Recycling tempura powder debris derived from the fried food industry as a binder for 3-dimensional biodegradable composites: A novel circular economy alternative to low-performance plastics

Although the collection and recycling of used cooking oils have been well-established, tempura powder debris discarded from the frying process has received little attention. Here, in collaboration with a local company that collects used cooking oil, we estimated that approximately 881,000,000 kg of tempura powder debris is discarded annually in South Korea. The debris was found to contain approximately 60 % of oils that can be extracted through a squeezing process. The resulting cake was proven to be beneficial for the fabrication of 3-dimensional biocomposites with waste biomass powders (e.g., used cardboard and coffee powders and rice straw powder), wherein the polysaccharides from the debris likely serve as a binder. Various complex structures were readily fabricated using heat-drying (90 ℃ for 30 minutes and then at 120 ℃ for 30 minutes for a dish and 130 ℃ for 24 hours for other shapes) and exhibited a compressive strength of 2500 kPa and a thermal conductivity of 0.089 W/(m·K). The overall composite shape was maintained under water soaking, while the compressive strengths were reduced by 40 % under a high humidity. Furthermore, strong sorption for toxic compounds, excellent biodegradability, low cytotoxicity, good-odor emission, and enhanced maize germination rates with bed soils were displayed by using the composites. The performance and function comparisons with commercial expanded polystyrene suggest that using the composites could be multi-beneficial. In conclusion, tempura powder debris from the fried food sector could become a significant bulk waste source, supporting the development of circular economy such as a low-performance plastic alternative.