Redução de Emissão

1. Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748
http://dx.doi.org/10.2478/IJNAOE-2013-0209
pISSN: 2092-6782, eISSN: 2092-6790ⓒSNAK, 2014
Eco-friendly selection of ship emissions reduction strategies
with emphasis on SOx and NOx emissions
Ibrahim S. Seddiek1,2
and Mohamed M. Elgohary1,3
1
Department of Marine Engineering, Faculty of Maritime Studies,
King Abdulaziz University, Jeddah, Saudi Arabia
2
Department of Marine Engineering Technology, Arab Academy for Science,
Technology & Maritime Transport, Alexandria, Egypt
3
Department of Naval Architecture and Marine Engineering,
Faculty of Engineering, Alexandria University, Alexandria, Egypt
ABSTRACT: Increasing amounts of ships exhaust gases emitted worldwide forced the International Maritime Orga-
nization to issue some restricted maritime legislation for reducing the adverse environmental impacts arising from such
emissions. Consequently, ships emission reduction became one of the technical and economical challenges that facing
the ships,
operators. The present paper addresses the different strategies that can be used to reduce those emissions,
especially nitrogen oxides and sulfur oxides. The strategies included: applying reduction technologies onboard, using of
alternative fuels, and follows one of fuel saving strategies. Using of selective catalytic reduction and sea water scrub-
bing appeared as the best reduction technologies onboard ships. Moreover, among the various proposed alternative
fuels, natural gas, in its liquid state; has the priority to be used instead of conventional fuels. Applying one of those
strategies is the matter of ship type and working area. As a numerical example, the proposed methods were investigated
at a high-speed craft operating in the Red Sea area between Egypt and the Kingdom of Saudi Arabia. The results ob-
tained are very satisfactory from the point of view of environment and economic issues, and reflected the importance of
applying those strategies.
KEY WORDS: Alternative fuels; High speed craft; Fuel cost; International maritime organization (IMO); Selective cat-
alytic reduction; Ship emissions.
ABBRIVIATION
CO2 Di-oxide MDO Marine diesel oil
CO Mono-oxide MGO Marine gas oil
EES Engineering equations solver NG Natural gas
EU European union NOx Nitrogen oxides
HC Hydrocarbons PM Particulate matter
LNG Liquefied natural gas SCR Selective catalytic reduction
Corresponding author: Ibrahim S. Seddiek, e-mail: isibrahim@kau.edu.sa
This is an Open-Access article distributed under the terms of the Creative Commons
Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0)
which permits unrestricted non-commercial use, distribution, and reproduction in any
medium, provided the original work is properly cited.

2. 738 Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748
IMO International maritime organization SECAs Ship emissions control areas
MARPOL Marine pollution SOx Sulfur oxides
MEPC Marine environment protection committee
INTRODUCTION
All over the study of properties, advantages and drawbacks of the different conventional marine fuels (Diesel oil and heavy
fuel oil) , it can be showed that the traditional liquid marine fuels have worked competently through the most recent decades,
particularly with regard to adaptability, performance, safety and the compliance with the emissions regulations. But in the last
few years, some troubles have appeared due to its use, these include: the barriers of compliance with the new emissions re-
gulations (Fotis et al., 2014), the increase of the fuel cost, which presents the main element in the ships operating cost (Banawan
et al., 2013) and finally the sustainability issue (Seddiek et al., 2013). Uncontrolled emissions from burning traditional marine
fuel oils onboard ships have a significant impact upon our environment, especially with increase quantity of ship emissions:
Nitrogen oxides (NOx), Sulfur oxides (SOx), Di-oxide (CO2 ), Mono-oxide (CO), Particulates Matter (PM) and Hydrocarbons
(HC) (Welaya et al., 2013). A more comprehensive review was recently carried out by various organizations which are con-
cerned with air pollution and discussed health and welfare impacts from burning the fuel oils and quantified the financial
benefits that result from reducing these emissions (Beecken et al., 2014). As a method toward ship emissions reduction,
nowadays, the IMO regulations pushed the ships to use expensive fuel type in Ship Emissions Control Areas (SECAs) and will
be forced to be worldwide by year 2020 (Herdzik, 2011). Moreover, Marine Environment Protection Committee (MEPC) in its
57th
session planned to reduce NOx emissions to the lowest level by year 2016. There is no doubt that this will effect negatively
in the ship economic due to the increase of operating cost, which encourage all who interest in marine field to search and
present different proposals to find a solution for this problem. Thus, many attempts are carried out to search for a solution for
that issue. The present paper discusses this issue from the point of view of statistics, regulations, and the proposed strategies for
achieving this target.
