Raceway Pond System Research Articles

Cultivation of Chlorella minutissima under a novel phosphate application strategy for biodiesel production: A pilot scale study

Microalgal biodiesel is considered as a carbon-neutral and renewable energy source for replacing/blending with petroleum-based diesel fuel. Selection of a microalgal species for its potential to produce biodiesel relies significantly on its acclimatization to grow in outdoor condition with high lipid productivity. The present investigation undertakes outdoor experiments in a raceway pond system involving a local isolate of green microalga, Chlorella minutissima, throughout varied seasonal changes and culture depth. The variations in climatic and cultural parameters were documented; the optimum culture depth of 30 cm was taken for further investigation. A novel cultivation approach incorporating the sequential addition of low-dose phosphate (LDSPA) projected a lipid productivity of 5.88 ton hectare−1 year−1, which was ∼40% higher than its batch culture counterpart, along with a 14-fold reduction in phosphate application. The biodiesel exhibited the dominance of saturated and monounsaturated fatty acid methyl esters, and the fuel qualities were confirmed to be within the stipulated limitations of European, American and Indian biodiesel standards, thus nominating C. minutissima as an attractive feedstock for generating high-quality biodiesel.

Microalgae Commercialization Using Renewable Lignocellulose Is Economically and Environmentally Viable.

Conventional phototrophic cultivation for microalgae production suffers from low and unstable biomass productivity due to limited and unreliable light transmission outdoors. Alternatively, the use of a renewable lignocellulose-derived carbon source, cellulosic hydrolysate, offers a cost-effective and sustainable pathway to cultivate microalgae heterotrophically with high algal growth rate and terminal density. In this study, we evaluate the feasibility of cellulosic hydrolysate-mediated heterotrophic cultivation (Cel-HC) for microalgae production by performing economic and environmental comparisons with phototrophic cultivation through techno-economic analysis and life cycle assessment. We estimate a minimum selling price (MSP) of 4722 USD/t for producing high-purity microalgae through Cel-HC considering annual biomass productivity of 300 t (dry weight), which is competitive with the conventional phototrophic raceway pond system. Revenues from the lignocellulose-derived co-products, xylose and fulvic acid fertilizer, could further reduce the MSP to 2976 USD/t, highlighting the advantages of simultaneously producing high-value products and biofuels in an integrated biorefinery scheme. Further, Cel-HC exhibits lower environmental impacts, such as cumulative energy demand and greenhouse gas emissions, than phototrophic systems, revealing its potential to reduce the carbon intensity of algae-derived commodities. Our results demonstrate the economic and environmental competitiveness of heterotrophic microalgae production based on renewable bio-feedstock of lignocellulose.

Extraction and partial characterization of exopolysaccharides and pigments from cyanobacterium Oscillatoria pseudogeminata G.Schmid

Cyanobacterial pigments such as chlorophyll, carotenoids and phycobiliproteins are considered as ecofriendly natural colourants used in food and food additives as they have nutraceutical value, non-toxic and non-carcinogenic. The present study focused on extraction, partial characterization of extracellular polysaccharides (EPS), phycocyanin and mycosporin like amino acid (MAA) from a freshwater cyanobacterium Oscillatoria pseudogeminata G.Schmid.The purified isolate of O.pseudogeminatawas deposited and maintained in the NRMC-F, Bharathidasan University. The EPS was extracted withthe help of double volume of ice-cold acetone and confirmed by UV (260 and 280 nm), FTIR and XRD analyses.Phycocyanin and MAA were also extracted from O. pseudogeminata biomass using double distilled water. The UV-VisSpectrophotometric results revealed that 520 and 230 nm peaks represent phycocyanin and MAA, respectively. Further, theprocess of scaling-up the biomass and increase the productivity of EPS, Phycocyanin and MAA from Oscillatoriapseudogeminata is under raceway pond system, already initialed in our laboratory.

