Carbon intensity of “average” ships

Abstract

This paper investigates the carbon intensity of “average” ships, i.e., the ships of different types and sizes which, in 2018, performed an average transport work and emitted an average amount of CO₂, according to the data published in the Fourth IMO GHG Study. The goal of the study is to identify the ship types and sizes which may be regarded as the best and the worst performing with respect to carbon intensity. Using the data available from the Fourth IMO GHG Study, the Carbon Intensity Indicator (CII) is calculated for each of the examined average ships and the obtained values are compared to the CII reference lines valid for 2023, 2024, 2025, and 2026. Based on the calculations, carbon intensity ratings may be assigned to examined ships for four consecutive years. Thus, it is possible to estimate the evolution of carbon intensity of examined fleet segments, provided that no measures for improvement of carbon intensity would be implemented in years to come. The analysis has shown that most of the current merchant fleet would exhibit an “inferior” (label E) performance with respect to the carbon intensity. While some of the examined average ships with “inferior” rating could attain the “moderate” rating (label C) in 2023 by relatively small reductions of 2018 CII values, most of the other ships would require considerably greater improvements. Identification of the “worst performers” would indicate which ships require immediate attention with respect to the carbon intensity. Thus, the outcomes of the study may serve as an input to policy makers when deciding on measures addressing the carbon intensity of maritime shipping.

Keywords

carbon intensity indicator fourth IMO GHG study maritime greenhouse gas emissions decarbonization of maritime transport

1. Introduction

In 2018, the International Maritime Organization (IMO) presented the so-called Initial Strategy on reduction of maritime greenhouse gas (GHG) emissions, see reference.¹ The Initial Strategy asserted the IMO vision to phase out the GHG emissions from international shipping by the end of this century. Furthermore, the Strategy introduced the so-called “levels of ambition” which outlined the milestones in the process of decarbonization of international shipping. The levels of ambition refer to intended reduction of carbon intensity (i.e. the reduction of CO₂ emissions relative to the transport work) of international shipping by at least 40% by 2030 (as compared to 2008), and by 70% by 2050 (as compared to 2008) as an average across international shipping, as well as to reduction (in absolute terms) of the total annual GHG emissions by at least 50% by 2050 as compared to 2008. The Initial Strategy also noted that the achievement of the levels of ambition was subject to deployment of innovative technologies, alternative fuels, and alternative energy sources. The Initial Strategy was followed by the 2023 IMO Strategy on reduction of maritime GHG emissions² which presented more ambitious goals. Namely, instead of the 50% reduction of the GHG emissions by 2050, the 2023 Strategy foresees the ambition to reach net-zero GHG emissions by or around 2050. The “indicative checkpoints” refer to the goals of reduction of the total annual GHG emissions from international shipping by at least 20% (striving for 30%), by 2030, compared to 2008, and by at least 70% (striving for 80%) by 2040, compared to 2008, when 940 million t of CO_2e were emitted by international shipping (see reference³).

As a catalyst of the shipping decarbonization, the IMO introduced a number of revisions in MARPOL Annex VI (see reference⁴) including the Regulation 28: Operational carbon intensity, which refers to “attained annual operational carbon intensity indicator (CII)”. CII is intended for assessment of carbon intensity of a specific existing ship and requires knowledge of the amount of CO₂ emissions generated by the ship, its capacity and the distance sailed. In this study, however, the attained annual CII for 2018 was not calculated for specific ships but for “average” ships. Namely, the information on average capacity, average distance sailed, and average emitted mass of CO₂ for 19 ship types (whereby each ship type is broken down into several size categories) for seven years in period from 2012 to 2018 can be obtained from the Fourth IMO GHG Study.⁵ This information can be used to calculate the average attained annual CII for 2018 for an “average” ship, i.e. a ship of average capacity that completed journeys corresponding to average distance, and emitted the average mass of CO₂ in 2018. Thus, such calculations indicate the average carbon intensity performance of ships within a specific size category of a specific ship type, not of a particular individual ship. However, it has been argued (see reference⁶) that carbon intensity metrics provide a better insight when applied at a (sectoral) fleet level than to individual ships.

