Background

Since 2015, IFB has contributed to the NLRS, an impressive statewide effort. Through leadership and participation by our farmer members across the state, IFB has made meaningful contributions to water quality improvements in Illinois. From 2016 to the 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 that uses research, technology, and industry experience to assess and reduce nutrient loss to Illinois waters and 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, nonprofits, wastewater treatment agencies, the agricultural sector, and state and local government. The primary goals are to reduce nitrogen losses by 15% and total phosphorus losses by 25% by 2025, relative to established baseline conditions. The NLRS was released in July 2015 after multiple years of stakeholder discussions, in which IFB actively participated. Since 2015, IFB has continued to participate in NLRS meetings and work groups to guide the effort strategically. In addition, IFB created new programs in 2015 to support farmer implementation of best management practices (BMPs) to help Illinois meet the NLRS goals. 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 on four priority areas:

1. Education and outreach to farmers, landowners, and the general public.

2. Supporting research on best management practices to reduce nutrient loss from agricultural fields.

3. Supporting farmer implementation efforts across the state.

4. Demonstrating progress toward the NLRS's long-term goals.

The IFB Board of Directors committed significant financial resources and staff support to achieve ambitious goals, enabling IFB to tackle environmental challenges head-on. IFB will continue to demonstrate that voluntary, science-based, incentive-based conservation can 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 by implementing the NLRS across Illinois. This program funds CFB projects statewide 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 cover crop test plots, conducting watershed planning and water testing, and hosting education and outreach activities.

In 2020, the McHenry County Conservation District and the McHenry County Farm Bureau partnered for the woodchip bioreactor field day at the installation site. Since the spring of 2021, MCCD volunteers have been collecting water samples at the bioreactor's inlet and outlet structures, which are then delivered to research partners at the University of Illinois with support from the McHenry County Farm Bureau. The pictures above show these partners gathering for a Nutrient Stewardship Field Day at the bioreactor site. The bioreactor project, initiated by the Illinois Farm Bureau, aims to standardize the implementation of water-quality practices and prioritize environmental sustainability. The woodchip bioreactor has proven successful in reducing nutrient loss, a goal every farmer strives for. The Illinois Farm Bureau has already invested over $1.5 million to reduce nutrient loss in Illinois. Below are videos from both the 2020 and 2021 Woodchip Bioreactor Field Days.

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 essential element for life on this planet, but excess nitrogen in water poses risks to human and environmental health. When excess nitrogen is present in water, such as in tile drainage, a woodchip bioreactor is one option for cleaning the water before the nitrogen causes problems downstream.

A woodchip bioreactor is a trench filled with woodchips that removes nitrogen from water by maximizing denitrification. Denitrification is a natural part of the nitrogen cycle in which native bacteria convert nitrate (a form of nitrogen) in water into harmless nitrogen gas. These bacteria lend the "bio" to the name bioreactor. The woodchips serve as the bacteria's food source, and as nitrate in the water flows past the bacteria, they convert it to nitrogen gas, thus cleaning the water.

WOODCHIP BIOREACTOR DESIGN

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 remove nitrate from water draining 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 sizes for which most conventional bioreactors are designed. Most conventional bioreactors are long, narrow trenches, for example, 10 ft wide by 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 it and flows into the stream untreated.

NITROGEN TREATMENT

A subsequent Nutrient Stewardship Grant was applied for and received by our CFB for the installation of monitoring devices. Since then, MCCD volunteers have been recording flow rates and taking water samples at the inlet and outlet structures of the bioreactor. We deliver them to our research partners at the University of Illinois, who conduct testing and data analysis.

Table 1. Annual bioreactor flow and nitrate-nitrogen removal performance for 3 years of monitoring.

Water year	Percentage of flow from the field that was treated in the bioreactor	lb N/ac removed by the bioreactor annually	lb N removed by the bioreactor annually	Edge of field efficiency
2021*	100%	2.2	97	58%
2022	60%	6.4	289	7%
2023	82%	3.5	159	4%

* Monitoring started in April 2021; not a full water year

Our bioreactor removed 159 lb N from the drainage water in 2023. This represented a 4% reduction in N loss at the field edge. While the removal efficiencies appear low for this bioreactor over the two full years of data (7% and 4%), the mass of N removed was generally higher than that of most other bioreactors in Illinois, which tend to remove approximately 100 lb N per year. Since monitoring began on this bioreactor, it has captured 545 pounds of nitrogen that would have otherwise gone downstream.

McHenry County Conservation District Farm Management Program

McHenry County Conservation District (District) manages over 25,600 acres of open space, including woodlands, prairies, wetlands, and savannas. Within its holdings, the District leases roughly 5,400 acres of farmland and currently works with 70 farmers through its Farm Management Program. All farm tracts are managed under District-approved conservation plans that ensure adequate protection of natural resources. Whether District-owned or farmed by local farmers, these lands support scenic and cultural landscapes and provide relief from suburban sprawl. Agricultural land also helps control flooding, protect wetlands and watersheds, absorb and filter nutrients, and recharge groundwater.

The District's Farm Management Program helps preserve tracts of land as open space and keeps them 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 for schools and other local government agencies.

The District has implemented Best Management Practices (BMPs), 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 rainfall in recent years, leading to increased erosion and flooding. These changing weather patterns, along with the goal of a more sustainable agricultural program, have prompted the District to adopt a more aggressive conservation approach. New leases require no fall tillage, and cover crops are required on highly erodible land. The District is conducting field assessments by measuring crop residue (Figure 1), using shovel probes for soil health (Figure 2), and assessing 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 to produce a high-quality stream but also allow biologists and scientists to study and correlate farm practices with 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 of achieving a healthy, productive landscape.

Woodchip Bioreactor Research

Agricultural productivity in the US Midwest is supported by 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 through this practice, it is now fully integrated into the economy and culture of our crop production. However, by installing tile pipes to alter how water leaves our fields, we have also changed how nutrients 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 help keep our tile drainage systems functioning for good crop production while removing nitrate from drainage water before it moves downstream.

A woodchip bioreactor is a trench filled with wood chips that removes nitrate from tile drainage water. Bioreactors remove nitrate from water through denitrification, a natural part of the nitrogen cycle in which nitrate in the soil or in water is converted into benign nitrogen gas. This process has been happening for millions of years on its own, and in a bioreactor, ideal conditions are created to enhance this conversion. One important aspect of denitrification is that bacteria perform it. These denitrifying bacteria are the workhorses that convert the nitrate in the water to harmless nitrogen gas. In other words, inside a bioreactor, nitrate doesn't stick to the wood chips or get physically filtered out of the water. These bacteria biologically convert it into nitrogen gas. It is this biological conversion of nitrate that gives the name “bio”-reactor.

From a research perspective, two key measurements are needed to estimate the amount of nitrate a woodchip bioreactor has removed. First, researchers collect water samples at the inflow and outflow control structures. The samples are sent to a laboratory for nitrate analysis. The water leaving the bioreactor should have a lower nitrate concentration than the water entering it, indicating that the bioreactor is working. Often, automated samplers are used to collect water samples over long periods, so research staff don't have to be physically at the bioreactor to collect them.

However, collecting water samples alone does not provide a complete picture of a bioreactor's performance. The amount of water being treated in the bioreactor must also be quantified. The second component of bioreactor research is monitoring water flow. Small, hot-dog-shaped pressure transducers are placed in the control structures to continuously measure the force of water pushing down on them as it flows through the structures. 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 associated with a high flow rate, whereas shallower depths are associated with slower flow rates.

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