STATISTICSAND REGULATIONS OF SHIPS,
EMISSIONS
Several inventory studies suggested that in 2000, ocean-going ships have emitted around (600-900) thousands tones of CO2,
15% of all global NOx emissions and 4-9% of global SO2 emissions (Eyring et al., 2010). While in 2007, the quantity of gases
emitted from ships estimated to be 25 and 15 million tons of NOx and SOx respectively, and have estimated around 2.7% of all
global CO2 are attributable to ships (IMO, 2009). Other studies revealed that shipping-related PM emissions are responsible for
3-8% of global P.M 2.5 -related mortalities (Eide et al., 2013).
IMO regulations regarding nitrogen oxides had planned to achieve NOx emissions reduction through three Tiers. Tier I for
ships keel lay-down after 1January 2000, Tier II , for ships keel lay-down after 1January 2011, which requires achievement of
15% emissions reduction of Tier I, and lastly Tier III for ships keel lay-down after 1January 2016 with 85% emissions reduction
of Tier I (Lin and Lin, 2006). The current allowable NOx emission level according to IMO regulation depends on the speed
category of the engine and ranges from (17 g/kWh) for engine speed 130r/min to (9.984 g/kWh) for engine speed 2000r/min
(IMO, 2009). Annex VI regulations of Marine Pollution (MARPOL) prevention convention on sulfur oxide requiring a
maximum 3.50% content sience 1 January 2012 and 0.50% by 1 January 2020 globally. Moreover, Annex VI also imposed a
1.5% sulfur limit on marine fuels in Emission Control Areas (ECAs) effective since May 2006, this limit was reduced to 1.0%
sulfur effective from 1 July 2010 and will be further reduced to 0.1% sulfur beginning January 2015 (Gritsenko and Yliskyla,
2013; Herdzik, 2011). Regarding HC emissions; MEPC in its 57th
session (IMO, 2008a) showed the importance of decreasing
availability of halons gas in addition to prohibit any new installations containing ozone-depleting substances on all ships by year
2020. So, this session, presented amended regulation 14, for P.M emissions, which in conjunction with SOx limitations (as
minimizing of fuel sulfur content leads to reduction of PM emissions). Furthermore, MEPC 58th
session (IMO, 2008b)
introduced the Energy Efficiency Design Index (EEDI) as a theoretical measure for the mass of CO2 emitted per unit of
transport work (grams CO2 per ton nautical mile) but until now there is no certain mandatory limit (Seddiek et al., 2013).

3. Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748 739
METHODS OF SHIP EMISSIONS REDUCTION
To carry out ships emission reduction process, a set of techniques could be done separately or as a complex concept, inclu-
ding using of: emissions reduction technology, alternative fuels, and fuel saving strategies, as follows:
Ship emissions reduction based on applying reduction technologies onboard
Technologies for emissions reduction can be divided into three general areas: In -engine, Fuel -related and Exhaust cleaning
technologies. The most emissions reductions technologies are concerned with NOx and SOx emissions due to their bad effect
on the marine environment (Seddiek et al., 2013).
