| Selected greenhouse gas and air pollutant emissions from municipal wastewater treatment plant energy supply scenarios were quantified and compared. In all scenarios, anaerobic digester biogas-fuelled energy recovery systems were utilized to meet thermal energy and electricity demands. Any demands not met by energy recovery systems were supplied by natural gas-fuelled boilers and the regional power grid. Each of the four scenarios analyzed included one of four energy recovery systems: boilers (the most common scenario), cogeneration internal combustion engines, cogeneration microturbines, or cogeneration phosphoric acid fuel cells.; All of the cogeneration scenarios when compared to the Boiler Scenario lowered facility greenhouse gas emissions by more than 40% and sulphur dioxide emissions by more than 50%. In addition, the Fuel Cell Scenario lowered nitrogen oxide, carbon monoxide, and total particulate matter emissions by more than 50%. For the Internal Combustion Engine Scenario, nitrogen oxide emissions were 50% greater than the Boiler Scenario. |
