Effect of pH on the Production of Volatile Fatty Acids in Dark Fermentation Process of Organic Waste

Grzelak, Justyna; Ślężak, Radosław; Krzystek, L.; Ledakowicz, S.

doi:10.1515/eces-2018-0020

Cited by 6 publications

(8 citation statements)

References 31 publications

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“…The lowest valeric content was observed at pH 12. This is opposite to the findings of Grzelak et al 23 . who reported maximum VFA content under alkaline conditions of pH 10–12.…”

Section: Resultscontrasting

confidence: 99%

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A parametric experimental validation of a biorefinery concept based on anaerobic digestion of fruit and vegetable waste

Magama

Chiyanzu

Mulopo

2022

Biofuels Bioprod Bioref

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The goal of this paper was to assess the possibilities for one-stage reactor anaerobic digestion processing of fruit and vegetable biomass within a biorefinery concept for optimum products. Co-digestion was the simplest strategy to implement to increase product yield among the variables tested (pH, ultrasonification, and co-digestion). Methane yields from co-digestion of fruit and vegetable waste (FVW) and pig manure (PM) ranged from 318 to 434 NmL /g VS, with the highest yield (434 NmL /g VS) achieved at a co-digestion ratio of FVW75:PM25, representing a 20% increase over the methane production from FVW alone. The pH value was determined to be the most effective variable for enhancing methane production, with pH = 8 producing the maximum cumulative methane yield of 497 NmL/g VS. There was no significant change in the composition of volatile fatty acids (VFA) with pH in terms of dominant product type; valeric acid was the predominant VFA synthesized at all starting pH values except pH = 12, where formic acid was the predominant acid formed. As a digestate posttreatment procedure, hydrothermal carbonization was combined with anaerobic digestion. At 200 °C, the maximum hydrochar yield production was 58.2%, with a higher heating value of 10.75 MJ/kg.

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“…The lowest valeric content was observed at pH 12. This is opposite to the findings of Grzelak et al 23 . who reported maximum VFA content under alkaline conditions of pH 10–12.…”

Section: Resultscontrasting

confidence: 99%

“…The lowest valeric content was observed at pH 12. This is opposite to the findings of Grzelak et al 23 who reported maximum VFA content under alkaline conditions of pH 10-12. No butyric or propionic acid was detected in any of the pH treatments, except at pH 4.…”

Section: Effect Of Ph On Vfa Production and Compositioncontrasting

confidence: 99%

A parametric experimental validation of a biorefinery concept based on anaerobic digestion of fruit and vegetable waste

Magama

Chiyanzu

Mulopo

2022

Biofuels Bioprod Bioref

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“…The bioreactor pH was maintained at 7.0 ± 0.1 in all experimental runs. This pH value has been selected based on our own research [33] and available topical literature [27,34] confirming the highest VFAs yields in neutral pH. An increased production of VFAs in each of the processes was observed at the initial days of transient state.…”

Section: An Impact Of Olr and Hrt On Vfas Synthesismentioning

confidence: 99%

Production of Volatile Fatty Acids in a Semi-Continuous Dark Fermentation of Kitchen Waste: Impact of Organic Loading Rate and Hydraulic Retention Time

et al. 2021

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The aim of the study was to evaluate the possibility of using the process of dark fermentation to convert kitchen waste into valuable volatile fatty acids in a semi-continuous process at different values of the organic loading rate (2.5 and 5.0 gVS/(L × d)) and hydraulic retention time (5 and 10 d) using anaerobic mixed microbial consortia. The experiments were performed in a bioreactor of working volume 8L with pH control. The maximum volatile fatty acids yield in a steady state (22.3 g/L) was achieved at the organic loading rate of 5.0 gVS/(L × d) and HRT of 10 days. The main products of dark fermentation were acetic and butyric acids, constituting, respectively, 35.2–47.7% and 24.1–30.0% of all identified volatile fatty acids. Additionally, at the beginning of the fermentation and in a steady-state condition, the microbial population analysis (16S rDNA) of the fermentation mixture with the most effective volatile fatty acids generation has been performed to monitor the DF microflora development. The dominant microorganisms at a phylum level in a steady state were Firmicutes (44.9%) and Bacteroidetes (30.1%), which indicate the main role of those phyla in the volatile fatty acids synthesis.

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“…The butyric acid metabolic pathway is activated to counteract pH drop and, therefore, it is favoured at pH below 6 [68]; whereas the metabolic pathway of Equation ( 1) allows for biogas richer in H 2 . If the metabolic shift is delayed or avoided, it is obvious that the % H 2 in the biogas remains high.…”

Section: Dark Fermentation Kinetics and Parametersmentioning

confidence: 99%

Hydrogen Production from Enzymatic Hydrolysates of Alkali Pre-Treated Giant Reed (Arundo donax L.)

Vasmara¹,

Cianchetta

Marchetti³

et al. 2022

Energies

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The perennial rhizomatous grass giant reed (Arundo donax L.) can be exploited to produce hydrogen by dark fermentation. This implies a high availability of simple sugars, like glucose and xylose, and, thus, a pre-treatment is necessary to remove lignin and expose the holocellulose to enzymatic attack. This study aimed at evaluating the hydrogen production from giant reed hydrolysates. Giant reed dry meal was pre-treated with diluted NaOH (1.2% weight/weight), then the solid fraction was separated from the alkaline black liquor by filtration, enzymatically hydrolyzed with a cellulase blend (Cellic CTec2), and fermented in mesophilic batch conditions with a microbial consortium derived from pig slurry. The impact on hydrogen yield of initial pH was evaluated by comparing the hydrogen production from hydrolysates with not adjusted (5.3) or adjusted initial pH (8.7) using NaOH or alkaline black liquor. The highest hydrogen yield, 2.0 mol/mol of hexoses, was obtained with alkaline initial pH 8.7, regardless of how the pH adjustment was managed. The yield was 39% higher than that obtained in reactors with initial pH 5.3. In conclusion, thermo-alkaline pre-treatment followed by enzymatic saccharification and initial pH adjustment at 8.7 with the black liquor remaining after pre-treatment is a promising strategy to produce hydrogen from giant reeds in dark fermentation.

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Effect of pH on the Production of Volatile Fatty Acids in Dark Fermentation Process of Organic Waste

Cited by 6 publications

References 31 publications

A parametric experimental validation of a biorefinery concept based on anaerobic digestion of fruit and vegetable waste

A parametric experimental validation of a biorefinery concept based on anaerobic digestion of fruit and vegetable waste

Production of Volatile Fatty Acids in a Semi-Continuous Dark Fermentation of Kitchen Waste: Impact of Organic Loading Rate and Hydraulic Retention Time

Hydrogen Production from Enzymatic Hydrolysates of Alkali Pre-Treated Giant Reed (Arundo donax L.)

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