Lauri Laatikainen 

Assessing Wärtsilä’s exhaust gas abatement 
solution 

Life cycle assessment of a SOx scrubber system 

 

 

 

 

 

 

 
  

School of Technology and Innovations 
Master’s thesis 

Industrial Systems Analytics  

Vaasa 2024 



2 

UNIVERSITY OF VAASA 
School of Technology and Innovations 

Author: Lauri Laatikainen 
Title of the thesis:  Assessing Wärtsilä’s exhaust gas abatement solution: Life cycle as-

sessment of a SOx scrubber system 
Degree: Master of Science 
Discipline: Industrial Systems Analytics  
Supervisors: Petri Helo, Bening Mayanti 
Year: 2024 Pages: 79 

ABSTRACT :  
Wärtsilä offers competent technical solutions for complying with the sulphur content regulations 
set by the IMO. Wärtsilä’s exhaust gas cleaning systems are a viable option for ship owners and 
operators that prefer to continue operating their vessels with fuels with a sulphur content of 
over 0,5% m/m. As the number of environmental regulations on maritime traffic and related 
industries is likely to increase in the near future, a proactive approach can yield beneficial results 
for companies looking to offset the impact of potential future restrictions. 
 
In this study, a life cycle assessment of a Wärtsilä V-SOx hybrid scrubber system was conducted. 
The used methodology followed the principles and framework demonstrated in the ISO 14040 
standard. The main objective of the study was to generate information about the environmental 
impacts of the scrubber system throughout its life cycle. The results were to be used to initiate 
the process of developing environmental KPIs to monitor and improve Wärtsilä’s environmental 
performance. Also, the study was conducted to support Wärtsilä’s efforts to decarbonize its own 
operations by 2030. 
 
The studied scrubber system was installed on a tanker vessel in 2019. The life cycle inventory for 
the LCA was built using data from Wärtsilä’s internal databases, scientific literature and docu-
mentation provided by the customer. The impacts were assessed with the ILCD 2011 midpoint+ 
method, which contains the impact categories recommended by the European Joint Research 
Centre.  
 
Most of the potential environmental impacts occurred during the operational phase. The raw 
material extraction & manufacturing of components phase produced the second highest poten-
tial impacts. These phases combined produced more than 98% of the potential impacts in each 
measured impact category except for the freshwater ecotoxicity category. 
 
The system had been operated mostly in open loop mode, and therefore an additional scenario 
analysis was conducted to get an overview of the potential environmental impacts of operating 
the system in closed loop mode. Although contributing less to marine eutrophication, closed 
loop operation was found to produce a significant number of indirect impacts in all the other 
impact categories. For example, the production of sodium hydroxide used in closed loop opera-
tion multiplied the potential CO2 emissions in both additional scenarios. 
 
In addition to direct environmental impacts, the LCA produced significant insight to the indirect 
impacts behind the processes that are connected to the system’s life cycle. As the responsibility 
of mitigating environmental burden through regulations will likely extend to affect more opera-
tors in supply chains, Wärtsilä is taking proactive steps to find various ways of improving its 
environmental performance. 

KEYWORDS: Life cycle assessment, Maritime sustainability, Exhaust gas scrubbing 



3 

VAASAN YLIOPISTO 
School of Technology and Innovations 

Tekijä: Lauri Laatikainen 
Tutkielman nimi:  Wärtsilän pakokaasunpuhdistustekniikan arviointi: Rikkipesurin 

elinkaariarviointi 
Tutkinto: Diplomi-insinööri 
Oppiaine: Industrial Systems Analytics  
Ohjaajat: Petri Helo, Bening Mayanti 
Valmistumisvuosi: 2024 Sivumäärä: 79 

TIIVISTELMÄ :  
Wärtsilä tarjoaa tehokkaita teknisiä ratkaisuja IMO:n asettamien rikkipitoisuusmääräysten 
noudattamiseen. Wärtsilän pakokaasunpuhdistusjärjestelmät ovat pätevä vaihtoehto 
laivanomistajille ja operaattoreille, jotka haluavat jatkaa alustensa toimintaa polttoaineilla, 
joiden rikkipitoisuus on yli 0,5% m/m. Koska meriliikennettä ja siihen liittyviä toimialoja 
koskevien ympäristömääräysten määrä todennäköisesti lisääntyy lähitulevaisuudessa, 
ennakoiva lähestymistapa voi tuottaa hyödyllisiä tuloksia yrityksille, jotka haluavat lieventää 
mahdollisten tulevien määräysten vaikutuksia.  
 
Tässä työssä suoritettiin elinkaariarviointi Wärtsilän V-SOx hybridijärjestelmälle. Käytetty 
metodologia noudatti ISO 14040 – standardin toimintaperiaatteita ja viitekehystä. Tutkimuksen 
päätavoitteena oli tuottaa tietoa järjestelmän ympäristövaikutuksista koko sen elinkaaren 
ajalta. Tuloksia käytettiin käynnistämään ympäristöindikaattoreiden kehitysprosessi, joiden 
tarkoituksena on seurata ja auttaa parantamaan Wärtsilän ympäristötehokkuutta. Työn 
tarkoituksena oli myös tukea Wärtsilän vuodelle 2030 asettamaa hiilineutraalisuustavoitetta. 
 
Tutkimuksen kohteena ollut pesurijärjestelmä asennettiin erääseen säiliöalukseen vuonna 2019. 
Elinkaari-inventaario rakennettiin käyttäen Wärtsilän sisäisiä tietokantoja, tieteellistä 
kirjallisuutta ja asiakkaan toimittamaa dokumentaatiota. Ympäristövaikutukset arvioitiin ILCD 
2011 midpoint+ menetelmällä, joka sisältää Euroopan yhteisen tutkimuskeskuksen 
suosittelemat vaikutusluokat. 
 
Valtaosa potentiaalisista ympäristövaikutuksista syntyi käyttövaiheen aikana. Raaka-aineiden 
louhinta & komponenttien valmistusvaihe tuotti toiseksi eniten potentiaalisia 
ympäristövaikutuksia. Nämä vaiheet tuottivat makean veden ekomyrkyllisyysluokkaa 
lukuunottamatta yli 98% potentiaalisista vaikutuksista jokaisessa mitatussa vaikutusluokassa.  
 
Järjestelmää oli käytetty pääosin avoimen kierron tilassa, minkä vuoksi suoritettiin ylimääräinen 
skenaarioanalyysi yleiskuvan saamiseksi suljetun kierron käytön mahdollisista 
ympäristövaikutuksista. Vaikka suljetun kierron toiminnalla oli vähemmän vaikutusta 
merialueiden rehevöitymiseen, sen havaittiin aiheuttavan huomattavan määrän epäsuoria 
vaikutuksia kaikissa muissa mitatuissa vaikutusluokissa. Suljetun kierron operaatiossa 
käytettävän natriumhydroksidin tuotanto esimerkiksi moninkertaisti potentiaaliset CO2  päästöt 
molemmissa lisäskenaarioissa. 
 
Suorien ympäristövaikutusten lisäksi työ tuotti merkittävää näkemystä järjestelmän elinkaareen 
liittyvien prosessien taustalla olevista välillisistä vaikutuksista. Koska vastuu ympäristöstä tulee 
todennäköisesti koskettamaan yhä useampaa toimijaa tulevaisuudessa, Wärtsilä tekee 
ennakoivia toimenpiteitä löytääkseen erilaisia tapoja parantaa ympäristötehokkuuttaan. 

AVAINSANAT: Elinkaariarviointi, Kestävä merenkulku, Pakokaasun puhdistus 



4 

Contents  

1 Introduction 9 

1.1 Purpose of the study 10 

1.2 Structure of the study 12 

2 Wärtsilä 13 

2.1 Wärtsilä businesses 14 

2.1.1 Wärtsilä Exhaust Treatment 16 

2.1.2 Wärtsilä Exhaust Treatment SOx abatement solutions 16 

3 Theoretical background 21 

3.1 IMO regulatory framework 21 

3.1.1 Annex I 22 

3.1.2 Annex II 23 

3.1.3 Annex III 24 

3.1.4 Annex IV 24 

3.1.5 Annex V 25 

3.1.6 Annex VI 26 

3.2 Life cycle assessment 29 

3.2.1 Life cycle of a Wärtsilä V-SOx scrubber 31 

3.2.2 Prior works 32 

4 Methodology 35 

4.1 Goal and scope 35 

4.2 Inventory analysis 39 

4.2.1 Raw material extraction and manufacturing of components 40 

4.2.2 Transportation from supplier to shipyard 42 

4.2.3 Operational phase 43 

4.2.4 End-of-Life 47 

4.2.5 Inventory data uncertainties 48 

5 Impact assessment and interpretation of results 51 

5.1 Environmental impacts of life cycle phases 51 



5 

5.2 Scenario analysis 57 

5.3 KPI development 62 

5.3.1 Managerial implications 66 

6 Conclusions 68 

6.1 Recommendations for reducing environmental impacts 69 

6.2 Limitations 71 

References 72 

Appendices 79 

Appendix 1. LCIA impact categories and their measurement units 79 

  



6 

Figures  
 
Figure 1. Wärtsilä V-SOx scrubber body with a venturi (Suopanki, 2021, p. 429) 12 

Figure 2. Wärtsilä Exhaust Treatment scrubber design family (Wärtsilä, n.d. -j). 17 

Figure 3. Wärtsilä open loop scrubber system (Wärtsilä, 2017, p. 4) 18 

Figure 4. Wärtsilä closed loop scrubber system (Wärtsilä, 2017, p. 5). 19 

Figure 5. Wärtsilä hybrid scrubber system (Wärtsilä, 2017, p. 6) 20 

Figure 6. Emission Control Areas (Rymaniak et al. 2018, p. 2). 26 

Figure 7. Annex VI fuel oil SOx content limitations over time (Čampara et al. 2018). 27 

Figure 8. MARPOL Annex VI NOx emission limits (Deng et al. 2021, p. 4) 28 

Figure 9. Stages and example applications of LCA (ISO, 2006). 30 

Figure 10. LCA System boundary 36 

Figure 11. LCIA steps from inventory to category endpoints (JRC, 2010a, p. 108) 37 

Figure 12. LCIA results as contribution percentages per phase. 54 

Figure 13. Top impact contributors in the raw mat. extraction & component 

manufacturing phase. 56 

Figure 14. Additional scenario 1 LCIA results as contribution percentages per phase. 58 

Figure 15. Additional scenario 2 LCIA results as contribution percentages per phase. 59 

Figure 16. Marine eutrophication impact category results for each scenario. 60 

Figure 17. Climate change impact category results for each scenario. 61 

Figure 18. Contribution percentages of different transportation methods to selected 

impact categories. 64 

Figure 19. GHG Protocol scopes and emissions across the value chain (WRI/WBCSD, 

2011, p. 5). 70 

 

Tables 
 
Table 1. Categorization system for pollution caused by noxious and liquid substances 

(IMO, n.d. -f). 23 

Table 2. Recommended methods and their classification at midpoint (JRC, 2010b). 38 

Table 3. Data collection methods and data quality in each life cycle phase. 40 

Table 4. Scrubber operating modes as percentages of total system running hours. 44 



7 

Table 5. Water consumption on different operating modes. 45 

Table 6. Operating modes. 45 

Table 7. End-of-life activity processes for each material. 48 

Table 8. Impact assessment results per functional unit. 53 

 

