Dubuque WRRC

At a Glance
• System Configuration: 1 × C600 Grid Connect Capstone Microturbine with gas conditioning
• Annual Generation: >5.0 Million kWh/year continuous power
• Energy Savings: ~$300,000 / year in reduced utility power and natural gas expenditures
• Thermal Integration: Waste heat recovery loop feeding anaerobic digesters and winter facility space heating
• Emissions Reduction: 5,000,000 lbs/year CO₂ offset; transformed to Renewable Natural Gas (RNG) in 2021


The Challenge
Serving nearly 60,000 residents and processing an average of 7 million gallons of wastewater daily (with design peaks up to 41 MGD), the City of Dubuque’s Water & Resource Recovery Center (WRRC) faced escalating municipal energy costs. Operating infrastructure built in the 1960s and 1970s—including end-of-life fluid bed incinerators—the city launched a $64 million facility transformation in 2013 to shift from burning sludge to anaerobic digestion. To align with Dubuque’s "Green City" principles, leadership required a low-emission, low-vibration generation system capable of turning formerly flared, high-strength biogas into reliable electricity and process heat.


The Solution
Veristar Energy and its partners deployed a 600 kW biogas-powered Combined Heat & Power (CHP) microturbine system paired with advanced gas conditioning technology to maximize energy capture from the facility's anaerobic digesters.
• 70% Onsite Power Self-Sufficiency: Generates over 5,000 MWh of clean electricity annually on-site—equivalent to powering approximately 360 households daily—supplying 70% of the facility’s total electrical demand behind the meter.
• Thermal Heat Loop Offset: Captures high-grade microturbine exhaust heat through integrated heat exchangers to maintain biological temperatures in the anaerobic digesters and heat plant buildings during Iowa winters.
• Ultra-Low Emissions & Low Maintenance: Replaced aging incinerators with air-bearing microturbine technology, delivering ultra-quiet, low-vibration power with minimal routine maintenance compared to traditional internal combustion engines.
• Future-Proof Renewable Transition: Engineered with modular flexibility that enabled a seamless transition in 2021 to support Renewable Natural Gas (RNG) pathways.


The Results
• $300,000 Annual Bottom-Line Savings: Drastically cuts recurring utility electricity purchases and natural gas expenses, reducing operating overhead for local taxpayers.
• 5 Million Lbs/Year CO₂ Reduction: Eliminates significant greenhouse gas emissions, establishing the WRRC as a regional model for sustainable municipal infrastructure.
• 15.5 Tons/Day Land-Applied Fertilizer: Transforms solid waste into 15.5 tons of nutrient-rich agricultural fertilizer daily, completely eliminating waste burning.
• Turnkey Biogas Utilization: Replaces raw gas flaring with a closed-loop energy strategy that captures maximum financial and environmental ROI from high-strength organic streams.