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Open IMO Carbon Intensity Indicator (CII) Calculator 🚢

What is this?

An unofficial open source implementation of the International Maritime Organisation (IMO)'s Carbon Intensity Indicator (CII).

The CII indicator aims to make the carbon intensity of any given ship easy to understand, transparent, and standardised. It does so by ranking all ships globally on an A to E rating (A being the best, E being the worst). Ship emission intensity calculations consider a mixture of weight, distance travelled in the calendar year, and the fuel used in their main engines (for a comprehensive explanation, see the methodology section).

Grades are re-calculated annually. The boundaries of what is considered "good" is a moving target, described in table 4. This moving target is intended to encourage shipping firms to constantly improve the carbon intensity of their ships to 2030. The graph below demonstrates the gradual tightening of the IMO's Carbon Intensity requirements over time. The nearer to 2030, the lower a ship's Attained CII must be to achieve an A grade.

The specification for this software can be found in IMO's resolution MEPC.354(78), adopted in June 2022. Additional references, summaries, & resolutions can be found in the References & datasets section.

[!NOTE] The repository code & software is provided as-is. While best-efforts are made to ensure its results are acurate inline with the IMO's CII specifications, the results it produces are estimates and guidance. Results should not be considered proof of regulatory compliance.

Table of Contents

• Open IMO Carbon Intensity Indicator (CII) Calculator 🚢
  • What is this?
• Table of Contents
• Software
  • Software Roadmap
  • Getting Started
    • Calculator Result Format
• Methodology
  • Ship Grade Ratio Methodology
    • Ship Grade Worked example
  • Ship Attained Carbon Intensity Methodology
  • Ship transport work methodology
  • Ship CO2 Emissions Methodology
  • Ship Capacity Methodology
• Reference Tables
  • Table 1: MEPC.353(78) - Shipping Capacity Tables
  • Table 2: MEPC.364(79) Mass Conversion between fuel consumption and CO2 emissions
  • Table 3: MEPC.339(76) - Ship Grading Boundaries
  • Table 4: Annual Carbon Reduction Factors (Z%)
  • Table 5: Common shipping measurement conversions
• Shipping Terminology & Glossary
• References & datasets
  • Further Reading
  • Useful datasets (mixed public and private)

Software

Software Roadmap

The following features are on the roadmap for the application:

• Support for Dependency Injection (DI). Currently the application does not
• Support for IMO Resolution MEPC.355(78). Currently the application considers fuel consumption only. Support for MEPC355(78) will bring additional CII properties, for example the lighting in crew quarters.

Getting Started

The library can be installed via Nuget. There is a C# dotnet console app at EtiveMor.OpenImoCiiCalculator.DemoConsoleApp, which demonstrates how to create a new instance of the calculator, submit data, and receive results in the format EtiveMor.OpenImoCiiCalculator.Core.ModelsCalculationResult.

When submitting data to the CalculateAttainedCiiRating method, the following parameters are required:

ShipType shipType,          
double grossTonnage,       
double deadweightTonnage, 
double distanceTravelled,   
TypeOfFuel fuelType,       
double fuelConsumption,  
int targetYear           

• The ship's type must be one of EtiveMor.OpenImoCiiCalculator.Core.Models.Enums.ShipType.
• Gross Tonnage is measured in long-tons (1.016047 metric tonnes, or 1,016.047 kilograms)
• Deadweight Tonnage is measured in long-tons (1.016047 metric tonnes, or 1,016.047 kilograms)
• Distance travelled is measured in nautical miles (1,852 metres)
• Fuel type must be one of EtiveMor.OpenImoCiiCalculator.Core.Models.Enums.TypeOfFuel
• Fuel consumption is measured in grams, and accepts scientific notation like 1.9e+10
• Year must refer to the measured year. For example, if a ship's fuel consumption is known in 2022, all other results will be based from that point

Multiple Fuel Type calculations

There are two CalculateAttainedCiiRating methods. One for a ship which consumes a single fuel type, and another which consumes multiple fuel types. Both methods are available at CalculateAttainedCiiRating.

Calculator Result Format

{
    "results": [
        {
            "isMeasuredYear": true,                        
            "isEstimatedYear": false,                     
            "year": 2019,                                 
            "rating": 2,                                   
            "requiredCii": 19.184190519387734,    
            "attainedCii": 16.243733333333335,
            "attainedRequiredRatio": 0.8467249799733408,
            "calculatedCo2eEmissions": 60914000000.0,
            "calculatedShipCapacity": 25000.0,
            "calculatedTransportWork": 3750000000.0,
            "vectorBoundariesForYear": {
                "year": 2019,
                "shipType": 110,
                "weightClassification": {
                    "upperLimit": 0,
                    "lowerLimit": 2147483647
                },
                "capacityUnit": 3,
                "boundaryDdVectors": {
                    "Superior": 14.579984794734678,
                    "Lower": 17.649455277836715,
                    "Upper": 21.869977192102013,
                    "Inferior": 24.939447675204054
                }
            }
        },
        ...
    ]
}

Methodology

A ship's Carbon Intensity Indicator (CII) is measured by calculating its transport workload in a given calendar year, then calculating the mass of $CO_2$ produced by the ship in that year. The ship's Attained CII is the product of its $transportWork$ and the $massOfCO_2Emissions$ in one calendar year.

