Integrated biorefinery of orange wastes for xylooligosaccharides, pectin, and bioenergy production

More than 1 million tons of OPW (orange processing waste) is generated annually, which creates disposal problems and organic pollution. The exploitation of this waste includes the extraction of pectin and essential oils; however, this is not its most common destination. The efficiency of chemical treatments and enzymatic cocktails remains a bottleneck. One strategy to reduce costs is to design consecutive extractions and hydrolysis stages to yield more bioproducts from different feedstock fractions, reducing energy and material consumption. The present study assessed the performance of an OPW biorefinery to produce xylo-oligosaccharides, pectin, and bioenergy (heat and power). 50% of OPW dry weight is free sugars, which can be used for bioenergy production. Pectin and hemicellulose correspond to 40.5% and 14.8% of OPW dry weight, respectively. Here, the hydrothermal conditions for pectin and hemicellulose extraction and hydrolysis were optimized via CCRD. The optimized treatments yielded more than 60% pectin recovery and 80% purity. The consumed solvents were recovered by distillation and reverse osmosis. More than 90% of extracted hemicellulose is converted into xylo-oligosaccharides. Ultrafiltration and PBA column equipped with dextran resin remove the impurities, and a rotary drying concentrates the xylo-oligosaccharides to achieve 98.84% purity. The proposed biorefinery presented an efficient performance for ethanol and water recovery, and self-sufficiency for standard power usage, providing 14.13% of savings related to steam costs. The mass and energy calculations considered an OPW input of 10 tons per batch, from which it is possible to obtain 825 kg of XOS and 2.9 tons of pectin. The overall net unit production cost obtained from the analyzed scenarios and conditions was $3.67/kg of products (pectin and XOS), while the market prices are $15/kg pectin and $40/kg xylo-oligosaccharides. The proposed biorefinery showed low environmental impacts, easy return of investment and high purity of final products.