# 40 CFR Appendix G to Part 75 - Determination of CO2 Emissions

Appendix G to Part 75 - Determination of CO2 Emissions
1. Applicability

The procedures in this appendix may be used to estimate CO2 mass emissions discharged to the atmosphere (in tons/day) as the sum of CO2 emissions from combustion and, if applicable, CO2 emissions from sorbent used in a wet flue gas desulfurization control system, fluidized bed boiler, or other emission controls.

2. Procedures for Estimating CO2 Emissions From Combustion

Use the following procedures to estimate daily CO2 mass emissions from the combustion of fossil fuels. The optional procedure in section 2.3 of this appendix may also be used for an affected gas-fired unit. For an affected unit that combusts any nonfossil fuels (e.g., bark, wood, residue, or refuse), either use a CO2 continuous emission monitoring system or apply to the Administrator for approval of a unit-specific method for determining CO2 emissions.

2.1 Use the following equation to calculate daily CO2 mass emissions (in tons/day) from the combustion of fossil fuels. Where fuel flow is measured in a common pipe header (i.e., a pipe carrying fuel for multiple units), the owner or operator may use the procedures in section 2.1.2 of appendix D of this part for combining or apportioning emissions, except that the term “SO2 mass emissions” is replaced with the term “CO2 mass emissions.”

${W}_{C{O}_{2}}=\frac{\left({\mathrm{MW}}_{C}+{\mathrm{MW}}_{{O}_{2}}\right)×{W}_{c}}{2,000{\phantom{\rule{0ex}{0ex}}\mathrm{MW}}_{C}}\text{(Eq.G-1)}$

Where:
Wco2 = CO2 emitted from combustion, tons/day.
MWc = Molecular weight of carbon (12.0).
MWo2 = Molecular weight of oxygen (32.0)
Wc = Carbon burned, lb/day, determined using fuel sampling and analysis and fuel feed rates.

2.1.1 Collect at least one fuel sample during each week that the unit combusts coal, one sample per each shipment or delivery for oil and diesel fuel, one fuel sample for each delivery for gaseous fuel in lots, one sample per day or per hour (as applicable) for each gaseous fuel that is required to be sampled daily or hourly for gross calorific value under section 2.3.5.6 of appendix D to this part, and one sample per month for each gaseous fuel that is required to be sampled monthly for gross calorific value under section 2.3.4.1 or 2.3.4.2 of appendix D to this part. Collect coal samples from a location in the fuel handling system that provides a sample representative of the fuel bunkered or consumed during the week.

2.1.2 Determine the carbon content of each fuel sample using one of the following methods: ASTM D3178-89 (Reapproved 2002) or ASTM D5373-02 (Reapproved 2007) for coal; ASTM D5291-02, Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants, ultimate analysis of oil, or computations based upon ASTM D3238-95 (Reapproved 2000) and either ASTM D2502-92 (Reapproved 1996) or ASTM D2503-92 (Reapproved 1997) for oil; and computations based on ASTM D1945-96 (Reapproved 2001) or ASTM D1946-90 (Reapproved 2006) for gas (all incorporated by reference under § 75.6 of this part).

2.1.3 Use daily fuel feed rates from company records for all fuels and the carbon content of the most recent fuel sample under this section to determine tons of carbon per day from combustion of each fuel. (All ASTM methods are incorporated by reference under § 75.6.) Where more than one fuel is combusted during a calendar day, calculate total tons of carbon for the day from all fuels.

2.2 For an affected coal-fired unit, the estimate of daily CO2 mass emissions given by equation G-1 may be adjusted to account for carbon retained in the ash using the procedures in either section 2.2.1 through 2.2.3 or section 2.2.4 of this appendix.

2.2.1 Determine the ash content of the weekly sample of coal using ASTM D3174-00, “Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal” (incorporated by reference under § 75.6 of this part).

2.2.2 Sample and analyze the carbon content of the fly-ash according to ASTM D5373-02 (Reapproved 2007), Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Laboratory Samples of Coal and Coke” (incorporated by reference under § 75.6 of this part).

