Hydrothermal Carbonisation of Novel Biomasses
type: CreativeWork
description: Renewable sources of thermal and chemical energy are needed in order to satisfy the world’s ever growing energy needs while limiting the rise of global temperatures below 2 °C above pre-industrial levels. Plant biomass is a vast resource which if harnessed properly could help revolutionise the global energy economy. Hydrothermal Carbonisation (HTC) is a technology wherein biomass exposed to subcritical water at 180 °C – 260 °C is thermochemically converted into an energy-dense “hydrochar” with strong thermal and elemental similarities to fossil coal. However, key aspects of the HTC reaction remain unknown, especially with regard to the degradation of the key biochemical macromolecules hemicellulose, cellulose, lignin and protein. In this thesis, three novel biomasses, Australian saltbush, hemp and macroalgae, were subjected to HTC and the hydrochars analysed for fuel properties and biochemical composition. The breakdown of the key macromolecules was then described using kinetic modelling to build a mechanistic model of the overall conversion of biomass to hydrochar. Each of the three biomasses underwent profound chemical changes during the HTC reaction, resulting in much lower oxygen content, and much higher carbon content. This caused the energy content of the hydrochars to rise to levels that rivaled or even exceeded those observed in fossil lignites. In addition, the ash content of the biomass was reduced, although certain reaction conditions at higher intensities saw the reabsorbence of inorganic elements back into the char. A twin-pathway mechanistic model was adapted and developed from the literature to describe the overall HTC process and the formation of two different kinds of hydrochar: Mechanism 1, involving solid phase conversions that yield “primary char” derived directly from undissolved and partially converted starting material; and Mechanism 2, a two-step pathway that involves the degradation of the feedstock into dissolved intermediates, and the subs…
abstract: Renewable sources of thermal and chemical energy are needed in order to satisfy the world’s ever growing energy needs while limiting the rise of global temperatures below 2 °C above pre-industrial levels. Plant biomass is a vast resource which if harnessed properly could help revolutionise the global energy economy. Hydrothermal Carbonisation (HTC) is a technology wherein biomass exposed to subcritical water at 180 °C – 260 °C is thermochemically converted into an energy-dense “hydrochar” with strong thermal and elemental similarities to fossil coal. However, key aspects of the HTC reaction remain unknown, especially with regard to the degradation of the key biochemical macromolecules hemicellulose, cellulose, lignin and protein. In this thesis, three novel biomasses, Australian saltbush, hemp and macroalgae, were subjected to HTC and the hydrochars analysed for fuel properties and biochemical composition. The breakdown of the key macromolecules was then described using kinetic modelling to build a mechanistic model of the overall conversion of biomass to hydrochar. Each of the three biomasses underwent profound chemical changes during the HTC reaction, resulting in much lower oxygen content, and much higher carbon content. This caused the energy content of the hydrochars to rise to levels that rivaled or even exceeded those observed in fossil lignites. In addition, the ash content of the biomass was reduced, although certain reaction conditions at higher intensities saw the reabsorbence of inorganic elements back into the char. A twin-pathway mechanistic model was adapted and developed from the literature to describe the overall HTC process and the formation of two different kinds of hydrochar: Mechanism 1, involving solid phase conversions that yield “primary char” derived directly from undissolved and partially converted starting material; and Mechanism 2, a two-step pathway that involves the degradation of the feedstock into dissolved intermediates, and the subs…
author: Keiller, Benjamin Geoffrey
language: en
keywords: Hydrothermal Carbonisation, HTC, hydrochar, reaction, mechanism, kinetics, saltbush, hemp, macroalgae, Ulva, Oegodonium
date published: 2020
date modified: 2026-07-24T00:50:50Z
provider: University of Adelaide
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Adelaide

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2440/125700