SFC-Based Harmonisation of Entec and Trozzi–Vaccaro Ship CO2 Emission Factors: Vessel-Category-Specific SFC Equivalence Thresholds

This study examines how published cruising CO2 factors from Entec UK Ltd. and Trozzi–Vaccaro can be compared on a common engine-energy basis. Multiplication of the Trozzi–Vaccaro factor of 3.2 g CO2/g fuel by specific fuel consumption (SFC) gives an energy-based factor. Equating this with six Entec category factors yields implied SFC thresholds of 195.94–215.63 g fuel/kWh. A grid of 42 deterministic comparisons illustrates this algebraic relationship; it is not independent validation. The contribution is a diagnostic procedure that links factor differences to conditional inventory consequences and tests whether their ordering survives bounded input changes. A matched-energy container example at an assumed SFC of 190 g/kWh produces 63.5 versus 60.8 t CO2 per 100,000 kWh. Allowing SFC to vary by ±5% reverses the factor ordering within that example. Independent ±1% changes in the two category factors also make the oil-tanker and Ro-Pax threshold intervals overlap. The thresholds therefore indicate numerical agreement under stated assumptions, rather than physical equivalence, measured vessel efficiency or superior method accuracy. Operational use requires compatible fuel, engine-work and system boundaries, together with verified SFC data.