Operators of compressor stations that are part of gas gathering systems are often faced with the conflicting goals of maximizing capacity throughput while minimizing emissions. Increasing compression horsepower generally requires adding more compressor engines, which necessarily results in greater emissions.
Maintaining emissions levels below Major Source thresholds is a critical goal for operators seeking to avoid time-consuming and costly Title V operating permits. Non-compliance can lead to hefty fines and restrictive operating practices.
This article covers some of the key aspects of emissions regulation compliance for air permits and how innovative technology-based solutions can help compressor station operators achieve the goals of maximizing throughput while minimizing emissions.
Understanding Compressor Station Emissions and Compliance
For compressor stations, emissions regulations typically focus on controlling emissions of volatile organic compounds (VOCs), nitrogen oxides (NOx), and greenhouse gases (GHGs). Compliance with these regulations often requires obtaining air permits, which specify the allowable emission limits and the necessary control measures. These limits vary, typically based on the size of a facility and its location (i.e., is it located in a non-attainment area).
Recently, the U.S. Environmental Protection Agency (EPA) issued its final update to emissions regulations in its New Source Performance Standards Subpart OOOOb (NSPS OOOOb), impacting oil and gas facilities placed into service or modified after December 6, 2022. NSPS OOOOb is just one part of the former Biden Administration’s “whole of government” approach to reducing methane and other emissions from the Energy sector.
The Role of Air Permits
Air permits are for both new facilities and expanding existing ones. These permits are typically categorized into two types: minor source permits and major source permits, also known as Title V operating permits. Minor source permits are generally easier to obtain and involve less stringent requirements, while Title V permits are required for facilities with higher emissions and involve more comprehensive monitoring and reporting obligations.
Compressor station operators aim to keep emissions, specifically the Potential to Emit (PTE) below major source thresholds to avoid the costly Title V permit process and its ongoing compliance requirements. With a Title V permit, operators must certify compliance when applying and usually recertify annually, along with submitting monitoring reports at least semi-annually.
The default value for defining a “major source” threshold that would require a Title V operating permit is 100 tons per year (tpy) of any air pollutant from an emissions source (e.g., a compressor station, tank battery, or other covered facility). Maintaining emissions below this threshold is an important priority. Note that the major source thresholds are different in various jurisdictions, primarily depending on whether the area has been classified as a “Non-Attainment” zone, where more stringent standards would apply.
Challenges in Compliance
Compressor station operators face several challenges in achieving compliance with emissions regulations. These challenges include:
- Complex Regulatory Requirements: Navigating the complex web of federal, state, and local regulations can be daunting. Each jurisdiction may have its own set of rules and standards, making it essential for operators to stay informed and up to date.
- Monitoring and Reporting: Compliance often requires continuous monitoring of emissions and regular reporting to regulatory agencies. This can be resource-intensive and time-consuming.
- Control Technologies: Implementing effective emissions control technologies is crucial for compliance. However, selecting and maintaining the right technologies can be challenging and costly.
Minimizing Compressor Station Emissions
There are several things compressor station operators can do to minimize emissions from their facilities, and perhaps the most impactful is maximizing fuel gas quality. Lean fuel gas allows compressor engines, both reciprocating and turbine, to operate at peak performance (maximum horsepower) and minimize emissions of VOCs and particulates. Lean fuel gas with high resistance to detonation combusts more efficiently and completely, resulting in fewer emissions and greater energy.
Residue Lines
A traditional method for delivering lean, pipeline quality fuel gas to compressor engines is to install a residue gas line from a gas processing plant to a compression facility. A residue line can provide access to lean, pipeline quality fuel gas that burns cleaner producing fewer emissions and maximizing engine performance.
There are several downsides to using residue lines. They can be time-consuming and expensive to install, additional capital outlays may reduce overall ROI, the potential variability in gas quality and consistency, ongoing costs for maintenance and repair, and potential for creating fugitive emissions. Also, because they are fixed infrastructure, you cannot move a residue line when decommissioning a station and move it to a new location. In some cases, it may result in additional costs if the gas gathering contract does not include a fuel allowance.
Although residue lines are often considered the “gold standard” fuel gas solution, due to their downsides they are best used when your compressor station is located near processing facilities where residue gas is readily available, facilitating easier logistics and integration into existing infrastructure. Generally, residue lines are not feasible for remote locations.
New PSA Technology for Producing Lean Fuel Gas
The MaCH4 NGL Recovery Solution from Coldstream Energy is a technology-driven solution for generating residue line quality gas without the time and expense of a residue line. The MaCH4 solution uses patented, proven Pressure Swing Adsorption (PSA) technology that allows you to separate NGL’s from the production stream at the compressor station instead of burning them as fuel so they can be recovered downstream for increasing revenue and reducing emissions.
The MaCH4 system efficiently and effectively captures NGLs so you can monetize them instead of burning them as fuel gas and simultaneously delivers lean, dry fuel gas to your natural gas fired engines and equipment at compressor stations.
MaCH4 NGL Recovery Solution Benefits
The MaCH4 solution delivers three major benefits, including the ability to deliver lean fuel gas as the result of cryogenic-like recovery of heavy hydrocarbons.
- Minimize Emissions. Reducing VOC emissions up to 70% pre-catalyst, and up to 75% post-catalyst, while reducing CO2 emissions up to 8% upstream of engine catalyst. Ability to add more compression to a facility without triggering major source emissions thresholds and costly Title V operating permits.
- Maximize Throughput. Residue quality fuel gas minimizes engine derating (up to 9%) to maximize gathering station throughput and fee-based revenue.
- Maximize NGL Value. Cryogenic level NGL recoveries capturing 60% of C2 and 95% C3+, keeping NGL’s in gaseous form for downstream monetization.
Case Study – Iron Horse Midstream
The MaCH4 solution proved its value proposition in a rigorous pilot project with Iron Horse Midstream that was converted into a permanent installation in Q1 2025.
MaCH4 NGL Recovery Solution Pilot Emissions Reduction Performance:
- VOC reductions due to better quality fuel was confirmed during stack testing on a Caterpillar G3608 A3 engine during the pilot period.
- Over 70% fewer VOCs were emitted post-catalyst when operating on fuel produced by the MaCH4 unit compared to JT fuel gas.
- Actual stack testing demonstrated that VOC emissions pre-catalyst from the MaCH4 system were lower than the maximum VOC rate predicted by Caterpillar’s Gas Engine Rating Program (GERP).
- This could mean the potential of sitting more horsepower on a site before reaching permitting limits and potentially extending the life of catalyst elements within the stack.
Conclusion
Minimizing emissions from compressor stations is an important priority for both regulatory compliance and performance optimization. The MaCH4 NGL Recovery Solution can help operators not only meet their compliance obligations but also enhance their environmental performance, operational efficiency, and profitability. The MaCH4 solution offers a promising solution for reducing emissions and avoiding the complexities and costs associated with Title V operating permits for maximizing compression horsepower with the lowest possible emissions footprint.
Contact us today to learn about how the MaCH4 NGL Recovery Solution can help you minimize your emissions footprint and if it is right for your compressor station.
