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3rd International conference of Chemical, Energy
and Environmental Engineering
July 2021 Egypt Japan University of Science and
Technology, Alexandria, Egypt.
Technical and environmental performance investigation of Marine
Alternative fuels
Mostafa A. El-Manzalawy 1, a, Mohamed M. ElGohary1, b, Maged M.
AbdElnaby1, c
1Department of Naval Architecture and Marine Engineering, Faculty of Engineering, Alexandria
University, Alexandria, Egypt
a Mostafa_211177@yahoo.com, b Mohamed.elgouhary@alexu.edu.eg,
cmaged.abdelnaby@alexu.edu.eg
Keywords: Ship emissions reduction, IMO regulations, Natural gas, Methanol, Energy Efficiency
Abstract. Environmental issues, for example, the expanded air pollutant emissions from ships are
progressively affecting the operation of ships. Therefore, International Maritime Organization (IMO)
has adopted many goals to decarbonizing the shipping industry by at least 40% by 2030. Marine fuels
play a major role in these goals because of the emissions resulting from the combustion process.
Therefore, the present research proposes to convert the conventional engine operated by marine diesel
oil (MDO) to a dual-fuel engine operated by either natural gas (NG) or methanol. As a case study,
A15-class container ship is investigated. The results showed that the dual-fuel engine operated with
(98.5% NG and 1.5% MDO) will reduce CO2, SOx, and NOx emissions by 28%, 98% and 85%,
respectively when compared with their values for conventional diesel engine. On the other hand, the
reduction percentages reach to 7%, 95% and 80% when using a dual-fuel engine operated with (95%
Methanol and 5% MDO), respectively. The proposed dual-fuel engines operated by either NG and
methanol will imrove the ship energy efficiency index by 26% and 7%, respectively.
Introduction
Currently, there are several legislations in addition to many goals adopted by the International
Maritime Organization (IMO) to reduce greenhouse gases (GHG) and achieve a blue economy [1].
One of those goals is to reach a 50 percent reduction in the percentage of GHG emitted from ships by
2050 compared to 2008 [2]. There are several mechanisms that can be followed to reduce GHG from
ships, include ship design, propulsion systems, alternative fuels [3–6] and renewable energy [7].
Among these methods, alternative fuels of less carbon content are considered one of the best ways to
reduce the GHG emitted from ships. The main alternative marine fuel types may be found in two
forms: liquid and gaseous fuels. Liquid marine alternative fuels include Methanol, Ethanol, and Bio
liquid fuel. On the other hand, the main alternative gasses fuels include Natural gas, Propane,
Hydrogen, and Ammonia [8].
Two alternative types will be considered throughout the present project, mainly: Natural gas (NG)
and Methanol. Selection of the previous types is the matter of searching for alternative fuels that have
less emissions to be applied on board ships in the short term. Methanol has been investigated as an
alternative marine fuel in previous research projects such as Swedish EffShip [9], SPIRETH project
[10], and Methaship,. Some studies by [11,12] has been carried to evaluate the applicability of using
methanol as an alternative marine fuel. Another research by [13] shows that methanol reduce exhaust
emissions by a considerable amount and reduce the fuel cost.
The primary segment of natural gas is methane (CH4), this fuel is the least carbon and sulfur content
and consequently with the most promising option to decrease carbon dioxide (CO2) and Sulfur
dioxide (SOx) emissions [5]. Besides, the burning of natural gas in comparison with diesel is
characteristically cleaner regarding Nitrogen oxide (NOx). Moreover, natural gas appears as a
3rd International conference of Chemical, Energy
and Environmental Engineering
July 2021 Egypt Japan University of Science and
Technology, Alexandria, Egypt.
financially motivating measure for vessel types spending a long period of their cruising time like
handy size tankers, RO-RO vessels, and container ships [4].
All the previous studies, whether research projects or research papers that dealt with the
importance of alternative fuels usage onboard ships, confirm that the maritime industry has not
benefited the most from alternative fuels. Moreover, it confirms the necessity of conducting many
other studies to determine the potential benefits from alternative fuel onboard ships from technical
and environmental point of view.
The present research aims at assessing the environmental and technical performance of the
proposed alternative fuels (natural gas and methanol). As a case study, A15-class container ship is
investigated. The assessment is based on a comparative study between alternative fuels and
conventional diesel fuel from environmental and energy efficiency point of view.
Environmental and technical assessment method
The environmental assessment can be performed by calculating the exhaust emissions from ships in
case of using the proposed alternative fuels compared with the conventional diesel fuel. The emissions
from ships included many kinds of pollutants such as CO2, SOx and NOx emissions.