The analysis presented in this paper has not been performed for all ship types included in the Fourth IMO GHG Study. However, the calculations were conducted for major cargo and passenger ship types: bulk carriers, oil tankers, containerships, general cargo ships, passenger cruise ships, and Ro-Ro passenger (RoPax) ships. The selected ship types account for approximately 70% of the total number of ships covered by the Fourth IMO GHG Study which would be affected by the new MARPOL Regulation 28. In addition, total CO₂ emissions of the selected ship types form approximately 82% of the total CO₂ emitted in 2018 by the ships which should comply with the CII regulations.

The described CII calculations for the selected average cargo and passenger ships are presented in detail in Chapter 2 and the carbon intensity ratings for 2018 are established for each of the examined ship types and their respective capacity categories. In addition, the carbon intensity ratings are also calculated for the period between 2023 and 2026, under the assumption of “business as usual” scenario which implies that approximately the same transport work would be done and that no measures for improvement of carbon intensity would be implemented. Furthermore, the reduction of carbon intensity necessary for attaining compliance with the CII reference lines valid for 2023, 2024, 2025, and 2026 is calculated and presented in Chapter 3. Finally, in Chapter 4 it is analyzed how much the reduction of carbon intensity that is required for compliance with the 2026 reference lines, could contribute to reduction of CO₂ emissions from maritime transport.

The existing literature which addresses the options for improvement of carbon intensity performance of maritime shipping and the applicability of different carbon intensity metrics is abundant and only a limited selection can be presented here. In reference,⁷ the CO₂ reduction potential of a number of technological and operational measures was assessed based on the review of 150 studies. The effects of combining technical and policy measures on decarbonization were discussed in reference.⁸ A comprehensive review of technical and operational measures, alternative fuels and energy sources, policies, and regulations were reviewed in reference.⁹ The GHG emissions reduction potential of ship design (ship size and hull form) and ship operation (ship speed) and associated policy implications were analyzed in reference.¹⁰ The probability of achieving of 50% reduction of GHG emissions as compared to 2008 by 2050, by employing energy efficiency design and operational measures was estimated in reference.¹¹ The limitations of slow steaming as a measure for fuel consumption reduction were demonstrated in reference.¹² Market-based measures, with the specific focus on practical aspects of fuel levy application were discussed in, e.g. references.^13,14 The deficiencies of the IMO regulatory instruments have been tackled in reference¹⁵ (where the impact of the carbon intensity metrics on energy efficient operations was questioned) and reference¹⁶ (where the effect of the Energy Efficiency Existing Ship Index on emissions reduction potential was quantified). Interestingly, in reference¹⁷ it was considered worth exploring a requirement that average carbon intensity of a fleet complies with the CII regulations, rather than individual ships—which is similar to the methodology employed in this paper. Even though the above-mentioned papers study the maritime GHG reduction potential from various angles, they all lead to a conclusion that an effective policy, supported by data, is required to achieve the IMO decarbonization goals. Nevertheless, a straightforward proposal in which fleet segments require immediate attention seems to be missing. Likewise, the quantification of effects of adopted instruments (such as CII) in terms of e.g., possible CO₂ reductions are rarely discussed. This paper aims at filling these gaps.

2. CII calculations

According to the IMO Guidelines¹⁸ IMO/MEPC (2021a), the attained annual Carbon Intensity Indicator (CII) of a ship is calculated as a ratio of the total mass of emitted CO₂ (M) in grams (g) to the transport work (W) performed during a calendar year:

Attained CI I_{ship} = \frac{M}{W} .

(1)

Transport work is calculated as:

W = C \cdot D_{t},

(2)

where C is the ship's capacity, that is, the mass of deadweight (DWT) for cargo ships in tones, and gross tonnage (GT) for passenger ships. D_t is the total distance sailed in nautical miles (nm).

The Fourth IMO GHG Study provides the information on the total mass of CO₂ emitted by ships of specific type and size, see reference.⁵ To obtain the average mass of CO₂ emitted by a ship in a specific type and size category during 2018 (M_ave), the total mass of CO₂ emissions generated by ships of the same category is divided by the number of ships in that category. The average transport work (W_ave) of a ship in the same category is calculated according to the formula (2) but instead of the capacity of a specific ship and the distance it sailed, the average ship capacity (C_ave) and the average distance sailed (D_tave) are used. Thus, the attained CII of an “average” ship is obtained by dividing the average mass of CO₂ emitted by ships in some category by the average transport work performed by ships in the same category:

Attained CI I_{average ship} = \frac{M_{ave}}{W_{ave}} .

(3)

All the data necessary to carry out the described calculations for 2018 may be found in the Fourth IMO GHG Study.