NOx emissions reduction technology
Many researches (Stationary, 2000; Andersson and Winnes, 2011; Lamas and Rodriguez, 2012; Lamas et al., 2013) showed
the possibility of achieving acceptable NOx emissions reduction. One of the old methods that used was adding water to the
liquid fuel (Genesis Engineering Inc., 2003). So, using the puriNOx product, who mix Lubrizol,
s proprietary additives with
liquid fuels to form a stable product may cause reduction of about 20% & 50% for NOx and P.M respectively (Stationary,
2000). Recently, it was shown by (Lamas et al., 2013) that several engine’
s internal modifications may achieve NOx reduction
by considerable percentage. Practically, Selective Catalytic Reduction (SCR) system is currently used onboard many ships and
considered the best efficient method of NOx reduction than the other methods due to its durability and compliance with most
commercial ships (Andersson and Winnes, 2011; Woodyard, 2004).
SOx emissions reduction technology
Some, attempts are carried out for improving of marine fuel oil regarding SOx emissions for a clean environment and for
keeping the running cost as low as possible. One of these attempts is mixing heavy fuel oil with thermal oil processed from
Waste Plastics, but practically it was too difficult due to some technical problems (Banawan et al., 2010). Worldwide concerns
about emissions of SOx emissions from marine vessels have created an impetus to replace high sulfur marine residual oil with
cleaner lower sulfur fuels. Two such fuels being discussed as substitutes for residual oil are Marine Gas Oil (MGO) and marine
diesel oil (MDO) (Bengtsson et al., 2011). Moreover, seawater scrubbing system appeared as an efficient SOx emissions
reduction (Andreasen and Mayer, 2007). Widespread adoption of seawater scrubbing will likely be dependent upon satisfactory
resolution of the issue of its impact on water quality and ship operating cost (Johansson et al., 2013). The IMO MARPOL
regulations, the European Union (EU) regulations and the US EPA regulations are aligned except on some points of detail.
They all allow for equivalents and so permit the use of Exhaust Gas Cleaning Systems (EGCS), which are called scrubbers.
They have to achieve the same limits on SOx content of the exhaust whatever fuel is burnt as if the ship was burning fuel with a
sulfur content less than 0.1%. Each scrubber also has to be approved as an equivalent by the flag administration of the vessel so
some different flag state requirements may apply.
Other emissions reduction technology
In addition to the technologies used to reduce both NOx and SOx, there are some other technologies which are used for
other pollutants such as P.M, CO2 and HC. A less concern is paid for those pollutant comparative with NOx and SOx emissions.
This is due to the fact that NOx and SOx emissions have the higher negative effect towards environment and human health
issues. The most common technologies used for PM emissions reductions are using of: low sulfur fuel oil, and catalyzed
particulate filter (Daniel et al., 2012). CO emissions reduction achieved through improving the process of fuel combustion
inside the engines to insure the complete combustion process. Moreover, reduction of CO2 and HC will be achieved as a part of
whole ship’s emissions reduction technology (Seddiek et al., 2012; Banawan et al., 2013). Currently, a combined SCR systems
can be used for reducing NOx, CO, and HC emissions together. This systems work in two efficient stages, the oxidation stage
for CO and HC emissions reduction and the SCR stage provide NOx emissions reduction. Applying the basic or combined SCR
system is the matter of economic considerations and the essential of a certain emissions reduction. Table 1 summarizes the
average emissions reduction percentages as a result of using the mentioned and other emissions reduction technologies for
marine diesel engines.

4. 740 Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748
Table 1 Available methods for reducing ship emissions (Buhaug et al., 2009; EPA, 2009; Ariana et al., 2006; Woodyard, 2004).
