The Milorganite® recipe for success
The technological journey toward the finished product begins with collection in interceptor sewers of wastewater and preliminary treatment to remove solid materials. Microbes are then added to the water — the activation process — to digest the nutrients in the water. Binding agents are added to the water, causing the microbes to clump together and settle to the bottom of the undisturbed water in sedimentation tanks. After settling, the cleaned water is returned to nearby Lake Michigan. The microbe clumps are sent to the city’s Jones Island water reclamation facility where the material is dewatered and dried to 95% solids in one of twelve rotary kiln driers. The now-pelletized material is then sent by rail car or truck to the adjacent port of Milwaukee for packaging and shipment to commercial and retail customers in bags ranging from five pounds to one ton.
Located on the western shore of Lake Michigan in the U.S. Midwest, the city of Milwaukee takes its name from a Native American term meaning “gathering place by the water.” A description perfectly in line with the exemplary process implemented in the city for treating and recycling wastewater, eliminating and recovering waste, and reducing the amount of energy consumed by all of these operations.
Developed by the Milwaukee Metropolitan Sewerage District (MMSD) and marketed since 1926, the process produces a pelletized fertilizer recovered from wastewater from the metropolitan area, including the breweries — important for their nutritional content, as it turns out. The resulting product is composed of heat-dried microbes that have digested the nutrients in the wastewater. Known as Milorganite® (for Milwaukee Organic Nitrogen), the product is sold across the
Milorganite®’s production fits with a broad sustainability strategy co-developed between MMSD and its partner Veolia. The twofold aim is to ensure environmental compliance — wastewater recovery, carbon footprint reduction — and develop a range of innovative technical programs. Other strengths have a socially responsible dimension, including successful Small/ Women/Minority Business Enterprise (SWMBE) purchasing programs and utilizing a collaborative process control framework aimed at controlling potential wet-weather overflows.
Brewing up a commercial success
Milorganite® is produced at a rate of approximately 48,000 metric tons per year. Sales, which have been steadily increasing (topping $10 million in 2017), benefit from a special ingredient according to MMSD Executive Director, Kevin Shafer. “Other cities are producing similar fertilizers but our quality is higher due to good BOD (biological oxygen demand) content that comes from the brewery streams.”
The excellence of the MMSD-Veolia partnership has been recognized through multiple prestigious honors, including: U.S. Water Prize from the Clean Water Alliance; Platinum Awards from the National Association of Clean Water Agencies; Distinguished Service Award from the National Council for Public-Private Partnerships. In addition, the Jones Island facility consistently ranks as one of Historic Milwaukee’s most popular “Doors Open” tour attractions, drawing more than 4,000 visitors in 2017. In 2016, MMSD awarded Veolia a 10-year contract extension, two years ahead of schedule, based on its performance. Scott Royer, VP and General Manager of the project for Veolia, attributes this success to the Group’s sustainability commitment. “With MMSD’s vision to achieve 80% renewable energy for their wastewater treatment operations and Veolia’s long-standing commitment to recycling, we know that this is a winwin partnership.”
Sales of Milorganite® are mainly for golf courses, green spaces and retail sales. Its appeal, says Kevin Shafer, is that “Milorganite® is from a natural source so it dissolves more slowly and soaks into the ground more efficiently than synthetic fertilizers produced from mined phosphorous – which is also a finite resource.”
In 2008, MMSD entered into a public-private partnership with Veolia. Under the contract, which was renewed in 2016, the Group operates and maintains the city’s two water reclamation facilities, Jones Island and South Shore, a 320-mile collection system, biosolids production and a “Deep Tunnel” sewage sludge storage system.
Early in the partnership, Veolia approached MMSD with a proposal to reduce the amount of energy consumed at Jones Island by utilizing biogas. This gas comes from the anaerobic digestion of waste from a landfill operated by Veolia 17 miles away, with the methane recovered being piped in. Completed in 2017, the project has halved the amount of natural gas consumed on the site, saving 1.5 million dekatherms per year. A new biogas plant is set to open soon, increasing the proportion of operations powered by biogas to almost 85%.
“Veolia’s energy recovery idea enabled us to reduce fossil fuel usage, reduce our carbon footprint and save money for our ratepayers,” says Kevin Shafer. “They’ve truly provided added value and been a good partner for us and the city of Milwaukee.”
- 1.1 million people benefit from wastewater services in 28 municipalities
- Operation and maintenance of a 320-mile system of interceptor and main sewers
- Two wastewater treatment facilities with a combined peak capacity of 630 million gallons
- Management of a 28-mile-long, 521-million-gallon Deep Tunnel storage system
- 3,000 miles of household laterals and 3,000 miles of sanitary sewers
- Annual production of 48,000 metric tons of MMSD’s renowned Milorganite® biosolids fertilizer
- 2017 Milorganite® sales > $10 million
- 1.5 million dekatherms of energy saved annually