Flaring of natural gas in the energy sector has long been considered highly efficient with methane “destruction removal efficiency”[1], or DRE, of 98%. A recent article in Science, however, takes issue with this figure after analyzing airborne samples taken across three of the largest oil-producing basins in the U.S.[2] The results challenge conventional beliefs about the efficiency of flaring and indicate that methane emissions from U.S. flaring may be significantly understated.
[1] DRE for CH4 represents the proportion of methane that has been converted to another species such as CO2.
[2] Plant et al., Science 377, 1566-1571, September 2022.
Field Measurements of Destruction Removal Efficiency
The basins surveyed were the Permian, Eagle Ford, and Bakken, representing approximately 80% of gas volumes flared in the nation. In twelve research flights conducted in 2020 and 2021, direct measurement of the composition of flare plumes resulted in samples of over 670 observations representing > 300 distinct flares across the three basins. Measured CO2 and CH4 in the flare plumes allowed the researchers to calculate the DRE for methane in flares that were actively operating. The mean DRE for methane was found to arithmetically average 95.2% and 95.6% when weighted by the observations for each basin, although the average DRE for the Permian Basin was 91.7% for lit, active flares.
(Pilot) Light’s Out
These figures exclude emissions from flares that were operational but remained unlit. A previous study of the Permian Basin using airborne optical gas imaging found that, on average, 4.9% of the flares were unlit and venting gas[1]. In the Bakken, the researchers for the Science article conducted a ground-based infrared imaging survey of 601 active flares and found that 3.2% of these flares were not lit. Owing to the lack of survey data the authors averaged the Permian and Bakken results (4.1% unlit) for the Eagle Ford. The data for both operating and unlit flares for each basin are shown in the following table.
[1] D.R. Lyon et al., Atmospheric Chemistry & Physics 21, 6605-6626 (2021).
The chart below summarizes the results by basin.
Direct measurements of flare efficiency demonstrate that DRE observed in the field is lower than the 98% DRE assumed by EPA in every basin surveyed. In fact, the contribution of methane emissions from flares operating at less than 98% efficiency and unlit flares venting to the atmosphere is substantially similar, with the authors estimating 270,000 MT/yr from inefficient flares and 220,000 MT/yr from unlit flares. These estimates are roughly five times the vented volume estimated using a 98% DRE for methane with all flares operational.
The study estimates: “If measures were taken to ensure that US flares operated at 98% efficiency and remained lit, as current accounting assumes, this would be equivalent to removing 2.9 million cars from the road each year these mitigation measures were in place.”
Capturing is the Solution
Gas capture along with other methods was recognized as a simple and cost-effective methane mitigation opportunity. By capturing 100% of the gas stream, including flash gas and tank vapors, oil & gas operators can simultaneously reduce tank flaring and venting emissions and generate an incremental revenue stream, conserving a valuable resource.
EcoVapor works with gas capture of low-pressure vapor such as that generated in atmospheric storage tank batteries, converting waste gas into revenue and eliminating flaring emissions.
About EcoVapor
EcoVapor, a DNOW company, provides gas treating solutions to both geologic and biogas production problems. Our fleet of proprietary ZerO2 oxygen removal (deoxo) units has grown to a fleet of nearly 250 since 2010, operating reliably for leading producers in all major U.S. basins. ZerO2 technology helps Oil & Gas and biogas producers convert waste gas streams into revenue by treating gas to meet pipeline specifications so it can be sold instead of vented or flared, generating incremental value while reducing emissions and improving environmental performance.
EcoVapor is headquartered in Denver, Colorado and has field locations in Greeley, Colorado and Midland, Texas.
Contact
EcoVapor Recovery Systems (a DNOW Company)
Email: ecovapor.info@dnow.com
Phone: 844-NOFLARE (844-663-5273)
Sales: Joe Hedges (281-615-2072)