Valorization of Food Waste through Controlled Oxidation: A Case Study on Densification of Onion Waste

Abstract Around 20% of the fruits and vegetables produced globally are lost between harvest and retail owing to infrastructure and logistics challenges. There are no technologies available to utilize this waste comprehensively, which amounts to billions in economic losses annually. While methods are available for extraction of bio-active compounds, the technologies to harness fibers and sugars, which are the major components of the waste, are not reported. This work reports a new technique for valorization of waste onion, as it consists of carbohydrates and fibers and represents the typical composition of food and vegetable waste. The controlled oxidation of onion waste under ambient conditions led to decomposition of 90% of the sugars, which resulted in crosslinking of the fibers to create a strong and rigid densified matrix of the fibers. The densified matrix had a compression strength of 101.7 MPa and remained stable up to 100 °C. Such densified materials can be used for packaging applications or as one of the components of vegan leather. The onion waste and densified material were characterized using FTIR, XRD, SEM imaging, elemental analysis, and compression testing to identify the structure–property relationship.