Abbreviations  

AE   Auxiliary engine 
CCS   Carbon capture and storage 
CEMS   Continuous emission monitoring system 
CH4   Methane 
CL   Closed loop 
CO2   Carbon dioxide 
ECA   Emission control area 
EFP   Environmental footprint 
EGC   Exhaust gas cleaning 
EoL   End-of-life 
FU   Functional unit 
GHG   Greenhouse gas 
GW   Gigawatt 
GWP   Global Warming Potential  
HC   Hydrocarbon 
HFO   Heavy fuel oil 
ILCD   International Life Cycle Data System 
IMO   International Maritime Organization 
ISO   International Organization for Standardization 
JRC   European Joint Research Centre 
KPI   Key performance indicator 
kW   Kilowatt 
kWh   Kilowatt-hour 
LCA   Life cycle assessment 
LCIA   Life cycle impact assessment    
LNG   Liquefied natural gas 
MCR   Maximum continuous rating 
ME   Main engine 
MGO   Marine gas oil 
Mg(OH)2  Magnesium hydroxide 
MW   Megawatt 
m/m   Mass by mass 
NaOH   Sodium hydroxide 
NOx   Nitrogen oxide 
OFB   Oil-fired boiler 
OL   Open loop 



8 

PAH   Polycyclic aromatic hydrocarbon    
PM   Particulate matter 
ppm   Parts per million 
SCR   Selective catalytic reduction 
SOx   Sulphur oxide 
STH   Sustainable Technology Hub 
Tkm   Tonne-kilometre 
VOC   Volatile organic compound  



9 

1 Introduction 

The volume of maritime transport in global trade has increased substantially in the past 

decades. Between 1992 and 2012, the global maritime traffic grew by 400%, showing a 

slight period of stagnancy only during the 2008-2009 economic crisis (Tournadre, 2014, 

p. 7929). In the past 30 years, the global maritime trade has been growing annually by 

3.3% on average and today more than 80% of the global merchandise trade is trans-

ported by sea (UNCTAD, 2022, pp. 17, 24). According to forecasts based on varying sce-

narios of economic development, the global maritime traffic is expected to grow be-

tween 240-1200% by 2050 (Sardain et al. 2019, p. 276). 

 

Along with the positive impacts that the growing maritime traffic will likely have on 

global economic prosperity, concerns have also risen on its impacts on human health 

and the environment (Li et al. 2020, p. 1). In addition to the global maritime sectors 

significant amount of direct greenhouse gas emissions such as methane (CH4) and car-

bon dioxide (CO2), it is also a major source for sulphur oxide (SOx), nitrogen oxide (NOx) 

and particulate matter (PM) emissions (Wang & Wright, 2021, p. 456). These emissions 

are regulated by The International Maritime Organization (IMO), which is an agency of 

the United Nations that is specialized in the development and maintenance of the regu-

latory framework in the shipping industry (IMO, n.d. -a). 

 

Although the shipping industry emissions are being investigated and regulated holisti-

cally by the IMO, a special focus has been targeted on SOx emissions in the recent years. 

SOx emissions are harmful to human health and the marine environment and can ad-

versely impact air quality hundreds of kilometres away from the source of the emissions 

(Fan et al. 2021, pp. 1, 2). To tackle these impacts, the IMO has limited the sulphur con-

tent of the fuel used in ships down to 0.5% m/m (mass by mass) globally and 0.1% m/m 

in the specifically defined emission control areas (ECAs) (IMO, n.d. -b). However, the use 

of low-sulphur marine fuel is not the only solution to meet the requirements of the reg-

ulations.  

 



10 

Currently, there are two regulation abiding, technologically and economically feasible 

alternative solutions to using low-sulphur fuel: using alternative nonpetroleum-based 

fuel such as liquefied natural gas (LNG) or methanol or installing an exhaust gas cleaning 

(EGC) system that removes the sulphur from the exhaust gas (Solakivi et al. 2019, p. 339). 

The decision for choosing one of these solutions is often based on the operating profile 

of the vessel, its operating routes, and thorough comparative cost assessment. 

 

Currently, the environmental responsibility regarding maritime traffic is in most parts 

shared between ship owners and operators through regulations regarding the operation 

of the vessel. However, given the political pressure on environmental issues and growing 

environmental awareness amongst the public, it is reasonable to assume that in the fu-

ture this responsibility will be extended to affect each party involved in the life cycle of 

a vessel. Should such extension unfold, the operators involved in the marine industry 

supply chains might have to examine their own operations more precisely in terms of 

environmental and social sustainability. As in many other industries, in the marine indus-

try as well, the life cycle assessment method has been proven effective in forming a com-

prehensive view of the environmental impacts of a product or a process during its life 

cycle (Jang et al. 2020, p. 3). 

 

1.1 Purpose of the study 

This study is commissioned by Wärtsilä Finland Oy. Wärtsilä is the market leader for ex-

haust gas cleaning systems in the global commercial shipping industry and has been a 

major contributor in engineering and designing ship engines and parts for over 60 years 

(Wärtsilä, n.d. -a, n.d. -b). Wärtsilä offers a wide range of EGC systems for being compli-

ant with the IMO SOx regulations and is also developing carbon capture and storage (CCS) 

technology to answer to the increasing focus on reducing CO2 emissions in the shipping 

industry. 

 



11 

In addition to ensuring that their customers are compliant with the current and upcom-

ing IMO regulations, Wärtsilä has set environmental targets regarding their own opera-

tions. The company has committed to being carbon neutral in their own operations by 

2030 and by then also providing a product portfolio that is compatible with the use of 

carbon-free fuels (Wärtsilä, 2021). The fulfilment of these commitments requires Wärt-

silä to increase environmental awareness amongst the employees and to find feasible 

solutions to mitigate the environmental impacts of its operations. 

 

The main purpose of this study is to evaluate the environmental footprint of a Wärtsilä 

V-SOx hybrid scrubber system throughout its life cycle. The study is conducted to gain 

insight about the most significant environmental impacts that the system produces both 

directly and indirectly during its lifetime. In addition, the purpose of the study is to eval-

uate and determine the difference in the magnitude and quality of environmental im-

pacts between different operating modes of the system. 

 

The studied scrubber system is designed to remove SOx and other pollutants such as PM 

from the exhaust gas. In the V-SOx design, a single or multiple venturis are used as the 

inlet for the exhaust gas, depending on the configuration of the system (Suopanki, 2021, 

p. 428). A Wärtsilä V-SOx scrubber body and venturi design is shown in figure 1. The 

operating principles of the hybrid system and other Wärtsilä SOx scrubber systems are 

described in chapter 2.1.2. 

 

By commissioning this study, Wärtsilä has also expressed interest in developing and de-

termining key performance indicators for enhancing environmental performance in its 

EGC business. This study also has potential to help Wärtsilä to develop their EGC systems, 

identify new business opportunities and to make more sustainable decisions regarding 

the EGC supply chain. 

 



12 

 

Figure 1. Wärtsilä V-SOx scrubber body with a venturi (Suopanki, 2021, p. 429) 

 

1.2 Structure of the study 

The study is divided into six parts. The first part introduces the topic and purposes be-

hind of the study. The second part introduces the history of Wärtsilä as a company, Wärt-

silä Exhaust Treatment business unit and Wärtsilä’s SOx scrubber systems. The third part 

is the theoretical background, which describes the IMO regulatory framework, the LCA 

methodology, and previous scrubber system LCA studies. The fourth part is the method-

ology, which focuses on data collection and building the life cycle inventory using the 

LCA method. The fifth part is the impact assessment, in which the results of the LCA are 

presented and interpreted, and the KPI development is discussed. The sixth and final 

chapter is conclusions, which contains discussion about the results, recommendations 

for mitigating environmental impacts and conducting future research, and limitations of 

the study. 

  



13 

2 Wärtsilä 

Wärtsilä was founded in Tohmajärvi, Finland in 1834 (Wärtsilä, n.d. -b). The company 

started as a sawmill, but quickly adopted ironworks to its operations. In 1935, Wärtsilä 

acquired a majority holding of Kone- ja Siltarakennus Oy (Machine and Bridge Construc-

tion Ltd), which manufactured paper machines and locks among other products (Wärt-

silä, n.d. -b). The acquisition gave Wärtsilä control for the Hietalahti shipyard in Helsinki 

and the Crichton-Vulcan shipyard in Turku. In 1938, Kone- ja Silta group was fully merged 

with Wärtsilä. During the same year, Wärtsilä signed a licence agreement with Friedrich 

Krupp Germania Werft AG which led to the manufacturing of Wärtsilä’s first diesel en-

gine in 1942 (Wärtsilä, n.d. -b). 

 

In the following decades, Wärtsilä focused on designing and manufacturing its own die-

sel engines. Wärtsilä started its international manufacturing operations in 1978, after 

acquiring the majority of the NOHAB diesel business from a Swedish company called 

Bofors (Wärtsilä, n.d. -b). In 1986, Wärtsilä and a Finnish industrial company Valmet 

joined their marine resources together and as a result, Wärtsilä Marine Oy was formed 

(Wärtsilä, n.d. -b). In exchange for Valmet’s marine resources, Wärtsilä’s paper machines 

were transferred to Valmet. By the year 2002, Wärtsilä had expanded its diesel and gas 

engine operations and gained a foothold in the biopower field through acquiring a Finn-

ish boiler plant manufacturing company Sermet Oy (Wärtsilä, n.d. -b). 

 

Between 2003-2010, Wärtsilä expanded its operations globally and entered into sev-

eral joint ventures that included the production of propellers, the production of dual-

fuel engines for LNG carriers, and the integration of biopower operations with heat and 

power businesses (Wärtsilä, n.d. -b). From 2010 to 2020, Wärtsilä continued develop-

ing its marine and energy businesses towards more sustainable direction. In 2016-

2017, Wärtsilä entered into the solar energy business with solar photo-voltaic solutions 

and successfully tested remote control ship operating capability and wireless induction 

charging system in the marine environment (Wärtsilä, n.d. -b). 

 



14 

In 2018, Wärtsilä launched a major investment in building a new innovation and tech-

nology hub in Vaasa, Finland (Wärtsilä, n.d. -b). The building is named Sustainable Tech-

nology Hub (STH) and its construction was completed in 2022. The hub acts as a centre 

for research, product development and production, and its main purpose is to contrib-

ute to marine and energy decarbonization (Wärtsilä, n.d. -b). The electricity produced 

in engine test runs at STH is fed into the power grid and residue heat is stored and used 

in the building, thus contributing to Wärtsilä’s sustainable development targets (Wärt-

silä, n.d. -d).  

 

In 2021, Wärtsilä committed to being carbon neutral in its own operations by 2030 and 

introduced a new strategic framework called “The Wärtsilä Way” (Wärtsilä, n.d. -b). 

The new strategic framework defines the company’s core values as customer success, 

passion, and performance, and its purpose as “enabling sustainable societies through 

innovation in technology and services” (Wärtsilä, n.d. -c). The framework also defines 

the company’s target position as “shaping the decarbonization of marine and energy”, 

which according to the framework can be achieved by following and implementing 

Wärtsilä’s strategic priorities (Wärtsilä, n.d. -c). These strategic priorities are exceling in 

creating customer value, developing high performing teams that make a difference, 

driving decarbonization in marine and energy, capturing growth in services, and contin-

uously improving Wärtsilä’s end-to-end value chain (Wärtsilä, n.d. -c). 

 

2.1 Wärtsilä businesses 

Wärtsilä has 17,500 employees in 79 countries and the company’s net sales were 5,8 

billion euros in 2022 (Wärtsilä, n.d. -e). In 2023, Wärtsilä is operating in the energy and 

marine markets with four different businesses: Wärtsilä Energy, Wärtsilä Marine Power, 

Wärtsilä Marine Systems, and Wärtsilä Portfolio Business (Wärtsilä, n.d. -e). 

