['Air Programs']
['Air Emissions']
06/12/2024
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This section describes how to calculate official emission results for CO 2, CH 4, and N 2 O.
(a) Calculate brake-specific emission rates for each applicable duty cycle as specified in 40 CFR 1065.650. Apply infrequent regeneration adjustment factors as described in §1036.580.
(b) Adjust CO 2 emission rates calculated under paragraph (a) of this section for measured test fuel properties as specified in this paragraph (b). This adjustment is intended to make official emission results independent of differences in test fuels within a fuel type. Use good engineering judgment to develop and apply testing protocols to minimize the impact of variations in test fuels.
(1) Determine your test fuel's mass-specific net energy content, Emfuelmeas, also known as lower heating value, in MJ/kg, expressed to at least three decimal places. Determine Emfuelmeas as follows:
(i) For liquid fuels, determine Emfuelmeas according to ASTM D4809 (incorporated by reference, see §1036.810). Have the sample analyzed by at least three different labs and determine the final value of your test fuel's Emfuelmeas as the median of all the lab test results as described in 40 CFR 1065.602(m). If you have results from three different labs, we recommend you screen them to determine if additional observations are needed. To perform this screening, determine the absolute value of the difference between each lab result and the average of the other two lab results. If the largest of these three resulting absolute value differences is greater than 0.297 MJ/kg, we recommend you obtain additional results prior to determining the final value of Emfuelmeas.
(ii) For gaseous fuels, determine Emfuelmeas according to ASTM D3588 (incorporated by reference, see §1036.810).
(2) Determine your test fuel's carbon mass fraction, wC, as described in 40 CFR 1065.655(d), expressed to at least three decimal places; however, you must measure fuel properties for α and β rather than using the default values specified in 40 CFR 1065.655(e).
(i) For liquid fuels, have the sample analyzed by at least three different labs, determine wC for each result as described in 40 CFR 1065.655(d), and determine the final value of your test fuel's wC as the median (as described in 40 CFR 1065.602(m)) of all the wC values. If you have results from three different labs, we recommend you screen them to determine if additional observations are needed. To perform this screening, determine the absolute value of the difference between each wC value and the average of the other two wC values. If the largest of these three resulting absolute value differences is greater than 1.56 percent carbon, we recommend you obtain additional results prior to determining the final value of wC.
(ii) For gaseous fuels, have the sample analyzed by a single lab and use that result as your test fuel's wC.
(3) If, over a period of time, you receive multiple fuel deliveries from a single stock batch of test fuel, you may use constant values for mass-specific energy content and carbon mass fraction, consistent with good engineering judgment. To use these constant values, you must demonstrate that every subsequent delivery comes from the same stock batch and that the fuel has not been contaminated.
(4) Correct measured CO 2 emission rates as follows:
Where:
eCO2 = the calculated CO 2 emission result.
Emfuelmeas = the mass-specific net energy content of the test fuel as determined in paragraph (b)(1) of this section. Note that dividing this value by wCmeas (as is done in this equation) equates to a carbon-specific net energy content having the same units as EmfuelCref.
EmfuelCref = the reference value of carbon-mass-specific net energy content for the appropriate fuel type, as determined in Table 1 in this section.
wCmeas = 0.870 kgC/kg
Example:
eCO2 = 630.0 g/hp·hr
Emfuelmeas = 42.528 MJ/kg
EmfuelCref = 49.3112 MJ/kgC
wCmeas = 0.870
eCO2cor = 624.5 g/hp·hr
| Fuel type a | Reference fuel carbon-mass-specific net energy content, EmfuelCref (MJ/kgC) b | Reference fuel carbon mass fraction, wCrefb |
|---|---|---|
| Diesel fuel | 49.3112 | 0.874 |
| Gasoline | 50.4742 | 0.846 |
| Natural gas | 66.2910 | 0.750 |
| LPG | 56.5218 | 0.820 |
| Dimethyl ether | 55.3886 | 0.521 |
| High-level ethanol-gasoline blends | 50.3211 | 0.576 |
| a For fuels that are not listed, you must ask us to approve reference fuel properties. | ||
| b For multi-fuel streams, such as natural gas with diesel fuel pilot injection, use good engineering judgment to determine blended values for EmfuelCref and wCref using the values in this table. | ||
(c) Your official emission result for each pollutant equals your calculated brake-specific emission rate multiplied by all applicable adjustment factors, other than the deterioration factor.
[88 FR 4487, Jan. 24, 2023; 89 FR 29763, Apr. 22, 2024]
['Air Programs']
['Air Emissions']