NACWA Recommends Greenhouse Gas Inventory Refinements

(December 2, 2020) –NACWA submitted comments November 19 on EPA’s Draft Inventory of US Greenhouse Gas Emissions and Sinks:1990-2019 as part of the expert review processThe annual Inventory provides nationwide estimates for greenhouse gas (GHG) emissions for different sectors, including wastewater treatment, and is intended to be used only for informational purposes.

The wastewater treatment category in the Inventory includes publicly owned treatment works (POTWs), septic systems, and industrial wastewater treatment systems. NACWA has reviewed and commented on the POTW emissions estimates in the Inventory since 2007, recommending revisions to characterize the sector’s emissions more accurately.

For first time since NACWA began commenting on it, this year’s Inventory has major changes from the previous year. EPA has made clarifications and minor adjustments in the past, but a new protocol developed by the Intergovernmental Panel on Climate Change (IPCC) for calculating wastewater emissions has resulted in some substantial changes. 

NACWA provided preliminary comments on the expert review draft and will provide further comments and information during the public review period next year.  NACWA pointed out that the new IPCC guidance eliminated the different emissions factors depending on whether treatment plants use nitrification/dentrification processes, and that actual nitrous oxide emissions are very process-specific. NACWA encouraged EPA to reinstate emission factors that account for the use of absence of nitrification/denitrification process, and to develop emission factors that are specific to US utilities whenever possible. 

NACWA will continue its review of the Inventory. Members that would like to participate in the review can contact Cynthia Finley, NACWA’s Director of Regulatory Affairs.