Alternative fuels for shipping
Feasibility study in Singapore
Beatrice Foscoli
Master of Science Thesis TRITA-ITM-EX 2020:350 KTH School of Industrial Technology and Management
Division of ENERGY TECHNOLOGY SE-100 44 STOCKHOLM
Master of Science Thesis TRITA-ITM-EX 2020:350
Alternative fuels in Shipping
Feasibility study in Singapore
Beatrice Foscoli
Approved Examiner
Andrew Martin
Supervisor
Jens Fridh
Commissioner
University of Cambridge
Contact person
Epaminondas Mastorakos
Abstract
This thesis work was performed as a collaboration between the University of Cambridge and the Royal Institute of Technology and was initially intended to be performed as a 5-months
internship at the CREATE Centre of Singapore. Unfortunately, due to the COVID-19 pandemic, it could only be done remotely.
The aim of the research is to investigate the use of alternative fuels for shipping in Singapore, as maritime power in a global process of decarbonization of this sector.
A range of alternative fuels and technologies with different carbon reduction potentials, depending on the primary energy source, have been proposed for ships to reduce emissions.
The overall ambition of the project has been to carry out a comprehensive study, based on existing academic and industry literature, on the technical viability of alternative marine fuels tailored to the context of Singapore.
The approach of the study has been to assess how a selection of alternative fuels performs on a set of parameters. The alternative fuels included are hydrogen (H2), ammonia (NH3), methanol (MeOH1), biodiesel (FAME) and liquefied natural gas (LNG).
LNG offers a good compromise between energy consumption for its production and reduction of emissions but will not be able to meet carbon coals in the long term. Bio-MeOH from woody biomass finds large applicability in Singapore given the abundance of feedstock in the South East Asian region and can deliver relevant CO2 emissions reduction. However, as for biodiesel, sustainability and availability concerns might rise questions on its impact as viable long-term solution. E-fuels, under renewable resources production, can deliver significant environmental benefits but at the moment seem to be inaccessible to Singapore considering the amount of clean electricity needed for their production.
Results show that the main challenge for Singapore towards the decarbonization of shipping is the procurement of primary resources. Ensuring energy security in a sustainable way in a post- pandemic context like South East Asia, where the priority for the coming 30 years will be an unprecedented economic boom, will first and foremost see Singapore engaged in international policies and collaboration in support of emerging economies.
Sammanfattning
Detta avhandlingsarbete utfördes som ett samarbete mellan University of Cambridge och Kungliga Tekniska Högskolan och var ursprungligen avsett att utföras som en 5-månaders praktik vid CREATE Center i Singapore. Tyvärr, på grund av COVID-19-pandemin, kunde det bara göras på distans. Syftet med forskningen är att undersöka användningen av alternativa bränslen för sjöfart i Singapore som maritim kraft i en global process för avkarbonisering av denna sektor. Ett antal alternativa bränslen och tekniker med olika
koldioxidreduktionspotentialer, beroende på den primära energikällan, har föreslagits för fartyg för att minska utsläppen. Projektets övergripande ambition har varit att genomföra en
omfattande studie, baserad på befintlig akademisk och industriell litteratur, med den tekniska tillgängligheten av alternativa marina bränslen anpassade till Singapore. Studiens
tillvägagångssätt har varit att bedöma hur ett urval av alternativa bränslen presterar på en uppsättning av parametrar. De alternativa bränslena som ingår är väte (H2), ammoniak (NH3), metanol (MeOH), biodiesel (FAME) och flytande naturgas (LNG). LNG erbjuder en bra
kompromiss mellan energiförbrukning för sin produktion och minskning av utsläpp men kommer inte att kunna möta fossilt kol på lång sikt. Bio-MeOH från ved-biomassa finner stor
tillämpbarhet i Singapore med tanke på överflödet av råmaterial i Sydostasien och kan ge relevant CO2-utsläppsminskning. Vad gäller biodiesel kan emellertid problem med hållbarhet och tillgänglighet väcka frågor om dess inverkan som en långsiktig lösning. E-bränslen, under produktion av förnybara resurser, kan ge betydande miljöfördelar men verkar för tillfället vara otillgängliga för Singapore med tanke på hur mycket ren el som behövs för deras produktion.
Resultaten visar att den största utmaningen för Singapore mot avkarbonisering av sjöfarten är upphandling av primära resurser. Att säkerställa energisäkerhet på ett hållbart sätt i ett post- pandemiskt sammanhang som Sydostasien, där prioriteringen under de kommande 30 åren kommer att vara en oöverträffad ekonomisk boom, kommer först och främst se Singapore engagerade i internationell politik och samarbete till stöd för tillväxtekonomier .
Acknowledgments
I would like to begin by expressing all my gratitude to prof. Epaminondas Mastorakos for giving me the opportunity to do this MSc thesis work with the University of Cambridge. I could have not hoped for a more caring and attentive guide to accompany me during my work and all the unforeseen events I had to deal with in the last months.
Thanks to Maran Tankers Management for some useful discussion on future shipping.
Additionally, I would like to thank Jens Fridh from the KTH Energy Technology Department for accepting to supervise me during my MSc thesis work.
Lastly, I would like to thank my friends Antonio and Lorenzo for their limitless support and encouragement during this last year.
