Determining biogenic content of biogas by measuring stable isotopologues 12CH4, 13CH4, and CH3D with a mid-infrared direct absorption laser spectrometer

Teemu Kääriäinen, Craig A. Richmond, Albert Manninen

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    Abstract

    A tunable laser absorption spectrometer (TLAS) was developed for the simultaneous measurement of δ 13C and δD values of methane (CH₄). A mid-infrared interband cascade laser (ICL) emitting around 3.27 µm was used to measure the absorption of the three most abundant isotopologues in CH₄ with a single, mode-hop free current sweep. The instrument was validated against methane samples of fossil and biogenic origin with known isotopic composition. Three blended mixtures with varied biogenic content were prepared volumetrically, and their δ 13C and δD values were determined. Analysis demonstrated that, provided the isotopic composition of the source materials was known, the δ 13C and δD values alone were sufficient to determine the biogenic content of the blended samples to within 1.5%.

    Original languageEnglish
    Article number496
    JournalSensors
    Volume18
    Issue number2
    DOIs
    Publication statusPublished - 7 Feb 2018
    MoE publication typeA1 Journal article-refereed

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    Keywords

    • Biogas
    • Biogenic determination
    • Bioprocess monitoring
    • Direct absorption
    • Laser-based sensors
    • Stable isotopologues

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