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Minnesota Biosolids Scene

Minnesota has more than 200 cities and sanitary districts that recycle biosolids as soil amendments and fertilizers. Biosolids are recycled to improve the fertility of cropland and forestland, as well as to restore and revegetate land impacted by the mining of iron and taconite.

Approximately 180,000 tons of biosolids (dry weight basis) are reclaimed from Minnesota wastewater every year. The majority of the biosolids produced in the state are incinerated at three locations - in St. Paul at the MCES Metropolitan Wastewater Treatment Plant, in Eagan at the MCES Seneca Wastewater Treatment Plant, and in Duluth at the Western Lake superior Sanitary district's (WLSSD) wastewater treatment plant. The WLSSD in Duluth is currently phasing out incineration and converting to a total biosolids recycling program.

The biosolids produced in the Minnesota managed in the following ways:

• 58% - Incinerated
• 26% - Biosolids Recycled
• 17% - Disposed in a Landfill

Pie-chart of the above data

One city in Minnesota, Grand Rapids, landfills its biosolids. Compared to other biosolids, the biosolids produced in Grand Rapids are high in wood fibers and clay and relatively low in nutrient value. This characteristic is the result of the high percentage of wastewater coming from the Blandin Papermill. Consequently, Grand Rapids biosolids are less attractive as a soil fertilizer. However, studies by the IRRRB and others have shown that Grand Rapids biosolids can be beneficial in the reclamation of mineland. Blandin Paper Company is also investigating the use of Grand Rapids biosolids as a mulch to reduce weed competition in tree plantations.

On a tonnage basis, the majority of Minnesota biosolids are incinerated, however on a management basis, most wastewater treatment facilities manage biosolids by recycling. In other words, over 200 facilities conduct biosolids recycling, 3 facilities conduct incineration and 1 conducts landfilling.

Biosolids recycling is especially popular with farmers in Minnesota. Many cities and sanitary districts that conduct biosolids recycling have waiting lists of farmers eager to use the product. They realize that biosolids are rich in slow-release organic nitrogen and phosphorus. But the fertility value is not the only beneficial attribute of biosolids, the organic matter is important as well. The organic mater is biosolids can improve the physical conditions of soil which can reduce runoff and erosion, increase waterholding capacity and bind soil particles making them more resistant to wind erosion.

For the past six years, a biosolids recycling exhibit has been conducted at the Minnesota State Fair. The exhibit is located on Machinery Hill just north of the John Deere exhibit. Thousands of state fair goers have visited the biosolids recycling exhibit over the years. Much information has been shared and many questions have been answered. Over two hundred farmers have signed up to receive biosolids at the State Fair alone.

The recycling of biosolids in Minnesota is regulated by the Minnesota Pollution Control Agency (MPCA). All biosolids that are recycled in Minnesota must be processed and tested before use. The biosolids must be low in potential contaminants and treated to reduce the levels of pathogens (i.e., germs) and odor. Operators conducting biosolids recycling must first get application sites approved by the MPCA and then follow "Best Management Practices," or BMPS, when conducting the application process. The following is a partial list of items that must be considered when recycling biosolids on land:

• Distance to residences and wells
• Distance to lakes, rivers, wetlands, and streams
• Depth to watertable and bedrock
• Landslope
• Soil Permeability
• Time of year (e.g., snow cover or frozen land)
• Soil pH and fertility level
• Crop to be gown
• Application rates

There are many things to learn before biosolids recycling can be conducted effectively by cities and sanitary districts. In fact, Minnesota is one of only a few states which require that biosolids recycling operators be certified by the state. To assist in this certification process, the MPCA and MCES conduct several 3-day training courses in biosolids recycling every year. Attendees of the workshops learn about the processing of biosolids, testing the material, site approval process, application BMPS, recordkeeping, and annual reporting. To learn more about the Minnesota biosolids regulatory program, contact the state biosolids coordinator, jorja.dufresene@pca.state.mn-us