Genoa, June 2020 Beatrice Foscoli
Table of Contents
Abstract ... 3
Acknowledgments ... 5
Table of Contents ... 6
Abbreviations ... 7
List of Symbols ... 8
List of Figures ... 9
1. Introduction ... 10
1.1 Background ... 10
1.2 Problem Description ... 11
1.3 Objectives... 11
2. Methods ... 12
2.1 Overview ... 12
2.2 Sources of data ... 13
2.3 Literature Review ... 13
2.4 Assumptions ... 20
2.5 Calculation Overview ... 22
2.6 Example calculation: H2 ... 23
3. Results ... 26
3.1 Hydrogen... 26
3.2 Ammonia ... 27
3.3 MeOH ... 28
3.4 Biodiesel ... 29
3.5 LNG ... 30
3.6 Sensitivity analysis ... 30
3.7 Summary of results ... 32
4. Discussion ... 38
4.1 Scenarios ... 38
4.2 Recommendations for policymakers... 47
5. Conclusions ... 51
5.1 Conclusions from this work ... 51
5.2. Recommendations for Future Work ... 52
6. Bibliography ... 53
7. Appendix ... 58
Abbreviations
AEC – Alkaline Electrolysis Cell
APG - Association of Southeast Asian Nations’ Power Grid ASEAN - Association of Southeast Asian Nations
Bcm – Billion Cubic Meter
CCS - Carbon Capture & Storage CO – Carbon Monoxide
CO2 – Carbon Dioxide
CO2, eq – Carbon Dioxide Equivalent DAC – Direct Air Capture
DAFC – Direct Alcohol Fuel Cell EMA - Energy Market Authority FAME - Fatty Acids Methyl Esters FC – Fuel Cell
FTT – Field to Tank
GDP - Gross Domestic Product GHG - Greenhouse Gas
GST – Goods and Services Tax HFO - Heavy Fuel Oil
H₂ – Hydrogen
ICE - Internal Combustion Engine
IGF – International Code for ships using Gases or other Low-flashpoint Fuels IMO- International Maritime Organization
LHV - Lower Heating Value LNG - Liquified Natural Gas MeOH - MeOH
MFO - Marine Fuel Oil MGO - Marine Gas Oil MPA - Marine Port Authority
MTOE – Million Tonsnes of Oil Equivalent
Mtons – Million Tons NG – Natural Gas NH3 – Ammonia NOx – nitrogen oxide
NUS – National University of Singapore PEM - Protons Exchange Membrane PM – Particulate Matter
SMR - Steam Methane Reforming TRL – Technology Readiness Levels TTP – Tank to Propeller
UN – United Nations WTT- Well to Tank WTP – Well to Propeller
List of Symbols
𝜂𝜂𝑒𝑒𝑒𝑒 – electric efficiency
𝜂𝜂𝑒𝑒−𝑒𝑒𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙 – electrolysis efficiency
𝜂𝜂𝑒𝑒𝑒𝑒𝑒𝑒 – ICE efficiency
𝜂𝜂𝑒𝑒𝑒𝑒𝑒𝑒+𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 – engine with cracking efficiency
𝜂𝜂𝑓𝑓𝑐𝑐 – fuel cell efficiency 𝜂𝜂𝐻𝐻𝐻𝐻 – Haber-Bosch efficiency
𝜂𝜂𝑆𝑆𝑆𝑆𝑆𝑆 – steam methane reforming efficiency
𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 – total capacity
𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 – total carbon emissions
𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 – energy from bunker HFO
𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝 – propulsion energy
𝐶𝐶𝑙𝑙 – energy from alternative fuel i 𝐶𝐶𝑒𝑒𝑒𝑒 – electricity
𝑚𝑚𝑙𝑙 – alternative fuel i mass
𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡 – tons of bunker HFO
List of Figures
Figure 1: Alternative fuels and energy sources considered in this paper ...14
Figure 2: Schematic of H2 production mechanisms, with typical efficiencies included. ...14
Figure 3: Schematic of H2 production mechanisms via cracking of ammonia (The Royal Society, 2020). ...15
Figure 4: Schematic of NH3 production mechanisms via conventional Haber-Bosch (The Royal Society, 2020) ...16
Figure 5: Schematic of NH3 production mechanisms via renewable Haber-Bosch (The Royal Society, 2020) ...16
Figure 6: Schematic of bio-MeOH production mechanisms (The MeOH Institute, 2020) ...17
Figure 7: Schematic of e-MeOH production mechanism (The MeOH Institute, 2020) ...18
Figure 8: Biofuels production pathways (Neste Group, 2016) ...19
Figure 9: Schematic of marine fuel LCA from well to propeller (Bengtsson et al., 2011) ...21
Figure 10: Schematic of calculations of the energy at the propeller ...22
Figure 11: Schematic of H2 electrolysis energy flow ...23
Figure 12: Schematic of SMR energy flow ...25
Figure 13: Schematic of H2 production calculations with used efficiencies included. ...26
Figure 14: Schematic of NH3 production calculations with used efficiencies included ...27
Figure 15: Schematic of MeOH production calculations, with used efficiencies included. ...28
Figure 16: Schematic of biodiesel production calculations, with used efficiencies included. ...29
Figure 17: Schematic of LNG production calculations, with used efficiencies included. ...30
Figure 18: Sensitivity Analysis of H2 resources consumption ...31
Figure 19: Sensitivity Analysis of H2 CO2 emissions ...31
Figure 20: Schematic of H2 production calculations in 2050 ...32
Figure 21: Energy needed vs. Energy available in Singapore ...33
Figure 22: Extra energy needed for alternative fuels production. ...34
Figure 23: Total CO2 emissions of alternative fuels LCA. ...35
Figure 24: Specific CO2 emission of alternative fuels in shipping ...36
Figure 25: Specific CO2 emission of alternative fuels in shipping (DNV GL Maritime, 2019) ...36
Figure 26:TRL ranking for H2 technologies (Lloyd’s Register and UMAS. 2020). ...41
Figure 27:TRL ranking for NH3 technologies (Lloyd’s Register and UMAS. 2020). ...43
Figure 28: TRL ranking for MeOH technologies (Lloyd’s Register and UMAS. 2020). ...44
Figure 29: TRL ranking for biodiesel technologies (Lloyd’s Register and UMAS. 2020). ...45
