The use of agricultural waste to produce value-added products has aided in managing waste management difficulties while somehow addressing cost-effectiveness concerns. The current research addresses environmental issues and helps to promote ecologically friendly agricultural practices in Punjab, Pakistan, by using banana and grapefruit peel biomass, converting them to biochar by pyrolysis, and further studying their efficacy as sustainable fertilizer. The return of biochar obtained from agricultural waste to the agricultural field is a sustainable approach for increasing the yield of crop output while reducing the environmental impact of traditional fertilizers. Furthermore, it improves soil condition by regulating pH, water holding capacity, soil organic carbon, and soil ion exchange potential. Zinc oxide loaded biochar was synthesized from banana and grapefruit peel biochar. Pyrolysis was done at 400-500ºC as part of the process. Co-precipitation method was used to impregnate ZnO nanoparticles in biochar and proved an efficient and dependable approach. In-situ loading was done. XRD, elemental analysis of carbon, hydrogen, nitrogen, and sulfur (CHNS), FT-IR, and TGA methods were used to characterize synthesized materials. The adsorption ability of ZnO loaded biochar, soil, and raw biochar was investigated using several physical tests such as swelling ratio, water retention, absorbance, and equilibrium water content percentage. As a result, the adsorption capacity of ZnO loaded biochar was shown to be greater than that of raw biochar. Zinc loaded biochar was used as a fertilizer in Cicer arietinum (gram). Synthesized nano-fertilizers exhibit enhanced prolonged nutrient release, plant growth, and improved soil fertility, providing an environmentally friendly alternative to traditional fertilizers by reducing nutrient loss.