Turning coffee waste into manufacturing feedstock

A UNSW SMaRT Centre research study has demonstrated a practical pathway for converting a common organic waste into a high-value advanced material.

Published in The Royal Society of Chemistry's Nanoscale Advances Journal, the study found that rather than treating spent coffee grounds as waste, they can become a feedstock for producing activated carbon suitable for energy-storage applications.

The work also shows that waste-derived activated carbon can outperform some commercial products, creating opportunities for:

• Circular economy solutions.
• Waste reduction.
• Sustainable materials manufacturing.
• Energy storage technologies such as supercapacitors and batteries.

The study successfully transformed spent coffee grounds into ultra-high-purity activated carbon (99.7%), significantly improving material quality and achieving nearly 60% better energy-storage performance than commercial activated carbon, demonstrating a promising circular-economy pathway from coffee waste to advanced energy materials.

Every year, large quantities of spent coffee grounds are discarded as waste. At the same time, there is growing demand for high-purity activated carbon used in energy storage devices, water treatment, air filtration, and advanced manufacturing.

The researchers explored whether coffee waste could be transformed into a high-quality activated carbon that performs better than many commercial products while supporting circular economy objectives.

The team developed a scalable purification process involving:

• Converting spent coffee grounds into biochar.
• Treating the material with sodium hydroxide (alkaline infusion).
• Using acid etching to remove remaining impurities.
• Applying thermal treatment to further improve carbon quality.

The goal was to remove ash, metal oxides, and other impurities that can reduce the performance of activated carbon