Hydrothermal liquefaction (HTL) is a promising technology that can produce biocrude oil from wet biomass. The biocrudes, while generally acknowledged to be more stable than pyrolysis oils, are still thought to degrade relatively quickly, which limits their applicability. In this investigation, the storage stability of biocrude produced from hydrothermal liquefaction of microalgae was systematically studied over 60 days, and the effect of the storage material, feedstock species, liquefaction temperature and storage temperature were assessed. Biocrudes obtained at 300 °C and 350 °C from the microalgae Spirulina and Chlorella vulgaris were stored at three temperatures: cold (4 °C), ambient (20 °C) and elevated temperatures (35 °C), over the two-month period. The dynamic viscosity, higher heating value, thermogravimetric analysis and elemental and chemical composition were assessed. The viscosity of the biocrudes only increased considerably at 35 °C. The reaction temperature and biomass type were also strong determining factors of the impact on biocrude stability. Biocrudes produced from C. vulgaris were more stable than the Spirulina, and the crudes formed at 350 °C were considerably less reactive than those produced at 300 °C. This demonstrates that biocrudes can be stored without substantial degradation, allowing a more flexible approach to upgrading to value products.
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment