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Abstract

The global demand for sustainable energy solutions has intensified interest in alternative biomass feedstocks. This research investigates the valorization potential of vegetable crop foliage, from tomato, eggplant, cucumber, summer squash, soybean, and corn, as non-woody lignocellulosic residues for bioenergy applications. A systematic approach was adopted to examine the physical, thermal, and mechanical behavior of these biomasses across grinding, characterization, and pelletization stages. Post-harvest processing revealed significant variability in grindability and flow behavior. The Net Specific Grinding Energy Consumption (NSGEC) ranged from 5.1 kWh/t for summer squash foliage to 31.7 kWh/t for soybean foliage. Compositional analysis indicated strong correlations between lignin, C/O ratio, and GCV (Gross Calorific Value), with soybean and corn foliage showing the highest GCV (~17.5 MJ/kg, db). Thermogravimetric analysis under oxidative and inert atmospheres demonstrated distinct thermal degradation profiles. Soybean and corn foliage exhibited superior combustion reactivity and higher pyrolysis indices. Kinetic modeling using the Coats–Redfern method quantified activation energies and decomposition stages across hemicellulose, cellulose, and lignin zones. Pelletization trials were conducted using both a laboratory single-pellet press and a batch-scale commercial flat die mill. Results highlighted cucumber and summer squash foliage as optimal feedstocks, achieving single pellet densities 1.48 g/cm³ to 1.51 g/cm³. Batch-scale trials showed that cucumber and summer squash foliage again led performance with high bulk density (665 – 691 kg/m³) and durability (96.6 – 97.9 %) at low pelletization energy (18.7 – 21.8 kWh/t), while soybean residue demanded the most energy (49.6 kWh/t) and showed the lowest bulk durability (92.3 %) by tumbler durability tester and bulk density (587 kg/m³). Statistical models were developed to link compositional properties with pellet quality metrics, enabling prediction of bulk pellet durability (R² = 0.936) and bulk pellet density (R² = 0.861) for scale-up and process-screening purposes. The findings demonstrate that vegetable foliage, particularly cucumber, summer squash, and soybean, can serve as promising feedstock for bioenergy systems.