Environment

The Metropolitan Sewer District is restarting a program that turns the city’s solid human waste into a kind of fertilizer. They plan to begin giving it away for free to farmers in June. 

For the last couple years, Louisville’s been trucking the city’s “solid” human waste to the landfill, said MSD Treatment facilities operations director Daymond Talley. 

“It takes up a lot of room in the landfill and it isn’t always friendly with the landfill,” he said. “They have to balance how much they can take and mix.”

This is probably too much information, but sewage is mostly water and about 1% solids. MSD treats the liquids and releases them into waterways. The district runs the solids through centrifuges to condense them into “cake,” which the city pays for the privilege of sending to the landfill. 

But it wasn’t always that way. From about 2004 through 2019, MSD ran the original Louisville Green program. Using massive rotary drum dryers to heat the biosolids and burn off any harmful bacteria, MSD converted the waste into small pellets. 

Metropolitan Sewer District

A pile of Louisville Green soil amendment pellets.

Over time the equipment began to break down until MSD suspended the program in 2020. Now the program is ramping back up. 

MSD has already put one new dryer in service, and is in the process of putting a second dryer online, Talley said. 

Their goal is to make 100 tons per day. It’s not technically fertilizer because fertilizer has certain levels of nitrogen and phosphorus and MSD can’t guarantee those in the product, but it serves the same purpose.

When the program is fully operational, it’ll save around a million cubic feet of landfill space per year, according to MSD’s Louisville Green website

Farming with Louisville Green

Louisville Green is free, but there’s a 15-ton minimum so unless you’ve got a really big garden, it’s mostly for farmers like Karl Weber from Indiana. 

Weber raises cows and grows corn and soybeans. He used Louisville Green for years before the program shut down and he’s excited for the program to start back up, because fertilizer is about twice as expensive as it was last year.  

“It’s tough. We’ve got a lot of inputs on the crops and it’s hard to make money,” he said. “I know [Louisville Green] works and it’ll really help us out.”

Weber said it’ll save him a couple hundred dollars per acre and he knows at least 10 other farmers who want to pick up their own truckloads. 

Those interested in the product, can email pellets@louisvillemsd.org for more information.

‘Forever chemicals’ and fertilizer made from biosolids

One unknown is the amount of PFAS chemicals present in Louisville Green’s product. PFAS, often called “forever chemicals,” are sometimes found in sewage waste that’s been turned into fertilizer, according to the Sierra Club

These chemicals persist in the environment for decades, have been linked to a number of health problems and can be taken up by plants when the chemicals are present in soil. 

However, there are no health standards for the presence of PFAS in fertilizer made from human waste. It’s unknown if the chemicals are present in Louisville Green, but it’s possible.

MSD said it plans to begin testing Louisville Green for the presence of PFAS. 

“There are no regulations for PFAS. The EPA is working on that and so what we are doing is we are going to start here in the next quarter or two quarters to do some PFAS initial sampling,” said Talley with MSD.  

 

 

 

Ryan Van Velzer is WFPL's Energy and Environment Reporter.