In-Situ Testing of Methane Emissions from Landfills Using Laser Absorption Spectroscopy

Abstract

Field monitoring of methane emissions from landfills is of great importance for both environmental concern and economic benefit. This study presents a highly effective method to measure methane emissions from landfills based on tunable diode laser absorption spectroscopy (TDLAS). Methane concentration is obtained by analyzing the absorption spectrum of the laser after passing through the landfill gas. The relationship between methane concentration and the optical signal was calibrated in the laboratory. As the methane concentration increased from 400 ppm to 5000 ppm, the absorption spectrum amplitude increased linearly from 0.0005 to 0.0046. In situ testing of methane emissions at a large-scale landfill in China demonstrated the accuracy of the TDLAS method. The methane concentrations in the well-covered areas were generally below 100 ppm. In the working area or the coverage area with holes, the methane concentration was about 700 ppm. The methane concentration was up to 1900 ppm, where the gas collection pipe is disconnected. Due to to the accuracy and simplicity, the TDLAS method is suitable to detect methane emissions on a large-scale from landfills.

Voc Detections With Optical Spectroscopy

“…7. An Allan deviation analysis yielded a detection sensitivity of 76.75 ppb during an average time of 340 s. As an application of the TDLAS method in the range of mid-infrared, co-author Shen et al [35] developed a TDLAS sensor based on a continuous-wave external-cavity quantum cascade laser (EC-QCL) operating in 8 µm for real-time on-line monitoring of N2O.The TDLAS method can remotely monitor the trace gas concentration as reported by He et al [36]. A compact remote sensor for measuring the methane concentration was developed based on the tunable diode laser absorption spectroscopy as shown in Fig.…”

Methane and ethane detection from natural gas level down to trace concentrations using a compact mid-IR LITES sensor based on univariate calibration

“…Several gas sensors for hydrocarbons detection were developed employing optical-based detection techniques. These sensors were mainly operate for methane and ethane detection in trace concentrations for environmental monitoring purposes, exploiting spectroscopic methods as cavity-based techniques [13] , [14] , non-dispersive infrared sensors [15] , [16] , photoacoustic spectroscopy [17] , [18] , [19] , photothermal spectroscopy [20] , [21] , and tunable diode laser absorption spectroscopy (TDLAS) [22] , [23] . These optical sensors exploit the absorption features located in the near- and mid-IR and corresponding to the C-H bond stretching, which characterize the absorption spectra of several alkanes and hydrocarbons (fundamental mode lies in λ = 3–4 µm, first overtone in λ = 1–2 µm).…”

Hotspot Detection and Estimation of Methane Emissions from Landfill Final Cover

“…In order to quickly measure the distribution of the methane concentration in a large area, laser absorption spectroscopy has attracted the interest of many scholars [20][21][22]. He et al [23] proposed a highly effective method to measure methane concentrations in landfill sites based on tunable diode laser absorption spectroscopy (TDLAS), and the field results indicated that the TDLAS method was suitable for detecting methane emissions from landfills on a large scale. Aldhafeeri et al [24] pointed out that optical sensors based on laser absorption spectroscopy technology have the advantages of fast testing, a low cost and strong immunity to electromagnetic interference.…”