Microbial community development during syngas methanation in a trickle bed reactor with various nutrient sources

Abstract

Microbial community development within an anaerobic trickle bed reactor (TBR) during methanation of syngas (56% H2, 30% CO, 14% CO2) was investigated using three different nutrient media: defined nutrient medium (241 days), diluted digestate from a thermophilic co-digestion plant operating with food waste (200 days) and reject water from dewatered digested sewage sludge at a wastewater treatment plant (220 days). Different TBR operating periods showed slightly different performance that was not clearly linked to the nutrient medium, as all proved suitable for the methanation process. During operation, maximum syngas load was 5.33 L per L packed bed volume (pbv) & day and methane (CH4) production was 1.26 L CH4/Lpbv/d. Microbial community analysis with Illumina Miseq targeting 16S rDNA revealed high relative abundance (20–40%) of several potential syngas and acetate consumers within the genera Sporomusa, Spirochaetaceae, Rikenellaceae and Acetobacterium during the process. These were the dominant taxa except in a period with high flow rate of digestate from the food waste plant. The dominant methanogen in all periods was a member of the genus Methanobacterium, while Methanosarcina was also observed in the carrier community. As in reactor effluent, the dominant bacterial genus in the carrier was Sporomusa. These results show that syngas methanation in TBR can proceed well with different nutrient sources, including undefined medium of different origins. Moreover, the dominant syngas community remained the same over time even when non-sterilised digestates were used as nutrient medium. Key points •Independent of nutrient source, syngas methanation above 1 L/Lpbv/D was achieved. •Methanobacterium and Sporomusa were dominant genera throughout the process. •Acetate conversion proceeded via both methanogenesis and syntrophic acetate oxidation. Graphical abstract

Enrichment of Microbial Consortium with Hydrogenotrophic Methanogens for Biological Biogas Upgrade to Biomethane in a Bubble Reactor under Mesophilic Conditions

“…Such cases include the stress induced by high ammonia concentration [60,61], high butyrate concentration [62], and high organic loading rate [63]. The co-existence of hydrogenotrophic methanogens (e.g., Methanobacterium), homoacetogens (e.g., Sporomusa), and SAO (e.g., Spirochaetaceae) has also been reported elsewhere (e.g., syngas fermentation [64]).…”

Pilot-scale study of biomethanation in biological trickle bed reactors converting impure CO2 from a Full-scale biogas plant

“…They reported CH 4 production capacity of 15.4 Nm 3 m − 3 d − 1 with 98 % CH 4 at the reactor outlet. Recent studies from Tsapekos et al (2021) and Cheng et al (2022) used a semi pilot-scale trickle bed reactor with a packed volume of 68 L and 35 L. However, the focus in both studies was on the microbial communities applying metagenomics and the reactors were operated at low gas feed rates. Asimakopoulos et al (2021) conducted a scale up study for syngas biomethanation in semi-pilot trickle bed reactor with a packed volume of 5 L. They reported 100 % H 2 conversion and CH 4 production capacity of 5.7 Nm 3 m − 3 d − 1 at a gas retention time (GRT) of 0.6 h.…”

“…A pilot scale biomethanation system consisting of two 1 m 3 BTF reactors was designed and built. This upscaling of biomethanation was a 15-fold increase from the study of Cheng et al (2022) and a 69-fold increase from the laboratory scale of Lemmer and Ullrich (2018). The pilot BTFs was placed in a full-scale biogas plant utilizing raw biogas to show the real potential of this technology.…”

Effect of Inoculum Microbial Diversity in Ex Situ Biomethanation of Hydrogen

“…Recent biomethanation studies have identified the pathways under mesophilic and thermophilic conditions [ 54 ], combined experimental and model data to dissect the competition between methanogens and homoacetogens [ 55 ], determined how functional redundancy leads to quick recovery of the methane production rate [ 24 ], analyzed the carbon flow during methanogenesis inhibition [ 20 ], and revealed microbial community changes during syngas biomethanation in trickle bed reactors with different nutrient sources, including non-sterile digestates [ 56 ]. The enhancement of the process can be achieved by addition of zero valent iron (ZVI) [ 57 ], by introducing micro-porous materials as enhancer of biofilm immobilization and hydrogen mass transfer during ex situ biomethanation in trickle bed reactors [ 58 ] or via bioaugmentation with hydrogenotrophic methanogens ( Methanoculleus bourgensis and Methanothermobacter thermautotrophicus) as active microbial resource management during mesophilic and thermophilic in situ biomethanation [ 59 ].…”