Photobioreactor System Research Articles

A Strategy to Enhance Photo-Algal Hydrogen Production Using External H+ Ions in a Dual Photobioreactor

The use of microalgae for direct biohydrogen energy generation exhibits significant promise as an alternative to traditional bio-energy production due to zero-emission of CO2. It is known that during photolysis, algae are capable of producing hydrogen (H2) gas instead of oxygen (O2) under enriched acetate conditions by algal fermentative metabolisms [1]. The utilization of acetate as a practical oxygen regulator in photosystem II (PSII), but the algal hydrogen production was relatively low due to the insufficient H+ ions available in the photobioreactor (PBR) [2]. Therefore, given that hydrogen ions from acetate contribute to H2 production, it is still unclear whether supplying additional external H+ ions can enhance H2 production.Here, we demonstrate a feasibility study on improving algal H2 production using a dual PBR system. This system enables the continuous transfer of H+ ions generated from photolysis to an algal H2 PBR through a proton exchange membrane (PEM), thereby enhancing photo-algal hydrogen production. The maximum H2 production of 108 µmol L-1 was obtained for Chlamydomonas reinhardtii in a single PBR for 15 days at a light intensity of 100 µmol m-2 s-1 [3]. However, by leveraging the external H+ ions supply, the dual PBR system increased photo-algal hydrogen production from 108 up to 760 µmol L-1 for the same period, which is 7 times greater compared to single chamber operation. This indicates that supplying external H+ ions in the operation of the dual PBR is one of the important parameters for improving biohydrogen production. Our findings contribute to the ongoing development of high-performance algal H2 production, offering valuable insights into optimizing the amount of H+ ions for enhanced hydrogen production.[1] Clemens KL, Force DA, Britt RD. Acetate binding at the photosystem II oxygen evolving complex: an S2-state multiline signal ESEEM study. J Am Chem Soc. 2002;124(36):10921-33.[2] Hwang J-H, Church J, Lim J, Lee WH. Photosynthetic biohydrogen production in a wastewater environment and its potential as renewable energy. Energy. 2018;149:222-9.[3] Hwang J-H, Lee WH. Continuous photosynthetic biohydrogen production from acetate-rich wastewater: Influence of light intensity. Int J Hydrogen Energy. 2021;46(42):21812-21.

Advanced membrane photobioreactors in algal CO2 biofixation and valuable biomass production: Integrative life cycle assessment and sustainability analysis

This paper presents and discusses the life cycle assessment (LCA) of CO2 capture and of microalgae biomass production in an advanced membrane photobioreactor (mPBR) system for climate change mitigation and the generation of renewable energy carriers. The study aims to evaluate environment-relevant aspects and propose alternative solutions for optimization of the environmental sustainability of the biologically based technology. The mPBR biotechnology, composed by an adsorption column, coupled with a reactor with a self-forming dynamic membrane (SFDM) module inside, was used for the experimental activities. Four principal operational steps (cultivation, harvesting, cleaning and drying) at three different scenarios were investigated and evaluated in terms of energy demand and environmental impacts amongst the boundary conditions based on the “cradle-to-gate” model. The ReCiPe 2016 and the Cumulative Energy Demand (CED) methodologies were applied for the assessment. In addition, a sensitivity analysis has been conducted.The results showed that across the operational phases, algae cultivation and drying are the most phases that lead to greater environment-relevant aspects. Analysing different scenarios, the use of wastewater as a source of nutrients for algae (Chlorella vulgaris species), with respect to the use of synthetic nutrients with the same biomass productivity, resulted to be the most feasible and attractive alternative in terms of environmental impact. Finally, the sensitivity analysis highlighted how the environmental performance can be significantly improved by enhancing the productivity and the harvesting rate.The study provides important information to the different actors involved in the biotechnologies sectors, to be able to build and/or evaluate different production options with a holistic and proactive approach, in order to optimize the technologies with a view to maximize its environmental sustainability.

Effect of culture hydrodynamics on Arthrospira platensis production using a single-use photobioreactor system through a CFD supported approach.

