Abstract:

The results illustrate the importance of understanding the reason for the life-cycle carbon accounting of fuels. For one, fuels that have zero tank-to-wake or direct emissions can have substantial upstream production emissions that are not counted when assessing only tank-to-wake emissions. Additionally, while indirect effects are uncertain and difficult to estimate, they might be large enough to greatly affect the estimated GHG savings of some fuel pathways, and assuming a value of zero on the basis of uncertainty is not necessarily a neutral decision. To avoid the adoption of high-emitting fuels in an effort to decarbonize maritime transportation, the IMO can adopt full life-cycle well-to-wake GHG accounting for policies related to fuel operational use such as the Carbon Intensity Indicator and potential future policies like the GHG Fuel Standard. Such accounting would be consistent with other major fuels policies that assess the indirect emissions attributable to fuels.