Effects of high-pressure anaerobic digestion up to 30 bar on pH-value, production kinetics and specific methane yield

Publication Type

Journal contribution (peer reviewed)

Authors

Lemmer, A., Merkle, W., Baer, K., Graf, F.

Year of publication

2017

Published in

Energy

Pubisher

Elsevier Ltd

Band/Volume

138/

ISBN / ISSN / eISSN

03605442

DOI

10.1016/j.energy.2017.07.095

Page (from - to)

pp. 659-667

Keywords

Biogas

The production of biogas for combined heat and power generation represents a common method in Germany. An alternative is the purification of biogas to biomethane and injection into the natural gas grid to decouple gas production from usage in terms of space and time. The concept of pressurized two-stage anaerobic digestion integrates biogas production, upgrading and pressure boosting within one process. The increasing solubility of CO₂ in process liquid at high pressures results in high methane contents in gaseous phase and in drop of pH. To investigate the effects of high initial pressures (10, 20, 30 bar) and dissolved CO₂ on pH-value, production kinetics and specific methane yields, pressurized batch methane reactors were built up. Additionally, a method for indirect measuring of pH-value was determined. The results of the experiment showed a decrease in pH from 7 to 6.31 (10 bar) and 6.25 (30 bar). Furthermore, neither a significant influence of initial pressures on the pressure increase nor on the degradation of organics and the specific methane yields was observed. However, the results show that anaerobic digestion at high pressures up to 30 bar might be a promising alternative to post purification and pressure boosting applications. © 2017 Elsevier Ltd