Attachment W

Pneumatic Devices

Environmental Defense Fund

Ramón Alvarez, Robert Harriss, David Lyon
Oil and Natural Gas Sector Pneumatic Devices 

Peer Review Responses of Environmental Defense Fund

June 16, 2014 

I. EXECUTIVE SUMMARY

• Pneumatic devices are, collectively, an important source of methane and other 

harmful pollutants. Pneumatic controllers and pneumatic pumps represent one of the 

largest sources of emissions of methane and other harmful pollutants within the oil and 

natural gas sector. EPA’s most recent Annual Inventory indicates that pneumatic devices 

in upstream petroleum and natural gas systems account for over 1 million metric tons of 

methane emissions per year. Recent studies confirm that these devices can individually 

have very high emissions, in some cases much higher than the average emission factors 

used for official emissions inventories. In addition, some recent literature suggests that 

the population of pneumatic controllers in the production and gathering segments is 

greater than EPA currently assumes on the basis of well counts. 

• Emissions from individual pneumatic devices are highly variable. Field research has 

also consistently indicated that there is wide variability in the emission rates of individual 

pneumatic devices. This variability demonstrates both the significant potential to reduce 

emissions by replacing or repairing the highest-emitting devices, as well as the role of 

good maintenance and sound facility design in preventing excess emissions. 

• Replacement of high-bleed pneumatic controllers with low-bleed devices is a highly 

cost-effective emission control measure. Studies have consistently found that replacing 

high-emitting pneumatic controllers with low-bleed models, or devices powered by 

instrument air or electricity, where feasible, avoids significant emissions and frequently 

yields an attractive rate of return for owners and operators. Experience with large-scale 

replacements of pneumatic controllers in the Denver-Julesberg basin indicates that such 

replacements are broadly feasible and that there are rarely significant operational or 

safety constraints that preclude such replacements. 

• Improperly maintained pneumatic controllers may represent an important emission 

reduction opportunity. Maintenance problems or malfunctions of otherwise lowemitting devices can be cost-effectively detected and resolved as part of a comprehensive 

leak detection and repair (LDAR) program. 

• Instrument air and electric-powered devices may be more broadly available than 

the White Paper indicates. Below, we present evidence that a significantly higher 

proportion of oil and gas production facilities may have access to grid power than is 

typically assumed. In addition, the use of solar-powered chemical injection pumps is 

now common operating practice in many regions of the country. 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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II. EMISSIONS FROM PNEUMATIC CONTROLLERS AND PUMPS

Pneumatic controllers and pumps are ubiquitous in the U.S. oil and gas sector, and 

collectively represent one of the industry’s largest source of methane and other harmful air 

pollutants. According to EPA’s Annual Inventory, which reflects the most authoritative national 

census of these devices, there were approximately 977,000 pneumatic controllers in use in the 

United States in 2012. Total methane emission from these controllers has been estimated to be 

over 1 million metric tons, which is approximately 13% of all methane emissions from the oil 

and gas sector.1 Companies reporting under EPA’s Greenhouse Gas Reporting Program, which 

applies only to a subset of oil and gas facilities that meet a certain emission threshold, reported 

similarly high emissions of over 870,000 metric tons in 2012. And ICF’s 2014 cost curve study, 

which is based on a modified version of the Annual Inventory, found that high-bleed pneumatic 

controllers alone will account for about 28 Bcf of methane emissions in 2018, equivalent to 

approximately 530,000 metric tons of methane. Consistent with the Annual Inventory, ICF also 

found that glycol pumps and chemical injection pumps are a large source of methane, with 

projected emissions of 11.5 and 5.9 Bcf in 2018, respectively.2 

Below, we respond to EPA’s charge questions and supplement the analysis in the White 

Paper by presenting recent information on emission factors, activity factors, and the distribution 

of emissions for pneumatic controllers and pumps. As the discussion that follows indicates, 

recent research is providing a more complete picture of the nature and scale of emissions from 

these devices. This research supports the widely accepted view that pneumatic devices are one 

of the largest and most widespread sources of avoidable emissions in the U.S. oil and gas sector. 

A. Pneumatic Controllers 

In this section, we present additional information on average emission factors for 

pneumatic controllers and pneumatic pumps; activity factors for pneumatic controllers; and 

variability in emission rates among pneumatic controllers and pneumatic pumps. 

