addressing uncertainty in oil and natural gas industry greenhouse

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EXHIBIT 4-2: Uncertainty Example for Fugitive Emissions Estimation, continued o Table 4-4 gives the methane emissions for the individual components and their uncertainties along with the total methane emissions and its uncertainty. The 95% confidence interval bounds for the total methane emissions is shown as (7.41, 30.6) tonnes/year. Table 4-4. Estimated Fugitive CH 4 Emission Equipment Type Electric reciprocating compressor Relative Absolute Component Type Service CH 4 Emissions Lower Uncertainty (%) Upper Uncertainty (%) Lower Uncertainty Upper Uncertainty Connectors Gas/Vapor 0.889 36.2 36.2 0.322 0.322 Connectors Light Liquid 0.000350 100 a 135 0.000350 0.000474 Controllers Fuel Gas 0.545 41.4 327 0.226 1.78 Compressor Gas/Vapor 6.53 83.3 83.3 5.44 5.44 Seals Open-ended Gas/Vapor 7.83 85.0 171 6.66 13.4 Lines Valves Gas/Vapor 0.225 22.5 22.5 0.0507 0.0507 Valves Light Liquid 0.00112 79.5 79.5 0.000889 0.000889 TOTAL 16.0 53.7 91.0 8.61 14.6 a This value was truncated (set to -100%) since the emissions cannot be less than 0. 4.3.3 Emission Factor Uncertainty The decision tree presented in Figure 4-3 addresses uncertainty for emission factor data. Uncertainties may be published along with the literature values for emission factors, in which case, the uncertainty from the literature should be used. If the uncertainties associated with literature values are unavailable or data are not available to calculate uncertainty, one must rely on expert judgment to estimate the uncertainty. Expert judgment involves a person, or group of people, familiar with the systems assigning an uncertainty to the estimate based on knowledge of the process. It is used when there is no information to quantify the uncertainty based on data or manufacturer’s specifications of the measured parameter. Expert judgment is covered in Sections 2.2, 3.2.2.3, and Annex 2A.1 of the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC, 2006). Section 7 of the ISO-5168 explains how to deal with uncertainty estimates based on expert judgment (ISO, 2005). Pilot Version, September 2009 4-13
Further guidance for assigning uncertainty values is provided in Section 5 in the context of quantifying uncertainty for the GHG inventory of a hypothetical oil and gas facility. The following example demonstrates uncertainty estimation for a default emission factor. EXHIBIT 4-3: Uncertainty Example for Emission Factors Input Data: o The CO 2 emissions factor for natural gas in production (non-pipeline quality) is 0.0547 tonnes/10 6 Btu (HHV) (from Table 4-2 of the 2009 API Compendium). An estimate of uncertainty for this value is not provided in the original reference, so an uncertainty of 10% at the 95% confidence interval is assumed based on expert judgment. Bias is assumed to be accounted for in this value. o Similarly, the natural gas heating values is 1020 Btu/scf (from Table 3-8 of the 2009 API Compendium). An estimate of uncertainty for this value is not provided in the original reference so an uncertainty of 10% at the 95% confidence interval is assumed based on expert judgment. Bias is assumed to be accounted for in this value. Emission Factor Estimate: o The emission factor is quantified as the product of the carbon content and heating value, as shown by the following formula: 6 Emission Factor Gas Carbon Content Heating Value 10 scf/MMscf × × × 6 (tonnes CO 2/MMscf) (tonnes CO 2/MMBtu) (Btu/scf) 10 Btu/MMBtu Uncertainty Estimate: o For the purpose of this example, the uncertainties associated with the carbon content and heating value are assumed to be independent because the values are cited from different literature references and are not based on measured data. Therefore, Equation 4-6 is applied to estimate the uncertainty for the emission factor. This applies the relative uncertainties for the carbon content and heating value. ⎛U X ⎞ ⎛UY ⎞ U ( Rel) X × Y = ⎜ ⎟ + ⎜ ⎟ ⎝ X ⎠ ⎝ Y ⎠ 2 2 U = + = 2 2 (Rel) Emission Factor 0.10 0.10 0.141 The resulting emission factor is then: 6 0.0547 tonnes CO2 1,020 Btu 10 scf/MMscf 6 Emission Factor = × × MMBtu scf 10 Btu/MMBtu Emission Factor = 55.8 ± 14.1% tonnes CO /MMscf ( ) 2 Pilot Version, September 2009 4-14
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Prepared by the LEVON Group, LLC an
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Table of Contents SECTION Page FORE
Page 5 and 6:
List of Tables SECTION Page 2-1 Ove
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FOREWORD The global oil and natural
Page 9 and 10: DOCUMENT AT A GLANCE This document
Page 11 and 12: 1.0 INTRODUCTION Policymakers use e
Page 13 and 14: The Intergovernmental Panel on Clim
Page 15 and 16: 2.0 SOURCES OF UNCERTAINTY There ar
Page 17 and 18: Table 2-1. Overview of Methods Used
Page 19 and 20: the uncertainty associated with cur
Page 21 and 22: d. Data processing uncertainty Typi
Page 23 and 24: d. Material Balance For some emissi
Page 25 and 26: 3.0 OVERVIEW OF MEASUREMENT PRACTIC
Page 27 and 28: 3.1 Flow Measurement Practices Cont