Figure 30: Singapore bunker HFO 2018 calculation sheet (MPA, 2019) ...58
Figure 31: Singapore Solar PV calculation sheet (EMA, 2019) ...58
Figure 32: H2 data sheet (comparison with HFO) ...58
Figure 33: NH3 data sheet (comparison with HFO) ...59
Figure 34: MeOH data sheet (comparison with HFO) ...59
Figure 35: Biodiesel and LNG data sheet (comparison with HFO)...60
Figure 36: Singapore’s available resources used as reference in calculations ...61
Figure 37: Singapore Electricity Balance 2018 (EMA,2019) ...61 Figure 38: The future of Singapore's Energy Story (Energy Market Authority of Singapore, 2019)
1. Introduction 1.1 Background
Decarbonizing the maritime industry
Today, 90% of world trade is conducted by sea. Maritime transport alone is responsible for about 3% of global GHG, producing roughly the same amount that Germany or Brazil produce each year (around 940 million tons2 of CO2 annually) and, due to international trade’s rise in emerging countries, it could increase to 17% by 2050 if no action is taken to mitigate (Martin CAMES, 2015) . Nonetheless, emissions from shipping are not covered by the Paris Climate Agreement because they are not creditable to any nation (OECD, 2018).
In April 2018, in order to align the sector with the Paris Agreement climate goals, the United Nations regulatory agency for the maritime industry, the International Maritime Organization (IMO), first adopted a strategy to reduce GHG emissions from shipping, establishing a target for global shipping to decarbonize by at least 50% from 2008 levels by 2050. The IMO 0.5 wt%
sulfur limit for marine fuels just came into force on 1st January 2020 to reduce sulfur emissions by over 80%, banning ships from using fuels with a sulfur content above 0.5%, compared with the previous limit of 3.5% (The International Chamber of Shipping (ICS), 2019) and, acting like an implicit carbon price it increases the costs of carbon-intensive shipping, thus the
attractiveness of lower-carbon ships.
Port of Singapore - Asia’s gateway
Founded in 1800, the Port of Singapore is known to be a leading center for shipping. Located at the crossroads of East-West trade, Singapore's strategic location in the heart of Asia allows the region to become a strategic center for maritime trade. Thanks to its excellent reputation in the maritime industry, combined with sophisticated port facilities, shipyards and various services, Singapore has developed into an International Maritime Centre (IMC) (Singapore Information Services, 2020). Located in the center of a trade route network and connected to 600 ports in over 120 countries, Singapore offers shipping companies global commercial connectivity.
Singapore is the busiest port in the world in terms of shipping tonnage, with over 130,000 calls per year and, although Singapore does not produce any oil, it is the top bunkering (ship
refueling) port in the World. Today, there are more than 5,000 maritime establishments contributing about 7% of Singapore's gross domestic product and employing about 170,000 personnel (Maritime and Port Authority of Singapore, 2020).
In 2019, Singapore consolidated its global position as one of the world's most important commercial maritime destinations - along with Hong Kong, London, Shanghai and Dubai - surpassing the ISCD (Xinhua-Baltic International Shipping Centre Development) index for the sixth consecutive year (Offshore Energy, 2019).
2 Referring to ‘metric tons’
Singapore: an “alternative-energy disadvantaged”
Despite its significant efforts in addressing climate change, Singapore’s alternative-energy disadvantaged status is also recognized by the UNFCCC (UNFCCC, 2015) . Singapore is an island city-state of only 719 km² in size with relatively flat land, low wind speed and lack of geothermal resources. Albeit in a tropical region, land constraints also make solar power on large scale challenging to deploy. Thus, improving energy efficiency and looking into emerging low-carbon solutions are for Singapore the only feasible ways to achieving the decarbonization goals set out for 2030 (UNFCCC, 2015). Within the maritime industry, this mainly results in the adoption of alternative fuels with combined use of carbon capture technologies where
necessary.
The future decarbonization of shipping is therefore both a trend that Singapore will need to react to, and potentially an opportunity for new forms of value creation related to future bunkering.
1.2 Problem Description
The decarbonization of the shipping sector is inevitable, but also one of the most difficult to achieve (Energy Transition Commission, 2018), especially in a context where alternative resources are as scarce as in Singapore. At present, low or zero carbon propulsion
technologies are not widely available, most of the world’s shipping fleet still relies on diesel and the questionable slow steaming (Walker, 2019) and scrubbers are so far the most effective ways to reduce GHG from ships in the short term (Patrizia Serra, 2020). The decarbonization of the marine sector raises important questions on the bunkering activities that are a foundation to the economy in Singapore. A shift to non-conventional propulsion modes questions about the future of HFO, which is today almost 80% of the total bunker fuel oil (Maritime and Port Authority of Singapore, 2019).
