Enhancing anaerobic methane production in the co-presence of PLA, TPS, and PBAT mixed under hydrogen-rich conditions

초록

Methane (CH4) production was compared during mesophilic anaerobic digestion (AD) under H2/CO2 purged versus N2 purged, investigating the biodecomposition of polylactic acid (PLA), thermoplastic starch (TPS), and polybutylene adipate terephthalate (PBAT) as the co-presence of PLA/TPS (LS), TPS/PBAT (SB), PLA/PBAT (LB), and PLA/TPS/PBAT (LSB). Therein, 427.37 and 339.22 mL CH4/g volatile solid (VS) were produced endogenously under H2/CO2 and N2 purged, respectively. CH4 production from LS and SB was further increased from 170 to 193 mL CH4/g VS compared to the respective control samples. The degradation of LB and LSB resulted in significantly higher CH4 production under H2/CO2 (157.49 and 229.21 mL CH4/g VS) than under N2 (106.88 and 119.63 mL CH4/g VS, respectively). Metagenome sequencing revealed that H2/CO2 purged led syntrophs of hydrogenotrophic methanogens (e.g., Firmicutes) overcoming higher strengths of fatty acids and utilizing H2 to produce more CH4. Subsequently, PLA and PBAT exhibited breakdowns in the polymer chains and molecular weight along with increased crystallinity. This was confirmed through Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). This study highlights the critical roles of co-digestion with H2 and bioplastics in increasing CH4 production in the AD system.

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