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Title: A Screening Model to Predict Microalgae Biomass Growth in Photobioreactors and Raceway Ponds

Abstract

A microalgae biomass growth model was developed for screening novel strains for their potential to exhibit high biomass productivities under nutrient-replete conditions in photobioreactors or outdoor ponds. Growth is modeled by first estimating the light attenuation by biomass according to Beer-Lambert’s law, and then calculating the specific growth rate in discretized culture volume slices that receive declining light intensities due to attenuation. The model requires only two physical and two species-specific biological input parameters, all of which are relatively easy to determine: incident light intensity, culture depth, as well as the biomass light absorption coefficient and the specific growth rate as a function of light intensity. Roux bottle culture experiments were performed with Nannochloropsis salina at constant temperature (23 °C) at six different incident light intensities (5, 10, 25, 50, 100, 250, and 850 μmol/m2∙ sec) to determine both the specific growth rate under non-shading conditions and the biomass light absorption coefficient as a function of light intensity. The model was successful in predicting the biomass growth rate in these Roux bottle cultures during the light-limited linear phase at different incident light intensities. Model predictions were moderately sensitive to minor variations in the values of input parameters. The model wasmore » also successful in predicting the growth performance of Chlorella sp. cultured in LED-lighted 800 L raceway ponds operated at constant temperature (30 °C) and constant light intensity (1650 μmol/m2∙ sec). Measurements of oxygen concentrations as a function of time demonstrated that following exposure to darkness, it takes at least 5 seconds for cells to initiate dark respiration. As a result, biomass loss due to dark respiration in the aphotic zone of a culture is unlikely to occur in highly mixed small-scale photobioreactors where cells move rapidly in and out of the light. By contrast, as supported also by the growth model, biomass loss due to dark respiration occurs in the dark zones of the relatively less well mixed pond cultures. In addition to screening novel microalgae strains for high biomass productivities, the model can also be used for optimizing the pond design and operation. Additional research is needed to validate the biomass growth model for other microalgae species and for the more realistic case of fluctuating temperatures and light intensities observed in outdoor pond cultures.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1214301
Report Number(s):
PNNL-SA-90592
BM0102030
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Biotechnology and Bioengineering, 110(6):1583-1594
Additional Journal Information:
Journal Name: Biotechnology and Bioengineering, 110(6):1583-1594
Country of Publication:
United States
Language:
English
Subject:
microalgae biofuels; Nannochloropsis salina; Chlorella sp.; biomass growth model; biomass light absorption coefficient; specific growth rate as a function of light intensity; dark respiration; photobioreactor; raceway pond; LED-lighting

Citation Formats

Huesemann, Michael H., Van Wagenen, Jonathan M., Miller, Tyler W., Chavis, Aaron R., Hobbs, Watts B., and Crowe, Braden J. A Screening Model to Predict Microalgae Biomass Growth in Photobioreactors and Raceway Ponds. United States: N. p., 2013. Web. doi:10.1002/bit.24814.
Huesemann, Michael H., Van Wagenen, Jonathan M., Miller, Tyler W., Chavis, Aaron R., Hobbs, Watts B., & Crowe, Braden J. A Screening Model to Predict Microalgae Biomass Growth in Photobioreactors and Raceway Ponds. United States. https://doi.org/10.1002/bit.24814
Huesemann, Michael H., Van Wagenen, Jonathan M., Miller, Tyler W., Chavis, Aaron R., Hobbs, Watts B., and Crowe, Braden J. 2013. "A Screening Model to Predict Microalgae Biomass Growth in Photobioreactors and Raceway Ponds". United States. https://doi.org/10.1002/bit.24814.
@article{osti_1214301,
title = {A Screening Model to Predict Microalgae Biomass Growth in Photobioreactors and Raceway Ponds},
author = {Huesemann, Michael H. and Van Wagenen, Jonathan M. and Miller, Tyler W. and Chavis, Aaron R. and Hobbs, Watts B. and Crowe, Braden J.},
abstractNote = {A microalgae biomass growth model was developed for screening novel strains for their potential to exhibit high biomass productivities under nutrient-replete conditions in photobioreactors or outdoor ponds. Growth is modeled by first estimating the light attenuation by biomass according to Beer-Lambert’s law, and then calculating the specific growth rate in discretized culture volume slices that receive declining light intensities due to attenuation. The model requires only two physical and two species-specific biological input parameters, all of which are relatively easy to determine: incident light intensity, culture depth, as well as the biomass light absorption coefficient and the specific growth rate as a function of light intensity. Roux bottle culture experiments were performed with Nannochloropsis salina at constant temperature (23 °C) at six different incident light intensities (5, 10, 25, 50, 100, 250, and 850 μmol/m2∙ sec) to determine both the specific growth rate under non-shading conditions and the biomass light absorption coefficient as a function of light intensity. The model was successful in predicting the biomass growth rate in these Roux bottle cultures during the light-limited linear phase at different incident light intensities. Model predictions were moderately sensitive to minor variations in the values of input parameters. The model was also successful in predicting the growth performance of Chlorella sp. cultured in LED-lighted 800 L raceway ponds operated at constant temperature (30 °C) and constant light intensity (1650 μmol/m2∙ sec). Measurements of oxygen concentrations as a function of time demonstrated that following exposure to darkness, it takes at least 5 seconds for cells to initiate dark respiration. As a result, biomass loss due to dark respiration in the aphotic zone of a culture is unlikely to occur in highly mixed small-scale photobioreactors where cells move rapidly in and out of the light. By contrast, as supported also by the growth model, biomass loss due to dark respiration occurs in the dark zones of the relatively less well mixed pond cultures. In addition to screening novel microalgae strains for high biomass productivities, the model can also be used for optimizing the pond design and operation. Additional research is needed to validate the biomass growth model for other microalgae species and for the more realistic case of fluctuating temperatures and light intensities observed in outdoor pond cultures.},
doi = {10.1002/bit.24814},
url = {https://www.osti.gov/biblio/1214301}, journal = {Biotechnology and Bioengineering, 110(6):1583-1594},
number = ,
volume = ,
place = {United States},
year = {Sat Jun 01 00:00:00 EDT 2013},
month = {Sat Jun 01 00:00:00 EDT 2013}
}