The performance of a ship with respect to carbon intensity is decided based on comparison of the calculated attained CII with the required value given by the reference line for 2019 (see reference¹⁹). The reference lines are ship-type-specific and given in the form:

Reference CII = a \cdot b^{- c},

(4)

where b is the ship's capacity (C in formula 2). The coefficients a and c are ship-type-specific and may be found in reference.¹⁹ For the ship types examined in this paper the coefficients a and c are given in Table 1. The reference lines should be gradually lowered over time, making the requirements more stringent. So far, the reduction of reference lines has been determined for years 2023–2026, see reference.²⁰

Table 1.

Parameters for calculation of the carbon intensity indicator reference line (G2), see reference.¹⁹

Ship type	a	b	c
Bulk carriers (DWT ≥ 279,000 t)	4745	279,000	0.622
Bulk carriers (DWT < 279,000 t)	4745	DWT	0.622
Oil tankers	5247	DWT	0.610
Containerships	1984	DWT	0.489
General cargo ships (DWT ≥ 20,000 t)	31,948	DWT	0.792
General cargo ships (DWT < 20,000 t)	588	DWT	0.389
Passenger cruise ships	930	GT	0.383
RoPax ships	7540	GT	0.587

Carbon intensity rating is determined based on the position of a ship's CII relative to the reference line. A ship may attain “major superior” (labeled with A), “minor superior” (labeled with B), “moderate” (labeled with C), “minor inferior” (labeled with D), and “inferior” (labeled with E) rating (where A is the best, and E is the worst CII rating). Rating boundaries are determined using the so-called “dd vectors” which are ship-type specific, see reference.²¹ In case a ship is labeled with D for three consecutive years or is labeled with E, “a plan of corrective actions to achieve the required annual operational CII” shall be developed, see reference.⁴

2.1 Carbon intensity indicators of average cargo ships

The Fourth IMO GHG Study reports the data necessary for this study (average ship capacity, average sailing distance, number of ships, and total CO₂ emitted) for the cargo ships capacity categories given in Table 2. Since CII is not applicable to ships below 5000 GT, some of the categories reported by the Fourth IMO GHG Study were excluded from the analysis. Such is the case with bulk carriers, oil tankers, and general cargo ships of capacity below 10,000 t of deadweight.

Table 2.
Capacity categories of the examined cargo ship types.

Bulk carriers Oil tankers Containerships General cargo ships

[t] [t] [-] [t]

10,000 ≤ DWT < 35,000 10,000 ≤ DWT < 20,000 TEU < 1000 10,000 ≤ DWT < 20,000

35,000 ≤ DWT < 60,000 20,000 ≤ DWT < 60,000 1000 ≤ TEU < 2000 DWT ≥ 20,000

60,000 ≤ DWT < 100,000 60,000 ≤ DWT < 80,000 2000 ≤ TEU < 3000

100,000 ≤ DWT < 200,000 80,000 ≤ DWT < 120,000 3000 ≤ TEU < 5000

DWT ≥ 200,000 120,000 ≤ DWT < 200,000 5000 ≤ TEU < 8000

DWT ≥ 200,000 8000 ≤ TEU < 12,000

12,000 ≤ TEU < 14,500

14,500 ≤ TEU < 20,000

TEU ≥ 20,000

Bulk carriers	Oil tankers	Containerships	General cargo ships
[t]	[t]	[-]	[t]
10,000 ≤ DWT < 35,000	10,000 ≤ DWT < 20,000	TEU < 1000	10,000 ≤ DWT < 20,000
35,000 ≤ DWT < 60,000	20,000 ≤ DWT < 60,000	1000 ≤ TEU < 2000	DWT ≥ 20,000
60,000 ≤ DWT < 100,000	60,000 ≤ DWT < 80,000	2000 ≤ TEU < 3000
100,000 ≤ DWT < 200,000	80,000 ≤ DWT < 120,000	3000 ≤ TEU < 5000
DWT ≥ 200,000	120,000 ≤ DWT < 200,000	5000 ≤ TEU < 8000
	DWT ≥ 200,000	8000 ≤ TEU < 12,000
		12,000 ≤ TEU < 14,500
		14,500 ≤ TEU < 20,000
		TEU ≥ 20,000