Review on the recent structural advances in open and closed systems for carbon capture through algae

Carbon capture has already been at the forefront of fighting global warming and ascending carbon dioxide emissions. To cumulate for a net-zero world by 2050, scientists believe carbon dioxide sequestration to play a consequential role. For achieving this near impossible, technologies ranging from simple chemical absorption and adsorption to novel membrane and biological methods have been studied. This review paper focus tentatively on one of the many carbon capture methods- the biological algal systems. Algae has nearly forty times the photosynthesis rate than normal terrestrial organisms, and a circular bio-economy involving algae lead to diversification of feedstock and raw materials. After a short overview on the requisite for carbon capture and other technologies, the article discuss the general strategies for macroalgae and microalgae mediated systems and their applicability. Recent developments in the open raceway pond systems and the closed photobioreactor systems have been reviewed extensively, and novel strategies have also been focused on. A brief discussion has also been added to understand the relation of carbon capture technologies and their implications on the Energy-Water-Food nexus. The present article also discuss the future roadmap for new research and development works that need to take place and how the integration of certain different subjects can render microalgae as a prosperous commercial feedstock.

Design, Fabrication, and Performance Evaluation of Open Raceway Ponds for the Cultivation of Chlorella vulgaris Beijerinck in the Philippines

Two pilot-scale open raceway pond systems were designed and fabricated in the University of the Philippines Los Baños (UPLB) for the cultivation of Chlorella vulgaris Beijerinck to observe the biomass productivity of the alga in an open condition in the Philippines. One design was an oval track with a middle island, while the other was a multi-stage raceway pond (MSRP) consisted of several sections separated by baffles. The pond designs aimed to accommodate 1,000 L of culture. The nutrient media used was composed of urea, NPK (16-20-0), FeCl3, and Na2EDTA – a locally formulated medium that sustains the growth of the species. Paddlewheel was installed to provide mixing, which was turned on during the daytime, while aeration was continuously supplied through perforated air-distributor PVC pipes installed on the pond floor. Only natural light was utilized, and no lighting was provided during the night. The growth rate was generated by monitoring the biomass concentration in the pond through spectrophotometry at 425 nm, where optical density and biomass concentration relationship was initially established. Using the equation for first-order kinetics and taking the points from the exponential phase, the specific growth rate of Chlorella obtained from the oval raceway pond was computed to be 0.007308 h–1 with doubling time of 94.84 h. The biomass productivity rate was computed to be 308.49 g/m3-d or equivalent to 63.24 g/m2-d. On the other hand, the MSRP obtained a specific growth rate of 0.003389 h–1 with a doubling time of 204.55 h and equivalent biomass productivity of 302.19 g/m3-d or 60.44 g/m2-d. The biomass productivity obtained is comparable, even superior to other commercial open pond cultivation using C. vulgaris.

Simulation and analysis of open raceway pond system at Manit, Bhopal

Microalgae can become completely faster than terrestrial plants and are a successful feedstock for viable appreciation including items that envelop pharmaceuticals, neutraceuticals, proteins and most significantly biofuels. Since the biomass productivity of microalgae absolutely depends emphatically on the temperature of development, point-by-point data on the temperature of the reactor as a component of time and topographic area is essential to assess the sincere capability of microalgae as a traditional feedstock. Microalgae is indeed a promising source of renewable biofuels, and techno-financial upgrades can be made by improving and controlling the stage of biomass development. This research explores the improved performance of a first-standard green growth development display that encompasses the effect of regular (and such) notions of climate in an open system related to creation. Thus, the simulation of the procedure is stochastic just as basic; it helps restore the dissemination of outcomes from normal changeability that speak to the daily acknowledgement. It also communicates variety day-to-night in the vitality based on cycling sunlight. The simulation is then used to optimize the design of the pond and the manages (growth time, depth of the raceway, pH control, etc.) to enhance protability. Because the simulation is stochastic, nonlinear, and with different optima, an optimization method for multiplayer direct inquiry is used with relentless state assembly criteria. Conclusions are that (1) representing common variety in optimization prompts detectable protability improvement, (2) model impact investigation uncovers where key science exploration is expected to support basic techno-monetary wonders, and (3) the stochastic optimization approach is broadly relevant.