 

Wärtsilä Energy develops and produces energy storage technology and balancing 

power plants that can be run with low-emission fuels such as synthetic carbon-neutral 

methanol, methane, and hydrogen (Wärtsilä, n.d. -f). Currently, Wärtsilä has delivered 



15 

over 110 energy storage systems to 180 countries and the company’s power plant ca-

pacity is over 76 GW (Wärtsilä, n.d. -f). Wärtsilä Energy also provides lifecycle services 

such as delivering spare parts, field service, and power plant lifecycle upgrades (Wärt-

silä, n.d. -f). 

 

Wärtsilä Marine Power has a wide product and service portfolio including marine en-

gines, propulsion systems, hybrid technology, and integrated powertrain systems (Wärt-

silä, n.d. -g).  Wärtsilä Marine Power delivers products and services for a variety of ma-

rine applications including passenger, offshore, merchant, and special purpose vessels 

such as fishing vessels and tugs (Wärtsilä, n.d. -g).  Marine Power also provides lifecycle 

services, spare parts, technical support, and maritime cyber security services (Wärtsilä, 

n.d. -g).  

 

Wärtsilä Marine Systems consists of three business units: Exhaust Treatment, Gas Solu-

tions, and Shaft Line Solutions (Wärtsilä, n.d. -h). Exhaust Treatment delivers technolog-

ical solutions to reducing emissions and achieving compliance with environmental regu-

lations (Wärtsilä, n.d. -h). Gas Solutions provides cargo handling systems, gasification 

and liquefaction systems, fuel systems, and alternative engine configuration systems 

(Wärtsilä, n.d. -h). Shaft Line Solutions provides end-to-end marine shaft line products 

such as seals, bearings, and hydraulic equipment (Wärtsilä, n.d. -h). All three business 

units also provide lifecycle services. 

 

Wärtsilä Portfolio Business consists of three business units that aim to enhance perfor-

mance and create value by managing divestments and other strategic measures (Wärt-

silä, n.d. -e). The businesses that are divested often do not have strong connections to 

other Wärtsilä products or services or are no longer in line with Wärtsilä’s strategy. Cur-

rently, the business units in Wärtsilä Portfolio Business are Automation, Navigation & 

Control Systems (ANCS), Marine Electrical Systems, and Water & Waste (Wärtsilä, n.d. -

e). 

 



16 

ANCS offers dynamic positioning systems, sensors, and navigation & automation systems 

to increase vessel efficiency and safety, while being compliant with regulations (Wärtsilä, 

n.d. -e). Marine Electrical Systems specializes on electrical integration services on com-

plex vessels, military vessels, and yachts (Wärtsilä, n.d. -e). Water & waste business unit 

provides environmental products such as wastewater management systems, ballast wa-

ter management systems, as well as freshwater generation solutions and vacuum collec-

tion systems (Wärtsilä, n.d. -e). 

 

 

2.1.1 Wärtsilä Exhaust Treatment 

Wärtsilä Exhaust Treatment, is a business unit under Wärtsilä Marine Systems, that de-

signs exhaust gas abatement solutions and products for the shipping industry (Wärtsilä, 

n.d. -i). The unit also provides lifecycle services including spare parts and field services 

for its abatement products. Exhaust Treatment’s product portfolio consists of scrubber 

technology that reduces SOx and PM emissions and onboard CCS technology (Wärtsilä, 

n.d. -i). Wärtsilä Exhaust Treatment currently employs over 200 employees in nine coun-

tries in Europe and Asia (Wärtsilä, n.d. -i).  

 

The environmental regulations set by the IMO are one of the main business drivers for 

Wärtsilä Exhaust Treatment. The SOx and NOx emission regulations in MARPOL Annex 

VI and the IMO’s increasing focus on CO2 emissions create the market in which Wärtsilä 

Exhaust Treatment operates. Wärtsilä Exhaust Treatment is the market leader for EGC 

systems with over 800 installed exhaust gas treatment systems (Wärtsilä, n.d. -i).  

 

 

2.1.2 Wärtsilä Exhaust Treatment SOx abatement solutions 

Wärtsilä Exhaust Treatment’s scrubber portfolio consists of five different designs, as il-

lustrated in figure 2. The design family includes both inline and venturi scrubber designs. 



17 

The designs have different capabilities and features such as capacity and energy con-

sumption, which together with vessel type and layout, are important factors when ac-

quiring a scrubber system for a vessel (Wärtsilä, n.d. -i). For example, inline designs such 

as the Wärtsilä I-SOx system require less space but have less capacity and require a 

higher water flow compared to the venturi designs such as Wärtsilä V-SOx. Wärtsilä 

scrubbers can be operated in open loop, closed loop, or hybrid mode.  

 

 

Figure 2. Wärtsilä Exhaust Treatment scrubber design family (Wärtsilä, n.d. -j). 

 

In a Wärtsilä open loop scrubber system, seawater is sprayed to the exhaust gas in three 

different stages (Wärtsilä, n.d. -k). The sprayed seawater reacts with the sulphur oxide 

in the exhaust gas and forms sulphuric acid, which is neutralized by the natural alkalinity 

of the seawater (Wärtsilä, n.d. -k). The neutralized wash water is discharged to the sea 

after ensuring that it complies with the environmental regulations. Wash water is moni-

tored at the inlet and outlet points of the system to ensure compliance and to record 

system operations (Wärtsilä, n.d. -k). Wärtsilä open loop SOx scrubber system is illus-

trated in figure 3.  

 



18 

 

Figure 3. Wärtsilä open loop scrubber system (Wärtsilä, 2017, p. 4) 

 

In a Wärtsilä closed loop scrubber system, the sulphur oxide in the exhaust gas is neu-

tralized by spraying it with a mixture of scrubbing water and alkali such as sodium hy-

droxide (Wärtsilä, n.d. -k). Instead of discharging the wash water to the sea, the closed 

loop system circulates the washing mixture in the scrubber and only a small bleed-off is 

extracted from the system, which is replaced with fresh water and alkali (Wärtsilä, n.d. -

k). The accumulated impurities in the wash water are removed from the loop with the 

extracted bleed-off, which is then fed to the water treatment unit where it is filtered for 

PM, PAH, and other harmful particles (Wärtsilä, n.d. -k). The cleaned effluent is then 

discharged or led to a holding tank if discharging is prohibited (Wärtsilä, n.d. -k). 

 

The pH levels of the washing mixture are constantly monitored and controlled with alkali 

dosing to ensure maximum cleaning efficiency and proper functioning of the system. The 

closed loop system is useful in areas where the natural alkalinity of the water is low and 

discharging is limited or prohibited (Wärtsilä, n.d. -k). Wärtsilä closed loop system is il-

lustrated in figure 4. 



19 

 

 

Figure 4. Wärtsilä closed loop scrubber system (Wärtsilä, 2017, p. 5). 

 

The Wärtsilä hybrid scrubber system combines the open and closed loop systems, allow-

ing the vessel to operate in low alkaline waters as well as in the open sea (Wärtsilä, 2018, 

p. 6). The system can be switched run closed or open loop at any given time, which in-

creases the vessels operational flexibility and is therefore suitable for vessels with varia-

ble operational routes. Wärtsilä hybrid scrubber system is illustrated in figure 5. 



20 

 

Figure 5. Wärtsilä hybrid scrubber system (Wärtsilä, 2017, p. 6) 

 



21 

3 Theoretical background 

This chapter introduces the history of IMO regulatory framework, the life cycle assess-

ment method, life cycle of a Wärtsilä SOx scrubber system, and prior LCA studies in the 

field. The chapter therefore covers the key theories behind the drivers of the SOx abate-

ment product business, the units of analysis used in this study, and the used methodol-

ogy. 

 

3.1 IMO regulatory framework 

The convention for the establishment of IMO was formed in 1948 at the international 

maritime conference of the United Nations and entered into force in 1958 (IMO, n.d. -c). 

The organization was established initially to improve maritime safety and efficiency of 

navigation and to control marine pollution caused by ships (IMO, n.d. -c). Since its incep-

tion, IMO has created a broad regulatory framework around the safety and sustainability 

of the maritime industry that does not conflict with the needs of global economy (Joseph 

& Dalaklis, 2021, p. 1). 

 

One part of the regulatory framework is the International Convention for the Prevention 

of Pollution from Ships, referred to as MARPOL. MARPOL was adopted in 1973 and en-

tered into force in 1978 (IMO, n.d. -c). Today its main responsibilities are to counter ac-

cidental and operational oil pollution, as well as chemical, sewage, and air pollution 

caused by maritime traffic (IMO, n.d. -c). The convention has been updated many times 

since its inception and today it includes six (I-VI) technical Annexes (IMO, n.d. -d). These 

Annexes, especially Annex VI, are one of the main drivers for Wärtsilä’s EGC system busi-

ness. 

 

 



22 

3.1.1 Annex I 

MARPOL Annex I was adopted in 1983 and its main objective is to ensure that oil tankers 

are built and operated in a manner that minimizes oil pollution during normal operation 

or in the event of accident (IMO, n.d. -e).  Annex I introduced regulations for the fitting 

out and construction of new oil tankers, such as ballast tanks to separate the ballast wa-

ter from the cargo to prevent oil spills in the event of an accident (IMO, n.d. -e). In 1992, 

Annex I was revised, and an amendment was added stating that all new oil tankers must 

built with a double hull to prevent leakage if the vessel is damaged (IMO, n.d. -e). This 

amendment replaced the requirements for separate ballast tanks. The amendment also 

stated that existing oil tankers were also to be scheduled for the fitting of double hulls 

(IMO, n.d. -e).  

 

In addition to cargo oil and its potential for pollution, fuel oils and discharged water are 

also addressed in Annex I. The oil content of bilge water discharged from ships over 400 

gross tons was limited to 15 ppm in Annex I and since then the limitations have become 

more stringent in certain waters around the world (McLaughlin et al. 2014, p. 5638). To 

comply with the limitations, the oil is separated from the bilge water in an oily water 

separator, and the oil content is monitored to ensure compliant discharge (IMO, n.d. -e). 

 

Construction and operational regulations introduced in Annex I combined with traffic 

separation schemes and other safety regulations have greatly contributed to the de-

crease of sea pollution (IMO, n.d. -e). However, given the forecasted growth in marine 

traffic and the increasing focus on sustainability, stricter measures regarding discharging 

of bilge water and other harmful liquids can be expected. One possible solution for re-

ducing oil pollution is the development of advanced combustion technologies that utilize 

e.g., methane or hydrogen instead of traditional petroleum.  

 

 



23 

3.1.2 Annex II 

MARPOL Annex II entered into force in 1983 and addresses pollution from noxious liquid 

substances carried in bulk (Arslan et al. 2018, p. 358). Annex II includes a categorization 

system for noxious and liquid substances and their impacts on human health, environ-

ment, and amenities (IMO, n.d. -f). The categories are named X, Y, Z and other substances 

and they are presented in table 1. 

 
Table 1. Categorization system for pollution caused by noxious and liquid substances (IMO, n.d. 

-f). 