Laboratory scale conventional single-use bioreactor was used to investigate the effect of different stirrer speeds on the Arthrospira platensis (Spirulina platensis) culture. Experiments were handled in two steps. First step was the selection of the stirring speeds, which was simulated via using CFD, and the second was the long term cultivation with the selected speed. During 10 days of batches as the first step, under identical culture conditions, stirrer speed of 230 rpm gave higher results, compared to 130 and 70 rpm, with respect to dry biomass weight, absorbance value (AB) and chlorophyll-a concentration. Volumetric productivity during the growth phase of the cultures were calculated as 0.39 ± 0.03, 0.28 ± 0.01, and 0.19 ± 0.02 g L-1 d-1, from the fast to the slower speeds. According to the results a 17 day batch was handled with 230 rpm in order to monitor the effects on the culture. The culture reached a volumetric productivity of 0.33 ± 0.04 g L-1 d-1. Statistical analysis showed the significance of the parameters related with the stirring speed.

Pseudomonas putida as saviour for troubled Synechococcus elongatus in a synthetic co-culture – interaction studies based on a multi-OMICs approach

In their natural habitats, microbes rarely exist in isolation; instead, they thrive in consortia, where various interactions occur. In this study, a defined synthetic co-culture of the cyanobacterium S. elongatus cscB, which supplies sucrose to the heterotrophic P. putida cscRABY, is investigated to identify potential interactions. Initial experiments reveal a remarkable growth-promoting effect of the heterotrophic partner on the cyanobacterium, resulting in an up to 80% increase in the growth rate and enhanced photosynthetic capacity. Vice versa, the presence of the cyanobacterium has a neutral effect on P. putida cscRABY, highlighting the resilience of pseudomonads against stress and their potential as co-culture partners. Next, a suitable reference process reinforcing the growth-promoting effect is established in a parallel photobioreactor system, which sets the basis for the analysis of the co-culture at the transcriptome, proteome, and metabolome levels. In addition to several moderate changes, including alterations in the metabolism and stress response in both microbes, this comprehensive multi-OMICs approach strongly hints towards the exchange of further molecules beyond the unidirectional feeding with sucrose. Taken together, these findings provide valuable insights into the complex dynamics between both co-culture partners, indicating multi-level interactions, which can be employed for further streamlining of the co-cultivation system.

Sub-pilot scale sequential microalgal consortium-based cultivation for treatment of municipal wastewater and biomass production

Municipal wastewater (MWW) was treated by a sequential pilot microalgal cultivation process. The cultivation was performed inside a specifically designed low-cost photobioreactor (PBR) system. A microalgal consortium 2:1 was developed using Tetraselmis indica (TS) and Picochlorum sp. (PC) in the first stage and PC:TS (2:1) in the second stage and the nutrient removal efficiency and biomass production and biomolecules production was evaluated and also compared with monoculture in a two-stage sequential cultivation system. This study also investigated the effect of seasonal variations on microalgae growth and MWW treatment. The results showed that mixed microalgal consortium (TS:PC) had higher nutrient removal efficiency, with chemical oxygen demand (COD), total phosphate (TP), and total nitrate (TN) removal efficiencies of 78.50, 84.49, and 84.20%, respectively, and produced a biomass of 2.50 g/L with lipid content of 37.36% in the first stage of cultivation under indoor conditions. In the second stage of indoor cultivation, the PC:TS consortium demonstrated maximum COD, TP, and TN removal efficiencies of 92.49, 94.24, and 94.16%, respectively. It also produced a biomass of 2.65 g/L with a lipid content of 40.67%. Among all the seasonal variations, mass flow analysis indicated that the combination of mixed consortium-based two-stage sequential process during the winter season favored maximum nutrient removal efficiency of TN i.e. 88.54% (84.12 mg/L) and TP i.e., 90.18% (43.29 mg/L), respectively. It also enhanced total biomass production of 49.10 g in 20-L medium, which includes lipid yield ∼15.68 g compared to monoculture i.e., 82.06% (78.70 mg/L) and 82.87% (40.26 mg/L) removal of TN and TP, respectively, and produced biomass 43.60 g with 11.90 g of lipids.

