Physics of ultra-high bioproductivity in algal photobioreactors

Greenwald, Efrat; Gordon, Jeffrey M.; Zarmi, Yair

doi:10.1063/1.3701168

Cited by 18 publications

(14 citation statements)

References 29 publications

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“…The quest to improve the bioproductivity of algae is largely prompted by their value for biofuels, nutritional supplements, and pharmaceuticals (Borowitzka and Moheimani, 2013). Previous investigations have focused on (1) trying to improve the efficiency with which the photosynthetic apparatus can exploit incident photons as well as (2) more efficiently distributing those photons among the algae in a photobioreactor (Tennessen et al, 1995;Gebremariam and Zarmi, 2012;Greenwald et al, 2012;Zarmi et al, 2013;Gordon and Polle, 2007;Abu-Ghosh et al, 2015).…”

Section: Background and Motivationmentioning

confidence: 99%

Enhanced Algal Photosynthetic Photon Efficiency by Pulsed Light

et al. 2020

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We present experimental results demonstrating that, relative to continuous illumination, an increase of a factor of 3-10 in the photon efficiency of algal photosynthesis is attainable via the judicious application of pulsed light for light intensities of practical interest (e.g., average-to-peak solar irradiance). We also propose a simple model that can account for all the measurements. The model (1) reflects the essential rate-limiting elements in bioproductivity, (2) incorporates the impact of photon arrival-time statistics, and (3) accounts for how the enhancement in photon efficiency depends on the timescales of light pulsing and photon flux density. The key is avoiding ''clogging'' of the photosynthetic pathway by properly timing the light-dark cycles experienced by algal cells. We show how this can be realized with pulsed light sources, or by producing pulsed-light effects from continuous illumination via turbulent mixing in dense algal cultures in thin photobioreactors.

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Section: Background and Motivationmentioning

confidence: 99%

Enhanced Algal Photosynthetic Photon Efficiency by Pulsed Light

et al. 2020

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“…11 Maintaining the optimum illumination throughout a photobioreactor is inhibited by self-shading, where cells closest to the light source receive excess illumination at the detriment of cells deeper within the culture, which are less illuminated. [12][13][14][15] This effect can be mitigated by continuously mixing, causing cells to travel between high and low intensity regions of the photobioreactor, such that they receive the optimal timeaveraged intensity. Bioreactors have shown increased performance with increased mixing due to improved chemical transport and better light utilization.…”

Section: Introductionmentioning

confidence: 99%

“…Bioreactors have shown increased performance with increased mixing due to improved chemical transport and better light utilization. [12][13][14]16 Another important irradiance parameter is spectral composition. Microalgal growth is dependent on wavelength by virtue of cell pigmentation, which varies largely between species.…”

Section: Introductionmentioning

confidence: 99%

Microalgae on display: a microfluidic pixel-based irradiance assay for photosynthetic growth

2015

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Microalgal biofuel is an emerging sustainable energy resource. Photosynthetic growth is heavily dependent on irradiance, therefore photobioreactor design optimization requires comprehensive screening of irradiance variables, such as intensity, time variance and spectral composition. Here we present a microfluidic irradiance assay which leverages liquid crystal display technology to provide multiplexed screening of irradiance conditions on growth. An array of 238 microreactors are operated in parallel with identical chemical environments. The approach is demonstrated by performing three irradiance assays. The first assay evaluates the effect of intensity on growth, quantifying saturating intensity. The second assay quantifies the influence of time-varied intensity and the threshold frequency for growth. Lastly, the coupled influence of red-blue spectral composition and intensity is assessed. Each multiplexed assay is completed within three days. In contrast, completing the same number of experiments using conventional incubation flasks would require several years. Not only does our approach enable more rapid screening, but the short optical path avoids self-shading issues inherent to flask based systems.

