Rethinking Biosolids as Fertilizer

Even though I’ve been a big fan of Milorganite for lawns and shrub beds over the years, news stories over the past 10 months have given me pause.

On the plus side, are its characteristics as a non-burning and slow-release organic fertilizer, as well as a level of iron (Fe) that helps establish turfgrass seedlings, and greens-up ornamental plants in the landscape. Frequent applications are also thought to repel whitetail deer.
The latest concern about using biosolids relate to PFAS, and what are known as “forever chemicals.” It was a February 16, 2022 story from Maine, in the Bangor Daily News, “Unity Farmers Want Maine to Take Action After Finding PFAS on Their Property” that garnered a great deal of new attention on the issue…

“Nordell and Davis believe the contamination happened during the 1990s, long before they purchased the 20-acre farm in the heart of the central Maine farming community. Back then, both the Kennebec Sanitary Treatment District and the Portland Water District applied for and received licenses from the Maine Department of Environmental Protection to apply wastewater treatment plant sludge on the land. Treated sludge, also called biosolid compost, was widely used as a fertilizer.”

Abigail Curtis / Bangor Daily News / February 16, 2022
Adam and Johanna, owners of the Songbird Organic Farm issued a statement to “Friends and Customers” which reads, in part…

“We are farmers, not doctors or toxicologists, but it is our understanding that there is no immediate health risk from the vegetables and grain products you have already eaten. These PFAS chemicals represent a long term exposure concern rather than a single exposure risk. Knowing where they are present and reducing all of our exposure to them is what we are trying to do.”

Adam Nordell and Johanna Davis / PFAS Statement
The history of the soil on our home property is much different than the farm in Maine, and we don’t have a water well or grow produce, but continued use of Milorganite still concerns me. Researching this issue further, I found an older news story on this issue, in the Milwaukee Journal Sentinel, “Here’s what you should know about Milorganite and a recent study showing it may contain ‘forever chemicals” that included this…

“Are there PFAS in Milorganite? Yes, some PFAS were found in the popular fertilizer. PFOA and PFOS, two of the most well-researched forms of the chemicals, were both detected. PFOA was detected at 0.67 parts per billion, under 2.5 parts per billion limit for the chemical in Maine, which was used as the standard for the study because it has the strictest requirements for PFAS in biosolids. PFOS, however, was detected at 8.66 parts per billion in Milorganite, over the 5.2 parts per billion standard set by Maine. The study found that some precursors to PFAS were contained in the Milwaukee fertilizer as well, which degrade over time to form actual PFAS.”

By Laura Schulte / Milwaukee Journal Sentinel / June 7, 2021
Next stop was the Milorganite® website for their information, including this…

“The PFAS issue in biosolids fertilizer is a relatively new issue, and there is no clear indication that Milorganite fertilizer has a PFAS build-up that need’s remediation. Experience has shown PFAS concentrations in biosolids vary significantly depending upon local conditions, such as the type of water supply, the presence of fire suppression training sites, and industries that manufacture or use PFAS. For Milorganite fertilizer, local conditions that contribute to the production of our product favor low concentrations. In fact, PFAS sampling for Maine, concentrations for two of the three analyzed compounds were below the level of detection and the third was slightly above the level of detection, confirming minimal PFAS risk.”

Milorganite® Safety
For some really technical data, you can read this PDF, “PFAS – More Than You Ever Wanted to Know and Then Some” from the 2019 BIOSOLIDS CONFERENCE.
Finally, it was interesting to read the comments under a blog post on reddit.
Due to what appeared to be supply chain issues, Milorganite was hard to find in local stores last year. As we enter Spring 2022, we’re reading of global fertilizer shortages and price increases, so it will be an interesting growing season for gardeners and farmers.

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