Attained annual CII for average bulk carriers corresponding to 2018 is given in Figure A.1 in Appendix A. Carbon intensity performance ranking in 2018, and in years from 2023 to 2026, in a “business as usual” scenario (i.e. in a scenario in which the same transport work would be done and the carbon intensity performance would not be improved in comparison to 2018) is given in Table 3. The carbon intensity performance of average bulk carriers worsens as the size of the ships increases. Average bulk carriers that belong to the categories whose capacity is between 10,000 and 35,000 t, between 35,000 and 60,000 t, and between 60,000 and 100,000 t of deadweight would retain the “moderate” performance (label C) throughout the 2023–2026 period, even without taking any steps aimed at reduction of CO₂ emissions, and provided that approximately the same transport work would be performed in the future (i.e. in the “business as usual scenario”). On the other hand, average large bulk carriers, with capacity between 100,000 and 200,000 t of deadweight, as well as those with capacity greater than 200,000 t, would be rated as “minor inferior” (label D) and “inferior” (label E) respectively, as early as in 2023. The 2018 carbon intensity performance of average bulk carriers with capacity between 35,000 and 100,000 t of deadweight, would be sufficient for the “moderate” performance (label C) until 2026, when it would drop to “minor inferior” performance (label D).

Table 3.

Carbon intensity performance of average bulk carriers in 2018 compared to the reference lines for 2019 and for years from 2023 to 2026, in a “business as usual” scenario.

	10,000 ≤ DWT < 35,000	35,000 ≤ DWT < 60,000	60,000 ≤ DWT < 100,000	100,000 ≤ DWT < 200,000	DWT ≥ 200,000
2019	B	C	C	C	D
2023	C	C	C	D	D
2024	C	C	C	D	E
2025	C	C	C	D	E
2026	C	C	C	D	E

Figure A.2 in Appendix A shows the position of the annual attained CII of average oil tankers relative to the CII reference lines. Carbon intensity performance ranking of oil tankers in 2018, and in years from 2023 to 2026, in a “business as usual” scenario, is given in Table 4. Contrary to bulk carriers, the carbon intensity performance of average oil tankers improves (albeit marginally) as the size of the ships increases. Average oil tankers in almost any capacity category would exhibit the “inferior” carbon intensity performance already in 2023. A slightly better performance may be expected of average oil tankers with the capacities between 80,000 and 120,000 t of deadweight (label D until 2025), and over 200,000 t of deadweight (label D until 2026).

Table 4.

Carbon intensity performance of average oil tankers in 2018 compared to the reference lines for 2019 and for years from 2023 to 2026, in a “business as usual” scenario.

	10,000 ≤ DWT < 20,000	20,000 ≤ DWT < 60,000	60,000 ≤ DWT < 80,000	80,000 ≤ DWT < 120,000	120,000 ≤ DWT < 200,000	DWT ≥ 200,000
2019	E	E	D	D	D	D
2023	E	E	E	D	D	D
2024	E	E	E	D	E	D
2025	E	E	E	E	E	D
2026	E	E	E	E	E	E

Table 5.

Carbon intensity performance of average containerships in 2018 compared to the reference lines for 2019 and for years from 2023 to 2026, in a “business as usual” scenario.

	TEU < 1000	1000 ≤ TEU < 2000	2000 ≤ TEU < 3000	3000 ≤ TEU < 5000	5000 ≤ TEU < 8000	8000 ≤ TEU < 12,000	12,000 ≤ TEU < 14,500	14,500 ≤ TEU < 20,000	TEU ≥ 20,000
2019	B	C	C	D	E	E	D	C	C
2023	B	D	C	D	E	E	E	C	C
2024	B	D	D	D	E	E	E	D	C
2025	C	D	D	D	E	E	E	D	C
2026	C	E	D	E	E	E	E	D	D

Table 6.

Carbon intensity performance of average general cargo ships in 2018 compared to the reference lines for 2019 and for years from 2023 to 2026, in a “business as usual” scenario.

	10,000 ≤ DWT < 20,000	DWT ≥ 20,000
2019	D	D
2023	E	D
2024	E	D
2025	E	D
2026	E	E

The position of the annual attained CII of average containerships in relation to the reference lines is given in Figure A.3 in Appendix A. The best performing average containerships are the smaller ones, with capacities below 1000 TEU: their carbon intensity would be “minor superior” in 2023 (label B) and would not go below “moderate” even in 2026. Average Ultra Large Containerships exceeding 20,000 TEU capacity would be the second-best performing containerships, as they would keep the “moderate” carbon intensity performance until 2026. The remaining containership capacity categories, in range above 1000 TEU and below 20,000 TEU, with very few exceptions, would exhibit “minor inferior” or “inferior” performance as early as in 2023. The worst performing would be the average containerships with capacity between 5000 and 8000 TEU, 8000 and 12,000 TEU, and 12,000 and 14,500 TEU (Table 5). These containership capacity categories constitute around a quarter of the total number of containerships and around 54% of containership fleet capacity in terms of deadweight in 2018, according to the data given in the Fourth IMO GHG Study.

