EC

/R Incorporated Providing Environmental Technical Support Since 1989

501 Eastowne Drive, Suite 250  Chapel Hill, North Carolina 27514

Telephone: (919)484-0222  Fax: (919) 484-0122

MEMORANDUM

DATE: August 1, 2013

SUBJECT: Cost and Secondary Environmental Impacts Associated with Controlling Storage 

Vessels under the Oil and Natural Gas Sector New Source Performance Standards

FROM: Heather Brown, EC/R Incorporated 

TO: Bruce Moore, EPA/OAQPS/SPPD/FIG

The purpose of this memorandum is to document the estimated cost and secondary 

environmental impacts related to reducing volatile organic compound (VOC) emissions from 

new storage vessels using a combustion device to comply with the new source performance 

standards (NSPS) for the oil and natural gas sector (40 CFR part 60, subpart OOOO).

On April 12, 2013, the Environmental Protection Agency (EPA) proposed amendments to the 

Oil and Natural Gas Sector NSPS (subpart OOOO) to address reconsideration of certain 

provisions of subpart OOOO. As a part of the proposed action, EPA established an alternative 

mass-based emission limitation of 4 tons per year (tpy) of VOC uncontrolled storage vessels. To 

respond to comments on its rationale for choosing the 4-tpy mass-based emission limit, the EPA 

further evaluated the cost of controls and secondary environmental impacts associated with 

operating a combustion control device at emission rates other than 4 tpy.

COST IMPACTS ASSOCIATED WITH COMBUSTION DEVICE OPERATION 

Cost effectiveness was calculated for several regulatory options to determine the appropriate 

mass-based alternative emission limit. Regulatory Options A through E represent uncontrolled 

VOC emissions ranging from 1 tpy to 6 tpy, respectively. The annual cost of $19,580 per year 

associated with operating a combustion device was previously estimated for the final, April 

2012, NSPS.1 Emission reductions were calculated based on a 95 percent control device 

efficiency. The options are presented in Table 1. As shown in Table 1, the cost effectiveness 

ranges from a maximum of $20,611/ton for uncontrolled VOC emissions of 1 tpy down to 

$3,435/ton for uncontrolled VOC emissions of 6 tpy.

SECONDARY ENVIRONMENTAL IMPACTS ASSOCIATED WITH COMBUSTION 

DEVICE OPERATION

Secondary environmental impacts were estimated for nitrogen oxides (NOX), carbon monoxide, 

and carbon dioxide (CO2) emissions associated with the combustion of the VOC emissions from 

oil and condensate storage vessels. In addition, the emissions associated with the pilot light 

operation were estimated, as well as methane emission reductions associated with control of oil
2

Table 1. Cost Impacts Associated Regulatory Options Operating a Combustion Device to 

Reduce VOC Emissions 

Regulatory 

Option

Uncontrolled 

VOC 

Emissions 

(tpy)

VOC 

Emission 

Reduction 

(tpy)a

Total Annual 

Cost of Control 

($/yr)b

Cost 

Effectiveness 

($/ton)

A 1 0.95 19,580 20,611

B 2 1.9 19,580 10,305

C 3 2.85 19,580 6,870

D 4 3.8 19,580 5,153

E 5 4.75 19,580 4,122

F 6 5.7 19,580 3,435 a

Calculated as 95 percent of uncontrolled VOC Emissions.

b Total annual cost for one combustion device. Calculated in previous memorandum (see 

Reference 1).

and condensate storage vessels. These impacts were calculated on a per-combustion device basis 

for each of the regulatory options presented in Table 1.

Table 2 presents inputs used to calculate these secondary impacts. As shown in Table 2, the 

information necessary to calculate the NOX, CO, CO2, and methane emissions includes:

• Condensate and oil emission factors (tpy/bbl/day)

• Heating value of the oil and condensate vapor stream (British thermal units/standard 

cubic feet, Btu/scf);

• Methane heating value (Btu/scf)

• Gas-to-Oil Ratio (GOR) of the oil and condensate (scf per barrel, scf/bbl);

• NOX Emission factor (pounds per million Btu, lb/MMBtu);

• CO Emission factor (lb/MMBtu);

• CO2 Emission factor (lb/MMBtu);

• Pilot light gas usage (scf/hr)

• Methane to VOC ratio

The secondary emission impacts are shown in Table 3 for each of the defined regulatory options, 

using the inputs from Table 2. The associated liquid throughput for each oil and condensate 

storage vessel was calculated using the uncontrolled VOC emissions associated with each 

regulatory option and the corresponding oil or condensate emission factor. The associated GOR 

was then used to calculate the vapor stream flow rate. This flow rate was then converted to heat 

input using the heat value of oil or condensate vapor stream, as appropriate. Emissions of NOX, 

CO and CO2 were then calculated using the emission factors identified in Table 2 and the heating 

input calculated for the oil or condensate vapor stream. 