1. Emission Factors (Questions 1, 2) 

The Gas Research Institute (GRI) study is the basis for current EPA estimates of 

pneumatic controller emissions in the Annual Inventory. The GRI measurements can serve as a 

useful benchmark for comparison purposes. However, due to the age of the GRI measurements, 

more recent measurement efforts are providing additional valuable insight into emissions from 

pneumatic controllers. 

 

 

1

 EPA, Oil and Natural Gas Sector Pneumatic Devices at 15, 18 (Apr. 2014) (“White Paper”) (summing net CH4

emissions and total controller counts from the production, transmission, and storage segments). 

2

 These emissions are equivalent to approximately 217,000 and 112,000 metric tons of methane, respectively. ICF 

International, Economic Analysis of Methane Emission Reduction Opportunities in the U.S. Onshore Oil and 

Natural Gas Industries 3-7 (Mar. 2014) [hereinafter “ICF Cost Curve Report”], available at 

http://www.edf.org/sites/default/files/methane_ cost_curve_report.pdf. 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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The Allen et al.3 and Prasino studies4 provide recent and robust data sets for pneumatic 

controller emissions. As the White Paper notes, the Allen study reports results of emission 

measurements for 305 pneumatic controllers, described as a mix of low-bleed and intermittent 

devices, with average emissions of 10.5 ± 2.0 scf/h methane. The White Paper correctly 

characterizes the average emission rates that were separately estimated for low-bleed and 

intermittent controllers, both of which were significantly higher than the values reflected in the 

Annual Inventory. 

The Prasino paper reports similar results to Allen et al; however, these results may not be 

representative because the study focused on high bleed devices in a single production area in 

Canada. Table 2-9 of the White Paper accurately presents the results in the Prasino report, but 

we note that the emission factors presented in the Table appear to represent whole gas and we 

recommend that this be stated explicitly in the Table to avoid confusion. The Prasino report also 

presents average bleed rates for several common pneumatic device types used for pressure and 

liquid level control, ranging from 0.5 to 14.8 scf/h whole gas. A potential limitation of the 

Prasino study is that the instrument that was used to quantify emissions creates back pressure on 

the vent line, and thus, may frequently report false zero emissions.5

 

The City of Fort Worth Air Quality Study (“Fort Worth Study”)6 includes a large set of 

pneumatics measurements made in 2010-2011 that are not considered in the White Paper. The 

Fort Worth Study states that pneumatic valve controllers were the most frequent emission 

sources encountered at well pads and compressor stations.7 The reported emissions from 480 

pneumatic controllers are presented in Appendix 3-B of the Fort Worth Study. We have 

extracted these results and provided them in an attached spreadsheet.8 Briefly, we identified 

pneumatic controllers in Appendix 3-B if: 1) a source's classification under the equipment type 

was labeled "PLLC," "PLC," "LLCB," "LLC," or "Other"; and 2) the component description 

included the terms "PVCB" (pneumatic valve control box), "LLCB" (liquid level control box), 

"PLLC" (pneumatic liquid level controller), or "PLC" (pneumatic level controller). A total of 

480 reported measurements met these criteria. Some of these components may be misclassified 

as pneumatic controllers using this approach; we have highlighted approximately 10 such likely 

misclassifications in the spreadsheet. We did not make any further reclassification since it 

required subjective judgment; however, we do not believe that the small number of potential 

misclassifications would significantly affect our analysis of the study. 

 

3

 David T. Allen et al., Measurements of methane emissions at natural gas production sites in the United States, 

Proceedings of the National Academy of Sciences (Oct. 29, 2013). 

4

 The Prasino Group, Determining bleed rates for pneumatic devices in British Columbia; Final Report (Dec. 18, 

2013). 

5

Id., at 9 and 21. 

6

 ERG and Sage Environmental Consulting, LP, City of Fort Worth Natural Gas Air Quality Study, Final Report. 

(July 13, 2011) [hereinafter “Fort Worth Study”], available at

http://fortworthtexas.gov/gaswells/default.aspx?id=87074. 

7

Id. at 3-99. 