Average general cargo ships show poor carbon intensity performance in both capacity categories which are within the scope of the CII regulations (Table 6). From Figure A.4 in Appendix A it is apparent that the average general cargo ships are well above the CII reference lines.

2.2 Carbon intensity indicators of average passenger ships

The capacity categories of the passenger ship types examined in this study are presented in Table 7, as given in the Fourth IMO GHG Study. Since CII applies to ships of 5000 GT and above, the passenger cruise ships of capacity < 2000 GT, and RoPax ships of capacities < 5000 GT fall out of scope of this study.

Table 7.
Capacity categories of the examined passenger ship types.

Passenger cruise ships RoPax ships

[-] [-]

2000 ≤ GT < 10,000 5000 ≤ GT < 10,000

10,000 ≤ GT < 60,000 10,000 ≤ GT < 20,000

60,000 ≤ GT < 100,000 GT ≥ 20,000

100,000 ≤ GT < 150,000

GT ≥ 150,000

Passenger cruise ships	RoPax ships
[-]	[-]
2000 ≤ GT < 10,000	5000 ≤ GT < 10,000
10,000 ≤ GT < 60,000	10,000 ≤ GT < 20,000
60,000 ≤ GT < 100,000	GT ≥ 20,000
100,000 ≤ GT < 150,000
GT ≥ 150,000

The Fourth IMO GHG Study reports only the average mass of deadweight of the examined ship types, but the exact average gross tonnage (required for the calculation of carbon intensity of passenger ships) for all passenger ship types and size categories is not known. Therefore, the attained annual CII of the average passenger ships was calculated assuming that the average capacity may take any value of the gross tonnage within the range.

Based on such calculations it is possible to conclude that, regardless of the average capacity, the cruise ships of gross tonnage between 2000 and 10,000 GT would attain an annual CII greater than required even by the initial reference line, see Figure A.5 in Appendix A. The same applies to the cruise ships of capacity between 60,000 and 100,000 GT. In other words, an average cruise passenger ship which belongs to one of these categories would be rated with D or E at the very beginning of implementation of the new regulations on carbon intensity of existing ships. Conversely, the best performing average cruise ships would be the ones with the average capacity exceeding 150,000 GT.

In case that the average capacity of the RoPax ships in category 5000 ≤ GT < 10,000 is at least 7500 GT, an average RoPax ship of this category would have the moderate carbon intensity performance in 2018, and it would maintain this status until 2026. Nevertheless, RoPax ships in capacity categories 10,000 ≤ GT < 20,000 would exhibit minor inferior or even inferior performance, regardless of the average capacity. This means that at least 69% of the RoPax ship fleet subject to the CII requirements would be labeled with D or E at the beginning of implementation of the new MARPOL regulations. The outcome of calculations for RoPax ships is presented in Figure A.6 in Appendix A.

3. Improvements of carbon intensity performance of major ship types necessary for compliance with 2023–2026 reference lines

The analysis presented in this section aims at answering how much the calculated CII of an average ship would have to be reduced to achieve at least the moderate (label C) carbon intensity performance in years 2023 to 2026.

It was previously shown that the bulk carriers of capacity between 10,000 and 100,000 t could keep their moderate carbon intensity performance even in the “business as usual” scenario (see Table 3). An average bulk carrier of capacity over 200,000 t of deadweight would have to reduce its 2018 CII by at least 9.7% to reach the acceptable “moderate” level of carbon intensity in 2023. That alone, however, would not be sufficient to avoid dropping to “minor inferior” level already in 2024. In fact, to retain the “moderate” carbon intensity performance level in 2026, an average bulk carrier in this capacity category would have to reduce its CII value attained in 2018 by at least 15.4% (Figure 1).

Figure 1.

Reduction of CII of average bulk carriers attained in 2018, necessary to meet the 2023 to 2026 CII requirements.

