Determination of methane during anaerobic digestion by tunable diode laser absorption spectroscopy (TDLAS)

Abstract

This paper presents the design and application of a near-infrared laser absorption-based sensor for methane measurements during anaerobic digestion using an optical probe inserted into an anaerobic tank reactor. The wavelength of the laser was scanned across the absorption lines of methane near 1.65 µm to provide the real-time concentration. A probe was designed for optical measurement. This technique was validated by measuring methane in the laboratory and anaerobic digestion tank reactor. A set of reference values spanning from 30 to 52%, covering the typical concentrations during anaerobic digestion, were measured to validate the reliability of the system. The spectrometrically derived methane concentrations showed high consistency with the reference values, and an R² of 0.999 revealed that the system was reliable. In addition, the detection limit was estimated by the uncertainty of the intercept to be 0.27% with an accuracy of 0.1% and a temporal resolution of 1 s.

Keywords:

• Anaerobic digestion
• methane
• optical probe
• spectroscopy
• tunable diode laser absorption spectroscopy (TDLAS)

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Key R & D Program of China (Number 2019YFC1907000); National Natural Science Foundation of China (Number 51976188); Science and Technology Plan Project of Zhejiang Province (Number 2021C03162, 2022C03092); and Key Project of Innovation of Science and Technology of Ningbo City (Number 2018B10023).