An enclosed rotating floating photobioreactor (RFP) powered by flowing water for mass cultivation of photosynthetic microalgae.

Jim Junhui Huang,Yuan Kun Lee,Gagarin Bunjamin,Edwin Sianguan Teo,Deric Boonhuat Ng

doi:10.1186/s13068-016-0633-8

Abstract

BackgroundThe design of photobioreactor (PBR) for outdoor mass cultivation of microalgae determines the distribution of solar irradiance among cells in the culture, mode of agitation, mass transfer efficacy, and energy consumption, thus determines the productivity of the system and the cost of production. In this study, the concept of a floating photobioreactor with rotation function is proposed. Dunaliella tertiolecta, a model microalga, cultured in the attached vessels was evaluated.ResultsThe rotation of the photobioreactor was powered by flowing water, in this case waves generated through a paddle wheel in an outdoor raceway pond for proof of concept. The rotating floating PBR (RFP) could be powered by natural flowing stream, river, and tidal waves, thus there could be no energy cost for agitation of the cultures in maintaining the cells in suspension. This RFP is characterized by its energy-saving and temperature control properties as well as more homogenous light distribution in the culture as compared to conventional culture systems, such as raceway pond. Maximal cell concentration of 8.38 × 106 cells mL−1, biomass productivity of 3.10 g m−2 day−1, and photosynthetic efficiency of 4.61 % (PAR) were achieved. In addition, satisfactory productivities of D. tertiolecta metabolites including carotenoids, mycosporine-like amino acids and lipids were also obtained.ConclusionsThe RFP, powered by flowing water, creates an innovative culture technology for economical cultivation of microalgal cells and production of microalgal metabolites.

Highlights

The design of photobioreactor (PBR) for outdoor mass cultivation of microalgae determines the distribution of solar irradiance among cells in the culture, mode of agitation, mass transfer efficacy, and energy consumption, determines the productivity of the system and the cost of production
The second benefit of rotating floating PBR (RFP) lies in its temperature control, which is often difficult to achieve in land-based large-scale outdoor PBR
The RFP developed are recommended for installation in flowing brook, river, and channel with stable unidirectional waves, taking advantage of free natural hydraulic energy

Summary

Introduction

The design of photobioreactor (PBR) for outdoor mass cultivation of microalgae determines the distribution of solar irradiance among cells in the culture, mode of agitation, mass transfer efficacy, and energy consumption, determines the productivity of the system and the cost of production. The excessive dependence on fossil fuels since industrial revolution might eventually evolve into energy crisis that was a seriously social problem which would cause economic recession, unemployment, social instability, and even lead to war [1]. For solving such issue, various new bioenergy forms such as bio-hydrogen generated by biophotolysis and photo/dark fermentation, bio-ethanol. Cost of energy to facilitate mass transfer and maintaining algal cells in suspension contribute to as much as 31 % of the production cost based on the most cost-effective tubular photobioreactor, leading to high cost of algal biomass and products [12]

Methods

Results

Conclusion