Raceway Reactor Research Articles

Microalgae from Biorefinery as Potential Protein Source for Siberian Sturgeon (A. baerii) Aquafeed

The demand for aquafeed is expected to increase in the coming years and new ingredients will be needed to compensate for the low fish meal and oil availability. Microalgae represent a promising matrix for the future aquafeed formulation, however, the high production cost hinders its application. The use of microalgae from biorefinery would reduce the disposal costs for microalgae production. The present study aimed to (i) verify the growth of microalgae on digestate coming from pig farming and (ii) evaluate their potential valorization as dietary ingredient in aquafeed according to a Circular Bioeconomy approach. For these purposes, a microalgae biomass was produced on an outdoor raceway reactor supplied with digestate and used for partial replacement (10% of the diet) in aquafeed for Siberian sturgeon fingerlings (Acipenser baerii). The results obtained confirm the feasibility for growing microalgae on digestate with satisfactory productivity (6.2 gDM m−2 d−1), nutrient removal efficiency and Chemical Oxygen Demand reduction; moreover, the feeding trial carried out showed similar results between experimental and control groups (p > 0.05), in term of growth performance, somatic indices, fillet nutritional composition and intestinal functionality, to indicate that microalgae from biorefinery could be used as protein source in Siberian sturgeon aquafeed.

Semi-continuous removal of nutrients and biomass production from domestic wastewater in raceway reactors using Chlorella variabilis TH03-bacteria consortia

Abstract Production of algae biomass from wastewaters have been considered as an economical strategy for feasible commercialization of microalgae industry. Technically, large scale cultivation of microalgae in wastewaters should be conducted in semi-continuous and/or continuous modes, in which stable health of algal cultures of previous generations for the use of later generations needs to be ensured. In this regards, this study has investigated stability of growth and pollutant removal capability of Chlorella variabilis TH03-bacteria consortia using domestic wastewater as the sole of nutrient source in raceway ponds. Experiments were performed in semi-continuous mode with the aim of recovering valuable nutrients including carbon, nitrogen and phosphorous from the waste stream to algal biomass. Data revealed that prior domestication of C. variabilis TH03 in unsterilized domestic wastewaters established seed cultures of C. variabilis TH03–bacteria consortia, which enabled to grow effectively in new wastewaters under highly variable conditions. Moreover, once nutrient levels dropped below those required by the national technical regulation on domestic wastewater QCVN 14 : 2008/BTNMT, the replacement of 80% volume of the algal–bacteria culture with new wastewater media was recommended to ensure both culture stability as well as high pollutant treatment capacity of the raceway systems. Under the optimal replacement, biomass concentration and areal biomass productivity of 1.67–1.85 g/L and 11.1–15.3 g/m2 day, respectively, were steadily achieved over 148 days of the outdoor cultivations. Removal efficiencies of nutrients in the form of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorous (TP) removed by the C. variabilis TH03-bacteria consortia in the reactor systems were determined as 64.7–90.7, 85.1–96.8 and 99.7%–100%, respectively. The obtained results are useful for further optimization including design and manage C. variabilis TH03-bacteria consortia based continuous processes in larger scales for the production of high volume and low price biomass, helping to obtain returns from treatment of the waste stream, which is currently considered as a major source of water pollution in Vietnam.

Scale-up of a Fibonacci-Type Photobioreactor for the Production of Dunaliella salina.

In this work, the previously proposed Fibonacci-type photobioreactor is scaled up and evaluated to produce Dunaliella salina. First, the composition of the culture medium was optimized to achieve maximal productivity. Next, the Fibonacci-type reactor was scaled up to 1250 L maintaining high solar radiation interception capacity of this type of reactor. Finally, the performance of the reactor for the production of green cells of Dunaliella salina at the environmental conditions prevailing in the Atacama Desert was evaluated. Data demonstrated that the proposed photobioreactor allows the temperature, pH and dissolved oxygen concentration to be maintained within the optimal ranges recommended for the selected strain. Both better exposure to solar radiation and photonic flow dilution avoids the use of cooling systems to prevent overheating under outdoor conditions. The system allows up to 60% more solar radiation to be intercepted than does the horizontal surface, likewise, allowing to maintain the pH efficiently through CO2 injection and to keep the dissolved oxygen concentration in acceptable ranges, thanks to its adequate mass transfer capacity. The biomass concentration reached up to 0.96 g L-1, three times higher than that obtained in a raceway reactor under the same environmental conditions, whereas productivity was up to 0.12 g L-1 day (2.41 g m-2 day). Maximum specific outdoor growth rates reached up to 0.17 day-1. Undoubtedly, this technology scaled up constitutes a new type of photobioreactor for use at the industrial scale since it is capable of maximizing biomass productivity under high light conditions.

