Energy potential of Cacay ( Caryodendron orinocense Karst) shell biomass and its biochar: a complete characterization

Rising Cacay oil demand could generate 4,018 tons of shells annually by 2035 in Meta, Colombia, with 28.5 TJ/year energy potential (>8% of 2023 industrial use). This study characterizes shells and biochar for waste valorization, showing 72.3% sphericity, 68.4% circularity, 80.9% porosity, and 26.41 cm2 surface area. Biochar was produced by slow pyrolysis at 500 °C, followed by NaOH and KOH activation, and chemically characterized through proximate analysis (moisture, volatile matter, ash, and fixed carbon content), ultimate analysis (C, H, N, S, and O elemental composition). Smaller particles and pre-activation increased biochar yield (37.25% fine, 35.82% coarse). KOH activation lowered heating value: 30 MJ/kg vs 19 MJ/kg for raw shells. Raw shells are suitable for fast-ignition bioenergy applications, such as rapid combustion for quick energy release, but less suitable for sustained heat generation due to their faster burnout rate. Untreated or NaOH-activated biochar is an efficient biofuel due to high heating value and ash control. KOH-activated biochar is ideal as a soil amendment, offering stability, low ash, and minimal salinity risk, while meeting carbon sequestration standards. Using Cacay shell waste delivers bioenergy and agricultural benefits, transforming waste into economic and environmental value.