Modelling methanogenic pathways and community dynamics during anaerobic digestion of municipal solid waste
Résumé
Based on experimental data of mesophilic and thermophilic anaerobic digestion of solids imitating the Chinese and French Municipal Solid Wastes (CMSW and FMSW) a mathematical model was developed to describe dynamics of methanogenic population. Three groups of methanogens were considered in the model including strictly hydrogenotrophic methanogens (Methanoculleus sp.), strictly aceticlastic methanogens (Methanosaeta sp.) and Methanosarcina sp. consuming both acetate and H2 /H2CO3. The growth of these different methanogens was monitored using Fluorescent in situ hybridization. Acetate-oxidizing syntrophs were also included in the model. The batch bottles were studied at water-saturated and unsaturated conditions. Initially, headspaces were purged by inert gas (helium). CMSW and FMSW contained mostly putrescible waste (PSW) as well as cellulosic material under the form of office paper (OP) and cardboard (CD). Separately, batch biodegradation experiments with OP, CD and PSW were carried out. The total organic (TOC) and inorganic (TIC) carbon concentrations, methane production volume, methane and carbon dioxide partial pressures values were used for the model calibration and validation. Moreover, in order to differentiate methane produced by hydrogenotrophic and aceticlastic pathways, we included the equations representing the evolution of isotopic 13C composition of methane that was followed by GC-IRMS analysis. Inhibition of the stages of hydrolysis/acidogenesis and aceticlastic methanogenesis by high value of non-ionized or total VFA concentrations was taken into account. A comparatively good fit of the model to experimental data was obtained. (...)