Page 1 of 17 Environmental Protection Agency (EPA) Methane White Paper

Oil and Natural Gas Sector Compressors

INGAA Comments

1. Introduction

The Interstate Natural Gas Associ ation of America (INGAA), a trade association of the interstate natural gas pipeline industry, submits these co mments on the EPA’s technical white paper, “Oil and Natural Gas Sector Compressors” (Compresso r Paper). On April 15, 2014, the EPA released five technical white papers disc ussing potentially significant sour ces of emissions in the oil and natural gas sector. Specifically, the white pa pers focus on potential emissions and mitigation techniques for methane and volatile organic co mpounds (VOCs). INGAA is submitting separate comments on the three papers (Compressors, Le aks and Pneumatics) that address sources applicable to the interstate natural gas transmission and storage (T&S) sector. These comments address the Compressor Paper.

In the Compressor Paper, EPA summarized it s current understanding of vented VOC and methane emissions from this source category, and its understanding of available mitigation techniques and the cost, effectiveness and applic ation of these techniques in the oil and natural gas sector. EPA has requested comment on 12 ques tions related to the c ontents and conclusions of the Compressor Paper.

INGAA and its member companies have a long histor y of working collaboratively with a variety of stakeholders on numerous greenhouse gas (GHG) related issues, including methane quantification and mitigation. As such, INGAA welcomes the opportunity to contribute its knowledge of emissions and available contro l technologies. INGA A commends EPA for involving stakeholders and inviting comment on the methane white papers.

Executive Summary

INGAA has three general points in response to EPA’ s white papers. First, there are significant

differences in the methane emission estimates produced by EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks (the National Invent ory) and the Subpart W portion of its Greenhouse Gas Reporting Program (GHGRP). 1 There also are significant gaps in the information available. EPA needs to develop a systematic program to re concile these differences and fill the gaps in order to support further di scussion on methane reductions . Second, INGAA recommends additional discussion and analysis of the implicat ions, including costs, of potential mitigation methods. Finally, EPA should recognize that new information will be available soon to supplement this discussion.

1 See http://www.epa.gov/ghgreporting/ and http://www.epa.gov/ghgreporting/ reporters/subpart/w.html ( Starting with the 2011 calendar year for Subpar t W, the GHGRP requires pipeline companies to submit annual reports of GHG emissions for subject facilities. Pipelines must submit 2014 emission information for the fourth annual report by March 31, 2015).INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 2 of 17 In response to the Compressor Paper specifi cally, INGAA offers the following comments:

1. EPA should review the data for centrifugal comp ressors. There is a significant disparity in reported emissions between the National Inventory and Subpart W for centrifugal compressors. EPA should resolve this issu e before contemplating mitigation methods. 2. EPA should consider additional mitigation appr oaches for rod packing. Specifically, INGAA recommends condition-based maintenance for rod p acking as an alternative to maintaining or replacing rod packing on a prescribed schedule. 3. Finally, EPA should acknowledge that almost all new compressor units use dry seals and

therefore wet seals as a source of emissions should no longer be a focal point of the

discussion.

INGAA welcomes the opportunity to contribute to this discussion.

Overview of INGAA Responses

INGAA has attempted to answer each question to th e best of its ability. Due to time and other limitations, however, INGAA has not answered all questions fully. For some questions, INGAA could not respond completely because this woul d require a significant long-term effort (e.g., a research program) that includes all stakeholde rs. For example, quest ions regarding technology prevalence, cost implications and technical feasibility impact s would entail an integrated research effort to provide a quality, validated and vetted answ er. In most cases, however, INGAA has provided a thorough response with the in formation available while noting the gaps in existing data. Whenever possible, INGAA offe rs specific examples of field conditions and industry experience. Appendix A provides a quic k reference to EPA’s questions on compressors and INGAA’s response.

2. Establish an Open Process that Involves A ll Stakeholders to Further Examine Methane

Reduction Issues

Other than the Natural Gas STAR program, EPA has focused its oil and gas industry GHG efforts primarily on quantifying or estimating me thane emissions. EPA must consider a number of issues, including economic, opera tions and environmental issues as it moves toward a broader methane strategy.

INGAA envisions a process that is transparent and inclus ive of industry and other stakeholders to examine issues and potential strategies. This ha s proven effective at othe r federal agencies and for other EPA regulations. For example, EPA c ould host technical confer ences similar to those convened by the Federal Energy Re gulatory Commission (FERC) to examine critical issues prior to initiating a rulemaking. 2

2 FERC typically holds public technical conferences to gath er information on important policy issues and to hear potentially competing positions in advance of issuing significant rulemakings. For example, in 2012-2013, FERC

held a series of technical conferences to explore issues surrounding the incr eased use of natural gas for electric power generation and issues that may impede coordination between the gas and electric industries. After considering discussions raised by inte rested stakeholders at the 2012-2013 technical conferences, and subsequent public comments, the FERC initiated two rulemakings that pro pose to address concerns raised by participants at the

technical conferences. Technical conferen ces provide the benefit of educating the regulator and other stakeholders on a particular issue and facilitating a structured dialogue where stakeholders can debate the effectiveness or needINGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 3 of 17 This process would provide an efficient a nd effective means to advance the current understanding of methane emissions and how to de sign effective programs. As an example, the EPA GHGRP is intended to develop improved G HG inventories and to inform policy decisions. 3
Subpart W of the GHGRP addresses T&S segmen t emissions from vents and equipment leaks and companies have submitted three years of data to date. Data is publicly available for the 2011 and 2012 reporting years, 4 and indicate signifi cant differences between Subpart W reporting and the National Inventory 5 for T&S sources. These differences are due in part to differences in scope but also other reasons. It is very important that these differences are understood and that a single, accurate inventory is in place before EPA or industry can develop and implement effective and efficient mitigation strategies. These proposed technical conferences or workshops can provide EPA and industry the platform to discuss these impo rtant issues so that EPA’s future methane reduction polici es reflect all relevant analysis.

