A Critical Assessment of Microbiological Biogas to Biomethane Upgrading Systems

Rittmann, Simon K.-M. R.

doi:10.1007/978-3-319-21993-6_5

Cited by 34 publications

(21 citation statements)

References 40 publications

(100 reference statements)

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“…According to Kougias et al [10] and Rittmann [11], biomethanation of H 2 can be done in three ways: in situ, ex situ and by a hybrid process. In the in situ process, H 2 is injected into the main anaerobic digester or post-digester of a biogas plant to reduce CO 2 and thereby increase the CH 4 content of the biogas.…”

Section: Introductionmentioning

confidence: 99%

Microbial Resource Management for Ex Situ Biomethanation of Hydrogen at Alkaline pH

et al. 2020

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Biomethanation is a promising solution to convert H2 (produced from surplus electricity) and CO2 to CH4 by using hydrogenotrophic methanogens. In ex situ biomethanation with mixed cultures, homoacetogens and methanogens compete for H2/CO2. We enriched a hydrogenotrophic microbiota on CO2 and H2 as sole carbon and energy sources, respectively, to investigate these competing reactions. The microbial community structure and dynamics of bacteria and methanogenic archaea were evaluated through 16S rRNA and mcrA gene amplicon sequencing, respectively. Hydrogenotrophic methanogens and homoacetogens were enriched, as acetate was concomitantly produced alongside CH4. By controlling the media composition, especially changing the reducing agent, the formation of acetate was lowered and grid quality CH4 (≥97%) was obtained. Formate was identified as an intermediate that was produced and consumed during the bioprocess. Stirring intensities ≥ 1000 rpm were detrimental, probably due to shear force stress. The predominating methanogens belonged to the genera Methanobacterium and Methanoculleus. The bacterial community was dominated by Lutispora. The methanogenic community was stable, whereas the bacterial community was more dynamic. Our results suggest that hydrogenotrophic communities can be steered towards the selective production of CH4 from H2/CO2 by adapting the media composition, the reducing agent and the stirring intensity.

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Section: Introductionmentioning

confidence: 99%

Microbial Resource Management for Ex Situ Biomethanation of Hydrogen at Alkaline pH

et al. 2020

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“…Biological biogas upgrading can be implemented either in situ, where H 2 is directly injected into anaerobic digesters or ex situ, where upgrading occurs in a separate reactor containing enriched cultures of hydrogenotrophic methanogens [8, 15–17]. Both approaches have allowed increases in CH 4 content up to 90% and higher [2, 11].…”

Section: Introductionmentioning

confidence: 99%

Effects of H2:CO2 ratio and H2 supply fluctuation on methane content and microbial community composition during in-situ biological biogas upgrading

Wahid

Mulat

Gaby

et al. 2019

Biotechnol Biofuels

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Background Commercial biogas upgrading facilities are expensive and consume energy. Biological biogas upgrading may serve as a low-cost approach because it can be easily integrated with existing facilities at biogas plants. The microbial communities found in anaerobic digesters typically contain hydrogenotrophic methanogens, which can use hydrogen (H 2 ) as a reducing agent for conversion of carbon dioxide (CO 2 ) into methane (CH 4 ). Thus, biological biogas upgrading through the exogenous addition of H 2 into biogas digesters for the conversion of CO 2 into CH 4 can increase CH 4 yield and lower CO 2 emission. Results The addition of 4 mol of H 2 per mol of CO 2 was optimal for batch biogas reactors and increased the CH 4 content of the biogas from 67 to 94%. The CO 2 content of the biogas was reduced from 33 to 3% and the average residual H 2 content was 3%. At molar H 2 :CO 2 ratios > 4:1, all CO 2 was converted into CH 4 , but the pH increased above 8 due to depletion of CO 2 , which negatively influenced the process stability. Additionally, high residual H 2 content in these reactors was unfavourable, causing volatile fatty acid accumulation and reduced CH 4 yields. The reactor microbial communities shifted in composition over time, which corresponded to changes in the reactor variables. Numerous taxa responded to the H 2 inputs, and in particular the hydrogenotrophic methanogen Methanobacterium increased in abundance with addition of H 2 . In addition, the apparent rapid response of hydrogenotrophic methanogens to intermittent H 2 feeding indicates the suitability of biological methanation for variable H 2 inputs, aligning well with fluctuations in renewable electricity production that may be used to produce H 2 . Conclusions Our research demonstrates that the H 2 :CO 2 ratio has a significant effect on reactor performance during in situ biological methanation. Consequently, the H 2 :CO 2 molar ratio should be kept at 4:1 to avoid process instability. A shift toward hydrogenotrophic methanogenesis was indicated by an increase in the abundance of the obligate hydrogenotrophic methanogen Methanobacterium . ...

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“…The partial pressure of a gas can be varied either by changing the concentration of the reactant gas or by changing the operation pressure in the reactor. Utilizing these modifications to increase the partial pressure will result in positively influencing the concentration gradient .…”

Section: Introductionmentioning

confidence: 99%

Development of a simultaneous bioreactor system for characterization of gas production kinetics of methanogenic archaea at high pressure

Pappenreiter

Zwirtmayr

Mauerhofer³

et al. 2019

Engineering in Life Sciences

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Cultivation of methanogens under high pressure offers a great opportunity in biotechnological processes, one of which is the improvement of the gas‐liquid transfer of substrate gases into the medium broth. This article describes a newly developed simultaneous bioreactor system consisting of four identical cultivation vessels suitable for investigation of microbial activity at pressures up to 50 bar and temperatures up to 145°C. Initial pressure studies at 10 and 50 bar of the autotrophic and hydrogenotrophic methanogens Methanothermobacter marburgensis, Methanobacterium palustre, and Methanobacterium thermaggregans were performed to evaluate the reproducibility of the system as well as to test the productivity of these strains. The strains were compared with respect to gas conversion (%), methane evolution rate (MER) (mmol L‐1 h−1), turnover rate (h−1), and maximum conversion rate (kmin) (bar h−1). A pressure drop that can be explained by the reaction stoichiometry showed that all tested strains were active under pressurized conditions. Our study sheds light on the production kinetics of methanogenic strains under high‐pressure conditions. In addition, the simultaneous bioreactor system is a suitable first step screening system for analyzing the substrate uptake and/or production kinetics of gas conversion and/or gas production processes for barophilic or barotolerant microbes.

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A Critical Assessment of Microbiological Biogas to Biomethane Upgrading Systems

Cited by 34 publications

References 40 publications

Microbial Resource Management for Ex Situ Biomethanation of Hydrogen at Alkaline pH

Microbial Resource Management for Ex Situ Biomethanation of Hydrogen at Alkaline pH

Effects of H2:CO2 ratio and H2 supply fluctuation on methane content and microbial community composition during in-situ biological biogas upgrading

Development of a simultaneous bioreactor system for characterization of gas production kinetics of methanogenic archaea at high pressure

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