8

 Fort Worth and UT pneumatics final.xls 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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The pneumatic controller emissions reported in the Fort Worth and Allen studies are 

summarized in Figure 1. The Fort Worth Study emissions average is 34.5 scf/h of methane, 

which is higher than the emissions average reported by the Allen and Prasino studies. On the 

other hand, the Fort Worth results are very similar to Environ's 2009 emission factor for liquid 

level controllers (31 scfh), the predominant application for the sampled pneumatics in the Fort 

Worth Study (see WP Table 2-11). The Fort Worth average emission factor is also consistent 

with the high-bleed emission factor that ICF derived from Subpart W data for its 2014 study of 

methane reduction opportunities in the oil and gas sector.9

One reason for the difference between the Fort Worth and Allen results is the sampling 

approach. At most sites, the Allen study randomly sampled from the controllers associated with 

the wells at the site. In contrast, the Fort Worth measurements were made on devices found to be 

emitting with an infrared camera or with a handheld hydrocarbon detector. This may explain 

why the Fort Worth study generally found higher measured emissions than the Allen study. In 

addition, as described in Part III of this response, the authors of the Fort Worth study observed 

that a number of the sampled pneumatic controllers appeared to be malfunctioning. 

As shown in Figure 1B, the Allen study and Fort Worth Study share a common feature 

that a small proportion of devices account for a large share of total emissions. In both studies, 

approximately 20% of the devices accounted for 70 to 75% of the total emissions. Further, there 

is wide variation in the individual emission rates measured, with a significant number of very 

high-emitting devices and a significant number of low-emitting devices. For example, 

approximately 40% of the controllers monitored in the Allen study had emission rates exceeding 

6 scf/h (the normal definition of a high-bleed controller), even though the study population 

contained no high-bleed controllers. At the same time, approximately 25% of the controllers in 

the Allen study had very low emissions of less than 1 scf/h. As Figure 1A shows, a similarly 

wide distribution of emission rates was observed in the Fort Worth study. 

 

9

 ICF Cost Curve Report, supra note 2, at B-6 (reporting high-bleed emission factor of 320 Mcf/yr, or 36.5 scf/h). 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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Figure 1. Emissions measurements of pneumatic controllers 

in the city of Fort Worth Study and Allen et al. 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.E-03 1.E-01 1.E+01 1.E+03

Cumulative Probability

scfh CH4

A. Distribution of pneumatic controller emissions (log scale)

Fort Worth

Allen et al.

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100

% of Emissions

% of Sites

B. Cumulative distribution

Fort Worth

Allen et al.
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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2. Activity Factor (Question 1)

There is uncertainty about the total number of pneumatic controllers, both in absolute 

terms and relative to the number of well sites, which are themselves fairly well characterized. 

The Annual Inventory assumes a ratio of pneumatic controllers to wells of roughly 1:1, and this 

ratio is a key driver for the total count of pneumatic controllers in the Annual Inventory. A very 

similar ratio was reported in a 2012 survey by the American Petroleum Institute (API) and 

America’s Natural Gas Alliance (ANGA).10 

However, several recent studies have found a higher ratio of controllers to well sites, 

including: 

• The Allen study sampled 305 devices, representing 41% of all the controllers at the 

sampled wells. Since there were 489 wells in the study, the number of pneumatic 

controllers per well is approximately 1.5.11 

• The Environ Report summarized on Table 2-11 in the WP indicates 3 devices per natural 

gas well. 

• A 2006 survey of producers in the Denver-Julesberg basin by the Independent Petroleum 

Association of the Mountain States (IPAMS) found approximately 3 devices per natural 

gas well. This survey was a critical source of information in Colorado’s recent 

rulemaking on emissions from high-bleed pneumatic controllers, and is discussed further 

in Part III of this response. 

Although it is difficult to draw firm conclusions from these studies, they do suggest that the 

ratio of pneumatic controllers to wells that EPA relies upon in the Annual Inventory is a 

conservative one - and that the actual number of pneumatic controllers in the production segment 

may be considerably higher than EPA currently assumes. In addition, ICF’s 2014 cost curve 

study noted that the Annual Inventory does not report pneumatic controllers located at gathering 

and boosting stations. Based on the API/ANGA survey, ICF estimated that approximately 

23,000 pneumatic controllers associated with gathering and boosting facilities are missing from 

the Annual Inventory.12 This reinforces the inference that the Annual Inventory assumptions 

regarding pneumatic controller counts are conservatively low. 

3. Future Studies (Question 9) 

The University of Texas is leading a follow-on study to Allen et al. The follow-on study 

will report additional measurements of emissions from pneumatic controllers. A manuscript 

reporting on these results is expected to be submitted for publication in a scientific journal in the 

summer of 2014. 

 

10 Terri Shires & Miriam Lev-On, Characterizing Pivotal Sources of Methane Emissions From Natural Gas 

Production 27 (2012) [hereinafter “API/ANGA Study”]. 

