SUMMARY: The Draft Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2017 is available for public review. EPA requests recommendations for improving the overall quality of the inventory report to be finalized in April 2019, as well as subsequent inventory reports.

DATES: To ensure your comments are considered for the final version of the document, please submit your comments by March 14, 2019. However, comments received after that date will still be welcomed and considered for the next edition of this report.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2018-0853, to the Federal eRulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting comments.

SUPPLEMENTARY INFORMATION: Annual U.S. emissions for the period of time from 1990 through 2017 are summarized and presented by sector, including source and sink categories. The inventory contains estimates of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3) emissions. The technical approach used in this report to estimate emissions and sinks for greenhouse gases is consistent with the methodologies recommended by the Intergovernmental Panel on Climate Change (IPCC), and reported in a format consistent with the United Nations Framework Convention on Climate Change (UNFCCC) reporting guidelines. The Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2017 is the latest in a series of annual, policy-neutral U.S. submissions to the Secretariat of the UNFCCC. EPA requests recommendations for improving the overall quality of the inventory report to be finalized in April 2019, as well as subsequent inventory reports.

Excerpts:

Greenhouse gases that are used in manufacturing processesor by end-consumers include man-made compounds such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF₆), and nitrogen trifluoride (NF₃). The present contribution of HFCs, PFCs, SF₆, and NF₃ gases to the radiative forcing effect of all anthropogenic greenhouse gases is small; however, because of their extremely long lifetimes, many of them will continue to accumulate in the atmosphere as long as emissions continue. In addition, many of these gases have high global warming potentials; SF₆ is the most potent greenhouse gas the Intergovernmental Panel on Climate Change (IPCC) has evaluated.

Use of HFCs is growing rapidly since they are the primary substitutes for ozone depleting substances (ODS), which are being phased-out under the Montreal Protocol on Substances that Deplete the Ozone Layer (our emphasis).

Hydrofluorocarbons, PFCs, SF₆, and NF₃ are employed and emitted by a number of other industrial sources in the United States, such as semiconductor manufacture, electric power transmission and distribution, and magnesium metal production and processing…

… Trifluoromethane (HFC-23 or CHF3) is generated as a byproduct during the manufacture of chlorodifluoromethane (HCFC-22), which is primarily employed in refrigeration and air conditioning systems and as a chemical feedstock for manufacturing synthetic polymers. Between 1990 and 2000, U.S. production of HCFC-22 increased significantly as HCFC-22 replaced chlorofluorocarbons (CFCs) in many applications. Between 2000 and 2007, U.S. production fluctuated but generally remained above 1990 levels. In 2008 and 2009, U.S. production declined markedly and has remained near 2009 levels since. Because HCFC-22 depletes stratospheric ozone, its production for non-feedstock 10uses is scheduled to be phased out by 2020 under the U.S. Clean Air Act. Feedstock production, however, is permitted to continue indefinitely.

HCFC-22 is produced by the reaction of chloroform (CHCl3) and hydrogen fluoride (HF) in the presence of a catalyst, SbCl5. The reaction of the catalyst and HF produces SbClxFy, (where x + y = 5), which reacts with chlorinated hydrocarbons to replace chlorine atoms with fluorine. The HF and chloroform are introduced by submerged piping into a continuous-flow reactor that contains the catalyst in a hydrocarbon mixture of chloroform and partially fluorinated intermediates. The vapors leaving the reactor contain HCFC-21 (CHCl2F), HCFC-22 (CHClF2), HFC-23 (CHF3), HCl, chloroform, and HF. The under-fluorinated intermediates (HCFC-21) and chloroform are then condensed and returned to the reactor, along with residual catalyst, to undergo further fluorination. The final vapors leaving the condenser are primarily HCFC-22, HFC-23, HCl and residual HF. The HCl is recovered as a useful byproduct, and the HF is removed. Once separated from HCFC-22, the HFC-23 may be released to the atmosphere, recaptured for use in a limited number of applications, or destroyed.

