Gasification of fruit wastes and agro-food residues in supercritical water

Considerable amounts of fruit wastes and agro-food residues are generated worldwide as a result of food processing. Converting the bioactive components (e.g., carbohydrates, lipids, fats, cellulose, hemicellulose and lignin) in food wastes to biofuels is a potential remediation approach. This study highlights the characterization and hydrothermal conversion of several fruit wastes and agro-food residues such as aloe vera rind, banana peel, coconut shell, lemon peel, orange peel, pineapple peel and sugarcane bagasse to hydrogen-rich syngas through supercritical water gasification. The agro-food wastes were gasified in supercritical water to study the impacts of temperature (400-600 degrees C), biomass-to-water ratio (1:5 and 1:10) and reaction time (15-45 min) at a pressure range of 23-25 MPa. The catalytic effects of NaOH and K2CO3 were also investigated to maximize the hydrogen yields and selectivity. The elevated temperature (600 degrees C), longer reaction time (45 min) and lower feed concentration (1:10 biomass-to-water ratio) were optimal for higher hydrogen yield (0.91 mmol/g) and total gas yield (5.5 mmol/g) from orange peel. However, coconut shell with 2 wt% K2CO3 at 600 degrees C and 1:10 biomass-to-water ratio for 45 min revealed superior hydrogen yield (4.8 mmol/g), hydrogen selectivity (45.8%) and total gas yield (15 mmol/g) with enhanced lower heating value of the gas product (1595 kJ/Nm(3)). The overall findings suggest that supercritical water gasification of fruit wastes and agro-food residues could serve as an effective organic waste management technology with regards to bioenergy production. (C) 2015 Elsevier Ltd. All rights reserved.