# Editorial: Proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022)

Ao Xia, Christiane Herrmann, Alissara Reungsang, Pau-Loke Show, Eric

Trably, Junjun Wu

► To cite this version:

Ao Xia, Christiane Herrmann, Alissara Reungsang, Pau-Loke Show, Eric Trably, et al.. Editorial: Proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022). Frontiers in Bioengineering and Biotechnology, 2024, 12, pp.1390377. 10.3389/fbioe.2024.1390377. hal-04569659

HAL Id: hal-04569659

https://hal.inrae.fr/hal-04569659

Submitted on 6 May 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_1.png" /></figure>

Check for updates

OPEN ACCESS

EDITED AND REVIEWED BY
Manfred Zinn,
HES-SO Valais-Wallis, Switzerland

*CORRESPONDENCE

Ao Xia,
aoxia@cqu.edu.cn

RECEIVED 23 February 2024

ACCEPTED 25 March 2024

PUBLISHED 09 April 2024

CITATION

Xia A, Herrmann C, Reungsang A, Show P-L, Trably E and Wu J (2024), Editorial: Proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022).

Front. Bioeng. Biotechnol. 12:1390377.
doi: 10.3389/fbioe.2024.1390377

COPYRIGHT

© 2024 Xia, Herrmann, Reungsang, Show, Trably and Wu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

# Editorial: Proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022)

Ao Xia¹,²*, Christiane Herrmann³, Alissara Reungsang⁴, Pau-Loke Show⁵,⁶, Eric Trably⁷ and Junjun Wu¹,²

¹Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing, China, ²Institute of Engineering Thermophysics, School of Energy and Power Engineering, Chongqing University, Chongqing, China, ³Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB), Potsdam, Germany, ⁴Research Group for Development of Microbial Hydrogen Production Process from Biomass, Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen, Thailand, ⁵Department of Chemical Engineering, Khalifa University, Abu Dhabi, United Arab Emirates, ⁶Department of Chemical and Environment Engineering, Faculty of Science and Engineering, University of Nottingham Malaysia, Semenyih, Malaysia, ⁷INRAE, Université de Montpellier, LBE, Narbonne, France

KEYWORDS

biofuels, waste treatment, fermentation, mass transfer, circular economy

## Editorial on the Research Topic

proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022)

A massive amount of solid wastes (such as straws, manures, plastic and food wastes), liquid wastes (such as municipal and agricultural wastewaters), and gaseous wastes (such as flue gases rich in carbon dioxide) are generated from industrial, residential, transportation and agricultural sectors (Siegelman et al., 2021; Vyas et al., 2022; You et al., 2022). These wastes would cause significant adverse environmental impacts if they are not properly treated. Turning wastes into biofuels and bioproducts can make a substantial contribution to the clean energy supply and environmental protection (Bhatia et al., 2018; Peng et al., 2023; Wang et al., 2023). However, competitive and sustainable circular economy solutions via scientific and technological innovation are urgently needed to improve the conversion rates and efficiencies of such processes. The Research Topic includes four original research papers, which could provide various solutions to upgrade the solid, liquid, and gaseous wastes to value-added products.

Anaerobic digestion is a mature technology and has been developed for over a hundred years. However, anaerobic mono-digestion suffers from drawbacks such as low biogas/biomethane yield, digester instability and limited year-round availability of specific feedstocks (Karki et al., 2021). A study by Kriswantoro et al. investigated the performance of anaerobic co-digestion of untreated Napier grass and food waste hydrolyzed with subcritical water. An optimal biomethane yield of 614.37 mL/g VS was obtained at a 1:1 ratio (VS basis) of Napier grass and food waste during two-stage anaerobic digestion that sequentially produced biohydrogen and biomethane. The methane concentration in the biogas was higher than 65% on day 20 and maintained in the range of 65%–80% until the end of anaerobic digestion. Liquid digestate derived from anaerobic digestion contains high levels of nitrogen and
<figure><img src="image_2.png" /></figure>

Check for updates

OPEN ACCESS

EDITED AND REVIEWED BY
Manfred Zinn,
HES-SO Valais-Wallis, Switzerland

*CORRESPONDENCE
Ao Xia,
aoxia@cqu.edu.cn

RECEIVED 23 February 2024

ACCEPTED 25 March 2024

PUBLISHED 09 April 2024

CITATION

Xia A, Herrmann C, Reungsang A, Show P-L, Trably E and Wu J (2024), Editorial: Proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022).

