Oilcake Bioconversion into Enriched Micronutrient and Secondary Nutrient: Optimization and Evaluation

This study investigates the use of four different oil cakes, a biodegradable waste stream, for creating secondary and micronutrient-enriched fertilizers via biosorption, focusing on zinc. iron, copper, magnesium and calcium to verify the appropriateness of oil cake as support material for nutrient release patterns to crops on slow release basis. Optimal biosorption conditions were established, highlighting a pH of 3.5, a feed rate of 4.5 ml/min, and a biomass ratio of 4.5 g. Compared to commercial fertiliser, it showed decreased Ca+ 2, Mg+ 2, Zn+ 2, Fe+ 2/+3, and Cu+ 2 release, indicating its low release behaviour. The leaching capability of the mineral nutrients was highest for Cu+ 2, followed by Ca+ 2 > Mg+ 2 > Fe+ 2/+3 > Zn+ 2. Furthermore, for the delayed release of Ca+ 2, Mg+ 2, Fe+ 2/+3, and Cu+ 2 nutrients, the karanj cake had the best nutrient retention/sorption capability among the four different types of oilcakes, followed by the neem cake, castor cake, and mustard cake. The Zn+ 2 nutrient retention/sorption capacity of neem cake was remarkable, however, and it was followed by mustard, castor, and karanj cakes. Consequently, the designed slow release fertilizer's secondary and micronutrient nutrient release pattern was likewise altered by oilcake kinds. Therefore, oilcake-based slow release fertiliser has a higher potential to improve water retention, reduce nutrient leaching, and increase plant nutrient and water use efficiency. This development in the production of fertilisers enhanced with micronutrients and secondary nutrients provides important insights into sustainable agriculture and effective waste management, highlighting oil cakes as a workable option for nutrient recycling.