Which are the suitable alternatives for Singapore to adapt to this trend?
Predictions of which technologies may dominate are currently poor, while the choice will have profound impacts on Singapore energy plan and policy and port and industrial policy.
1.3 Objectives
We often talk about the urgent need to get rid of fossil fuels, but have we ever wondered whether the resources we have available are sufficient to make it happen? And if not, which actions should be taken by the government to secure sufficient supply of primary resources? In this proposal, a feasibility study of the most promising alternative fuels in replacement of the current bunker HFO for shipping applications in Singapore is performed. The specific objectives are set as:
1. Analysis and comparison of alternative fuel solutions across the multiple dimensions of CO2 emissions, energy consumption and potential for the economy of Singapore.
2. Development of understanding the measures to be taken by Singapore policymakers for each of the alternative fuels studied in the form of “Fuel Scenarios”
3. Key findings and recommendations for Singapore policy makers
The assessment aims to provide Singapore stakeholders with a clear and perhaps somewhat unusual view of alternative fuels role and potential and of the further efforts needed to achieve
discussion on alternative fuels tailored to the context of Singapore, as a maritime global leader.
The results are novel and will be disseminated in the scientific literature but will also inform various Singapore stakeholders concerning energy policy and future economy planning.
2. Methods 2.1 Overview
Bunkering is the process of supplying fuels to ships for their own use and Singapore is one of the largest and most important bunkering ports in the world (Maritime and Port Authority of Singapore, 2020). In 2019, with the maritime industry contributing about 7% of Singapore’s GDP, Singapore bunker sales, according to the MPA statistics, accounted for more than 47 million tons of marine fuel, 79% of which are MFOs, high sulfur content residual fuels (Maritime and Port Authority of Singapore, 2019). Committed to the objective of cutting emissions from the sector by at least 50% by 2050, on 1st January 2020 the IMO 0.5 wt% sulfur limit for marine fuels came into force to reduce sulfur emissions (Wood Mackenzie, 2018). This will ultimately require all waterborne vessels to make a rapid switch from HFO to low burning fuels such as MGO or so called “alternative” fuels, which leads us to believe that in 2020 statistics MFO bunker sales will suffer a significant collapse.
But given that the age of fossil fuels is coming to an end, Singapore needs to find suitable solutions to react to this trend.
The first step taken to answer those questions is to calculate how much alternative fuel is needed to supply the same propulsion provided today by bunker HFO and, secondly, how much energy is needed to produce such fuel. The purpose of those calculations is, in fact, to assess the feasibility of the most promising alternative marine fuel options in the context of a
decarbonized Singapore, if these were to replace the bunker sales of HFOs to comply with IMO2050.
The research was carried out through a comprehensive literature review to collect a wide range of content relevant for the establishment of the production pathways (from energy source to fuel converter) of the fuels in analysis. Through a categorization and evaluation process the most relevant references were selected and the pathways established with related assumptions (section 2.4 Assumptions. Note that within allpotential technology pathways, only mature, as well as pathways that are expected to mature during the next five to ten years are included in this study.
The scope of this work has been to identify and summarize existing literature on the topic of alternative fuels to be able to evaluate their performance and feasibility with Singapore as a boundary.
2.2 Sources of data
This project based the performance comparison of alternative fuels for marine applications on online literature research.
Given that alternative fuels, as much as one hears about it, with regards to marine applications are still at an early stage (Lloyd's Register and UMAS, 2020), it was challenging to find the numbers and parameters needed for calculation purposes. In fact, as many publications released by official bodies (e.g. IMO) and universally accredited agencies (e.g. DNV GL) as there are to explain the objectives set by the IMO and the various scenarios that can be pursued between now and 2050, and although all major engine and ship manufacturers (e.g. MAN Diesel & Turbo, Wärtsilä) are talking about ambitious future projects for decarbonization, finding concrete figures and quantitative forecast for the future to come has been often difficult. Within the described processes, for instance, the conventional steam methane reforming (SMR) and the Haber-Bosch ammonia synthesis are well known and consolidated (The Royal Society, 2020), thus reliable numbers and efficiencies are accessible. However, the uncertainty arises when applied specifically to the maritime sector which has largely yet to be explored.
Several targeted literature searches were conducted in attempt to close any gaps of missing data or a low number of sources, however, for some parameters on certain fuels, the literature search did not uncover any reliable available data, either because this data is not available or does not exist, or because it was not discovered in the literature study.
For more innovative solutions, such as direct-fuel cells for ammonia and MeOH or ammonia cracking for example, numbers and efficiency, are rather uncertain and, when estimable, reasonably subject to change in the coming years. How they will change is unknown yet.
Therefore, due to a lack of forecast data available, the sensitivity analysis performed is limited to the expected improvement in H2 fuel cells efficiencies.
It should be pointed out that the scarcity of information and the protection exercised by the government over its own data has often forced the use of poor sources such as websites. Most of the figures about Singapore used for data collection are taken from Singapore Government websites, like the “Energy Market Authority” and the “Maritime & Port Authority”.
2.3 Literature Review
In this section, the alternative fuels investigated in the research are discussed and several pathways for their production are presented as shown in Figure 1: Alternative fuels and energy sources considered in this paper
Figure 1: Alternative fuels and energy sources considered in this paper
2.3.1 Hydrogen
H2 can be produced from water electrolysis or SMR and used in FCs or ICEs (McKinlay, 2020).