Average oil tankers in all capacity categories would require their CII values attained in 2018 to be reduced by between 11.4% (for ships of capacity greater than 200,000 t) and 37.2% (for ships of capacity between 10,000 and 20,000 t) to attain the moderate carbon intensity performance in 2023, see Figure 2. To keep the same carbon intensity performance in 2026, the required 2018 CII reductions would range between 17% and 41.2%.

Figure 2.

Reduction of CII of average oil tankers attained in 2018 necessary to meet the 2023 to 2026 CII requirements.

Average containerships with capacities 5000 ≤ TEU < 8000, and 8000 ≤ TEU < 12,000, would have to reduce their CII values attained in 2018 by 21.5% and 21.1% respectively to comply with the 2026 CII reference lines (Figure 3). Average containerships with capacities 2000 ≤ TEU < 3000, and 14,500 ≤ TEU < 2000 would need a single-digit reduction (4.6% and 4.9% respectively) of their 2018 CII values. It was previously indicated that the Ultra Large Containerships would keep moderate performance until 2026 in a “business as usual” scenario (see Table 5); now it is possible to state that keeping the same status in 2026 would require the reduction of 2018 CII value by not more than 0.9%.

Figure 3.

Reduction of CII of average containerships attained in 2018 necessary to meet the 2026 CII requirements.

The average general cargo ships that belong to the category of capacity between 10,000 and 20,000 t of deadweight would have to reduce their 2018 CII by 12.9% to gain the moderate carbon intensity rating in 2023, and by 18.4% to retain it in 2026. The average general cargo ships in the next capacity category (greater than 20,000 t of deadweight) would require smaller reductions: 6% to meet the target in 2023, and 12% to comply with the 2026 target (Figure 4).

Figure 4.

Reduction of CII of average general cargo ships attained in 2018 necessary to meet the 2026 CII requirements.

The calculations for average cruise passenger ships and average RoPax ships are not given, considering that the assessment depends on the average gross tonnage for which the exact figures are not available. However, some estimates of possible CO₂ reductions that may be achieved as a consequence of compliance of cruise passenger and RoPax ships with the CII regulations in 2026 will be given in Chapter 4.

4. Contribution of CII to reduction of CO₂ emissions

Notwithstanding the fact that CII regulations aim at improving the carbon intensity performance, rather than decreasing the absolute amount of emissions, it is investigated how much the CO₂ emissions from maritime shipping could be reduced in absolute terms if the selected ship types and categories achieve the compliance with CII requirements for 2026, that is, if they attain at least “moderate” performance by 2026. Theoretically speaking, the compliance with the CII requirements could be achieved by changing either the numerator or the denominator, or both in equation (1). In this paper, however, it is assumed that the compliance would be achieved by reducing the CO₂ emissions only (Tables 8 and 9). This should indicate the maximum potential reduction of CO₂ emissions in 2026, in comparison to 2018 levels. Table 10 summarizes the possible reduction of CO₂ emissions from the examined cargo ship types. It may be interesting to note that the greatest reduction of CO₂ emissions may not be achieved by the greatest emitters. For instance, in 2018, bulk carriers emitted more CO₂ in absolute terms than oil tankers and general cargo ships combined; however, since they perform better in terms of carbon intensity than oil tankers, the CO₂ reduction required for compliance with 2026 CII reference line would be much smaller than that of oil tankers (Table 8).

Table 8.
Reduction of CO₂ emissions relative to 2018 levels as a consequence of compliance of major cargo ship types with 2026 CII reference line.

CO₂ emissions in 2018 CO₂ reduction CO₂ reduction relative to 2018 emissions

Ship type [million t] [million t] [%]

Bulk carriers 189.7 6.6 3.5

Oil tankers 129.8 27.8 21.4

Containerships 232.1 32.7 14.1

General cargo ships 26.4 4.0 15.1

Table 9.

Reduction of CO₂ emissions relative to 2018 levels as a consequence of compliance of major passenger ship types with 2026 CII target.

	CO₂ emissions in 2018	CO₂ reduction	CO₂ reduction relative to 2018 emissions
Ship type	[million t]	[million t]	[%]
Cruise passenger ships	28.2	9.6 (Upper capacity limit)	34.2
Cruise passenger ships	28.2	2.2 (Lower capacity limit)	7.9
RoPax ships	27.6	8.3 (Upper capacity limit)	30
RoPax ships	27.6	0.3 (Lower capacity limit)	1.1

Table 10.

