Innovative utilization of cactus gel: Transforming coal fines into sustainable briquettes

South Africa's coal industry is crucial for the nation’s economy and energy supply; however, the generation of coal fines during mining and processing creates serious environmental and public health concerns. Cactus gel, a biomass-derived binder well-suited to arid environments, was used in this study for coal fines briquetting due to its strong adhesive properties, which enable the formation of durable briquettes and may contribute to cleaner fuel by reducing emissions during combustion. Coal fines were mixed with cactus plant gel to enhance compressibility and durability. Different solid-to-liquid mixing ratios were examined, and the resulting mixture was moulded into briquettes. After curing, the samples underwent analysis to determine their unconfined compressive strength, proximate analysis, and chemical characterization. The results showed that initially, the briquettes did not pass the water resistance index requirements of 95%, as they disintegrated into a liquid-like substance. To mitigate this challenge, the briquettes were coated with paraffin wax. The 40:60 solid-to-liquid ratio briquettes had the highest calorific value at 26.57 MJ/kg, and the highest compressive strength of 0.375 MPa was observed in the 20:80 solid-to-liquid ratio, meeting the requirements for fuel briquettes. Cactus gel proved to be a highly effective natural binding agent for coal fines briquettes, significantly improving their structural integrity and energy content. This study presents a sustainable approach for the valorisation of coal fines through briquetting with cactus gel as a natural binder, effectively mitigating environmental and handling challenges while producing mechanically robust and environmentally cleaner fuel.