Cross-interaction of volatiles in co-pyrolysis of spinach and noodles and their impacts on properties of pyrolytic products and pyrolysis kinetics

Noodles and spinach are common staple food and vegetables in kitchen waste and they have distinct compositions. Their co-pyrolysis might induce some cross-interactions in terms of volatiles-volatiles or volatiles-biochar, the influence of which on properties of pyrolytic products was studied herein in co-pyrolysis of noodles and spinach at 600 °C. The results indicated that the abundance of inorganics (contained elements such as K, Ca, Na and Cl) in spinach promoted cracking of volatiles, producing more gases at the expense of bio-oil. The inorganics from spinach also promoted further cracking of volatiles from the noodles in the co-pyrolysis, diminishing production of bio-oil. Additionally, cross-polymerization of the volatiles also occurred in the co-pyrolysis, generating oxygen-rich biochar with lower thermal stability but a much higher hydrophilicity. The in-situ Diffuse Reflection Infrared Fourier Transform Spectra (DRIFTS) measurement showed that the inorganics in spinach catalyzed the cracking of aliphatic structures in biochar and hindered aromatization process, leading to the especially low C content of biochar. The kinetic study showed that the co-pyrolysis of noodles and spinach reduced activation energy for conversion of the feedstock, originating from the cross-interactions among the volatiles and between the volatiles and biochar of different origin.