Abstract

To optimize commercial-scale biogas production, it is important to evaluate the performance of each microbial step in the anaerobic process. Hydrolysis and methanogenesis are usually the rate-limiting steps during digestion of organic waste and by-products. By measuring biogas production and methane concentrations on-line in a semi-continuously fed reactor, gas kinetics can be evaluated. In this study, the rate constants of the fermentative hydrolysis step (k(c)) and the methanogenesis step (k(m)) were determined and evaluated in a continuously stirred tank laboratory-scale reactor treating food and slaughterhouse waste and glycerin. A process additive containing Fe2+, Co2+ and Ni2+ was supplied until day 89, after which Ni2+ was omitted. The omission resulted in a rapid decline in the methanogenesis rate constant (k(m)) to 70% of the level observed when Ni2+ was present, while kc remained unaffected. This suggests that Ni2+ mainly affects the methanogenic rather than the hydrolytic microorganisms in the system. However, no effect was initially observed when using conventional process monitoring parameters such as biogas yield and volatile fatty acid concentration. Hence, formation rate constants can reveal additional information on process performance and km can be used as a complement to conventional process monitoring tools for semi-continuously fed anaerobic digesters.

Keywords

anaerobic digestion; kinetics; rate constants; trace elements; nickel

Published in

Energies
2015, Volume: 8, number: 1, pages: 645-655
Publisher: MDPI AG

SLU Authors

• Moestedt, Jan

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    
  • Tekniska verken i Linköping AB

UKÄ Subject classification

Bioenergy


Publication identifier

DOI: https://doi.org/10.3390/en8010645

Permanent link to this page (URI)

https://res.slu.se/id/publ/76153