 
Category Definition 

X Noxious Liquid Substances which, if discharged into the sea from tank 
cleaning or de-ballasting operations, are deemed to present a major 
hazard to either marine resources or human health and, therefore, 
justify the prohibition of the discharge into the marine environment 

Y Noxious Liquid Substances which, if discharged into the sea from tank 
cleaning or de-ballasting operations, are deemed to present a hazard 
to either marine resources or human health and, or cause harm to 
amenities or legitimate uses of the sea and therefore justify a limita-
tion on the quality and quantity of the discharge into the marine envi-
ronment 

Z Noxious Liquid Substances which, if discharged into the sea from tank 
cleaning or de-ballasting operations, are deemed to present a minor 
hazard to either marine resources or human health and therefore jus-
tify less stringent restrictions on the quality and quantity of the dis-
charge into the marine environment 

Other substances Substances which have been evaluated and found to fall outside cate-
gory X, Y or Z because they are considered to present no harm to ma-
rine resources, human health, amenities, or other legitimate uses of 
the sea when discharged into the sea from tank cleaning or de-ballast-
ing operations. The discharge of bilge or ballast water or other resi-
dues or mixtures containing these substances are not subject to any 
requirements of MARPOL Annex II 

 

In addition to the categorization system, Annex II defines rules and requirements for dis-

charging, carriage, and stripping procedures for the noxious liquids (Arslan et al. 2018, p. 

347). By way of example, Annex II prohibits the discharge of noxious substance residue 

within 12 nautical miles of the nearest shore (Arslan et al. 2018, p. 358).  

 

 



24 

3.1.3 Annex III 

MARPOL Annex III was adopted in 1992 and addresses the pollution caused by harmful 

substances in packaged form (Arslan et al. 2018, p. 348). According to the Annex, each 

vessel carrying harmful substances in packaged form should store documentation for the 

stowage plan of the ship until the substances are discharged or stored ashore (Arslan et 

al. 2018, p. 348). In addition to substances in packaged forms, the Annex addresses the 

stowage plans for harmful substances carried in freight containers, tanks, and wagons 

(Arslan et al. 2018, p. 348). 

 

The Annex includes marking and labelling regulations which state that each package con-

taining harmful substances should be marked durably and with the correct technical 

name (Arslan et al. 2018, p. 348). Stowage documents combined with correct marking 

and labelling of harmful substances are effective in reducing the risks of accidents harm-

ful to human health or the environment. 

 

 

3.1.4 Annex IV 

MARPOL Annex IV addresses the pollution caused by sewage and it entered into force in 

2003 (Arslan et al. 2018, p. 349). In Annex IV, sewage is defined as wastewater from 

lavatories, medical facilities, spaces containing living animals, and other wastewater con-

taining waste from these premises (Şahin et al. 2020, p. 49). Among other chemicals, 

sewage contains high amounts of nitrogen and phosphorus, which are harmful to the 

marine environment (Arslan et al. 2018, p. 349). 

 

Annex IV regulates the discharging of untreated sewage and requires governments to 

provide sewage reception facilities in ports (IMO, n.d. -g). Vessels certified to carry over 

15 persons and are of 400 gross tonnage or above are required to have a sewage treat-

ment plant, sewage disinfecting system, or a sewage holding tank (IMO, n.d. -g). Dis-



25 

charging of sewage is prohibited unless the vessel is equipped and operating with a sew-

age treatment plant. Discharging of disinfected sewage is allowed if the vessel is located 

more than three nautical miles away from the nearest shore (IMO, n.d. -g). Untreated 

sewage can be discharged if it is approved by administration or if the vessel is more than 

12 nautical miles away from the shore and moving at a speed of at least four knots (IMO, 

n.d. -g). 

 

 

3.1.5 Annex V 

MARPOL Annex V entered into force in 1988 and contains regulations for the prevention 

of pollution by garbage from ships (Arslan et al. 2018, p. 350). The regulations in the 

Annex apply to all ships but do not contain any certification or approval requirements. 

Despite the lack of these requirements, over 150 countries have ratified the Annex (IMO, 

n.d. -h). The Annex prohibits discharging any type of garbage into the sea unless they 

comply with the regulations included in the Annex related to food waste, cargo residues, 

cleaning agents, or animal carcasses (IMO, n.d. -h). 

 

Annex V also requires a garbage management plan to be stored on all ships and floating 

or fixed platforms that are of 100 gross tonnage or more or certified to carry 15 or more 

persons (Arslan et al. 2018, p. 350).  All ships and fixed or floating platforms that are 

certified to carry 15 or more persons and are of 400 gross tonnage or above are required 

to keep a garbage record book on board (Arslan et al. 2018, p. 350). The intent of the 

garbage record book is to keep track of the amount of incinerated and discharged waste 

produced in the ship, and the location and date of the waste management procedures 

(IMO, n.d. -h). The garbage record book can be a useful tool for ship operators to avoid 

penalties when upon inspection. Keeping an up-to-date record book of waste manage-

ment is an approved proof of complying with the waste regulations and ensuring that 

waste is handled properly in allowed locations. 



26 

3.1.6 Annex VI 

MARPOL Annex VI, also called Regulations for the Prevention of Air Pollution was intro-

duced by the IMO in 1997 and entered into force in 2005 (Čampara et al. 2018, p. 3). 

Annex VI regulations limit SOx, NOx, PM, VOC, and other ozone depleting emissions from 

shipping operations and define specific ECA’s in which some of the emission regulations 

are more stringent (IMO, n.d. -d). The currently established ECA’s are the Baltic Sea area, 

North Sea area, the North American area, and the United States Caribbean Sea area, as 

presented in figure 6 (Fagerholt et al. 2015, p. 58). In addition to these areas, the Medi-

terranean Sea area has been adopted as the next SOx and PM emission-controlled area 

under Annex VI (IMO, n.d. -i).  The amendment is expected to enter into force in 2024. 

 

 

Figure 6. Emission Control Areas (Rymaniak et al. 2018, p. 2). 

 

Annex VI regulations limit the SOx content in marine fuel oils to improve air quality and 

to prevent environmental damage. The marine fuel oil SOx content limitations have pro-

gressively tightened over time, as illustrated in figure 7. SOx and PM emissions are harm-

ful to human health and have been linked to asthma, heart attacks and premature death 

(Tokuslu et al. 2020, p. 150). Compliance with the latest SOx regulations can be achieved 

by using fuel oil that meets the SOx content limits, natural gas, or biofuels (Boviatsis, 



27 

2022, p. 393). Exhaust gas cleaning systems, also called scrubbers, are also a viable al-

ternative for achieving compliance. Scrubbers remove sulphur oxides and particle matter 

from engine exhaust gases and can achieve the strictest 0,1% m/m SOx limitation (Bo-

viatsis, 2022, p. 393). 

 

 

Figure 7. Annex VI fuel oil SOx content limitations over time (Čampara et al. 2018). 

 

SOx and NOx emissions cause acidification and eutrophication in oceans resulting in 

changes in water pH levels and increase in anoxic and hypoxic water areas (Omstedt et 

al. 2015, p. 242). Annex VI introduced NOx control levels for all marine diesel engines 

with a power output of more than 130 kW and that are installed on ships built on or 

after 1 January 2000 (Čampara et al. 2018, p. 4). Today, these control levels are defined 

as Tiers I, II, and III. The three Tiers are based on the construction date of the vessel and 

their NOx limitations are defined as g/kWh, which is proportional to the engine’s rated 

speed (Čampara et al. 2018, p. 4). Tier III is the most stringent and applies to ships built 

after 2016 and only when operating in ECA’s. Operating elsewhere requires compliance 

with Tier I or Tier II depending on the age of the vessel (Čampara et al. 2018, p. 4). The 

Tier specific NOx limitations are illustrated in figure 8.  



28 

 

 

Figure 8. MARPOL Annex VI NOx emission limits (Deng et al. 2021, p. 4) 

 

NOx emission reduction methods are often categorized as primary or secondary meth-

ods (Rymaniak et al. 2018, p. 2). Primary methods aim to reduce the formation of NOx 

inside the engine during the combustion process and they are often sufficient for Tier II 

limitations. Primary methods are, for example, modifying the fuel injection into the com-

bustion chamber or lowering the temperature of the combustion air (Rymaniak et al. 

2018, p. 3). Secondary methods aim to reduce NOx from the exhaust gas and the most 

common method for this is the use of SCR technology (Rymaniak et al. 2018, p. 2). SCR 

produces chemical reactions using ammonia and a catalyst, the most dominant of which 

converts nitrogen monoxide, oxygen and ammonia into nitrogen and water (Aakko-Saksa 

& Lehtiranta, 2019, p. 21). SCR technology is often used in vessels operating in areas that 

require Tier III compliance due to its high NOx reduction efficiency (Rymaniak et al. 2018, 

p. 5). 

 

In 2011, Annex VI was complimented with new regulations concerning energy efficiency 

requirements. These regulations state that all vessels must have an energy efficiency 



29 

management plan which includes plans to improve voyage planning, increase frequency 

of cleaning underwater parts, and implement new technical measures for increasing en-

ergy efficiency (Boviatsis et al. 2022, p. 394). The regulations also state that the Energy 

Efficiency Design Index (EEDI), which is a measure of ship’s energy efficiency, must be 

calculated for all new ships. The calculation is to be done using a formula developed by 

the IMO and the results represent the minimum required energy efficiency of the vessel 

(Čampara et al. 2018, p. 8). 

 

3.2 Life cycle assessment 

Life cycle assessment (LCA) is an ISO-standardized quantitative method for identifying 

the environmental impacts of a product or a process throughout its lifecycle (Hellweg & 

Canals, 2014, p. 1109). LCA can be used in many ways, for example to optimize the envi-

ronmental performance of a product or a process, to benchmark and compare environ-

mental impacts of products or processes, to design production and consumption policies, 

or to market a product or a process (Hellweg & Canals, 2014, p. 1109). Wärtsilä has com-

missioned this LCA study to initiate the process of developing environmental KPIs for 

their scrubber business and to contribute to the company’s target of being carbon neu-

tral by 2030. 

 

ISO has developed two standards for life cycle assessments and how they should be con-

ducted. These standards are ISO 14040, which defines LCA principles and framework, 

and ISO 14044, which defines requirements and guidelines for conducting a life cycle 

assessment. As shown in figure 9, the LCA framework is an iterative process that consists 

of four phases: defining goal and scope, inventory analysis, impact assessment, and in-

terpretation of results (ISO, 2006). 

 



30 

 

Figure 9. Stages and example applications of LCA (ISO, 2006). 

 

In the first phase of an LCA, the goal and scope of the study are defined. The goal defini-

tion of the study must include four statements for the LCA to be compliant with the ISO 

standards. These statements are the intended application of the study, reasons for con-

ducting the study, to whom the results are to be presented, and whether the results will 

be used in comparative public assertions (Matthews et al. 2015, p. 85). The scope of the 

study should include a specific explanation of what is included in the study and how the 

assessment is going to be conducted. ISO 14044 standard defines clear instructions for 

12 items that are required to be described in the scope. These items include for example 

the studied system, the functional unit of the system, system boundaries, and the impact 

assessment methodology used in the study (Matthews et al. 2015, p. 86). 

 

The second phase of an LCA is the inventory analysis. In this phase, the input and output 

data for the studied system is collected in accordance with the predefined goal and scope 

of the study (Matthews et al. 2015, p. 101). The input data generally is the materials, 



31 

electricity consumption, logistics, and other resources that are needed to produce the 

studied system. The output data refers to the product system itself, co-products, and 

release outputs such as GHG emissions that are produced in creating the product system 

(Matthews et al. 2015, p. 101). The ISO 14044 guidelines state that the data collected for 

the inventory analysis needs to be validated and related to the functional unit that is 

defined in the goal and scope (Matthews et al. 2015, p. 101).  

