Solvothermal co‐liquefaction of wastes from Citrus limetta fruit processing

Abstract

BACKGROUND: Liquefaction of biomass has an advantage over other thermochemical processes of conversion and its co-liquefaction aims to overcome the restrictions and limitations imposed upon single feedstock liquefaction. Valorization of Citrus limetta peel and pulp wastes by their co-liquefaction in a hydrogen-donor solvent such as methanol was chosen as an objective herein for efficient conversion of raw materials to obtain better quality biocrude.RESULTS: A maximum biocrude yield of 11.25 wt. % was obtained from solvothermal co-liquefaction of Citrus limetta peel and pulp biomasses at 260 °C temperature, with 30 min residence time, at three different ratios of biomass to solvent (1:2, 1:3 and 1:4). This was higher than the biocrude yield from liquefaction of individual C. limetta pulp biomass as well as other studies on similar citrus fruit wastes. The higher heating value (HHV) of biocrude was raised to 25.72 MJ kg −1 at 1:3 biomass:solvent ratio by co-liquefaction, showing its synergy over individual C. limetta peel biocrude. The presence of esters, ketones, alcohols, hydrocarbons and fatty acids in the biocrude product were found from Gas Chromatography-Mass Spectrometry (GC-MS) results. The biochar obtained was mesoporous in nature and could be employed for adsorption in bioremediation of water and soil.CONCLUSION: Co-liquefaction of homogeneous lignocellulosic biomasses have the ability to boost production and the quality of the biocrude and biochar attained in comparison to products of individual liquefaction. Future studies on upgrading the quality of products are required.