Biological methanation: Strategies for in-situ and ex-situ upgrading in anaerobic digestion.
- Resource Type
- Article
- Authors
- Voelklein, M.A.; Rusmanis, Davis; Murphy, J.D.
- Source
- Applied Energy. Feb2019, Vol. 235, p1061-1071. 11p.
- Subject
- *ANAEROBIC digestion
*METHANATION
*BIOGAS
*BIOMASS chemicals
*GASES
*BIOGAS production
- Language
- ISSN
- 0306-2619
Highlights • Biological methanation was assessed in-situ and ex-situ. • A 24-hour batch ex-situ system produced 3.7 L CH 4 L VR −1 d−1 at 96% methane content. • High hydrogen loadings boost performance while adversely affecting efficiency. • Elevated hydrogen concentrations hamper in-situ acetogenesis process. • Concepts for full-scale methanation strategies are proposed to upgrade biogas. Abstract This study investigated in-situ and ex-situ biological methanation strategies for biogas upgrading potential. The addition and circulation of hydrogen with a ceramic gas diffuser unit revealed positive effects on the methanogenic process. A short-term maximum methane productivity of 2.5 L CH 4 per L reactor volume per day (L VR −1 d−1) was obtained in-situ. Adverse effects of elevated dissolved hydrogen concentrations on acetogenesis became evident. Ex-situ methanation in a reactor subjected to gas recirculation for recurrent 24 h periods achieved methane formation rates of 3.7 L CH 4 L VR −1 d−1. A biomethane with methane concentrations in excess of 96% successfully demonstrated the potential for gas grid injection. A theoretic model supplying gases continuously into a sequential ex-situ reactor system and steadily displacing the upgraded biogas confirmed similar methane formation performance and was advanced to a full-scale concept. Gas conversion efficiency of 95% producing biomethane at 85% methane content was attained. A hybrid model, where an in-situ grass digester is followed by an ex-situ reactor, is proposed as a novel upgrading strategy. [ABSTRACT FROM AUTHOR]