addressing uncertainty in oil and natural gas industry greenhouse

U ( abs) = ( U ( abs) + U ( abs) + U ( abs)
2 2 2
ECO 2e ECO E
2 CH E
4 N2O
U ( abs) E
= ( − 0.157× 13,900) + ( − 0.294× 21× 0.905) + ( − 1.00× 310×
0.325)
CO2e
Lower:
U ( abs) = 2,190 tonnes CO e/yr
Urel
E
CO2e
( ) 100% 2
ECO 2e
14,100 tonnes CO 2
2
2 2 2
2,190 tonnes CO e/yr
=−15.6% tonnes CO2e/yr
e/yr
= × ( )
Uncertainty Estimate of CH 4 and N 2 O Emissions from Diesel-fired Equipment:
For diesel engines, the emission factor is provided on a heat input basis. The equipment ratings provided in
Table F-5 are converted to volume of fuel consumed on a heat input basis using the conversion factor 8,089
Btu/hp-hr (from API Compendium Table 4-2). An uncertainty of 5% is assumed based on engineering
judgment for this conversion factor.
Diesel engine >600 hp:
-6
1,800 hp 8,089 Btu 200 hr 3.7×
10 tonne CH4
E
CH
= 1 Unit × × × × = 0.0108 tonnes CH
4
6
4
/yr
unit hp-hr yr 10 Btu
-7
1,800 hp 8,089 Btu 200 hr 6.01 × 10 tonne N2O
E
NO
= 1 Unit × × × × = 0.00175 tonnes N
2
6
2O/yr
unit hp-hr yr 10 Btu
As discussed earlier, we assume there is no uncertainty in the number of units, the count of diesel engines.
The uncertainty in the unit capacity is 5%, the uncertainty in the hp-hr to Btu conversion factor is 5%, and
the uncertainty in the average hours of operation is 10% based on expert judgment. The uncertainty in the
emissions factors are determined by engineering judgment to be 25% for CH 4 and +150%, –100% for N 2 O.
The uncertainty of the emissions is calculated by applying Equation 4-6 and using the relative uncertainty
values.
Because it is not possible to have negative emissions, the lower bound uncertainty will be truncated at zero.
As a result, the lower and upper bound uncertainties are estimated separately.
U ( rel) = U(rel) +U( rel) +U( rel) +U( rel) +U( rel)
2 2 2 2 2
emissions NumberOfUnits UnityCapacity Btu/hp-hr conv OperationHours EF
( )
For CH : Urel ( ) = 0 + 5 + 5 + 10 + 25 =± 27.8% tonnes CH /yr
2 2 2 2 2
4 4
Urel
= + + + + =+ , −100%
( tonnes N O/yr)
2 2 2 2 2
For N20 : ( ) 0 5 5 10 150 151%
2
Pilot Version, September 2009 F-11