Valorization of waste tea bags via CO2-assisted pyrolysis

Abstract

Pyrolysis is an effective method for both waste valorization and treatment. Herein, carbon dioxide-assisted pyrolysis was conducted for the valorization and treatment of everyday waste, namely used tea bags. The effects of pyrolysis temperature and medium (N2 and CO2) on the composition and yield of the pyrolytic products were explored. The changes in the pyrolysis temperature and pyrolysis medium affected the compositions and yields of pyrolytic products. More non-condensable gases and less char were produced as the temperature increased. CO2 increased the yield of pyrolytic gases, particularly hydrogen and also prevented the formation of environmental pollutants such as phenolic compounds, benzene derivatives, and polycyclic aromatic hydrocarbons. The char produced from waste tea bags via CO2-assisted pyrolysis had a higher heating value (26.8 MJ kg−1) comparable to that of coal. This study demonstrates the effectiveness of CO2 utilization in pyrolysis for valorization of everyday waste.