Pilot light emissions were calculated using the same NOX, CO, and CO2 emission factors and a 

pilot light usage value of 70 scf/hr from Partner Reported Opportunities associated with the 
3

Natural Gas STAR program. As shown in Table 3, the NOX and CO emissions associated with 

combustion of the pilot light are an order of magnitude higher than the NOX and CO emissions

associated with combustion of the VOC stream.

Table 2. Inputs Used to Calculate Secondary Impacts

Variable Value Units Reference

Condensate VOC emission factor 2.09 tpy VOC/(bbl/day) 2

Oil VOC emission factor 0.214 tpy VOC/(bbl/day) 2

Heating value of vapor stream from 

condensate storage vessel

2,166 Btu/scf 3

Heating value of vapor stream from oil 

storage vessel

1,806 Btu/scf 3

Heating value of methane 1,011 Btu/scf

Condensate GOR 173 scf/bbl3 3

Oil GOR 18.9 scf/bbl3 3

NOX emission factor 0.068 lb NOX/MMBtu 4

CO emission factor 0.37 lb CO/MMBtu 4

CO2 emission factor 60 kg CO2/MMBtu 5

Pilot light natural gas usage 70 scf/hr 6

Methane to VOC ratio 0.207 3

Figures 1 and 2 illustrate the changes in cost effectiveness and secondary impacts for each of the 

regulatory options for condensate storage vessels and Figures 3 and 4 present these options for 

oil storage vessels. Figures 1 and 3 present how cost effectiveness, VOC, NOX and CO change 

with each regulatory option for condensate and oil storage vessels, respectively. Figures 2 and 4

show the cost effectiveness, VOC and CO2 emissions associated with condensate and oil storage

vessels, respectively. Pilot light emissions are constant and were not included in these figures. 

There is a significant increase in cost effectiveness values the lower the emissions of the 

uncontrolled storage vessel.
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Table 3. Secondary Emission Impacts Associated with Combustion of VOC Emissions from Storage Vessels

Regulatory 

Option

Uncontrolled 

VOC 

Emissions 

(tpy)

Associated 

Throughput 

(bbl/day)a

Vapor 

Flowrate 

from 

Storage 

Vessel

(scf/day)b

Heating Input 

from Storage 

Vessel 

(MMBtu/hr)c

Emissions Associated with 

Combustion of Vapor 

Stream (tpy)d

Emissions Associated with Pilot 

Light Operation (tpy)e

Total Emissions from 

Combustion of Pilot 

Light and Vapor Stream 

(tpy)f

NOX CO CO2 NOX CO CO2 NOX CO CO2

CONDENSATE STORAGE VESSELS

A 1 0.478 82.4 0.00744 0.00221 0.0121 4.31 0.0211 0.115 41.0 0.0233 0.127 45.3

B 2 0.956 165 0.01487 0.00443 0.0241 8.62 0.0211 0.115 41.0 0.0255 0.139 49.6

C 3 1.43 247 0.0223 0.00664 0.0362 12.9 0.0211 0.115 41.0 0.0277 0.151 53.9

D 4 1.91 330 0.0297 0.00886 0.0482 17.2 0.0211 0.115 41.0 0.0299 0.163 58.2

E 5 2.39 412 0.0372 0.0111 0.0603 21.5 0.0211 0.115 41.0 0.0322 0.175 62.5

F 6 2.87 495 0.0446 0.0133 0.0723 25.9 0.0211 0.115 41.0 0.0344 0.187 66.9

OIL STORAGE VESSELS

A 1 4.66 88.0 0.00662 0.00197 0.0107 3.84 0.0211 0.115 41.0 0.0231 0.125 44.8

B 2 9.33 176 0.0133 0.00395 0.0215 7.68 0.0211 0.115 41.0 0.0250 0.136 48.7

C 3 14.0 264 0.0199 0.00592 0.0322 11.5 0.0211 0.115 41.0 0.0270 0.147 52.5

D 4 18.7 352 0.0265 0.00789 0.0429 15.4 0.0211 0.115 41.0 0.0290 0.158 56.4

E 5 23.3 440 0.0331 0.00986 0.0537 19.2 0.0211 0.115 41.0 0.0309 0.168 60.2

F 6 28.0 528 0.0397 0.0118 0.0644 23.0 0.0211 0.115 41.0 0.0329 0.179 64.0

Note: Slight differences are due to rounding.

a Associated throughput (bbl/day) calculated using VOC emission factor of 2.09 tpy/bbl condensate/day or 0.214 tpy/bbl oil/day (see Table 2) and uncontrolled VOC emissions 

(tpy).

