149
© Springer Nature Switzerland AG 2021
K. K. Pant et al. (eds.), Catalysis for Clean Energy and Environmental
Sustainability, https://doi.org/10.1007/978-3-030-65017-9_6
Catalytic and Non-Catalytic Hydrothermal
Liquefaction of Microalgae
Eleazer P. Resurreccion and Sandeep Kumar
Abstract Hydrothermal liquefaction (HTL) is an attractive thermochemical pathway that converts microalgal cells into biocrude which can be upgraded and refined
into drop-in transportation fuel. HTL is propitious from an environmental sustainability standpoint because the reaction requires medium temperatures (200–400 °C)
and high pressures (5–25 MPa) (subcritical and supercritical conditions) for a relatively short period of time (10–60 min) without the need for dewatering and drying
of the microalgal culture (wet microalgae with cultivation culture). Instead, water
provides dual use to the reaction: as a solvent and as a catalyst. At HTL conditions,
water is a reactive nonpolar species with high miscibility in organics. It solubilizes
even the recalcitrant microalgal components such as lignin to produce biocrude,
aqueous, gaseous, and solid products. This chapter discusses the process and chemistry of microalgae HTL, the role of water in the reaction, the difference between
catalytic and non-catalytic HTL as it applies to microalgae, and perspectives and
direction on the state of research for microalgae HTL.
Keywords Microalgae · Hydrothermal liquefaction · Biocrude · Subcritical water
· Algaenans · Decarboxylation
1 Introduction
The production of sustainable liquid fuels from renewable sources has become
increasingly challenging in recent years due to the substantial energy demand
brought about by rising population. This demand is largely supplied by limited fossil fuel reserves with remarkable effect on global climate change [1]. The world’s
E. P. Resurreccion (*)
Department of Civil Engineering Technology, Montana State University-Northern,
Havre, MT, USA
e-mail: e.p.resurreccion@gmail.edu
S. Kumar
Department of Civil and Environmental Engineering, Old Dominion University,
Norfolk, VA, USA
e-mail: skumar@odu.edu
© Springer Nature Switzerland AG 2021
K. K. Pant et al. (eds.), Catalysis for Clean Energy and Environmental
Sustainability, https://doi.org/10.1007/978-3-030-65017-9_6
Catalytic and Non-Catalytic Hydrothermal
Liquefaction of Microalgae
Eleazer P. Resurreccion and Sandeep Kumar
Abstract Hydrothermal liquefaction (HTL) is an attractive thermochemical pathway that converts microalgal cells into biocrude which can be upgraded and refined
into drop-in transportation fuel. HTL is propitious from an environmental sustainability standpoint because the reaction requires medium temperatures (200–400 °C)
and high pressures (5–25 MPa) (subcritical and supercritical conditions) for a relatively short period of time (10–60 min) without the need for dewatering and drying
of the microalgal culture (wet microalgae with cultivation culture). Instead, water
provides dual use to the reaction: as a solvent and as a catalyst. At HTL conditions,
water is a reactive nonpolar species with high miscibility in organics. It solubilizes
even the recalcitrant microalgal components such as lignin to produce biocrude,
aqueous, gaseous, and solid products. This chapter discusses the process and chemistry of microalgae HTL, the role of water in the reaction, the difference between
catalytic and non-catalytic HTL as it applies to microalgae, and perspectives and
direction on the state of research for microalgae HTL.
Keywords Microalgae · Hydrothermal liquefaction · Biocrude · Subcritical water
· Algaenans · Decarboxylation
1 Introduction
The production of sustainable liquid fuels from renewable sources has become
increasingly challenging in recent years due to the substantial energy demand
brought about by rising population. This demand is largely supplied by limited fossil fuel reserves with remarkable effect on global climate change [1]. The world’s
E. P. Resurreccion (*)
Department of Civil Engineering Technology, Montana State University-Northern,
Havre, MT, USA
e-mail: e.p.resurreccion@gmail.edu
S. Kumar
Department of Civil and Environmental Engineering, Old Dominion University,
Norfolk, VA, USA
e-mail: skumar@odu.edu