Numerical investigation of a bubble-column photo-bioreactor design for microalgae cultivation (original) (raw)
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2013
Techno-economic and systems studies on microalgal growth scenarios to date are abbreviated and missing a number of important variables. By including these variables in a detailed model integrating biology, chemistry, engineering, and financial aspects, a more defined systems analysis is possible. Through optimizing the model productivity based on the resulting net profit, the system analysis results in a more accurate assessment of environmental and economic sustainability of specific algal growth scenarios. Photobioreactor algal growth scenario optimization in the system model has resulted in realistic engineering design requirements based on algal growth requirements and fluid dynamics analysis. Results show feasibility for photobioreactor growth scenarios to be economically sustainable when co-products are included, but definite technological advancements and productivity improvements must be made. The main factors inhibiting a cost effective photobioreactor growth scenario are culture density, temperature, and lighting distribution for solar illuminated photobioreactors, and lighting cost for artificially illuminated photobioreactors. Open pond algal growth scenarios do not show any prospect of economic or environmental sustainability with current technology due to the large amount of surface area required, inefficient water use, and iii low culture density. All algal growth scenarios are inferior to petro-diesel regarding energy inputs, carbon emissions, and environmental sustainability. No algal growth scenarios analyzed in this study meet the U.S. requirement of biofuel emitting at least 20% less carbon emissions than diesel from crude oil. Dr. Robert M. Dores from the University of Denver, and Larry Clark from Lockheed Martin. Also, my deep appreciation for the assistance of Chad Van Fleet at Mathworks,
Development of industrial scale microalgae production
Introduction and thesis outline Chapter 1 feeds was the improving understanding of the dietary and gnotobiological 1 requirements of marine fish larvae. Aquaculture diets remains today an important market for high-value microalgal products. Current microalgal products. Currently, the global market of autotrophic micro algae is about 30,000 tons of biomass, distributed on only 7 major species (Table 1-1). These are the species that are available on the market; in addition, microalgae are used as live diets in aquatic hatcheries, for example for bivalve rearing, but these algae are mostly produced on-site. Over the past 10 years, the market has approximately tripled but sadly, it remains small, considering the large public interest in microalgae. The species in Table 1-1 are all high-value products for human food supplements or nutraceuticals or special aquafeeds although the Japanese company by the name Euglena company intends to develop its Euglena-product for biofuel. Two of the species, Spirulina and Dunaliella are produced in open ponds under conditions that are rather exclusive to these species, namely high alkalinity (Spirulina) and high salinity (Dunaliella). Haematococcus and Euglena are produced in photobioreactors or hybrid Plant-based food is gaining increased acceptance in parts of the industrialized world. Germany, for example that traditionally consumed rather little vegetables and fruits, has now reached a tipping point where (42%) would say they were deliberately limiting meat consumption while less people said they were comfortable with eating meat (Oltermann 2020). This has a bearing on microalgal production. Since 3 to 4 years, many microalgal R&D projects have started operating within meat replacements and soy protein replacement. Whereas microalgal biofuel production depends on triacylglycerol formation that requires growth limitation, protein formation takes place at fast biomass growth rates and that would unleash the high microalgal productivity potential. Microalgal protein in a multiple product value chain already now appears economically viable (Slegers et al. 2020). Water management Water management is a global issue of ever-increasing importance. In arid regions, producing food at low water consumption is a subsistence condition. In Israel, for example algal cultivation is considered a desert technology. Heat tolerant species (42 degrees) may be cultivated in open ponds during summertime at a water loss of 20 L m-2 day-1 , even in hot desert areas where positive convection (heating) occurred during night (Pruvost et al. 2019). With a modest heat-exchanger in the ground under the ponds, both heat tolerant and temperate species could be cultivated year-round. Cooling with saltwater, either from aquifers or from the sea is another option. In a 1 ha flat panel plant near Livorno, Italy, annual power expenditure for pumping sea water for cooling, was 52 GJ y-1 ha-1. (Tredici et al. 2015) or 14,400 kWhr. This is very little, compared with the energy output of the produced biomass, 799 GJ y-1 ha-1 in the 36 t Tetraselmis. net energy ratio however was still negative, mostly because of a large power consumption for bubbling the cultures (317.1 GJ y-1 ha-1). The Proviron reactor (Fig. 1-5), (Norsker et al. 2019) offers an elegant solution to temperature control in temperate climates where heating is dominated by radiation-the panels are enclosed in a water filled bag which is large enough to absorb heat from a high irradiation (>30 MJ m-2) summer day and dissipate it during night. These examples hold promise-there are technical and economical solutions for maintaining adequate temperature in both open and enclosed microalgal cultures. Land utilization Microalgae may be produced in closed reactors on industrially impacted land that is unsuitable for agricultural crops and such activity is therefore not in competition with conventional agricultural food production. An example is the flat panel photobioreactor plant, that from 2011 to 2017 was integrated in a solid waste disposal plant, Hooghe Maey in Antwerp. The plant was developed by the Belgian chemical company, Proviron. The waste disposal plant contributed hot water and electrical power and CO2 from biogas combustion to the algal plant (Fig. 1-5), (Norsker et al. 2019). Open pond cultivation of algae, on the other hand is sensitive to airborne and water pollution from industrial activities. Productivity of Nannochloropsis oceanica in an industrial closely spaced flat panel photobioreactor Chapter 4
Challenges and Perspectives of Microalgae Production
TATuP - Zeitschrift für Technikfolgenabschätzung in Theorie und Praxis
SCHWERPUNKT Challenges and Perspectives of Microalgae Production Introduction to the Thematic Focus by Christine Rösch, ITAS, and Clemens Posten, BLT (both KIT) Microalgae offer great promise to contribute to the future supply of biofuels, but great efforts in research, development and demonstration are needed to overcome the biological, technical, economic and environmental challenges to developing a sustainable and commercially viable microalgae production system. The thematic focus of this issue highlights the grand challenges, perspectives and milestones of microalgal biomass production. These articles provide an overview of the most important questions addressed by society, and the answers they offer contribute to our conceptual knowledge. They provide a basis on which we can undertake the first steps in assessing any unintended side-effects-a core business of technology assessment. 1 Parameter Open ponds Photobioreactors Land footprint High Low Water footprint High Low CO 2 release High Low Energy requirement Low High Application of waste water Yes Yes Temperature control Not needed Required Reactor cleaning Not needed Required Risk of contamination High Low Product quality Variable Reproducible Microbiology safety No Yes Biomass productivity Low High Capital and operation costs
Modeling and Simulation of the Growth of Microalgae in Photobioreactors
Development of new-source of energy which is renewable and carbon neutral is necessary for mankind’s environmental and economic sustainability. Among the new sources of energy being explored, biodiesel derived from oil crops and from microalgae is the most potential and promising source. However, the production period of oil plants is also one of the primary concerns. More so, meeting the increasing demand of energy from oil plants would require the world to use virtually all of its arable land which also competes with the increasing demand of food supply. Microalgae which is the most potential source of biodiesel overcomes such drawbacks. Microalgae use primary sunlight and CO2 to produce oil. Oil content in microalgae can exceed 80% by weight of dry mass and they can double their biomass within 24 h. Although a number of photobioreactors (PBRs) have been proposed for large scale production of microalgae, only a few can be practically used because of the following factors: most des...