3. Sources of Information on Emissions and Reduction Opportunities 6

EPA has requested comment on whether the Comp ressor Paper appropriately characterizes the

different studies and data sources . INGAA agrees that it is im portant to understand the sources of methane emissions, how those emissions are measured and reported, what reduction opportunities exist (and what is the cost associated with th ese opportunities). While the Compressor Paper provides a summary of several sources of information, the paper does not

reflect the full breadth of valuable information av ailable to EPA on the topic. Further, while the studies have been summarized, they are neither co mpared nor contrasted with each other or with

other sources of similar information. It would ha ve been valuable for EPA to provide a tabular summary that presents the primary results from each study in common engineering units in order to identify data gaps and inconsistencies. While it may not have been the intent of the Compressor Paper to compare or contrast informati on, such an exercise is necessary to determine if a particular study appropriately characterizes the data available. Further, a comparison of the studies would help identify conflicts and data gaps in the information.

Due to the limited comment period, I NGAA did not have time to deve lop a definitive analysis of

the various studies listed or a list of key studies that were not included. However, more detailed discussion below provides examples of data gaps or differences in the primary tools that are being used to inform the process (e.g., differe nces between Subpart W reporting and the National Inventory).

In general, INGAA views the Compressor Paper as a summary of some information, but not the full range of studies and data sour ces currently available. EPA’s characterization that the studies

for prospective action prior to the issuance in a propos ed rulemaking. Often techni cal conferences can reveal stakeholder support for certain initiatives, identify potential flaws in certain proposals, and identify alternative ways to address the regulator’s or stakeholders’ concerns.

3 See 40 C.F.R. Part 98 (2014).

4 EPA publishes GHGRP reporting results through its data publication tool, Facility Level Information on GreenHouse gases Tool (FLIGHT); see http://ghgdata.epa.gov/ghgp/main.do

5 Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012 , EPA 430-R-14-003 (April 2014). This report presents the U.S. national GHG inventory from 1990-2012 for anthropogenic sources (i.e., associated with human activity) and is referred to as the “National Inventory” in these comments. The report is updated annually.

6 This section generally responds to Compressor Paper questions 1 and 2.INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 4 of 17 presented in the paper are pivotal suggests that EPA considers them key to understanding these issues. INGAA would caution EPA against placi ng excessive weight on this limited information since other studies, not referenced in the Compre ssor Paper, may be based on the same or similar

data sets but reach different conclusions.

INGAA also urges EPA to elaborate on how it ar rived at its cost analysis for mitigation measures. Cost estimates are sensitive to assump tions and inherent data inconsistencies. Costs vary over time and with locat ion and chosen technology. As presented by EPA, the 2014 study by ICF, Economic Analysis of Methane Emission Re duction Opportunities in the U.S. Onshore Oil and Natural Gas Industries, (ICF paper)

, 7 appears to be the primary source of information on evaluating cost-effective emissions reduction opport unities. However, the ICF paper has several limitations such as only including emissions mitiga tion options for a subset of emission sources, only addressing one mitigation technology or wo rk practice for these select sources (i.e., alternatives are not addressed) , and generally not a ddressing uncertainties or presenting ranges associated with emission mitigation costs and performance. Further, several other sources of

similar information have not been referenced. In fact, cost-effectiveness has been examined by a number of organizations such as the Inte rnational Petroleum Industry Environmental Conservation Association (IPIECA) 8 and the Intergovernmental Panel on Climate Change (IPCC). 9 Cost effectiveness has also been a topic during the United Nations Framework Convention on Climate Change (UNFCCC) events. Given the significance of understanding the

costs associated with various methane reduction technologies in crafting a comprehensive costeffective reduction strategy, the Compressor Pa per should expand the discussion to describe more fully the body of available information, including key parameters and assumptions that impact cost analyses.

Other issues associated with the listed studies have not been fully vetted in the available time for comment. For example, the ICF paper makes assu mptions to refine existing emission factors and update activity data counts and uses very coarse data (e.g., miles of pipe) to change activity data for compressor counts. Such unverified “guess timates” introduce uncertainty across emissions, mitigation and cost discussions is differences between Subpart W data and the National Inventory for T&S sources. Th is is important because differe nces in the inventory affect potential achievable reductions and have implications for economic analysis. The Subpart W and National Inventory differences are discussed further below.

New sources of information soon will become av ailable that will sign ificantly add to the understanding of methane emissions and reduction opportunities in th e T&S sector. Specifically, the Pipeline Research Council International (PRCI) 10 is completing a report summarizing GHG emission reduction technologies and work practices applicab le to natural gas pipeline compressor stations. The PRCI work will id entify existing and commercially available GHG emission reduction technologies and work practices for pipeline compressor stations, as well as

7 Economic Analysis of Methane Emission Reduction Opportunities in the U.S. Onshore Oil and Natural Gas Industries, ICF International, 2014.

