Improving bio-oil chemical profile of seaweeds through anaerobic fermentation pre-treatment

Abstract

Biomass pre-treatments for bio-oil quality improvement are mainly based on thermal and chemical methods which are costly and hence reduce the sustainability of pyrolysis-based refineries. In this paper, anaerobic digestion (AD) and dark fermentation (DF) are proposed as alternative ‘green’ pre-treatments to improve this situation. For this purpose, three seaweeds namely Sargassum polycystum, (Phaephyta), Gracilaria tenuistipitata, (Rhodophyta) and Ulva reticulata, (Chlorophyta) with high ash and oxygen contents were pre-treated to improve their composition and structure prior to pyrolysis. The results reveal that both biological pre-treatments affected, positively, the composition and structure of the seaweed biomass with AD pre-treatment reducing N and S contents by 86% and 63%, respectively. DF was more efficient in terms of ash and moisture reduction with 25% and 70%, respectively. In addition, oxygen (O) reduction by 27% was observed after DF which was evidenced by FTIR spectroscopy indicating the reduction of most oxygen-containing functional groups in the biomass. On the other hand, the carbon (C) content increased in DF pre-treated seaweeds up to 42%, almost two times higher relative content than C in the raw seaweed. The changes in the composition of pre-treated seaweeds resulted in changes in their thermal degradation and the volatile profiles produced during pyrolysis. Interestingly, anhydrosugars and furans which account for some 70% (by area) in raw seaweeds markedly declined or become undetectable after DF pre-treatment and correspondingly more acetic acid and hydrocarbons were produced while after AD more aromatics with high toluene content (ca.17%) were generated. The results indicate that bio-oil with profiles more similar to petroleum-based composition i.e. rich in hydrocarbons and low in anhydrosugars, N and S can be generated by AD and DF pre-treatments and opens up the possibility of these approaches to effect cost reduction in the overall generation of bio-based fuels.

Publication DOI: https://doi.org/10.1016/j.enconman.2021.114632
Divisions: College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
College of Engineering & Physical Sciences
Additional Information: © 2021, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ Funding: The authors acknowledge the European Union and Horizon 2020 for the financial support of the action H2020-MSCA-IF-2015, TASAB, Grant 706642.
Uncontrolled Keywords: Anaerobic digestion,Dark fermentation,Pyrolysis,Seaweeds,Thermogravimetric analysis,Pyrolysis volatiles
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Related URLs: https://linking ... 196890421008086 (Publisher URL)
PURE Output Type: Article
Published Date: 2021-10-01
Published Online Date: 2021-08-23
Accepted Date: 2021-08-09
Authors: Wahab, Mohamed Ali
Kebelmann, Katharina
Schartel, Bernhard
Griffiths, Gareth (ORCID Profile 0000-0002-7507-6945)

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Version: Accepted Version

Access Restriction: Restricted to Repository staff only until 23 August 2022.

License: Creative Commons Attribution Non-commercial No Derivatives


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