Bio-crude oil production and valorization of hydrochar as anode material from hydrothermal liquefaction of algae grown on brackish dairy wastewater

• Published in: Fuel processing technology 2022-03, Vol.227, p.107119, Article 107119
• Main Authors: Yu, Jiuling, Audu, Meshack, Myint, Maung T., Cheng, Feng, Jarvis, Jacqueline M., Jena, Umakanta, Nirmalakhandan, Nagamany, Brewer, Catherine E., Luo, Hongmei
• Format: Article
• Language: English
• Subjects: Algae; Anode material; Anodes; Anodic cleaning; Biofuels; Biomass; Biomass-derived carbon; Brackish water; Brackish water-grown algae; By products; Byproducts; Carbon; Carbon content; Clean energy; Crude oil; Electrochemical analysis; Electrode materials; Energy consumption; Feasibility studies; Fossil fuels; Hydrothermal liquefaction; Liquefaction; Lithium ion battery; Lithium-ion batteries; Rechargeable batteries; Renewable energy; Wastewater; Water pollution
• ISSN: 0378-3820; 1873-7188
• DOI: 10.1016/j.fuproc.2021.107119

Hydrothermal liquefaction (HTL) is effective at recovering bioenergy from wet microalgae, which is used for cleaning polluted water body. In this study, a brackish water-grown microalgae polyculture was hydrothermally liquefied into 26.5 wt% bio-crude oil with an energy consumption ratio of 2.4, indicating an energy negative process for bioenergy production. To improve the economic feasibility of wastewater algae-to-bioenergy process, a HTL byproduct, hydrochar, has been recycled to assemble in lithium ion batteries (LIBs) as a renewable anode material. Owing to the organic components produced from HTL and high concentrations of impurities obtained from brackish water, HTL hydrochar needs to be post-treated (CO2 activation and ‘base-acid’ wash) to increase carbon content, leading to better electrochemical performance. By virtue of increased specific surface area (304.06 m2 g−1) and massive mesopores, post-treated hydrochar exhibits reversible discharge-charge capacity of 226 and 223 mAh g−1 at 0.1 A g−1 after 40 cycles. There is no related study to investigate the feasibility of brackish-grown algae-derived hydrochar as green anodes of LIBs. This integration will not only mitigate water pollution (algae treatment for brackish water), produce carbon-neutral alternative to fossil fuel (algae-derived biofuel production), but also valorize solid byproduct for generating clean energy (LIBs anodes synthesis from biomass-derived carbon). •Brackish water-grown microalgae gave 26.5 wt% bio-crude oil yield by HTL.•HTL byproduct-hydrochar was used as potential anode material in LIBs.•Post-treatments were crucial to improve electrochemical performance of hydrochar derived from high-ash biomass.•An integration of bio-crude oil production and solid byproduct valorization was evaluated.