A selective laser-based sensor for fugitive methane emissions

Mhanna Mhanna; Mohamed Sy; Aamir Farooq

doi:10.1038/s41598-023-28668-z

A selective laser-based sensor for fugitive methane emissions

Sci Rep. 2023 Jan 28;13(1):1573. doi: 10.1038/s41598-023-28668-z.

Authors

Mhanna Mhanna¹, Mohamed Sy¹, Aamir Farooq²

Affiliations

¹ Mechanical Engineering Program, Physical Science and Engineering Division, Clean Combustion Research Center, King Abdullah University of Science and Technology (KAUST), 23955-6900, Thuwal, Saudi Arabia.
² Mechanical Engineering Program, Physical Science and Engineering Division, Clean Combustion Research Center, King Abdullah University of Science and Technology (KAUST), 23955-6900, Thuwal, Saudi Arabia. aamir.farooq@kaust.edu.sa.

Abstract

A mid-infrared laser-based sensor is reported for the quantification of fugitive methane emissions. The sensor is based on a distributed feedback inter-band cascade laser operating near 3.3 μm. Wavelength tuning with cepstral analysis is employed to isolate methane absorbance from (1) fluctuations in the baseline laser intensity, and (2) interfering species. Cepstral analysis creates a modified form of the time-domain molecular free-induction-decay (m-FID) signal to temporally separate optical and molecular responses. The developed sensor is insensitive to baseline laser intensity imperfections and spectral interference from other species. Accurate measurements of methane in the presence of a representative interfering species, benzene, are performed by careful selection of the scan index (ratio of laser tuning range to spectral linewidth) and initial and final time of m-FID signal fitting. The minimum detection limit of the sensor is ~ 110 ppm which can be enhanced with an optical cavity. The proposed sensing strategy can be utilized to measure methane leaks in harsh environments and in the presence of interfering species in environment-monitoring applications.