Exhaust emissions from gas engines and gas turbines have long been the focus of regulatory bodies seeking to lower the level of pollution. Now the US Environmental Protection Agency (EPA) and associated local air quality districts have turned their attention to the policing of fugitive emissions.
Fugitive emissions come from fuel leakage, unburned methane, and other sources of greenhouse gases (GHG) that don’t originate directly from the combustion process.
With this widening of the scope of EPA action, plant operators must up their game beyond the measurement of what comes out of the exhaust. They are now required to pay close attention to all sources of GHGs, including methane.
This has a major impact on any utility using reciprocating engines or gas turbines for power generation as well as those involved in oil & gas exploration, gas gathering, gas processing, and gas pipeline transmission activities.
Why all this attention on methane? Depending on how it is calculated, methane is said to be over 20x more potent than CO2 as a GHG in terms of climate change potential. If a shorter time frame is used, such as over 10 years, it becomes about 88x more potent.
After that, methane has largely dissipated in the atmosphere. That’s why many are looking at methane as a key target in reducing GHGs and arresting the rise in global temperature.
Addressing Methane Leakage
In 2022, the Inflation Reduction Act included stricter methane rules. It reduced the amount of allowable methane leakage to between 0.2% and 0.05% depending on facility type.
Penalties of up to $1,500.00 per metric ton for excess methane can be levied. Canada, too, has tightened the methane noose for upstream oil and natural gas facilities.
The latest batch of rules throughout North America make it critical that utilities, upstream producers and pipelines raise their game in the monitoring, measurement, and capture of fugitive methane emissions at various points along the value chain, including:
Methane Capture and Reuse
Leaked methane can be captured and channeled to another process or used for power generation purposes. Upstream drilling and production sites produce by far the most methane emissions in the oil & gas sector according to the EPA.
As drillers are beginning to switch their power generation equipment to natural gas, captured methane can be harnessed to supply the power needed at the drilling site. Portable power generation units are increasingly being deployed for this purpose.
As the drilling site moves, power generation trailers can be towed and hooked up to use recaptured or excess methane to produce electricity.
Better Sealing Technology for Pipelines and Compressors
Dry gas seals (DGS) for example, have become the de-facto standard in compression applications. They have reduced the amount of methane leakage considerably compared to older wet gas seals.
But DGS’ still leak and therefore are under the microscope. If compressors are stopped frequently, for example, dry gas seals may become contaminated. This can be avoided by depressurizing the compressor housing. During this process, large amounts of methane can escape.
To avoid such an outcome and maintain pressure in the compressor housing during downtime, a rotating seal gas booster can be used to keep seals clean during standby conditions, and at any time when insufficient seal gas flow occurs.
Facility Blowdowns
Emergency safety blowdowns have long been part of the safety and maintenance requirements for gas pipeline and storage operators. Improved sensors and more accurate alarm systems can eliminate costly false alarm blowdowns.
Alternate shutdown protocols and new facilities designed to capture blowdown discharge of methane reduce the amount of vented methane. For example, it is possible to blowdown into low-pressure gas storage systems to reduce methane emissions.
Leak Detection Systems
Pipeline facilities have long standing compliance programs to manage methane leaks. These programs now require instruments with a higher degree of sensitivity along with enhanced corrective action plans to reduce methane emissions.
Relatively few compressor stations have deployed continuous methane measurement tools. These tools come in the form of sensors in the station itself, as well as airborne infrared spectrometers which are flown over pipelines, storage fields, and oil & gas production sites and can detect/estimate methane leakage using wavelengths in light.
Facility Efficiency
The new rules mean that natural gas production, gathering, processing, and transmission facilities and power plants will need to find ways to measure the amount of methane coming in and compare it to how much is burned/recaptured. The goal is to reduce any shortfall to zero.
Hermetic Sealing
Hermetically sealed systems are an expensive but workable way to eliminate leakage. Equipment is packaged inside a container that doesn’t let anything in or out.
Flaring Efficiency
Flaring natural gas into the atmosphere has been greatly reduced in recent years. Nevertheless, it is still necessary at certain times. In those cases, higher-efficiency flare combustion ensures that almost all the methane is burned rather than some escaping into the atmosphere.
Packages are appearing on the market that combine a variety of combustion measurement elements such as a fuel measurement, fuel valves, sensors (O2 and NOx), catalyst monitors, with display panels and venturi elements to improve the fuel / air mix.
Sound Economics
These are just a few of the approaches that can be deployed to make a major difference to the amount of methane escaping into the atmosphere from oil & gas operations, pipelines, refineries, and anywhere that uses natural gas for power generation.
Further innovation will no doubt result in more ways to bring leakage down toward zero. That will require funding and interest on the research and development front.
The transition to a net zero carbon emissions future will require contributions for all forms for energy, including natural gas to be successful. Unfortunately, policy decisions as well as ESG scoring systems can sometimes make it difficult to fund new methane reduction, measurement, and recapture technologies.
If those hurdles are not overcome, those wishing for a greener future may inadvertently curtail GHG reduction efforts due to vocal opposition to anything connected with fossil fuels.
In addition to being an environmental imperative, methane capture and reuse makes sound economical sense. Oil & gas companies end up delivering more natural gas for sale to industry and end users.
Reusing leaked methane in power generation provides a fuel source that is free as it replaces oil or diesel and uses methane that would otherwise be vented to the atmosphere.
with contribution from Ted Lenart, Vice President of Gas Services, PFES