8 Oil and Natural Gas Industry Guidelines for Greenhouse Gas Reduction Projects, March 2007.

9 Climate Change 2007, the Fourth A ssessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC).

10 The Pipeline Research Council International (PRCI) is th e global collaborative research development organization of, by, and for the energy pipeline industry.INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 5 of 17 identify technologies in development. The repo rt will evaluate technica l and economic viability of existing and developmental GHG emission reduc tion technologies and work practices. While this report has yet to be released, PRCI has permitted INGAA to acknowledge the draft document for the purposes of our comments. More detail on compressor emissions reduction technologies and costs is provided in comments below.

4. National Estimates of Metha ne Emissions and Methane Emission Factors, Activity Data, and Calculation Methodologies 11

EPA has asked for comment on the national es timates of methane emissions and methane emission factors, activity data, and calculation methodologies. While there are several sources of

information on methane emissions from the natu ral gas system, the two primary sources of GHG emission data are the National Inventory and the EPA GHGRP. The EPA compiles both a topdown estimate of GHG emissions (i.e., National Inventor y activity data uses data such as facility count and miles of pipe to estimate emissi ons) and detailed bottom-up reporting (GHGRP). Using other common vernacular, the National Invent ory is commensurate with a Tier 1 or Tier 2 estimate (i.e., using activity data at the facility or large unit level), whil e Subpart W of the GHGRP uses Tier 3 (more granular source or component level activity data) or Tier 4 (detailed source level data or direct measurement) estimat es. These two reports use different methods for estimating methane releases and do not include all of the same sources of releases. Accordingly, there currently is no single compilation that comprehensively and accurately addresses all sources of methane released by the T&S sector.

While the National Inventory and the GHGRP pr oduce consistent estimated emissions from some sources (e.g., the natural gas production segmen t), there are significant differences for the other segments of the natural gas system. There likely are multiple reasons for the disparity, including differences in the methodologies used in the two programs, an d the specific sources being measured and included for reporting. Fo r example, EPA updated key National Inventory estimates for the production segment based on more recent data, including Subpart W data. In contrast, EPA has not yet updated its key estimate s for the T&S segment, and it does not appear that EPA has compiled or analyzed results base d on thousands of measurements for T&S sources completed in response the GHGRP reporting require ments. INGAA suggests that the approach used for production can also be used to improve the estimates for the T&S sector and to serve as a more accurate basis for determining costs and mitigation opportunities. Work to reconcile these estimates remains an area of needed analysis before drawing any definitive conclusions

about the total level of methane emissions fr om natural gas transmission or definitively addressing related questions about mitigation and costs.

The need for more current data and analysis on methane emission levels is highlighted by the

fact that most T&S emission factors used fo r estimating methane emissions are based on a limited set of data that is approximately two deca des old. The emission factors that are used to

calculate methane emissions for both the Natio nal Inventory Report and for some Subpart W sources have typically been in place since the 1990s and need to be updated. For T&S, the National Inventory (and other pub lished papers and studies) prim arily rely on emission factors

11 This section generally responds to Compressor Paper ques tions 1, 2, 4 (on mitigation technologies, reductions and costs), and 12 (ongoing or planned related studies).INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 6 of 17 derived from an EPA – Gas Re search Institute (GRI) study 12 that was conducted in the early 1990s and published in 1996. These factors may not accurately reflect na tural gas transmission methane emissions because operatin g practices, as well as the effi ciency of operating equipment, have improved over the past 20 years. INGAA urge s EPA to initiate a program to use the T&S data from 2011, 2012 and 2013 GHGRP reporting to support development of improved emission factors, and improved emission estimates for the T&S segments.

The GHGRP also has some limitations, includ ing reliance on dated emission factors and

exclusion of smaller facilities a nd smaller sources at s ubject facilities. Subpart W also does not require reporting of known sources, such as rod packing emissions in “not operatingpressurized” (i.e., standby) mode, and centrif ugal compressor emissions from dry seals. However, analysis of the reported data shoul d significantly improve the understanding of methane emissions from the T&S sector, especi ally where measurement is required. Future improvements in estimates of aggregated methan e emissions, along with use of Subpart W direct measurements to update emission factors, can le ad to more accurate estimates overall. INGAA asks that EPA work with the industry to deve lop emission factors for the sources with new

measurement data available.

Compressor Emission Factors, Activi ty Data and Emission Estimates

As noted above, while the emission studies listed in the Compressor Paper provide a sampling of available information, other valuable sources are available. For example, a number of papers from the late 1990s and early 2000s followed th e publication of the EPA/GRI Report. As another example, in 2005 and 2006, INGAA (along w ith the American Petroleum Institute and American Gas Association) worked with EPA to prioritize data gaps and methane emission factors that required addi tional research. That effort deve loped a plan for a methane “emission factor reconciliation” project 13 and initiated an effort to secu re funding for field tests. The project would have implemented emissions testing pr ojects to address data gaps that remain to this day, based on a prioritized list of emissi on sources collaboratively developed by EPA and the industry stakeholders. However, this projec t was not executed due in large part to EPA’s new responsibility to develop the GHGRP.

A more comprehensive list of reports and emissions-related documents could be compiled, but a higher-priority endeavor might i nvolve a better characterization of the strengths and weaknesses of available documents, identifying data or in formation gaps and defining a programmatic approach for resolving differences. INGAA cannot now provide a comprehensive response because of the limited time provided to respond to the white papers. INGAA believes there is a general need to develop a system atic approach to reconcile diffe rences in available information

because definitive data is not available or has not yet been analyzed (e.g., Subpart W data).

