Hydrothermal liquefaction of fresh lemon-peel: Parameter optimisation and product chemistry

Abstract

Large amounts of food wastes, such as fruit peels, are released into the environment without proper treatment every year. Fruit peels are also a potential bio-resource that can be converted into useful chemicals. Due to the high moisture content of the peels, hydrothermal liquefaction was introduced to convert the fresh lemon-peel to biocrude oil in this study. The optimisation based on the response surface methodology was applied to parameters including temperature, reaction time and feedstock concentration. The highest oil yield around 18 wt% was achieved under the optimised settings of 336 °C, 50 min, and 9.6 wt% feedstock loading. GC-MS identified a large number of ketones in the biocrude, while few fatty acids and N & O containing compounds compared with that from microalgae. A higher percentage of the biocrude can be distilled compared with the microalgae oil, indicating more volatiles within the lemon-peel liquefied oil.