11 The ratio is estimated according to the formula: 305/(0.41×489) = 1.5. 

12 ICF Cost Curve Report, supra note 2, at B-6. 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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B. Pneumatic Pumps (Question 1) 

The White Paper does not appear to take note of the pneumatic chemical injection pump 

measurements in Allen et al. The Allen study sampled 62 chemical injection pumps, all located 

in the Gulf Coast and Midcontinent regions. Emission measurements were taken at these pumps 

using a HiFlow sampler. Some sites sampled in the Allen study had solar-powered chemical 

injection pumps, and therefore exhibited no pump-related methane emissions. 

The Supplemental Information accompanying the Allen study, at S-29-S-30, reports a 

slightly lower emission factor for pneumatic chemical injection pumps (12.2 scf/h) than the 

potential emission factor in the EPA Annual Inventory (13.3 scf/h). The Allen study 

encountered significant geographical variability in emissions rates among pneumatic pumps, 

similar to the variability among pneumatic controllers. The Allen study was not able to identify 

the cause of this variability, although several hypotheses were tested.13 The 2014 GHG EI 

reported national emissions from chemical injection pumps on a net basis, 65 Gg (Table A-141), 

which is in good agreement with the national estimate of Allen et al (68 Gg, 95% range of 35-

100 Gg). 

 

III. EFFICACY AND COST-EFFECTIVENESS OF MITIGATION OPTIONS

A. Replacement or Retrofit of High-Bleed Pneumatic Controllers 

(Questions 4, 5) 

EPA’s White Paper correctly indicates that replacing high-bleed pneumatic controllers 

with low-bleed models is an effective control strategy that achieves significant emission 

reductions and yields significant cost recovery for upstream operators. Citing Natural Gas STAR 

documentation and EPA’s 2011 TSD for the NSPS, the White Paper estimates that the 

replacement of a single high-bleed pneumatic controller in the production segment reduces 

emissions by an average of 6.65 tons per year of methane and 1.8 tons per year of VOC. Using 

standard assumptions regarding the average concentration of methane in natural gas, and a 

conservative natural gas price of $4/Mcf, the White Paper estimates that these emission 

reductions would equate to annual savings of approximately $1,500 per controller.14 This 

conservative estimate of savings suggests that operators would fully recoup the cost of a 

pneumatic controller replacement in less than two years. EDF strongly agrees that pneumatic 

controller replacements are an effective control strategy for methane and associated copollutants, and agrees that the assessments of cost-effectiveness presented in the White Paper are 

reasonable. Below, we provide additional information that broadly confirms the White Paper 

analysis and supplements the White Paper’s discussion of the applicability of this technique. 

 

13 Allen et al., Supplemental Information at S-30. 

14 The White Paper appears to include an erroneous calculation of the annual savings that would result from 

replacement of pneumatic controllers in the transmission segment. The savings estimate of $1,375 per controller 

appears to be based on an assumed emission reduction of 6.65 tons of methane per year. However, according to 

EPA’s 2011 TSD, a low-bleed pneumatic controller in the transmission segment reduces emissions by only 3.7 tons 

of methane per year. Using the assumptions in the White Paper, these emission reductions would equate to annual 

savings of approximately $767 per year. 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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1. Cost-effectiveness and efficacy of replacements. 

Recent studies of pneumatic controllers, which are not fully discussed in the White Paper, 

support the White Paper’s conclusions regarding the cost-effectiveness of retrofitting or 

replacing high-bleed devices. For example, the White Paper contains an incomplete discussion 

of ICF’s 2014 analysis of the cost-effectiveness and efficacy of replacing high-bleed pneumatic 

controllers. Based on emission factors derived from Subpart W data, ICF determined that an 

individual pneumatic controller replacement would reduce emissions by approximately 97%, and 

at a negative annual cost of -$3.08/Mcf of methane – even when assuming a relatively high 

capital cost of $3,000 per device. 

In addition, the Allen study supports the cost-effectiveness figures presented in the White 

Paper. As noted above, the Allen study reported a wide range of emission rates for the 305 low 

and intermittent-bleed controllers that were sampled. The highest-emitting 20% of pneumatic 

controllers sampled in the Allen study had an average emission rate of 37.7 scf/h, equivalent to 

approximately 330 Mcf/y and similar to the emission factor of 320 Mcf/y derived by ICF for 

high-bleed pneumatic controllers reported under Subpart W),15 and the lowest-emitting 20% had 

an average emission rate of 0.3 scf/h, equivalent to 2.6 Mcf/y. If the average pneumatic 

controller from the top-emitting quintile in the Allen study were replaced with the average 

pneumatic controller from the lowest-emitting quintile, the annual emissions avoided would be 

approximately 327 Mcf/y. At an assumed natural gas price of $4/Mcf, this would amount to 

$1,308 in savings per year per device, which is consistent with the analysis presented in the 

White Paper. 