Effect of Audible Sound Exposure on the Growth and Lipid Content of Chlorella DPK-01 Cultivated in Photobioreactor System using Different Growth Media

Effect of Audible Sound Exposure on the Growth and Lipid Content of Chlorella DPK-01 Cultivated in Photobioreactor System using Different Growth Media

Data-driven recurrent neural networks modeling of cyanobacteria growth in bubble columns reactors under sparging with CO2-enriched Air

Cultivating carbohydrate-enriched microalgae in photobioreactors is a recognized method for converting atmospheric carbon dioxide (CO2) into valuable resources, offering a solution to combat industrial CO2 emissions. Achieving global carbon neutrality by 2050 necessitates an annual reduction of approximately 1.4 gigatons of CO2. To address this challenge, we developed a machine learning-based black box model using data from the Institute of Advanced Materials for Sustainable Manufacturing at ITESM. This dataset encompasses hourly operational parameters collected over eleven months, including temperature, pressure, and flow rate. These parameters were essential for a microalgal cultivation experiment using the cyanobacterium Desertifilum tharense and CO2-enriched air. Two 100-L photobioreactor systems were employed. Leveraging the sequential dataset, we deployed a long short-term memory network (LSTM) to predict CO2 percentages at reactor outlets, indirectly indicating algae biomass production. Seven input variables were selected on the basis of their impact on system behavior. Using advanced machine learning time series mathematical models can boost process intensification tasks through advanced process optimization, simulation, and control goals.

Towards Optimisation of Microalgae Cultivation through Monitoring and Control in Membrane Photobioreactor Systems

This research lays a foundation for optimised membrane photobioreactor performance and introduces novel control parameters crucial for advancing microalgae cultivation techniques and promoting environmental sustainability. Particularly, this study presents an innovative solids retention time (SRT) controller designed for a pilot-scale membrane photobioreactor. Employing a fuzzy-logic knowledge-based approach, this controller uses the first derivative of pH data dynamics (pH′) as an input variable, directly correlated with nitrogen recovery rate and biomass productivity when normalised by average light irradiance (I2). Through a feedback mechanism, it regulates daily SRT variations, ensuring stable reactor operation, optimal volatile suspended solids concentration, efficient nitrogen removal, and enhanced biomass productivity. Normalised nitrogen recovery rate, considering solar light irradiance and volatile suspended solids concentration, increased by 51% compared to previous studies employing fixed SRT and hydraulic retention time (HRT). Combining this SRT controller with a previously studied HRT controller could potentially amplify biomass productivity efficiency. In addition, controlling or not controlling the HRT and SRT are assessed in terms of filtration performance and GHG emissions. Finally, a new dissolved-oxygen-based parameter shows promise for continuous microalgae culture control.

SẢN XUẤT SINH KHỐI TẢO Nannochloropsis oculata QUY MÔ HÀNG HÓA TẠI HUYỆN QUỲNH LƯU, NGHỆ AN

The research was conducted to complete technological protocol of biomass production of algae Nannochloropsis oculata with both culture methods in plastic bags and photo-bioreactor systems. The results show that in the nylon bag system, algae reached a peak of biomass density at day-8 of culture with 80 million cells per ml. In the photo-bioreactor systems, algae were higher density (180 million cells per ml), and longer period of culture (15 days of culture) than in plastic bags. The total products of 404.4 kg of fresh concetrated algae and 57.6 kg of dried algae powder which were suitable produced under climate conditions in Nghe An. All the algae products met the quality and requirements for use as food for aquatic animals as well as raw materials for the production of functional foods for humans.

A Microalgae Photobioreactor System for Indoor Air Remediation: Empirical Examination of the CO2 Absorption Performance of Spirulina maxima in a NaHCO3-Reduced Medium

Microalgae-based photobioreactors (PBRs) have gained attention as a sustainable solution for indoor air quality (IAQ) control. This study investigates indoor CO2 absorption performance of Spirulina maxima (S. maxima) in NaHCO3-limited cultivation (standard: NaHCO3-free medium = 1:1 v/v%) of a lab-scale PBR system. Cultivation performance of three medium amendments (standard, 50% NaHCO3, and NaHCO3-free) was compared by observing cell growth for 30 days in a controlled environment. Empirical examinations were conducted to evaluate the algal CO2 uptake, and overall system performance in the culture volumes of 2, 4, and 7 L and natural indoor CO2 concentration of ~1100 ppm. We found CO2 was reduced by ~55%, in an air chamber of 0.064 m3, showing the greatest mitigation rate (~20%) on Day 4. Under a high concentration of CO2 (10,000 ppm), the CO2 levels were decreased up to ~90% before saturation. This research provides valuable insights into the development of S. maxima-activated IAQ control systems for airtight buildings.

