Co-production of hydrogen and caproate for an effective bioprocessing of waste

Oct 16, 2026

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The objective of the study was to valorize waste stream for the co-production of hydrogen and caproate via open culture fermentation (OCF). Batch studies confirmed that using lactose together with lactate and acetate supports mutual coexistence of chain elongation and dark fermentation. In continuous operation using an upflow anaerobic sludge blanket reactor (UASB), acid whey served as a model feedstock. Shortening HRT to 2.5 days enabled co-production with almost complete methanogenesis inhibition. Over 50 days, average hydrogen and caproate production reached 1.78 ± 0.75 L H2/L/d and 133.4 ± 17.9 mmol C/L/d.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages5

Reading Time13 min

AccessFree to download

Introduction

Bioeconomy, carboxylate platform, and OCF

Chain elongation and methanogenesis competition

Caproate production challenges

Rationale for co-production with biohydrogen

Bioresource Technology xxx (xxxx) xxxx Contents lists available at ScienceDirect Bioresource Technology journal [homepage:](homepage: www.elsevier. com/locate/biortech)[ www.elsevier. com/locate/biortech](homepage: www.elsevier. com/locate/biortech) | Co-production of hydrogen and caproate for an eﬀective bioprocessing of waste
Filip Brodowskia, Anna Dubera, Roman Zagrodnikb, Piotr Oleskowicz-Popiela,⁎
a Water Supply and Bioeconomy Division, Faculty of Environmental Engineering and Energy, Poznan University of Technology, Berdychowo 4, 60-965, Poznan, Poland b Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznanskiego 8, 61-614 Poznan, Poland | | --- | | G R A P H I C A L A B S T R A C T | | A R T I C L E I N F O | | A B S T R A C T | | --- | --- | --- | | Keywords:
Medium chain carboxylic acids
Caproate
Hydrogen
Whey
Co-production | | The objective of the study was to valorize waste stream for the co-production of hydrogen and caproate via open culture fermentation (OCF). Batch studies conﬁrmed that the use of sugar (lactose) together with carboxylates (lactate and acetate) may allow mutual coexistence of chain elongation and dark fermentation processes. During the continuous test in an upﬂow anaerobic sludge blanket reactor (UASB), acid whey was used as a model feedstock due to a high concentration of lactose and lactate. Shortening hydraulic retention time (HRT) to 2.5 days allowed the co-production of hydrogen and caproate with almost complete methanogenesis inhibition. During the 50 days period, the average hydrogen and caproate production were 1.78 ± 0.75 LH2/L/d and 133.4 ± 17.9 mmol C/L/d, respectively. | 1. Introduction The constantly growing demand for primary energy and depleting fossil fuel resources are conducive to the search for new energy solutions based on the renewable resources. Bioreﬁneries producing energy and marketable bioproducts from biomass and organic waste are becoming increasingly popular (Dragone et al., 2020). The production of bulk chemicals from organic waste, however, faces the problem of economic viability, which is why a new spectrum of products is being sought. Therefore, more and more attention is paid to new solutions such carboxylate platform, i.e. open culture fermentation (OCF) leading to the formation of medium chain carboxylic acids (MCCAs) containing from 6 to 12 carbon atoms in the molecule in the process of carboxylic chain elongation (CE). The CE process is based on the oxidation of the electron donor to acetyl-CoA and then combining it with another CoA derivative, e.g. acetyl-CoA in combination with acetyl-CoA leads to the formation of butyrate, and the combination of acetyl-CoA with butyrylCoA leads to caproate (Spirito et al., 2014). Large species diversity in OCF systems enables fermentation in non-sterile conditions, which translates into a reduction in the capital and operating costs compared to the axenic systems. Conducting the CE via OCF competes with themethanogenesis, to overcome this issue, speciﬁc methanogenic inhibitors can be added to promote the CE. However, the high cost of chemicals makes it unproﬁtable. Another strategy is to run the OCF at a controlled mildly acidic pH of 5.5, which leads to the inhibition ofacetoclastic methanogens (Angenent et al., 2016). The production of methane is still possible by hydrogenotrophic methanogens; however, theoretically it does not cause competition for the substrate with the ⁎ Corresponding author. E-mail address: [piotr.oleskowicz-popiel@put.poznan.pl](piotr.oleskowicz-popiel@put.poznan.pl) (P. Oleskowicz-Popiel). [https://doi.org/10.1016/j.biortech.2020.123895](https://doi.org/10.1016/j.biortech.2020.123895) Received 12 June 2020; Received in revised form 17 July 2020; Accepted 18 July 2020 0960-8524/ © 2020 Elsevier Ltd. All rights reserved. Please cite this article as: Filip Brodowski, et al., Bioresource Technology, [https://doi.org/10.1016/j.biortech.2020.1

FAQs

What was the main objective of the study?

The study aimed to valorize a waste stream for the co-production of hydrogen and caproate using open culture fermentation (OCF).

How did the researchers address competition with methanogenesis during chain elongation?

They reduced hydraulic retention time (HRT) to 2.5 days in a UASB system, which resulted in almost complete methanogenesis inhibition and supported chain elongation.

What feedstock and reactor configuration were used in continuous testing?

Acid whey was used as a model feedstock due to high concentrations of lactose and lactate, and the continuous process used an upflow anaerobic sludge blanket reactor (UASB).

Oct 16, 2026

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