The White Paper also appears to overlook significant state-level experience with 

mandating replacement of pneumatic controllers, and analyses that have been undertaken in 

support of those requirements. Colorado’s Air Quality Control Commission (AQCC) first 

mandated the replacement of existing high-bleed pneumatic controllers in the Denver-Julesberg 

basin in 2008. In 2014, the AQCC extended this requirement to all of the high-bleed pneumatic 

controllers in the state. On both occasions, the AQCC based its requirements on rigorous 

technical analyses of costs and benefits, which are attached here as exhibits. 

Colorado’s November 2008 analysis includes detailed information on bleed rates of new 

liquid level and pressure controllers; capital, installation and O&M costs associated with retrofits 

and replacements; and annual benefits of replacement, all based on an industry survey of 

pneumatic controllers in the Denver-Julesberg basin in 2006. Colorado’s analysis found that 

replacements of a high-bleed device would pay for itself within seven months, on average, and 

would achieve VOC emission reductions of close to 90%.16 For some types of pneumatic 

controllers, Colorado found an average payback time of just three months, using the relatively 

high gas prices that prevailed in 2008. 

 

15 ICF Cost Curve Report, supra note 2, at B-6. 

16 See Colorado Department of Public Health and Environment, Air Pollution Control Division, Denver 

Metropolitan Area and North Front Range 8-Hour Ozone State Implementation Plan, Technical Support Document 

for Proposed Pneumatic Controller Regulation 14-15 (Nov. 2008) [“APCD 2008”]. 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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In 2014, Colorado updated and supplemented this analysis.17 Among other things, 

Colorado increased the costs of controller replacements to account for inflation;18 assumed a 

very conservative natural gas price of just $3.50/Mcf; and estimated state-wide emission 

reductions based on the above-mentioned 2006 industry survey. Based on this survey, Colorado 

found that the average bleed rate of high-bleed controllers was 16.8 scf/h (140 Mcf/yr), and that 

the average bleed rate of low-bleed controllers was 1.93 scf/h (17 Mcf/yr). Even at substantially 

lower gas prices, Colorado found that replacement of high-bleed pneumatic controllers would be 

very cost-effective: replacement would have an annual net cost of -$1,084 per device and an 

average payback period of approximately 14 months.19

2. Evidence of significant emission reductions from replacements. 

The White Paper also contains little discussion of the potential for large-scale emission 

reductions from widespread replacement of high-emitting pneumatic controllers, which has been 

the focus of several recent studies. ICF’s 2014 report, for example, found that pneumatic 

controller replacements were not only highly cost-effective on an individual basis, but also 

represented one of the single largest emission reduction opportunities across the entire oil and 

gas sector. ICF estimated that if carried out nationwide, replacement of high-bleed pneumatic 

controllers would avoid nearly 25.4 billion cubic feet of methane emissions per year in 2018 

(approximately 480,000 metric tons of methane) – and at a negative cost of -$67.4 million per 

year.

20 ICF’s general conclusions regarding the efficacy of replacement are consistent with other 

analyses, including a 2013 report by the World Resources Institute that estimated that nationwide 

replacements of high-bleed pneumatic controllers could yield emission reductions of 19 million 

metric tons CO2-e by 2019.21 WRI identified high-bleed pneumatic replacements as one of the 

top three high-impact methane mitigation measures that could significantly reduce methane 

emissions from the U.S. oil and natural gas sector. 

Colorado’s 2014 analysis supporting the state-wide phaseout of high-bleed pneumatic 

controllers also found a significant potential for emission reductions, in part because Colorado 

found that a large number of high-bleed devices remained in the state. Based on 2006 industry 

survey data, Colorado found that each well in the Denver-Julesberg had an average of 3.1 

pneumatic controllers, and that slightly over 13% of those controllers were high-bleed devices. 

Further, based on industry input, Colorado determined that 95% of remaining high-bleed 

 

17 See Colorado Department of Public Health and Environment, Air Pollution Control Division, Prehearing 

Statement Exhibit SS (2014). 

18 Notably, Colorado’s cost study found that a low-bleed controller would cost approximately $1,033 with an 

additional $387 in one-time labor costs. This is substantially lower than the costs cited in the White Paper. Id. 

