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Building a cascading multi-product biorefinery process for Ascophyllum nodosum: a green chemistry approach

Olivares Molina, Alex; (2021) Building a cascading multi-product biorefinery process for Ascophyllum nodosum: a green chemistry approach. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Brown macroalgae are an attractive third-generation feedstock for biofuel, as well as a source of natural products. A cascading biorefinery approach extracts potentially bioactive compounds, i.e., polyphenols, fucoidan, and commodity products i.e., alginate, proteins in the same process. In order to design a green chemistry-compliant process and reduce the use of organic solvents in bioactive product extraction, aqueous two-phase systems (ATPS) and low-concentration biodegradable acid extractions were applied. The present work aimed to develop a multi-product biorefinery concept using Ascophyllum nodosum as a model feedstock using life cycle assessment (LCA), techno-economic analysis (TEA), and technical feasibility trials (TFT) as early-design tools for its development. After a biochemical characterisation of three potential model species, A. nodosum was selected as model feedstock based on the high accumulation of high-value products with potential breakthrough in the market. A.nodosum exhibited higher contents of polyphenols, lipids, protein, and minerals than the other species analysed, with 4.63% DW, 8.13% DW, 11.33% DW, and 29.54% DW, respectively. Once the biochemical characterisation was completed, three biorefining scenarios using different technology pathways (solvent, physicochemical, and green techniques) were modelled to process 1,000 metric tonnes (MT) biomass/year, in order to evaluate their economic and environmental metrics. From all evaluated scenarios, a green chemistry-compliant cascading sequence showed the lowest capital expenditure (CAPEX) (£30 million), operational expenditure (OPEX) (£11 million), cost of goods per kg of feedstock processed (CoG/kg) (£0.08) and production costs (£0.03/kg), along with the highest internal rate of return (IRR) (75.0%). Additionally, this scenario exhibited the lowest environmental impacts in all categories assessed, around 2 – 10 times lower than the other scenarios. In addition, the cascading sequence performance was evaluated to obtain first-hand data and re-iterate the models. The cascading sequence approach has been proposed to maximise resource efficiency and, in this work, a cascading sequence aimed at the sequential extraction of fucoidan, alginate, polyphenols, and proteins. Bioprocessing hotspots were identified for polyphenol and fucoidan extraction steps and further optimised using automated high-throughput screenings (HTS) and Design of Experiments (DoE), recovering 89% of total polyphenols, and showing a 33% increase in fucoidan recovery. Finally, after completing the bioprocessing hotspots, economic and environmental models were re-iterated to confirm the robustness of the biorefinery concept developed. The re-iterated version of the green chemistry-compliant cascading sequence exhibited better recovery performance in the optimised extraction stages, and thus showed better sales revenues (£91 million) than its previous version, a higher IRR (82.1%), and lower CoG/kg (£0.05) and production costs (£0.01/kg). The re-iterated version of the cascading sequence also exhibited the lowest environmental impacts in every category assessed, of all scenarios analysed in this project. These findings confirm that a holistic approach to early bioprocesses design is a valuable addition for decision-making tool options in the development of green-compliant multi-product third generation biorefineries.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Building a cascading multi-product biorefinery process for Ascophyllum nodosum: a green chemistry approach
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Biochemical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10138572
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