Emissions

Methane emissions: Not just NOx and CO anymore

Plant operators must up their game beyond the measurement of what comes out the exhaust. They now are required to pay close attention to all sources of GHGs, including methane.
Methane emissions: Not just NOx and CO anymore

Power generators will need better controls to accurately measure fugitive and exhaust methane emissions.

By Archie Robb

Exhaust emissions from gas engines and gas turbines used to be the primary focus of regulatory bodies seeking to lower the level of pollution. But now the U.S. Environmental Protection Agency (EPA) and associated local air districts have turned their attention to the policing of fugitive emissions. Such emissions come from fuel leakage, unburned methane, and other sources of greenhouse gases (GHG) that don’t originate 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 the exhaust. They now are required to pay close attention to all sources of GHGs, including methane. Let’s review where things stand, and the steps facilities operating gas turbines and gas engines should take to address this shift.

Operators of gas turbines and gas engines will now need to monitor fugitive methane, as well as exhaust emissions. Photo Courtesy of Continental Controls Corp.

Rules and more rules

Things heated up on the compliance front more than a decade ago when air quality regulations were beefed up to include hazardous air pollutants (HAPs) from reciprocating internal combustion engines (RICE). Given the nickname RICE MACT (maximum achievable control technology), it is also sometimes referred to as 40 CFR Part 63.

To meet these requirements, engine owners initiated improved maintenance procedures, and deployed technology such as end-of-stack emission control equipment and catalysts to transform pollutants from the engine exhaust before they are emitted. What had begun as a set of regulations for large engines and major sources of pollutants in the early 2000s gradually filtered down to much smaller engines. This took shape in the form of National Emissions Standards for Hazardous Air Pollutants (NESHAP) for stationary RICE. The only recent update to these rules was a short August 2022 amendment related to emergency engines.

Gas turbine-based power plants, too, are subject to a variety of regulations based on federal, state, and regional standards. These traditionally have addressed sulfur dioxide (SO2), nitrogen oxides (NOX), particulate matter (PM), carbon dioxide (CO2), mercury (Hg), and other pollutants. Over the last few decades, the quantity of such emissions has been dramatically reduced. But methane is the big game changer.

“Natural gas, which is primarily composed of methane, has been regarded as a pollutant as well as a commodity since 2016 based on New Source Performance Standards (NSPS) targeting oil & gas operations (NSPS OOOOa),” said Brian Kromer, Managing Director and Principal, Step2Compliance.

Depending on how it is calculated, methane is said to be anywhere from 25 to 88 times more potent than CO2 as a GHG in terms of global warming potential. The latest batch of rules, therefore, makes it critical that facilities raise their game in the monitoring, measurement, and capture of fugitive methane emissions at various points along the value chain. This includes capturing any leaked methane and using it in combustion and other processes, as well as measuring the amount of methane coming into a facility and comparing it to how much is burned and recaptured.

More stringent compliance requirements

All of this is in the early stages. But with GHGs, climate change, Environmental Social and Governance (ESG) requirements on public companies and net-zero targets being so much in the spotlight, the screws will soon be turned. Facilities will be forced to prove they are fulfilling their environmental commitments. This fact was solidified in the August 16th passage of the Inflation Reduction Act, Public Law 117-169. This most recent act of Congress reduces the amount of methane that can leak and places a hefty fee on any excess methane of up to $1,500.00 per ton.

This is where the problems enter in.

“Methane is not easy to eliminate and doesn’t go away when you use a three-way catalyst,” said Rick Fisher, Vice President at Continental Control Corp. “Any plant running a gas turbine or gas engine is going to suffer methane leakage.”

Utilities, owners, operators, and plant personnel are grooved in to measuring emissions in the exhaust. Everything else is relatively virgin territory. Thus, it is quite likely that even those facilities that go to great lengths to comply with the latest requirements may still fall afoul or regulators as they failed to appreciate some nuance or other of the methane detection and control challenge

Why? Methane measurement and tracking is distinctly different than traditional exhaust emissions. In all likelihood, methane will require reporting on the amount of fuel that comes into a facility, how much was combusted, and how much methane leakage has been collected for reuse. It will probably usher in an era of real-time measurement. Official or agreed-upon standards for all of this have yet to materialize. There is a lack of independent bodies that can certify compliance. Traditional monitors and controls are not set up to accurately measure methane.

“Controls must now be able to accurately calculate GHG emissions as well as the conventional pollutants,” said Kromer. “Facilities must learn to track the amount of methane leakage and find ways to recapture it and put it to use.”

The Continental Controls Catalyst Monitor continuously measures pressure across the catalyst as well as pre- and post-catalyst temperature.

Measuring methane

The vendor community is beginning to respond to demand. There are a number of products that address the various needs of the methane measurement market. Here are a few examples:

Continental Controls Corp. (CCC) offers a range of fuel control, fuel measurement, and emissions monitoring tools to accurately measure GHGs. Its Catalyst Monitor continuously measures pressure across the catalyst as well as pre- and post-catalyst temperature and notifies the user if minimum or maximum temperatures are exceeded. When combined with CCC Air Fuel Ratio Controls (AFRC), it can make corrections to set points to maintain low emissions levels and extend the useful life of catalysts. This arrangement can be used to provide evidence of engine compliance and fuel consumption over an extended period of time.

Additionally, the CCC FM50 flow meter records individual flow to an engine or to an enclosed combustor at a point in time or total flow over a period of hours, days, or months. A mass flow calculation is used to continuously correct for temperature or pressure fluctuations. As it uses a venturi for flow measurement, pressure drop across the device is minimized.

“CCC does things that many can’t do such as continuously measure the true rate of methane compliance,” said Kromer. “Its tools can help monitor methane related to the exhaust as well as fugitive emissions.”  

Vortex Services of Canada offers the Vortex Emissions Target Solution. It packages a number of elements that address methane measurement such as a fuel measurement, fuel valves, a display panel, sensors (O2 and NOx) a catalyst monitor, and several venturi elements to improve the fuel/air mix.

Rules exceeded by commitments

Historically, regulations drove companies to take steps to improve their operations to achieve compliance. While this is still a major factor, we are now seeing plant operators, OEMs and others within the supply chain issuing emissions reduction targets and environmental commitments that go far in excess of historical regulatory mandates.

Fortunately, developments in methane monitoring and detection are introducing the necessary level of control over the measurement of fuel consumption and exhaust emissions and GHGs. These tools certainly help with compliance. But the bottom line is just as potent a driver and the new methane fee will affect the profitability of all operators. If almost all methane is captured and reused, the producer and transporter receive a higher rate of return and simultaneously avoid the methane fee.

About the author: Archie Robb is a writer from Southern California specializing in energy and business.