Selecting fermentation products for food waste valorisation with HRT and OLR as the key operational parameters

Vicky De Groof; Marta Coma; Tom Arnot; David J Leak; Ana B Lanham

doi:10.1016/j.wasman.2021.04.023

Selecting fermentation products for food waste valorisation with HRT and OLR as the key operational parameters

Waste Manag. 2021 May 15:127:80-89. doi: 10.1016/j.wasman.2021.04.023. Epub 2021 Apr 28.

Authors

Vicky De Groof¹, Marta Coma², Tom Arnot³, David J Leak⁴, Ana B Lanham⁵

Affiliations

¹ EPSRC Centre for Doctoral Training in Sustainable Chemical Technologies, University of Bath, Claverton Down, Bath BA2 7AY, UK; Department of Chemical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK.
² Centre for Sustainable and Circular Technologies (CSCT), University of Bath, Claverton Down, Bath BA2 7AY, UK.
³ Department of Chemical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK; Centre for Sustainable and Circular Technologies (CSCT), University of Bath, Claverton Down, Bath BA2 7AY, UK; Water Innovation & Research Centre (WIRC), University of Bath, Claverton Down, Bath BA2 7AY, UK.
⁴ Centre for Sustainable and Circular Technologies (CSCT), University of Bath, Claverton Down, Bath BA2 7AY, UK; Water Innovation & Research Centre (WIRC), University of Bath, Claverton Down, Bath BA2 7AY, UK; Department of Biology & Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK.
⁵ Department of Chemical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK; Water Innovation & Research Centre (WIRC), University of Bath, Claverton Down, Bath BA2 7AY, UK. Electronic address: A.Lanham@bath.ac.uk.

PMID: 33932853
DOI: 10.1016/j.wasman.2021.04.023

Abstract

Acidogenic fermentation is attractive for food waste valorisation. A better understanding is required on how operation affects product selectivity. This study demonstrated that the hydraulic retention time (HRT) and organic loading rate (OLR) selected fermentation pathways in a single-stage, semi-continuous stirred tank reactor. Three combinations of HRT and OLR were tested to distinguish the effect of each parameter. Three fermentation profiles with distinct microbial communities were obtained. Predominantly n-butyric acid (13 ± 2 gCOD L^-1, 55 ± 14% of carboxylates) was produced at an HRT of 8.5 days and OLR around 12 gCOD L^-1d^-1. Operating at an HRT two days longer, yet with similar OLR, stimulated chain elongation (up to 13.6 gCOD L^-1 of n-caproic acid). This was reflected by a microbial community twice as diverse at longer HRT as indicated by first and second order Hill number (¹D = 24 ± 4, ²D = 12 ± 3) and by a higher relative abundance of genera related to secondary fermentation, such as the VFA-elongating Caproiciproducens spp., and secondary lactic acid fermenter Secundilactobacillus spp.. Operating at a higher OLR (20 gCOD L^-1d^-1) but HRT of 8.5 days, resulted in typical lactic acid fermentation (34 ± 5 gCOD L^-1) harbouring a less diverse community (¹D = 8.0 ± 0.7, ²D = 5.7 ± 0.9) rich in acid-resistant homofermentative Lactobacillus spp. These findings demonstrate that a flexible product portfolio can be achieved by small adjustments in two key operating conditions. This improves the economic potential of acidogenic fermentation for food waste valorisation.

Keywords: Acidogenic fermentation; Butyric acid; Caproic acid; Food waste valorisation; Lactic acid; Resource recovery.

MeSH terms

Bioreactors
Fermentation
Food
Microbiota*
Refuse Disposal*