if the type of woodchip matters. The short answer is the tree species used to make the woodchips generally does not matter. All woods contain roughly the same amount of carbon, which is the fuel for the process of denitrification inside a bioreactor. Rather than the type of tree, it’s the physical size and shape of the woodchips that are more important. Locally-available woodchips will be most cost-effective, but they must be clean from leaves or dirt. Ideally, the woodchips should have a square/ rectangular “chip shape” and be around 1” or more in size. There is a restriction on the use of oak woodchips due to concerns about leaching of tannins, although this is an area of active research.