Bio-oil from hydrothermal liquefaction of microalgae cultivated in wastewater: An economic and life cycle approach

Silva, Thiago; Junior, Maurino Magno de Jesus; Magalhães, Iara; Ananias, Marina Stefany; Saleme Aona de Paula Pereira, Alexia; Rodrigues, Fábio de Ávila; Delgado dos Reis, Alberto José; Calijuri, Maria Lucia

http://hdl.handle.net/10400.9/6010

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Authors

Silva, Thiago

Junior, Maurino Magno de Jesus

Magalhães, Iara

Ananias, Marina Stefany

Saleme Aona de Paula Pereira, Alexia

Rodrigues, Fábio de Ávila

Delgado dos Reis, Alberto José

Calijuri, Maria Lucia

Abstract(s)

ABSTRACT: Although microalgae are a promising sustainable biofuel feedstock, their energy-intensive production and most environmental assessments rarely achieve the desired trade-off between productivity and sustainability. In this context, this study aims to evaluate the economic and environmental feasibility of producing bio-oil via hydrothermal liquefaction (HTL) of wastewater-grown microalgae at an industrial scale. Four scenarios varied production scale and steam source: sugarcane bagasse (SCB) in SC1 and SC3, liquefied petroleum gas (LPG) in SC2 and SC4. Each scenario processed microalgae at 300 degrees C for 30 min. Smaller-scale feedstock (1332.9 kg/h) in SC1 and SC2 produced 34.6 kg/h of bio-oil, while the larger feedstock (85,554.4 kg/h) in SC3 and SC4 yielded 2222.2 kg/h. Microalgae biomass cultivation costs dominated overall expenses (56-75 %). Economic analyses indicated minimum selling prices of 3.82-8.52 USD/kg, exceeding the average literature figure of 1.57 USD/kg. Life Cycle Assessment (LCA) showed SCB reduced fossil resource depletion by 14.97 % compared to LPG but increased emissions of nitrogen oxides, particulates, and toxic compounds, which are manageable via selective catalytic reduction and flue gas desulphurization. Cyclohexane as a solvent elevated human carcinogenic toxicity, greener alternatives could reduce toxicity but may cost more, requiring further cost analysis. Advancing this biorefinery route requires optimization of cultivation and processing costs, adoption of environmentally benign solvents, and implementation of emission control strategies to enable economically feasible and environmentally sustainable bio-oil production.

Keywords

Energy efficiency Biomass valorisation Biorefinery Microalgae Process simulation Sustainability

URI

http://hdl.handle.net/10400.9/6010

Citation

Silva, T., Jesus Jr, M., Magalhaes, I., Ananias, M., Pereira, A., Rodrigues, F., Reis, A. & Calijuri, M.L. (2025). Bio-oil from hydrothermal liquefaction of microalgae cultivated in wastewater: An economic and life cycle approach. In: Journal of Cleaner Production, 2025, vol. 512, article 145719. https://doi.org/10.1016/j.jclepro.2025.145719