19 Colorado Department of Public Health and Environment, Air Pollution Control Division, Regulatory Analysis for 

Proposed Revisions to Colorado Air Quality Control Commission Regulation Numbers 3, 6, and 7 (Feb. 2014). 

20 For its analysis, ICF also conservatively estimated that approximately 10% of controllers in the production 

segment are high-bleeds, and that 90% of these could be replaced with low-bleed controllers. ICF assumed much 

lower rates of replacement in segments further downstream of production. ICF Cost Curve Report, supra note 8, at 

3-15 to 3-16. 

21 James Bradbury et al., Clearing the Air: Reducing Upstream Greenhouse Gas Emissions from U.S. Natural Gas 

Systems 28 (World Resources Institute, 2013). 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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controllers in the state could be retrofitted or replaced.22 Statewide, Colorado estimated that the 

requirement would apply to approximately 9,400 controllers and would achieve total methane 

emission reductions of over 15,500 metric tons per year (nearly 1 billion cubic feet of 

methane).23

Notably, the nationwide potential for emission reductions from pneumatic replacements 

could be much greater than the above-mentioned analyses suggest. As noted above, several 

recent studies – including the Allen study and the IPAMS survey used in the Colorado analysis – 

indicate that the number of pneumatic controllers per well site ranges from 1.5 to 3.1, or 50% to 

200% greater than the average EPA assumes in the Annual Inventory.24 ICF’s 2014 report also 

noted a 2012 survey by API and ANGA which found an average of approximately 8.6 pneumatic 

controllers at each gathering compressor station, of which approximately 7% were high-bleed 

controllers. These devices are not accounted for in the Annual Inventory.25 These studies 

suggest that overall emissions from high-bleed pneumatic controllers – and the potential for 

emission reductions through replacement or retrofit – could be much higher than the current 

Annual Inventory would suggest. 

3. Replacement of high-bleed pneumatic devices widely applicable 

Lastly, the White Paper states that operational or safety considerations may limit the 

applicability of replacements or retrofits of high-bleed pneumatic controllers. Such situations 

appear to be extremely rare, as Colorado’s experience requiring replacement of these controllers 

suggests. Colorado based its 2008 replacement requirement in part on information from industry 

suggesting that nearly all high-bleed pneumatic controllers in the Denver nonattainment area 

could feasibly be replaced.26 Notwithstanding this information, Colorado allowed owners and 

operators in the nonattainment area to petition for a waiver of the replacement requirement where 

necessary. EDF understands that Colorado has not received any petitions for such waivers in the 

six years since this requirement took effect. This is a strong indication that replacement of highbleed pneumatic controllers could be broadly applied. 

 

22 This assumption was adopted from the 2008 analysis, which found that “close to 100% of the high bleeds will be 

converted to low/no bleeds” based on industry feedback from the Colorado nonattainment area. See APCD 2008, at 

12. Notably, Colorado’s prediction was borne out by subsequent experience implementing the replacement 

requirement in the Denver ozone nonattainment area. In the 2008 regulation, Colorado allowed operators to petition 

for a waiver of the pneumatic controller retrofit/replacement requirement in situations where replacements or 

retrofits are not technically feasible or safe. EDF understands that no such petitions have been filed since that 

requirement took effect. 

23 Colorado Department of Public Health and Environment, Air Pollution Control Division, supra note 17. 

24 The Fort Worth study found that there were 1.3 emitting controllers per well site examined, suggesting that the 

ratio of total pneumatic controllers to wells was higher. 

25 ICF Cost Curve Report, supra note 2, at B-6. Based on the API/ANGA survey, ICF estimated that there are 

approximately 23,000 pneumatic controllers in the gathering and boosting segment that are not accounted for in the 

Annual Inventory. Notably, the API/ANGA survey also found an average of approximately 0.99 pneumatic 

controllers per well. 

26 See APCD 2008, supra note 16. 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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B. Enhanced Maintenance of High-Emitting Controllers (Question 3) 

In addition to replacing or retrofitting inherently high-emitting pneumatic controllers, 

proper maintenance of existing devices is essential to ensuring continued emission reduction 

over time. Application of regular leak detection and repair (LDAR) techniques to pneumatic 

controllers and pumps, especially as part of a comprehensive LDAR program applied to all 

components of an oil and gas facility, is a cost-effective way to identify maintenance issues and 

malfunctions in pneumatic devices. 

