---
kind: "section"
citation: "40 C.F.R. § 98.503"
title: "40"
number: "98.503"
heading: "Calculating GHG emissions."
url: "https://uscodex.org/cfr/40/98.503"
---

# §98.503. Calculating GHG emissions.


You must calculate and report the annual process CO2 emissions from each calcium carbide process unit not subject to [paragraph (c)](#c) of this section using the procedures in either paragraph [(a)](#a) or [(b)](#b) of this section.

- (a) Calculate and report under this subpart the combined process and combustion CO2 emissions by operating and maintaining CEMS 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.
- (b) Calculate and report under this subpart the annual process CO2 emissions from the calcium carbide process unit using the carbon mass balance procedure specified in paragraphs [(b)(1)](#b-1) and [(2)](#b-2) of this section.
  - (1) For each calcium carbide process unit, determine the annual mass of carbon in each carbon-containing input and output material for the calcium carbide process unit and estimate annual process CO2 emissions from the calcium carbide process unit using equation 1 to this [paragraph (b)(1)](#b-1). Carbon-containing input materials include carbon electrodes and carbonaceous reducing agents. If you document that a specific input or output material contributes less than 1 percent of the total carbon into or out of the process, you do not have to include the material in your calculation using equation 1.
  - (2) Determine the combined annual process CO2 emissions from the calcium carbide process units at your facility using equation 2 to this [paragraph (b)(2)](#b-2).
- (c) If all GHG emissions from a calcium carbide process 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, then the calculation methodology in [paragraph (b)](#b) of this section must not be used to calculate process emissions. The owner or operator must 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

### Source

Source: 89 FR 31948, Apr. 25, 2024, unless otherwise noted.

### Authority

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

### Source

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