Co-pyrolysis of starch-rich food with ash-rich vegetables: Importance of inorganics in shaping pyrolysis reaction network and kinetics

Abstract

Vegetables tend to have higher content of inorganics and might involve in co-pyrolysis and impact characteristics of pyrolytic products. This was investigated by co-pyrolysis of lettuce or spinach with noodles at 600 °C. The results showed that the inorganics and/or the volatiles from lettuce/spinach interacted with noodles-derived organics, enhancing gasification, which produced more gases while diminished biochar formation. The inorganics in lettuce or spinach also catalyzed cracking of themselves to form more organics with π-conjugated structure in bio-oil. Moreover, the activation energy (Ea) in the pyrolysis of noodles or nascent biochar of higher aromatic nature was much higher than that in pyrolysis of spinach or lettuce. However, exposure of more inorganics from vegetable-derived biochar, at only high feedstock conversion (>20 %), significantly involved in the pyrolysis, reducing Ea in the co-pyrolysis. The co-pyrolysis enhanced combustion performances and also densification of biochar structures with lowered environmental impacts.