Default Emission Factor

A default emission factor is a standardized, conservative value an operator uses when fuel-specific measured data are unavailable or unverified. The IMO Life Cycle GHG Intensity Guidelines provide default well-to-wake factors per fuel pathway and allow an actual factor only when a third party verifies and certifies it. Defaults carry built-in conservatism, so a producer of a genuinely lower-carbon fuel has an incentive to certify an actual value rather than accept the default. Using the default keeps the calculation auditable and comparable across the fleet, at the cost of not crediting below-default performance.