Targeting greens and yellows: A solar biorefinery analysis for the microalgae-based co-production of pigments, proteins, and fuel

• Published in: Algal research (Amsterdam) Vol. 74; p. 103187
• Main Authors: Karan, Hakan, Roles, John, Hankamer, Ben, Ross, Ian L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2023
• Subjects: amino acid composition; biocompatible materials; bioeconomics; Biofuel; biomass; biorefining; Chlorella; Copper chlorophyllin; cost effectiveness; feedstocks; fractionation; fuels; hydrothermal liquefaction; Life cycle analysis; liquids; Lutein; markets; medicine; microalgae; Microalgae biorefinery; molecular weight; plant source protein; Protein; saponification; Techno-economic; water solubility; Copper chlorophyllin; Life cycle analysis; Lutein; Biofuel; Techno-economic; Protein; Microalgae biorefinery
• ISSN: 2211-9264; 2211-9264
• DOI: 10.1016/j.algal.2023.103187

Microalgae biorefineries can enable cost effective cascaded biomass use to produce multiple product and revenue streams (e.g., protein-rich foods & feeds, pigments, biomaterials and high-density liquid fuels). The aim of this work is to develop a multi-product microalgae biorefinery simulation that employs a green chemistry-based alkaline saponification treatment to extract proteins, chlorophyllins, and lutein from microalgal (Chlorella sp.) biomass and subject it to techno-economic evaluation for a 50-ha facility. Optimisation of the saponification parameters revealed that the most value-generating strategy is a sequential saponification in which the biomass is first treated at mild conditions (0.4 % NaOH, 45 °C, 0.5 h) to recover a high quality protein fraction (with a calculated extraction efficiency of 42.5 %), followed by a harsher treatment (4 % NaOH, 70 °C, 8.5 h) to extract carotenoids and recover chlorophyllins for the synthesis of copper chlorophyllin. Water-insoluble chlorophylls are usually not refined, but their water-soluble and stable copper chlorophyllin derivatives offer significant utility for materials science, nutrition, and biomedicine. The obtained protein fraction has a purity of 44 %. It contains high molecular weight proteins and has a relatively unchanged amino acid composition, making it competitive with common plant-based protein meals on the market. The purities of the obtained carotenoid (mainly lutein) and the copper chlorophyllin fractions are estimated to be 5.47 % and 10.9–13.6 %, respectively. The process also produced a low-nitrogen fuel feedstock that can be converted into renewable diesel using hydrothermal liquefaction. The techno-economic analysis results show that at a 10 % internal rate of return (IRR) competitive bioproduct valuation (7 US$·kg−1 for 5 % lutein, 16 US$·kg−1 for 10 % Cu-chlorophyllin, 3.28 US$·kg−1 for 44 % protein, and US$0.67 L−1 for renewable diesel) can be achieved, which shows promise for saponification as a major biomass fractionation process. Multi-product microalgae biorefineries will help achieve a circular bioeconomy. •Saponification was used to generate four co-products from microalgae.•Co-products included chlorophyllin, lutein, protein, and biofuel feedstock.•High yields and purities were achieved for pigment and protein extraction.•TEA and LCA were performed on chlorophyllin, lutein, protein, and biofuel production.•A fuel price of US$0.67 L−1 was achieved after competitive co-product valuation.