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“…When light passes through the PBR, microalgae will absorb part of such light and transform it into chemical energy. The equation describing the absorption of light is called the Lambert-Beer Law, which states that (Greenwald, Gordon & Zarmi, 2012): Where z is the depth of the flat plate PBR, X is cell density of microalgae, α is the absorption coefficient, I(z) is the irradiance at the length z, and I 0 is the irradiance of the light source. For the design of the PBR it is important to maintain sufficient light imposed upon the microalgae to saturate the active sites during the passage of the photon, but just enough to ensure that photoinhibition does not take place.…”

Section: Light Regimementioning

confidence: 99%

“…Table 1 shows the employed model parameters. The values were taken from different authors (Carvalho & Malcata, 2001;Kurano & Miyachi, 2005;Greenwald et al, 2012;Chisti, 1989) or calculated assuming that we operate at the assumed conditions previously described. If it reaches steady state and establishes optimal growth rate conditions, the analysis will be conducted like a single chemostat without biomass input, i.e., equation 13, since it is the operation that would give higher productivity.…”

Section: Ii)mentioning

confidence: 99%

A method for the design of a continuous microalgae culture photobioreactor in series with recirculation system.

Vargas¹,

Pérez²,

Espinosa³

2017

CT&F Cienc. Tecnol. Futuro

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Nowadays, there are functional pilot scale PhotoBioReactors (PBRs), which present serious challenges when performing a scaling up process for an industrial application. The aim of this research was to evaluate the design of several continuous flat plate PBRs connected in series, while allowing constant circulation from the last to the first unit. Scaling up feasibility using the adjunction of new units, instead of PBRs volume increase is analyzed. An ad hoc mathematical model based on mass balances and constitutive equations from literature was constructed; the model integrates the illumination and mass transfer effects on microalgae growth kinetics by a complete model solution. Unfortunately, the model is too complex to be analyzed by conventional methods. Furthermore, it presents problems when evaluated by numeric methods as the results do not have physical meaning and the initial condition has strong effect on the final solution. Hence, this paper presents a simple method to analyze the design of this kind of continuous system. The method allows the design parameters calculation of PBRs system resulting physically in a simple way without having to guess possible system solutions. Moreover it is also shown that the continuous PBRs in series with a recirculation system obtain good amount of microalgae productivity. ABSTRACT METODO PARA EL DISEÑO DE FOTOBIOREACTORES CONTINUOS EN 102A tualmente existem fotobioreatores de escala piloto funcionais, porém trazem sérias complicações para executar um processo de escalonamento para uma implementação industrial. Este trabalho propõe avaliar a concepção de vários fotobioreatores contínuos de placa plana conectados em série com recirculação desde a última unidade até a primeira, para analisar a viabilidade do escalonamento da produtividade a partir da adição de mais unidades em vez de aumentar o volume do fotobioreator. Para este propósito um modelo matemático foi construído baseado nos balanços de massa e equações constitutivas da literatura, nas quais se integram os efeitos da iluminação e a transferência de massa na cinética de crescimento das microalgas. Infelizmente, obtém-se um modelo que é muito complexo para ser avaliado através de meios convencionais. Além disso, apresenta problemas ao ser avaliado com métodos numéricos, há que se obtêm resultados que não têm explicação física e a solução tem uma grande dependência das condições iniciais. Portanto, este artigo apresenta um método simples para a análise do desenho deste tipo de sistema contínuo. O método permite obter os parâmetros do desenho do sistema de fotobioreatores e soluções com sentido físico de forma simples, sem ter que tentar possíveis soluções do sistema. Além disso, mostra-se que o sistema de fotobioreatores contínuos em série com recirculação oferece uma boa produtividade de microalgas. Hoy en día, existen fotobiorreactores (PBRs de su sigla en inglés) a escala piloto funcionales, que presentan serios desafíos al momento de realizar un proceso de escalamiento para una aplicación industrial. Este t...

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Physics of ultra-high bioproductivity in algal photobioreactors

Cited by 18 publications

References 29 publications

Enhanced Algal Photosynthetic Photon Efficiency by Pulsed Light

Enhanced Algal Photosynthetic Photon Efficiency by Pulsed Light

Microalgae on display: a microfluidic pixel-based irradiance assay for photosynthetic growth

A method for the design of a continuous microalgae culture photobioreactor in series with recirculation system.

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