Cultivation Systems of Microalgae for the Production of Biofuels
Biofuels - State of Development
As reported in the study, the high-oil/ha-year productivity of microalgae has raised a lot of interest in their use as a source of raw materials for biofuels. However, the high costs of production and maintenance of closed culture systems (photobioreactor type) and the problems of contamination that lead to lower productivity of open systems (of the "open-pond" type) have become important limitations in evaluating the sustainability of producing biofuels from microalgae.In the view of the favorable prospects of employing microalgae as an economically viable source of raw materials for the production of biofuels, this chapter outlines the different ways microalgae are cultivated, the required nutritional conditions and the main procedures used for increasing their scale. Additionally, those more commonly used on a large scale are described and their advantages and disadvantages are pointed out. This analysis results in a proposal of a new type of photobioreactor, of the cylindrical container type, constructed of polyethylene, a nontransparent material that is cheaper and more durable than the ones that are commonly used (polycarbonate, glass or polymethyl methacrylate (PMMA)). Internal illumination of the photobioreactor is provided by a beam from plastic optical fibers that receive sunlight focused at the extremity of the beam.
Cultivation of Local Fresh Water Microalgae in Closed Systems
Alternative renewable energy is considered the optimal solution to solve the global energy crisis. Biofuel is one of the promising alternatives; especially that are produced from microalgae. Microalgae have the potential to produce 5000 – 15000 gallons biodiesel/ (acre-year). However, there are challenges; these include high yield of biomass and high lipid content. In this paper the authors studied the concentration of inoculum and the light penetration as a part of the parameters affecting the kinetics of the cultivation process of local strains of microalgae (Spirulina platensis, Scenedesmus obliquus, and Nannochloropsis sp.) that isolated from the Nile to obtain the maximum amount of oil, applying the factors affecting algal growth as light intensity, mixing, temperature and aeration for optimal design of photo-bioreactor. The achieved productivity was 0.54 g/l of algae biomass in 13 days with doubling time 2.8 days and specific growth rate 0.25 d-1. Optimizing the culture dense ...
Modified conventional bioreactor for microalgae cultivation
Journal of bioscience and bioengineering, 2017
Microalgae, a renewable source for third generation biofuel production, have a great potential if cultivated in high concentration economically. Bottleneck lies with designing economical and efficient photobioreactor. In addition, proportional C and N inputs in the known media does not support high specific growth rate and high biomass build-up. Nitrates in fermentation media, f/2 for Nannochloropsis sp. and Zarrouk's for Arthrospiraplatensis, were modified. Aeration and agitation were altered in conventional bioreactor (BIOFLO 110) to reduce power consumption, increase mixing time and prevents settling. This was achieved by introducing four way flow regime supporting uniform nutrient and cell distribution in media. Volumetric cell productivity for Nannochloropsis sp. and A. platensis were achieved as 0.618 g/l/d and 0.774 g/l/d, respectively. This photobioreactor also supported the maximum specific CO2 sequestration rates to the level of 0.42 g/g/h and 0.39 g/g/h for Nannochlor...
A new tubular reactor for mass production of microalgae outdoors
Journal of Applied Phycology, 1993
A novel reactor for outdoor production of microalgae is described. Airlift is used for circulation of the culture in transparent tubes lying on the ground and interconnected by a manifold. Dissolved 02 is removed through a gas-separator placed 2.0 m above the tubes and water-spray is used for cooling. The manifold permits short-run durations between leaving the gas separator and re-entering it, preventing thereby damaging accumulation of dissolved oxygen. Day temperature control in summer is attained using water-spray. In winter, temperature in the tubes rises rapidly in the morning, as compared to an open raceway even if placed in a greenhouse. The number of hours along which optimal temperature prevails in the culture throughout the year increased significantly. Very high daily productivity computed on a volumetric basis (e.g. 550 mg dry wt 1-culture) was obtained and preliminary observations indicate that a significantly higher output, e.g. 1500 mg dry wt 1-' d-1, is attainable. Much more research is required to assess the year-round, sustained productivity attainable in this reactor.