Diurnal and nocturnal pH control in microalgae raceway reactors by combining classical and event-based control approaches.

The pH control in raceway reactors is crucial for an optimal performance of the system. Classical pH control is exclusively performed during the daytime period for cost saving reasons. This paper demonstrates that pH can be controlled 24 hours a day by using both a continuous-based and an event-based control approach, being able to improve the system's performance and reducing costs at the same time. Thus, experimental tests on a raceway reactor for several days are presented to show a comparison between traditional control algorithms during the daytime period versus an event-based control approach operating during both daytime and night-time periods. As a result, the combination of classical PI control for the daytime period and the event-based control for the night-time period is presented as a promising pH control architecture in raceway reactors.

Outdoor pilot-scale raceway as a microalgae-bacteria sidestream treatment in a WWTP

This study aims at demonstrating the feasibility of using microalgae-bacteria consortia for the treatment of the sidestream flow of the supernatant from blackwater dewatering (centrate) in an urban wastewater treatment plant in Northern Italy. A 1200 L raceway reactor was used for the outdoor cultivation of a diverse community of Chlorella spp., Scenedesmus spp. and Chlamydomonas spp. in continuous operation mode with 10 days hydraulic retention time. During the trial, an average daily areal productivity of 5.5 ± 7.4 g TSS m−2 day−1 was achieved while average nutrient removal efficiencies were 86% ± 7% and 71% ± 10% for NH4-N and PO4-P, respectively. The microalgal nitrogen assimilation accounted for 10% of the nitrogen in the centrate while 34% was oxidized to nitrite and nitrate. The oxygen produced by microalgae fully covert the oxygen demand for nitrification. This suggests that the proposed process would reduce the aeration demand for nitrification in the water line of the plant, while producing algal biomass to be further valorized for energy or material recovery.

Assessing Oil Content of Microalgae Grown in Industrial Energetic-Laden Wastewater

Industrial ammunition facilities generate wastewater containing different energetic compounds and nitrogen species. Our previous studies showed that some of these untreated wastewater streams can be mixed at a specific ratio to grow microalgae. In this study, four different untreated wastewater samples from an industrial ammunition facility were mixed and used as a culture media for microalgae, Scenedesmus obliquus ATCC®11477, in 100 L raceway reactors. The main objective of the study was to test the effect of growth parameters (light penetration, nutrient availability and retention times) on the oil content of microalgae in a semi-continuous setting. The raceway reactors were operated under 68–95 μmol/m2/s of light intensity for a 14:10 h light:dark photoperiod, and 60 rpm mixing paddle speed. Continuous monitoring of pH and temperature of the growth medium, periodic analysis of cell density and dry weight of microalgae, and analysis of the medium’s nutrient contents were performed. Biomass harvesting from the raceway reactors was conducted weekly, and the harvested algal biomass was tested for its oil content using an ethanol extraction method. Results showed that nitrogen starvation increased the oil production from 13% to 29% of oil based on the dry weight of biomass, whereas no increment in oil or biomass production was evidenced with the increase of light penetration for the two different retention times tested. This study provided significant information towards microalgae growth in energetic-laden wastewater streams. This study also showed that wastewaters from industrial ammunition facilities can be reused for culturing microalgae, which can be utilized for renewable energy production.

Treatment of a synthetic colored effluent in raceway reactors: The role of operational conditions on the environmental performance of a photo-Fenton process