Microalgae cultivation in flat panel photobioreactor as a method of carbon capture: A review

Biomass is one of the renewable energy technologies that plays a crucial role in fulfilling our energy needs while helping to mitigate carbon release. Microalgae biomass is a valuable product that can be utilized for a variety of applications which are generally high in proteins, carbohydrates, and lipids. In relation to that, photobioreactor (PBR) is known to be the appropriate system for microalgae to grow efficiently under controlled conditions. Nevertheless, handling this system can be challenging due to its complexity since it operates through different physical and chemical processes. This paper describes a systematic review of the recent literature published on flat panel photobioreactor (FPPBR) systems for microalgae cultivation that served as one of the critical technologies for the sustainable production of microalgae biomass and bio-based products. A total of 115 publications have been identified and analyzed from the literature search focusing on identifying different designs of FPPBR that have been developed and validated experimentally and numerically. Ultimately, this review is able to provide valuable insights into the current state of FPPBR implementation for microalgae cultivation that can aid in sorting out new strategies to support climate change attenuation and the commercialization of microalgae-based products.

Exploring advanced phycoremediation strategies for resource recovery from secondary wastewater using a large scale photobioreactor

This study aimed to investigate the operation of a 1000L microalgae-based membrane photobioreactor system in a greenhouse for continuous secondary wastewater treatment using Desmodesmus sp., a green microalgae strain originally isolated from a German sewage plant. The research spanned both summer and winter seasons, seeking to comprehend key trends and optimization strategies. Maintaining low cell concentrations in the photobioreactor during periods of light inhibition proved advantageous for nutrient uptake rates. Effective strategies for enhancing algae-based wastewater treatment included cell mass recycling, particularly during periods of high light availability. In comparison to conventional continuous cultivation methods, employing cell recycling and high dilution rates during times of abundant light, alongside using low cell concentrations and dilution rates during light inhibition, resulted in an 80 % and 10 % increase in overall biomass productivity during summer and winter, respectively. Furthermore, nitrogen/phosphorus (N/P) removal rates exhibited a 23 % improvement during winter, while remaining unchanged in summer.

A modelling workflow for quantification of photobioreactor performance

In this work we have developed a comprehensive modelling workflow for the quantification of photobioreactor performance. Computational Fluid Dynamics (CFD) modelling combined with Lagrangian particle tracking was used to characterise the flow field inside the reactor; this information was combined with a Monte-Carlo model of light attenuation and a kinetic growth model to predict the performance of the system over the duration of the entire batch. The CFD model was validated against measurements of the overall hold-up, local hold-up and mixing time for superficial velocities between 0.6 and 6 cm s−1 in a pilot-scale bubble column photobioreactor, with the CFD predictions agreeing with the experimental data. Comparison was also made between the predicted biomass concentration and experimental measurements using the diatom Phaeodactylum tricornutum, with the model predictions being in good agreement with the experimental results. The model was used to investigate a range of operating conditions and reactor designs, with the most promising predicted to give a 40 % increase in the biomass productivity. Results from this work can be used for the in-silico design and optimisation of photobioreactor systems, thereby enabling their wider use as a sustainable production technology.

Stability Assessment of Microalgal Photobioreactors for Carbon Dioxide Capture under Dilution Rate Constraints

Algal cultivation is a sustainable approach which can be used not only for carbon dioxide sequestration but also for making useful products in many industries. To facilitate the widespread adoption of this approach, the current research studies the stable control of closed photobioreactors (PBRs) cultivating microalgae. More specifically, a proportional–integral (PI) controller is employed for the tracking of the microalgal concentration to a desired reference corresponding to a required amount of sequestrated carbon dioxide. In the presence of the practically positive and bounded constraints of the dilution rate, the stability and reference tracking of the closed-loop PBR system needs to be assessed. This work then derives conditions under which a unique equilibrium point exists and the closed-loop PBR system is asymptotically stable around such an equilibrium point. The derived theoretical results are validated and illustrated through numerical simulations for PBRs of the microalgae Chlorella vulgaris.

