Fermentation of organic waste for bioplastic production. A potential sustainable alternative to fossil-fuel plastic

• Main Author: Lise Demeslay
• Other Authors: Landbúnaðarháskóli Íslands
• Format: Master Thesis
• Language: English
• Published: 2023
• Subjects: Náttúra og skógur; Umhverfisbreytingar á norðurslóðum; Environmental Changes at Higher Latitudes; Polyhydroxyalkanoates; Bioreactor; Fermentation; Bioplastic; Production; Optimisation; Agitation; Aeration; Arctic; Skógur; Arctic Council; Iceland
• Online Access: http://hdl.handle.net/1946/45739

Thesis approved in partial fulfilment of a double Nordic Master MSc degree in environmental changes at higher latitudes (EnCHiL), from University of Lund and Agricultural University of Iceland. The plastic pollution has become a massive problem in the Arctic, affecting aquatic, and terrestrial ecosystems, the cryosphere, and the atmosphere. One of the solutions proposed by the Arctic Council is to improve waste management by using renewable and sustainable materials. This is where bioplastics reveal their importance. They can be bio-produced by microorganisms from organic waste, they are biodegradable and can be reused. Their production relies on a circular economy system making it sustainable. Here lies the relevance of developing the bioplastic bioproduction and technology. The present research focused on the development of a specific production of polyhydroxyalkanoates (PHAs) from organic waste, in collaboration with the start-up Dionymer (Bordeaux, France). First, the purpose of the study was to up scale the process from the fermentation of chemical volatile fatty acids in flasks (400 mL culture medium) to 2 L bioreactors (BR) by characterizing the main differences in the two processes. Secondly, the research consisted in implementing and testing different set-up for the BR to enhance and improve bioplastic and biomass yields, including aeration and agitation. The characterization of the culture parameters differences between BR and flask pointed out; a higher viscosity of the medium at the end of the process, a darker PHA product and a lower final optical density (OD) (8 versus 12) respectively. Secondly, the focus was on the increase of the OD in BR and finding the origin of the stress, to do so, the following parameters were tested; - three aerations strategies; pO220%; - two agitations blades; marine and Rushton with baffles; - two aerations spargers; circular and micro. The results revealed that; the pO2 needs to be higher to 20% and it may be linked with the reduction of stress induced to the cells; ...