Component Reduction method Potential reduction
NOx
Selective catalytic reduction (SCR) 95%
Emulsification 20-25%
Humid air 70%
Engine tuning 50-60%
Exhaust gas re-circulation 10-30%
SOx
Fuel Switching Process* 60-90%
Sea water scrubbing, Exhaust below water line Up to 95%
CO2 Energy Management 1-10%
PM Electrostatic filters Up to 85%
*Switching from residual fuel to distillate fuel
Ships emissions reduction based on using of alternative fuels
The main alternative marine fuel types may be found in two forms - liquid and gaseous fuels. Liquid marine alternative
fuels include: Methanol, Ethanol, and Bioliquid fuel, among them methanol has the promise to use for marine application in the
future (Kolwzan et al., 2012). On the other hand, the main alternative gasses fuels include: Hydrogen, Propane, and natural gas.
Among the previous types, Hydrogen and natural gas showed many attempts to applied onboard ships, and more emphasis on
those fuels regarding their characteristics can be illustrated as follows:
Hydrogen
A variety of alternative hydrogen energy production technologies are available in practice, including: Steam reforming, Off-
gas cleanup, Electrolysis Photo process, thermo chemical process and Partial oxidation of hydrocarbons (Hagh, 2004). Until
now the use of hydrogen as a main fuel for marine power plants is very restricted due to some technical problems (Christos et
al., 2014).
Natural gas
The use of natural gas also offers a number of environmental benefits over other fossil fuels, particularly liquid fuels
(Elma et al., 2014; Seddiek et al, 2013; Banawan et al., 2010). The combustion of natural gas releases very small amounts of
sulfur dioxide and nitrogen oxides, virtually no ash or particulate matter and lower the levels of carbon dioxide, carbon
monoxide, and other reactive hydrocarbons (Bengtsson, 2011). Many researchers showed the possibility of using natural gas
for marine application either for ships powering system (El-Gohary, 2012; El-Gohary and Seddiek, 2013) or for electric
generation, using fuel cells (Welaya et al., 2011; 2013). The compression had been presented by (Radwan et al., 2007;
Banawan et al., 2010) among the most marine alternative fuels and the other one, which was presented by (Bengtsson et al.,
2011) between current onboard fossil fuel and liquefied natural gas indicated that NG considers the best alternative fuel for
marine applications.
Ships emissions reduction based on fuel saving strategies
Several studies, aiming to saving and reducing fuel consumption and consequently exhaust gases emissions onboard ships,
have shown that there are different methods to achieve that. The present section describes some of the main strategies which
may be applicable onboard ships in order to achieve maximum fuel saving.

5. Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748 741
Ship resistance reduction
Ship's fuel consumption is a part of ship's powering calculation, which depends mainly on the ship's resistance. There are
many options to reduce ship resistance, such as anti-fouling, ship's weight reduction as traditional methods (Apostolos, 2010;
TAYLAN, 2010; Philippe, 2009) and air bubbles as a new concept (Winkler, 2009). Each method of them can contribute by
different fuel saving percentages according to ship type.
Renewable energy
Although there is a high degree of preference for renewable energy over fossil fuels as energy source for ship power, the
study of development of a renewable infrastructure for marine transportation is still in the first steps. Wind energy, Solar energy,
Wave energy, and Hydrogen combustion present the most common sources of renewable energy that may be used onboard
ships (Alexandros et al., 2010; Mekhilef et al., 2011).
Energy performance improvement
The contribution of marine power plant efficiency in issue of fuel saving may be achieved through fuel quality
improvement and engine tuning process (Rosli, 2008; Fredrik, 2008). Engine tuning process can be achieved through tuning of
fuel system, air system, and exhaust system.
Energy conservation management
In the maritime field, energy conservation and management processes onboard ships are made more efficient, concerning
the fuel to help stretch the fuel budget as far as possible and make ships more environmentally friendly (Oihane et al., 2012;
Gerasimos and George, 2013; Kjeld, 2009; Elgohary, 2009). One of the new proposed waste heat recovery application was
presented by (Seddiek et al., 2012), which showed the possibility of using exhaust gases to operate absorption air condition unit.
