Enhancing microalgae attachment for biofilm-based photobioreactors

• Main Author: Bhaiji, Tasneem
• Other Authors: Zhang, Qi ; Kirby, Paul B.
• Published: Cranfield University 2016
• Subjects: 662
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685597

The potential of algal biofuels has been technically and experimentally confirmed with laboratory- and pilot-scale studies in past literature. However, the most important factor now is to confirm that algal cultivation for biofuels and other end-products is economically feasible on the large, commercial scale. The ALGADISK project aimed to produce a novel biofilm-based photo-bioreactor with the aims of CO2 capture and making valuable products such as biofuel, economically viable. This thesis aimed to investigate and provide substrates in which algae biofilm is stimulated and increased. Polyelectrolyte (PE) coatings adsorbed onto cost-effective polymers were investigated, based on the strategy of electrostatic attraction. It was found that the algae species charge density and cell wall functional groups composition affected attachment onto charged PE coatings. Two coatings labeled C1 and C3 were selected due to their promising growth results with the strains C.sorokiniana, C.vulgaris and S.obliquus. Harvesting growth results showed inconsistent regrowth due to the lack of textured structure. Sandpapering the surface with certain grades was found to improve regrowth and consistency. Surface roughness did not show correlation to initial attachment of algae or strength of attachment. It was shown instead that surface roughness improved long-term growth As part of the aims of the ALGADISK project, the coatings large scale potential and cost was optimized. It was found that airbrushing rather than dip-coating, reduced the amount of PE solution needed drastically. Furthermore, photo-cross- linking with UV exposure enhanced the strength of C1 according to scratch and wear data. Lastly, the physico-chemical properties of both algae and substrates were examined in order to examine the thermodynamic model for algae adhesion prediction. It was found that the two thermodynamic approaches tested did not predict algae adhesion results with good accuracy. However, it was revealed that there could be a possible link between the substrate physico-chemistry and lipid content found in the biofilm attached. It was found that the less favorable the predicted thermodynamic conditions the higher the lipid content.