Methane quantification of LNG gas-fired power plant in Seoul, South Korea

Abstract

Methane emissions from a liquefied natural gas (LNG) gas-fired power plant in Seoul, South Korea were measured using a mobile greenhouse gas measurement platform. Twenty-one mobile measurements were conducted between February and 12 July 2023. The Gaussian Plume Dispersion Model and the OTM-33A method were used to quantify fugitive methane emissions from mobile measurements in order to compare them with estimated fugitive methane emissions from the bottom-up approach. The measurements identified three key emission hotspots: S1 and S2 were attributed to continuous fugitive methane leaks from underground pipeline, whereas S3 was identified as a stochastic super-emitter likely caused by incomplete combustion or pressure relief venting from the facility's exhaust. The average methane emission rates were 90 ± 9, 18 ± 2, and 550 ± 58 kgh-1 at S1, S2, and S3, respectively. Notably, S3 had a significant methane emission rate of 2053 ± 283 kgh-1, approximately 6 times greater than our corresponding bottom-up estimate of fugitive methane emissions (350 kgh-1). This significant discrepancy arises because bottom-up inventories rely on aggregated monthly fuel consumption data and static emission factors. These inventories are unable to capture intermittent, high-emission events like S3. Our snapshot measurements highlight this temporal variability, demonstrating that mobile measurement is an effective approach for identifying specific sources of methane emissions in Seoul, especially for facilities with strict access restrictions. Furthermore, assuming the maximum rate as a continuous event, we estimated a potential upper-bound annual financial loss of approximately USD 15.77 million, highlighting the economic necessity of improved leak detection and repair (LDAR). These findings are essential for developing a more precise understanding of effective methods to reduce methane emissions from these facilities.