(620d) Air Emission Reduction Benefits of Biogas Electricity Generation at Municipal Wastewater Treatment Plants

Municipal wastewater treatment is an energy and materially intensive process. Generating the electricity and manufacturing the chemicals that are used for these processes leads to criteria air pollutants (e.g. NO_x, SO₂, PM_2.5, and volatile organic compounds) and greenhouse gas emissions (e.g. CO₂, CH₄, and N₂O). In this talk, we quantify the implications of these criteria air pollutants and greenhouse gas emissions resulting from energy consumption, chemical use, and direct pollutant release at publicly operated treatment works (POTWs) across the United States. We also assess the potential to reduce air emission damages by generating electricity and heat resulting from upgrading POTWs through the installation of biogas produced during anaerobic sludge digestion. We find that the embedded and on-site health, environmental, and climate (HEC) damages from air emissions are on the order of $1.63 billion. The overwhelming majority of these damages are associated with electricity consumption. Retrofitting all existing POTWs with anaerobic sludge digestion and biogas-fueled heat and electricity can reduce the HEC damages from POTWs by 25%. This work emphasizes the need to account for use-phase embedded air emissions and use spatially resolved marginal damages in evaluating sustainable infrastructure systems.