$AttainedCII = massOfCo2Emissions \times transportWork$

Ships are split into 12 categories, for example "Bulk Carrier", "Tanker", "Cruise Passenger Ship" among others (see Table 1 for a comprehensive list). A ship is compared internally among its category peers but never across categories, for example, a Bulk Carrier is not directly comparable to a LNG Carrier in this system.

Inputs

• The type of ship
• The type of fuel used by the ship's main engine
• The capacity of the ship, measured in either Deadweight Tonnage (DWT) or Gross Tonnage (GT)
• The distance travelled by the ship in one calendar year, measured in nautical miles

The ship's Attained CII is then compared to its Required CII to produce an easy to understand grade for the ship. The grading scheme is in the range A to E, where A is the most efficient bracket, C represents a ship at-or-near its CII, and E is the least efficient.

Fig1. IMO Boundaries, after IMO MEPC.354(78)

Ship Grade Ratio Methodology

A ship's grade is calculated by comparing its Attained CII to its Required CII to give its performance $A/R$ ratio. If the ship's $A/R$ ratio falls below the boundary for its class of Ship Type, it attains a higher (better) grade. Boundaries are calculated as:

$shipTypeRequiredCII \times exp(d_i)$.

Ship Grade Worked example

The worked example below considers a Bulk Carrier, with a Deadweight Tonnage below 279,000. Assuming the Bulk Carrier's $required CII$ is:

$10g CO_2 / DWT.NM$

[!IMPORTANT] For some ship types, $GT \times NM$ should be used instead of $DWT \times NM$, see Table 1 and transport work done methodology for a comprehensive guide.

Then the boundaries are calculated with:

• $10 \times exp(d1)$
• $10 \times exp(d2)$
• $10 \times exp(d3)$
• $10 \times exp(d4)$.

The $exp(d_i)$ rating boundaries for each ship type can be found in Table 3. The resultant boundaries for the Bulk Carrier in question are:

Grades are then derived from these boundaries, by comparing the ship's Attained CII to the thresholds across a given calendar year:

Example Results:

• If the ship's Attained CII was $9gCO_2/ DWT \times NM$, the ship receives a grade B, as its Attained CII was above the threshold for Superior Boundary, but below the threshold for Lower Boundary.
• If the ship's Attained CII was $11gCO_2/ DWT \times NM$, the ship receives a grade D, as its Attained CII was above the threshold for Upper Boundary, but below the threshold for Inferior Boundary.

Ship Attained Carbon Intensity Methodology

A ship's Attained carbon intensity is calculated by taking the mass of its aggregate CO₂ emissions in a calendar year, and multiplying it by its transport work done in the calendar year.

$massOfCo2Emissions \times transportWork$

Method accepts:

• massOfCo2Emissions, the mass of $CO_2$ emissions in the calendar year
  • See co2 emissions methodology to calculate
• transportWork, the work carried out by the ship in the calendar year
  • See transport work methodology to calculate

Method Returns:

• A double representing the ship's Attained Carbon Intensity

Implementation:

Returns the product of a ship's mass of $CO_2$ emissions and its $transportWork$.

Ship transport work methodology

A ship's transport work is calculated by taking its capacity and multiplying it by the distance sailed in nautical miles in the calendar year.

$capacity \times distanceSailed$

Method accepts:

• capacity the ship's capacity for cargo or passengers
  • See ship capacity methodology to calculate
• distanceSailed the distance sailed in Nautical Miles in the calendar year

Implementation:

Returns the product of a ship's capacity and its distance sailed

Ship CO₂ Emissions Methodology

The sum of a ship's $CO_2$ emissions over a given year are calculated by multiplying the mass of consumed fuel by the fuel's emissions factor. If the ship consumes multiple fuel types, the calculation is repeated for each fuel type & consumption mass, then those results are summed together.

Method Accepts:

• fuelType, an enum derrived from Table 2's Fuel Type column
• fuelConsumptionMass, a double representing the mass of fuel consumed in grams (g) over the given year

Method Returns:

• A double representing the $M$ mass of $CO_2$ emitted by the ship across one calendar year

Implementation:

The sum of $CO_2$ emissions $M$ from fuel consumption in a given calendar year is

$M = FC_j \times C_{f_j}$

Where:

• $j$ is the fuel type
• $FC_j$ is the mass in grams of the consumed fuel type j in one calendar year
• $C_{f_j}$ is the fuel oil mass to CO2 mass conversion factor, given in Table 2's $C_F$ column

Ship Capacity Methodology

A ship's capacity is measured by either its Deadweight Tonnage (DWT) or Gross Tonnage (GT). The only exception is Bulk Carriers, which have a capacity capped at 279,000.

