A Novel and Efficient Optical Device for Mitigating Methane Emission Risks in Geological and Built-in Environment

Abstract

Methane, the most deleterious greenhouse gas causes multi-dimensional damage footprint from local to global scales. This necessitates detection of its source and quantifying of its concentration. Widely used compact chemical sensors are sensitive to broad-spectrum of gases, degrade fast and slow in response. Which limits its efficiency in tracing its sources within geological/mine/reclaimed and built-in environments. Contrary, optical sensors are very fast, precisely measures the methane concentration and its flux, and deployable in above mentioned environments. Conventionally, costly InGaAs sensors are used in optical-detectors due to its sensitivity in near Infra-red region (1000–2500 nm). Here, we report development of an efficient spectroscopy-based cost-effective sensor which is methane specific, fast response time and has tremendous application potential in tracking the methane source in above environments. The detector, NiSi Schottky diode, was designed, fabricated, and characterized exclusively for the 1.65 µm, narrow bandwidth methane absorption wavelength. The sensor system, which is of 20 cm length includes a laser source and the NiSi detector. This probe can be easily deployed in boreholes, mine vents and soil layers for measuring real-time fluxes in methane concentrations. From the experiments it is observed that the detection limits of the developed device are very low (3% by volume) and the response time of detection is about 2 seconds. Based on the materials used, fabrication procedures adopted, sensitivity of the device and its compactness, the developed device can be considered as a novel, economic device for effectively measuring and targeting the methane source in above mentioned environment.