Rather than disposing of biosolids — the organic matter from sewage — St. Joseph’s water protection facility is leading the way in new technology to turn those biosolids into fertilizer.
The city purchased a biosolids dryer, the largest in the country, to take the sludge from the wastewater stream at the facility and dry it out into small tiny black pellets of fertilizer. The sludge is processed in an anaerobic digester for 40 days. It then goes through what is essentially a furnace for 90 minutes to produce the fertilizer.
The previous operation was taking sludge, dewatering it and dumping the biosolids on land by Rosecrans Memorial Airport. To save money, the city changed the process.
“We use several fields over there and we were getting to the point where we had to start looking at the purchase of new land within the next several years,” said Eddie Leaverton, the superintendent of water protection. “As part of that process, we started to think about how we could dispose of our biosolids in a more financially responsible and economically friendly way. We settled on the biosolids dryer.”
The biosolids dryer has cut costs in half, saving the city $150,000 to $200,000 a year. It also provides an opportunity for the city to make revenue by selling the fertilizer.
“I have seen some rough estimates between around $20 and $40 per ton; that’s kind of the price range that we’ve been looking at,” Leaverton said. “There’s some flexibility there — (it) depends on what the customer is looking for.”
The fertilizer isn’t just for farmers — it can also can be used in backyard gardens. The city said this fertilizer is better than the kind you can buy at hardware stores because it has additional nutrients.
“With standard fertilizers, you have to be really careful on your rates. In your yard, it’ll burn your grass,” said Andy Clements, the director of public works and transportation. “With a biologically produced fertilizer, it’s not high content with phosphorus or nitrogen, but it releases really slowly. You won’t get a real quick green, you’ll get a long continuous green.”
St. Joseph is a trailblazer in this process. It is one of the first cities in Missouri, along with Cape Girardeau, to dry biosolids into fertilizer. And it’s receiving national attention.
“I’ve talked with a few other municipalities around the country that have called to inquire about the dryer, the technology and how it works and what benefit we see from it,” Leaverton said. “I think it’s starting to generate a lot of interest around the country.”
The fertilizer has been approved by the Missouri Department of Natural Resources, and the city is awaiting certification from the Missouri Fertilizer Control Board. Once those steps are taken, the city will look for customers and begin to apply the fertilizer at facilities in town.
“There are a couple of other options available for biosolids disposal, but we felt like this was the option that gave us the best beneficial reuse of the biosolids we were already removing from the wastewater,” Leaverton said.