Reduce ship speed
Fuel consumption and the amount of ships exhaust gas emissions are in direct relation. Consequently, saving any amount of
ship fuel consumption will affect positively on marine environment (Harilaos et al., 2009). Furthermore, with the continuous
fuel price increment, some companies forced to reduce their ships speed (Shuaian and Qiang, 2012). An estimate of fuel saving
percentage as a result of speed reduction was introduced and expressed by (Banawan et al., 2013):
Shore side power connection
A huge amount of fuel is consumed by auxiliary engines at the ports. (P.M) emissions are responsible for approximately
60000 cardiopulmonary and lung cancer deaths annually, with most of those deaths occurring along the coasts (Yang et al.,
2011). Shore power connection system used to saving the quantity of fuel consumption through ships berthing periods. The
economical and environmental benefits due to applying of shore power connection were demonstrated by (Hall, 2010; Seddiek
et al., 2013).
CHOICE OF THE SUITABLE EMISSIONS REDUCTION METHOD
There are many factors affecting choice of the suitable ship emissions reduction method which include ship type, power
rating, economic issue, adaptability, and compliance with the current and future emission regulations. As a case study, the
present paper handling this factors in case of applying the previous methods onboard high speed passenger ships Choice of
these types is the matter of power rating which conjuncts directly with the amount of exhaust gas emitted from ships.
Moreover, these ships call ports on more regular basis in short time compare to any other ships which make them more effect
in the health of population at the areas near from ports. According to the nature of ships,
operating and based on the previous
researches, carried out by (Elma et al., 2014; Christos, 2014; Johansson et al., 2014) using of alternative fuels and emission
reduction technologies seem the most suitable methods to be applied for passenger ships, especially from the point of view of
applicability.

6. 742 Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748
CASE STUDY
In recent years, the number of short-voyage passenger ships sailing in the Red Sea area has increased. There is no doubt that
these ships have contributed to develop maritime transport in this area. On the other hand, it was shown by (Seddiek et al., 2012;
Seddiek et al., 2013) that the high power of these ships contributed to the increasing gaseous emission rate and affect adversely
on the environment in this area. The present paper discusses the viability of applying the mentioned two methods onboard one
of the high-speed crafts operating in the Red Sea area, called Alkahera, as shown in Fig. 1. The ship operates between Hurghada
port in Egypt and Duba port in the Kingdom of Saudi Arabia. The ship's technical data is summarized as shown in Table 2.
Fig.1 High-speed craft Al-Kahera.
Table 2 M/V Alkahera main technical data.
Item Description
Propulsion Four steerable / Reversing water jets
Classification society Germanischer Lloyd (GL)
Passengers 1200
Vehicle capacities 120 Cars plus 15x 15tone trucks
Service Speed (90% MCR, fully loaded) 34 knots
Main engines 4x MTU 20V 8000 M71R
Main engine fuel consumption 1,200 Lit @ MCR
Engine power 4x 7,200 kW @ 1,150 rpm ± 1.5%
Generating sets 4x MAN D2866 LXE LSAM 46.2 VL12 228 kW @ 1500 RPM
Number of trips 200 per year
Sailing & maneuvering time 8 h per trip
Applying emissions reduction technologies
Fig. 2 shows a simple scheme for emissions reduction model, which can be installed onboard the case. It consists of SCR
system for NOx emissions reduction , followed by sea water scrubber system. The present study had been relied on the
characteristic and performance of ship’s main engines, SCR system, and Scrubber system. All data were computed using
Engineering Equations Solver (EES) program for environmental and economic results.

7. Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748 743
Fig. 2 Simple model of main components for SCR & water scrubber system inside engine room.