Maximum possible reduction of absolute CO₂ emissions in comparison to 2018 levels as a consequence of compliance of major cargo ship types with 2026 CII reference line.

Ship type	Capacity category	CO₂ reduction [million t]
Bulk carriers
	100,000 ≤ DWT < 200,000	3.2
	DWT ≥ 200,000	3.4
		Σ 6.6
Oil tankers
	5000 ≤ DWT < 10,000	2.1
	10,000 ≤ DWT < 20,000	1.2
	20,000 ≤ DWT < 60,000	4.8
	60,000 ≤ DWT < 80,000	2.8
	80,000 ≤ DWT < 120,000	5.8
	120,000 ≤ DWT < 200,000	5.5
	DWT ≥ 200,000	7.7
		Σ 27.8
Containerships
	1000 ≤ TEU < 2000	2.8
	2000 ≤ TEU < 3000	1.0
	3000 ≤ TEU < 5000	4.7
	5000 ≤ TEU < 8000	8.8
	8000 ≤ TEU < 12,000	12.2
	12,000 ≤ TEU < 14,500	3.8
	14,500 ≤ TEU < 20,000	0.5
	TEU ≥ 20,000	0.03
		Σ 32.7
General cargo ships
	10,000 ≤ DWT < 20,000	2.3
	DWT ≥ 20,000	1.6
		Σ 4.0
Total CO₂ reduction for all considered cargo ships		Σ 71.0

Table 11.

Maximum possible reduction of absolute CO₂ emissions in comparison to the 2018 levels as a consequence of compliance of major passenger ship types with 2026 CII reference lines; the calculations were performed for the lower and the upper limit of capacity range for each of the capacity categories.

Ship type	Capacity category	Assumed capacity	CO₂ reduction [million t]
Cruise passenger ships Lower capacity limit
	2000 ≤ GT < 10,000	5000 GT	0.5
	10,000 ≤ GT < 60,000	10,000 GT	2.4
	60,000 ≤ GT < 100,000	60,000 GT	4.2
	100,000 ≤ GT < 150,000	100,000 GT	2.3
	GT ≥ 150,000	150,000 GT	0.2
			Σ 9.6
Cruise passenger ships Upper capacity limit
	2000 ≤ GT < 10,000	9999 GT	0.2
	10,000 ≤ GT < 60,000	59,999 GT	—
	60,000 ≤ GT < 100,000	99,999 GT	1.6
	100,000 ≤ GT < 150,000	149,999 GT	0.5
	GT ≥ 150,000	* 230,000 GT	—
			Σ 2.2
RoPax ships Lower capacity limit
	5000 ≤ GT < 10,000	5000 GT	0.5
	10,000 ≤ GT < 20,000	10,000 GT	2.1
	GT ≥ 20,000	20,000 GT	5.7
			Σ 8.3
RoPax ships Upper capacity limit
	5000 ≤ GT < 10,000	9999 GT	—
	10,000 ≤ GT < 20,000	19,999 GT	0.3
	GT ≥ 20,000	** 75,000 GT	—
			Σ 0.3
Total CO₂ reduction for considered passengers ships
Lower capacity limit			Σ 17.9
Upper capacity limit			Σ 2.5

* Corresponding to the gross tonnage of the largest existing cruise passenger ship.

** Corresponding to the gross tonnage of the largest existing RoPax ship.

Again, the lack of average gross tonnage information for passenger ships prevents us from calculating the possible reduction of CO₂ emissions with the same accuracy as for the cargo ships. It is, however, possible to calculate the range of emissions reduction assuming that the average capacity corresponds to the lowest capacity in a ship capacity category (“lower capacity limit”) or that the average capacity corresponds to the highest capacity in a ship capacity category (“upper capacity limit”), see Table 11. It may be concluded that at least 2.5 million t but not more than 17.9 million t of CO₂ could be saved by meeting the 2026 CII targets for cruise passenger ships and RoPax ships (Table 11).

To conclude, the possible reduction of CO₂ emissions achieved by compliance of the selected ship types with 2026 CII targets, could be between 73.6 and 88.9 million t. Thus, considering that the total CO₂ emissions from international and domestic shipping, and fishing, calculated using the bottom-up approach, amounted to 1056 million t in 2018 (see reference⁵ IMO, 2020), the possible reduction of shipping CO₂ emissions could be between 7% and 8.4%. If 2008 is considered as the base year, when 921 million t of CO₂ were emitted by international shipping,³ the possible reduction of shipping CO₂ emissions in comparison to 2008 levels could be between 8% and 9.7%.

