Understanding the Scope

The EPA’s new rules, encompassing New Source Performance Standards (NSPS) OOOOb apply to new, modified, or reconstructed Oil and Gas facilities constructed after December 6, 2022, and supersedes both OOOO and OOOOa as older facilities are modified or reconstructed (e.g., expanding the capacity of a compressor station originally placed in service before December 6, 2022).

Emission Guidelines (EG) OOOOc is not a regulation per se, but instead a “model rule” for states and tribal land administrators to use for updating their own emissions regulations for existing facilities and is substantially similar to OOOOb. It is important to note, however, that states can develop regulations that are at least as restrictive as those in OOOOc, but they have the option to impose standards that are even more restrictive than EG OOOOc.

Under OOOOb and the eventual OOOOc plans, these regulations mandate that affected facilities meet a 95% reduction in emissions.

ECDs: Essential Tools for Emission Control

Enclosed combustion devices (ECDs) play a pivotal role in achieving compliance with NSPS OOOOb and EG OOOOc because they can efficiently meet the required 95% control efficiency requirement. NSPS OOOOb has numerous compliance requirements to ensure that ECDs being used to meet the 95% emission reduction standard can achieve that level of control continuously. In other words, operators can no longer just assume an ECD meets the 95% control efficiency requirement once installed, they must also demonstrate it on a continuous basis.

The rule lists the following affected facilities:

• Above ground storage tanks (tank batteries) for crude oil, condensate, and produced water
• Facility blowdown events
• Associated gas from oil and gas wells
• Seal venting for both centrifugal and reciprocating compressors
• Liquids unloading venting
• Pneumatic controllers and other natural gas-operated devices

There are several types of ECDs, including enclosed combustors (enclosed flares), thermal vapor incinerators, catalytic vapor incinerators, boilers, and process heaters. Our focus in this article is enclosed combustors and, in this post, we use the terms ECD and enclosed combustor(s) interchangeably.

The emissions objective for using ECDs is to meet the 95% emission reduction standard for methane and VOCs under OOOOb and OOOOc, or maintain total organic compound (TOC) concentrations in  For the latter option, Method 25A is used to determine compliance with the TOC exhaust gas concentration limit.

READ MORE: Method 25A – Gaseous Organic Concentration – Flame Ionization

Compliance through Testing and Monitoring

ECD Performance Testing

Operators have two compliance pathways to demonstrate ECDs meet control efficiency standards (40 CFR 60.5413b):

Manufacturer-Tested ECDs: The EPA maintains a list of approved models that have been tested by manufacturers using EPA-approved methods on its web page. If using an ECD that is on the EPA’s approved list, the operator does not have to make an initial test, but is required to make periodic tests (see note below).

READ MORE: EPA Approved Combustion Control Device Models That Have Been tested by the Manufacturer

Non-Manufacturer-Tested ECDs: If the operator is not using an ECD approved by the EPA, it must conduct both initial and periodic performance tests. An initial test must be completed within 180 days of startup consistent with the methods specified in 60.5413(b):

• Determine sampling sites using Method 1 or 1A.
• Determine gas volumetric flow rate using Method 2, 2A, 2C, or 2D, as appropriate.
• Determine compliance with percent reduction performance requirement using Method 25A.
• Measure TOC, as propane, to determine exhaust gas concentration limit using Method 25A.

Note that for all ECDs, including manufacturer-tested units, operators are required to perform periodic tests after initial installation. Consistent with 60.5413d(5)iii, the first periodic performance test must occur no later than 60 months after initial installation and startup, with subsequent periodic tests at intervals no longer than 60 months following the previous test.

READ MORE: Encino stack testing services for ECD compliance

Enclosed Combustion Device (ECD) Continuous Monitoring Requirements

Continuous monitoring of ECDs is mandatory, with specific requirements (§ 60.5417b):

• Pilot or combustion flames must be monitored continuously, triggering alerts for any extinguishment. Each continuous parameter monitoring system must take and record a reading at least once every hour. If the monitoring system detects the presence of a pilot or combustion flame, a reading must be taken at least once every 5 minutes.
• A monitoring plan must be prepared that covers each control device, consistent with EPA requirements.
• Monitoring system equipment must undergo performance checks, accuracy audits, or other audit procedures in the monitoring plan every 12 months.
• Heat sensing monitoring devices or those that detect a continuous ignition of a pilot or combustion flame are exempt from the calibration and quality control requirements for other monitoring devices.

Note that we plan to cover monitoring plan requirements in a future blog article.

Net Heat Value (NHV) Compliance

It is important to define the term heating value in context of the regulation.

NHV of inlet gases to Enclosed Combustion Devices is critical to achieving control efficiency and the EPA has specific requirements based on device type and operational conditions. For manufacturer tested ECDs, the inlet gas must have a net heating value (NHV) of the gas, as summarized in the table below.

Btu/scf = British thermal units per standard cubic feet

NHVcz = NHV combustion zone parameter
NHVdil = NHV dilution parameter

Operators may use the following options for initial ECD inlet vent gas NHV testing:

• Demonstrate the inlet gas to the ECD (except steam-assisted and air-assisted ECDs) meets or exceeds the NHV requirements using a 14-day sampling/chemical analysis program. If using this method, a minimum of 28 samples are required, and periodic sampling and chemical analysis are required once every five years.
• Continuously measure Btu (British thermal units) of inlet gas using a calorimeter, gas chromatograph, mass spectrometer, or grab sampling and chemical analysis of the vent gas.
• For ECDs, continuously monitor exhaust gas to verify total organic carbon (TOC) concentration is less than or equal to 275 ppmv (as propane).
• For unassisted or pressure-assisted ECDs or flares that initially demonstrate the vent gas combusted consistently exceeds the NHV requirements, no continuous measurement of the NHV of gas required.

Although continuous NHV monitoring is not required for inlet gas that is associated gas from a well with high enough NHV, periodic or continuous monitoring of NHV may be required by OOOOb for some applications.

Emissions Performance Engine Testing

How the EPA came to the 14-day sample program and 28 samples determination is revealed in the comments made during the rulemaking process.

A commentator remarked that if the initial NHV sampling demonstration determines that the NHV of a gas stream is always above the required NHV, continuous monitoring is unnecessarily burdensome, making it even more burdensome than what is currently required for refineries.

The commentator estimated the cost of a vendor-conducted 10-day continuous monitoring campaign for the initial NHV sampling (depending on method) would range between $250,000 and $400,000.

In contrast, another commentor disagreed with the assumption that NHV from vent streams will always exceed the minimum, and that infrequent monitoring would not capture the variability in gas stream composition, which directly impacts NHV, over time.

The EPA response included that it “…disagrees with the comments that neither continuous monitoring nor the initial NHV sampling demonstration (which the EPA proposed as an alternative to continuous monitoring) is unnecessarily burdensome or its cost unreasonable…”

However, the agency did modify its proposal in the final rule to reduce the number of daily samples to twice daily sampling for 14 days, reducing the total number of samples from 240 to 28.

Summary

In the final version of NSPS OOOOb and EG OOOOc the EPA established sweeping new requirements for reducing emissions of methane and VOCs from the Oil and Gas sector, including the mandate to use ECDs to reduce emissions from the Oil and Gas sector. Operators are required to demonstrate their ECDs meet the performance standards, among other mandates.

Standards of Performance for New, Reconstructed, and Modified Sources and Emissions Guidelines for Existing Sources: Oil and Natural Gas Sector Climate Review.

READ MORE: Navigating the EPA Final Rule for Methane Reduction: Solutions for Oil and Gas Operators Subjected to NSPS OOOOb and More