Thermo-catalytic conversion of actual drax biomass combustion residue into porous carbon: A dual valorisation approach

The valorisation of combustion residues offers a sustainable route to support sustained development of biomass power plants. This study investigates the synthesis of Ca-enhanced porous carbons from biomass combustion residues sourced from Drax Power Station (UK) and post-consumer chicken eggshells. Unburnt biomass was selectively recovered through systematic drying, size fractionation, and ultrasonic treatment, producing a carbon-rich precursor with reduced inorganic contamination. The recovered biomass was systematically pyrolysed, Ca-enhanced, and activated to yield a structurally stable porous sorbent with a fixed carbon content of 61%. Raman analysis confirmed turbostratic carbon formation with consistent defect characteristics (ID/IG ≈ 0.65), while FTIR spectra showed substantial attenuation of lignocellulosic O H and C O functionalities following carbonisation. Surface enhancement was achieved via eggshell-assisted calcium incorporation through dry-mixing and Ca-ion impregnation, with the latter producing superior dispersion and controlled pore development. Subsequent physical activation demonstrated that CO 2 activation outperformed steam activation, generating predominantly microporous carbons with a total accessible surface area of 463 m 2 g −1 , micropore surface area of 384 m 2 g −1 and an estimated external surface area of 92 m 2 g −1 . The resulting surface area was comparable to those reported for several physically activated biomass-derived carbons while avoiding chemical activating agents.