Determining Biogenic Content of Biogas by Measuring Stable Isotopologues 12CH₄, 13CH₄, and CH₃D with a Mid-Infrared Direct Absorption Laser Spectrometer.

Albert Manninen,Craig Richmond,Teemu Kääriäinen

doi:10.3390/s18020496

Abstract

A tunable laser absorption spectrometer (TLAS) was developed for the simultaneous measurement of δ13C 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 δ13C and δD values were determined. Analysis demonstrated that, provided the isotopic composition of the source materials was known, the δ13C and δD values alone were sufficient to determine the biogenic content of the blended samples to within 1.5%.

Highlights

As the utilisation of renewable energy sources increases globally, the safe and efficient integration of biofuels into existing energy infrastructures becomes pertinent
Analysis demonstrated that, provided the isotopic composition of the source materials was known, the δ13 C and δD values alone were sufficient to determine the biogenic content of the blended samples to within 1.5%
The need to validate the biogenic content of gas samples consisting of blended biomethane and natural gas is included in such regulatory framework

Summary

Introduction

As the utilisation of renewable energy sources increases globally, the safe and efficient integration of biofuels into existing energy infrastructures becomes pertinent. Biogas is one such renewable energy source, with the potential to replace fossil fuels for applications such as power production and transportation fuel. Due to increasing European biogas production [2,3], and to support the use of green gas, the European Committee for Standardization (CEN) has worked to establish technical specifications for both biogas (a mixture of methane and other gases, such as CO2 ). Biomethane (purified biogas with higher methane content), with the aim of allowing safe injection to the natural gas distribution grids, and for use as a fuel for vehicle engines [4]. As fossil samples are free of 14 C, the measured

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Conclusion