DNV – helping understand CII

Feb 07 2022

Tankers will need a Carbon Intensity Indicator (CII) below a certain limit, under regulations taking effect in January 2023. DNV ran a webinar to explain how this scheme works.

The Carbon Intensity Indicator (CII) requirement from IMO is somewhat confusing, since when we also have the EEDI / EEXI requirements, you may wonder why the industry needs to be regulated twice.


The difference is that EEDI / EEXI focus only on the ship itself – how much fuel is needed to move the cargo in standard speeds and operating conditions. CII is looking at the actual emissions you make. So if you improve your weather routing, or reduce speed, you reduce CII but not the EEDI / EEXI.


To add to the complication, you can improve your EEDI / EEXI by setting a maximum speed for the vessel, since this is seen to be changing the ship itself. But your CII will only change if you actually change speed.


If you were never operating at this high speed which is now restricted, this restriction doesn’t change the emissions, and so your CII does not change.


The word ‘intensity’ is used because we are talking about emissions per tonne mile. If it was about absolute emissions, countries would complain it denies them of the right to grow their maritime industries.


DNV held a webinar on Sept 16 to explain further.


So we can say that EEDI and EEXI sit on the technical side and CII sits on the operational side, said Tore Longva, Principal Consultant, DNV


The CII requirements apply to all cargo, ropax and cruise ships above 5000 gt. It does not cover offshore support vessels, other passenger ships, fishing vessels and other service vessels such as supply vessels, anchor handlers and construction vessels.


Cruise ships are defined as “a ship with overnight accommodation”. Ropax is defined as a “passenger ship with cargo space”. So a ship without either overnight accommodation or cargo space is not included.


CII does not distinguish on propulsion type or age, it looks purely at emissions per tonne of cargo carried per mile over the year.


It comes into force on January 2023. During the 2023 calendar year, ships need to gather data, and make a report in early 2024 for the calendar year.


The carbon intensity will be used to determine their score, with enforcement action if they get a D for 3 consecutive years, or a single E rating.


If this happens, the ship will need to show its flag authority its plan for getting a C. If a ship has a C or better rating, or an approved corrective action plan, it gets a “Statement of Compliance” which is valid for 1.5 years. Each ship will need to have this from 2024.


The emissions levels for the various scores have been defined up to 2026. The scheme will be reviewed by January 2026, with potential tightening from 2027, and perhaps also “strengthening the corrective actions”, i.e. making more serious consequences for failing ships.


Mr Longva expects IMO to finalise the guidelines for calculation of CII, including correction factors, by June 2022, the time of the MEPC 78 meeting.


Note that using biofuels will not reduce the carbon intensity using this equation, because it looks only at emissions from the vessel itself, known as tank to wake. It does not cover fuel lifecycle emissions, such as including CO2 absorbed when the plant is grown, or CO2 emitted in the processes of producing fossil fuels, which is known as well to wake.


“There is an intersessional working group addressing these guidelines,” Mr Longva added. “We see a lot of questions around applying biofuels.” But this is not expected to be reviewed until 2025.


Calculations and graphs

The CII is calculated as (fuel consumption x CO2 conversion factor) divided by (annual distance travelled x capacity). So it is g Co2 per deadweight tonnage mile.


The formula for CII was chosen because all of this data is available and already reported. It does not yet have any coverage of ballast trips.


Ballast legs could give complex incentives, because if a ship has an opportunity to go a long distance carrying no cargo, and so using less fuel, that would give a better CII over the year. Although shipowners may prefer to take a cargo if it is available, because they can earn money from it.


If you reduce speed, you will reduce the fuel consumption, but may also reduce the annual distance travelled, so a reduction on both the numerator and denominator of the equation. But overall, your emissions per dwt mile should be reduced.


There may be correction factors to take into account the extra emissions from vessels travelling through ice, or the reduced distance travelled by some ships which spend a lot of time in port. “It’s undecided which will be taken onboard.”


IMO will develop a “carbon intensity code”, showing in more detail how the calculation must be done.


Then to determine which category or band a ship falls into, IMO has drawn a graph for each ship segment, bulk carrier, tanker, container vessel, passenger. There are separate lines showing where the A, B, C, D, E criteria are, as a function of deadweight or gross tonnes.


For each line, the intensity reduces by 5 per cent over 2019 to 2023, and then a further 2 per cent each year, to 11 per cent in 2026.


The graph begins with an analysis of the 2019 fleet, so that in 2019, 30 per cent of vessels would have been C, 20 per cent each B and D, and 15 per cent each A and E.


There is no requirement that a certain number of ships should fall into each rating every year.


DNV calculates that if the 2019 fleet was still floating in 2030, and no changes made, and tightening rate increased to 3 per cent a year over 2026 to 2030, then 70 per cent of the tankers would fail, scoring D or E,


The audience was asked in a poll what the average CII of their ships was based on today’s operations. 4 per cent said A, 9 per cent B, 25 per centre C, 13 per cent D or E, and 49 per cent did not know.



An important component of the CII scheme is the requirement to create a Ship Efficiency Energy Management plan (SEEMP), with upgraded requirements on Jan 2023 known as “SEEMP part 3”.


It should include the methodologies of how the ship calculates the CII, the target for the next 3 years, an implementation plan, including a procedure for self-evaluation.


There will be company audits, probably including a check on how the ‘implementation plan’ has been implemented.


Public disclosure

The calculation is based on data submitted through IMO’s Data Collection System (DCS), which is not public. The European Union has an equivalent scheme, called MRV (Monitoring, reporting and verification), which is made public, although it only covers vessels going to, from or between EU ports.


“I expect that there will be review discussions on availability of DCS data,” Mr Longva said. “In a couple of years we'll see.”


DNV’s services

DNV offers services to help shipping companies calculate their CII, or verify what they have done. It can put together roadmaps for your existing ships and newbuildings, explained Øyvind Sekkesaeter, consultant maritime environmental technology with DNV.


Its roadmap for existing ships has three steps – first to calculate the CII on a vessel, second to work out the most cost efficient way to reduce carbon intensity, based on its database of energy efficiency measures, and third to prepare your company “road map” for CII compliance.


For example, you may find that in a 5 ship fleet, 4 attain D and one attains C.


To do the work, DNV maps out what energy efficiency measures are already implemented on the vessel, typically through a questionnaire. It gathers operational data on the vessel, the fuel consumption and speed profile.


Then the decarbonisation measures are ranked according to cost efficiency, defined as how much you pay to reduce one tonne of CO2 from the vessel.


Example analysis

In one example, the 8 most promising measures to reduce carbon intensity for a ship were estimated to be improving load on auxiliary engine, manual engine performance optimisation, voyage optimisation, propulsion efficiency devices (such as Mewis Duct), engine de-rating, energy efficiency lighting, a different hull coating, and variable frequency electric drives.


The study found that improving the load on the auxiliary engine could achieve a 1 per cent reduction by itself.


“We estimate that for this particular vessel, if all the measures are implemented, you would achieve a reduction of 18 per cent, without reducing the speed of the vessel,” Mr Sekkesaeter said.


The roadmap for this particular vessel showed a carbon intensity of 4.5 g CO2 / dwt mile, equating to a C rating in 2023. If all the above measures were implemented in 2023, in line with the vessel’s planned dry dock, it would stay in C rating until its expensive end of lifetime in 2028.


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