Pond Photobioreactor Research Articles

Biomass productivity of Scenedesmus dimorphus (Chlorophyceae) was improved by using an open pond–photobioreactor hybrid system

ABSTRACTThe industrialization of microalgae-based biofuel production has been hampered by low biomass productivity of conventional open ponds. In this research, a hybrid cultivation system that combined an open pond and photobioreactor (PBR), with broth circulating between both, was introduced. The hybrid system was tested under indoor and outdoor conditions using the oleaginous microalgal species Scenedesmus dimorphus. When the PBR(s) in the hybrid system reinforced the light supply to the carbon-replete open pond the biomass reached 1.34 g l–1, 116% higher than in the non-hybrid system. Subsequent studies showed that higher circulation speed and low volume ratio of PBR vs. open pond would further improve the hybrid effects. When applied outdoors at pilot scale, the biomass productivity of the hybrid system increased 46.3–74.3% compared with the open pond and in September was 12.5% higher than that of PBRs. These results indicate that hybrid cultivation might be a cost-effective way to improve the light usage efficiency of current open pond systems.

Technical-economic Prefeasibility Study of Astaxanthin Production System from�H. pluvialMicroalgae in Colombia

Background: Nowadays, microalgae has been considered as source of valuable products such as astaxanthin, which is a carotenoid with great commercial potential as antioxidant widely used in many industries such as pharmaceutical, cosmetics and health supplement. Objectives: This work was focused on technical-economic pre-feasibility study of hybrid system for cultivation, harvesting and extraction of astaxanthin from H. pluvialis microalgae in five Colombian cities (Barranquilla, Cartagena, Santa Marta, Barrancabermeja and Cucuta). Methods/Analysis: A hybrid system was purposed based on flat panel + open pond Photo Bioreactor (PBR), in which cell growth is inhibited by increasing radiation. Additional stages as centrifugation, filtration, and drying, milling and supercritical extraction were also implemented. An economic prefeasibility study was applied in order to determine the suitability of locations in terms of NPV, IRR and PP. Findings: It was found that the most feasible location for astaxanthin production is Santa Marta with NPV, IRR and PP of € 5,529,203, 50% and 1.9 years, respectively. Novelty/Improvement: These results suggested that astaxanthin can satisfy national demand of antioxidants by producing it from H. pluvialis microalgae. Keywords: Antioxidant, Astaxanthin, H. pluvialis, Microalgae, Technical-economic Prefeasibility

Computational and experimental studies of high depth algal raceway pond photo-bioreactor

Abstract Microalgae are promising candidate for biofuels as well as precursors for many high value products like polyunsaturated fatty acids, pigments or polysaccharides. Major cultivation of microalgae is carried out in open raceway ponds. Conventional raceway pond designs with paddle wheels have limitations such as high capital investment, inefficient mixing, lower depth (approximately 0.3 m) and lower productivity. In the present work, a modified high depth (1 m) raceway pond design with side entry axial flow impeller has been studied. The higher depth decreases the land requirement as well as capital cost. The pilot scale (4.5 m3) studies for cultivation of Spirullinaplatensis in nutrient rich Zarrouk's culture media have shown productivity of 21.22 gm/m2/day compared to 11.05 gm/m2/day in convectional raceway ponds. The specific power consumption was found to be 4 W/gm in modified design compared to 6 W/gm in conventional design. Computational Fluid Dynamics (CFD) analysis shows that modified design minimized the excessive turbulence generation and provided higher convective currents keeping biomass in suspension. The simulation results have been validated with ultrasonic velocity profiler (UVP) and particle image velocimetry (PIV) measurements.

Studies on light intensity distribution inside an open pond photo-bioreactor.

Light intensity profiles inside an open tank were studied using ANSYS Fluent. Experiments were performed by taking Scenedesmus arcuatus, green microalgae at three different concentrations under actual sunlight conditions. Absorption of light intensity at different depths was measured experimentally. The results generated from CFD simulations were compared with the experimental results and the cornet model. It has been found that there is a good agreement between the light intensity profile obtained from the CFD simulation and that calculated using the Cornet's model. Light intensity profiles at different depths were calculated using CFD simulation by varying the dimensions of the tank. The effect of wall reflectivity, diffuse fraction and scattering phase function on light profile in side open tank are also studied using CFD simulation.

Autotrophic production of biodiesel from microalgae: An updated process and economic analysis

A technical evaluation of a plant for biodiesel production from microalgae was investigated in which a novel configuration of a CPR (closed pond photobioreactor) is proposed. The entire process was simulated by Aspen Plus® and optimized energetically in order to obtain the best profits in energy terms.The design and sizing of the process equipment was performed to obtain a realistic estimation of costs, considering both CAPEX (capital costs) and OPEX (operating costs). The economic analysis evaluated the profitability of the complete process at industrial scale referred to a CPR of 1 km2 of surface area as the base for calculation. In order to ensure an acceptable economic profitability a sale price of oil of $ 18.35/gal was obtained, corresponding to $ 21.11/gal of biodiesel.These results were compared to those of other recent studies, confirming that at the current state of technology the production of biodiesel from microalgae is not competitive with respect to that of conventional diesel, and a breakthrough in technology is needed to bridge this gap maybe by means of other valuable co-products from the same process. A future outlook is eventually reported.

High Concentration of Carbon Dioxide Sequestrated by Microalgae in A Closed Raceway Pond Photobioreactor

CO2 is the main greenhouse gas leading to global warming. Sequestration strategies of CO2 have become a popular research topic around the world. Among them, CO2 biofixation by microalgae is thought to be one of the most effective carbon sequestration means. The flue gas from power plant or waste gas from industry normally contains concentrated CO2 with concentrations varied from 10% to 95%. In the present study, microalgae growth in a closed raceway pond aerated with high concentration of CO2 (100%) was examined. The experimental results showed that in the closed raceway pond, microalgae can grow with 100% CO2 and grow well under certain condition. The present study proved the feasibility of using microalgae for sequestration of concentrated CO2 emitted from industrial plants.