A greenhouse gas source of surprising significance: anthropogenic CO2 emissions from use of methanol in sewage treatment

Methanol9s (CH 3 OH) impact as a source of anthropogenic carbon dioxide (CO 2 ) in denitrification at wastewater treatment plants (WWTPs) has never been quantified. CH 3 OH is the most commonly purchased carbon source for sewage denitrification. Until recently, greenhouse gas (GHG) reporting protocols consistently ignored the liberation of anthropogenic carbon dioxide (CO 2 ) attributable to CH 3 OH. This oversight can likely be attributed to a simplifying notion that CO 2 produced through activated-sludge-process respiration is biogenic because most raw-sewage carbon is un-sequestered prior to entering a WWTP. Instead, a biogenic categorization cannot apply to fossil-fuel-derived carbon sources like CH 3 OH. This paper provides a summary of how CH 3 OH use at DC Water9s Blue Plains Advanced Wastewater Treatment Plant (AWTP; Washington, DC) amounts to 60 to 85% of the AWTP9s Scope-1 emissions. United States Environmental Protection Agency and Water Environment Federation databases suggest that CH 3 OH CO 2 likely represents one quarter of all Scope-1 GHG emissions attributable to sewage treatment in the U.S. Finally, many alternatives to CH 3 OH use exist and are discussed.