addressing uncertainty in oil and natural gas industry greenhouse

goes on to discuss data considerations when collecting information on activity levels and applicable GHG
emissions. It includes an overview of measurement practices that would result in high quality data when
properly implemented, while focusing on measurements that are applicable to the key contributing
sources, i.e. carbon dioxide (CO 2 ) emissions from combustion devices. Topics discussed include: flow
measurement practices; uncertainties of flow measurements for GHG inventories; uncertainty of sampling
and analysis for GHG estimation; and laboratory management systems.
Section 4.0 provides calculation methods for quantifying GHG inventory uncertainty. It addresses the
statistical characterization of measurement uncertainty, and the uncertainty associated with published
emission factors, and concludes by providing specific statistical methods and industry relevant examples
for the propagation of uncertainty. This section links the statistical concepts introduced in earlier sections
to their application for measurement uncertainty and error propagation. Decision trees are provided to
guide the user through the steps needed to quantify uncertainty for each part of a GHG inventory.
Section 5.0 takes the guidelines, procedures, and equations for calculation of uncertainty that were
outlined in Section 4 and applies them to a hypothetical facility to demonstrate how to calculate total
uncertainty for a facility-level GHG inventory. The statistical approaches discussed previously are also
applied to two select refinery operations to examine and compare uncertainty estimates for different
emission estimation methods. The hypothetical example facilities and operations are taken directly from
the 2009 API Compendium containing details of how the inventory was generated or calculated. This
section also provides a detailed analysis of the resulting inventory data and its uncertainty in the context
of improving GHG data quality and reducing uncertainty.
Detailed technical information is organized in six appendices, as follows:
Appendix A – Glossary of statistical and GHG inventory terms;
Appendix B – A comprehensive list of applicable industry measurement standards;
Appendix C - Operating conditions, inspection, calibration and manufacturers’ reported measurement
errors for common flow meters;
Appendix D – Measurement method summaries for carbon content measurement methods, and heating
value measurement methods;
Appendix E – Unit conversions including energy units, common units of measure for fossil fuel heating
content values, and carbon content of selected fuels; and
Appendix F – Calculation details for uncertainty estimation for an example GHG inventory.
Pilot Version, September 2009
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