Improving the active AirCore system to determine the destruction rate efficiency of gas flares in the Netherlands

Avoiding unnecessary methane (CH₄) emissions is an easy way to mitigate the effects of
climate change, since methane has a higher global warming potential and a shorter lifetime
compared to carbon dioxide (CO₂) and often no purpose is served with the flaring. Flaring is
the disposal of associated gas by combustion. In some cases, the flaring is unavoidable to
ensure the safety of the personnel, while in other instances flaring can easily be avoided,
resulting in unnecessary emissions. Yearly, approximately 140 billion cubic meters is flared
globally. With a destruction rate efficiency (DRE) of 98%, this results in yearly GHGs emission
of 315 Mt of CO₂ and 1.4 Mt of CH₄ (or 315 Mt and 42 Mt of CO₂ equivalent). It is speculated
that the DRE of flares in operation is generally lower. For example, Plant et al. 2022 found a
DRE of 91% across three oil basins in the United States using an aircraft-based study.
However, there is still a lack of experimental data from other countries and on facility-scale.
In this research, the active AirCore system described by Andersen et al. 2018 was improved
and used to determine the flaring efficiency from gas flares in the Netherlands. An in-situ
CO₂ sensor was added to obtain an in-flight signal allowing to reliably sample the entire
cross section of the plume. To test the system, it was used during two separate campaigns
in the Netherlands. The flaring (by a Dutch national gas grid operator) is a routine part of
scheduled infrastructure maintenance. The operator’s mobile flaring unit has been
specifically designed for high-efficiency combustion. In the flare plume, we observed a DRE
of 99.7% ± 0.2%. However, the last 1.2 bar absolute (of 40) that remains in the gas pipes is
vented and decreases the methane emission mitigation efficacy (MEME) of the operator’s
procedure with 3%. Additionally, using the in-situ sensor we were able to determine the CO₂
fluxes from flaring during the campaigns which equated to a CH₄ burn rate of 1240 ± 300
m³/h over three different flights, which agrees with the nominal burn rate of 1200 m³/h. This
shows that the system can characterize flaring efficiency and emissions well, which provides
us the capability to use the system in future flaring campaigns where the gas flushing rate is
still unknown.

References
Andersen, T., Scheeren, B., Peters, W., Chen, H. (2018). A UAV-based active Aircore system for
measurements of greenhouse gases. Atmos. Meas. Tech., 11, 2683-2699,
https://doi.org/10.5194/amt-11-2683-2018
Plant, G., Kort, E. A., Brandt, A. R., Chen, Y., Fordice, G., Gorchov Negron, A. M., Schwietzke, S.,
Smith, M., & Zavala-Araiza, D. (2022). Inefficient and unlit natural gas flares both emit large
quantities of methane. Science, 377(6614), 1566–1571. https://doi.org/10.1126/science.abq0385