Data Dispatch: Methane Emissions from Gas Flares

Carbon Mapper Data Dispatches are regular communications highlighting insights and information from the Carbon Mapper Data Portal. We believe transparency is critical in the global fight against climate change. That’s why Carbon Mapper is committed to delivering accessible data on methane and CO2 emissions so that it can be used by policymakers, regulators, operators, and civil society to guide science-based action to reduce emissions.

Data Highlight

Image 1—a flare with no observed methane emissions.

 

 

Image 2—incomplete combustion from a flare Plume ID: GAO20210807t191744p0000-E

 

Image 3—an unlit flare Plume ID: GAO20191010t164043p0000-J

 

What we See 

These images show three different examples of flare stacks. Flare stacks are tall thin structures usually seen with a flame coming out the top. Flares stacks are mostly found in refineries, chemical and petrochemical plants, natural-gas processing plants, offshore exploration platforms, well heads, and landfills. Their main purpose is to combust vent gas—a substantial portion of which is methane (a byproduct of which is CO2 and water) as well as stabilize pressure and flow from a well. 

  • The first image shows a flare with no observed methane emissions. This indicates that the flare is operating as designed—where methane is fully combusted, and the emissions are primarily limited to CO2. 
  • The second image shows a location where a flare and methane plume were simultaneously observed by Carbon Mapper, indicating incomplete combustion (releasing both methane and CO2).
  • The third image shows a large methane plume coming from the flare stack with no simultaneous flare detection, indicating the flare is unlit, releasing methane directly into the atmosphere.

Carbon Mapper Project Scientist Dr. Dan Cusworth explained how he identifies these flares—and the process he goes through to identify whether the flare is operating properly—during airborne surveys, using the Permian Basin as an example. 

“For every area we survey, we look for methane plumes. In the Permian, these are overlayed against a vast landscape. When we find a plume, we examine it further using Google Earth or our own context camera images to identify exactly where it is coming from and attribute it to a source. Often these plumes come from a very visible flare stack.” said Cusworth. “When the flare is operating as intended, we do not observe a methane plume. But when methane is not combusted fully it is obvious to the spectrometer because the heat swamps the instrument’s signal in a very predictable way—and it is clearly visible in our imagery.”  

Why it Matters

The inefficient or non-existent flaring of vented gas matters for several reasons. 

First, it represents a near-term opportunity to mitigate methane emissions in the oil and gas sector. Analysis from Carbon Mapper and other NGOs have found that relatively small number of malfunctioning flares can have a disproportionate impact on the methane emissions in major oil and gas producing regions. For example, Carbon Mapper found that during 2019 Permian Basin observations, 5% of all methane plumes detected were from flare stacks. But together, these emissions represented 12% of all methane detected by that study.

Better understanding where and when incomplete and unlit flares at the facility level are contributing to large methane emissions provides a significant opportunity to address those emissions through operator engagement and equipment maintenance. This is particularly true for unlit flares which can result in very large and sustained releases of otherwise invisible gas. 

Second, flaring issues have resulted in hidden methane emissions that are often under-reported and may not be fully captured in current emissions inventories. Assuming a typical composition of associated gas, flare combustion efficiency is estimated to occur at 98% by the US Environmental Protection Agency (EPA). The EPA inventory calculates methane emissions from permitted flares by taking reported gas volumes sent to flares and assumes that only 2% of the gas escapes to the atmosphere as methane. However, that approach results in an under-estimate of methane emission when a flare goes unlit (not combusting gas at all and releasing all of the methane directly into the atmosphere), or not operating properly (below 98% combustion efficiency and releasing a significant amount of methane along with CO2). Given that most facilities currently lack continuous on-site monitoring, these anomalous situations largely go undetected and unreported. The highly intermittent nature of these emissions further amplifies the need for sustained simultaneous measurements of methane emissions and the operational status of flaring equipment. 

Learn More 

Carbon Mapper conducted extensive analysis on flares during their 2019 Permian campaign and published these findings in the 2021 study, Intermittency of Large Methane Emitters in the Permian Basin available here.

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