Development of a novel bio char for CO2 capture and biogas upgrade: Static and dynamic testing

The optimization of the pyrolysis of the spruce sawdust was conducted based on the yield, textural properties, and static capture capacity of the chars to generate a new micro porous char for biogas upgrade. The nature of the precursor (C: 45.68 %, H: 6.08 %, N: 0.15 %, and 0.34 % ash content) helped to tune the porosity of the char for capturing CO 2 from gas streams and biogas. The optimization of the pyrolysis at 700 °C, a heating rate of 10 °C / min and holding time of 1 hour, produced a microporous char with high yield, CO 2 capture capacity and CO 2 /CH 4 selectivity. The presence of the oxygen and nitrogen-containing functional groups in the optimum char help in the selective capture of CO 2 . The static CO 2 capture capacity of the optimum char was 1.98 mmol/g at atmospheric pressure and 25 °C (90 % CO 2 stream). The CSD (700−10−60) have capture capacity of 1.50 mmol/g (at a feed gas stream of 50 % CO 2 and adsorption temperature of 25 °C and 120 kPa) which is equivalent to Norit C and Calgon BPL. Hence, spruce sawdust can be used to produce efficient biochar for biogas upgrade (CO 2 capture) owing to high capture capacity and CO 2 /CH 4 selectivity (around 3) and easy regeneration of the biochar for 10 consecutive cycles. • The potential of spruce sawdust as a cheap and easily available biomass precursor for biogas upgrade to biomethane. • The CSD (700−10−60) showed a static CO 2 capture capacity of 1.98 mmol/g (highest for an unmodified char) at 25 °C. • The cyclic stability was very high for 10 consecutive cycles. • It has dynamic capture capacity of 1.50 mmol/g (50 % CO 2 stream) which is equivalent to Norit C and Calgon BPL at 25 °C. • The CO 2 /CH 4 selectivity of the char was 2.47 (lower concentration of CO 2 has higher selectivity 3.59). • The pore size was in the range of 0.4–0.55 nm which was crucial for CO 2 capture and selectivity. • Spruce sawdust can be used to produce efficient biochar for biogas upgrade owing to CO 2 /CH 4 selectivity around 3.