<p>Sodium alginate is a naturally occurring anionic polysaccharide derived from brown algae and is widely employed in food, pharmaceutical, biomedical, and environmental applications. Its combination with magnetite (Fe₃O₄) nanoparticles produces composite suspensions used in adsorption, enzyme immobilization, drug delivery, and catalysis, yet the rheology of their precursor suspensions remains poorly characterized despite its importance for processing and end-use performance. This study integrates rotational rheometry, constitutive modeling, machine learning, and a gate-to-gate carbon footprint assessment of the Alg/Fe₃O₄ suspension system. Suspensions at 0.25-1.00% (w/v) Fe₃O₄ loading were analyzed between 25 and 40&#xa0;°C. Apparent viscosity increased with loading from 4.52 ± 1.24 to 10.07 ± 1.50 cP at 25&#xa0;°C, and all suspensions exhibited shear-thinning behavior, with power-law flow indices below unity (<i>n</i> &lt; 1). Among the power-law, Herschel-Bulkley, and Bingham models, Herschel-Bulkley provided the best fit, although the intercept stresses (1716–2551&#xa0;Pa) reflect fitting parameters rather than true yield stresses owing to high shear rates measurement window. Among eight regression algorithms tested, support vector regression achieved the highest accuracy for viscosity (R² = 0.998) and light gradient boosting machine for shear stress (R² = 0.979), with Fe₃O₄ loading and shear rate as the dominant features. The gate-to-gate carbon footprint, dominated by thermal processing of nanoparticles, ranged from 188 to 308&#xa0;g CO₂eq per gram of composite solid, with <i>Pyracantha coccinea</i> fruit extract providing an environmental advantage over conventional chemical coprecipitation. The integrated rheological, data-driven, and environmental analysis presented here provides a quantitative baseline for the design and processability assessment of Alg/Fe₃O₄ suspensions targeted for biomedical, environmental, and catalytic applications.</p> Graphical abstract <p></p>