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 R-2 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.