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 (; ; ). 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 (; ; ). 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 (). 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 (). 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 (). 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%) (), 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.
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.
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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.
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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.
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Summary
Keywords
biofuels, waste treatment, fermentation, mass transfer, circular economy
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
Received
23 February 2024
Accepted
25 March 2024
Published
09 April 2024
Volume
12 - 2024
Edited and reviewed by
Manfred Zinn, HES-SO Valais-Wallis, Switzerland
Updates
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.
*Correspondence: Ao Xia, aoxia@cqu.edu.cn
Disclaimer
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.