12 Methane Emissions from the Natural Gas Industry, EPA/GRI report (June 1996) at: http://www.epa.gov/gasstar/tools/related.html ; This 15-volume compendium of reports is from an EPA/GRI study published in 1996 that remains a seminal reference on methane releases from natural gas systems. These reports and related data are referred to as the “EPA-GRI Study” in this paper.

13 INGAA/API/AGA Natural Gas Systems GHG Emission Fa ctor Comparison, Gap Assessment, & Improvement Collaborative Project, Executive Summary (May 17, 2006).INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 7 of 17 These comments will illustrate differences in the level of methane emissions by comparing the National Inventory with data fr om the first two years of Subpart W reporting – i.e., 2011 and 2012 annual Subpart W reporting. Although, INGAA has not completed a thorough analysis of Subpart W data, a subset of this information ha s been reviewed. This review indicates that INGAA members have completed over 10,000 direct measurements of compressor emissions in the first two years of Subpart W reporting. Yet, it does not appear that EPA has completed an analysis of Subpart W measurement data. INGAA is working with PRCI on compilation and review of Subpart W data along with supplemen tal data on equipment, operations, and methods used for Subpart W measurements. Initial review indicates that emissi ons for compressors as reported pursuant to Subpart W are significantly lower than the National Inventory estimate of such emissions. EPA should analyze these more recent data. Additional information likely will be available as further analysis is completed, and INGAA will coordi nate with PRCI to share that

information with EPA.

When comparing the data, it is important to understand the different nomenclature used to categorize emissions. For the white papers, INGAA supports the Compressor Paper approach that focuses on vented emissions – e.g., rod pack ing venting from reciprocating compressors. For Subpart W (and emission factors used in th e National Inventory), “compressor” emissions include equipment leaks from unit isolation valves (when uni ts are not operating and depressurized) and blowdown valves (e.g., when units are operating). EPA addresses those emissions in the Leaks White Paper, and that ap pears to be a reasonable approach. However, it is important to understand how emissions are reported and how various vented or leaking

emissions are reflected in estimates. Since ti me was limited to comment, INGAA cannot provide concise analysis on this issue, but there certainly ar e inconsistencies. For example, in the National Inventory and Subpart W estimates disc ussed here, leaks along with compressor vented emissions are grouped and compared. However, when assessing mitigation it is inappropriate to

use the same estimate because the emission rate ma y include rod pack venting (which is covered by the Compressor Paper and would be reduced by rod packing mainte nance) and leaks (e.g., isolation valve leakage when th e unit is shutdown, which should be covered in the Leaks paper and would not be affected by rod packing maintenance).

Additional time would be requi red to segregate National Inventory emissions and Subpart W reported emissions into subsets based on emi ssion source (e.g., rod packing, valve leak) and compressor operating mode. Both inventories pr esent “rolled up” compressor emission estimates that aggregate some leak sources addressed in the Leaks Paper with vents addressed in the Compressor Paper, but the reported data from both programs is similar because certain leaks (e.g., isolation valve) and vented emissions are captured within the estimate for compressors. Since compressor emissions are reported on a sim ilar basis, comparison is appropriate. Other than the emissions data used for the estimate (i.e ., 1990s emissions factors versus recent Subpart W measurements), the primary difference is that only larger facilities that exceed the GHGRP threshold of 25,000 metric tons CO 2 equivalent (CO 2 e) report for the GHGRP. For compressors in the transmission segment, comparisons indicate that:

• Reciprocating compressor emissions are over seven times higher in the National Inventory than Subpart W; and

• Centrifugal compressor emissions are over 30 times higher in the National Inventory than Subpart W.INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 8 of 17 These differences are due in part to the fact that many facilities were not required to submit a GHGRP report because only 30 perc ent or less of the transmission compressor stations exceeded the reporting threshold for the GHGRP. In c ontrast, the National Inventory uses “coarse” activity data (e.g., facility count for many sources , compressor count for compressor emissions). This can be reconciled by normalizing compre ssor emissions from Subpart W based on total emissions and total compressors (or facilities) for reporting facilities and then scaling using National Inventory activity data. Using data collected from INGAA members for 2011 GHGRP reporting, INGAA completed an initial analysis to normalize GHGRP data then scale the

emissions based on the National In ventory activity data (i.e., co mpressor counts for the entire sector). This initial analysis to scale emissions shows that th ere remain significant differences for transmission compressors, including:

• Reciprocating compressor emissions are over 50 percent higher in the National Inventory than based on Subpart W data; and

• Centrifugal compressor emissions remain very disparate – 20 times higher in the National Inventory than based on Subpart W data.

This is based on an initial analysis and provide d as an example to demonstrate the significant uncertainty regarding compressor emission esti mates. More detailed analysis should be completed by industry stakeholders at a later date, and INGAA commen ts on Subpart W have inquired about EPA plans to review Subpart W data, especially measurement data from T&S facilities. In addition, INGAA and others that are required to complete compressor vent measurements for Subpart W have asked EPA to use that data to develop emission factors for compressors (e.g., in recent comments on propos ed Subpart W amendments). INGAA welcomes the opportunity to continue to expl ore how to best resolve these data inconsistencies and arrive at a reasonably accurate inventory that balances the considerable expense and burden incurred by INGAA members to implement Subpart W measur ement and reporting requirements with the

need for more consistent and accurate data.