Both production processes including a brief word to the cracking of the ammonia are analyzed, while only direct use in PEM FC is evaluated since so far, despite fundamental design changes for ships to use an electric motor, is said to be the most efficient and economical method for extracting energy from H2 in the long term (McKinlay, 2020).
● Electrolysis
Figure 2: Schematic of H2 production mechanisms, with typical efficiencies included.
The electricity needed could either come from the grid (more than 95% produced from NG, in Singapore (Energy Market Authority (EMA), 2019)) or from renewable sources which, in the Singaporean context, means solar PV. In fact, the scarcity of available land and the low wind speed range make the development of wind power implausible, there are no hydro resources and mean tidal range are low (Energy Market Authority (EMA), 2019). To make an approximate calculation of the installations (residential and non-residential) needed in the next years to supply this amount of electricity, yearly statistics on solar are made available by the Energy Market Authority (EMA) (see Figure 31: Singapore Solar PV calculation sheet (EMA, 2019).
● Ammonia Cracking
Figure 3: Schematic of H2 production mechanisms via cracking of ammonia (The Royal Society, 2020).
H2 can be also cracked from ammonia, when the latter is used as a virtual H2 carrier, obtained by electrolysis and Haber-Bosch and used in a PEM FC. In this case, H2 production efficiency shows lower values causing a decrease of the overall efficiency of the process (S. Giddey, 2017).
Ammonia production is discussed separately in section 2.3.2 Ammonia.
● Steam methane reforming (SMR)
Steam reforming converts methane into H2 and CO by reaction with steam over a nickel catalyst. Electrolysis using renewable energy is in fact a promising solution for clean H2, but thermochemical conversion of conventional fuels remains significantly cheaper. Therefore, if H2 is to play a role in shipping decarbonization (and not only), steam reforming using NG as a feedstock implies coupling it with CCS, thus it would require a higher consumption of NG but this calculation is not performed in the research (New York State. Energy Research and Development Authority, 2006).
2.3.2 Ammonia
Produced via Haber-Bosch consolidated process using fossil fuels (mainly NG) or renewable electricity, similarly to H2, NH3 can be used as a transport fuel by direct combustion in an engine or by chemical reaction in a FC (directly or after cracking) to produce electricity (The Royal Society, 2020). However, the latter utilization is still under development and at this stage there are no commercially available FCs which utilize NH3 as a fuel (directly or indirectly), thus it is not considered in this research (S. Giddey, 2017).
Albeit with a few modifications, NH3 can be used as a fuel in ICE (compression ignition or spark ignition) and although pure NH3 combustion is feasible, several aspects like high compression ratio for compression ignition, low flame speed and low flame stability make NH3 - H2 mixtures preferable to pure NH3 (De Vries, 2019). Therefore, only NH3 - H2 mixtures in ICE, where NH3 is cracked into H2 before the combustion, is investigated further in this project.
The two Haber-Bosch processes, the conventional one using NG and the one using renewable electricity, are discussed as potential solutions to produce the necessary NH3.
● Conventional Haber-Bosch process (NG)
Figure 4: Schematic of NH3 production mechanisms via conventional Haber-Bosch (The Royal Society, 2020)
NH3 is currently mostly produced by the highly energy and carbon intense Haber-Bosch process using H2 reformed from NG (72% of NH3 global production from NG (A Valera-Medina, 2018)).
However, most of the energy consumed and 90% of the emission are due to H2 and for this reason NH3 synthesis is often coupled with H2 production to increase the efficiency (The Royal Society, 2020), but this is not being discussed in this research.
● Renewable energy Haber-Bosch process
Figure 5: Schematic of NH3 production mechanisms via renewable Haber-Bosch (The Royal Society, 2020)
Alternatively, NH3 synthesis Haber-Bosch can use H2 produced by an electrolyzer operated with electricity from renewable energy sources as a feedstock. The energy consumption by this route is higher than conventional Haber-Bosch and the electrolysis efficiency is around 0.5. The carbon footprint in case of renewable electricity usage for H2 production steeply decreases compared to the fossil route: more than 70% of CO2 emissions are feedstock related indeed (The Royal Society, 2020).
2.3.4 MeOH
Compared with methane, which needs to be liquefied and kept at sub-zero temperatures, MeOH remains liquid at ambient temperature. On the top of that, it is sulfur-free, thus no sulfur oxide
emissions are produced during combustion (Prof. Karin Andersson, 2015). Up to date MeOH is mainly produced from synthesis gas generated by reforming NG (SMR). Syngas can
alternatively be produced from biomass undergoing fermentation or gasification. A low-carbon pathway to e- MeOH, MeOH based on H2 production through electrolysis with low-carbon electricity followed by CO2 hydrogenation, is also available (Michael Matzen, 2015). The three processes are discussed as potential solutions to produce the required amount of MeOH.
MeOH can be used in pure form or as a blend component in ICEs achieving efficiencies similar to diesel combustion or in dedicated FCs (Winebrake, 2018). This review focuses on the use of MeOH as a pure fuel only in a two-stroke diesel-cycle engine, the only type which is currently commercially available (DNV GL 2019, 2019) .
● Conventional SMR
The traditional process for producing MeOH consists of syngas production followed by its conversion into MeOH and distillation. This pathway is consolidated and well-known, providing efficiencies around 75% (Michael Matzen, 2015).
