Use of Models and Facility-Level Data in Greenhouse Gas Inventories

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Use of Models and Facility-Level Data in Greenhouse Gas Inventories • For source categories with thresholds, a large fraction of the industry may not be subject to reporting. One goal of the GHGRP, after all, was to maximize emissions coverage while minimizing the number of reporters to the program. EPA will need to consider how representative reported data are of national practices? For some industries the fact that only large industries are reporting may not be relevant, as the same practices, fuels, etc., may be used at smaller facilities as well. For other industries, the larger facilities subject to the rule may have vastly different practices and some data obtained from them may not be sufficient for applying to the smaller sources. The availability of plant-level data could address or partially address many of the current challenges associated with Inventory development. Overall, the GHGRP will help improve the national Inventory by: • Directly provide the combustion and process-related emissions for some source categories (e.g. ammonia, cement, aluminum) on an annual basis. • Allowing the United States to better disaggregate national emissions by industry; disaggregate the current stationary combustion estimates by manufacturing sector per reporting guidelines (e.g., iron and steel, nonferrous metals, chemicals, etc.). • Ensuring that the underlying data for certain source categories are gathered following very specific methodologies; methodologies that can subsequently be readily reviewed by review teams. • Enabling the Inventory Agency to develop a relationship with the facilities directly, as opposed to relying on a third party national statistics organization. • Reducing reliance on default emission factors; develop country-specific (or even more refined) emission factors. • Providing substantial supporting information in addition to the GHG emissions data that will enable us to verify emissions reported. • Gather underlying data that can help affirm, or bring into question, previous assumptions used in the Inventory. • Provide an additional data source to conduct quality assurance/quality control checks. • Refine the uncertainty analysis by allowing us to rely more on data and less on expert judgment. Nevertheless, we can already anticipate a number of challenges with incorporating reported GHG emissions information into the national inventory. Some key challenges anticipated include: • Time Series Consistency. Ensuring time series consistency will be a key issue for all source categories, although some will be more difficult than others (e.g., combustion-related emissions information received from facilities using CEMS, petroleum and natural gas systems). Will have to assess source category by source category whether Tier 3 data obtained through the GHGRP is applicable for earlier years. This may be the case where there is minimal penetration of technologies and minimal fuel variability over time. • Comparability. As discussed above, there are only so many ways to quantify emissions from various source categories. Although the uncertainty bands around emissions estimates will narrow as the United States and other countries start implementing higher-tiered and country-specific methods, determining comparability may become more challenging as it may be difficult for inventory reviewers to assess the comparability of methods. • Transparency. There is still uncertainty over how much of the data will be required to be held confidential. EPA is currently undertaking a rulemaking to determine how the data will be handled. Our goal is to make as much available as possible, thereby facilitating transparent review of the data. Nevertheless, some data will inevitably be held as confidential. The extent to which this affects transparency is yet to be determined. In addition, some methods employed by facilities within a given source category may actually result in less verification data reported to EPA, which in turn could introduce challenges with ensuring transparent data presented in the Inventory. Conclusions The United States has an unprecedented opportunity to collect more comprehensive GHG emissions information as a result of the first annual GHG reports submitted by facilities in 2011 under the Greenhouse Gas Reporting Program. One can only imagine all of the ultimate uses of the data generated through this program (e.g., project, corporate, IPCC Expert Meeting Report 116 TFI
Use of Models and Facility-Level Data in Greenhouse Gas Inventories national, and even international level). The United States has only just begun to think about the next steps of how to use these data; although it is certain that one important end-user will be the National Inventory system. It is generally true that Tier 3 data are more accurate and lead to improved emissions estimates. However, incorporation of facility-specific data into national emissions inventories needs to be done in a deliberate manner taking into account the principles of transparency, completeness, consistency, comparability and accuracy, in order to ensure that the national emissions estimates are in fact improved and can be verified as such. As the United States and other countries start incorporating more Tier 3 methods into their national inventories, some key questions for the international community arise, including: 1) What is meant by a Tier 3 method? Are all Tier 3 methods alike? 2) How should Tier 3 methods be presented in the national inventory? 3) Is current IPCC guidance on QA/QC sufficient for Tier 3 methods? How do inventory compilers document facility specific QA/QC activities undertaken? 4) How will the international community assess comparability of Tier 3 methods across Parties? 5) How should uncertainty analyses be conducted where there is variability in methods within a source category? Is the IPCC guidance sufficient to address this? 6) Can Tier 3 methods introduced in 2010 be applied historically? If so, how? Does it depend on the source category? 7) Will confidential business information be more of an issue where inventories are developed using facilityspecific data? One of the great ironies of inventory development is that while higher-tiered methods are desired, it can often be the case that as countries move to higher tiers and develop more country-specific methods more questions arise about the validity of the emissions estimates or the approaches to obtaining the data. These questions about the inventory quality objectives are most certainly valid, but we should not lose site of the fact that collection and use of facility-specific data in the national Inventory presents significant opportunity for countries to improve their national inventory. IPCC Expert Meeting Report 117 TFI
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Use of Models and Facility-Level Data in Greenhouse Gas Inventories

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