This study assessed the environmental and economic performance of a photo-Fenton process in a raceway reactor at laboratory scale. For the best operational condition (BOC) identified (dye = 55.0 mg/L, H2O2/dye = 0.862 mg/L, Fe2+/dye = 0.184) a carbon footprint (CFP) of 1.335 kg CO2 Eqv/m3 was obtained. Consumption of electrical energy, construction materials, and reagents represent 97.2% (1.298 kg CO2 Eqv/m3) of the CFP. Similarly, ReCiPe-2016 v1.1 evidenced that these activities play an important role on the environmental performance of the process because their relative impact ranged from 96.5% to 99.7% at least in 14 of the 18 categories considered by this method. It should be noted that the CFP is scarcely sensitive to variations in the use of cement, steel, H2O2, and NaOH as a 50.0% increase in their expenditure increases the CFP in 4.4%, 5.0%, 5.9%, and 7.2%, respectively. A 50.0% increment in electricity consumption increased the CFP in 20.7% whereas categories related to acidification, eutrophication, resources depletion, and toxicity-related impacts had significant increments (20.0%–34.0%) in the emissions of substances used for impact characterization. BOC led to the lowest treatment cost (US$0.540/m3) and a CFP between 5- and 10-times lower than that reported for solar tubular reactors. Also, higher proportions of H2O2 (H2O2/dye = 1.200–1.800) and Fe2+ (Fe2+/dye = 0.200–0.300) increased cost in 1.9%–5.6% but reduced the CFP in 1.2%–3.7%. Finally, our results evidenced that it is possible to increase the raceway reactor's capacity by increasing the depth of the reactor without affecting the effluent quality. When the depth of the reaction medium went from 3 cm to 6 cm, the treatment capacity (TC) was increased 102.4%, and a 33.3% diminution in the CFP and of 29.1% in the treatment cost occurred. An increase from 3 cm to 9 cm rose the TC up to 204.4% and reduced the CFP (44.4%) and treatment cost (39.3%).

Daytime/Nighttime Event-Based PI Control for the pH of a Microalgae Raceway Reactor

In this paper, a new solution to improve the traditional control operation of raceway microalgae reactors is presented. The control strategy is based on an event-based method that can be easily coupled to a classical time-driven proportional-integral controller, simplifying the design process approach. The results of a standard Proportional-Integral (PI) controller, as well as of two event-based architectures, are presented in simulation and compared with each other and with traditional On/Off control. It is demonstrated that the event-based PI controller—operating during the whole day instead of only during daytime—achieves a better performance by reducing the actuator effort and saving costs related to gas consumption.

Evaluation of photosynthetic light integration by microalgae in a pilot-scale raceway reactor

The improvement of photosynthetic efficiency in a 100 m2 raceway reactor by enhancement of light regime to which the cells are exposed is here reported. From Computational Fluid Dynamics it was calculated that the light exposure times ranged from 0.4 to 3.6 s while the exposure times to darkness were much longer, from 6 to 21 s. It was demonstrated that these times are too long for light integration, the cells fully adapting to local irradiances. This phenomenon was validated in the real outdoor raceway at different seasons. Simulations allows to confirm that if total light integration is achieved biomass productivity can increase up to 40 g/m2·day compared to 29 g/m2·day obtained considering local adaptation, which is close to the experimental value of 25 g/m2·day. This paper provides clear evidence of microalgae cell adaptation to local irradiance because of the unfavourable cell movement pattern in raceway reactors.

Combination of solar disinfection (SODIS) with H2O2 for enhanced disinfection of marine aquaculture effluents

Technologically advanced recirculation aquaculture systems (RAS), developed for intensive farming, allows to recycle about 90–99% of water. As a result, accumulation of pathogenic bacteria in water often occurs and possesses threat of infectious fish diseases. The goal of this study was to evaluate feasibility of solar disinfection in combination with hydrogen peroxide for seawater and real marine aquaculture effluent. Specific roles of solar disinfection (SODIS), hydrogen peroxide and highly reactive oxidizing species (experiments conducted in presence of tert-butyl alcohol), generated in combined SODIS/H2O2 process were investigated. Natural consortia of Vibrio spp., known as highly resistant pathogen, present in seawater and real marine aquaculture effluent were chosen as target microorganisms. The SODIS/H2O2 process significantly enhances inactivation of natural Vibrio consortia (Vibrio harveyi, Vibrio owensii and Vibrio alfacsensis) in seawater in comparison with individual SODIS and H2O2 treatment. The best results in terms of Vibrio spp. inactivation efficiency was obtained with SODIS/H2O2 conducted using open channel raceway reactor. The efficiency of Vibrio spp. inactivation by SODIS/H2O2 in raceway and compound parabolic collector (CPC) reactors was found to be similar, requiring the dose of 28–29 Wh m−2 for complete inactivation of Vibrio spp. present in seawater. Absence of toxic effect of residual H2O2 for Nannochloropsis gaditana, as well as absence of Vibrio spp. regrowth (48 h) indicate suitability of SODIS/H2O2 process for inactivation of pathogenic bacteria in aquaculture effluent and following nutrients removal by microalgae. Moreover, feasibility of SODIS/H2O2 performed in raceway reactor for disinfection of real aquaculture effluent, containing more than 5⋅103 CFU mL−1 of Vibrio harveyi, was demonstrated requiring the dose of 34.4 Wh m−2 for complete Vibrio spp. inactivation. The annual operation and maintenance cost of aquaculture effluent disinfection using CPC and raceway reactors were evaluated.