These comparisons clearly show large uncertainti es regarding compressor emissions – especially for centrifugal compressors. There are si gnificant and important data gaps.

While some may presume that compressors are a primary source of emissions and mitigation measures are available, educated decisions abou t the need for, effectiveness of, and cost of mitigation cannot be made until the emission differe nces are resolved and there is a technically based understanding of compressor-related emissi ons. The contribution of various sources must be clearly understood before effective policies can be developed. Since GHGRP (and Subpart W) information is intended to inform policy decisi ons, it is imperative that program data be used

to advance the current understand ing of emissions and thus the potential for reductions. If Subpart W data shows significantly lower emissions from a particular source, then it would be appropriate to focus efforts on other sources . For example, focusing on emissions from centrifugal compressor emission sources, such as wet seal degassing vent s, may be unproductive because these sources may account for lower emi ssions than indicated by the National Inventory and because new units will use dry seals rather than wet seals.INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 9 of 17 To summarize:

• Two key available resources – GHGRP Subpart W reporting and that National Inventory – show very different emissions from compressors.

• It is imperative that emissions and the associ ated sources (e.g., vent s, leaks) be clearly defined, including understanding how differences in scope and approach affect the results from different programs. Signifi cant data gaps may still remain.

• If Subpart W is not meeting its intended objective, improvements in survey and reporting protocols should be considered, because the emissi ons data from this program is intended to inform policy decisions, such as methane re duction opportunities with in the T&S sector.

• “Compressor-related” emissions can include sources that are intended to vent (e.g., reciprocating compressor rod p acking) and equipment leaks (e .g., unit isolation valve when the compressor is shut down and depressurized.) Data is not consis tently “rolled up” for various reports listed by EPA, and consistent roll-up is n eeded to understand the actual emissions. The white papers intend for leak-r elated emissions (e.g., leaking valve) to be addressed by the Leaks Paper rath er than the Compressor Paper.

• Reported emissions from different studies may be based on emission factors that represent a different subset of emission sources – e.g., reciprocating compressor emissions factors include rod packing venting, and may also include leak sources (e.g., isolation valve leakage). Inconsistencies in different st udies can introduce problems when comparing emissions or assessing mitigation effectiveness. For example, “average” times in different operating modes and both vented and leak sources are integrated into “composite” compressor emission factors in the original EPA-GRI study. Significant review of each study and emissions roll-up is needed to understa nd the data and implications better. This

can influence emission reduction calculations – e.g., control effectiven ess for rod packing maintenance should not be applied to an emissi on factor that includes other emission sources (compressor-related leaks). This is di scussed further in the next section.

• A systematic program needs to be developed an d implemented to understand the data that is available through Subpart W, the National Invent ory, and other sources to ensure that it is representative and consistent over the primary platforms being used by EPA to inform GHG policy. Leveraging Subpart W data and ongoing GHG RP requirements shoul d be integral to that process.

• Additional work is being completed. Still, a co mprehensive, systematic approach is needed to understand fully the data generated by S ubpart W, as well as how the accuracy and completeness of this data collection effort can be improved. Industry projects include an ongoing PRCI project to compile and analyze Su bpart W data and related supplemental data provided by PRCI and INGAA members. In addition, several natu ral gas transmission companies are participating in a study with the Environmental Defense Fund that includes

measurements at a number of T&S facilities, including on-site measurements and mobile monitoring using tracers. Results from that study should be av ailable later this year.INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 10 of 17 5. Compressor Mitigation Techniques and Costs 14

The Compressor Paper discusses available emission mitigation techniques and focuses on reducing vented emissions from reciprocat ing compressor rod packing and centrifugal compressor wet seal degassing. As noted in the emissions discussion above, INGAA’s understanding is that leak-related emissions (e.g., from a leaking is olation valve) are addressed in the Leaks Paper. As noted in earlier comments, the mitigation information presented is only a sampling of available technologies and work practices. A PRCI report is being completed that should be available this summer; that report is intended to provid e a thorough list of technologies and work practices, and the associated performa nce and cost of such technologies and work practices. It includes both ex isting mitigation methods and developmental or conceptual approaches. The report includes all but one of the T&S mitigation techniques in the ICF paper and also includes many additional prospective m itigation technologies and work practices and their technical feasibility. While the PRCI report includes mitigation techniques that are currently in development or less common techni ques, detailed appendices address the primary mitigation techniques. INGAA expects it will be able to share information from this report with

EPA soon.

INGAA is concerned with EPA’s estimates of pote ntial reductions. As no ted in Section 4, there is significant uncer tainty about emissions, yet an assumed baseline emissions level is used to estimate potential reductions. Clea rly, emissions data gaps need to be addressed before potential

reductions can be understood. Section 4 also di scusses the potential for errors in reduction

calculations based on an unclear understanding of emission factor s. For example, a reduction target for “compressors” applies a mitigation tech nique to reciprocating compressor rod packing. However, emission factors, such as EPA/GR I study emission factors used in the National Inventory, may represent emissions from several compressor-related sources, including leaks. These “typical” emission factor s are a composite of different emission sources (e.g., rod packing venting, isolation valve leakage) and typical time in different compressor modes (e.g., operating, shutdown and depressurized). For a technology or pr actice that redu ces rod packing venting, it is not appropriate to calculate the reduction using an emission factor that includes both rod packing and leak emissions. To understand the specific im plications, significant additional review of the Compressor Paper material would be required (e.g., decouple the emissions factors and only apply rod packing reduction to th e portion of the emission factor that applies to rod packing emissions). That was not possible within the comments schedule and may not be productive. Rather than delving into such nuance, EPA should consider identifying the differences in available data (e.g., comparing the National Inve ntory to Subpart W) and design and implement a systematic approach to resolve these differences and address data gaps.

