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01/04/2013 08:53 AM     print story email story  

Kansas City Turns Sewer Sludge Into Money-Making Fertilizer

SustainableBusiness.com News

Kansas City has decided to fertilize its crops in a way that saves money but that's very controversial from an environmental standpoint.

Rather than incinerating the city's sewer sludge, it's being used as fertilizer at a 1340 acre farm near the water treatment plant.

Last year, 9,982 tons of fertilizer produced by wastewater operations were spread on the city-owned farm along the Missouri River, which grows corn and soybeans intended as biofuel feedstock.

So far, Kansas City has netted more than $2.1 million by using the sludge rather than burning it. City officials see it as a way to completely stop incinerating over time.

"That is an expensive process that takes a lot of water, takes a lot of gas, takes a lot of electricity, and it leaves us with a fairly inert ash," Kurt Bordewick, manager of the Water Services' wastewater treatment division, told Kansas City Star.

At first the city dealt with the problem by buying the watery waste in lagoons, adding more as the city grew. In the 1980s, they invested in digesters that create biosolids by removing the water from waste, which ended up as the fertilizer they use today.

Every city produces sewer sludge and they all need to figure out what to do with it. In this case, the sludge is being used for crops not intended for human consumption, but since the farm runs along the Missouri River, they have to be careful about fertilizer run off.

Communities have fought the use of sewage sludge as fertilizer because it "regularly tests positive for a host of heavy metals, flame retardants, polycyclic aromatic hydrocarbons, pharmaceuticals, phthalates, dioxins, and a host of other chemicals and organisms. Of the thousands of contaminants that have been found in sludge, the U.S. government regulates 10 of them (nine heavy metals and fecal coliform) if you want to spread the sludge on farm fields growing food crops," says Food Safety News.

Wastewater treatment plants remove as many contaminants as possible that's in the water from homes, industry and hospitals. Treated water is discharged into waterways as effluent and the solids that are left are called "sludge." Recently sludge has been rebranded as "biosolids."

Plenty of companies are trying to come up with uses for sludge, such as turning it into ethanol, or other kinds of renewable fuels.



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