 

The third phase of an LCA is the impact assessment, in which the environmental impacts 

of the life cycle inventory are assessed in accordance with the chosen impact assessment 

methodology. The goal of the impact assessment is to transform the results of the inven-

tory analysis into a form that serves the goal and purpose of the study (Matthews et al. 

2015, p. 366). There are several impact assessment methodologies that track different 

impact categories and therefore different impacts on ecosystems, natural resources, and 

human health (Matthews et al. 2015, p. 366).  

 

The fourth and final phase of an LCA is the interpretation of the results. In this phase, 

the results all previous phases are studied in order to make conclusions and to recom-

mend actions based on the purpose of the study (Matthews et al. 2015, p. 113). The 

interpretation phase is often complemented with a sensitivity analysis, although it is not 

mandatory for achieving compliance with the ISO standards (Matthews et al. 2015, p. 

113). The sensitivity analysis is often performed by modifying the output and input pa-

rameters and the used methodology to see how much the results are affected (Mat-

thews et al. 2015, p. 114). The purpose of the sensitivity analysis is to test if the conclu-

sions are affected by changing the quantitative parameters (Matthews et al. 2015, p. 

114). 

 

 

3.2.1 Life cycle of a Wärtsilä V-SOx scrubber 

A Wärtsilä SOx scrubber system consists of hundreds of different components, which 

makes it difficult to estimate the service life of the system as an entity. The scrubber 



32 

towers are given a service lifetime expectancy of 20-25 years, during which some other 

components may have had to be replaced several times. In this research, the operational 

lifetime of the system is estimated to be 20 years, and replaceable components are con-

sidered and included in the life cycle assessment. 

 

Wärtsilä does not manufacture its SOx scrubbing systems in-house. Wärtsilä designs and 

delivers the systems, hence the manufacturing is outsourced to different suppliers. The 

company uses different suppliers to acquire most of the necessary components which 

are then ordered to the shipyard in which the system is assembled and installed to the 

vessel. After the system is installed and the vessel is ready to sail, a sea trial is performed 

to ensure that the scrubber operates in compliance with the IMO regulations. After pass-

ing the sea trial, the scrubber system is ready to be used as part of the ship’s operation. 

 

This study assesses a V-SOx hybrid scrubber system that is installed on a certain type of 

tanker. The operational lifetime of these type of tankers is generally 20 to 25 years (Ozguc, 

2018, p. 33). Therefore, if the scrubber system is inspected and maintained regularly, it 

should be able to operate throughout the lifetime of the tanker. Once the operational 

lifetime of the vessel and scrubber has come to an end, the scrubber is scrapped and 

disposed of or recycled, thus ending the lifecycle of the system. 

 

 

3.2.2 Prior works 

Although the latest sulphur content regulations were introduced in 2020 and the wide-

spread use of marine SOx scrubber systems is relatively new, several LCA studies have 

been conducted in the field. Many of the studies are comparative and contain cost as-

sessments for comprehensive comparison between the different options of complying 

with the sulphur content regulations.  

 



33 

Andersson et al. (2020) compared 20 MW open and closed loop marine SOx scrubber 

systems in terms of environmental impacts and installation cost payback time. They con-

ducted the LCA following the framework in the ISO 14040 standard and built the life cycle 

inventory using material from scientific articles and other publicly available data. The 

results were used to evaluate global warming, acidification, and eutrophication poten-

tials. Andersson et al. (2017, p. 175) concluded that the impacts generated by the open 

loop system are slightly smaller due to less material needed for installation and opera-

tion. However, open loop discharge water and closed loop NaOH consumption were not 

considered in the study. Andersson et al. (2017, p. 174) suggested further research to 

address these limitations, as they may have significant potential for impacting the envi-

ronment. They also concluded that compared to closed loop system, the open loop sys-

tem had a marginally shorter payback time regardless of the type of fuel used. 

 

Cui et al. (2021) conducted a comparative LCA and cost assessment study on an open 

loop system, closed loop system utilizing NaOH, and a system utilizing Mg(OH)2 as the 

alkali. The LCA consisted of the construction and operational phase and the impacts were 

assessed with the ReCiPe2016 method, which combines midpoint and endpoint impact 

categories. Cui et al. (2021, p. 113) found that the NaOH system produced the most en-

vironmental impacts out of the three systems. The open loop system was found to pro-

duce significantly less impacts compared to the other two systems. However, open loop 

wash water discharging was not modelled in the LCA, which likely contributed to the gap 

between the impacts of the systems. The NaOH and Mg(OH)2 systems were also more 

expensive according to the results obtained in the cost assessment due to the cost of the 

alkali over the life cycle (Cui et al. 2021, p. 113).  

 

Martínez-López et al. (2022) introduced an environmental assessment model and com-

pared the environmental performance of different marine sulphur mitigation methods. 

The studied methods were open and closed loop scrubber systems using varying sulphur 

content HFOs, running the main engine on MGO and running the engine in dual mode 



34 

using LNG. They applied the model to a container vessel operating in a shipping line be-

tween the Canary Islands and the Iberian Peninsula. 

 

Martinez-Lopez et al. (2022) evaluated the environmental performance of the different 

sulphur mitigation methods with climate change, marine ecotoxicity, and marine eu-

trophication impact categories. They included the scrubber wash water discharge in the 

study and modelled it to contain average concentrations of 16 different PAHs, nitrate and 

ten different metals. The introduced model quantified the environmental performance 

of the different methods in monetary terms, determining a cost for each environmental 

characterization factor (Martinez-Lopez et al. 2022). 

 

Martinez-Lopez et al. (2022) concluded that regardless of the operating mode, the scrub-

ber system was the most efficient sulphur mitigation method in terms of environmental 

performance. In terms of air emissions, they found that the dual engine LNG operation 

was the most suitable option. However, the total pollution impact was the lowest for the 

scrubber systems. MGO operation was found to be the least suitable option in compari-

son to the other methods. 

 

Martinez-Lopez et al. (2022) also concluded that there was no significant difference be-

tween the total pollution impact between open and closed loop scrubber systems. They 

highlighted that although the volume of discharge water in closed loop operation is sig-

nificantly lower, the marine eutrophication results were nearly the same. According to 

Martinez-Lopez et al. (2022), this phenomenon is the result of the significantly higher 

nitrogen concentration in closed loop discharge water. They suggested further research 

on the marine eutrophication caused by closed loop scrubber system operation. 

 



35 

4 Methodology 

This chapter demonstrates the data collection and research methodology used in the 

study. The goal and scope of the life cycle assessment are covered in chapters 4.1, fol-

lowed by inventory analysis and an explanation of uncertainties in inventory data in 

chapter 4.2. 

 

4.1 Goal and scope 

The goal of the life cycle assessment was to determine the environmental impacts of a 

certain Wärtsilä V-SOx hybrid scrubber system throughout its complete lifecycle. The 

reason for conducting the LCA study was to initiate the process of developing KPIs for 

future monitoring of environmental performance in the manufacturing, logistics and in-

stallation phases of the lifecycle. Also, assessing the environmental impacts of the oper-

ational and end-of-life phases of the system provides the company with information that 

can be used in benchmarking and product development activities. The results of the LCA 

were to be presented internally in Wärtsilä and as part of a master’s thesis seminar at 

the University of Vaasa. 

 

The system studied in the life cycle assessment is an Wärtsilä V-SOx hybrid scrubber sys-

tem. The studied system was installed on a tanker in 2019 and at the time of conducting 

the study, it had been in operation for four years and two months. The function of the 

system is to remove sulphur oxides and other contaminants from the exhaust gas pro-

duced by the combustion engines on the tanker. 

 

In LCA studies, the function of the system should be expressed as a functional unit which 

acts as a reference point for all inputs and outputs in the scope (Panesar et al. 2017, p. 

1969). Using the functional unit as a reference point allows the results of the LCA to be 

compared to other LCA studies of different processes or products with the same function 

(Panesar et al. 2017, p. 1969). The exhaust gas produced by the combustion processes 

in the vessel is directed into the scrubber where it is treated. The functional unit used in 



36 

this LCA was determined as 1 kg mass of exhaust gas entering from the engine to the 

scrubber system. The exhaust gas mass flows were obtained from Wärtsilä’s technical 

documentation.  

 

The system boundary defines the boundaries within which the life cycle assessment is 

performed (ISO, 2006).  In this study, the system boundary includes four life cycle stages, 

27 specifically chosen components, raw materials and transportation, and other inputs 

of the V-SOx system life cycle. The system components were selected based on their 

mass and function in the system, with the aim of selecting the most critical components 

in terms of system functionality. The system boundary is outlined in figure 10. 

 

 

 

Figure 10. LCA System boundary 

 

 



37 

The LCIA method used in the study was ILCD 2011 Midpoint+. Midpoint LCIA methods 

assess category indicators for selected impact categories that are in the middle of the 

pathway between life cycle inventory results and endpoints (Sharaai et al. 2012, p. 1392). 

Midpoint methods convert the category impacts into real environmental phenomenon 

such as eutrophication, acidification, and climate change (Sharaai et al. 2012, p. 1392). 

Endpoint LCIA methods assess category indicators that are in the end of the pathway of 

the environmental impact (Sharaai et al. 2012, p. 1392). Endpoint methods assess the 

impact of the environmental system to human health, ecosystem diversity, or resource 

availability, thus measuring damage on the societal value these entities produce (Sharaai 

et al. 2012, p. 1392). The general framework for LCIA pathways is illustrated in figure 11.  

 

 

Figure 11. LCIA steps from inventory to category endpoints (JRC, 2010a, p. 108) 

 

The ILCD handbook recommends ten midpoint impact categories and three areas of pro-

tection to be checked for relevance by default in LCIA’s (JRC, 2010a, p. 109). These impact 

categories and areas of protection are all included in the ILCD 2011 midpoint+ LCIA meth-

odology. The ILCD handbook also recommends methods and characterisation factors for 

the impact categories, as illustrated in table 2. The characterisation factors are classified 

as level I, II, or III. Level I is defined in the ILCD handbook as recommended and satisfac-

tory, level II as recommended but in need of some improvements, and level III as recom-



38 

mended but to be applied with caution (JRC, 2010b, p. 3). In addition to these classifica-

tions, a separate classification category for methods that are considered best of the an-

alysed methods but still considered deficient, is called “interim” (JRC, 2010b, p.3).  

 

The ILCD 2011 midpoint+ LCIA methodology and the ILCD handbooks were developed 

by the European Joint Research Centre in effort to enhance consistency and quality when 

applying LCA within the ISO 14040 and 14044 standards. ILCD 2011 midpoint+ uses the 

methods and characterisation factors recommended in the ILCD handbooks, which is the 

reason for choosing it as this study’s LCIA methodology. The same methodology has pre-

viously also been used by Järvinen (2021) in an LCA performed on a Wärtsilä marine 

diesel engine. The LCIA in this study was calculated using OpenLCA version 1.11.0 soft-

ware. 

 

Table 2. Recommended methods and their classification at midpoint (JRC, 2010b). 

