The study of properties and nutrient determination of hydrogel made of soybean meal (okara) using microwave-assisted heating

Recent Advances in Superabsorbent Hydrogels Derived from Agro Waste Materials for Sustainable Agriculture: A Review

Superabsorbent hydrogels made from agro waste materials have the potential to promote sustainable agriculture and environmental sustainability. These hydrogels not only help reduce water consumption and increase crop yields but also contribute to minimizing waste and lowering greenhouse gas emissions. Recent research on superabsorbent hydrogels derived from agro wastes has focused on the preparation of hydrogels based on natural polymers isolated from agro wastes, such as cellulose, hemicellulose, and lignin. This review provides an in-depth examination of hydrogels developed from raw agro waste materials and natural polymers extracted from agro wastes, highlighting that these studies start with raw wastes as the main materials. The utilization strategies for specific types of agro wastes are comprehensively described. This review outlines different methods utilized in the production of these hydrogels, including physical cross-linking techniques such as dissolution-regeneration and freeze-thawing, as well as chemical cross-linking methods involving various cross-linking agents and graft polymerization techniques such as free radical polymerization, microwave-assisted polymerization, and γ radiation graft polymerization. Specifically, this review explores the applications of agro waste-based superabsorbent hydrogels in enhancing soil properties such as water retention and slow-release of fertilizers for sustainable agriculture.

Evaluating the potential of okara-derived black soldier fly larval frass as a soil amendment

Bioconversion of organic waste by the black soldier fly (BSF) larva yields a by-product commonly known as 'frass'. Although BSF larval frass has often been marketed as a biofertilizer, few studies have evaluated this claim. In this study, BSF larvae reared on a pure okara diet achieved an 85% waste reduction in the fresh weight of the okara. Subsequently, the frass was mixed with soil at concentrations of 10, 20, and 30% (vol/vol), and used to cultivate lettuce plants. At 10% concentration, the lettuce plants had biomasses comparable to those of the controls. Higher frass concentrations stunted the growth of the lettuce, likely because of the low C:N ratio of larval frass resulting from the rapid mineralization of nutrients. Larval frass was also found to be able to provide sufficient nutrients for lettuce growth as fertilizer application was only necessary after the first growth cycle, suggesting its suitability as a soil amendment. Analyses of the microbial community of all the growing media showed that the growth medium treatments with BSF larval frass tended to have a lower number of microbial species than the controls. Inherently higher micronutrient levels present in the frass resulted in the growth of lettuce plants. More importantly, the microbial analysis revealed that common foodborne pathogens were absent in the BSF larval frass and elemental analysis also indicated no heavy metal pollutants present. Overall, BSF larval frass was found to be a suitable soil amendment and more in-depth studies could facilitate its sensible use in agriculture.