Investigation on low-cost CO2 absorbents from bagasse fly ash and unburned carbon residues from biomass power plant

This study reports the development of low-cost CO 2 adsorbents derived from solid residues using simple washing and steam or chemical treatments as a sustainable approach to mitigate rising CO 2 emissions. Fly ash (FA) and unburned carbon (UC) obtained from biomass combustion were converted into adsorbents with improved textural and CO 2 adsorption properties. Among the prepared materials, AUC-C exhibited the highest CO 2 adsorption capacity of 2.03 mmol/g at 1 bar and 25 °C and maintained stable performance over five adsorption–desorption cycles, indicating good reusability. Adsorption behavior for all samples was well described by the Langmuir model, with R 2 values exceeding 0.96. Steam treatment enhanced the CO 2 adsorption capacity of FA-based adsorbents from 0.11 to 0.24 mmol/g, corresponding to an improvement of approximately 118 %. Cost analysis showed that washed UC was the most cost-effective adsorbent, with a capture cost of 2.25 USD per mole of CO 2 , while steam-activated materials also exhibited low costs (2.41 USD per mole of CO 2 ). Overall, all prepared adsorbents were substantially less expensive than commercial alternatives.