Experimental analysis and novel modeling of semi-batch photobioreactors operated with Chlorella vulgaris and fed with 100% (v/v) CO2 (original) (raw)
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Mathematical modelling of chlorella vulgaris growth in semi-batch photobioreactors fed with pure CO2
2013
In order to viably scale up the microalgae based technology for CO 2 capture and biofuels production, suitable mathematical models should be developed. In particular, since the potential exploitation of flue gases as carbon source is one of the main targets of this technology, the effects on microalgae growth, i.e. low pH values and high dissolved concentration of CO 2 , resulting from such operating mode should be properly simulated. Along these lines, a novel mathematical model of the growth of Chlorella Vulgaris in semi-batch photobioreactors fed with pure CO 2 (100% v/v) is addressed in this work.
Algal Research, 2018
A simple and robust microalgae kinetic model has been developed for application in the prediction and control of algae cultivations in wastewater. The microalgae kinetic model was calibrated using experimental cultivation data from Desmodesmus sp. to determine specific microalgae growth rates (μ max and μ maxNO3), microalgae death rates (μ d), and the NH 4 + to NO 3 − oxidation rate (μ B). Model parameters obtained were: μ max = 0.17 day −1 , μ d = 0.004 day −1 , and μ B = 0.14 day −1. Microalgae specific growth rate based on NO 3 − alone (μ maxNO3 = 0.1 day −1) was lower than the overall growth rate (μ max). The kinetic model was validated using additional experimental data for the Desmodesmus sp. and Scenedesmus obliquus cultivation in wastewater containing 0% and 7% landfill leachate, with accuracy above 98% in all cases. These results demonstrated the kinetic model was accurate in predicting microalgae growth, wastewater nutrient removal, and changes in the culture media pH. Biomass productivity of the algae culture was associated with an exponential increase in the media pH, which led to ammonia volatilisation and decreased carbon intake. Between 28.8 and 29.7% of the initial NH 4 + was lost to ammonia volatilisation in wastewater containing 7% landfill leachate. Hence, loss of ammonium nitrogen contained in domestic wastewater must be avoided to ensure steady and efficient inorganic carbon utilisation which inherently maximises biomass production efficiency. The optimal pH for the microalgae culture was 8.1, at which point microalgae could achieve about 99% carbon fixation efficiency. To ensure constant pH in the microalgae growing system, immediate removal of the OH − generated is needed, which could be facilitated by injections of 1.14 g CO 2 and 0.067 g OH − per gram of produced algae when using NH 4 + nutrient, and 1.54 g of CO 2 per gram of produced algae when using NO 3 − nutrient. This could be done in a wastewater pond by using an optical density-controlled smart CO 2 injection system.
New mechanistic model to simulate microalgae growth
Algal Research, 2015
The prospect of treating wastewater and at the same time producing microalgae biomass is receiving increasing attention. Mechanistic models for microalgae growth in wastewater are currently being developed for new systems design as well as to improve the understanding of the involved biokinetic processes. However, mathematical models able to describe the complexity of microalgal cultures are still not a common practice. The aim of the present study is to present and calibrate a new mechanistic model built in COMSOL MultiphysicsTM platform for the description of microalgae growth. Carbon-limited algal growth, transfer of gases to the atmosphere; and photorespiration, photosynthesis kinetics and photoinhibition are included. The model considers the growth of microalgae as a function of light intensity and temperature, as well as availability of nitrogen and other nutrients. The model was calibrated using experimental data from a case study based on the cultivation of microalgae species in synthetic culture medium. The model was able to reproduce experimental data. Simulations results show the potential of the model to predict microalgae growth and production, nutrient uptake, and the influence of temperature, light intensity and pH on biokinetic processes of microalgae.