The Compressor Paper does not discuss cost sens itivities and factors that contribute to cost differences from facility to facility. The draft PRCI report, discussed above, will include several approaches for reviewing economic implications , and present cost ra nges. Site-specific operating conditions and requirements can result in a wide range of mitigation costs. INGAA

asks EPA to consider the additi onal information provided, when available, in the PRCI report.

14 This section generally responds to Compressor Paper questions 3, 4, 5, and 6 (on mitigation technologies, reductions and costs), 10 (on prevalence) and 12 (ongoing or planned related studies).INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 11 of 17 As with other issues, INGAA welcomes that oppor tunity to continue to engage with EPA on understanding mitigation performance and costs. As noted throughout these comments, a clearer understanding of emissions should be attained to reduce uncertainties in assessing mitigation performance and costs.

Condition-Based Maintenance for Rod Packing

The Compressor Paper fails to, and should, in clude condition-based maintenance for rod packing. This is used by some companies as an alternative to ma intaining / replacing rod packing at a prescribed interval. Reliability st udies have shown that many different mechanisms

can affect the need for maintenance or contri bute to the failure of a component (e.g., packing wear that increases emissions). Prescribed maintenance intervals are a relatively antiquated approach that is being replaced in many cases wi th predictive or condition-based maintenance, where operating conditions are monitored and maintenance decisions are based on performance (or defined “conditions”) rather than assuming a specific time basis (e.g., every 3 years) for maintenance. INGAA strongly recommends incl uding condition-based maintenance for rod packing as a viable alternative to mitigate methane emissions.

Condition-based maintenance practices may exte nd the operation of functional rod packing and preclude premature and wasteful rod packing main tenance/replacement. In other cases, it will identity rod packing where premature wear warra nts maintenance on a more frequent basis than the prescribed interval . It also encourages the deve lopment of innovative rod packing technologies. This option considers current pr actices being used by operators, improvements to rod packing design, and the evolving technology.

The EPA Natural Gas STAR program includes a lessons learned document “Reducing Methane Emissions from Compressor Rod Packing System,” 15 which provides an example for conditionbased maintenance practices. Rod packing gas l eaks are periodically monitored and the value of the incremental leaked gas (relative to post-main tenance/replacement leak rates) is compared with the discounted rod packing maintenance/replacement cost. When the incremental lost gas value exceeds the maintenance/replacement cost, the rod packing maintenance/replacement is cost-effective. This same general philosophy can be applied using a different basis for the repair decision, such as a defined leak rate or change in leak rate over time.

Changing compressor rod packing at a set interval is discussed in the Compressor Paper as a means of reducing methane emissions. We s upport this approach pr ovided the operating company is allowed the flexibility to establish a packing replacement interval coordinated with regular scheduled maintenance. The desired outcom e of a rod packing replacement protocol is to prevent methane emissions to the environment, but the frequency of replacement must consider

the blowdown emissions that occur each time the packing is replaced.

Companies understand the value of rod packi ng monitoring and maintenance/replacement programs, and such programs have been instituted as part of safety and standard maintenance practices. EPA requests more details on mitigatio n techniques, including prevalence, but those answers are not known. For example, a survey would be required to understand the prevalence

15 http://www.epa.gov/gasstar/documents/ll_rodpack.pdfINGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 12 of 17 and common procedures for rod packing condition- based maintenance. In general, conditionbased maintenance grounded on periodically measuri ng rod packing leak rate typically will show a relatively flat leak rate over ti me, followed by an increase in leak rate when rod packing begins

to fail.

Low Emissions Rod Packing

Question 3 from the Compressor Paper asks ab out low emissions packing for reciprocating compressors. While this technology is available, INGAA questions whether its effectiveness has been proven. INGAA has not developed detailed in formation on this topic, but is aware that some operators currently are assessing its pe rformance by comparing conventional rod packing to low emission packing on similar units and mon itoring the vent rate and changes over time. Such evaluations indicate that low emissions p acking may emit at similar or higher levels than conventional packing. Thus, it is not apparentthat this technology can significantly reduce vented rod packing emissions. At best, th is technology requires additional study and improvement before its mitigation viability can be confirmed.

6. Compressor Mitigation – T echnology-Specific Questions 16

The Compressor Paper includes several questions specific to control technology, especially related to centrifugal compressor wet seal em issions. This section provides some general responses. As noted in Section 4, there is a signifi cant disparity in reported emissions from centrifugal compressors for Subpart W a nd the National Inventory. INGAA strongly recommends understanding and reconciling the di fferences and identifying, as appropriate, revisions to the National Inventory estimate or Subpart W methodologies. Mitigation-related questions cannot be addressed on an informed basis until that important data gap is addressed. It is possible that industry results from compila tion and review of Subpart W data or the collaborative study with EDF will offer some insi ghts, and those will be shared with EPA when

available.

