The University of Southampton
University of Southampton Institutional Repository

Predicting pH rise as a control measure for integration of CO2 biomethanisation with anaerobic digestion

Predicting pH rise as a control measure for integration of CO2 biomethanisation with anaerobic digestion
Predicting pH rise as a control measure for integration of CO2 biomethanisation with anaerobic digestion
In-situ CO2 biomethanisation offers a means to combine biogas upgrading with increased methane productivity, but its potential contribution to power-to-gas is often ignored due to concerns over process stability and control. The research presents an equation derived from fundamental chemical equilibria which predicts the relationship between partial CO2 pressure and digester pH, and allows estimation of the maximum achievable biogas methane content compatible with stable operation. A rapid experimental determination was also developed to support these predictions. The results were validated by long-term experiments using synthetic feedstock with different ammonia concentrations (2 and 3 g N L-1). Further trials carried out using food waste and sewage sludge as substrates showed stable operation at biogas methane contents of 92 and 90 % CH4 and pH 8.5 and 7.9, respectively. CO2 biomethanisation was successfully demonstrated in a food waste digester with a total ammoniacal nitrogen of 4.8 g N L-1 with volumetric methane production enhanced by more than 2 times, from 2.29 to 5.01 L CH4 per L digester per day. The predictive approach used is applicable to digesters fed on different feedstocks and to hybrid systems with biomethanisation of both endogenous and exogenous CO2; and offers a basis for both process design guidelines and operational control. The output from the work thus provides engineers, operators and plant designers with a valuable tool for the successful implementation of in situ biomethanisation in anaerobic digesters.
CO2 biomethanisation, pH rise, Anaerobic digestion, Food waste, Renewable energy, Hydrogenotrophic methanogens
0306-2619
Tao, Bing
a016d442-8190-4f19-b71b-d3f7e4ce357f
Zhang, Yue
69b11d32-d555-46e4-a333-88eee4628ae7
Banks, Charles
5c6c8c4b-5b25-4e37-9058-50fa8d2e926f
Heaven, Sonia
f25f74b6-97bd-4a18-b33b-a63084718571
Tao, Bing
a016d442-8190-4f19-b71b-d3f7e4ce357f
Zhang, Yue
69b11d32-d555-46e4-a333-88eee4628ae7
Banks, Charles
5c6c8c4b-5b25-4e37-9058-50fa8d2e926f
Heaven, Sonia
f25f74b6-97bd-4a18-b33b-a63084718571

Tao, Bing, Zhang, Yue, Banks, Charles and Heaven, Sonia (2020) Predicting pH rise as a control measure for integration of CO2 biomethanisation with anaerobic digestion. Applied Energy, 277. (doi:10.1016/j.apenergy.2020.115535).

Record type: Article

Abstract

In-situ CO2 biomethanisation offers a means to combine biogas upgrading with increased methane productivity, but its potential contribution to power-to-gas is often ignored due to concerns over process stability and control. The research presents an equation derived from fundamental chemical equilibria which predicts the relationship between partial CO2 pressure and digester pH, and allows estimation of the maximum achievable biogas methane content compatible with stable operation. A rapid experimental determination was also developed to support these predictions. The results were validated by long-term experiments using synthetic feedstock with different ammonia concentrations (2 and 3 g N L-1). Further trials carried out using food waste and sewage sludge as substrates showed stable operation at biogas methane contents of 92 and 90 % CH4 and pH 8.5 and 7.9, respectively. CO2 biomethanisation was successfully demonstrated in a food waste digester with a total ammoniacal nitrogen of 4.8 g N L-1 with volumetric methane production enhanced by more than 2 times, from 2.29 to 5.01 L CH4 per L digester per day. The predictive approach used is applicable to digesters fed on different feedstocks and to hybrid systems with biomethanisation of both endogenous and exogenous CO2; and offers a basis for both process design guidelines and operational control. The output from the work thus provides engineers, operators and plant designers with a valuable tool for the successful implementation of in situ biomethanisation in anaerobic digesters.

Text
Revised Main Manuscript - Accepted Manuscript
Restricted to Repository staff only until 30 July 2021.
Request a copy

More information

Submitted date: 6 April 2020
Accepted/In Press date: 15 July 2020
e-pub ahead of print date: 30 July 2020
Published date: 1 November 2020
Keywords: CO2 biomethanisation, pH rise, Anaerobic digestion, Food waste, Renewable energy, Hydrogenotrophic methanogens

Identifiers

Local EPrints ID: 443178
URI: http://eprints.soton.ac.uk/id/eprint/443178
ISSN: 0306-2619
PURE UUID: ce6a3f10-cce2-4f25-8319-d08b34d0520f
ORCID for Yue Zhang: ORCID iD orcid.org/0000-0002-5068-2260
ORCID for Sonia Heaven: ORCID iD orcid.org/0000-0001-7798-4683

Catalogue record

Date deposited: 13 Aug 2020 16:38
Last modified: 07 Oct 2020 01:48

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×