● Bio-MeOH
Figure 6: Schematic of bio-MeOH production mechanisms (The MeOH Institute, 2020)
Most of the technologies for MeOH production that use biomass as feedstock are similar to those adopted when fossil fuels are used as raw materials. Biomass is usually dried and grinded to obtain small and uniform particles. Within all methods of biomass utilization, gasification is by far the most used in the Singapore area (Maw Maw Tun, 2019). Although all biomass sources can be gasified (waste wood, municipal solid waste, etc.), low-moisture materials are the most suitable for such purposes and provide efficiencies up to 55% (Michael Matzen, 2015). For the calculations, biomass from forestry residues is assumed as feedstock. In such a process, the emissions from MeOH production comes from the emissions generated elsewhere to create electricity needed, thus the source of electricity is a crucial factor for the total GHG of MeOH
from biomass. However, emissions of CO2 from combustion (TTP) of MeOH from renewable feedstock, as explained in 2.4 Assumptions, are taken to be zero.
● e-MEOH
Figure 7: Schematic of e-MeOH production mechanism (The MeOH Institute, 2020)
The e-MeOH pathway aims at synthesizing MeOH entirely from renewable resources: H2
originates from water electrolysis where the electricity is renewable as well. Then, H2 is combined with captured CO2 to produce MeOH with a low C-footprint (Prof. Karin Andersson, 2015). As in ammonia synthesis, water electrolysis is also the most energy intensive step in the production chain. Despite having a substantially higher total energy demand, the CO2 footprint contribution of the low-carbon process is large, leading to 90% CO2 emissions reduction compared to conventional MeOH (Carbon Recycling International, 2017).
2.3.5 Biodiesel
Biofuels refers to liquid or gaseous fuels produced from biomass. After coal, oil and NG, biomass stands as the world’s fourth-largest energy source. Among all available biofuels, the one of greatest interest for maritime application due to its compatibility with internal combustion diesel engines is biodiesel, typically referring to FAME (vegetable oils and animal fats
esterification): it can be blended with marine distillate and it is applicable with existing ships and bunkering infrastructure with minor modifications. It is also the readiest alternative fuel for actual application in the shipping industry (Thepsitha, 2017). The hydrotreating of vegetable oils (HVO) is a more recent alternative to FAME biodiesel, showing higher heating values (43 MJ/kg vs. 38 MJ/kg) and lower life cycle greenhouse gas emissions than those of FAME if both are made from the same feedstock (Neste Group, 2016).
Figure 8: Biofuels production pathways (Neste Group, 2016)
A large variety of processes exist to produce conventional (1st generation) and advanced (2nd and 3rd generation) biofuels, involving a variety of feedstocks and conversions. In the
geographical context of Asia-Pacific and Singapore in particular, palm oil imported from
Malaysia and Indonesia and animal fats and oils imported from New Zealand and Australia are the predominant feedstocks for biodiesel production (1st generation biofuels). In fact, the global fats & oils market is driven by the demand from Asia-Pacific countries, particularly India, China, Malaysia, and Indonesia, where rising in living standards and population growth, coupled with an increased focus on biofuels, is boosting the demand for them (Markets and Markets, 2016).
From an environmental perspective, biodiesel does not contain sulfur and therefore its combustion does not emit sulfur oxides. GHG emission reduction compared to fossil diesel varies from 30% to 90%, with upper levels being attributed to wastes and non-edible oils and lower levels to efficient vegetable crops (Jungmeier, 2016) . However, biodiesel in the Asia- Pacific area, belonging predominantly to 1st biodiesel generation, has an overall relatively low CO₂ reduction potential due to land utilization and food industry competition (Nophea Sasaki, 2009).
Among all biofuels, only biodiesel is considered in view of its suitable application to the maritime industry (Thepsitha, 2017). As a simplification, biodiesel is treated as a drop-in fuel3 throughout the calculations.
2.3.6 LNG
LNG generally refers to natural gas, containing mostly methane (CH4), converted to liquid form and stored at -160 ⁰C. NG is ranked third for the abundance after coal and oil (Verbeek, 2011).
Among available LNG fuel propulsion options, the diesel-ignited gas engine with dual fuel capability (NG-fuel oil) is considered for coherence with the assumptions in section 2.4
Assumptions. Fuel tanks and safety systems needed on LNG fueled ships are not evaluated in this review.
LNG is the cleanest fossil fuel available, but methane slip could cancel out its beneficial effect of GHG reduction (Maritime Energy & Sustainable Development Centre of Excellence, 2020).
However, today most of the energy consumption of ships occurs in two-stroke engines and, based on engine manufacturer’s data, methane slip is less of an issue in two-stroke engines than in four-stroke engines (DNV GL Maritime, 2019). Moreover, according to MAN Diesel &
Turbo, low-speed diesel engines with high- pressure injection have found to have almost no methane slip (0.1% of SFOC). Therefore, assuming the use of this type of engine, the effect of methane leakage can be overlooked during the investigation.
2.4 Assumptions
For a modeling exercise, a reasonable amount of assumptions is required.
● Vessel Type
○ Deep-sea shipping4 which comprises large ocean-going ships and which is responsible for 80% of the global fleet’s CO2 emissions (DNV GL, 2018).
○ Since large cargo ships are responsible for most of the maritime fuel
consumption and emissions (IEA Bioenergy, 2017), the vessel considered is a large cargo ship.
● Engine
○ ICE slow-speed, 2-stroke engine (typically used for propulsion in large vessels (DNV GL 2019, 2019)) .