Page 29 and 30: All these factors should be assesse
Page 31 and 32: Table 3-1. Example of FFMS Combined
Page 33 and 34: 3.2 Uncertainties of Flow Measureme
Page 35 and 36: Table 3-3. Compilation of Specifica
Page 37 and 38: EXHIBIT 3-3: FACTORS TO CONSIDER WH
Page 39 and 40: 3.3.2 Quantifying Sampling Precisio
Page 41 and 42: Table 3-4. Summary of Selected Carb
Page 43 and 44: 3.5 Heat Content Determination The
Page 45 and 46: 3.5.2 Computational Methods Heating
Page 47 and 48: using standard methods, non-standar
Page 49 and 50: 0.6 0.4 0.2 Error 0 -0.2 -0.4 -0.6
Page 51 and 52: s ± t × (Equation 4-1) n where s
Page 53 and 54: 4.2.1 Propagation Equations There a
Page 55 and 56: For two terms that might be correla
Page 57 and 58: EXHIBIT 4-1: Uncertainty Example fo
Page 59: EXHIBIT 4-2: Uncertainty Example fo
Page 63 and 64: 4.4 Quantifying Measurement Uncerta
Page 69 and 70: Are the data based on a single poin
Page 71 and 72: Two methods are compared. The first
Page 73 and 74: . EXHIBIT 4-6: Uncertainty Example
Page 77 and 78: Table 4-13 shows the uncertainty in
Page 79 and 80: Table 4-13. Comparison of Annual Em
Page 81 and 82: • The evolution of activity and e
Page 83 and 84: These guidelines concentrate solely
Page 85 and 86: (Reprinted from the API Compendium)
Page 87 and 88: Table 5-2. Onshore Oil Field (High
Page 89 and 90: associated with them are assigned b
Page 91 and 92: Table 5-4. Onshore Oil Field (High
Page 93 and 94: 5.2.4 Propagating Assymetric Uncert
Page 95 and 96: U( rel) = U( rel) + U( rel) + U( re
Page 97 and 98: Coke burn rate approach (Equation 5
Page 99 and 100: Wt% C ∑ lbmole x lbmole C 12 lb C
Page 101 and 102: The CO 2 emissions are calculated u
Page 103 and 104: GHG Emissions, tonnes/yr 60,000 50,
Page 105 and 106: vast majority of the uncertainty fo
Page 107 and 108: 6.0 REFERENCES AGA, 2008, Greenhous
Page 109 and 110: The Alberta Energy and Utilities Bo
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Appendix A GLOSSARY OF STATISTICAL
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APPENDIX B LIST OF INDUSTRY MEASURE
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Chapter 2.8B Establishment of the L
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Chapter 11.5.3 Chapter 12.1.1 Chapt
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Chapter 19.4 Chapter 20.1 RP 85 RP
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ISO 8222:2002 ISO 8697:1999 ISO 902
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ISO 7194:2008 Measurement of fluid
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ASTM D4292 ASTM D4892 ASTM D5002 AS
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APPENDIX C OPERATING CONDITIONS, IN
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Appendix C OPERATING CONDITIONS, IN
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Appendix D SELECT MEASUREMENT METHO
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c. ASTM UOP539-97, Refinery Gas Ana
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interference between known componen
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maintained over the room temperatur
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APPENDIX E UNITS CONVERSION
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− Gasoline density (average) = 0.
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Appendix F UNCERTAINTY ESTIMATION D
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The uncertainty for the heaters/reb
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∑ 2 U ( abs) = U( abs) ∑(Wt%C)
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Combining the fuel usage for the tw
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Uncertainty Estimate of CO 2 e Emis
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U ( abs) = ( U ( abs) + U ( abs) +
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E E CO2e 219 tonne CO ⎛ 2 0.0108
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E CO 2 6 500× 10 scf gas lbmole ga
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• Fuel Economy (miles per gallon)
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Upper: U ( abs) = (U( abs) +U( abs)
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default CH 4 content is 5.53% from
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Uncertainty Estimate of CO 2 e Emis
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( ) Urel ( ) = Urel ( ) = Urel ( )
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Uncertainty Estimate for CH 4 and C
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specific mole % for CH 4 and CO 2 i
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E CO2 0.07239 tonne CH 4 tonne mole
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U ( rel) = U( rel) +U( rel) +U( rel
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Table F-14. Fugitive Emission and U
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U ( abs) = (U( abs) +U( abs) +U( ab
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Table F-15. Onshore Oil Field (High
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