In-situ biogas upgrading with pulse H 2 additions: The relevance of methanogen adaption and inorganic carbon level

Biogas upgrading and utilization: Current status and perspectives

“…As a consequence, the system could become imbalanced or even, in the worst case, can totally be fatally deteriorated due to excess acidification caused by VFA accumulation. A recent study concluded that the injection of H 2 in batch reactors at a concentration that exceeds the stoichiometric amount for hydrogenotrophic methanogenesis led to an accumulation of acetate, which could be attributed to stimulated homoacetogenic pathway, and/or decreased methanogenic activity of acetoclastic archaea (Agneessens et al, 2017). However, after longer term H 2 exposure, increase of the hydrogenotrophic population enhances the H 2 -utilization capacity and reverts the inhibition (Reeve et al, 1997).…”

“…For that reason, the material and type of the module that is used to inject H 2 , the application of gas recirculation flows and the reactor designs are considered as fundamental elements for the implementation of sufficient in-situ biogas upgrading (Bassani et al, 2016). In batch experiments, it was found that the H 2 uptake rate decreased rapidly at CO 2 concentrations < 12% (Agneessens et al, 2017) and the maximum CH 4 content in biogas reached 89% (Mulat et al, 2017). On contrary in continuously fed reactors, Luo and Angelidaki (2013b) who used hollow fiber membranes to inject H 2 in an anaerobic reactor treating cattle manure and cheese whey, achieved up to 96% methane at the final output gas.…”

“…Microbial analysis performed during biogas upgrading, revealed that the most frequently found hydrogenotrophic methanogenic genera were Methanobacterium, Methanoculleus, Methanomicrobium and Methanothermobacter (Agneessens et al, 2017;Bassani et al, 2017;Luo and Angelidaki, 2013a;Mulat et al, 2017), whereas Methanosarcina and, more generally, acetoclastic methanogens are usually present at lower abundance (Agneessens et al, 2017;Bassani et al, 2015;Mulat et al, 2017). Methanobacterium and Methanothermobacter species were found to be dominant in various biogas upgrading configurations (i.e.…”

“…In fact, Reeve and colleagues found a decreased growth yield (Y CH4 ) of M. thermoautotrophicum at high H 2 concentration (expressed as grams of biomass synthesized per mole of CH 4 produced), which was partially attributed to the transcriptional activity of some specific genes involved in methanogenesis (Reeve et al, 1997). Due to the difficulty in isolation and cultivation of methanogens and syntrophic bacterial species, most of the studies recently performed on these microbial communities were performed using high throughput 16S rRNA amplicon sequencing (Agneessens et al, 2017;Bassani et al, 2017;Kougias et al, 2017b;Mulat et al, 2017). It has been shown that H 2 addition has multiple effects on the microbial species and it can influence not only species abundance but also their transcriptional activity (Reeve et al, 1997).…”

Bioelectrochemical CO2 Reduction to Methane: MES Integration in Biogas Production Processes

“…Electrochemical studies combining anaerobic digestion (AD) units have been demonstrated with both processes taking place in a single reactor [19]. A few researchers have suggested combining AD and microbial electrolysis cells (MECs) as two separate units where the MECs were used for in-situ hydrogen gas injection into AD reactors for biogas enrichment [20][21][22][23]. Several studies on biogas upgrading technologies using in situ and/or ex situ hydrogen gas injection have been discussed by Aryal et al, 2018 [24].…”