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Direct and rapid production of biodiesel from algae foamate using a homogeneous base catalyst as part of an intensified process

Lookup NU author(s): Dr Shurooq Al-Humairi, Dr Jonathan LeeORCiD, Professor Adam Harvey



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


© 2022 The Author(s). Microalgae are important biodiesel feedstocks because of their high lipid content and low land requirement for cultivation. One method of harvesting and concentrating algal biomass is by means of a foam column using surfactant CTAB as a collector and foaming agent, however, the downstream treatments for the “foamate” produced have not yet been investigated. Here, the freshwater microalgae strain, Chlorella vulgaris, was harvested by a continuous dispersed air flotation column and the foamate obtained was used as the feedstock for conversion to biodiesel via in situ reactive extraction using KOH as the catalyst. The process variables were methanol: oil molar ratio (100:1 to 1000:1), reaction temperature (40–60 °C) and reaction time (5–10 min). The maximum biodiesel yield from the foamate produced of 97% from C. vulgaris microalgae was accomplished at a molar ratio (methanol to oil) of 1000:1, a 60 °C temperature of reaction and a 10 min time of reaction. Longer reaction times resulted in reduced fatty acid methyl ester (FAME) yield due to saponification, converting the FAME to soap. High FAME yields were obtained despite the presence of significant quantities of free fatty acids (6% lipid) in the C. vulgaris biomass. The method also exhibited greater tolerance to water than that observed in conventional transesterification conditions. At a methanol: oil molar ratio of 1000:1, the method was not adversely affected by the presence of up to 80% level of moisture in the microalgae. Hence, a viable, FFA-tolerant, water-tolerant process has been demonstrated for direct conversion of microalgae foamate to biodiesel, at mild conditions (60 °C and below) in a short residence time (10 min).

Publication metadata

Author(s): Al-Humairi ST, Lee JGM, Harvey AP

Publication type: Article

Publication status: Published

Journal: Energy Conversion and Management: X

Year: 2022

Volume: 16

Print publication date: 01/12/2022

Online publication date: 19/08/2022

Acceptance date: 16/08/2022

Date deposited: 20/09/2022

ISSN (electronic): 2590-1745

Publisher: Elsevier Ltd


DOI: 10.1016/j.ecmx.2022.100284


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Funder referenceFunder name
Ministry of Higher Education and Scientific Research in Iraq (HESR)
University of Technology in Iraq