Regarding centrifugal compressors with wet seals:

• New turbine / centrifugal compressor installation are unlikely to include wet seals, as dry seals have been the norm for about two decades are longer.

• Solar Turbines, the primary supplier of industrial-scale units used for natural gas compression, has not sold wet seal units for a number of years. A Solar Turbines representative indicated that it may consider a special request fo r wet seals but it is not aware of any such request in recent years.

• According to a centrifugal compressor manufactur er, dry seal technology replaced wet seals to provide benefits that include increased sa fety, reliability and efficiency, and reduced operating, utility and maintenance costs.

16 This section generally responds to Compressor Paper questions 7, 8, 9, 10, and 11(specific technology questions such as questions regarding centrifugal compressor wet seals).INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 13 of 17 • An informal query of INGAA members indicates that most companies last installed a unit with wet seals in the late 1980s or early 1990s. All subsequent installations included dry seals. However, one company provided an ex ample of three units with wet seals being

installed in the mid-2000s.

• Although there is an existing popula tion of older units with wet s eals, new units largely will be equipped with dry seals.

• For the existing units, Subpart W data indica tes that EPA has over-estimated the population of compressors with wet seals. For the transmission segment, the National Inventory assumes that 91 percent of centrifugal compresso rs include wet seals. Based on a review of the vast majority of Subpart W reports for 2011 and 2012, about 36 percent of units in 2011 and 48 percent in 2012 indicated wet seals in the Subpart W report. At this time, it is unclear why there is such a difference between the two years, but in either case, the population is significantly lower than the National Inventory estimate.

• As noted in Section 4, there is a 20-fold difference in the Nati onal Inventory estimate and an estimate scaled up from Subpart W data that us es the same activity data (total compressor count) as the National Inventor y. The population difference and associated contribution from wet seals is only a part of th at difference. Clearly, the Na tional Inventory emission factor differs from Subpart W results to date.

Initial review of 2011 Subpart W da ta (from a vast majority but not all reporting facilities in transmission) indicates about 70 measurements of wet seal degassing vents. The average

value for annual emissions was 0.56 MMSCF or about 260 metric tons CO 2 e (287 short tons). The emission factor for wet seal co mpressors presented in Table 3-11 is 126 tons

methane per compressor-year or 3,150 tons CO 2 e. This difference, along with the population count difference noted above, are most likely the primary contribu tors to the discrepancy in Subpart W and National Inventory estimates. Insi ght into the reason for this difference is not available at this time, but additi onal review, investigation, and analys is are clearly needed.

• The Compressor Paper inquires about replacing wet seals with dry seals for existing wet seal units. INGAA’s understanding is that this practice is possi ble but is not common. INGAA does not have data on how frequently wet seal s are replaced with dry seals. The Compressor Paper presents in Section 4.3.3 the capital co sts for replacement and O&M savings costs in Table 4-4 that are much more favorable for dry seal replacement than similar costs noted for the ICF paper. The discrepancy is not ac knowledged or explained. Compressor specific factors, such as compressor size, operating pre ssure, type of wet and dry seals, etc. also impact the costs for replacing a wet seal wi th a dry seal. One INGAA member company reported capital costs of $865,000 for replacement of a wet seal on a Solar Centaur 40 T4702S centrifugal compressor, based on a May 2014 vendor proposal. This is more than double the cost in the ICF paper and more than an order of magnitude higher than the costs in Table 4-4. It also requires extensive compre ssor downtime of approximately 7 to 8 months to perform the replacement of we t seals with dry seals, which has economic implications that need to be considered. The upcoming PRCI report may also provide additional information

on this issue for EPA’s consideration.INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 14 of 17 • Regarding vapor-recovery units (VRUs), I NGAA believes that th ere are safety and operational concerns not addressed in the Comp ressor Paper. The use of VRUs to capture emissions from rod packing vents has rarely (i f ever) been used in practice across the T&S sector and will require a feasibil ity or pilot study to determine the viability of the technology. Thus, INGAA does not support this control technique for compressor stations.

As discussed in INGAA’s comments on the Leak s Paper, it supports th e apparent consensus
from the literature that a few sources/leaks contri bute the vast majority of emissions (i.e., the 80/20 or 90/10 rule) from compressor stations . Thus, approaches such as “directed inspection and maintenance” would be preferre d for finding and mitigating larger emitters. Application of vapor recovery is unlikely to be a reasonabl e alternative. In addition, transmission facilities rarely include flares so on site use of the rec overed gas is required. However, using the recovered gas may also intro duce safety issues (e.g., pressure of vent line and system pressures) or may not be compatible w ith fuel if considered for that purpose.

These bullets are intended to summarize informa tion related to centrifugal compressor wet seal mitigation questions from the Compressor Pape r. INGAA recommends that EPA reconcile the significant differences in estimated centrif ugal compressor emissions between the National Inventory and Subpart W. Once emissions are be tter understood, it is possible that emissions from wet seals will be lower priority, especially since future centrifugal compressor installations will include dry seals.

