Carbon capture of biochar produced by microwave co-pyrolysis: adsorption capacity, kinetics, and benefits

Microwave co-pyrolysis of sewage sludge and leucaena wood was conducted to produce biochar as an adsorbent for CO₂ capture. Both microwave power level and blending ratio were crucial factors affecting the CO₂ adsorption capacity of biochar. At a power level of 150 W, the biochar produced by microwave co-pyrolysis of 25% sewage sludge and 75% leucaena wood possessed the highest CO₂ adsorption capacity. When the biochar was produced at 100 W, its CO₂ adsorption capacity was higher than predicted. Based on the proximate and elemental compositions of biochar, two equations were obtained to predict CO₂ adsorption capacity. The proximate composition of biochar can provide more precise prediction of CO₂ adsorption capacity than elemental composition according to the higher R² value provided. The blending ratio of 50% would be most appropriate to produce the biochar with acceptable reduction in CO₂ adsorption capacity and loss of quantity. The pseudo-second-order model would be most suitable for simulating the kinetic of CO₂ adsorption. The biochar produced from 1 metric tonne of sewage sludge and leucaena wood can offset carbon tax by 83 US dollars. Based on experimental results and findings, microwave co-pyrolysis should be a feasible technique to produce biochar possessing high CO₂ adsorption capacity.