Two facilities produced HCFC-22 in the United States in 2017. Emissions of HFC-23 from this activity in 2017 were estimated to be 5.2 MMT CO2Eq. (0.3 kt) (see Table 4-50). This quantity represents an 85 percent increase from 2015 emissions and an 89 percent decrease from 1990 emissions.The decrease from 1990 emissions was caused primarily by changes in the HFC-23 emission rate (kg HFC-23 emitted/kg HCFC-22 produced). An uptick in this rate, as well as in the quantity of HCFC-22 produced, was responsible for the increase in HFC-23 emissions between 2016 and 2017. The long-term decrease in the emission rate is primarily attributable to six factors: (a) five plants that did not capture and destroy the HFC-23 generated have ceased production of HCFC-22 since 1990; (b) one plant that captures and destroys the HFC-23 generated began to produce HCFC-22; (c) one plant implemented and documented a process change that reduced the amount of HFC-23 generated; (d) the same plant began recovering HFC-23, primarily for destruction and secondarily for sale; (e) another plant began destroying HFC-23; and (f) the same plant, whose emission factor was higher than that of the other two plants, ceased production of HCFC-22 in 2013.

List of some (not all) of the Tables in the report:

Table ES–1: Global Warming Potentials (100-Year Time Horizon) Used in this Report

Table ES-2: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks (MMT CO₂Eq.)

Table ES-3: CO2Emissions from Fossil Fuel Combustion by End-Use Sector (MMT CO₂Eq.)

Table ES-4: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks by Chapter/IPCC Sector (MMT CO₂Eq.)

Table ES-5: U.S. Greenhouse Gas Emissions and Removals (Net Flux) from Land Use, Land-Use Change, and Forestry (MMT CO₂Eq.)

Table ES-6: U.S. Greenhouse Gas Emissions Allocated to Economic Sectors (MMT CO₂Eq.)

Table ES-7: U.S. Greenhouse Gas Emissions by Economic Sector with Electricity-Related Emissions Distributed (MMT CO₂Eq.)

Table ES-8: Recent Trends in Various U.S. Data (Index 1990 = 100)

Table 1-1: Global Atmospheric Concentration, Rate of Concentration Change, and Atmospheric Lifetime of Selected Greenhouse Gases

Table 1-2: Global Warming Potentials and Atmospheric Lifetimes (Years) Used in this Report

Table 1-3: Comparison of 100-Year GWP values

Table 1-4: Key Categories for the United States (1990-2017)

Table 1-5: Estimated Overall Inventory Quantitative Uncertainty (MMT CO₂Eq. and Percent) –TO BE UPDATED FOR FINAL INVENTORY REPORT

Table 1-6: IPCC Sector Descriptions.

Table 1-7: List of Annexes.

Table 2-1: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks (MMT CO₂Eq.)

Table 2-2:Recent Trends in U.S. Greenhouse Gas Emissions and Sinks (kt)

Table 2-3: Recent Trends in U.S. Greenhouse Gas Emissions and Sinks by Chapter/IPCC Sector (MMT CO₂Eq.)

Table 2-4: Emissions from Energy (MMT CO₂Eq.)

Table 2-5: CO2Emissions from Fossil Fuel Combustion by End-Use Sector (MMT CO₂Eq.)

Table 2-6: Emissions from Industrial Processes and Product Use (MMT CO₂Eq.)

Table 2-7: Emissions from Agriculture (MMT CO₂Eq.)

Table 2-8: U.S. Greenhouse Gas Emissions and Removals (Net Flux) from Land Use, Land-Use Change, and Forestry (MMT CO₂Eq.)

Table 2-9: Emissions from Waste (MMT CO₂Eq.)

Table 2-10: U.S. Greenhouse Gas Emissions Allocated to Economic Sectors (MMT CO₂Eq. and Percent of Total in 2017)

Table 2-11: Electric Power-Related Greenhouse Gas Emissions (MMT CO₂Eq.)

Table 2-12: U.S. Greenhouse Gas Emissions by Economic Sector and Gas with Electricity-Related Emissions Distributed (MMT CO₂Eq.) and Percent of Total in 2017

*See original report at http://fluoridealert.org/wp-content/uploads/epa.greenhouse-gas.inventory.2019.pdf