Biochar addition can upgrade fuel chemistry while impairing densification and handling. An experimental campaign was conducted to quantify these process-performance trade-offs for pellets produced from buckwheat hulls containing 10–30 wt.% wood-derived biochar (BC) and 20 wt.% molasses on a 6 mm flat-die press. Three blend variants (BC10, BC20 and BC30) were produced, and the fuel and pellet properties were determined in triplicate. Electrical power was logged at 0.002 s to determine specific energy consumption (SEC), and a net energy metric (SECnet), defined as the higher heating value (HHV) reduced by the pelletization energy, was used to evaluate the energy retained in the product per kilogram of pellets. Fuel properties (HHV and lower heating value, LHV), particle and bulk density, mechanical durability, and combustion behaviour (thermogravimetric analysis, TGA/DTG, 25–850 °C, synthetic air) were measured under steady-state conditions. Biochar increased gravimetric energy density (LHV 15.82 → 17.52 MJ/kg; HHV 17.28 → 18.96 MJ/kg) and raised SECnet by 9.3%. Thus, calorific gains outweighed the densification penalty, despite a significant rise in SEC (BC10 < BC20 < BC30, p < 0.001). In contrast, bulk density decreased (390 → 365 kg/m3) and mechanical durability declined (74.2 → 45.9%), so volumetric energy density (LHV×bulk density) improved only modestly (+3.6%). TGA/DTG profiles remained biomass-like but shifted to slightly higher temperatures with higher ash residue. The results indicate that SECnet is a useful pellet-scale energy indicator and show that biochar-enriched pellets remain net-energy positive across 10–30 wt.% char, however, logistics and handling are constrained by reduced bulk density and durability. The experimental trends indicate a pragmatic operating window of 10-20 wt.% biochar, within which energy gains are retained while process loads and mechanical penalties remain manageable; beyond this range, industrial deployment will require targeted optimisation e.g., steam conditioning, die-temperature control, and stronger/low-cost binders.