Search Results (8)

Microalgae and their bioproducts have diverse applications, including wastewater remediation, CO₂ fixation, and the synthesis of nutraceuticals, pharmaceuticals, and biofuels. However, the production of these organisms heavily relies upon environmental conditions, which can significantly impact growth. Furthermore, microalgae cultivation itself can be a source of economic and environmental concerns. Thus, microalgae growth systems have become a critical consideration for both research and industry, to bolster microalgae cultivation and address its accompanying issues. Both open and closed systems, such as raceway ponds and photobioreactors, respectively, are commonly used during the growth process but have their own advantages and drawbacks. However, for microalgae growth, photobioreactors may address most concerns as the system’s design lowers the risk of contamination and provides the ability to control the delivery of desired growth factors. To determine the appropriate system for targeted microalgae cultivation, it is crucial to determine factors such as the scale of cultivation and growth and productivity targets. Additionally, efficient usage of these growth systems and carefully selected incubation factors can aid in addressing some of the economic and environmental issues associated with microalgae production. This review will summarize the current applications of bioreactors in both research and industrial capacities and summarize growth and incubation factors for microalgae. Full article

Additive manufacturing (AM) or 3D printing offers a new paradigm for designing and developing chemical reactors, in particular, prototypes. The use of 3D printers has been increasing, their performance has been improving, and their price has been reducing. While the general trend is clear, particular applications need to be assessed for their practicality. This study develops and follows a systematic approach to the prototyping of Advanced Oxidation Processes (AOP) reactors. Specifically, this work evaluates and discusses different printable materials in terms of mechanical and chemical resistance to photo-Fenton reactants. Metallic and ceramic materials are shown to be impracticable due to their high printing cost. Polymeric and composite materials are sieved according to criteria such as biodegradability, chemical, thermal, and mechanical resistance. Finally, 3D-printed prototypes are produced and tested in terms of leakage and resistance to the photo-Fenton reacting environment. Polylactic acid (PLA) and wood–PLA composite (Timberfill^®) were selected, and lab-scale raceway pond reactors (RPR) were printed accordingly. They were next exposed to ${\mathrm{H}}_2{\mathrm{O}}_2$/Fe(II) solutions at pH = 3 ± 0.2 and UV radiation. After 48 h reaction tests, results revealed that the Timberfill^® reactor produced higher Total Organic Carbon (TOC) concentrations (9.6 mg·L⁻¹) than that obtained for the PLA reactor (5.5 mg·L⁻¹) and Pyrex^® reactor (5.2 mg·L⁻¹), which suggests the interference of Timberfill^® with the reaction. The work also considers and discusses further chemical and mechanical criteria that also favor PLA for 3D-printing Fenton and photo-Fenton reactors. Finally, the work also provides a detailed explanation of the printing parameters used and guidelines for preparing prototypes. Full article

There is a groundswell of interest in applying phototrophic microorganisms, specifically microalgae and cyanobacteria, for biotechnology and ecosystem service applications. However, there are inherent challenges associated with conventional routes to their deployment (using ponds, raceways and photobioreactors) which are synonymous with suspension cultivation techniques. Cultivation as biofilms partly ameliorates these issues; however, based on the principles of process intensification, by taking a step beyond biofilms and exploiting nature inspired artificial cell immobilisation, new opportunities become available, particularly for applications requiring extensive deployment periods (e.g., carbon capture and wastewater bioremediation). We explore the rationale for, and approaches to immobilised cultivation, in particular the application of latex-based polymer immobilisation as living biocomposites. We discuss how biocomposites can be optimised at the design stage based on mass transfer limitations. Finally, we predict that biocomposites will have a defining role in realising the deployment of metabolically engineered organisms for real world applications that may tip the balance of risk towards their environmental deployment. Full article

The goal of this work is to design a supply chain network that distributes algae biomass from supply locations to meet biodiesel demand at specified demand locations, given a specified algae species, cultivation (i.e., supply) locations, demand locations, and demand requirements. The final supply chain topology includes the optimum sites to grow biomass, to extract algal oil from the biomass, and to convert the algae oil into biodiesel. The objective is to minimize the overall cost of the supply chain, which includes production, operation, and transportation costs over a planning horizon of ten years. Algae production was modeled both within the U.S. State of Oklahoma, as well as the entire contiguous United States. The biodiesel production cost was estimated at $7.07 per U.S. gallon ($1.87 per liter) for the State of Oklahoma case. For the contiguous United States case, a lower bound on costs of $13.68 per U.S. gallon ($3.62 per liter) and an upper bound of $61.69 ($16.32 per liter) were calculated, depending on the transportation distance of algal biomass from production locations. Full article

