South Burlington WWTP

At a Glance
• System Configuration: 1 × C65 Grid Connect Capstone Biogas Microturbine with gas conditioning
• Annual Generation: >500 MWh/year of clean, grid-synchronized electricity (enough to power ~83 local homes)
• Thermal Output: 430,000 BTU/hr of recovered hot water for anaerobic digester and facility heating
• Financial Impact: $50,000 / year in annual energy cost reductions
• Long-Term Service Partner: Commissioned in 2012 as part of a $28M facility upgrade; maintained and serviced by Veristar Energy since 2014


The Challenge
Treating 3.25 million gallons of wastewater per day (MGD) for the City of South Burlington and surrounding communities, the Grade 5 Airport Parkway Water Quality Facility underwent a major upgrade to Biological Nutrient Removal (BNR) and 2-PAD anaerobic digestion. The advanced digestion process produced high volumes of methane gas. To protect Lake Champlain, achieve Class A biosolids standards, and manage municipal utility budgets, South Burlington needed a clean, efficient distributed generation system to convert its by-product biogas into useful power and heat without relying on fossil fuel boilers.


The Solution
The City of South Burlington installed a 65 kW Combined Heat & Power (CHP) system featuring a Capstone C65 biogas microturbine paired with Unison Solutions gas conditioning equipment, serviced continuously by Veristar since 2014.
• Renewable Power Generation: Converts by-product digester methane into over 500 MWh of clean electricity annually, directly offsetting grid power demand across the treatment complex.
• Digester Thermal Recovery: Captures 430,000 BTU/hr of high-grade exhaust waste heat to maintain optimal thermophilic (135°F) and mesophilic (95°F) temperatures in the 2-PAD digestion process.
• Displaced Boiler Burn: Fulfils core process heating loads using recovered exhaust energy, drastically reducing secondary natural gas boiler use.
• Low-Maintenance Biogas Reliability: Utilizes oil-free air-bearing technology with a single moving part, delivering quiet, low-emission power from variable-quality biogas.


The Results
• $50,000 Annual Utility Savings: Significantly lowers municipal treatment plant operating overhead, delivering recurring cost avoidance for South Burlington taxpayers.
• Closed-Loop Sustainability: Converts municipal wastewater sludge into renewable power and heat, supporting Class A biosolids production and protecting the Winooski River watershed.
• Offset Fossil Fuel Consumption: Maximize digester methane utilization to minimize greenhouse gas emissions and boiler gas burn.
• Proven Long-Term Asset: Serviced continuously by Veristar since 2014, ensuring high system availability and sustained thermal energy capture.