7. Coordinate Methane Initiatives across Agenci es and Establish a Primary Point of Contact

As part of the Obama administration’s Climat e Action Plan, the Administration has initiated

several efforts that address methane reductions , including revisions to the EPA Natural Gas STAR Program, launch of the Quadrennial Energy Review, revision of EPA’s GHGRP, the five methane white papers and plans to revise regu lations to control VOC emissions and possibly methane emissions, from the oil and gas sector. 17 This level of si multaneous activity on a common issue challenges the indus try and other stakeholders, a nd coordination between industry and policymakers and across agencies is cr ucial. Therefore, INGAA recommends the Administration establish a primar y point of contact responsible for ensuring coordination across the multiple federal agencies and departments task ed with methane-related initiatives impacting the T&S sector. Ideally, this point of cont act would provide guidance and assistance in the development, interpretation and implementation of methane policies. It can be difficult for the pipeline industry to manage the numerous and sometimes duplicative requests for information from multiple agencies and departments.

As questions arise about the overall climate chan ge strategy, it would be extremely helpful to have this same primary point of contact within the Administration to discuss methane and other GHG reduction issues, opport unities and policies.

17 For example, potential revisions to 40 C.F.R., Part 60, Subpart OOOO.INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 15 of 17 8. Conclusion

INGAA and its members are committed to redu cing methane emissions in a prudent and environmentally responsible manner. INGAA an d its members are undertaking initiatives to

understand the sources of T&S sector methane em issions and to identify the most significant

sources and the most cost-effective me thane emission reduction strategies.

In summary:

1. There are significant differences in compressor emission estimates for the National Inventory and Subpart W of the GHGRP. This is due in part to a subset of s ources reporting under the GHGRP, but the differences are not due solely to that fact.

2. These differences must be reconciled and emissi ons data gaps addressed before conclusions can be made regarding the efficacy of mitig ation measures or associated costs.

3. A systematic program needs to be developed and implemented to address data gaps and reach consensus conclusions on compressor emissions.

4. INGAA is aware of additional information that will be available fr om ongoing studies to supplement this discussion. This information may inform the process and provide some insight, but it is not expected that it w ill address all of the emissions data gaps.

5. Once emissions are better understood, INGAA recommends additional discussion on the implications, including costs, of potential mitigation methods.

6. Compressor Paper mitigation discussions focus on reciprocating compressor rod packing venting and centrifugal compressor wet seals. For rod packing, condition-based maintenance

should be included an alternative to maintain ing or replacing rod p acking on a prescribed schedule. Centrifugal compressor emissions reported for Subpart W are significantly lower than the National Inventory. In addition, new un its are equipped with dry seals, which has been the standard for over a decade. Thus, it may be inappropriate to continue to focus on

wet seal emissions.

INGAA appreciates the opportunity to comment on the Compressor Paper and will continue to provide EPA with additional inform ation as it becomes available.

Sincerely,

Lisa S. Beal

Vice President, Environment and Construction Policy

Interstate Natural Gas Association of AmericaINGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 16 of 17 Appendix A Compressor Charge Question and INGAA Response Quick Reference

1. Please comment on the national estimates of methane emissions and methane emission factors for vented compressor emissions presented in th is paper. Please comment on the activity data and the methodologies used for calculating emi ssion factors presented in this paper.

Responses are found in sections three a nd four of the INGAA comment document.

2. Did this paper appropriately characterize the di fferent studies and datasources that quantify vented emissions from compressors in the oil and gas sector?

Responses are found in sections three a nd four of the INGAA comment document.

3. Did this paper capture the full range of technol ogies available to reduce vented emissions from reciprocating compressors and wet seal centrifuga l compressors at oil and gas facilities? In particular, are there other options for reducing emissions at existi ng reciprocating or centrifugal compressors? For example, the EPA is aware of “low emissions packing” for reciprocating compressors but has no detailed information on this technology.

Responses are found in section five of the INGAA comment document.

4. Did this paper appropriately characterize the emissions reductions achievable from the emissions mitigation technologies discussed fo r reciprocating compressors and wet seal centrifugal compressors?

Responses are found in sections four and five of the INGAA comment document.

5. Did this paper appropriately characterize the capital and operating co sts for the technologies

discussed for reduction of vented emissions fr om reciprocating compressors and wet seal centrifugal compressors?

Responses are found in sections five of the INGAA comment document.

6. If there are emissions mitigation options for reciprocating and centrifugal compressors that were not discussed in this paper, please comm ent on the pros and cons of those options. Please discuss the efficacy, cost and feasibly for both new and existing compressors.

Responses are found in sections five of the INGAA comment document.

7. Are there technical limitations that make the replacement of wet seals with dry seals impractical at certain existing centrifugal compressors?

Responses are found in section six of the I NGAA comment document.8. Are there technical
reasons why an operator would use a wet seal centrifugal compressor wi thout a gas recovery
system?INGAA Comments on EPA Compressor White Paper June 16, 2014

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Page 17 of 17 Responses are found in section six of the INGAA comment document.

9. Are there technical limitations that make the installation of gas capture systems at certain reciprocating compressors impractical?

Responses are found in section six of the INGAA comment document.

10. Please comment on the prevalence of the differe nt emission mitigation options in the field.

Responses are found in sections five and six of the INGAA comment document.

11. Given the substantial benefits of dry seal systems (e.g., lower emissions, less maintenance, and higher efficiency), are you aw are of situations where new we t seal centrifugal compressors are being installed in the field? If so, are there specific appl ications that re quire wet seal compressors?

Responses are found in section six of the INGAA comment document.

12. Are there ongoing or planned studies that will substantially improve the current understanding of vented VOC and methane em issions from reciprocating and centrifugal compressors and available techniques for increa sed product recovery and emissions reductions?

Responses are found in sections four and five of the INGAA comment document.