Analysis of mass transfer capacity in raceway reactors

In the present work, a methodology is proposed to determine the mass transfer capacity in existing microalgae raceway reactors to minimize excessive dissolved oxygen accumulation that would otherwise reduce biomass productivity. The methodology has been validated using a 100 m2 raceway reactor operated in semi-continuous mode. The relevance of each raceway reactor section was evaluated as well as the oxygen transfer capacity in the sump to different air flow rates. The results confirm that dissolved oxygen accumulates in raceway reactors if no appropriate mass transfer systems are provided. Therefore, mass transfer in the sump is the main contributor to oxygen removal in these systems. The variation in the volumetric mass transfer coefficient in the sump as a function of the gas flow rate, and therefore the superficial gas velocity in the sump, has been studied and modelled. Moreover, the developed model has been used to estimate the mass transfer requirements in the sump as a function of the target dissolved oxygen concentration and the oxygen production rate. The proposed methodology allows us to determine and optimize the mass transfer capacity in the sump for any existing raceway reactor. Moreover, it is a powerful tool for the optimization of existing reactors as well as for the design optimization of new reactors.

Photo-Fenton processes in raceway reactors: Technical, economic, and environmental implications during treatment of colored wastewaters

Abstract Photo-Fenton processes in CPC (compound parabolic concentrators)-type solar reactors have received great attention because of their extraordinary performance during the treatment of a wide range of recalcitrant pollutants. Unfortunately, less effort has been spent on evaluating the technical and operational feasibility of more simple and low-cost solar reactors. In this study, we evidenced the technical, economic, and environmental feasibility of a raceway reactor to treat acid orange 52 dye (AO52), by means of a photo-Fenton process. The raceway reactor presents decolorization efficiencies (97%), chemical oxygen demand reduction (COD = 55%), and organic carbon removal (35%) similar to those obtained by compound parabolic collectors. After 1 h of reaction (25 kJ/L of accumulated energy), the treatment allows generating a highly biodegradable (BOD5/COD > 0.5) effluent using 15% of the theoretically required hydrogen peroxide (0.65 mg H2O2/mg AO52) to mineralize the dye. Phytotoxicity assays confirmed the quality of the effluent because photo-treatment led to an increase in the germination index in Cucumis sativus (from 102% to 104%), Solanum lycopersicum (from 37% to 60%), Allium cepa (from 40% to 80%), and Capsicum annuum (from 40% to 90%). During the photo-treatment, an increase of the accumulated energy, from 17 to 32 kJ/L, did not affect decolorization efficiency or the biodegradability of the effluent (BOD5/COD = 0.55–0.69). The lack of solar radiation caused a slight reduction in decolorization efficiency (∼1%) and led to a less biodegradable effluent (BOD5/COD = 0.35); these results suggest that the discharge of the effluent to conventional wastewater plants may affect their robustness. The economic study indicates that it is feasible to biocompatibilize the AO52 dye through a photo-Fenton process in a raceway-type reactor at a low cost (US$1.0/m3). Finally, the life cycle impact assessment reveals that electricity and H2O2 consumption can be considered the main environmental hotspots of the process because they have, in terms of relative impact, a contribution greater than 70% in 14 of the 18 environmental categories considered. Photo-Fenton processes in raceway reactors offer key advantages such as low installation and operating cost, robustness, and a lower environmental footprint (0.762 kg CO2-Eqv/m3 wastewater). Therefore, raceway reactors could become an attractive option for small and medium scale textile mills in low-income economies.