The White Paper appropriately cites Natural Gas STAR documentation in discussing 

potential emission reductions from enhanced maintenance, and common causes of upsets or 

malfunctions at pneumatic controllers. Additional literature, which is not cited to in the White 

Paper, further indicates that poor maintenance and malfunctions are an important cause of high 

emissions from pneumatic controllers. For example, the Fort Worth Study examined emissions 

from 489 intermittent pneumatic controllers, using infrared cameras, Method 21, and a HiFlow 

sampler for quantification. The study found that many of these controllers were emitting 

constantly and at very high rates, even though these devices were used to operate separator dump 

valves and were not designed to emit in between actuations. Average emission rates for the 

controllers in the Fort Worth study were 34.5 scf/h (302 Mcf/yr), or 6 tons per year of total 

organic compounds (TOC) – a rate that approaches the average emissions of a high-bleed 

pneumatic controller. Over 50% of the controllers emitted more than 16 scf/h (140 Mcf). 

According to the study authors, these emissions were frequently due to malfunctioning or 

failed controllers: 

Pneumatic Valve Controllers were the most frequent emission sources 

encountered at well pads and compressor stations. These controllers use 

pressurized natural gas to actuate separator unloading valves. Under normal 

operation a pneumatic valve controller is designed to release a small amount of 

natural gas to the atmosphere during each unloading event. Due to contaminants 

in the natural gas stream, however, these controllers eventually fail (often within 

six months of installation) and begin leaking natural gas continually. The 

emissions from the 489 failed pneumatic valve controllers detected by the point 

source team result in a combined TOC emission rate of 3,003 tons per year.27

 

The Prasino study of pneumatic controller emissions in British Columbia also noted the 

potential for maintenance issues to lead to abnormally high bleed rates.28 As noted above, the 

Prasino study – like the Fort Worth study and UT-Austin studies - found significant variability in 

the emission rates of pneumatic controllers. In particular, some pneumatic controllers that were 

nominally rated as “low bleed” models by manufacturers exhibited emission rates much higher 

than 6 scf/h in the field. Although the researchers did not identify a cause for these unexpectedly 

 

27 Fort Worth Study, supra note 5, at 3-99 to 3-100 (emphasis added). 

28 Prasino, supra note 3, at 19 (“Certain controllers can have abnormally high bleed rates due to operations and 

maintenance; however, these bleed rates are representative of real world conditions and therefore were included in 

the analysis.”). 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

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high emission rates, the results are consistent with the observation that maintenance and 

operational issues can lead to high emissions. 

 As the Fort Worth Study suggests, the same methods used for leak detection at valves, 

connectors, and other leaking components at oil and gas facilities can be used to spot significant 

malfunctions at pneumatic controllers. Moreover, if a comprehensive LDAR program is already 

being implemented at a facility, the marginal cost of extending that program to pneumatic 

controllers would be very modest. Well production sites typically have a small number of 

controllers per well.29 More complex facilities such as gathering and boosting facilities, and gas 

processing plants, may have eight to nine pneumatic controllers per site.30 In either case, 

however, pneumatic controllers would represent only a small fraction of the total number of 

components that would usually be monitored for leaks under a LDAR program. In the Fort 

Worth study, for example, the well production sites studied had an average of about 1,500 

components each. This is consistent with the Subpart OOOO technical documentation, which 

assumed that an intermediate-size well production facility with five wellheads would have 

approximately 1,200 components amenable to LDAR.31 

C. Conversion to Instrument Air or Electric Power (Question 8) 

The White Paper correctly notes that conversion of pneumatic controllers and pumps to 

compressed air, or to electrically powered devices, can eliminate emissions. However, the White 

Paper also notes that these strategies require either access to electric distribution infrastructure, 

or the use of solar-powered devices. Below, we offer additional information on the availability 

and cost of these technologies. 

1. Grid power potentially available at many production facilities. 

In the 2012 NSPS rulemaking, EPA assumed that grid electricity is not available at oil 

and gas facilities other than natural gas processing plants, and cited this as a key rationale for 

declining to require the use of no-bleed pneumatic controllers at such facilities. However, there 

is anecdotal evidence indicating that access to grid power at oil and gas production facilities may 

be more prevalent than is widely believed. One report commissioned by the North Dakota 

Transmission Authority in October 2012 – which was intended to forecast electric load 

requirements associated with growing oil and gas production in the Williston Basin – found that 

approximately 80% of 1,087 existing oil wells surveyed were tied to the electrical grid, and that 

95% would be connected to the grid in 10 years.32

 

 

29 As noted above, the Annual Inventory assumes approximately one controller per well, whereas recent field studies 

have found an average of 1.3 to 3.1 controllers per well. 

