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Kansas City turns human waste into fertilizer for city trees
Kansas City is turning black into green: black as in sewage and green as in leafy trees.
The city is using “biosolids” — yes, they are what they sound like — as a high-power fertilizer to nourish hundreds of saplings destined to shade the city’s streets and grace its parks.
But the benefits go beyond aesthetics. The city saves money on trees, the trees improve air quality, and something distasteful gets turned into something useful.
“We’re trying to do the full circle here,” said Forest Decker, manager of forestry and conservation in the Kansas City Parks and Recreation Department.
Decker looked out recently on two acres of young trees planted in rows on the grounds of the city’s Birmingham sewage treatment plant in the bottoms on the north side of the Missouri River. Behind him on the hill were large lagoons storing human byproducts that used to be incinerated.
For several years, Tim Walters, agronomist for the Kansas City Water Services Department, has been using biosolids to fertilize trees and crops on the roughly 1,300-acre property. Last fall, Decker’s crew and volunteers also began planting young trees here for later transplantation throughout the city.
Kansas City receives the trees, of a variety of species, for free from a nonprofit organization called Forest ReLeaf of Missouri. By the time they are transplanted, the city will have spent about $80 a tree, roughly a third of the cost to buy from a commercial nursery.
That will be a great help as the city aims toward a goal of planting 120,000 additional trees in the coming decade. Decker can plant about 625 trees an acre, and he has 40 acres of room to expand. The first saplings will be big enough to transplant by fall 2010. That’s a quick turnaround.
“In normal conditions, it would probably take them four years to reach the size that we need them to be,” Decker said. “We’re going to cut that time in half.”
That is because of the rich nitrogen content and other nutrients in the biosolids. Elsewhere on the water department property, cottonwoods planted just four years ago and fertilized with biosolids soar 50 feet or higher. The department also grows corn and soybeans with the stuff and got $680,000 by selling last year’s crop for animal feed or biodiesel fuel.
All that is gravy for the water department, which also saves about $20,000 a month by not incinerating the biosolids, Walters said.
“We’re getting rid of something that used to be considered a waste and used to cost us a lot of money to deal with,” he said. “Now we’re making money on the deal.”
The Birmingham sewage plant takes in waste from Kansas City, North, as well as Liberty and Gladstone. After initial treatment to remove most of the liquids, what’s left gets pumped under the river to the Blue River plant in the East Bottoms. There the solids from Birmingham and other treatment plants in the city are further processed, or “cooked,” before being pumped back to the lagoons at Birmingham.
Walters’ operation handles about 8,000 dry tons of biosolids a year and could use even more. The material contains about 250,000 pounds of nitrogen. By spraying it on the soil, Walters estimates he also is sequestering about 1,125 tons of carbon that otherwise would go into the atmosphere.
Such operations are not unique to Kansas City. The Environmental Protection Agency, which regulates the use of biosolids, estimates about half of them produced in the country are returned to the land. But Decker said he is not aware of many other places where biosolids are used to nurture trees for transplanting on public property.
The Birmingham lagoons have a noticeable odor up close, but the operation is in a relatively isolated area. Monitoring wells on site and at the river allow officials to make sure they are not discharging excessive amounts of nitrogen or other chemicals or heavy metals into the water table or the river. The Missouri Department of Natural Resources also watches the results.
These biosolids are not processed enough to allow for use on human food crops, and they are not available to the public.
Decker and Walters were recently recognized for their work by the Kansas City Environmental Management Commission.