A comparative life cycle assessment of microalgae production by CO2 sequestration from flue gas in outdoor raceway ponds under batch and semi-continuous regime

To be a sustainable energy source, a microalgal cultivation model should address important environmental challenges for its large-scale implementation. In this work, the performance of an outdoor raceway pond system was evaluated for biomass production and sequestration of flue gas carbon-dioxide under different conditions. The microalgae growth was influenced by several physio-chemical factors such as temperature, solar irradiance, carbon-dioxide in the incoming feed, cross-contamination etc. Batch microalgal cultivation, without any external carbon supplementation (0.04% CO2, v/v), exhibited lower areal biomass productivity, whereas flue gas (10 ± 2% CO2, v/v) feeding increased dissolved medium carbon concentrations, which improved carbon-dioxide fixation rate. To further improve the system’s performance, semi-continuous regime was adopted that resulted in maximum biomass density of 0.42 g/L and 3.5-fold increase in areal productivity of 11.488 g/m2.s. Next, a “cradle-to-gate” Life Cycle Assessment (LCA) was performed using SimaPro 8.3.0.14 software to identify the potential environmental impacts associated with the production of Chlorella vulgaris biomass (functional unit: 1 kg). Results showed cultivation step to have significant environmental impact (>75%) in terms of GHG emission, energy requirement and other impact categories as estimated by GWP 100 IPCC 2013, CED and ReCiPe Endpoint method. Further, sensitivity analysis assisted in identifying the effect of variables with greatest impact on systems performance in the proposed scenarios; especially with the co-location of cultivation systems and flue gas emitting point sources. The results of attributional LCA revealed that flue gas utilization by microalgae in outdoor raceway ponds has less carbon footprint when a semi-continuous cultivation is carried out and will be more suitable when raceway ponds are co-located with thermal power plants.

Algae Harvesting from Large Outdoor Ponds Using a Novel Parallel Robot System

This paper presents a novel method for effective, economical, energy-efficient algae harvesting from large (1-4 acre) outdoor circulating raceway pond systems: a portable 4-cable-suspended robot. Algae, used as an alternative energy crop to produce biofuels (and other consumer products), still remains too expensive. One of the greatest expenses in processing algae is the harvesting process. To replace the typical energy-intensive pumping of the entire pond water through algae filters, we propose using a cable-suspended robot to collect algae, which largely then drains of water while the robot translates the product to a collection point. An additional benefit of our concept, in additional to lower harvesting cost, is that the algae still growing in the pond is not shocked as in the current pumping process, leading to better, healthier yields. Further, the proposed robot system is portable, capable of harvesting multiple ponds while algae continues to grow.

Unveiling algal cultivation using raceway ponds for biodiesel production and its quality assessment

Abstract Microalgal biomass is a renewable, carbon-neutral resource and an excellent alternative to petroleum-footed fuels. In this work the open outdoor raceway pond system was used for the cultivation of Chlorella vulgaris. The biomass productivity was 31.5 mg L-1d-1 and lipid content 25 ± 5% when cultivated in low cost medium (Urea, Superphosphate and Potash at 91.9, 72.9 and 62.7 mg L-1 where the pH was 8.03) formulated by RSM. The highest FAME yield was 67% under the optimized conditions of H2SO4 at 4%; reaction time at 4 h; methanol-hexane as co-solvent in the ratio of 2:1; and temperature at 80 °C for 100 mg of algal lipid. The DU, LCSF, CFPP, CN, PP, CP of the biodiesel evidenced high quality, which corroborate with International standards. The diesel engine performance showed a blend of B50 which is superior in quality compared to B20 and B40 blends and the commercial diesel. Furthermore, reduction of brake-specific fuel consumption at 100% load showed 273.9 g/kW h in B50 whereas for commercial diesel it was 275 g/kW h. There was 40–55% reduction of CO, HC, and emissions compared to commercial diesel. Thus, this research emphasizes that microalga-based biodiesel is cost-effective and eco-friendly choice for biodiesel.

