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Antifoam, dilution and trace element addition as foaming control strategies in mesophilic anaerobic digestion of sugar beet pulp

Antifoam, dilution and trace element addition as foaming control strategies in mesophilic anaerobic digestion of sugar beet pulp
Antifoam, dilution and trace element addition as foaming control strategies in mesophilic anaerobic digestion of sugar beet pulp
The effectiveness of foaming control strategies, including trace element addition, feedstock dilution and use of antifoams, was assessed for the anaerobic digestion of sugar beet pulp (SBP) at laboratory scale under mesophilic conditions. Semi-continuous digestion at an organic loading rate (OLR) of 2 g VS L-1 day-1 resulted in methane yields of 0.316 L CH4 g-1 of volatile solids (VS), with a VS destruction rate of ~91%. At OLR of 3 g VS L-1 day-1 or above, foaming occurred, accompanied by small increases in alkalinity ratio and volatile fatty acid (VFA) concentrations and a slight fall in specific biogas and methane production, indicating a minor reduction in process stability and performance. At OLR 5 g VS L-1 day-1 foaming was persistent and severe. In contrast, digesters fed at OLR 5 g VS L-1 day-1 and supplemented with selected trace elements showed stable performance with no foaming. Dilution has proved an effective control strategy for other feedstocks, but feeding with diluted SBP (1:1 w/w) led to a decline in gas production and operational stability, with no significant benefits in eliminating foaming. Seven antifoams were tested for foam reduction and effects on batch digestion at a range of concentrations. Addition of certain antifoams at dosages of 0.5 mL L-1 or more could inhibit gas production. A selected antifoam agent was then trialled in semi-continuous digestion at OLR 5 g VS L-1 day-1. Repeated high antifoam dosing of 1 mL L-1 digestate was required to reduce foaming, and eventually proved inhibitory. More reliable screening tests are needed for antifoam selection, as batch toxicity testing may not provide a satisfactory guide to performance in continuous operation.
Sugar beet pulp, foaming, organic loading rate, Trace elements, antifoam, anaerobic digestion
0964-8305
1-13
Suhartini, Sri
6b1f437a-a266-48eb-a7ec-9bbc1db0f817
Heaven, Sonia
f25f74b6-97bd-4a18-b33b-a63084718571
Zhang, Yue
69b11d32-d555-46e4-a333-88eee4628ae7
Banks, Charles
5c6c8c4b-5b25-4e37-9058-50fa8d2e926f
Suhartini, Sri
6b1f437a-a266-48eb-a7ec-9bbc1db0f817
Heaven, Sonia
f25f74b6-97bd-4a18-b33b-a63084718571
Zhang, Yue
69b11d32-d555-46e4-a333-88eee4628ae7
Banks, Charles
5c6c8c4b-5b25-4e37-9058-50fa8d2e926f

Suhartini, Sri, Heaven, Sonia, Zhang, Yue and Banks, Charles (2019) Antifoam, dilution and trace element addition as foaming control strategies in mesophilic anaerobic digestion of sugar beet pulp. International Biodeterioration & Biodegradation, 145, 1-13, [104812]. (doi:10.1016/j.ibiod.2019.104812).

Record type: Article

Abstract

The effectiveness of foaming control strategies, including trace element addition, feedstock dilution and use of antifoams, was assessed for the anaerobic digestion of sugar beet pulp (SBP) at laboratory scale under mesophilic conditions. Semi-continuous digestion at an organic loading rate (OLR) of 2 g VS L-1 day-1 resulted in methane yields of 0.316 L CH4 g-1 of volatile solids (VS), with a VS destruction rate of ~91%. At OLR of 3 g VS L-1 day-1 or above, foaming occurred, accompanied by small increases in alkalinity ratio and volatile fatty acid (VFA) concentrations and a slight fall in specific biogas and methane production, indicating a minor reduction in process stability and performance. At OLR 5 g VS L-1 day-1 foaming was persistent and severe. In contrast, digesters fed at OLR 5 g VS L-1 day-1 and supplemented with selected trace elements showed stable performance with no foaming. Dilution has proved an effective control strategy for other feedstocks, but feeding with diluted SBP (1:1 w/w) led to a decline in gas production and operational stability, with no significant benefits in eliminating foaming. Seven antifoams were tested for foam reduction and effects on batch digestion at a range of concentrations. Addition of certain antifoams at dosages of 0.5 mL L-1 or more could inhibit gas production. A selected antifoam agent was then trialled in semi-continuous digestion at OLR 5 g VS L-1 day-1. Repeated high antifoam dosing of 1 mL L-1 digestate was required to reduce foaming, and eventually proved inhibitory. More reliable screening tests are needed for antifoam selection, as batch toxicity testing may not provide a satisfactory guide to performance in continuous operation.

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Suhartini et al antifoam 2019 - scholar text - Accepted Manuscript
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More information

Accepted/In Press date: 30 September 2019
e-pub ahead of print date: 5 October 2019
Published date: November 2019
Keywords: Sugar beet pulp, foaming, organic loading rate, Trace elements, antifoam, anaerobic digestion

Identifiers

Local EPrints ID: 434961
URI: http://eprints.soton.ac.uk/id/eprint/434961
ISSN: 0964-8305
PURE UUID: 09130322-d05c-44dc-b796-202dc62a2fbd
ORCID for Sonia Heaven: ORCID iD orcid.org/0000-0001-7798-4683
ORCID for Yue Zhang: ORCID iD orcid.org/0000-0002-5068-2260

Catalogue record

Date deposited: 17 Oct 2019 16:30
Last modified: 07 Oct 2020 06:15

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