Valorization of Citrus maxima Peel Waste Using Different Drying Methods: Phytochemical Profiling for Eco-Friendly Natural Fertilizer Development for Plant Growth

Abstract

This study aims to optimize the utilization of Citrus maxima peel waste into an organic fertilizer rich in flavonoids and pectin by evaluating various drying methods. This optimization is undertaken as an effort to achieve sustainable agricultural waste management while creating value-added goods that enhance plant growth. The research treatments included of oven and sun-dried and three different types of solvents (n-hexane, ethanol, and ethyl acetate) with four replications. Pectin is extracted through acid heating and measured gravimetrically as calcium pectate. Macronutrients (N, K) is frequently analyzed using the Kjeldahl and Flame Photometry methods, whereas volatile substances are identified using GC-MS. The results show that sun drying maintains the highest pectin content (15.28%), but oven drying maintains the highest flavonoid content (237.25 mg CAE/g). Total Nitrogen (0.84%) and K2O (0.47%) content were higher in controlled oven-dried than in sun-dried samples. GC-MS analysis identified the compounds heneicosane, benzene, phenol, heptadecane, eicosane, and tetracosane as dominant when using non-polar n-hexane and ethyl acetate solvents. In contrast, ethanol solvents contained the dominant compounds is a-D-Mannofuranoside (mannofuranoside), hydroxymethylfurfural, and fatty acid. These compounds contribute to soil biological activity. The high nitrogen and potassium content in all analyzed samples confirms the suitability of Citrus maxima peel as an organic input for the development of environmentally friendly fertilizers. The integration of pectin as a nutrient carrier and its nitrogen & K2O profile, flavonoids, and rich metabolite contents indicate that the utilization of Citrus maxima peel has great potential and could serve as a sustainable alternative for the development of eco-friendly bio-based fertilizers to enhance plant growth, taking into considering the research findings that solvent polarity and drying conditions play a decisive role in shaping the metabolite profile of Citrus maxima peel extracts. Keywords: Citrus maxima, flavonoid, pectin, drying method, nutrient, GC-MS .