 
Impact category Recommended default 

LCIA method 
Characterisation factor Classification 

Climate change Baseline model of 100 
years of the IPCC 

Radiative forcing as 
Global Warming Potential 
(GWP100) 

I 

Ozone depletion Steady-state ODPs 1999 as 
in WMO assessment 

Ozone Depletion Poten-
tial (ODP) 

I 

Human toxicity, 
cancer effects 

USEtox model (Rosenbaum 
et al. 2008) 

Comparative Toxic Unit 
for humans (CTUh) 

II/III 

Human toxicity, 
non-cancer effects  

USEtox model (Rosenbaum 
et al. 2008) 

Comparative Toxic Unit 
for humans (CTUh) 

II/III 

Particulate mat-
ter/Respiratory In-
organics 

RiskPoll model (Rabl and 
Spadaro, 2004) and Greco 
et al. 2007 

Intake fraction for fine 
particles (kg PM2.5-
eq/kg) 

I 

Ionising radiation, 
ecosystems 

Human health effect model 
as developed by Dreicer et 
al. 1995 (Frischknecht et al, 
2000) 

Human exposure effi-
ciency relative to U235 

II 

Ionising radiation, 
ecosystems 

No methods recommended  Interim 

Photochemical 
ozone formation 

LOTOS-EUROS (Van Zelm et 
al. 2008) as applied in ReC-
iPe 

Tropospheric ozone con-
centration increase 

II 

Acidification Accumulated Exceedance 
(Seppälä et al. 2006, Posch 
et al. 2008) 

Accumulated Exceedance 
(AE) 

II 



39 

Impact category Recommended default 
LCIA method 

Characterisation factor Classification 

Eutrophication, ter-
restrial 

Accumulated Exceedance 
(Seppälä et al. 2006, Posch 
et al. 2008) 

Accumulated Exceedance 
(AE) 

II 

Eutrophication, 
aquatic 

EUTREND model (Struijs et 
al. 2009b as implemented 
in ReCiPe 

Fraction of nutrients 
reaching freshwater end 
compartment (P) or ma-
rine end compartment (N) 

II 

Ecotoxicity (fresh-
water) 

USEtox model, (Rosen-
baum et al. 2008) 

Comparative Toxic Unit 
for ecosystems (CTUe) 

II/III 

Ecotoxicity (terres-
trial and marine) 

No methods recommended   

Land use Model based on Soil Or-
ganic Matter (SOM) (Milá I 
Canals et al. 2007b) 

Soil Organic Matter III 

Resource depletion, 
water 

Model for water consump-
tion as in Swiss Ecoscarcity 
(Frischknecht et al. 2008) 

Water use related to local 
scarcity of water 

III 

Resource depletion, 
mineral, fossil, and 
renewable 

CML 2002 (Guinée et al. 
2002) 

Scarcity II 

 

The LCA conducted on this study includes assumptions on each phase of the systems life 

cycle. The assumptions and uncertainties in each phase are outlined in chapter 4.2.5. 

The assumptions in the study create limitations to the interpretation of the environmen-

tal impacts of the systems lifecycle, which are discussed in chapter 6. The results of this 

LCA study were not to be used in a comparative assertion, and therefore a critical review 

for the study was not performed.  

 

4.2 Inventory analysis 

The life cycle inventory analysis includes the input and output data for each life cycle 

phase of the studied product system. The input data was collected from Wärtsilä’s inter-

nal databases, documentation sent by the ship’s operator and secondary sources i.e., 

scientific literature and Ecoinvent database if internal data was not found to be sufficient. 

The life cycle phases of the system were defined as raw material extraction and manu-

facturing of the components, transportation to shipyard, operational phase, and end-of-

life phase.  



40 

As stated in chapter 3.2.1, the studied V-SOx hybrid scrubber system consists of hun-

dreds of different components. The components for the LCA were selected from the bill 

of materials of the delivery project of the system based on their mass and functionality 

in the system. Out of the 27 selected system components, six were not supplied by Wärt-

silä, but instead by the shipyard. Although not being in Wärtsilä’s scope of supply, the 

components are crucial for the function of the system and contribute significantly to 

meeting the mass-specific requirements of the LCA. The total weight of the system was 

estimated to be 35 tons. The combined weight of the selected components without 

packaging materials was 30,3 tons, giving the weight-based cut-off range for the LCA of 

86,7%. The data collection methods for each phase of the life cycle are illustrated in table 

3. 

 

Table 3. Data collection methods and data quality in each life cycle phase. 

 
Life cycle phase Data quality Data Source 

Raw material extraction & 
manufacturing of compo-
nents 

Primary & secondary 
data 

Wärtsilä internal databases, Ecoin-
vent database v3.8, Literature 

Transportation to shipyard Primary data & sec-
ondary data 

Wärtsilä internal databases, Ecoin-
vent database v3.8 

Operational phase Primary & secondary 
data 

Wärtsilä internal databases, cus-
tomer documentation, Ecoinvent da-
tabase v3.8 

End-of-Life Secondary data Ecoinvent database v3.8 

 

 

4.2.1 Raw material extraction and manufacturing of components 

The first life cycle phase of the studied system consists of the extraction and manufac-

turing of the materials used in the selected components, and their delivery to the com-

ponent manufacturers and suppliers. Packaging materials, for which data were acquired 

from Wärtsilä’s shipping documents were also included in the material inputs of this 

phase. The material compositions of the selected components were collected from 

Wärtsilä’s internal tools and databases and scientific literature. All 6 components deliv-

ered by the shipyard were tanks and were assumed to be made of carbon steel based on 



41 

Wärtsilä’s documentation. Wärtsilä has delivered similar tanks in the past and has docu-

mentation of their typical material composition and mass. 

 

The data for extraction and production of the raw materials was collected from Ecoinvent 

database version 3.8 market processes. The transportation data from extraction to sup-

plier was based on average distances and transportation methods and was also collected 

from the Ecoinvent database. The material composition of the selected components con-

sisted mostly of different grades of stainless and carbon steel, copper, cast iron, and al-

uminium. Some of the components also included metal coating, synthetic rubber, brass, 

polyvinylchloride, glass reinforced plastic, carbon reinforced plastic, or electronic sys-

tems such as displays, for which input data were collected from the Ecoinvent database. 

For coated components, an assumption was made that the coating material accounted 

for 3% of the components total mass. In OpenLCA, the coating materials were modelled 

with a market process for epoxy resin liquid obtained from Ecoinvent database v3.8. 

 

Carbon steel was the most dominant material in the system, attributing for 75% of the 

total mass of the system. Stainless steel accounted for 10% of the systems mass and cast 

iron for 9%. The remaining 6% of the mass was accounted by all other materials men-

tioned on page 35. The components were delivered in wooden boxes, and rigid foam 

made of polyurethane was assumed to be the protective material for the delivery. The 

mass of the protection material was assumed to be 0,5% - 5% of the total package mass, 

depending on the size and fragility of the component. The volume of wood used in the 

packaging materials was calculated using the dimensions of the packages, which were 

obtained from the shipping documents. 

 

Wärtsilä did not manufacture the components on the scope of this LCA. The manufac-

turing data was collected from Ecoinvent database version 3.8 due to the vast number 

of different manufacturers and difficulties in acquiring data from them.  Majority of the 

components in the scope were given an estimated lifetime of 15-20 years. Four replace-

able components during the lifetime of the system were identified and their processes 



42 

were duplicated in the OpenLCA model. The Ecoinvent database contains processes con-

taining average inputs and outputs for steel, copper, aluminium, and other metal prod-

uct manufacturing, which were utilized in simulating the manufacturing of the compo-

nents in the scope.  

 

 

4.2.2 Transportation from supplier to shipyard 

The second life cycle phase of the system consists of transportation from the supplier to 

the shipyard, where the system is installed on the vessel. The transportation data includ-

ing transportation methods and delivery address information were collected from ship-

ping documents and Wärtsilä’s internal databases. The six components in the scope de-

livered by the shipyard were assumed to be transported 500 km with 7.5-16 metric ton 

lorries that operate in compliance with the EURO VI exhaust gas emission standard. 

 

The EURO emission standards were created by the European Commission to regulate the 

GHG emissions produced by light-duty and heavy-duty vehicles. The EURO VI standard is 

the latest and most stringent emission standard for heavy-duty vehicles set by the com-

mission, and it regulates, for example CO2, NOx, HC, and PM contents in exhaust gas 

emissions (Grigoratos et al. 2019, p. 348). 

 

The system was installed on the vessel in a shipyard located in South Korea. The compo-

nents in the scope were delivered to the shipyard from various locations in East Asia and 

Europe. The freight was transported with lorries, aircrafts, and cargo ships. In the 

OpenLCA software, the transportation was modelled using a tonne-kilometre (tkm) as 

the unit of measure. The unit represents the transport of one tonne of goods including 

packaging materials for a distance of one kilometre with the given transport method 

(Eurostat, 2023). The tkm value for each delivery was calculated using equation 1: 

 

   𝑡𝑘𝑚 =
𝑀𝑎𝑠𝑠 (𝑘𝑔) 𝑜𝑓 𝑡𝑟𝑎𝑛𝑠𝑝𝑜𝑟𝑡𝑒𝑑 𝑔𝑜𝑜𝑑𝑠

1000
× 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 (𝑘𝑚) 𝑜𝑓 𝑡𝑟𝑎𝑛𝑠𝑝𝑜𝑟𝑡,   (1) 

 



43 

The transportation distances were calculated using road, seaport and airport distance 

calculators that were found on the internet. For road transport, 3.5-7.5 metric ton and 

7.5-16 metric ton lorry processes obtained from Ecoinvent v3.8 were used to model the 

transport. The lorries were assumed to operate in compliance with the EURO VI in South 

Korea and Europe and EURO V in some parts of East Asia. For sea transport, bulk carrier 

and container ship processes were obtained from the Ecoinvent database and used in 

the model. Air transport was modelled with a process for generic air freight obtained 

from the Ecoinvent database. In total, the components were transported by three air 

deliveries, four ship deliveries, and 18 road deliveries.  

 

 

4.2.3 Operational phase 

The operational data of the system was collected from Wärtsilä’s technical documenta-

tion of the system, Wärtsilä’s databases and documentation and other information pro-

vided by the operator of the vessel. The operator was unable to attend meetings regard-

ing the operation of the system, which led to an increased number of assumptions in the 

modelling of the operational phase.  

 

The V-SOx scrubber system was installed in 2019 on a tanker and had been in operation 

for 50 months at the time of conducting the LCA. The tanker has one main engine that is 

connected to an 8 MW scrubber, three auxiliary engines that are connected to a 4 MW 

scrubber and an oil-fired boiler that is connected to a 1 MW venturi tube. The systems 

running hours were provided by the operator and used to calculate an estimate for total 

running hours for the duration of the operational phase. The main engine scrubber was 

estimated to be in operation for 142 560 hours, auxiliary engine scrubber for 87 840 

hours and the oil-fired boiler scrubber for 4392 hours during the 20-year operational 

phase. 

 

The installed scrubber system is a hybrid and can thus be operated in both open and 

closed loop modes. The ratio of open to closed loop usage was provided by the operator 



44 

and was used in modelling the operational phase. The vessel had mostly operated in sea 

areas and ports where discharging of the wash water is allowed. Therefore, the scrubber 

system had been operated in open loop mode for 99% and in closed loop for 1% of the 

running hours since installation. The closed loop operation was assumed to be in port 

running two auxiliary engines and the oil-fired boiler. The baseline scenario shown in 

table 4 was modelled using the scrubber mode usage ratio provided by the operator.  

 

An additional analysis for two more operational phase scenarios was calculated to pro-

vide more results on the environmental impacts of closed loop operation in comparison 

to open loop operations. In the first additional scenario, the system was assumed to be 

operated in manoeuvring closed loop mode for 10% of the time and in the second sce-

nario for 30% of the time. In both additional scenarios, the system was assumed to be 

run on port closed loop operating mode for 5% of the time. For rest of the running hours, 

the system was assumed to be run on open loop seagoing mode. The operational profiles 

and scrubber running configuration for each scenario are presented in table 4, in which 

the running time of different configurations are described as percentages of the systems 

total running hours. 