Development of yeast and microalgae consortium biofilm growth system for biofuel production

BackgroundThe current study aimed to develop a laboratory-scale biofilm photobioreactor system for biofuel production. Scope & ApproachDuring the investigation, Jute was discovered to be the best, cheap, hairy, open-pored supporting material for biofilm formation. Microalgae & yeast consortium was used in this study for biofilm formation. ConclusionThe study identified microalgae and yeast consortium as a promising choice and ideal partners for biofilm formation with the highest biomass yield (47.63 ± 0.93 g/m2), biomass productivity (4.39 ± 0.29 to 7.77 ± 0.05 g/m2/day) and lipid content (36%) over 28 days cultivation period, resulting in a more sustainable and environmentally benign fuel that could become a reality in the near future.

Practical Design of Hybrid Photobioreactor System for Economic Feasibility and Environmental Sustainability

Modern photobioreactors for microalgae-based biofuel production face various budgetary challenges in comparison to its competitor design, the traditional open pond system. Herein, a novel design of a double-chamber hybrid photobioreactor is proposed, featuring low-cost components including a 3-W centrifugal pump and recyclable plastic modules for its solar flank, as well as derivatives from tubular and membrane photobioreactors. The hybrid photobioreactor exhibits reasonable hydrodynamic performance with a circulation time of 120 seconds and a mixing time of 38 seconds. A side-by-side runthrough of Chlorella vulgaris cultivation with the novel hybrid photobioreactor and a standard open pond system was done to compare growth rates and system performance under equal environmental conditions. Resulting measurements show that the hybrid photobioreactor produced a 34.87% comparatively greater amount of C. vulgaris by the tenth day of cultivation, demonstrating a significantly higher growth rate (P < 0.05). In contrast, wet-sludge lipid extraction processes show that the C. vulgaris culture grown in the open pond system held a substantially larger lipid accumulation than that of the hybrid photobioreactor, although the difference was not statistically significant (P > 0.05). The pilot-scale photobioreactor not only costed as little as the open pond system but also incurred 88.6% less expenses compared to a similarly designed bioreactor made of clear PVC material. Consequently, this project demonstrates the candidacy of the proposed low-cost hybrid photobioreactor design for microalgal biofuel production.

Organic loads reduction efficiency using natural fiber reinforced polymer encapsulated microalgae macrocapsule for wastewater treatment

Organic load such as Chemical Oxygen Demand (COD) increases in the water because of the increase in human growth and industrialisation. The initial goal of the study, to characterise the natural fibre reinforced polymer encapsulated microalgae macrocapsule using Scanning electron microscope (SEM). Second, analyse organic load reduction utilising natural fiber reinforced polymer encapsulated microalgae macrocapsule. The experiment was conducted with five Schott bottles with a 1.7 liter working volume as a photobioreactors. The system was operated with three tubes fabricated with different functions. The first tube was connected to the adjustable air pump oxygen aerator to supply oxygen into the photobioreactor system. The photobioreactor’s second tube is designed to flow out gasses. The last tube is the sampling tube function to withdraw the samples for the efficacy of treatment performance. The photobioreactor will continuously be illuminated with cool-white fluorescent light (Philip TL-D 36W/865, light intensity of 60–70 μmol m-2 s-1). This study employs COD to test microalgae’s organic load reduction. From day 1 to 5, COD value shows a pattern of reduction from 352 mg/L for day 1 and 223 mg/L for day 5, respectively. The analysis reveals that the p-OPEFB (Polymeric Oil Palm Empty Fruit Bunch) macrocapsule has a surface structure with a rough surface before and after treatment. Optical density measures microalgae growth. BBM’s (Bold Basal Medium) increasing absorbance value allows microalgae to develop optimally. Natural fibre reinforced polymer encapsulated microalgae macrocapsule shows potential for wastewater treatment.

