Thesis

Brewing up solutions : developing high-performance adsorbents from spent coffee grounds for carbon capture

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T17684
Person Identifier (Local)
  • 202161978
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Qualification Name
Department, School or Faculty
Abstract
  • The development of low-cost, regenerable adsorbents for post-combustion carbon capture is critical for realising scalable carbon capture and storage (CCS) technologies. This study investigates the use of spent coffee grounds (SCG), an abundant organic waste stream, as a precursor for producing high-performance biochar-based CO₂ sorbents. Through a systematic Design of Experiments (DoE) framework, SCG-derived biochars were synthesised via physical (CO₂), chemical (KOH, potassium oxalate), and biological (fungal) activation methods, with the aim of optimising porosity, surface chemistry, and CO₂ capture performance under realistic flue gas conditions. Key findings demonstrate that activation route significantly influences both textural and chemical properties. EX37-850-15-CO₂-600, a nitrogen-rich, microporous sample prepared via single-step CO₂ activation, exhibited the highest low-pressure CO₂ uptake (0.76 mmol g⁻¹ at 150 mbar and 60 °C), strong initial enthalpy of adsorption (42.25 kJ mol⁻¹), and the greatest CO₂/N₂ selectivity (up to 44 at 1000 mbar). In contrast, EX53-900-2H-KOX-1:1 (pre-pyrolysed)—produced by potassium oxalate activation—showed superior regenerability under cyclic pressure swing conditions, retaining >95% capacity after 60 cycles with a working capacity of 0.735 mmol g⁻¹ between 150–50 mbar. IAST-based binary gas analysis confirmed that nitrogen functionalities play a decisive role in enhancing selectivity beyond what is achievable through porosity alone. This work represents the first comprehensive comparison of physical, chemical, and biological activation methods applied to SCG under a DoE framework, linking activation parameters to sorbent performance across capacity, selectivity, kinetics, and stability. It highlights a key trade-off between affinity and regenerability, underscoring the importance of aligning sorbent properties with capture process requirements. The findings establish SCG-derived biochars as viable, sustainable alternatives to synthetic sorbents, and offer a pathway for integrating circular economy principles into CCS deployment.
Advisor / supervisor
  • Fletcher, Ashleigh
Date Created
  • 2025

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