Front. Bioeng. Biotechnol. 12:1390377.
doi: 10.3389/fbioe.2024.1390377

COPYRIGHT

© 2024 Xia, Herrmann, Reungsang, Show, Trably and Wu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

# Editorial: Proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022)

Ao Xia¹,²*, Christiane Herrmann³, Alissara Reungsang⁴, Pau-Loke Show⁵,⁶, Eric Trably⁷ and Junjun Wu¹,²

¹Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Chongqing University, Ministry of Education, Chongqing, China, ²Institute of Engineering Thermophysics, School of Energy and Power Engineering, Chongqing University, Chongqing, China, ³Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB), Potsdam, Germany, ⁴Research Group for Development of Microbial Hydrogen Production Process from Biomass, Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen, Thailand, ⁵Department of Chemical Engineering, Khalifa University, Abu Dhabi, United Arab Emirates, ⁶Department of Chemical and Environment Engineering, Faculty of Science and Engineering, University of Nottingham Malaysia, Semenyih, Malaysia, ⁷INRAE, Université de Montpellier, LBE, Narbonne, France

KEYWORDS

biofuels, waste treatment, fermentation, mass transfer, circular economy

## Editorial on the Research Topic

proceedings of ABBS-international conference on biohydrogen and bioprocesses 2022 (ABBS 2022)

A massive amount of solid wastes (such as straws, manures, plastic and food wastes), liquid wastes (such as municipal and agricultural wastewaters), and gaseous wastes (such as flue gases rich in carbon dioxide) are generated from industrial, residential, transportation and agricultural sectors (Siegelman et al., 2021; Vyas et al., 2022; You et al., 2022). These wastes would cause significant adverse environmental impacts if they are not properly treated. Turning wastes into biofuels and bioproducts can make a substantial contribution to the clean energy supply and environmental protection (Bhatia et al., 2018; Peng et al., 2023; Wang et al., 2023). However, competitive and sustainable circular economy solutions via scientific and technological innovation are urgently needed to improve the conversion rates and efficiencies of such processes. The Research Topic includes four original research papers, which could provide various solutions to upgrade the solid, liquid, and gaseous wastes to value-added products.

Anaerobic digestion is a mature technology and has been developed for over a hundred years. However, anaerobic mono-digestion suffers from drawbacks such as low biogas/biomethane yield, digester instability and limited year-round availability of specific feedstocks (Karki et al., 2021). A study by Kriswantoro et al. investigated the performance of anaerobic co-digestion of untreated Napier grass and food waste hydrolyzed with subcritical water. An optimal biomethane yield of 614.37 mL/g VS was obtained at a 1:1 ratio (VS basis) of Napier grass and food waste during two-stage anaerobic digestion that sequentially produced biohydrogen and biomethane. The methane concentration in the biogas was higher than 65% on day 20 and maintained in the range of 65%–80% until the end of anaerobic digestion. Liquid digestate derived from anaerobic digestion contains high levels of nitrogen and
phosphorus pollutants, which may require an energy-intensive and
high-cost post-treatment process. The cultivation of microalgae may
provide an alternative solution to treat liquid digestate while
producing high-value biomass (Xia and Murphy, 2016). The work
of Wang et al. assessed the potential of cultivation of microalgae
Chlorella sp. in the liquid digestate from anaerobic digestion of
brewer's grains and brewery wastewater. A maximum biomass
concentration of 1.36 g/L was obtained at 10% of digestate and
20% of brewery wastewater, which was 24.77% higher than the
control cultivated in the BG11 medium. The maximum removal of
ammonia nitrogen, chemical oxygen demand, total nitrogen, and total
phosphorus achieved 98.20%, 89.98%, 86.98%, and 71.86%,
respectively, suggesting a potential approach for liquid digestate
treatment and microalgae biomass production.

Plastic waste has become a serious environmental issue in recent
years; it is forecasted that plastic waste will rapidly accumulate to
approximately 12 billion metric tons by 2050 (Geyer et al., 2017). The
most promising route to tackle such a global issue is to turn plastic waste
into small-molecule chemicals, which is considered as chemical
upcycling. Lin et al. explored the feasibility of the synthesis of
vitrimers (a class of covalent adaptable network plastic materials)
with self-repairing properties by using plastic wastes as feedstocks.
The raw materials were subjected to glycolysis to obtain the glycolysis
products that were subsequently used as a reagent for the vitrimer
synthesis process. The glycolysis of raw material and vitrimer synthesis
processes were optimized.

Microalgae photosynthesis may offer an alternative solution to
capture CO2 in ambient (420 ppm) or flue gas levels (10%-25%)
(Chen and Xu, 2021), while it is important to improve the CO2 mass
transfer at the gas-liquid interface. Zhao et al. proposed a new aeration
device with bubble-cutting slices, which can separate bubbles into
smaller sizes after their departure and improve the CO2 mass
transfer. When the photobioreactor was equipped with the bubble-
cutting slices, the bubble size and rising velocity decreased by 27.97% and
46.88%, respectively, while the prolongation of bubble residence time
increased by 84.55%. Consequently, the dry weight and biomass
productivity of microalgae *Chlorella pyrenoidosa* were improved by 6.
99% and 33.33%, respectively. The authors demonstrated an interesting
way to improve the CO2 mass transfer and enhance microalgae
cultivation.