To calculate a ship's Capacity in accordance with the IMO's MEPC353(78) guidelines:

Method accepts:

• shipType, an enum, derrived from Table 1's Ship Type column
• deadweightTonnage, the deadweight tonnage of the ship, provided in long tons
• grossTonnage, the gross tonnage of the ship, provided in long tons

Method returns:

• a double representing the ship's capacity in imperial long tons

Implementation:

$Capacity$ of a given ship is calculated using the following rules:

• If the ship is a Bulk Carrier, and its DWT is 279,000 or above, its capacity is capped at 279,000
• If the ship is a Bulk Carrier, and its DWT is below 279,000, its capacity is equal to its DWT
• If the ship is a Ro-ro cargo ship (vehicle carrier), a Ro-ro passenger ship or a Cruise passenger ship, its capacity is equal to its Gross Tonnage
• Otherwise, the ships capacity is equal to its DWT

The full implementation detail can be found in Table 1's Ship Type, Ship weight, and Capacity columns.

Exceptions:

• ArgumentOutOfRangeException is thrown if the DWT is set to 0, when ship type is set to anything other than Ro-ro cargo ship (vehicle carrier), Ro-ro passenger ship or Cruise passenger ship
• ArgumentOutOfRangeException is thrown if the GT is set to 0, when ship type is set to Ro-ro cargo ship (vehicle carrier), Ro-ro passenger ship or Cruise passenger ship

Reference Tables

Table 1: MEPC.353(78) - Shipping Capacity Tables

The following table describes how to determine a given ship type's Capacity.

Table Source: IMO: MEPC.353(78)

Table 2: MEPC.364(79) Mass Conversion between fuel consumption and CO₂ emissions

The following table describes how to convert from the fuel used by a ship's main engine $ME_{(i)}$ to the amount of $CO_2$ produced. Fuel consumption is measured in grams (g), as is the output $CO_2$ emission

Table source: IMO: MEPC.364(79)

Table 3: MEPC.339(76) - Ship Grading Boundaries

The following table describes the $dd$ vectors used to determine the rating boundaries for ship types. The columns $dd$ $exp(d_i)$ values represent the boundaries the IMO's rating system in the baseline year (2019).

Table source (2022): IMO: MEPC.354(78) Previous source (2021): IMO: MEPC.339(76)

Table 4: Annual Carbon Reduction Factors (Z%)

The following table describes the reduction factor to be applied to a ship's $requiredCII$ on an annual basis. IMO have to date released figures up to 2026. In the table, the values from 2027 onwards are unofficial estimates based on the pattern to 2026. IMO aims to release new reduction factors

Table Source: IMO: MEPC.338(76)

Table 5: Common shipping measurement conversions

Often in shipping, non-metric measurements are used. Conversions are detailed below

Shipping Terminology & Glossary

References & datasets

• IMO: MEPC.337(76) - Carbon Intensity Index (CII) spec: https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MEPCDocuments/MEPC.337(76).pdf
• IMO: MEPC.364(79) - Energy Efficiency Design Index (EEDI) spec: https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MEPCDocuments/MEPC.364(79).pdf
• IMO: MEPC.339(76) - 2021 Guidelines on the operational carbon intensity rating of ships (CII Rating Guidelines, G4): https://wwwcdn.imo.org/localresources/en/OurWork/Environment/Documents/Air%20pollution/MEPC.339(76).pdf
• IMO: MEPC.339(76) - 2022 Guidelines on the operational carbon intensity rating of ships (CII Rating Guidelines, G4): https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MEPCDocuments/MEPC.354(78).pdf
• ISO 8217:2017 (Current standard) - Petroleum products, Fuels (class F), Specifications of marine fuels: https://www.iso.org/standard/64247.html
• ISO/FDIS 8217 (Standard under development) - Products from petroleum, synthetic and renewable sources, Fuels (class F), Specifications of marine fuel: https://www.iso.org/standard/80579.html

Further Reading

• IMO's press briefing, including links to the comprehensive guidelines: https://www.imo.org/en/MediaCentre/PressBriefings/pages/CII-and-EEXI-entry-into-force.aspx
• Society of Naval Architecture Students summary of CII Calculations: https://github.com/snascusat/CII-Calculator
• DNV's summary of EEXI and CII requirements: https://www.dnv.com/news/eexi-and-cii-requirements-taking-effect-from-1-january-2023-237817/

Useful datasets (mixed public and private)

• UNStats (public, non-commercial dataset): https://unstats.un.org/bigdata/task-teams/ttt-dashboards/
• Dataliastic (private commercial dataset): https://datalastic.com/pricing/
• Marine Traffic (private commercial dataset): https://servicedocs.marinetraffic.com/
• Windward.AI (private commercial datasets): https://windward.ai/