Metrogro: A Wastewater Win-Win

by Garret Hopkins, Rock River Coalition

On average, every person flushes their toilet at least five times per day. If you are connected to municipal sewer service or have a septic tank that gets pumped regularly, this wastewater makes its way to a wastewater treatment plant. These facilities clean the wastewater by removing all solid waste and other contaminants, and then send the clean water back to local waterways and store the leftover organic matter, called biosolids, in enormous tanks. Dane County’s largest wastewater utility, Madison Metropolitan Sewerage District (District), has been a leader in innovation for biosolids management since the 1930s.


“The District has always looked for a way to make this management of our solids a gold standard,” says Martye Griffin, Director of Ecosystem Services at the District. “Way back in the 1930s, they dealt with biosolids by air-drying them, bagging them and selling them locally as fertilizer. This product was called Nitro Humus.” In the 1980s, the District began storing biosolids in a more economical near-liquid form, and renamed their product Metrogro. And while the density of the product changed, its final destination did not. On a yearly basis, more than 5,000 acres of south-central Wisconsin farmland are fertilized with Metrogro.

The thought of using human-based fertilizer on crops may be less than appetizing. But a quick peek into the treatment process should calm any qualms. “We understand some members of the community believe biosolids are not safe,” said Amanda Wegner, Communications Director at the District, “but we follow strict DNR and EPA regulations.” Before Metrogro is applied, it undergoes multiple rounds of treatment to control bacteria and other potentially harmful organisms. It is then tested to ensure quality and safety. What remains is a highly sustainable substance filled with micro-nutrients.

Those concerned by what Metrogro is would likely feel better by reflecting on what Metrogro is not. Perhaps most importantly, it is not a chemical-based fertilizer. Commercial fertilizers pollute water, degrade soil and harm wildlife and local organisms at a higher rate. It is also not expensive. In fact, Metrogro – and the labor required to apply it to the land – is free to all farmers who choose to use it. The District, which owns and operates all of the application equipment, adheres to specific DNR regulations when delivering Metrogro. Specifically, application is done in a way to avoid harmful runoff into local waterways. “There are specific locations on the farms we target,” says Zac Thompson, Biosolids Specialist at the District. “First, we go out and do a site investigation. We check for shallow ground water and bedrock. Then we inject it underground. We want to make sure the nutrients we use stay on the landscape where they belong.”

While Metrogro is extremely beneficial for the farmers that use it for the cash-grain crops grown on their farms, it’s equally beneficial for the District. “Every time someone flushes the toilet, there is organic matter in there,” says Wegner. “We always have a constant stream of materials to create biosolids. We have storage on site, but it’s limited. If we couldn’t get this product out into the fields, we would have to figure something out.” Alternative solutions would likely be more expensive and less ecofriendly.

The District’s service area generates approximately 110,000 gallons of biosolids each day, and the District transports approximately 38 million gallons of Metrogro to Dane County farmland each year.

Wegner says Metrogro is a win-win solution. “It’s safe, it’s beneficial. It saves farmers money. And it’s a natural byproduct of all of us.”