2.2.3 Discount the estimate of daily CO2 mass emissions from the combustion of coal given by equation G-1 by the percent carbon retained in the ash using the following equation:

${W}_{\mathrm{NCO}2}={W}_{\mathrm{CO}2}-\left(\frac{{\mathrm{MW}}_{\mathrm{CO}2}}{{\mathrm{MW}}_{c}}\right)\left(\frac{A%}{100}\right)\left(\frac{C%}{100}\right){W}_{\mathrm{COAL}}$

(Eq. G-2)
where,
WNCO2 = Net CO2 mass emissions discharged to the atmosphere, tons/day.
WCO2 = Daily CO2 mass emissions calculated by equation G-1, tons/day.
MWC02 = Molecular weight of carbon dioxide (44.0).
MWc = Molecular weight of carbon (12.0).
A% = Ash content of the coal sample, percent by weight.
C% = Carbon content of ash, percent by weight.
WCOAL = Feed rate of coal from company records, tons/day.

2.2.4 The daily CO2 mass emissions from combusting coal may be adjusted to account for carbon retained in the ash using the following equation:

WNCO2 = .99 WCO2
(Eq. G-3)
where,
WNCO2 = Net CO2 mass emissions from the combustion of coal discharged to the atmosphere, tons/day.
.99 = Average fraction of coal converted into CO2 upon combustion.
WCO2 = Daily CO2 mass emissions from the combustion of coal calculated by equation G-1, tons/day.

2.3 In lieu of using the procedures, methods, and equations in section 2.1 of this appendix, the owner or operator of an affected gas-fired or oil-fired unit (as defined under § 72.2 of this chapter) may use the following equation and records of hourly heat input to estimate hourly CO2 mass emissions (in tons).

${W}_{C{O}_{2}}=\left(\frac{{F}_{C}×H×{U}_{f}×{\mathrm{MW}}_{{\mathrm{CO}}_{2}}}{2000}\right)\phantom{\rule{0ex}{0ex}}\text{(Eq. G-4)}$

(Eq. G-4)
Where:
WCO2 = CO2 emitted from combustion, tons/hr.
MW CO2 = Molecular weight of carbon dioxide, 44.0 lb/lb-mole.
Fc = Carbon based F-factor, 1040 scf/mmBtu for natural gas; 1,420 scf/mmBtu for crude, residual, or distillate oil; and calculated according to the procedures in section 3.3.5 of appendix F to this part for other gaseous fuels.
H = Hourly heat input in mmBtu, as calculated using the procedures in section 5 of appendix F of this part.
Uf = 1/385 scf CO2/lb-mole at 14.7 psia and 68 °F.
3. Procedures for Estimating CO2 Emissions From Sorbent

When the affected unit has a wet flue gas desulfurization system, is a fluidized bed boiler, or uses other emission controls with sorbent injection, use either a CO2 continuous emission monitoring system or an O2 monitor and a flow monitor, or use the procedures, methods, and equations in sections 3.1 through 3.2 of this appendix to determine daily CO2 mass emissions from the sorbent (in tons).

3.1 When limestone is the sorbent material, use the equations and procedures in either section 3.1.1 or 3.1.2 of this appendix.

3.1.1 Use the following equation to estimate daily CO2 mass emissions from sorbent (in tons).

${SE}_{{\mathrm{CO}}_{2}}={W}_{{\mathrm{CaCO}}_{3}}-\left(\frac{{\mathrm{MW}}_{{\mathrm{CO}}_{2}}}{{\mathrm{MW}}_{{\mathrm{CaCO}}_{3}}}\right)$

(Eq. G-5)
where,
SECO2 = CO2 emitted from sorbent, tons/day.
WCaCO3 = CaCO3 used, tons/day.
Fu = 1.00, the calcium to sulfur stoichiometric ratio.
MWCO2 = Molecular weight of carbon dioxide (44).
MWCaCO3 = Molecular weight of calcium carbonate (100).

3.1.2 In lieu of using Equation G-5, any owner or operator who operates and maintains a certified SO2-diluent continuous emission monitoring system (consisting of an SO2 pollutant concentration monitor and an O2 or CO2 diluent gas monitor), for measuring and recording SO2 emission rate (in lb/mmBtu) at the outlet to the emission controls and who uses the applicable procedures, methods, and equations such as those in EPA Method 19 in appendix A to part 60 of this chapter to estimate the SO2 emissions removal efficiency of the emission controls, may use the following equations to estimate daily CO2 mass emissions from sorbent (in tons).

