Tank-to-Wake

Tank-to-wake is the onboard half of the life-cycle boundary, covering emissions from burning the fuel in the ship’s engines and boilers plus any unburned slip. It is the default boundary for the EEDI, EEXI, and CII, which count only CO2 from combustion using a fuel carbon factor Cf. For carbon-free fuels such as ammonia and hydrogen the tank-to-wake CO2 is near zero, which is why the IMO and FuelEU shifted to the wider well-to-wake basis to capture upstream and slip emissions including methane and N2O.