Outdoor cultivation of Chlorella vulgaris FSP-E in vertical tubular-type photobioreactors for microalgal protein production

Perspectives on cultivation and harvesting technologies of microalgae, towards environmental sustainability and life cycle analysis

The development of algae is seen as a potential and ecologically sound approach to address the increasing demands in multiple sectors. However, successful implementation of processes is highly dependent on effective growing and harvesting methods. The present study provides a complete examination of contemporary techniques employed in the production and harvesting of algae, with a particular emphasis on their sustainability. The review begins by examining several culture strategies, encompassing open ponds, closed photobioreactors, and raceway ponds. The analysis of each method is conducted in a systematic manner, with a particular focus on highlighting their advantages, limitations, and potential for expansion. This approach ensures that the conversation is in line with the objectives of sustainability. Moreover, this study explores essential elements of algae harvesting, including the processes of cell separation, dewatering, and biomass extraction. Traditional methods such as centrifugation, filtration, and sedimentation are examined in conjunction with novel, environmentally concerned strategies including flocculation, electro-coagulation, and membrane filtration. It evaluates the impacts on the environment that are caused by the cultivation process, including the usage of water and land, the use of energy, the production of carbon dioxide, and the runoff of nutrients. Furthermore, this study presents a thorough examination of the current body of research pertaining to Life Cycle Analysis (LCA) studies, presenting a perspective that emphasizes sustainability in the context of algae harvesting systems. In conclusion, the analysis ends up with an examination ahead at potential areas for future study in the cultivation and harvesting of algae. This review is an essential guide for scientists, policymakers, and industry experts associated with the advancement and implementation of algae-based technologies.

Integrating anaerobic digestion and microalgae cultivation for dairy wastewater treatment and potential biochemicals production from the harvested microalgal biomass

Utilizing wastewaters as feedstock for microalgal cultivation has the dual benefits of water-saving and low nutrient costs, with simultaneous remediation of pollutants and generation of value-added biochemical products. This study employed two different strategies to treat raw dairy wastewaters with moderate and high chemical oxygen demand (COD) levels. For moderate-COD dairy wastewater, the wastewater was directly utilized as feedstock for algal cultivation, in which the effects of wastewater dilution ratios and algal inoculum sizes were investigated. The results show that the microalga strain used (Chlorella sorokiniana SU-1) was capable of obtaining a high biomass concentration of 3.2 ± 0.1 g/L, accompanied by 86.8 ± 6%, 94.6 ± 3%, and 80.7 ± 1%, removal of COD, total phosphorus (TP) and total nitrogen (TN), respectively. Meanwhile, the obtained microalgal biomass has lipids content of up to 12.0 ± 0.7% at a wastewater dilution ratio of 50% and an inoculum size of 2 g/L. For high-COD dairy wastewater, an integrated process of anaerobic digestion and microalgal phycoremediation was employed, and the effect of inoculum sizes was also studied. The inoculum size of 2 g/L gave highest biomass production of 4.25 ± 0.10 g/L with over 93.0 ± 2.0% removal of COD, TP, and TN. The harvested microalgal biomass has lipids and protein content of 12.5 ± 2.2% and 18.0 ± 2.2%, respectively. The present study demonstrated potential microalgal phycoremediation strategies for the efficient COD removal and nutrients recovery from dairy wastewater of different COD levels with simultaneous production of microalgal biomass which contains valuable components, such as protein and lipids.

Performance evaluation of algae assisted microbial fuel cell under outdoor conditions

This study reports for the first time an operation of an outdoor algae assisted Microbial Fuel Cell (MFC). The MFC (10 L) comprised of low-cost materials like rock phosphate blended clayware & low-density polyethylene bags as anodic & cathodic chamber respectively. Algae biomass after lipid extraction at 2 g/l served as electron donor at the anode. Chlorella vulgaris at cathode provided oxygen as electron acceptor and served as lipid source. The MFCs performed well in all aspects namely energy recovery, algae productivity, and cost of operation. The 5% RP-MFCs gave 0.307 kg/m³d algal productivity, 0.09 kg/m³d lipid productivity, and 11.5318 kWh/m³ of net energy recovery (NER). Rock phosphate served as a slow and constant source of phosphorus supporting algae growth. Proteobacteria (45.14%) were the dominant phyla while Alicyliphilus (5.46%) and Dechloromonas (4.74%) were the dominant genera at the anode. The estimated cost of the system was $11.225 only.

Cultivation of newly isolated microalgae Coelastrum sp. in wastewater for simultaneous CO2 fixation, lipid production and wastewater treatment

Cultivation of microalgae in wastewater is a promising and cost-effective approach for both CO₂ biofixation and wastewater remediation. In this study, a new strain of Coelastrum sp. was isolated from cattle manure leachate. The isolated microalgae were then cultivated in wastewater. Effects of different sCOD concentrations (600, 750, 900, 1050 mg L^-1) and light intensities (1000, 2300, 4600, 6900 and 10000 Lux) on biomass production, CO₂ consumption rate and nutrient removal from wastewater were investigated. The results showed that maximum cell growth and CO₂ consumption rate were 2.71 g L^-1 and 53.12 mg L^-1 day^-1, respectively, which were obtained in the wastewater with 750 mg L^-1 sCOD and under the light intensity of 6900 Lux. The microalgae were able to completely consume all CO₂ after incubation period of 4 days. The highest sCOD, total Kjeldahl nitrogen (TKN), nitrate and total phosphorous (TP) removal at such conditions were 53.45, 91.18, 87.51 and 100%, respectively. The lipid content of microalgal biomass was also measured under different light intensities; maximum amount of lipid was determined to be 50.77% under illumination of 2300 Lux. Finally, the CO₂ consumption rate and biomass productivity of microalgae in semi-batch culture with continuous gas flow (CO₂ 6%:N₂ 94%) were investigated. The rate of CO₂ consumption and biomass productivity were 0.528 and 0.281 g L^-1 day^-1, respectively. The TKN, nitrate, TP and sCOD removal rate of microalgae were 83.51, 80.91, 100, 41.4%, respectively.