Application of Predictive Feedforward Compensator to Microalgae Production in a Raceway Reactor: A Simulation Study

In this work, the evaluation of a predictive feedforward compensator is provided in order to highlight its most important advantages and drawbacks. The analyzed technique has been applied to microalgae production process in a raceway photobioreactor. The evaluation of the analyzed disturbance rejection schemes were performed through simulation, considering a nonlinear process model, whereas all controllers were designed using linear model approximations resulting in a realistic evaluation scenario. The predictive feedforward disturbance compensator was coupled with two feedback control techniques, PID (Proportional-Integral-Derivative) and MPC (Model Predictive Control) that are widely used in industrial practice. Moreover, the classical feedforward approach has been used for the purpose of comparison. The performance of the tested technique is evaluated with different indexes that include control performance measurements as well as biomass production performance. The application of the analyzed compensator to microalgae production process allows us to improve the average photosynthesis rate about 6% simultaneously reducing the energy usage about 4%.

Experimental Investigation on the Integration of Raceway Pond and Airlift Pump for Microalgal Cultivation

This work proposed an integration of raceway pond and airlift pump (RWPAP) for microalgae cultivation. Therefore, the proposed reactor was evaluated under various configurations of liquid depth in the raceway reactor, air flow rates, two riser airlift pump diameter and two nozzle hole diameter. The minimum air flow rate necessary for circulating medium in the RWPAP reactor in addition to the liquid velocity in the reactor was investigated. These parameters as well as the power consumption were determined in order to achieve the maximum efficiency and effectiveness configuration. The maximum effectiveness configuration of the RWPAP system was achieved at the water depth 40 cm, air flow rate 0.83 L min -1 , injector hole diameter 0.5 mm and tube diameter 0.75 inch that produced the maximum ratio velocity to power consumption with near one tenth of power consumption of the maximum efficiency configuration. At these configurations, the microalga Dunaliella Salina was cultivated in the natural culture medium from the Maharlu Salt Lake, southeast of Shiraz, Iran in order to achieve commercialization and reduce cultivation cost and the results showed that the effectiveness configuration had better biomass productivity, CO 2 utilization efficiency, power consumption and water evaporation rate compared to another configuration. The effectiveness configurations gave comparable batch biomass productivity (0.096 g L -1 day -1 ) and 25.37% CO 2 utilization efficiency, but around five-times higher biomass productivity per unit power input (2.21 g W -1 day -1 ) than reported for the modified airlift reactors. Furthermore, the β-carotene content and composition of fatty acids were evaluated.

Improving the CO2 fixation rate by increasing flow rate of the flue gas from microalgae in a raceway pond

Residence time of flue gas bubbles with different solution velocities and the influence of NO X and SO2 from flue gas on pH values of culture solutions were analyzed based on large-scale raceway reactors. Microalgal growth and CO2 fixation rates were also investigated with different gas flow rates. Bubble residence time was ∼1.1 s when the solution velocity was 20 cm/s. The NO X and SO2 effects on microalgal growth were negligible, although 66% NO X and 95% SO2 were captured by the microalgal solution. Microalgal biomass productivity increased from 10.3 to 14.1 g/m2/d when flue gas flow rate increased from 20 to 50 m3/h. CO2 fixation and microalgae biomass productivity increased further from 26.3 to 31.9 g/m2/d and from 14.1 to 17.1 g/m2/d, respectively, upon increase of flue gas flow rate from 50 to 150 m3/h.

Maximizing CO2 biofixation and lipid productivity of oleaginous microalga Graesiella sp. WBG­1 via CO2-regulated pH in indoor and outdoor open reactors

Carbon dioxide (CO2) and pH are two interdependent factors that greatly impact the growth and lipid accumulation of microalgae. However, the effects of these two factors are usually studied separately. The use of exogenous CO2, such as flue gas derived, to regulate pH in the large-scale cultivation of microalgae provides an ideal means for combining CO2 biofixation and biodiesel production. In this study, the CO2 biofixation and lipid production of oleaginous microalga Graesiella sp. WBG­1 was explored for four pH levels regulated by exogenous 15% CO2 (flue gas concentration) in 10L circular culture ponds and 5m2 open raceway reactors. Results revealed that pH8.0–9.0 was the optimum pH for CO2 fixation and lipid production, attaining the highest CO2 fixation rates of 0.26gL−1day−1 and 18.9gm−2day−1, respectively, lipid contents of 46.28% and 32.38%, and lipid productivities of 64.8mgL−1day−1 and 3.14gm−2day−1. A positive correlation between CO2 utilization efficiency and pH in open reactors was also suggested in this research, and thus provides direction for screening of CO2 fixation by microalgae. The present study provides an excellent strategy for coupling CO2 fixation and lipid production via microalgae in large-scale cultivation.

