Utilization of Biomass Waste from Citrus Fruits for the Production of Essential Oils

The valorization of citrus peel residues represents an important strategy for promoting circular bioeconomy approaches in the agri-food sector. This study evaluated the biorefinery potential of ten citrus varieties cultivated in Bolívar Province, Ecuador, including mandarin (Citrus reticulata criolla, Citrus nobilis Loureiro, Citrus tangerina, Citrus unshiu), lemon (Citrus aurantifolia Swingle, Citrus limonia, Citrus limonum, Citrus latifolia), and grapefruit (Citrus paradisi, Citrus paradisi Macfad.), focusing on the extraction and characterization of essential oils from peel biomass. The residual biomass was characterized through proximate and elemental analyses to determine its physicochemical properties, and essential oils were extracted under two maceration times (8 and 12 h) to evaluate the influence of extraction conditions on yield. Chemical composition was determined by gas chromatography-mass spectrometry (GC-MS). The results revealed significant variability among varieties in moisture, ash, and volatile solids content. Citrus nobilis Loureiro showed the highest extraction yield, while grapefruit varieties exhibited the greatest increase in yield with extended maceration time. Limonene was identified as the predominant compound in all essential oils, reaching concentrations above 90% in grapefruit samples, and significant intervarietal differences in monoterpene profiles were observed. Extraction kinetics were evaluated using seven mathematical models, among which the Monod model showed the best fit to the experimental data (R² > 0.99), demonstrating strong predictive capability. These findings highlight the potential of citrus peel residues as sustainable sources of high-value essential oils and provide a quantitative framework for optimizing extraction processes within citrus biorefinery systems.