○ The engine efficiency is based on an engine load of 25%-100%.
○ This study has not accounted for the energy required for auxiliary power (on- board systems). It is assumed that all the fuel energy is used for propulsion.
● Conversion process
○ Throughout the candidates promising technologies only Protons Exchange Membrane (PEM) fuel cells (FC) systems for H2 conversion are considered.
Other alternative technologies have been excluded due to societal challenges (e.g. nuclear power), operational challenges (e.g. wind-assisted propulsion) or because they are more suitable for short-sea shipping (e.g. batteries).
○ Only conventional ICEs are considered for fuels other than H2 (H2 is most
efficiently utilized in fuel cells (Staffell, 2019)). Direct Alcohol Fuel Cells (DAFCs) and H2 FCs for NH3 and MeOH must mature to become commercially viable on a large scale (DNV GL 2019, 2019). This option has significant potential in the long term, but the paths are not covered in this study.
● Fuels
○ Fuels produced from renewable electricity are referred to as electro-fuels and are prefixed by an 'e'5.
○ Only LNG and liquid fuels are investigated (all the H2 options store H2 as liquid).
4 Refers to the maritime transport of goods on intercontinental routes, crossing oceans; as opposed to
‘short sea shipping’ over relatively short distances (Danish Ship Finance, 2020)
5 Often refers to them also as Power-to-X (PtX)
● Emissions
○ In Singapore, the most significant GHG is CO2, primarily produced by fossil fuels burning (National Environment Agency, 2020). For this reason, only CO2 (and not CO2, eq) are calculated in the research.
○ The life cycle of marine fuels is measured from well-to-propeller (WTP) or field- to-propeller (FTP) for fossil fuels and biofuels, respectively. The first stage (WTT or FTT) consists of extraction, production, and transportation, the second (TTP) consists of emissions from fuel combustion on board (Figure 9: Schematic of marine fuel LCA from well to propeller (Bengtsson et al., 2011)
Figure 9: Schematic of marine fuel LCA from well to propeller (Bengtsson et al., 2011)
○ TTP CO2 emissions are considered null for fuels produced from renewable feedstock (biomass included) since the amount of CO2 released during combustion is the same as that captured by the plant during growth (biogenic origin). This is consistent with the EU Renewable Energy Directive (2009/28/EC) rules for calculating the GHG impact of biofuels.
○ Carbon Capture & Storage technologies (CCS) are the only way to make NG- fuels, biodiesel, and LNG zero-carbon. However, the inclusion of CCS is not considered in the calculations due to very limited data available. In terms of emissions, it is likely that the NG-derived fuel (CCS) pathway would lie between the NG-derived fuel (no CCS) and e- pathways (DNV GL 2019, 2019) .
○ Direct Air Capture (DAC), with CO2 directly captured from air, can help achieving negative emissions or, if combined with H2 , used for e-fuels production (IEA, 2020). Yet it is not considered in the research, given its early stages.
2.5 Calculation Overview
Figure 10: Schematic of calculations of the energy at the propeller
The calculation is carried out by replacing today's energy at the propeller, which is produced by bunker HFO combustion, with the same energy but delivered through a low-carbon energy carrier.
Hence, if 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 is the total energy available from the bunker HFO in a year, 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 = 𝐿𝐿𝐿𝐿𝐿𝐿 ∗ 𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡 (1)
where 𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡 are the tons of HFO delivered yearly by Singapore’s bunkering activities. If 𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝 is the total energy at the propeller,
𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝 = 𝜂𝜂𝑒𝑒𝑒𝑒𝑒𝑒∗ 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 (2)
where 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 is the current energy delivered to shipping by Singapore's HFO bunkering activities, which translates into 𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡 tons of oil. If the ICE changes and is for instance replaced by a FC coupled with an electric motor, then
𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝 = 𝜂𝜂𝑒𝑒𝑒𝑒∗ 𝜂𝜂𝑓𝑓𝑐𝑐∗ 𝐶𝐶𝐻𝐻2 (3)
where 𝐶𝐶𝐻𝐻2 is the energy from H2 fuel. This H2 may be produced via electrolysis by renewable electricity or electricity from the grid, or via conventional SMR. Taking the electrolysis pathway:
𝐶𝐶𝐻𝐻2 = 𝜂𝜂𝑒𝑒−𝑒𝑒𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙∗ 𝐶𝐶𝑒𝑒𝑒𝑒 (4)
Therefore, for a given total propeller power, we can estimate how much electricity, renewable or not, Singapore has to provide (𝐶𝐶𝑒𝑒𝑒𝑒) if this electricity has to produce H2 to power the ship.
Similarly, for H2 production via SMR and other alternative fuels such as NH3, MeOH, biodiesel and LNG.
We can also then estimate the carbon emissions by evaluating the carbon content of the electricity or other fuel used to replace the oil.
For instance, if the electricity comes from the grid 𝐶𝐶𝐶𝐶 𝑡𝑡𝑡𝑡𝑡𝑡 = 𝐺𝐺𝐶𝐶𝐹𝐹 ∗ 𝐶𝐶𝑒𝑒𝑒𝑒(5)
where 𝐺𝐺𝐶𝐶𝐹𝐹 is the grid emission factor of the Singaporean grid.
2.6 Example calculation: H
2In this Section, we present an example calculation based on the above to demonstrate the technique used.