Journal of Process Control, 2011
Oleaginous microalgae are seen as a potential major biofuel producer in the future since, under conditions of nitrogen deprivation, they can contain high amounts of lipids, while they consume CO 2 from power plants. These photosynthetic microorganisms are however rather different from the microorganisms usually used in biotechnology. In particular, predicting the behaviour of microalgal based processes is delicate because of the strong interaction between biology (microalgal development and respiration), and physics (light attenuation and hydrodynamics). This paper reviews existing models, and in particular Droop Model which has been widely used to predict microalgal behaviour under nutrient limitation. It details a model for photobioreactors or raceways, when both light and nutrients are limiting. The challenges and hurdles to improve photobioreactor modelling and control in order to optimise biomass or biofuel production are then discussed.
Model development for the growth of microalgae: A review
Renewable & Sustainable Energy Reviews, 2018
Despite attracting many attentions in the past decades, microalgal cultivation still faces many challenges for industrialisation. Growth, as one of the most crucial characteristics of a microalgal cultivation system, has been a significant subject for modelling. This paper presents a review of available models in the literature regarding the effect of process parameters such as light, temperature, nutrients, oxygen accumulation, salinity, and pH and carbon, on the growth rate of microalgal cells to understand their application in large-scale microalgal production. The existing models are classified based on the process conditions or parameters they considered in the formulation, and where multiple parameters were included the model was broken into separate functions, and each function was presented in the associated section. The most prominent result of this review is the huge gap between models and their validity for outdoor systems. It seems that to find suitable models for a real condition application, a new pathway is needed where models are developed based on the behaviour of the outdoor cultures in long-term. There are some effects such as adaptation which are difficult to model in short-term modelling while if the long-term approach is used these effects can be considered negligible. These characteristics of outdoor cultivation help in simplification of the models and less struggle in their validation. Moreover, using saline water is an effective way to improve the viability of algal production which requires understanding the relationship between growth and salinity of the medium. Such models are missing in the literature.
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...
In this study, a two phase flow for CO 2 and Microalgae suspension is considered to understand fluid dynamics phenomena after injecting CO 2 gas inside a tubular Photobioreactor (PBR).The growth rate of the microalgae cell is taken as a function of available sun light at Chittagong University of Engineering & Technology (CUET). The tubular PBR is considered in our study have the radius of 0.025m while the entire length is 20.94m. To observe the growth of microalgae cell we selected the 21 st June for a bright sunny and the longest day of a year. From the simulation after day seven we observed a very slow growth for the microalgae culture and the growth related to concentration of microalgae is increased by day length with respect to continuous sunlight. A small fluctuation of shear rate around U-loop area is also found in our simulation which may be caused to reduce the volumetric production due to cell fragility.
KINETICS OF Chlorella sp GROWTH MODELS IN REDUCING CO2 EMISSIONS
Rasayan Journal of Chemistry, 2019
CO 2 emissions resulting from human activities are relatively higher concentrations that disrupt the equilibrium system in the air and ultimately damage the environment and human well-being. One environmentally friendly solution for CO 2 gas removal is to use microalgae (Chlorella sp.). Chlorella sp. in photobioreactors has the ability to biofixate CO 2 gas. Chlorella sp. was chosen because of the most numerous in freshwater and seawater. The purpose of this study was to determine the kinetic model of the effect of adding substrate concentrations and flow rate variations on the growth and development rates of Chlorella sp. due to exposure to pure CO 2 gas emissions. This study uses pure CO 2 gas with a flow rate of 0.
Analysis of green algal growth via dynamic model simulation and process optimisation
Biotechnology and bioengineering, 2015
Chlamydomonas reinhardtii is a green microalga with the potential to generate sustainable biofuels for the future. Process simulation models are required to predict the impact of laboratory-scale growth experiments on future scaled-up system operation. Two dynamic models were constructed to simulate C. reinhardtii photo-autotrophic and photo-mixotrophic growth. A novel parameter estimation methodology was applied to determine the values of key parameters in both models, which were then verified using experimental results. The photo-mixotrophic model was used to accurately predict C. reinhardtii growth under different light intensities and in different photobioreactor configurations. The optimal dissolved CO2 concentration for C. reinhardtii photo-autotrophic growth was determined to be 0.0643 g · L(-1) , and the optimal light intensity for algal growth was 47 W · m(-2) . Sensitivity analysis revealed that the primary factor limiting C. reinhardtii growth was its intrinsic cell decay...