The fascinating truth of converting human waste into fertilizer.
Biosolids are a valuable resource for agricultural farms.
For many, the very thought of spreading human manure across a field is quite revolting. However, a clever company in Madison, Wisconsin has found a way to make that practice much more accepted, and sanitary. Inside Madison's Metropolitan Sewerage District is a large building titled "Metrogro". In summary, this building houses the large intricate filtration systems needed to convert human waste collected from the area's sewer lines, into usable fertilizer. The final product has been give the name Metrogro, and is a nutrient rich organic fertilizer.
Let's take it from the start: what are biosolids? Biosolids are the solid portion of waste water or black water. Biosolids contain both micro and macro nutrients such as nitrogen and phosphorus that are beneficial for crop production. Unwanted contaminants and pathogens, such as heavy metals and E. Coli, are also found in biosolids which is why careful treatment and regulations are enforced when handling and treating biosolids. The Madison Metropolitan Sewerage District website features a biosolids fact sheet that outlines the various forms of fertilizers that biosolids can be converted into. By reusing biosolids, negative impacts on the environment are significantly reduced and farmers are presented with an organic fertilizer source. The goal is for farmers to rely less on commercial, chemical based, fertilizers and for biosolids to be treated in a more sustainable fashion.
Where can this organic fertilizer be used?
Just like with chemical fertilizers, detailed measures and precautions are followed to ensure fertilizer never ends up in or near drinking wells, fresh water sources, homes, or recreational areas.
"Metrogro staff evaluate all fields to meet Wisconsin Department of Natural Resources (WDNR) administrative code NR204, surveying soil types, depth to bedrock, groundwater levels, distance to wetlands or waterways, and other characteristics. Application follows safety protocols and strict setbacks from homes, wells, schools, and recreation areas. " - https://www.madsewer.org/what-we-do/resource-recovery/metrogro-biosolids-program/
Precise application of Metrogro is essential to reducing the risk of leaching to unwanted areas. This method of fertilizing also enables the crops to use up the nutrients they need over time, as in a "slow-release" fertilizer. This method has many other benefits as well, such as odor control and low soil disturbance.
"Federal and state government agencies heavily regulate the Metrogro program and our biosolids, including the U.S. Environmental Protection Agency (EPA) and WDNR. These regulations are in place to protect communities and the environment while also recovering valuable resources from the biosolids." - https://www.madsewer.org/what-we-do/resource-recovery/metrogro-biosolids-program/
The circular sanitation movement has begun.
From composting toilets used on a small homestead to forward thinking cities, such as Madison producing Metrogro, the recycling of biosolids is without a doubt gaining popularity and for good reason. Through regulated practices and precise application, biosolids can be converted not only into fertilizer, but into renewable energy that can be used to power many aspects of our daily lives.
Kelsey McWilliams, founder and managing director of Point of Shift has been paving the way for circular sanitation since 2021. Kelsey and her team focus on creating beautiful and functional toilet designs that integrate into active composting systems.