Comparative characterisation and phytotoxicity assessment of biochar and hydrochar derived from municipal wastewater microalgae biomass

[Display omitted] •Municipal wastewater derived microalgae are used to produce biochar and hydrochar.•Microalgae biochar promotes the germination and seedling growth.•Microalgae hydrochar can inhibit the germination due to the organic acids.•Post-pyrolysis and organic solvent washing are proved to b...

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Bibliographic Details
Published in:Bioresource technology 2023-10, Vol.386, p.129567-129567, Article 129567
Main Authors: Sun, Jiacheng, Benavente, Veronica, Jansson, Stina, Mašek, Ondřej
Format: Article
Language:English
Subjects:
Agricultural use
Biochar
biomass
carbon sequestration
Carbon storage
Carbonization
Comparative characterizations
Dichloromethane
germination
Micro-algae
Microalgae
Microorganisms
Municipal wastewaters
nutrient
Nutrient contents
phytotoxicity
Property
Pyrolysis
Risk assessment
Storage abilities
Tertiary treatment
wastewater
Wastewater treatment
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Summary:[Display omitted] •Municipal wastewater derived microalgae are used to produce biochar and hydrochar.•Microalgae biochar promotes the germination and seedling growth.•Microalgae hydrochar can inhibit the germination due to the organic acids.•Post-pyrolysis and organic solvent washing are proved to be effective methods mitigating phytotoxicity of hydrochar. Microalgae, originating from a tertiary treatment of municipal wastewater, is considered a sustainable feedstock for producing biochar and hydrochar, offering great potential for agricultural use due to nutrient content and carbon storage ability. However, there are risks related to contamination and these need to be carefully assessed to ensure safe use of material from wastewater microalgae. Therefore, this study compared the properties and phototoxicity of biochar and hydrochar produced via pyrolysis and hydrothermal carbonisation (HTC) of microalgae under different temperatures and residence times. While biochar promoted germination and seedling growth by up to 11.0% and 70.0%, respectively, raw hydrochar showed strong phytotoxicity, due to the high content of volatile matter. Two post-treatments, dichloromethane (DCM) washing and further pyrolysis, proved to be effective methods for mitigating phytotoxicity of hydrochar. Additionally, biochar had 35.8–38.6% fixed carbon, resulting in higher carbon sequestration potential compared to hydrochar.
ISSN:0960-8524
1873-2976
1873-2976
DOI:10.1016/j.biortech.2023.129567