Gabler, Florian
- Department of Energy and Technology, Swedish University of Agricultural Sciences
Abstract
Biomethanation of syngas in trickle-bed reactors (TBRs) presents a promising route for producing renewable methane (CH4), coupled with the gasification of recalcitrant biomass, such as forestry residues. The overall objective of this thesis was to achieve efficient and stable syngas biomethanation in TBRs using liquid organic waste streams as nutrient media by varying process and operational conditions, based on the assessment of CH4 productivity and conversion rates of H2 and CO.
This work presents long-term lab-scale studies (a total of 1,600 days of operation) where mainly digestate and reject water were used as nutrient media to evaluate potential macronutrient limitations, nutrient supply rates, liquid recirculation regimes, and microbial community development. Additionally, the effect of increasing H2 content in syngas to enhance CH4 concentration in the product gas was investigated.
Methane evolution rates up to 4.5 L/(Lpbv·d) were achieved under thermophilic conditions with H2 and CO conversions consistently above 90 %. Adequate phosphorus and sulfur supply, proper nutrient addition, and efficient liquid recirculation were crucial for sustaining high performance, while nutrient limitations or short gas retention times reduced stability and productivity. With an experimental upper limit of 71 % H2 in the syngas, the maximum CH4 concentration reached 65 %. High H2 partial pressures promoted hydrogenotrophic methanogenesis but limited CO conversion.
Despite performance variations, microbial communities remained stable, dominated by Methanothermobacter and supported by syntrophic acetate-oxidizing bacteria, while performance shifts were linked mainly to activity changes rather than community restructuring.
The results highlight the potential of TBRs as a reactor concept for integrating syngas biomethanation into renewable energy systems, while identifying nutrient management, gas–liquid mass transfer optimization, and syngas composition control as key priorities for future development.
Keywords
Biosyngas; Hydrogen; Carbon Monoxide; Reject Water; Digestate; Microbial Community; Biotrickling Filters; E-Methane
Published in
Acta Universitatis Agriculturae Sueciae
2025, number: 2025:87
Publisher: Swedish University of Agricultural Sciences
SLU Authors
UKÄ Subject classification
Bioenergy
Publication identifier
- DOI: https://doi.org/10.54612/a.3m2t1b64np
- ISBN: 978-91-8124-071-9
- eISBN: 978-91-8124-117-4
Permanent link to this page (URI)
https://res.slu.se/id/publ/142488