 

Table 4. Scrubber operating modes as percentages of total system running hours. 

 
Scenario Seagoing Manoeuvring Port 

Baseline scenario OL, 70% OL, 25% OL 4% / CL 1% 

Additional scenario 1 OL, 70% OL, 15% / CL 10% CL 5% 

Additional scenario 2 OL, 65% CL, 30% CL 5% 

  

The estimated fuel consumption of the vessel in 2022 was obtained from Wärtsilä’s in-

ternal database. Running the scrubber system typically increases the ships fuel consump-

tion approximately between 1% to 3% depending on the characteristics of the system, 

used fuel type, and operating mode (Zis et al. 2022, p. 1101). The estimated fuel con-

sumption for 20 years of operating the scrubber was calculated based on the tankers 

fuel consumption estimate from 2022 and Wärtsilä’s technical documentation on the 

systems energy consumption. An estimation was made that different operating modes 



45 

increase fuel consumption between 0,8% to 2,9%. Open loop operation typically in-

creases the fuel consumption more compared to closed loop operation because more 

water is needed in the scrubbing process, which increases the use of scrubbing water 

pumps and therefore energy consumption. 

 

Based on the estimates on fuel consumption increase, assumptions were made that the 

vessels fuel consumption due to scrubber use in the baseline scenario was increased by 

2,7%, in the first additional scenario by 2,4% and in the second additional scenario by 

2%. The energy consumption of the system was modelled to be embedded in the fuel 

consumption increase of the vessel. The tanker was assumed to operate on heavy fuel 

oil with a sulphur content of 3,5% m/m throughout the operational phase. On all scenar-

ios, the scrubber was assumed to operate to clean the exhaust gas to a level equivalent 

to using a fuel with a 0,1% sulphur content. 

 

The data on scrubbing water consumption in open and closed loop operations was ob-

tained from Wärtsilä’s technical documentation and is described in table 5. The water 

supply values in the documentation were based on operating modes that are permitted 

for complying with MARPOL Annex VI regulations. The operating modes are described in 

table 6. 

 

Table 5. Water consumption on different operating modes. 

 
Utility Seagoing Manoeuvring Port 

EGC operating mode Open loop Closed loop Closed loop 

Total scrubbing water supply (m3/h) 540 405 160 

Cooling water supply for closed loop operation 
(m3/h) 

- 265 225 

Sea water intake (m3/h) 540 300 260 

 

Table 6. Operating modes. 

 
Ship operating mode Seagoing Manoeuvring Port 

EGC operating mode Open loop Closed loop Closed loop 

ME1 load (% MCR) 86 75 0 

AE1 load (% MCR) 91 80 80 



46 

Ship operating mode Seagoing Manoeuvring Port 

EGC operating mode Open loop Closed loop Closed loop 

AE2 load (% MCR) 91 80 80 

AE3 load (% MCR) 91 80 0 

OFB1 load (% MCR) 0 0 100 

 

Closed loop operation of the system requires the use of sodium hydroxide to control the 

pH levels of the washing mixture. The consumption of sodium hydroxide in the closed 

loop operation is directly proportional to the operating power of the vessel and sulphur 

content of the fuel. The recommended solution was sodium hydroxide 50% solution, in 

which the chemical is mixed with equal amount of water. The consumption of the chem-

ical was obtained from Wärtsilä’s technical documentation.  

 

The closed loop operation of the system, specifically the use of the bleed-off treatment 

unit also requires the use of coagulation and flocculation chemicals. Flocculation chem-

icals are used to clump small particles in the effluent together so that they are easier to 

remove. Coagulation chemicals are used to remove the particles and impurities such as 

heavy metals, oil, suspended solids and turbidity from the effluent (Abujazar et al. 2022). 

The estimated consumption of coagulation and flocculation chemicals during the sys-

tems operational phase on the different scenarios was based on consumption averages 

obtained from Wärtsilä’s technical documentation. In the OpenLCA model, the use of 

flocculant was modelled as aluminium sulfate input and use of coagulant as polyalumin-

ium chloride input. Both flows were obtained from the Ecoinvent database version 3.8. 

 

The combustion process in the ships engines creates non-water-soluble content that is 

typically referred to as sludge. In closed loop operation, the sludge in the effluent is sep-

arated in the bleed-off treatment unit and collected in a sludge tank. The collected 

sludge cannot be incinerated on-board but must be brought to port where it is removed 

from the tank and transported to a treating facility for disposal. The estimated sludge 

generation for the closed loop operation was 35 litres/ton fuel and the sludge was as-

sumed to be treated in a dewatering unit. The dewatering unit removes the water of the 

mix and therefore reduces the final amount of generated sludge. The final amount of 



47 

sludge was assumed to be 0,6 times the mass of the generated sludge in the closed loop 

operation. In OpenLCA, the sludge generation was modelled with a market process for 

fly ash and scrubber sludge, which includes the transportation of the sludge to the treat-

ment facility and the treatment process. The process was obtained from the Ecoinvent 

database. 

 

In open loop operation, the amount of discharging water is the same as sea water intake 

for the scrubbing process. In closed loop operation, only a small bleed-off is discharged, 

after it has been cleaned in the bleed-off treatment unit. The capacity of the bleed-off 

treatment unit in the system was 5 m3 per hour, which was assumed to be fully utilized 

during the manoeuvring closed loop operation hours. In port closed loop operation, the 

used capacity was assumed to be 4 m3 per hour. The amount of discharged effluent on 

closed loop operations were calculated by multiplying the running hours with the given 

used capacity of the bleed-off treatment unit. 

 

The open loop wash water and closed loop effluent are constantly measured for PAH, 

turbidity and pH-level to ensure compliant running of the scrubber. However, the dis-

charged water also contains other substances, such as nitrates, arsenic, chromium, nickel, 

mercury, and zinc (Teuchies et al. 2020, p. 3). In modelling the discharge water, only PAHs 

and nitrates were used as emission categories. This was due to lack of data on the dis-

charging water quality and the difficulty of calculating reliable averages for the specific 

system configuration. The PAH and nitrate concentrations of the discharge water were 

obtained from Wärtsilä’s technical documentation and data logs provided by the opera-

tor. 

 

 

4.2.4 End-of-Life 

Wärtsilä does not have documentation on recommended procedures for the end-of-life 

activities of the scrubber system. The lifetime of the scrubber system was estimated to 

be 20 years, which is close to the average operational lifetime of tankers, as described in 



48 

chapter 3.2.1. Therefore, the scrubber system is likely to be scrapped and disposed or 

recycled along with the tanker. Ships are scrapped mostly in Bangladesh, Pakistan, India, 

China and Turkey and the industry can recycle up to 90-95% of the scrapped materials 

(Barua et al. 2018, p. 30880).  

 

The operator of the studied system was not able to provide plans for the end-of-life ac-

tivities for the system. The studied system consists of materials that are for the most part 

recyclable, such as stainless steel and copper. However, the Ecoinvent database only con-

tained material recovery processes suitable for the electronic equipment and iron in the 

system. Therefore, the end-of-life activities for the rest of the materials were modelled 

in OpenLCA with Ecoinvent waste incineration and landfill processes that included trans-

portation to the facilities. The used processes for each material are described in table 7. 

 

Table 7. End-of-life activity processes for each material. 

 
Material End-of-life process 

Scrap aluminium Waste incineration 

Scrap copper Waste incineration 

Scrap steel Inert material landfill / waste incineration  

Scrap tin sheet Waste incineration 

Waste iron Recycling via sorting facility 

Waste plastic Waste incineration 

Waste polyvinylchloride product Unsanitary landfill / waste incineration 

Waste rubber Waste incineration 

Waste electric and electronical equipment Recycling via shredder facility 

 

 

4.2.5 Inventory data uncertainties 

The life cycle inventory contains assumptions in the inputs in each phase of the life cycle. 

In the first life cycle phase, the raw material extraction and manufacturing of the com-

ponents was modelled with processes from Ecoinvent using the data on material com-

position of the components. The geographical location of the extraction and manufac-



49 

turing was set based on the location of the supplier. The used processes contained aver-

age transportation methods and distances, which might deviate from the actual trans-

portation operations in the supply chains first phase. There was no primary data on the 

raw material extraction or component manufacturing phases apart from the materials 

and supplier locations, which increases the uncertainty of the reliability of the cradle-to-

gate part of the life cycle. 

 

The transportation to shipyard phase was modelled using primary data from Wärtsilä’s 

internal databases which contained accurate data on the delivery of the components 

from supplier to shipyard. Transportation of the six components in the scope that were 

delivered by the shipyard were modelled using assumptions on both transportation dis-

tances and methods which might deviate from the actual logistical processes. The ca-

pacities and emission standard of the lorry transport processes were assumed based on 

the weights and dimensions of the delivered components. Data for padding or other 

protective material for the deliveries was not available, and therefore rigid polyurethane 

foam was assumed to be used in each delivery.  

 

The operational phase was modelled using operational information provided by the case 

customer and Wärtsilä’s technical documentation. The customer provided the systems 

running hours since installation and open loop and closed usage ratio, which were used 

to calculate average running hours for the whole operational phase. The vessel was as-

sumed to run on heavy fuel with a 3,5% sulphur content throughout the phase, since no 

data on actual used fuel types was available. The fuel consumption due to scrubber use 

was calculated using an assumption for the vessel’s fuel consumption in 2022, which was 

obtained from Wärtsilä’s internal database. The fuel type and consumption assumptions 

inputs have major uncertainties, and therefore the created model might deviate signifi-

cantly from the actual operation of the vessel and scrubber. 

 

The usage ratio of different operating modes in the operational phase was based on the 

assumption that the operating company aims to minimize time spent in ports. No data 



50 

was available on the actual operation on different modes, which creates uncertainty to 

the model. The scrubber’s water consumption in different modes depends on many fac-

tors such as the engine loads, fuel type, and whether the exhaust gas is to be scrubbed 

to a level equivalent to 0,1% or 0,5% m/m sulphur content. The model was created using 

constant values for water consumption on different modes, which were obtained from 

Wärtsilä’s documentation. These values were based on certain constant engine loads 

and fuel type. In actual operation the factors determining the consumption change con-

stantly, which makes it difficult to accurately model the entire operational phase. The 

consumption of sodium hydroxide, coagulant and flocculant chemicals also depends on 

operating power and required cleaning efficiency and hence assumptions on the opera-

tional use of the system affect the calculation of these values. 

 

The discharge water and its contents were based on the data logs sent by the customer 

and Wärtsilä’s documentation of the system. The amount of discharge water is directly 

proportional to the scrubbing water use and therefore uncertainties in water consump-

tion data affect also affect the accuracy of the discharge water data. The PAH and nitrate 

concentration of the discharged water in different use modes were modelled as averages 

calculated from the data or other estimates based on the compliant operation of the 

system. The discharge water quality is also dependent on many factors including those 

described on page 44. The most significant factor in the uncertainty of the discharge 

water modelling was the lack of data on heavy metals and other contaminants. 

 

The end-of-life phase was modelled as waste treatment and recycling activities using the 

material inputs from the manufacturing phase as basis for inputs for the treatment ac-

tivities. Therefore, any uncertainties in the first phase inputs affect the quality of results 

in the last phase. Regarding the end-of-life activities, the system has potential to be re-

cycled in most parts, which deviates from the approach and model built in this study. 



