Oxidative torrefaction of microalgae Chlorella sorokiniana: Process optimization by central composite design

Charles B Felix; Wei-Hsin Chen; Jo-Shu Chang; Young-Kwon Park; Samrand Saeidi; Gopalakrishnan Kumar

doi:10.1016/j.biortech.2023.129200

Oxidative torrefaction of microalgae Chlorella sorokiniana: Process optimization by central composite design

Bioresour Technol. 2023 Aug:382:129200. doi: 10.1016/j.biortech.2023.129200. Epub 2023 May 19.

Authors

Charles B Felix¹, Wei-Hsin Chen², Jo-Shu Chang³, Young-Kwon Park⁴, Samrand Saeidi⁵, Gopalakrishnan Kumar⁶

Affiliations

¹ Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan; Department of Mechanical Engineering, De La Salle University, 2401 Taft Avenue, 0922, Manila, Philippines.
² Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung 407, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan. Electronic address: weihsinchen@gmail.com.
³ Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung 407, Taiwan; Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan; Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan.
⁴ School of Environmental Engineering, University of Seoul, Seoul 02504, Republic of Korea.
⁵ Department of Applied and Environmental Chemistry, Interdisciplinary Excellence Centre, University of Szeged, H-6720, Rerrich Belater 1, Szeged, Hungary; Biotechnology Center, Silesian University of Technology, 8 Krzywousty St., 44-100 Gliwice, Poland.
⁶ Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Box 8600 Forus, 4036 Stavanger, Norway.

PMID: 37211235
DOI: 10.1016/j.biortech.2023.129200

Abstract

Microalgae are currently not viable as solid biofuels owing to their poor raw fuel properties. Torrefaction under oxidative media offers a cost-effective and energy-efficient process to address these drawbacks. A design of experiment was conducted using central composite design with three factors: temperature (200, 250, and 300 °C), time (10, 35, and 60 min), and O₂ concentration (3, 12, and 21 vol%). The responses were solid yield, energy yield, higher heating value, and onset temperatures at 50% and 90% carbon conversion determined from thermogravimetric analysis. Temperature and time significantly affected all responses, while O₂ concentration only affected higher heating value, energy yield and thermodegradation temperature at 90% conversion. Oxidative torrefaction of microalgae is recommended to be conducted at 200 °C, 10.6 min, 12% O₂ where the energy yield and enhancement factor are 98.73% and 1.08, respectively. It is also more reactive under an air environment compared to inert torrefaction conditions.

Keywords: Biochar; Bioenergy; Central composite design; Microalgae; Optimization; Oxidative torrefaction.

MeSH terms

Biofuels
Biomass
Chlorella*
Microalgae* / metabolism
Oxidative Stress
Temperature

Substances

Biofuels