The quantity of exhaust emission during one trip () can be calculated by using Eq. (1) which
depending on the engine power.
(1)
Where (MCR) is the maximum continuous rating power of engine in [kW], (i) is the type of engine
(main engine or auxiliary engine), L is the load factor of engine and T is the operating time of ship in
[hour], and () is the pollutant emission factor in an energy based form [g pollutant/kWh] [14,15].
The individual emission energy-based rate in differs from type to another. In case of CO2 emission,
it is based on the conversion factor between fuel and CO2 which depend on the carbon content in fuel,
therefore, its value differs from fuel to another. Table 1 show the conversion factor values for different
fuels [4]. Table 1 Conversion factors and carbon contents for marine fuels
Fuel type
Carbon content
Conversion factor (g CO2/ g fuel)
Marine Diesel oil (MDO)
0.8744
3.206
Heavy fuel oil (HFO)
0.8493
3.114
Liquefied natural gas (LNG)
0.75
2.75
Methanol
0.37
1.375
The energy-based rate of CO2 emission () measured in g CO2/kWh can be calculated using
Eq. (2) based on specific fuel consumption (SFC) in g fuel /kWh and the conversion factor CF).
(2)
Regarding the air pollution emission inventory recommendation from IMO, NOx emission factor
expressed in g/kWh for slow speed diesel engine depends on the ship construction date [4]. The first
level of control (Tier I) applies for ships constructed on 1 January 2000 or after and can be calculated
as shown in Eq. (3) which depends on the engine’s rated speed (n).
(3)
A slow speed diesel engine (SSDE) that is installed on a ship constructed on 1 January 2011 or
after (Tier II), a reduction equal to 15% should be fulfilled compared with Tier I NOx emission value
[14]. On the other hand, NOx emission factor for natural gas engine and methanol engine is 2.16
g/kWh and 2.47 g/kWh, respectively [4,13].
On the other hand, SOx is proportional to SFC and the content of sulfur in the fuel (S) so that the
SOX emission energy-based rate () can be calculated by Eq. (4) [8,16,17].
(4)
3rd International conference of Chemical, Energy
and Environmental Engineering
July 2021 Egypt Japan University of Science and
Technology, Alexandria, Egypt.
It is seen that lower the sulfur content in fuel is led to reducing the specific emission rate of SOx,
which is the reason why more and more strict demands towards lower sulfur content in marine fuel.
In case of dual-fuel engine, the emission factor should be evaluated by considering the percentage of
each fuel as shown in Eq. (5) [4].
(5)
Where, and are the percentages of gas and pilot fuels in the dual-fuel engine (DF),
and are the pollutant (p) emission factors for gas and pilot fuels, respectively.
The technical performance can be assessed by using the procedure recommended from IMO
through the calculation of Energy Efficiency Design Index (EEDI) [8]. EEDI has two indexes, a
restrictive value () and the actual value () which should be lower than the restrictive
value. The restrictive value depends on the ship type and its deadweight (DWT); therefore, Eq. (6)
should be used for the calculation of in case of container ship.
(6)
Where (X) is the reduction rate of baseline value each five years as recommended from IMO; 10%
in phase 1 (2015-2019), 20% in phase 2 (2020-2024) and 30% in phase 3 (2025-onwards) [3,18].
On the other hand, the actual value is a measure of energy efficiency level for the specified ship
and can be calculated as shown in Eq. (7). For the dual-fuel engine, the product of ( )
can be calculated by using Eq. (8) depending on the SFC and CF of either gas fuel and pilot fuel [4].
(7)
(8)
Where (PME) is 75% of MCR for each main engine (ME) in kW, ( ) is the operational ship
speed in knots and (capacity) is 70% of the container ship deadweight. The auxiliary engine (AE)
power necessary to operate the main engine and the crew accommodation is based on the MCR of
the main engine in case of using an engine of more than 10,000 kW as shown in Eq. (7) [4,19].
Case study description
The case study for the assessment process of energy efficiency and environmental impacts is selected
to be A15-class container ship. The container ship (Al Jmeliyah) is owned to United Arab shipping
company limited Dubai branch and operated by Hapag-Lloyd, Hamburg [20]. The ship was built in
2017 and sailing under the flag of Marshall Islands. Table 2 shows the technical data of the ship [21].
