Characterization of trace compounds of the biomethanes injected in the French gas network: complementary analytical methods

Authors:
  • BSBeatrice Sanz
    Beatrice Sanz
  • ALAmélie Louvat
    Amélie Louvat
  • DVDjimmy Vorin
    Djimmy Vorin
  • LDLucie Dupré
    Lucie Dupré
  • LCLorena Cuccia
    Lorena Cuccia
  • ZDZoé Disdier
    Zoé Disdier
  • MPMaïlys Pale-Guerquin
    Maïlys Pale-Guerquin
  • ETEmmanuel Tena
    Emmanuel Tena
  • LJLéa Josi
    Léa Josi
  • GCGuilhem Caumette
    Guilhem Caumette
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Abstract
NaTran R&I launched the CARABIO project in 2016 to characterize biomethanes from methanization injected into the national gas network, aiming at addressing the knowledge gap in the composition of trace compounds. Between 2016 and 2023, 75 biomethane sampling and analysis campaigns were conducted at 40 injection plants, reflecting the variety of feedstocks and upgrading technologies in France. The investigations carried out required a unique analytical development work.Across 75 Gas Chromatography-Mass Spectrometry screenings, 530 trace compounds were semi-quantified. Of these, 100 were detected at least ten times, while 207 appeared only once. On average, biomethane contained 48 trace compounds, predominantly hydrocarbons. For organo-oxygenated compounds, terpenes, sulfur compounds, organo-halogens, siloxanes and amines, 87% of average concentrations were below 0.1 mg/m³(n) by compound, with maximum 0.35 mg/m³(n).Quantitative analyses were performed using micro-Gas Chromatography – Thermal Conductivity for monoaromatic hydrocarbons and terpenes, Gas Chromatography-Pulsed Flame Photometry for sulfur compounds, absorption spectroscopy for ammonia, Inductively Coupled Plasma-Mass Spectrometry for metals, and atomic fluorescence spectrometry for mercury. A statistical assessment seeking correlations between trace compounds, feedstocks, and upgrading processes revealed no clustering, indicating good overall homogeneity of biomethane quality.Levels for comparable compound families were lower than those in natural gas, and no trace compound reached concentrations that could pose risks to gas infrastructures or end-users, confirming biomethane’s suitability as a renewable energy source.