Appendix E Calculation Methods Appendix

Appendix E
Calculation Methods Appendix $-$ Part II.C.3.a

II.C.3.a Facility-Wide Fuel Combustion Emissions for GHGRP Reporters with CEMS Units

The EPA GHGRP’s Subpart C data are available as fuel-specific and unit-specific emissions values for almost all the GHGRP-reporting U.S. steel and aluminum producers in the Commission’s survey population. However, a few U.S. steel and aluminum producers have some fuel combustion emissions in Subpart C or D that are measured using a continuous emissions monitoring system (CEMS).529F[526] Unlike the rest of the subpart C and D emissions data, the CO₂ emissions from CEMS units are not separated out by fuel type.530F[527] When the CEMS unit combusted a single fuel type, all the CEMS unit emissions were allocated to that fuel type (equation E.14). When the unit used multiple fuels, the Commission used public data from the GHGRP on the annual heat input from natural gas ( $C E M S h e a t_{n a t g a s}$ ) and the GHGRP’s direct CO₂ emissions factor for natural gas ( $C O_{2} E F_{n a t g a s}$ ) to estimate the unit’s CO₂ emissions from natural gas combustion.531F[528] Equation E.15 subtracts this natural gas emissions value from the CEMS unit’s total CO₂ emissions ( $C E M S C O_{2}$ ) and assigns the remainder to the other fuel type used. These CEMS-specific emissions are combined with any Tier 1, 2, and 3 data from the facility for each fuel type ( $f a c i l i t y T 1 G H G_{f u e l}, f a c i l i t y T 2 G H G_{f u e l}, f a c i l i t y T 3 G H G_{f u e l}$ ) as well as the fuel-specific CH₄ ( $f a c i l i t y T 4 C H_{4}_{f u e l}$ ) and N₂O emissions ( $f a c i l i t y T 4 N_{2} O_{f u e l}$ ) from the CEMS unit. This results in facility-wide, fuel-specific totals.

$\begin{matrix} f a c i l i t y G H G_{n a t g a s} = f a c i l i t y T 1 G H G_{n a t g a s} + f a c i l i t y T 2 G H G_{n a t g a s} + f a c i l i t y T 3 G H G_{n a t g a s} \\ + (C E M S h e a t_{n a t g a s} * C O_{2} E F_{n a t g a s}) + f a c i l i t y T 4 C H_{4}_{n a t g a s} + f a c i l i t y T 4 N_{2} O_{n a t g a s} (E .14) \end{matrix}$

$\begin{matrix} f a c i l i t y G H G_{o t h e r f u e l} = f a c i l i t y T 1 G H G_{o t h e r f u e l} + f a c i l i t y T 2 G H G_{o t h e r f u e l} \\ + f a c i l i t y T 3 G H G_{o t h e r f u e l} + C E M S C O_{2} - (C E M S h e a t_{n a t g a s} * C O_{2} E F_{n a t g a s}) \\ + f a c i l i t y T 4 C H_{4}_{n a t g a s} + f a c i l i t y T 4 N_{2} O_{n a t g a s} (E .15) \end{matrix}$

[526] Subpart D of the GHGRP is for certain electricity generating units; GHGRP-reporting facilities that use fuel combustion for electricity generation but do not meet subpart D reporting requirements instead report these emissions in subpart C. Only one facility producing covered steel or aluminum products reported subpart D emissions in 2022, and the facility reported all of these emissions using a CEMS unit. These subpart D emissions were included in the scope 1 fuel combustion emission calculations. 40 C.F.R. § 98.30(a), 98.30(b)(5), and 98.42; EPA, “GHGRP, Envirofacts GHG Query Builder,” accessed September 18, 2024.

[527] 40 C.F.R. § 98.36(b)(9).

[528] Table C-1 to Subpart C of Part 98, Title 40; EPA, OAP, “FLIGHT Database, 2022 Greenhouse Gas Emissions from Large Facilities,” Accessed various dates.