Extraction and Characterization of Fluvic Acids from Agro-Industrial Wastes: An Innovative Waste Management Strategy

Agro-industrial wastes (AIW) can be converted into valuable products such as fulvic acid (FA) and nutrient sources. The study was carried out with a sequential alkaline and acidic method for the extraction and characterization of FA from banana waste compost (BWC), farmyard manure (FYM), and sugarcane press mud (SPM), in this context to record the physiochemical properties of organic waste, fluvic acid recovery percentage, proximate analysis of fluvic acid, elemental contents of FA, and functional groups were evaluated. The results revealed that all three agro-industrial wastes showed significant physicochemical properties. Moreover, the highest FA recovery (%) was obtained from BWC (3.70%), followed by FYM (3.56%), and the lowest from SPM (2.45%). The highest moisture content, volatile matter, and Fixed carbon were observed in BWC waste, followed by FYM, and the lowest was observed in SPM. The elemental composition exhibited that the FA derived from BWC had the highest C content (46.1%), followed by FYM (44.7%) and SPM (44.3%). The highest hydrogen (H) in FA from BWC was (4.30%), compared to SPM (4.13%). The highest nitrogen (N) was recorded from BWC and SPM (3.50%), and the lowest was in FYM (3.40%) derived from FA. The highest oxygen (O) was observed in SPM (47.20%), followed by FYM (46.6), and the least in BWC-derived FA (45.2). In addition, the phosphorus (P) content was higher in FA extracted from SPM (0.08%) and lower in FYM (0.07%). The potassium content was highest in FA extracted from FYM (11.6%) and lowest in SPM (9.6%). The maximum sulphur (S), content was recorded in FA extracted from BWC, followed by FYM and SPM. Functional group analysis revealed that the highest total acidity, 11.33 meq g-1, carboxyl groups 9.91meq g-1, and phenolic group (11.81 meq g-1) were recorded in FA extracted from BWC. The lowest total acidity, 10.97 meq g-1, the lowest carboxyl groups (9.32 meq g-1), and the lowest phenolic group (1.66 meq g-1) were recorded in BWC. The highest E4/E6 ratio (7.103) was observed in FA from BWC, and the lowest E4/E6 ratio (6.9) was recorded in FA isolated from SPM. It is concluded that the FA extracted from BWC exhibited superior structural maturity, aromaticity, and stability compared to the other two sources; hence, it may be more effective as a soil conditioner.