b Vapor flowrate (scf/day) calculated using gas-to-oil ratio of 172.5 scf/bbl of condensate or 18.9 scf/bbl of oil (see Table 2) and associated throughput (bbl/day). c

Heating input from storage vessel (MMBtu/hr) calculated using heating value of vapor stream of 2,166 Btu/scf of condensate vapor or 1,806 Btu/scf of oil vapor (see Table 2) and 

vapor flowrate from storage storage vessel (scf/day) and 24 hours/day.

d Emissions associated with combustion of vapor stream (tpy) calculated using emission factors for NOX (0.068 lb/MMBtu), CO (0.37 lb/MMBtu), and CO2 (60 kg/MMBtu) and 

heating input from the storage vessel. e Emissions associated with pilot light operation calculated using average annual pilot light gas usage estimate from Natural Gas STAR partners of 70 scf/hr and emission factors 

for NOX (0.068 lb/MMBtu), CO (0.37 lb/MMBtu), and CO2 (60 kg/MMBtu). f Emissions associated with combustion of vapor stream plus the emissions associated with the pilot light operation.
5

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

1 2 3 4 5 6

Emissions after Control (tpy)

Cost Effectiveness ($/ton VOC)

Uncontrolled VOC Emissions (tpy)

Figure 1. Cost Effectiveness and NOX, CO, and VOC Emissions Associated 

with Controlling VOC Emissions from Condensate Storage Vessels

Cost Effectiveness ($/ton)

VOC Emissions after Control

(tpy)

NOX Emissions Assoc with

Controlling VOC (tpy)

CO Emissions Assoc with

Controlling VOC (tpy)

Methane Emissions After

Control (tpy)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0

5,000

10,000

15,000

20,000

25,000

30,000

1 2 3 4 5 6

Emissions After Control (tpy)

Cost Effectiveness ($/ton VOC)

Uncontrolled VOC Emissions (tpy)

Figure 2. Cost Effectiveness and CO2 and VOC Emissions Associated with 

Controlling VOC Emissions from Condensate Storage Vessels

Cost Effectiveness ($/ton)

CO2 Emissions Assoc with

Controlling VOC (tpy)

VOC Emissions after Control

(tpy)
6

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

1 2 3 4 5 6

Emissions after Control (tpy)

Cost Effectiveness ($/ton VOC)

Uncontrolled VOC Emissions (tpy)

Figure 3. Cost Effectiveness and NOX, CO and VOC Emissions Associated 

with Controlling VOC Emissions from Oil Storage Vessels

Cost Effectiveness ($/ton)

VOC Emissions after Control

(tpy)

NOX Emissions Assoc with

Controlling VOC (tpy)

CO Emissions Assoc with

Controlling VOC (tpy)

Methane Emissions After

Control (tpy)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0

5,000

10,000

15,000

20,000

25,000

30,000

1 2 3 4 5 6

Emissions After Control (tpy)

Cost Effectiveness ($/ton VOC)

Uncontrolled VOC Emissions (tpy)

Figure 4. Cost Effectiveness and CO2 and VOC Emissions Associated with 

Controlling VOC Emissions from Oil Storage Vessels

Cost Effectiveness ($/ton)

CO2 Emissions Assoc with

Controlling VOC (tpy)

VOC Emissions after Control

(tpy)
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References

1. EC/R Incorporated, et al. 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. April 2012. EPA Docket No. EPA-HQ-OAR-2010-0505-4550.

2. Memorandum from Brown, H., EC/R Incorporated to Moore, B., US Environmental 

Protection Agency OAQPS/SPPD/FIG. Revised Analysis to Determine the Number of 

Storage Vessels Projected to be Subject to New Source Performance Standards for the 

Oil and Natural Gas Sector. April 8, 2013. EPA Docket Number: EPA-HQ-OAR-2010-

0505-4597.

3. EC/R Incorporated. Oil and Natural Gas Sector: Standards of Performance for Crude Oil 

and Natural Gas Production, Transmission, and Distribution. Technical Support 

Document for Proposed Standards. Prepared for U.S. Environmental Protection Agency. 

Research Triangle Park, NC. Appendix A. Publication No. EPA-453/R-11-0012. July 

2011. Docket No. EPA-HQ-OAR-2010- 0505-0045.

4. U.S. Environmental Protection Agency. Office of Air Quality Planning and Standards. 

AP-42, Fifth Edition, Volume I, Chapter 13.5. Industrial Flares. 1991

5. 40 CFR part 98, subpart Y, Equation Y-2.

6. U.S. Environmental Protection Agency. PRO Fact Sheet No. 903. Partner Reported 

Opporunities for Reducing Methane Emissions: Install Electronic Flare Ignition Devices. 

2011. Available on the Internet at: 

http://www.epa.gov/gasstar/documents/installelectronicflareignitiondevices.pdf