The IMO have not yet favoured any particular means of applying constraints on GHG emissions. They have proposed two Indices to help to demonstrate that shipping is moving towards a more efficient operating regime: the Energy Efficient Design Index (EEDI), and the Energy Efficient Operating Index (EEOI). The EEDI will apply to future new designs of ship, and hence will take many years to have any effect.
The EEOI will require a ‘baseline’ level of current operating efficiency to be produced before any improvements can be measured against it; the construction of this baseline is not agreed and will also take some time to achieve from accurate and reliable data provided by willing owners/operators/flag states. The IMO is also proposing a Ship Energy Efficiency Management Plan (SEEMP) for each new and in service vessel.
The EEDI will measure the assumed energy efficiency of a design when operated in its design condition (speed, full payload) in grams of CO2 per capacity mile [gm/Tonne mile]. The EEOI has been under trial since 2005 to measure the actual energy efficiency of a vessel on a voyage, ie actual fuel used to carry the actual payload, and is measured in the same units as the EEDI. The EEOI can also be used to gauge the effectiveness of any energy efficiency improvement measures which have been implemented – as long as the operating conditions are comparable. The SEEMP will provide guidance on best practice for each specific vessel in terms of operating parameters, voyage planning/routing, speed/power optimisation, cargo handling and energy management.