Fresh pig urine is unsuitable for microalgae cultivation due to its high concentrations of NH₄⁺-N, high pH and insufficient magnesium. In this study, fresh pig urine was pretreated by dilution, pH adjustment, and magnesium addition in order to polish wastewater and produce microalgae biomass. Chlorella vulgaris was cultured in an in-house-designed light-receiving-plate (LRP)-enhanced raceway pond to treat the pretreated pig urine in both batch and continuous mode under outdoor conditions. NH₄⁺-N and TP in wastewater were detected, and the growth of C. vulgaris was evaluated by chlorophyll fluorescence activity as well as biomass production. Results indicated that an 8-fold dilution, pH adjusted to 6.0 and MgSO₄·7H₂O dosage of 0.1 mg·L⁻¹ would be optimal for the pig urine pretreatment. C. vulgaris could stably accumulate biomass in the LRP-enhanced raceway pond when cultured by both BG11 medium and the pretreated pig urine. About 1.72 g·m⁻²·day⁻¹ of microalgal biomass could be produced and 98.20% of NH₄⁺-N and 68.48% of TP could be removed during batch treatment. Hydraulic retention time of 7-9d would be optimal for both efficient nutrient removal and microalgal biomass production during continuous treatment. Full article

Raceways ponds are the microalgal production systems most commonly used at industrial scale. In this work, two different raceway configurations were tested under the same processing conditions to compare their performance on the production of Nannochloropsis oceanica. Biomass productivity, biochemical composition of the produced biomass, and power requirements to operate those reactors were evaluated. Water depths of 0.20 and 0.13 m, and culture circulation velocities of 0.30 and 0.15 m s⁻¹ were tested. A standard configuration, which had a full channel width paddlewheel, proved to be the most energy efficient, consuming less than half of the energy required by a modified configuration (had a half channel width paddlewheel). The later showed to have slightly higher productivity, not enough to offset the large difference in energetic consumption. Higher flow velocity (0.30 m s⁻¹) led to a 1.7 g m⁻² d⁻¹ improvement of biomass productivity of the system, but it increased the energy consumption twice as compared to the 0.15 m s⁻¹ flow velocity. The latter velocity showed to be the most productive in lipids. A water depth of 0.20 m was the most suitable option tested to cultivate microalgae, since it allowed a 54% energy saving. Therefore, a standard raceway pond using a flow velocity of 0.3 m s⁻¹ with a 0.20 m water depth was the most efficient system for microalgal cultivation. Conversely, a flow velocity of 0.15 m s⁻¹ was the most suitable to produce lipids. Full article

A current concern is the increase in greenhouse gas emissions, mainly CO₂, with anthropogenic sources being the main contributors. Microalgae have greater capacity than terrestrial plants to capture CO₂, with this being an attraction for using them as capture systems. This study aims at the techno-economic evaluation of microalgae biomass production, while only considering technologies with industrial scaling potential. Energy consumption and operating costs are considered as parameters for the evaluation. In addition, the capture of CO₂ from a thermoelectric plant is analyzed, as a carbon source for the cultivation of microalgae. 24 scenarios were evaluated while using process simulation tools (SuperPro Designer), being generated by the combination of cultivations in raceway pond, primary harvest with three types of flocculants, secondary harvest with centrifugation and three filtering technologies, and finally the drying evaluated with Spray and Drum Dryer. Low biomass productivity, 12.7 g/m²/day, was considered, achieving a capture of 102.13 tons of CO₂/year in 1 ha for the cultivation area. The scenarios that included centrifugation and vacuum filtration are the ones with the highest energy consumption. The operating costs range from US $ 4.75–6.55/kg of dry biomass. The choice of the best scenario depends on the final use of biomass. Full article

This work focuses on designing the optimum raceway pond by considering the effects of sunlight availability, temperature fluctuations, and harvest time on algae growth, and introduces a dynamic programing model to do so. Culture properties such as biomass productivity, growth rate, and concentration, and physical properties, such as average velocity, pond temperature, and rate of evaporation, were estimated daily depending on the dynamic behavior of solar zenith angle, diurnal pattern of solar irradiance, and temperature fluctuations at the location. Case studies consider two algae species (Phaeodactylum. tricornutum and Isochrysis. galbana) and four locations (Tulsa, USA; Hyderabad, India; Cape Town, South Africa; and Rio de Janeiro, Brazil). They investigate the influences of the type of algae strain and geographical location on algae biomass production costs. From our case studies, the combination of I. galbana species grown in Hyderabad, India, with a raceway pond geometry of 30 cm channel depth, about a meter channel width, and 300 m in length, and a harvest interval of every six days yielded the minimum algal biomass production costs. The results of the sensitivity analysis reveal that smaller channel depths and longer ponds (within the ranges considered) are recommended to minimize the net present cost of algae biomass production. Full article