Gasification biochar from biowaste (food waste and wood waste) for effective CO2 adsorption

Biochar is newly proposed as an innovative and cost-effective material to capture CO2. In this study, biochar was produced from feedstock mixtures of food waste and wood waste (i.e., 20%:80% WFW20, 30%:70% WFW30 and 40%:60% WFW40) by gasification. The two biochar adsorbents containing the highest percentage of food waste, i.e., WFW40-K and WFW40-KC, were activated by KOH and KOH + CO2, respectively. The biochar adsorbents were then tested for CO2 adsorption at room temperature of 25 °C by using a volumetric sorption analyzer. The WFW20 showed the highest CO2 adsorption capacity, while higher percentage of food waste in the feedstock was unfavorable for the CO2 adsorption. The presence of N and S on the biochar surface was the primary contributor to the high CO2 uptake on WFW20. The development of micropores by KOH activation significantly increased the CO2 adsorption on WFW40-K, but KOH + CO2 activation could not further increase the development of micropores and subsequent CO2 adsorption. Moreover, WFW40-K showed >99% recyclability during 10 consecutive adsorption-desorption cycles. The biochars derived from biowaste (food waste and wood waste) could be effective adsorbents for CO2 capture by providing green solution for food waste recycling.