To evaluate the importance of installation of SCR and sea water scrubber system from the view point of environment; quan-
tity of ship's emissions that could be reduced in case of applying these systems may be estimated from the following equation
for both NOx and SOx emissions.
f f p TERQ L E R P t= ⋅ ⋅ ⋅ ⋅ (1)
where ( ERQ ) emission reduction quantity is ( fL ) is load factor, ( fE ) is emission factor, ( pR ) is emissions factor reduction
percentage due to installation of SCR, ( P ) engine power rating, ( Tt ) ship sailing time. On the other hand, the main draw-back
of applying these systems is the additional annual costs. Economically, applying SCR system will show some extra costs
including: Urea consumption, investment costs , running costs (urea) and maintenance cost . Moreover, the main component of
the catalyst requires rebuilding depending on the type of fuel during operation. There is noticeable uncertainty concerning the
time estimate; this study assumes a grim window of 5 years and these costs may be expressed as follows:
[ ]
[ ]
1
1 1
N
i C O MN
i i
ACI C F C C
i
+
= + +
+ −
∑ ∑ (2)
where ( iC ) is total capital installation cost, which depends on fuel sulfur content, ( N ) ship working years after installation, ( i )
interest percent, ( OC ) annual maintenance cost , ( CF ) fuel cost increment in case of using marine gas oil, ( MC ) annual
operating cost. Take into consideration that the life time of SCR will depends on sulfur content.
Applying alternative fuels
Discussion of using alternative fuels as a strategy for ship emissions reduction revealed that natural gas appears as the most
common alternative fuel onboard ships. One of the most outcomes of applying this strategy is the environmental benefit, which
may be quantified as follows:
1 2fDO fDO fNG fNG fDO fDO TERQ L E C L E C L E P t = ⋅ − ⋅ ⋅ + ⋅ ⋅ ⋅  (3)
where fDOL and fDOE are load factor, emission factor in case of diesel engines. So, fDOL and fNGE are load factor, emission

8. 744 Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748
factor for natural gas, while 1C and 2C are percentage of diesel oil and natural gas in case of dual-fuel engines. It should be
taken into consideration that using of natural gas will be during sailing only. The typical exhaust gas compositions of burning
diesel fuel inside marine internal combustion engine can be tabulated as shown in Table 3. Moreover, consumed power, specific
fuel consumption, and emissions Factors of diesel and dual-fuel natural gas engines can be illustrated as shown in Table 4
(Banawan et al., 2010; Seddiek et al., 2013).
To adapt the diesel engine to dual-fuel (diesel -methane) engine, a conversion process should be carried out. This includes
modification of the main engines parts such as (fuel injector, piston, and valves). In addition, adding NG supply system
including NG storage spaces, supply piping and valves, gas detection units and alarms, exhaust ventilation system, and other
minor components. Cost analysis of using natural gas, in form of Liquefied Natural Gas (LNG): instead of diesel oil onboard
ships it depends on some essential items, including the present and future of diesel fuel prices trend, cost of conversion onboard
diesel engine to dual-fuel engine and the difference in maintenance, operation and bunkering costs.
Table 3 Typical composition of exhaust gases.
Component N2 O2 CO2 H2O NOx SOx CO HC Dust
% 77.50 13.75 6.25 0.025 0.212 0.17 0.005 0.005 0.0075
Table 4 Engines data and emissions factors.