The color of mass culture: spectral characteristics of a shallow water column through shade-limited algal growth dynamics(1).

It is envisioned that mass algal cultivation for commercial biofuels production will entail the use of large raceway pond systems, which typically have shade-limited photosynthetic growth within depths of 20-30cm. The attenuation of light and spectral qualities of red, green, and blue wavelengths in a 20-cm water column as a function of Chl-a concentration during exponential and linear phases of growth dynamics for the marine diatom Thalassiosira pseudonana was examined under laboratory conditions. While photosynthetically available radiation (PAR) was in excess throughout the water column during the phase of exponential growth, PAR became rate limiting differently for red, green, and blue wavelengths during the phase of linear growth. The transition from exponential to linear growth occurred at 1-2mg Chl-a·L-1, whereby a scalar ~5μmol photons·m-2·s-1 at 20-cm depth was found to occur as would be anticipated having the compensation point for where rates of photosynthesis and respiration are equal. During the phase of linear growth, red wavelengths became increasingly dominant at depth as Chl-a concentrations increased, being contrary to the optical conditions for those natural bodies of water that forced the evolution of phytoplankton photosynthesis. It is hypothesized this dramatic difference in water column optics between natural and synthetic environments could influence a variety of biological reactions, importantly non-photochemical quenching capacities, which could negatively impact crop yield.

Dimensionless equations to describe microalgal growth in a planar cultivation system.

To develop dimensionless equations to describe microalgal growth in planar photobioreactor or raceway pond systems that are generalized to all phototrophic species and reactor length scales. Expressions for biomass growth and mean light intensity within a nutrient replete, well-mixed, phototrophic cell culture in a planar cultivation system were developed in terms of dimensionless variables for biomass, time and light intensity, plus two new dimensionless parameters. The first dimensionless parameter represents a species-specific physiological characteristic based on maximum growth rate and cell maintenance, while the second represents the light input. Optimal biomass productivities and photosynthetic conversion efficiencies are easily determined from the dimensionless expressions and system-specific performances can be easily determined by back substituting with the relevant cell culture and photobioreactor parameters. The dimensionless expressions are useful for understanding and determining the relevant bioprocess parameters in a generalized form applicable to all strains and reactor length scales.

Comparison of continuous and day time only mixing on Tetraselmis suecica (Chlorophyta) in outdoor raceway ponds

The mixing of microalgae bioreactors is important as it circulates cells in and out of the light zone and reduces boundary layers, benefiting photosynthesis and nutrient uptake. However, mixing is also a major economical factor, impacting on power consumption and operating costs, and it remains a barrier for those locations where no electrical supply is available. Combining solar panels with algae ponds can help to alleviate the power cost burden, but if solar panels are the sole source of generated electricity for a regional raceway pond system, the paddle wheels will only operate during day time. This study investigated the growth of halophilic green alga Tetraselmis suecica, in outdoor paddle wheel-driven open ponds under three different mixing regimes. The first experimental condition was a continuously mixed regime, while in the second and third conditions, the paddle wheels were stopped overnight and restarted 1 h after sunrise or 1 h before sunrise, respectively. Growth rate, biomass productivity and cell weight showed no statistically significant difference during the period when the culture was growing under optimal environmental conditions. Chlorophyll fluorescence measurements of photosystem II maximum quantum yield in the light (Fv′/Fm′) over a 24-h period found no significant differences between cultures, further suggesting that under favourable conditions ceasing mixing overnight may have no undesirable impact on Tetraselmis health or productivity. These findings imply a potential 37 % power saving and a 33 % reduction in energy-associated costs. During a heat stress event, Tetraselmis was negatively impacted in all ponds to the same degree; however, the continuously mixed pond recovered faster than ponds that were not mixed overnight.