Kansas City’s Water Services department has generated $2.1 million in net income over the past six years by reusing human waste as fertilizer on its own city-run biofuel farm – turning an expense into a revenue generator, the Kansas City Star reports.
The city maintains more than 2,500 miles of sewers, treating 96 million gallons of wastewater daily, and used to burn all that waste in incinerators. The process was expensive and a big consumer of water, gas and electricity, as well as a producer of ash byproducts, according to Kurt Bordewick, manager of the city’s wastewater treatment division.
So the city bought digesters to remove water from the waste, creating biosolids that could be applied as fertilizer. At first Kansas City maintained land that hosted tenant farmers, but in 2006 the municipality took over most of the farming itself.
The city now owns 1,340 acres along the Missouri River, next to its Birmingham wastewater treatment plant. The land produces corn and soybeans designated for sale to biofuel producers, so they stay outside the food chain.
Yearly income from the land jumped from about $50,000 in 2000-2005 to $455,451 in 2006-2011. In 2011, 9,982 tons of fertilizer were spread on the farm, and just 2,044 tons were incinerated, the Star said.
Kansas City was able to expand the fertilizer project with American Recovery and Reinvestment Act funding, the city website said.
The valuable nutrients and trace elements in human waste rarely get rechanneled back into agriculture, according to Design-Aire Engineering president Bob Boulware, writing in Environmental Leader. Most of the nutrients are either destroyed in treatment or enter the water cycle, where they increase unwanted algae. This has increased demand for chemical fertilizers, created using large amounts of energy and minerals including phosphorous, Boulware says.
Plant operators are finding a variety of ways to put wastewater to productive use, however. One method is biogas. Last February, Ameresco and the Philadelphia Water Department announced they will design, build and maintain a $47.5 million wastewater biogas-to-energy facility capable of generating 5.6 MW of power and reducing PWD’s energy costs by more than $12 million over 16 years.
And the Arizona Snowbowl has been using sewage effluent for snow-making, though a report has found that the system is a potential breeding ground for antibiotic-resistant bacteria.