Transdisciplinary collaboration in architecture: Integrating microalgae biotechnologies for human and non-human perspectives

Abstract This article investigates the role of architectural research in addressing the current ecological, geopolitical, and socioeconomic challenges by exploring the potential of symbiotic ecosystems, particularly microorganisms such as microalgae, in architectural and design applications. Microalgae biotechnologies have the potential to offer a wide range of applications in architecture and design, encompassing small-scale objects, living systems on building exteriors, as well as urban and rural scenarios, thereby allowing for systematic research. When using these biotechnologies in architectural designs, it is crucial to consider maintenance requirements, environmental impacts, and the potential for enhancing public spaces and society across various dimensions in both short-term and long-term perspectives, and potential environmental impacts before implementing microalgae-based systems in real-life scenarios. This study describes a collection of interdisciplinary projects and research that involve microbiology, architecture, and design and proposes various experimental scenarios concerning the integration of both human and non-human perspectives. Through collaborative academic efforts, these projects demonstrate the potential for combining microalgae cultivation with architectural applications. The projects include Photosynthetic Landscape, a modular photobioreactor system, Synthesizing/Distancing which addresses coexistence in global epidemics, Biotopia, a permanent interior installation incorporating microalgae, Exchange Instruments, a semi-closed cultivation system, and Cultivated Environment, a small-scale microalgae cultivation apparatus. The article highlights the implication of controlled environments, maintenance, and interdisciplinary cooperation while showcasing the potential for these systems.

A sequential electrochemical oxidation – algal photobioreactor system for the treatment of distillery wastewater

A sequential electrochemical oxidation (EO) and algal bubble column photobioreactor (BPBR) system was proposed to treat distillery wastewater (DWW). EO was carried out in a 2 L reactor with Ti-RuO2 anodes. Electrochemically oxidised DWW (EO-DWW) was then supplied to the microalgae Asterarcys quadricellulare. The EO operating current, treatment time and post-treatment dilution were optimised with a central composite design (CCD) with algal specific growth rate, lipid accumulation and photosynthetic quantum yield (Fv/Fm) as dependent variables. The optimal treatment conditions for the growth of A. quadricellulare were 27 A for 26 h and a post-treatment dilution of 8. Under optimal conditions, A. quadricellulare grew at a specific growth rate of 1.06 d−1 with a lipid accumulation of 12.7% and an Fv/Fm of 0.7. The optimal conditions were validated, and a 1.6 L bubble column photobioreactor was designed to treat the EO-DWW sequentially. The sequential EO-BPBR system removed 92% COD, 76% TOC and 82% TN from DWW. The algal biomass productivity was 0.96 g/L/d with a carbon sequestration of 550–700 mg/L/d and an aqueous carbon capture of 240–280 mg C/L/d. Additionally, the flue gas evolved from the EO reactor was analysed and contained 68% H2, 18% O2 and 12.5% CO2. The H2 in the flue gas can compensate for 26.5% of the energy spent for the EO process. The algal biomass produced in the sequential process can compensate for 6% of the total energy consumed for EO. Therefore, 32% of the energy spent on EO can be reclaimed by sequential EO-BPBR treatment.

A preliminary techno-economic analysis of photofermentative hydrogen production

Photofermentative hydrogen production promises sustainable energy using cheap feedstock and sunlight. While successful laboratory and pilot-scale photofermentative production studies are widespread, overall economic feasibility remains to be demonstrated. In this study, a preliminary techno-economic analysis of photofermentative production based on current technology was carried out, and the results were compared to alternatives such as photovoltaic electrolysis.Specific photofermentative hydrogen cost was estimated based on an existing outdoor, pilot-scale (20 L) photobioreactor system. The annual capital cost was calculated as 124 USD/year including equipment and land. Operating cost was calculated as 42 USD/year including maintenance, energy consumption and feedstock. The specific hydrogen production cost was found as 2.7 USD/mol (1362 USD/kg H2), and 395 USD/kg H2 when equipment cost is subsidized. Further analysis shows that utilization of wastewater as feedstock and a boost in hydrogen productivity could reduce specific cost of hydrogen to levels competitive with alternative technologies.