References

Bhatia, S. K., Joo, H. S., and Yang, Y. H. (2018). Biowaste-to-bioenergy using biological methods - a mini-review. *Energy Conv. Manag.* 177, 640–660. doi:10.1016/j.enconman.2018.09.090

Chen, Y., and Xu, C. (2021). How to narrow the CO₂ gap from growth-optimal to flue gas levels by using microalgae for carbon capture and sustainable biomass production. *J. Clean Prod.* 280, 124448. doi:10.1016/j.jclepro.2020.124448

Geyer, R., Jambeck, J. R., and Law, K. L. (2017). Production, use, and fate of all plastics ever made. *Sci. Adv.* 3 (7), e1700782. doi:10.1126/sciadv.1700782

Karki, R., Chuenchart, W., Surendra, K. C., Shrestha, S., Raskin, L., Sung, S. W., et al. (2021). Anaerobic co-digestion: current status and perspectives. *Bioresour. Technol.* 330, 125001. doi:10.1016/j.biortech.2021.125001

Peng, X., Jiang, Y., Chen, Z., Osman, A. I. I., Farghali, M., Rooney, D. W. W., et al. (2023). Recycling municipal, agricultural and industrial waste into energy, fertilizers, food and construction materials, and economic feasibility: a review. *Environ. Chem. Lett.* 21 (2), 765–801. doi:10.1007/s10311-022-01551-5

In conclusion, these works show various potential approaches to
efficiently convert solid, liquid, and gaseous wastes to biofuels and
bioproducts to achieve a circular economy. We would like to
sincerely acknowledge all authors and reviewers for their
important contributions to this Research Topic. We also would
like to thank the Frontiers in Bioengineering and Biotechnology
editorial team for their continued support and assistance.

Author contributions

AX: Writing—original draft. CH: Writing—review and editing.

AR: Writing—review and editing. PS: Writing—review and editing.

ET: Writing—review and editing. JW: Writing—review and editing.

Funding

The author(s) declare that no financial support was received for
the research, authorship, and/or publication of this article.

Conflict of interest

The authors declare that the research was conducted in the
absence of any commercial or financial relationships that could be
construed as a potential conflict of interest.

The author(s) declared that they were an editorial board
member of Frontiers, at the time of submission. This had no
impact on the peer review process and the final decision.

Publisher's note

All claims expressed in this article are solely those of the authors
and do not necessarily represent those of their affiliated
organizations, or those of the publisher, the editors and the
reviewers. Any product that may be evaluated in this article, or
claim that may be made by its manufacturer, is not guaranteed or
endorsed by the publisher.

Siegelman, R. L., Kim, E. J., and Long, J. R. (2021). Porous materials for carbon dioxide separations. *Nat. Mater.* 20 (8), 1060–1072. doi:10.1038/s41563-021-01054-8

Vyas, S., Prajapati, P., Shah, A. V., Srivastava, V. K., and Varjani, S. (2022). Opportunities and knowledge gaps in biochemical interventions for mining of resources from solid waste: a special focus on anaerobic digestion. *Fuel* 311, 122625. doi:10.1016/j.fuel.2021.122625

Wang, Z. X., Peng, X. G., Xia, A., Shah, A. A., Yan, H. C., Huang, Y., et al. (2023). Comparison of machine learning methods for predicting the methane production from anaerobic digestion of lignocellulosic biomass. *Energy* 263, 125883. doi:10.1016/j. energy.2022.125883

Xia, A., and Murphy, J. D. (2016). Microalgal cultivation in treating liquid digestate from biogas systems. *Trends Biotechnol.* 34 (4), 264–275. doi:10.1016/j.tibtech.2015.12.010

You, X., Yang, L., Zhou, X., and Zhang, Y. (2022). Sustainability and carbon neutrality trends for microalgae-based wastewater treatment: a review. *Environ. Res.* 209, 112860. doi:10.1016/j.envres.2022.112860
phosphorus pollutants, which may require an energy-intensive and high-cost post-treatment process. The cultivation of microalgae may provide an alternative solution to treat liquid digestate while producing high-value biomass (Xia and Murphy, 2016). The work of Wang et al. assessed the potential of cultivation of microalgae *Chlorella* sp. in the liquid digestate from anaerobic digestion of brewer's grains and brewery wastewater. A maximum biomass concentration of 1.36 g/L was obtained at 10% of digestate and 20% of brewery wastewater, which was 24.77% higher than the control cultivated in the BG11 medium. The maximum removal of ammonia nitrogen, chemical oxygen demand, total nitrogen, and total phosphorus achieved 98.20%, 89.98%, 86.98%, and 71.86%, respectively, suggesting a potential approach for liquid digestate treatment and microalgae biomass production.

