Flotation: A promising microalgae harvesting and dewatering technology for biofuels production

Abstract

Microalgal biomass as renewable energy source is believed to be of great potential for reliable and sustainable biofuels production. However, microalgal biomass production is pinned by harvesting and dewatering stage thus hindering the developing and growing microalgae biotechnology industries. Flotation technology applied in mineral industry could be potentially applied in microalgae harvesting and dewatering, however substantial knowledge on different flotation units is essential. This paper presents an overview on different flotation units as promising cost-effective technologies for microalgae harvesting thus bestowing for further research in development and commercialization of microalgae based biofuels. Dispersed air flotation was found to be less energy consuming. Moreover, Jameson cell flotation and dispersed ozone flotation are believed to be energy efficient microalgae flotation approaches. Microalgae harvesting and dewatering by flotation is still at embryonic stage, therefore extended studies with the focus on life cycle assessment, sustainability of the flotation unit, optimization of the operating parameters using different algal species is imperative. Though there are a number of challenges in microalgae harvesting and dewatering, with well designed and developed cultivation, harvesting/dewatering, extraction and conversion technologies, progressively, microalgae technology will be of great potential for biological carbon sequestration, biofuels and biochemicals production.

Theoretical Calculations on the Feasibility of Microalgal Biofuels: Utilization of Marine Resources Could Help Realizing the Potential of Microalgae

“…Costs for harvesting and transportation of produced biomass are also of concerns. Development of in situ harvest methods, such as floatation, for concentration and dewatering of algal biomass could reduce the cost for transportation . At a full‐scale, construction of an offshore platform adjacent to an offshore algal culture facility would be a more economic option, so that final products, algal biofuel and other byproducts, could be transported as how fossil fuels from offshore platforms are extracted and transported.…”

Implications of Extracellular Polymeric Substance Matrices of Microbial Habitats Associated with Coastal Aquaculture Systems

“…In microalgal aquaculture, flocculation and flotation are two efficient biomass harvesting techniques. The flotation technique occurs when air or gas is transformed into bubbles through a solid/liquid suspension; as a result, solid particles get attached to gaseous molecules and are carried up and accumulated on the surface [160]. In flocculation, the dispersed microalgal cells aggregate and form larger particles with a higher sedimentation rate.…”

Optimization of thermal pre‐flocculation treatment for effective air flotation harvesting of microalgae

“…Flocculating agents alter the cell surface hydrophobicity and improve the floatability of cells . However, some negative consequences are associated with the use of flocculants, such as increased process costs and the creation of secondary pollutants, restricting the potential scope of application …”

“…22 However, some negative consequences are associated with the use of flocculants, such as increased process costs and the creation of secondary pollutants, restricting the potential scope of application. [23][24][25][26][27][28] To avoid these issues, a novel air flotation approach with thermal pre-flocculation treatment was developed to remove Scenedesmus obliquus from suspensions. Laamanen et al 29 proposed an improved method using factory thermal waste gas as a heating source for flotation pretreatment, without the use of surfactants.…”