addressing uncertainty in oil and natural gas industry greenhouse

E
100 10 Btu ×
8760 hr
= × ×
hr 10 Btu yr
6
-6
× 1.0 10 tonne CH4
CH4
6
E
= 0.88 tonnes CH / yr
CH4
4
The uncertainty is calculated by applying Equation 4-6 using the relative uncertainty values. The CH 4
emission factor has a “B” quality rating assigned to it. Based on this, an uncertainty of 10% is applied to
the emission factor.
U( rel) = U( rel) + U( rel)
U rel
CH
4
2 2
( )
CH
= 5 + 10 = 11.2%
4
2 2
Heat rate
Emission Factor
The N 2 O emission factor is also taken from API Compendium Table 4-7 for controlled natural gas fired
boilers.
E
E
6
-7
× 9.8×
10 tonne N2O
NO 2
6
100 10 Btu 8760 hr
= × ×
hr 10 Btu yr
= 0.86 tonnes N O / yr
NO 2
2
The uncertainty is calculated by applying Equation 4-6 using the relative uncertainty values. The N 2 O
emission factor has an “E” quality rating assigned to it. Based on this, an uncertainty of 50% is applied to
the emission factor.
U( rel) = U( rel) + U( rel)
U rel
NO
2
2 2
( )
NO= 5 + 50 = 50.2%
2
2 2
Heat rate
Emission Factor
Table 5-5 summarizes the emission and uncertainty estimates for the different FCCU methodologies.
Equation 4-4, using the absolute uncertainty values, is applied where the emission estimates are summed.
Based on the assumptions applied for the FCCU methodologies, the uncertainty associated with each of the
methods provided in the API Compendium is comparable. In all three equations, the aggregated uncertainty is
influenced primarily by the ± 15% uncertainty values assigned to the coke burn rate (used in the first and third
methods) and the blower air capacity (used in the second method).
Pilot Version, September 2009 5-13