Plastic waste has become a serious environmental issue in recent years; it is forecasted that plastic waste will rapidly accumulate to approximately 12 billion metric tons by 2050 (Geyer et al., 2017). The most promising route to tackle such a global issue is to turn plastic waste into small-molecule chemicals, which is considered as chemical upcycling. Lin et al. explored the feasibility of the synthesis of vitrimers (a class of covalent adaptable network plastic materials) with self-repairing properties by using plastic wastes as feedstocks. The raw materials were subjected to glycolysis to obtain the glycolysis products that were subsequently used as a reagent for the vitrimer synthesis process. The glycolysis of raw material and vitrimer synthesis processes were optimized.

Microalgae photosynthesis may offer an alternative solution to capture CO₂ in ambient (420 ppm) or flue gas levels (10%-25%) (Chen and Xu, 2021), while it is important to improve the CO₂ mass transfer at the gas-liquid interface. Zhao et al. proposed a new aeration device with bubble-cutting slices, which can separate bubbles into smaller sizes after their departure and improve the CO₂ mass transfer. When the photobioreactor was equipped with the bubble-cutting slices, the bubble size and rising velocity decreased by 27.97% and 46.88%, respectively, while the prolongation of bubble residence time increased by 84.55%. Consequently, the dry weight and biomass productivity of microalgae *Chlorella pyrenoidosa* were improved by 6. 99% and 33.33%, respectively. The authors demonstrated an interesting way to improve the CO₂ mass transfer and enhance microalgae cultivation.

## References

Bhatia, S. K., Joo, H. S., and Yang, Y. H. (2018). Biowaste-to-bioenergy using biological methods - a mini-review. *Energy Conv. Manag.* 177, 640–660. doi:10.1016/j.enconman.2018.09.090

Chen, Y., and Xu, C. (2021). How to narrow the CO₂ gap from growth-optimal to flue gas levels by using microalgae for carbon capture and sustainable biomass production. *J. Clean Prod.* 280, 124448. doi:10.1016/j.jclepro.2020.124448

Geyer, R., Jambeck, J. R., and Law, K. L. (2017). Production, use, and fate of all plastics ever made. *Sci. Adv.* 3 (7), e1700782. doi:10.1126/sciadv.1700782

Karki, R., Chuenchart, W., Surendra, K. C., Shrestha, S., Raskin, L., Sung, S. W., et al. (2021). Anaerobic co-digestion: current status and perspectives. *Bioresour. Technol.* 330, 125001. doi:10.1016/j.biortech.2021.125001

Peng, X., Jiang, Y., Chen, Z., Osman, A. I. I., Farghali, M., Rooney, D. W. W., et al. (2023). Recycling municipal, agricultural and industrial waste into energy, fertilizers, food and construction materials, and economic feasibility: a review. *Environ. Chem. Lett.* 21 (2), 765–801. doi:10.1007/s10311-022-01551-5

In conclusion, these works show various potential approaches to efficiently convert solid, liquid, and gaseous wastes to biofuels and bioproducts to achieve a circular economy. We would like to sincerely acknowledge all authors and reviewers for their important contributions to this Research Topic. We also would like to thank the Frontiers in Bioengineering and Biotechnology editorial team for their continued support and assistance.

## Author contributions

AX: Writing–original draft. CH: Writing–review and editing.

AR: Writing–review and editing. PS: Writing–review and editing.

ET: Writing–review and editing. JW: Writing–review and editing.

## Funding

The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.

## Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

## Publisher's note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Siegelman, R. L., Kim, E. J., and Long, J. R. (2021). Porous materials for carbon dioxide separations. *Nat. Mater.* 20 (8), 1060–1072. doi:10.1038/s41563-021-01054-8

Vyas, S., Prajapati, P., Shah, A. V., Srivastava, V. K., and Varjani, S. (2022). Opportunities and knowledge gaps in biochemical interventions for mining of resources from solid waste: a special focus on anaerobic digestion. *Fuel* 311, 122625. doi:10.1016/j.fuel.2021.122625

Wang, Z. X., Peng, X. G., Xia, A., Shah, A. A., Yan, H. C., Huang, Y., et al. (2023). Comparison of machine learning methods for predicting the methane production from anaerobic digestion of lignocellulosic biomass. *Energy* 263, 125883. doi:10.1016/j.energy.2022.125883

Xia, A., and Murphy, J. D. (2016). Microalgal cultivation in treating liquid digestate from biogas systems. *Trends Biotechnol.* 34 (4), 264–275. doi:10.1016/j.tibtech.2015.12.010

You, X., Yang, L., Zhou, X., and Zhang, Y. (2022). Sustainability and carbon neutrality trends for microalgae-based wastewater treatment: a review. *Environ. Res.* 209, 112860. doi:10.1016/j.envres.2022.112860