Table 2 Main specifications of the studied container ship
Ship type
A15-class container ship
IMO number
9732357
Length overall, [m]
368
Breadth, [m]
51
Service speed, [knots]
24
Deadweight, [ton]
149360
Container capacity, TEU
14993
Main Engine type
2×Hyundai-MAN B&W 9S90 ME-C
MCR power, [kW]
2×37,620 kW at 72 RPM
The vessel normally serves the Far East route from Asia to Northern Europe through the Suez
Canal. The average time for each trip is 47 days from Busan in Asia to Hamburg in Northern Europa
[22].
3rd International conference of Chemical, Energy
and Environmental Engineering
July 2021 Egypt Japan University of Science and
Technology, Alexandria, Egypt.
The ship is currently powered by a two SSDE (MAN 9S90 ME-C) with an output of 37,620 kW
at 72 rpm which operated with marine diesel oil (0.5% S). The main engine is proposed to be
converted to 9G80ME-C10.5-GI dual-fuel engine (DFE) with the same power and speed operated by
natural gas and 1.5% MDO as a pilot fuel. On the other hand, it is proposed to be converted to MAN
B&W ME-LGI dual-fuel engine that can run on methanol and 5% MDO as a pilot fuel. The proposed
engine’s cylinder head is equipped with two valves for gas injection and two conventional valves for
the pilot fuel oil. ME-GI has the same efficeincy, power and dimensions of ME-C. Based on Hapag-
Lloyd reports, around 350 container sites will be lost for the additional gas storage system [23].
Results and discussions
The environmental performance can be assessed by evaluating the exhaust emission rates per trip.
The examined emission types are CO2, SOx, and NOx, as these types are related with IMO
regulations. The assessment process depends on the comparative study between the proposed dual-
fuel engine operated with natural gas or methanol and the conventional SSDE operated with MDO
(0.5%S). The first step in evaluating the environmental benefits of proposed dual-fuel engine is to
calculate the energy-based emissions factors as discussed before. The different emissions rates per
trip can be calculated based on the specified trip from Busan to Hamburg. The relative emissions rates
of the proposed dual-fuel engine compared to diesel engine are shown in Fig.1.
Fig. 1 Relative emissions rates of the proposed dual-fuel engine compared to diesel engine
For the current case study, the emissions rates of SSDE are 39.1 ton/hr, 2.13 kg/min and 20.4
kg/min for CO2, SOx, and NOx, respectively. These rates are reduced after applying dual-fuel engine
(98.5% NG and 1.5% MDO) to 28.2 ton/hr, 0.032 kg/min and 2.97 kg/min with reduction percentages
of 28%, 98% and 85%, respectively. These rates are reduced after applying dual-fuel engine (95%
Methanol and 5% MDO) to 36.25 ton/hr, 0.107 kg/min and 0.032 kg/min with reduction percentages
of 7%, 95% and 80%, respectively.
NOx and SOx emission rates should be compared with the IMO 2016 and 2020 emission-limit
rates, respectively [4,8]. IMO 2020 SOx emission limit rate can be predicted based on fuel sulfur
content (0.5%) which equals 2.133 kg/min. For the case study, SOx emission rates can be calculated
for different pilot fuel percentage in dual-fuel engine to assess the effect of its value on emission rates
as shown in Fig.2.
100%100%100%
72%
2%
15%
93%
5%
20%
0%
20%
40%
60%
80%
100%
120%
CO2 SOx NOx
Relative emissions compared to
diesel engine, %
SSDE (MDO) DFE (NG +1.5% pilot fuel) DFE (Methanol+5% pilot fuel)
3rd International conference of Chemical, Energy
and Environmental Engineering
July 2021 Egypt Japan University of Science and
Technology, Alexandria, Egypt.
Fig. 2 SOx emission rates at different pilot fuel percentages
It can be noticed that SOx emissions rates for dual-fuel engine are compliant with IMO 2020 limit
at different pilot fuel percentage.
IMO 2016 NOx emission limit rate can be predicted based on engine speed which equals 4.26
kg/min. For the dual-fuel engine operated by natural gas and pilot fuel, NOx emissions rates can be
calculated for different pilot fuel percentages to evaluate the impact of its value on emission rates as
shown in Fig.3.
Fig. 3 NOx emission rates at different pilot fuel percentages
As shown in Fig.3, the dual-fuel engine operated by natural gas and methanol will be compliant
with the required IMO limit if the percentage of pilot fuel is lower than 8.8% and 6.4%, respectively.
Furthermore, the energy efficiency can be assessed by the calculation of EEDI for the proposed
dual-fuel engine as recommended by IMO. By conducting the reference EEDI procedure to the case
study, it is shown that the reference EEDI and its value in the three phases can be calculated based
on the deadweight of the container ship as investigated in Fig. 4.