${SE}_{{\mathrm{CO}}_{2}}={F}_{u}\phantom{\rule{0ex}{0ex}}\frac{{W}_{{\mathrm{SO}}_{2}}}{2000}\frac{{\mathrm{MW}}_{{\mathrm{CO}}_{2}}}{{\mathrm{MW}}_{{\mathrm{SO}}_{2}}}$

(Eq. G-6)
where,
SECO2 = CO2 emitted from sorbent, tons/day.
MWCO2 = Molecular weight of carbon dioxide (44).
MWSO2 = Molecular weight of sulfur dioxide (64).
WSO2 = Sulfur dioxide removed, lb/day, as calculated below using Eq. G-7.
Fu = 1.0, the calcium to sulfur stoichiometric ratio.
and

${W}_{S{O}_{2}}={\mathrm{SO}}_{2o}\frac{%R}{\left(100-%R\right)}\phantom{\rule{0ex}{0ex}}\text{(Eq. G-7)}$

(Eq. G-7)
where:
WSO2 = Weight of sulfur dioxide removed, lb/day.
SO20 = SO2 mass emissions monitored at the outlet, lb/day, as calculated using the equations and procedures in section 2 of appendix F of this part.
%R = Overall percentage SO2 emissions removal efficiency, calculated using equations such as those in EPA Method 19 in appendix A to part 60 of this chapter, and using daily instead of annual average emission rates.

3.2 When a sorbent material other than limestone is used, modify the equations, methods, and procedures in section 3.1 of this appendix as follows to estimate daily CO2 mass emissions from sorbent (in tons).

3.2.1 Determine a site-specific value for Fu, defined as the ratio of the number of moles of CO2 released upon capture of one mole of SO2, using methods and procedures satisfactory to the Administrator. Use this value of Fu (instead of 1.0) in either equation G-5 or equation G-6.

3.2.2 When using equation G-5, replace MWCaCO3, the molecular weight of calcium carbonate, with the molecular weight of the sorbent material that participates in the reaction to capture SO2 and that releases CO2, and replace WCaCO3, the amount of calcium carbonate used (in tons/day), with the amount of sorbent material used (in tons/day).

4. Procedures for Estimating Total CO2 Emissions

When the affected unit has a wet flue gas desulfurization system, is a fluidized bed boiler, or uses other emission controls with sorbent injection, use the following equation to obtain total daily CO2 mass emissions (in tons) as the sum of combustion-related emissions and sorbent-related emissions.

Wt = WCO2 + SECO2
(Eq. G-8)
where,
Wt = Estimated total CO2 mass emissions, tons/day.
WCO2 = CO2 emitted from fuel combustion, tons/day.
SECO2 = CO2 emitted from sorbent, tons/day.
5. Missing Data Substitution Procedures for Fuel Analytical Data

Use the following procedures to substitute for missing fuel analytical data used to calculate CO2 mass emissions under this appendix.

5.1-5.1.2 [Reserved]
5.2 Missing Carbon Content Data

Use the following procedures to substitute for missing carbon content data.

5.2.1 In all cases (i.e., for weekly coal samples or composite oil samples from continuous sampling, for oil samples taken from the storage tank after transfer of a new delivery of fuel, for as-delivered samples of oil, diesel fuel, or gaseous fuel delivered in lots, and for gaseous fuel that is supplied by a pipeline and sampled monthly, daily or hourly for gross calorific value) when carbon content data is missing, report the appropriate default value from Table G-1.

5.2.2 The missing data values in Table G-1 shall be reported whenever the results of a required sample of fuel carbon content are either missing or invalid. The substitute data value shall be used until the next valid carbon content sample is obtained.

5.3 Gross Calorific Value Data

For a gas-fired unit using the procedures of section 2.3 of this appendix to determine CO2 emissions, substitute for missing gross calorific value data used to calculate heat input by following the missing data procedures for gross calorific value in section 2.4 of appendix D to this part.

[58 FR 3701, Jan. 11, 1993, as amended at 60 FR 26556, May 17, 1995; 61 FR 25585, May 22, 1996; 64 FR 28671, May 26, 1999; 67 FR 40475, June 12, 2002; 67 FR 57274, Sept. 9, 2002; 73 FR 4376, Jan. 24, 2008]