Recovery of renewable carbon resources from the household kitchen waste via char induced microwave pyrolysis

This study is focused on creating value addition to kitchen waste (KW) by converting it into valuable product resources via microwave pyrolysis. The effect of the following on product yields and energy efficiency were examined in this study: (i) microwave power (140–700 W), (ii) KW: susceptor ratio (20:0 to 20:20 (g/g)), and (iii) pyrolysis temperature (200–600 °C). The KW was pyrolyzed without the addition of a susceptor and char formed during pyrolysis acted as a susceptor and enhanced pyrolysis energy efficiency (78%). An increase in microwave power has significantly increased the heating rate from 4 to 85 °C/min, and KW has produced 73 wt% of bio-oil and gases even at low microwave power (140 W). An increase in pyrolysis temperature promoted thermal cracking of KW, which resulted in decreased char yields (64–27 wt%), and an increase in gas yields (12–45 wt%). Bio-oil contains a significant amount of phenolics (35–50%) and its selectivity varied significantly with the variables probed. The selectivity of furan derivatives has dramatically decreased from 45 to 20% with the increase in pyrolysis temperature. This work demonstrated the feasibility of valorization of kitchen waste into various value-added products.