Monroe WWTP

At a Glance
• System Configuration: 3 × C65 Grid Connect Capstone Biogas Microturbines integrated with central plant controls
• Annual Generation: >1,500 MWh/year of clean, grid-synchronized electricity
• Thermal Recovery: Recovers exhaust heat for anaerobic digester temperature maintenance and building heating
• Long-Term Service Partner: Commissioned in 2014 as part of a $25M plant modernization; serviced and maintained by Veristar Energy since installation


The Challenge
Operating a 3.7 MGD facility serving local residential users and heavy regional dairy and food processing industries, the City of Monroe Wastewater Treatment Plant in Wisconsin faced significant energy demand for continuous pumping, aeration, and processing. The plant's anaerobic digesters produced substantial volumes of methane-rich biogas, which was historically flared off—representing lost energy potential and unnecessary greenhouse gas emissions. The City sought a sustainable, highly reliable solution to convert this by-product gas into useful power while protecting municipal budgets against rising grid power costs.


The Solution
The City of Monroe deployed a 195 kW Biogas Combined Heat & Power (CHP) system featuring three Capstone C65 microturbines, engineered for continuous operation on variable-quality biogas.
• On-Site Biogas Power Generation: Produces over 1,500 MWh of clean electricity annually, offsetting peak utility grid purchases to power critical treatment processes.
• Closed-Loop Digester Heating: Captures microturbine exhaust waste heat to maintain optimal temperatures in the anaerobic digestion system, reducing central boiler fuel usage.
• Flexible Modular Operation: Features a three-shaft modular design that automatically scales power output up or down based on real-time digester biogas production rates.
• Low-Maintenance Fuel Tolerance: Tolerates variable methane content and gas quality with ultra-low emissions and minimal mechanical wear due to air-bearing technology.


The Results
• Substantial Utility Cost Reductions: Delivers predictable, long-term operational savings for the municipal utility by displacing expensive grid electricity.
• Eliminated Biogas Flaring: Transforms a waste by-product into a high-value energy asset, significantly reducing the facility's carbon footprint.
• Industrial Load Stability: Provides smooth, reliable baseload power needed to process heavy organic loading from local food and dairy processing facilities.
• Over a Decade of Continuous Service: Maintained by Veristar since 2014, ensuring maximum system availability and sustained environmental stewardship.