5. Conclusions

The study presented in this paper aimed at providing an indication of the carbon intensity of the existing merchant fleet. The study comprised major ship types: bulk carriers, oil tankers, containerships, general cargo ships, cruise passenger ships, and Ro-Ro passenger (RoPax) ships. Based on the IMO procedure for calculation of CII, and using the data reported in the Fourth IMO GHG Study, a method for assessment of average carbon intensity of ships of different size categories within the analyzed ship types was developed. The analysis of the obtained results led to the following findings.

The analysis has shown that most of the current merchant fleet would exhibit an inferior performance with respect to carbon intensity. The only exceptions among the examined cargo ship types are bulk carriers of capacity between 10,000 and 100,000 t of deadweight, and small containerships with capacity below 1000 TEU. Considering that the average gross tonnage required for calculation of CII for passenger ships was not available, it was more difficult to estimate the carbon intensity performance of cruise passenger ships and RoPax ships. Nevertheless, it was possible to conclude that the cruise passenger ships of capacity between 2000 and 10,000 GT, and between 60,000 and 100,000 GT would have inferior carbon intensity rating, regardless of the actual average capacity. The same is valid for the RoPax ships of capacity between 10,000 and 20,000 GT.

Some of the examined average ships that exhibit inferior carbon intensity performance could attain the “moderate” rating (label C) in 2023 by relatively small reductions of 2018 CII values. Such is the case with e.g., bulk carriers of capacity between 100,000 and 200,000 t of deadweight which would have to reduce carbon intensity achieved in 2018 by less than 2% or containerships of capacity between 1000 and 2000 TEU whose 2018 CII values would have to be decreased by 4%. However, most of the other ships would require considerably greater improvements of carbon intensity to be able to obtain at least C rating in 2023. For oil tankers, which seem to be the worst performers in terms of carbon intensity, CII values would have to be reduced between 11.4% and 37.2%, depending on the capacity of the ship.

Finally, if the compliance with 2026 CII targets for bulk carriers, oil tankers, containerships, general cargo ships, cruise passenger ships, and RoPax ships would be achieved exclusively by reducing the CO₂ emissions, it was estimated that the absolute CO₂ emissions could be reduced by up to 8.4% as compared to 2018 levels, and up to 9.7% as compared to 2008 levels. In this respect, however, the findings are incomplete because not all the ship types which are subject to MARPOL Regulation 28 have been considered. Nevertheless, considering that the analysis comprised approximately 70% of the fleet which would be affected by the new MARPOL Regulation 28 and more than 80% of total CO₂ emissions emitted in 2018 by ships which should comply with the CII regulations, it is believed that the results are sufficiently representative to provide a valuable insight into carbon intensity performance of maritime transport. The presented analysis makes practical use of the publicly available data to identify those ship types and sizes which may be regarded as the worst and the best performers with respect to the carbon intensity, and to quantify the possible CO₂ reduction which could be achieved as a result of compliance with the CII regulations. This information could serve as an input to policy makers when deciding on the measures to tackle the carbon emissions of maritime shipping.

Footnotes

ORCID iD

Igor Bačkalov

Funding

The author received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Appendix A: Carbon intensity indicators of major ship types

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Carbon intensity of “average” ships

Abstract

Keywords

1. Introduction

2. CII calculations

Table 7. Capacity categories of the examined passenger ship types. Passenger cruise ships RoPax ships [-] [-] 2000 ≤ GT < 10,000 5000 ≤ GT < 10,000 10,000 ≤ GT < 60,000 10,000 ≤ GT < 20,000 60,000 ≤ GT < 100,000 GT ≥ 20,000 100,000 ≤ GT < 150,000 GT ≥ 150,000

Footnotes

ORCID iD

Funding

Declaration of conflicting interests

Appendix A: Carbon intensity indicators of major ship types

References

Table 7.
Capacity categories of the examined passenger ship types.

Passenger cruise ships RoPax ships

[-] [-]

2000 ≤ GT < 10,000 5000 ≤ GT < 10,000

10,000 ≤ GT < 60,000 10,000 ≤ GT < 20,000

60,000 ≤ GT < 100,000 GT ≥ 20,000

100,000 ≤ GT < 150,000

GT ≥ 150,000