51 

5 Impact assessment and interpretation of results 

This chapter demonstrates the impact assessment of the LCA, scenario analysis for the 

different operational use scenarios, and the KPI development based on the results. Un-

less otherwise stated, the results are presented as per functional unit, which was deter-

mined as 1 kg mass of exhaust gas entering the scrubbing process. The LCIA is demon-

strated and interpreted in chapter 5.1, and scenario analysis in chapter 5.2. Chapter 5.3 

contains discussion on completing the objective of initiating the process of developing 

KPIs to improve Wärtsilä’s environmental performance during the first two phases of the 

system’s life cycle. 

 

5.1 Environmental impacts of life cycle phases 

The LCIA was calculated using the ILCD 2011 midpoint+ method in the OpenLCA software. 

Table 8 demonstrates the environmental impacts per functional unit based on the im-

pact categories. The table also contains the percentage contributions of each life cycle 

phase to each environmental impact. The column for the operational phase in the table 

includes separate percentages for open and closed loop operations and their contribu-

tion to the impacts. 

 

As was described in chapter 4.2.3, the ME scrubber was estimated to be operated for 

142 560 hours, AE scrubber for 87 840 hours and the OFB scrubber for 4392 hours during 

the operational phase. The exhaust gas mass flows at MCR load were 60480 kg per hour 

for the ME, 9360 kg per hour for the AEs, and 1800 kg per hour for the OFB. The hourly 

mass flows were used to estimate the total exhaust gas mass flow for the whole opera-

tional phase using the running hours provided by the customer. 

 

Since in real operation the engines are not operated on MCR loads constantly, the flow 

values were multiplied with estimated factors to generate more realistic exhaust gas 

mass flows for the operational phase. For seagoing mode operation hours, the exhaust 

gas mass flow for the ME was multiplied with by a factor of 0,86 and for the AEs by a 



52 

factor of 0,91. For manoeuvring operation hours, the exhaust gas flows for the ME and  

AEs were multiplied by 0,8. For port operation hours, the exhaust gas mass flows for the 

two AEs in use were multiplied with 0,8. The exhaust gas mass flow for the OFB was 

assumed to be 100% in port operation.  

 

Based on the calculations, the total exhaust gas mass flow for the operational phase in 

the baseline scenario was 9,39E+09 kilograms. This equals to an average of 53,59E+03 

kilograms of exhaust gas mass flow every operating hour or approximately 14,89 kilo-

grams every operating second. The generated results in the LCIA are based on the ex-

haust gas flows and represent the total potential environmental impacts per 1 kg of ex-

haust gas flow entering the scrubber system. Thus, the total potential environmental 

impacts of the studied system would be calculated by multiplying the generated results 

in each impact category by the total exhaust gas mass flow for the operational phase. 

 

The V-SOx scrubber system removes particulate matter and sulphur oxides from the ex-

haust gas. The treated exhaust gas is continuously monitored with a CEMS to ensure 

compliance with the IMO Annex VI sulphur regulations. The scrubber system is designed 

to be able to reduce over 97% of the SOx content in the exhaust gas. As described in 

chapter 4.2.3, the scenarios were built assuming a SOx reduction from 3,5% SOx content 

HFO to a level equivalent to using 0,1% sulphur content fuel. 

 

The results of the impact assessment are from the use profile that was created based on 

the running hours provided by the customer. Based on the provided data, in the baseline 

scenario the system is assumed to run on different open loop modes for 99% of the time 

and on closed loop port mode for 1%. The scenario analysis in chapter 5.2 contains re-

sults with increased closed loop operation.  

 

It should be noted that the LCIA only addresses the data that was entered into the life 

cycle inventory based on the scope of the study (ISO, 2006). Therefore, the results do 



53 

not represent the total environmental impacts of the V-SOx system throughout its life-

time. Complementing the scope of the LCA and LCI data are discussed more in chapter 

6. 

 

Table 8. Impact assessment results per functional unit. 

 
Impact category Total 

/ 
FU 

Unit Raw mat. 
& manu-
facturing 

Trans-
porta-
tion 

Operation EoL 

Freshwater eco-
toxicity 

0,0085 CTUe 70,62 % 0,04 % OL 5,07 % 
CL 1,47 % 

22,80 % 

Land use 0,0021 kg C deficit 1,88 % 0,23 % OL 96,65 % 
CL 1,22 % 

0,03 % 

Climate change 0,00014 kg CO2 eq 30,08 % 1,32 % OL 63,19 % 
CL 5,38 % 

0,03 % 

Water resource 
depletion 

7,88E-05 m3 water eq 61,15 % 0,11 % OL 28,70 % 
CL 10,03 % 

0,01 % 

Ionizing radiation 
HH 

5,72E-05 kBg U235 eq 8,56 % 0,21 % OL 88,74 % 
CL 2,49 % 

0,01 % 

Marine eutrophi-
cation 

5,01E-05 kg N eq 0,11 % 0,01 % OL 99,64 % 
CL 0,24 % 

0 % 

Terrestrial eu-
trophication 

2,53E-06 molc N eq 23,39 % 1,43 % OL 71,35 % 
CL 3,84 % 

0,03 % 

Acidification 1,53E-06 molc H+ eq 18,83 % 0,62 % OL 77,21 % 
CL 3,33 % 

0,02 % 

Photochemical 
ozone formation 

9,38E-07 kg NMVOC 
eq 

17,64 % 1,01 % OL 78,31 % 
CL 3,02 % 

0,03 % 

Particulate mat-
ter 

1,25E-07 kg PM2.5 eq 36 % 0,34 % OL 58,09 % 
CL 5,53 % 

0,03 % 

Freshwater eu-
trophication 

5,89E-08 kg P eq 79,69 % 0,07 % OL 14,64 % 
CL 5,59 % 

0,01 % 

Mineral, fossil, 
ren. Resource de-
pletion 

2,06E-08 kg Sb eq 80,56 % 0,06 % OL 18,14 % 
CL 1,24 % 

0 % 

Ionizing radiation 
E (interim) 

3,77E-10 CTUe 4,63 % 0,21 % OL 93,38 % 
CL 1,77 % 

0 % 

Ozone depletion 1,60E-10 kg CFC-11 
eq 

2,47 % 0,21% OL 93,82 % 
CL 3,50 % 

0 % 

Human toxicity, 
non-cancer ef-
fects 

8,14E-11 CTUh 83,41 % 0,29 % OL 13,24 % 
CL 2,99 % 

0,07 % 

Human toxicity, 
cancer effects 

2,48E-11 CTUh 73,38 % 0,12 % OL 23,5 % 
CL 2,98 % 

0,02 % 

 



54 

As shown in table 8, the operational phase produces the most potential environmental 

impacts in ten different impact categories.  In these categories, specifically the open loop 

operation is the most dominant cause for potential environmental impacts. This phe-

nomenon is unsurprising due to the length of the phase and the overwhelming number 

open loop running hours compared to closed loop running hours. 

 

The potential environmental impacts for the remaining six impact categories are domi-

nated by the raw material extraction & manufacturing of components phase of the life 

cycle. The end-of-life phase has significant contribution in the freshwater ecotoxicity im-

pact category but does not significantly affect other potential impacts in other categories 

relative to other phases. Transportation to shipyard phase has no significant contribution 

in any of the categories relative to other phases but it is taken into further consideration 

in chapter 5.3 as it is a process that is under Wärtsilä’s control. Figure 12 illustrates the 

results as contribution percentages for each phase of the life cycle. 

 

 

Figure 12. LCIA results as contribution percentages per phase. 

 



55 

Out of the 16 impact categories assessed in this study, climate change is one that is rep-

resented in all LCIA methodologies (Hauschild et al. 2013, p. 42). The category is assessed 

via GWP100, which is expressed as kilogram of CO2 equivalent per functional unit. GWP100 

presents the accumulated radiative forcing of greenhouse gases relative to the same 

value of CO2 emissions over a 100-year period (Hauschild et al. 2013, p. 42). 

 

In the LCIA results of this study, the climate change impact category results were 0,00014 

kg CO2 eq/FU. The majority (63,19%) of these potential impacts were accumulated by 

open loop operation. The potential impacts from this phase were produced in totality by 

the market process for heavy fuel oil production, which also contains transportation av-

erages. Running the scrubber system increases the fuel consumption of the vessel 

through increased energy consumption, as described in chapter 4.2.3. Therefore, it is 

included in the model although the system itself does not have a combustion process. 

The open loop operation generated 0,088 grams of CO2 eq/FU throughout the life cycle 

of the system. 

 

The other life cycle phase that had significant contribution to the climate change impact 

category was raw material extraction & manufacturing of components. The contribution 

of this phase was 30,08%, which is equivalent to 0,042 grams of CO2 eq/FU. A total of 

70,7% of the potential climate change impacts generated during this life cycle phase 

were accumulated by market processes for electronic component production. Other sig-

nificant contributors in this phase were average metal product and steel product manu-

facturing processes and market processes containing transportation for different grades 

of steel, attributing for 26% of the potential impacts. 

 

Figure 13 shows the top contributors to the impact categories in the raw material extrac-

tion & manufacturing life cycle phase. The bleed-off treatment unit, alkali feed module, 

CEMS, and pH monitoring unit were assumed to be replaced once during the lifecycle of 

the system and therefore their processes in the model were duplicated. These compo-

nents include most of the electronic components in the scope and are also the biggest 



56 

contributors in most of the impact categories. As in the climate change impact category, 

also in almost all other impact categories, the most significant contributions to the im-

pact categories were accumulated by the market processes for electronic component 

production.  

 

 

Figure 13. Top impact contributors in the raw mat. extraction & component manufacturing phase. 

 

Considering the purpose and operating principle of the scrubber system, marine eu-

trophication is an essential impact category to be considered. The impact category 

measures potential impacts with a unit of kg nitrogen equivalent. Nitrogen is considered 

a growth-limiting nutrient that contributes to planktonic growth and eventually to oxy-

gen depletion and hypoxia-related damage especially in coastal waters (Cosme et al. 

2017, p. 676). 

 



57 

Open loop operation contributed for 99,64% of the total impacts in marine eutrophica-

tion category. This is expected due to the ratio of open loop and closed loop usage, and 

their different operating principles. In open loop operation, the amounts of scrubbing 

water and discharge water are the same, which results in increased concentration of 

contaminants discharged into the sea. The discharge water was modelled to contain PAH 

compounds and nitrates. PAH compounds contribute to marine ecotoxicity and cause for 

example immunotoxicity, embryonic abnormalities, and cardiotoxicity in marine wildlife 

(Honda & Suzuki, 2020, p. 2). In terms of marine eutrophication, the more significant 

contaminants are nitrates, which contributed for over 99% of the open loop impacts. 

Nitrate is nitrogen in an oxidized form (NO3
-) and accounts for most of the fixed nitrogen 

in the oceans (Zakem et al. 2018, p. 2).  The total potential impacts in marine eutrophi-

cation impact category for open loop operation were 0,049 grams of N eq/FU. The sce-

nario analysis in chapter 5.2 analyses marine eutrophication in scenarios with increased 

closed loop usage.  

 

5.2 Scenario analysis 

The scenario analysis contains two additional use scenarios for the V-SOx scrubber sys-

tem. In the first additional scenario, the system was assumed to operate in closed loop 

manoeuvring mode for 10% of the running hours and in closed loop port mode for 5% 

of the running hours. In the second additional scenario, the closed loop manoeuvring 

mode accounted for 30% of the running hours and closed loop port mode for 5%. Rest 

of the running hours were assumed to be operated on open loop seagoing mode in both 

scenarios. The scenario analysis was conducted to gain results on closed loop operation 

and its potential for environmental impacts. The results in the scenario analysis were 

calculated