Co-pyrolysis of municipal solid waste and rice husk gasification tar to prepare biochar: An optimization study using response surface methodology

Abstract

Organic household waste and tar constitute the typical municipal solid waste (MSW) and biomass gasification liquid waste, respectively. In this study, biochar was prepared by co-pyrolysis of simulated MSW samples and rice husk gasification tar as experimental materials. The effects of three factors of co-pyrolysis, namely, pyrolysis temperature, residence time, and tar percentage on the biochar yield and quality were systematically evaluated by response surface methodology. The results reveal that the experimental mass yield, fixed carbon content, and higher heating value (HHV) of biochar increased by 2.06 %, 3.3 %, and 1.08 MJ kg−1, respectively, compared to the theoretical values under the optimized conditions of co-pyrolysis (600 °C, 17.5 min, and an MSW/tar mass ratio of 1:1). Thus, the synergistic effects occurred during the co-pyrolysis of MSW and tar. The three factors differently affected the properties of biochar. In general, the influence degree among three factors on biochar yield is in the following order: tar percentage > pyrolysis temperature > residence time. Among the three factors, the tar percentage showed the greatest influence on the HHV of biochar, while the pyrolysis temperature played a major role in deciding the fixed carbon content of biochar. The fitting equations were established for biochar and the three factors of co-pyrolysis, which provide data basis for effective use of MSW and tar. Finally, the experimental optimization conditions for biochar to reach the maximum yield, maximum carbon content, and maximum HHV were recommended.