Dynamic model of an industrial raceway reactor for microalgae production

A dynamic model for microalgae production in raceway reactors is developed in this work. The model takes into account fluid-dynamic, mass transfer, and biological phenomena taking place in microalgae bioreactors. The model has been calibrated and validated using real data from a 100m2 pilot-scale raceway reactor. Results demonstrate that in raceway reactors large accumulation of oxygen takes place into the channel whereas carbon losses into this section are scarce, these phenomena influencing the overall productivity of the reactor. The model can be used to determine characteristic parameters (biological and engineering ones) of existing reactors. Moreover, it can be used to simulate the effect of different designs and/or operation conditions into the performance of the system. Simulations allow us demonstrating that to increase the productivity of raceway reactors it is recommendable to reduce the water depth into the cultures and to increase the mass transfer capacity of the entire reactor.

Optimization of carbon dioxide supply in raceway reactors: Influence of carbon dioxide molar fraction and gas flow rate

Influence of CO2 composition and gas flow rate to control pH in a pilot-scale raceway producing Scenedesmus sp. was studied. Light and temperature determined the biomass productivity whereas neither the CO2 molar fraction nor the gas flow rate used influenced it; because pH was always controlled and carbon limitation did not take place. The CO2 molar fraction and the gas flow rate influenced carbon loss in the system. At low CO2 molar fraction (2–6%) or gas flow rate (75–100l·min−1) the carbon efficiency in the sump was higher than 95%, 85% of the injected carbon being transformed into biomass. Conversely, at high CO2 molar fraction (14%) or gas flow rate (150l·min−1) the carbon efficiency in the sump was lower than 67%, 32% of the carbon being fixed as biomass. Analysis here reported allows the pH control to be optimized and production costs to be reduced by optimizing CO2 efficiency.

Event-based selective control strategy for raceway reactor: A simulation study

This work presents a simulation study of an event-based selective control strategy for a raceway reactor. The control system aims are to maintain simultaneously a pH and dissolved oxygen within specific limits. In the analyzed control scheme, the pH value is prioritized over the dissolved oxygen, since it has a critical influence on the process performance. Besides, the dissolved oxygen also influences the photosynthesis rate and should be kept within the limits. The control structure is evaluated through simulation, where a nonlinear model for microalgae culture in the raceway photobioreactor is used. Analysis of different configurations allows to determine the most adequate control system setup to achieve the desired goals. The obtained results show that combination of an event-based approach with selective control allows to increase the overall productivity as well as to address effective CO2 utilization and aeration system energy minimization.

Outdoor production of Scenedesmus sp. in thin-layer and raceway reactors using centrate from anaerobic digestion as the sole nutrient source

In this paper, we have studied the outdoor production of the freshwater microalgae Scenedesmus sp. in two open reactors (32m2): thin-layer (1.2m3) and raceway (4.4m3), using centrate from anaerobic digestion as the sole nutrient source. The aim was to recover valuable nutrients (nitrogen and phosphorus) from effluents in order to maximize biomass productivity. Experiments were performed in semicontinuous mode, modifying the centrate percentage within the culture medium. The optimal centrate percentage was 30% — above this value the culture's performance reduced, probably due to ammonium excess (above 122mgl−1). Using the raceway reactor, biomass productivity was 24gm−2day−1, whereas using the thin-layer reactor, it increased up to 42gm−2day−1. Nitrogen and phosphorus removal was demonstrated to be proportional to biomass productivity, with maximal values up to 38mgNl−1day−1 and 3.9mgPl−1day−1 being removed, respectively. Ammonium stripping was only relevant in the raceway reactor, due to its lower biomass productivity, with more than 40% of the inlet nitrogen being lost to the air. The thin-layer reactor also proved to be more photosynthetically efficient, with maximal values of 4.7% being measured. An economic analysis demonstrated that the thin-layer reactor allowed a reduction in the biomass production cost, in addition to utilizing waste as the nutrient source, with a minimum production cost of 0.9€/kgbiomass being estimated. In conclusion, it is possible to use centrate from anaerobic digestion as the sole nutrient source for the large-scale production of Scenedesmus sp. biomass thus reducing the biomass production cost by avoiding the use of expensive and non-sustainable fertilizers; while also obtaining returns from the treatment of this type of residue. Such a combination helps to increase the possibility of producing commodities, or biofuels, from microalgae by coupling their production to treatment processes.