30 See API/ANGA supra note 9, at 26. 

31 EPA, Oil and Natural Gas Sector: Standards of Performance for Crude Oil and Natural Gas Production, 

Transmission, and Distribution, Background Supplemental Technical Support Document for the Final New Source 

Performance Standards C-3 (Apr. 2012). 

32 Kadrmas, Lee & Jackson, Inc., Power Forecast 2012: Williston Basin Oil and Gas Related Electrical Load 

Growth Forecast 15 (Oct. 2012), available at http://www.nd.gov/ndic/ic-press/Power2012.pdf. 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

13 

Similarly, an oil and gas producer in Oklahoma recently indicated at its annual meeting 

that only one in ten of its wells rely on generators for on-site power.33 Recent press reports from 

Oklahoma have also indicated that rural electric cooperatives are rapidly expanding generation 

and transmission capacity to serve growing loads from oil and gas production sites.34 Lastly, the 

ICF study assumed that approximately 50% of pneumatic glycol pumps could be replaced with 

electric pumps due to widespread access to grid electricity.35 All of these sources suggest EPA 

should undertake closer examination of the extent to which both new and existing oil and gas 

production facilities have access to grid power and can feasibly implement no-bleed alternatives 

to pneumatic controllers and pumps. 

2. Cost and availability of solar-powered pump technologies. 

Based on firsthand observations of oil and gas facilities, EDF also understands that the 

use of solar-powered chemical injection pumps is now widespread in key oil and gas producing 

regions such as the Eagle Ford basin and the Marcellus Shale. There are also a number of major 

vendors of solar-powered chemical injection pumps, which is a further indication that solarpowered pump technology is commercially available and broadly used. 

As further indication of the cost-effectiveness and widespread availability of this 

approach, one of the Natural Gas STAR partner companies reported as early as 2010 that it was 

replacing all chemical injection pumps in its Barnett Shale operations with solar-powered 

models. As of 2010, the company had replaced 140 pumps at a cost of $188,300 (approximately 

$1,300 per pump), and was avoiding over 8 million cubic feet per year in natural gas losses as a 

result. At this rate of savings, the company estimated it would recover its initial investment in 

slightly less than six years at a gas price of $4/Mcf, and slightly less than five years at a gas price 

of $5/Mcf.36

IV. EXHIBITS

1. EDF Analysis of Pneumatic Controller Emissions Data from Fort Worth Study and Allen 

et al., Fort Worth UT Pneumatics.xlsx (May 2014) 

2. Colorado Department of Public Health and Environment, Air Pollution Control Division, 

Denver Metropolitan Area and North Front Range 8-Hour Ozone State Implementation 

Plan: Technical Support Document for Proposed Pneumatic Controller Regulation 

(Draft, Nov. 2008). 

 

33 Jay F. Marks, Natural gas bringing cheaper electricity to Oklahoma oil play, NewsOK (July 12, 2013) (Reporting 

that the CEO of SandRidge Energy Inc., the leading producer in the Mississippian oil play, stated, “We have very 

few wells on generators at this point . . . . In this part of the world, we didn't have a full electrical distribution 

system. The company was very aggressive and stepped out and built these lines. From about a year and a half ago, 

we've taken the number of generators down from about 35 percent to about 11 percent.”) 

34 Victoria A. Rocha, Oklahoma Co-ops Face Oil, Gas Boom, (Sept. 25, 2012) (reporting on efforts by four 

Oklahoma co-ops to keep up with growing electricity demand from remote oil and gas production facilities). 

35 ICF Cost Curve Report, supra note 2, at 3-16. 

36 Zach Schaffer, Terry Chapman & Don Bredy, Renewable Power Applications at Natural Gas Well Sites 10 

(Chesapeake Energy, Nov. 2010). 
ENVIRONMENTAL DEFENSE FUND • JUNE 16, 2014 

14 

3. Colorado Department of Public Health and Environment, Air Pollution Control Division, 

Pneumatic Analysis, Prehearing Statement Exhibit SS (Date Unknown) 

4. Colorado Department of Public Health and Environment, Air Pollution Control Division, 

Regulatory Analysis for Proposed Revisions to Colorado Air Quality Control 

Commission Regulation Numbers 3, 6, and 7 (Feb. 2014).