---
kind: "section"
citation: "40 C.F.R. § 98.73"
title: "40"
number: "98.73"
heading: "Calculating GHG emissions."
url: "https://uscodex.org/cfr/40/98.73"
---

# §98.73. Calculating GHG emissions.


You must calculate and report the annual CO2 process emissions from each ammonia manufacturing unit using the procedures in either paragraph [(a)](#a) or [(b)](#b) of this section.

- (a) Calculate and report under this subpart the process CO2 emissions by operating and maintaining CEMS according to the Tier 4 Calculation Methodology specified in [§ 98.33(a)(4)](/cfr/40/98.33.md?p=a-4) and all associated requirements for Tier 4 in [subpart C](/cfr/40/subpartC.md) of this part (General Stationary Fuel Combustion Sources).
- (b) Calculate and report under this subpart process CO2 emissions using the procedures in [paragraphs (b)(1) through (4)](#b-1..b-4) of this section, as applicable.
  - (1) **Gaseous feedstock.** You must calculate, from each ammonia manufacturing unit, the CO2 process emissions from gaseous feedstock according to equation G-1 to this section:
  - (2) **Liquid feedstock.** You must calculate, from each ammonia manufacturing unit, the CO2 process emissions from liquid feedstock according to equation G-2 to this section:
  - (3) **Solid feedstock.** You must calculate, from each ammonia manufacturing unit, the CO2 process emissions from solid feedstock according to equation G-3 to this section:
  - (4) **CO—** 2process emissions. You must calculate the annual CO2 process emissions at each ammonia manufacturing unit according to equation G-4 to this section:
- (c) If GHG emissions from an ammonia manufacturing unit are vented through the same stack as any combustion unit or process equipment that reports CO2 emissions using a CEMS that complies with the Tier 4 Calculation Methodology in [subpart C](/cfr/40/subpartC.md) of this part (General Stationary Fuel Combustion Sources), then the calculation methodology in [paragraph (b)](#b) of this section shall not be used to calculate process emissions. The owner or operator shall report under this subpart the combined stack emissions according to the Tier 4 Calculation Methodology in [§ 98.33(a)(4)](/cfr/40/98.33.md?p=a-4) and all associated requirements for Tier 4 in [subpart C](/cfr/40/subpartC.md) of this part.

## Notes

### Amendments

[74 FR 56374, Oct. 30, 2009, as amended at 75 FR 79156, Dec. 17, 2010; 89 FR 31904, Apr. 25, 2024]

### Authority

Authority: 42 U.S.C. 7401-7671q.

### Source

Source: 74 FR 56374, Oct. 30, 2009, unless otherwise noted.

### Amendments

[74 FR 56374, Oct. 30, 2009, as amended at 75 FR 79156, Dec. 17, 2010; 89 FR 31904, Apr. 25, 2024]