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Polyhydroxybutyrate-Natural Fiber Reinforcement Biocomposite Production and Their Biological Recyclability through Anaerobic Digestion
University of Borås, Faculty of Textiles, Engineering and Business. (Swedish Centre for Resource Recovery)
University of Borås, Faculty of Textiles, Engineering and Business. (Swedish Centre for Resource Recovery)ORCID iD: 0000-0001-6280-4483
University of Borås, Faculty of Textiles, Engineering and Business.ORCID iD: 0000-0002-4283-9715
University of Borås, Faculty of Textiles, Engineering and Business. (Swedish Centre for Resource Recovery)ORCID iD: 0000-0003-4887-2433
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2022 (English)In: Energies, E-ISSN 1996-1073, Vol. 15, no 23Article in journal (Refereed) Published
Sustainable development
According to the author(s), the content of this publication falls within the area of sustainable development.
Abstract [en]

The existing recycling methods of PHA-based material are ineffective in terms of increasing resource efficiency and the production of high value end-of-life products. Therefore, in this study, a novel approach of acidogenic fermentation was proposed to recycle PHB-based composites reinforced with natural fibers such as cellulose, chitin, chitosan, orange waste, sawdust, soy protein, and starch. The inclusion of cellulose, chitosan, and sawdust improved the impact properties of the composites while other fillers had various effects on the mechanical properties. These three composites and neat PHB were subsequently subjected to biological degradation via acidogenic digestion to determine the possibility of converting PHB-based composites into volatile fatty acids (VFAs). Two different pH levels of 6 and 10 were applied to assess the effect of pH on the bioconversion and inhibition of the methanogenesis. The results showed promising PHB degradation, contributing to considerable VFA production of 2.5 g/L at pH 6 after 47 days. At pH 6, the presence of the natural fibers in the biocomposites promoted the degradation rate. On the contrary, pH 10 proved to be more suitable for the degradation of the fibers. The VFA which is produced can be recirculated into PHB production, fitting with the concept of a circulating bioeconomy.

Place, publisher, year, edition, pages
2022. Vol. 15, no 23
Keywords [en]
acidogenic fermentation, biocomposites, biological recycling, natural fillers, polyhydroxybutyrate, volatile fatty acids
National Category
Other Industrial Biotechnology
Research subject
Resource Recovery; Resource Recovery
Identifiers
URN: urn:nbn:se:hb:diva-29180DOI: 10.3390/en15238934ISI: 000897348900001Scopus ID: 2-s2.0-85143809706OAI: oai:DiVA.org:hb-29180DiVA, id: diva2:1723539
Available from: 2023-01-03 Created: 2023-01-03 Last updated: 2023-08-28Bibliographically approved
In thesis
1. Volatile Fatty Acids as a Key to Sustainability and Circularity in Polyhydroxyalkanoates Production
Open this publication in new window or tab >>Volatile Fatty Acids as a Key to Sustainability and Circularity in Polyhydroxyalkanoates Production
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The negative consequences of plastic pollution on both environmental and socio-economic aspects have motivated the development of sustainable and renewable materials to replace the petroleum-based plastic. Polyhydroxyalkanoates (PHAs), which are bioplastics, having an outstanding biodegradability and rather comparable thermal and mechanical properties, are potential alternatives for the replacement of conventional plastics. However, one of the hurdles on the way to PHA commercial production is the cost of conventional feedstock, which can constitute up to 50% of the production cost. In this regard, volatile fatty acids (VFAs) derived from acidogenic fermentation of organic waste can be a promising substrate to increase the cost-competitiveness of PHA production. Therefore, in this thesis, VFAs were utilized and developed to be a key carbon feedstock for the sustainable and economically feasible production of PHAs. The applicability of individual and mixed VFAs as potential substrates was initially investigated through the cultivation of two different PHA-bearing bacteria of Bacillus megaterium and Cupriavidus necator, providing an average PHA yield on biomass of 10 and 55%, respectively. Further thorough studies, in terms of VFAs loading and inhibition thresholds and operating parameters, were conducted to improve the conversion efficiency of VFAs by C. necator. Consequently, a biomass yield on VFAs of up to 82% was obtained, rendering a PHA accumulation of 1 g/L using actual waste derived VFA effluent. In addition, in order to tackle the inherent issue of low productivity in batch and/or fed-batch cultivations under high VFA containing feed, a novel approach of immersed membrane reactor (iMBR) was introduced and applied in this thesis. With the assistance of membrane filtration, the PHA production was conducted in semi-continuous mode (up to 128 h), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. The outcomes achieved, furthermore, were 32.1 and 28.5%, respectively, higher than that from a continuous stirred tank (CSTR), in which the cultivation was affected by the washout effect. Moreover, considering the insufficiency of the current recycling methods of PHA-based products in terms of resource recovery, a novel attempt of acidogenic fermentation has been conducted to valorize the PHA-based composites through conversion into precursor VFAs. Afterwards, the recovered VFAs could be recirculated into PHA production, fulfilling the concept of a circular bioeconomy.

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2023
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 137
Keywords
bioplastics, food waste, polyhydroxyalkanoates, volatile fatty acids, immersed membrane bioreactor, acidogenic fermentation
National Category
Environmental Biotechnology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-29578 (URN)978-91-89271-92-0 (ISBN)978-91-89271-93-7 (ISBN)
Public defence
2023-05-26, C203, Allégatan 1, Borås, 10:00 (English)
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Supervisors
Available from: 2023-05-04 Created: 2023-03-28 Last updated: 2023-04-28Bibliographically approved

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Vu, Hoang DanhMahboubi, AmirFerreira, JorgeTaherzadeh, Mohammad JÅkesson, Dan

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