Section 98.43 - Calculating GHG emissions(a) Except as provided in paragraph (b) of this section, continue to monitor and report CO2 mass emissions as required under § 75.13 or section 2.3 of appendix G to 40 CFR part 75, and § 75.64 . Calculate CO2, CH4, and N2O emissions as follows: (1) Convert the cumulative annual CO2 mass emissions reported in the fourth quarter electronic data report required under § 75.64 from units of short tons to metric tons. To convert tons to metric tons, divide by 1.1023.(2) Calculate and report annual CH4 and N2O mass emissions under this subpart by following the applicable method specified in § 98.33(c) .(b) Calculate and report biogenic CO2 emissions under this subpart by following the applicable methods specified in § 98.33(e) . The CO2 emissions (excluding biogenic CO2) for units subject to this subpart that are reported under §§ 98.3(c)(4)(i) and (c)(4)(iii)(B) shall be calculated by subtracting the biogenic CO2 mass emissions calculated according to § 98.33(e) from the cumulative annual CO2 mass emissions from paragraph (a)(1) of this section. Separate calculation and reporting of biogenic CO2 emissions is optional only for the 2010 reporting year pursuant to § 98.3(c)(12) and required every year thereafter. 75 FR 79155 , Dec. 17, 2010