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
1.0% 3.0% 5.0% 7.0% 9.0%
SOx emission rate (kg/min)
Pilot fuel percent in the dual-fuel engine
IMO 2020
1
1.4
1.8
2.2
2.6
3
3.4
3.8
4.2
4.6
5
5.4
1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% 8.0% 9.0% 10.0%
NOx emission rate (kg/min)
Pilot fuel percent in the dual-fuel engine
DFE (NG) IMO NOx limit DFE (Methanol)
3rd International conference of Chemical, Energy
and Environmental Engineering
July 2021 Egypt Japan University of Science and
Technology, Alexandria, Egypt.
Fig. 4 Reference EEDI values for Container ship
This reference value will be compared with the actual attained EEDI for the case study powered
by SSDE which can be calculated by using Eq. (7) based on 24 knots service speed, 3.206 ton-
CO2/ton-fuel conversion factor of fuel to CO2. The attained EEDI will be 11.91 g CO2/DWT-NM. It
is noticed that the current EEDI of SSDE is fulfilling the EEDI requirement until phase 2 but must be
reduced to comply with EEDI phase 3.
To evaluate the energy efficiency benefits for the selected dual-fuel engine operated by either
natural gas or methanol, attained EEDI should be calculated. Based on Eq. (7) and Eq. (8), the attained
EEDI for dual-fuel engine (98.5% NG and 1.5% MDO) and (95% Methanol and 5% MDO) is 8.77
gCO2/DWT-NM and 11.07 g CO2/DWT-NM, respectively. To assess the results, it should be
compared with the reference EEDI at different phases as shown in Fig.5.
Fig. 5 Relative attained EEDI compared to reference value at different phases
It is shown that, the proposed dual-fuel engine operated by (98.5% NG and 1.5% MDO) will
comply with the required IMO phases now and in the future as the attained EEDI is about 61%, 69%
and 79% of the reference EEDI at phase 1, phase 2 and phase 3, respectively. On the other hand, the
proposed dual-fuel engine operated by (95% Methanol and 5% MDO) will comply with IMO phase
1 and phase 2 as it is about 77% and 87% of the reference EEDI value, respectively. While it will
comply with the required IMO phase 3 by a small percentage, as the attained EEDI will reach 99.5%
of the required EEDI.
15.89
14.30
12.71
11.12
0
5
10
15
20
25
30
050000 100000 150000 200000 250000 300000 350000
REFERENCE EEDI (gCO2/DWT.NM)
CONTAINER SHIP DEADWEIGHT
Baseline
Phase 1 (2015-2019)
Phase 2 (2020-2024)
Phase 3 (2025-onwards)
Case study
75%
55%
70%
83%
61%
77%
94%
69%
87%
107%
79%
99.5%
0%
20%
40%
60%
80%
100%
120%
SSDE (MDO) DFE (98.5% NG+1.5%
MDO)
DFE (95% Methanol+5%
MDO)
Relative attained EEDI compared to
reference value, %
Baseline EEDI phase 1 EEDI phase 2 EEDI phase 3
Reference EEDI
3rd International conference of Chemical, Energy
and Environmental Engineering
July 2021 Egypt Japan University of Science and
Technology, Alexandria, Egypt.
Conclusions
The application of dual-fuel engine operated by natural gas or methanol on A15-class container ship
has been investigated from environmental and energy efficiency point of view. The main conclusions
from the current study are:
• From environmental point of view, using dual-fuel engine operated with 98.5% NG and 1.5%
MDO will comply with the required IMO emissions regulations. This will lead to reductions in
CO2, SOx, and NOx emissions by 28%, 98% and 85%, respectively when compared with their
values for SSDE operated by MDO (0.5%S). While the another proposed dual-fuel engine
operated by 95% Methanol and 5% MDO will lead to reductions by 7%, 95% and 80%,
respectively. Furthermore, the dual-fuel engine operated by natural gas and methanol will be
compliant with the required IMO limit if the percentage of pilot fuel is lower than 8.8% and 6.4%,
respectively.
• From energy efficiency point of view, the dual-fuel engine operated by (98.5% NG and 1.5%
MDO) will comply with the required IMO EEDI phases now and in the future. On the other hand,
the dual-fuel engine operated by (95% Methanol and 5% MDO) will comply with IMO EEDI
phase 1, phase 2, and phase 3 by about 77%, 87%, and 99.5% of the reference EEDI value,
respectively.
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