Engine emission factor[g/kWh]Fuel consumption/EnginePower(kW)
@85%
Engine Mode
HCPM10NOxCOSOxCO2NG(m3
/h)D.O(m3
/h)
0.530.5513.431.682.562698Nil1.0206120
Onboard diesel
engine
0.9010.0152.590.5970.255312200.056120
Natural gas
dual-fuel
The annual saving or increment cost [ ACI ] due to shifting to natural gas may be expressed as follows:
[ ]
[ ]
&
1
1 1
N
M O A N
i i
ACI FSC SC C Bunkering cost
i
+
= + − ⋅ − ∆
+ −
∑ (4)
where, ( AC ) the capital cost of conversion from diesel oil to dual-fueled engine, ( N ) is the expected working years after
conversion process, (i ) annual interest ( FSC ) the difference between fuel cost of diesel and natural gas, (∆ bunkering) is the
difference cost between ship bunkering process of diesel oil and NG and ( &M OSC ) the difference between maintenance and
operating cost of diesel and natural gas engines. Moreover, annual fuel cost difference ( FSC ) could be estimated as follows:
[ ]. . . ..OD O D O T p LNG LNG p D O D O TFSC sfc fc P t LNG sfc fc D sfc fc P t = ⋅ ⋅ − ⋅ ⋅ + ⋅ ⋅ ⋅  (5)
where, ( .D Osfc ), and ( .D Ofc ) are specific fuel consumption, and fuel cost of diesel fuel oil. ( LNGsfc ), ( LNGfc ), and ( . pD O ) are
specific fuel consumption, fuel cost, diesel oil percent in case of dual-fuel. LNG fuel cost is different from area to other
worldwide taking various factors into account such as cost of production, liquefaction, logistic, and bunkering process. The fuel
price, in 2013, was about 11-12 USD/mmBTU for LNG (Harsema, 2013) and nearly 20 USD/mmBTU for marine diesel oil
(Bunker world, 2014). Figs. 3 and 4 represent the environmental and economic outcome due applying the emissions reduction
strategies. It can be noticed that applying of those strategies will achieve nearly the same emission reduction regards NOx,
SOX, and P.M emissions. On the other hand, LNG will achieve more CO2 reduction and cause more HC emissions as shown
in Fig. 3.

9. Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748 745
As the present paper emphasis on SOx and NOX emissions; using of the basic type of SCR (which designed mainly for
NOx emissions) will be considered rather than using of the combined system which is more expensive than the basic system.
From Fig. 3 it can be noticed that the higher NOx emissions reduction percentage could be done through using of (SCR + MGO)
system, while applying of (SCR + Sea water scrubber) system which may achieve maximum SOx and HC emissions reduction.
On the other hand using of natural gas as alternative fuel will contribute in reducing CO2 emissions more than any other pro-
posed system. A part of this conclusion is due to the fact that NG has lower Carbone content than diesel oil and consequently
the combustion of these products of it will contain less CO2 emissions. On the other hand, HC emissions will increase when
using NG instead of diesel oil as the main fuel in internal combustion engines, since diesel engines are operated at a much
leaner mixture than NG engines are, especially for converted engines (Banawan et al., 2010).
Fig. 3 Ship’s emission reduction @ various strategies.
Economically, Fig. 4 presents the average cost saving or increment due to applying the proposed emissions reduction
strategies. From the Figure it can be excluded that using of natural gas as an alternative fuel, in LNG form, will be economically
either without or with adding the conversion cost. As shown; applying LNG fuel for main engines can achieve annual cost
saving of 50 and 18 ($/kW) in case of LNG without and with adding conversion cost, respectively. Conversely, both SCR with
MGO (of 0.1% sulfur content ) and SCR with sea water scrubber systems will cause increasing of the annual ship operating
cost by about 35 and 45($/kW) , respectively.
Fig. 4 Ship’s Cost saving @ various strategies.

10. 746 Int. J. Nav. Archit. Ocean Eng. (2014) 6:737~748
CONCLUSION
Emissions from ships represent one of the important issues that concern those interested in maritime domain, as it has a
negative impact on the marine environment. The present paper discussed the various methods which could carry out to reduce
those emissions. Using of SCR and water scrubber systems as treatment technology onboard ships or natural gas as alternative
fuel appeared as the best methods from the point view of environmental. Applying one of them depends on some criteria such
as the required emission reduction percentage. Those methods were studied to be used for one of passenger ships working at the
Red Sea. The results showed the possibility to achieve valuable emission reduction percentage by using of SCR and scrubber
systems, but it will be costly and add more ship operating cost. On the other hand, using of LNG as alternative fuel will con-
vince from the view point of environmental and economic issues.
ACKNOWLEDGEMENT
This work was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant no.
(980-118 -D1435). The authors, therefore, acknowledge with thanks DSR technical and financial support.
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