The massive influx of Sargassum along Caribbean coastlines presents both an environmental challenge and an opportunity for biomass valorization. This study evaluated pretreatment consisting of washing and solar drying to adapt Sargassum biomass for thermochemical recovery. Biomass was collected from three coastal sites in the Mexican Caribbean, with an average morphotype composition of Sargassum natans III (88.3%), Sargassum fluitans I (10%), and Sargassum natans VIII (1.6%). Samples were divided into Control (untreated) and Wash-dry (pretreated) groups and analyzed through Fourier transform infrared (FTIR) spectroscopy, proximate analysis, and ultimate analysis. Statistical evaluation revealed that prior segregation by morphotype or morphological section does not significantly influence biomass composition or higher heating value (~14 MJ/kg), supporting large-scale processing strategies. FTIR spectra showed that both groups retained key functional groups such as hydroxyl, carbonyl, and polysaccharide-associated vibrations, indicating biochemical integrity. The intensity of the signals associated with marine salts and sand decreased in the Wash-dry sample, confirming effective removal of surface-bound inorganic matter. Proximate analysis revealed a reduction in both moisture content (from 57.9 to 18.1%) and fixed carbon content (from 3.5 to 0.9%). Volatile matter increased from 20.7 to 59.4%, enhancing the potential of Sargassum for oil and gas production. Ultimate analysis revealed statistically similar C, H, N, S, and O contents after pretreatment, confirming preservation of the internal chemical structure. These findings demonstrate that the Wash-dry protocol is a selective and non-destructive strategy that enhances Sargassum biomass quality, potentially enabling a less energy-intensive pathway for its thermochemical valorization.