Taking H2 as marine fuel example, it can be produced from water electrolysis or SMR and used directly or in a fuel mixture. Both production processes including a brief nod to the cracking of the ammonia are analyzed, while only direct use in a fuel cell is evaluated since fuel mixture usage does not comply with our decarbonization scopes.
If 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 is the total energy available from the bunker fuel in a year,
𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡[𝑀𝑀𝑀𝑀/𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦] = 𝐿𝐿𝐿𝐿𝐿𝐿6∗ 𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡= 42,700.0 [𝑀𝑀𝑀𝑀/𝑡𝑡𝑡𝑡𝑡𝑡] ∗ 37,336,188.0 [𝑡𝑡𝑡𝑡𝑡𝑡] = 1,594,255,277,600.0
(1)
where 𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡 are the tons of HFO delivered yearly by Singapore’s bunkering activities. If 𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝 is the total energy at the propeller,
𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝[𝑀𝑀𝑀𝑀/𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦] = 𝜂𝜂𝑒𝑒𝑒𝑒𝑒𝑒∗ 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡=0.42 ∗ 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡= 668,938,200,000.0 (2)
where 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡 is the current energy delivered to shipping by Singapore's HFO bunkering activities, which translates into 𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡 tons of oil. If HFO has to be substituted by H2, the engine has to be replaced by fuel cells coupled with an electric motor. Hence,
𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝[𝑀𝑀𝑀𝑀/𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦] = 𝜂𝜂𝑒𝑒𝑒𝑒∗ 𝜂𝜂𝑓𝑓𝑐𝑐∗ 𝐶𝐶𝐻𝐻2= 0.925 ∗ 0.5 ∗ 𝐶𝐶𝐻𝐻2 (3)
obtaining 𝐶𝐶𝐻𝐻2= 1,447,756,098 𝐺𝐺𝑀𝑀/𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 for the energy from H2 fuel. This H2 may be produced via electrolysis by renewable electricity or electricity from the grid, or via conventional SMR and the various components along the way have certain efficiencies.
● Electrolysis
Figure 11: Schematic of H2 electrolysis energy flow
Taking the electrolysis pathway, the electrolyzer efficiency has been considered, 𝐶𝐶𝐻𝐻2[𝑀𝑀𝑀𝑀/𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦] = 𝜂𝜂𝑒𝑒−𝑒𝑒𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙∗ 𝐶𝐶𝑒𝑒𝑒𝑒 = 0.7 ∗ 𝐶𝐶𝑒𝑒𝑒𝑒 (4)
Therefore, for a given total propeller power, we can estimate how much electricity, renewable or not, Singapore has to provide if this electricity has to produce H2 to power the ship. Substituting numerical values, the total electricity needed is 𝐶𝐶𝑒𝑒𝑒𝑒 = 574,506 𝐺𝐺𝐺𝐺ℎ.
The energy needed is higher if H2 cracked from NH3 is to produce due to lower electrolysis efficiencies (𝜂𝜂𝑒𝑒−𝑒𝑒𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙 = 40 − 50% against 70% ), causing a decrease of the overall efficiency of the process (fuel cell + electrolysis) to 25% (against 35%) (S. Giddey, 2017).
While tank- to- propeller (TTP) emissions associated with H2 as a fuel are considered zero, we can estimate those associated with the carbon content of the electricity used. If the electricity comes from the grid:
𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡[𝑡𝑡𝑡𝑡𝑡𝑡𝐶𝐶𝑡𝑡2] = 𝐺𝐺𝐶𝐶𝐹𝐹 ∗ 𝐶𝐶𝑦𝑦𝐸𝐸 = 0.4188[𝑘𝑘𝑘𝑘𝐶𝐶𝑡𝑡2/𝑘𝑘𝐺𝐺ℎ] ∗ 𝐶𝐶𝑒𝑒𝑒𝑒 =240,579,215 (5)
where 𝐺𝐺𝐶𝐶𝐹𝐹 is the grid emission factor of Singapore’s grid; if produced from renewable sources we consider them to be null.
If electricity were to be produced by renewable sources and solar PV in particular, the capacity to install would be
𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡[𝐺𝐺𝐺𝐺] = 𝐶𝐶𝑒𝑒𝑒𝑒/𝑈𝑈𝐹𝐹 = 𝐶𝐶𝑒𝑒𝑒𝑒/1200 [ℎ] = 479 (6)
where 𝑈𝑈𝐹𝐹 is the utilisation factor predicted for 2020, based on the new developing projects (see calculation sheets in 7. Appendix). In terms of number of installations this is equivalent to
#𝑖𝑖𝑡𝑡𝑖𝑖𝑡𝑡𝑦𝑦𝐸𝐸𝐸𝐸 = 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡/𝐶𝐶𝑙𝑙𝑒𝑒𝑙𝑙𝑡𝑡 = 𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡/85.6 [𝑘𝑘𝐺𝐺/𝑖𝑖𝑡𝑡𝑖𝑖𝑡𝑡𝑦𝑦𝐸𝐸𝐸𝐸] =5,797,476 (7)
with 𝐶𝐶𝑙𝑙𝑒𝑒𝑙𝑙𝑡𝑡 is the average capacity of current solar installations in place in Singapore (see Figure 31: Singapore Solar PV calculation sheet (EMA, 2019)).
Using the carbon footprint of the PV driven electrolysis, total emissions associated to H2
production are
𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡[𝑡𝑡𝑡𝑡𝑡𝑡𝐶𝐶𝑡𝑡2] = 1.03[𝑘𝑘𝑘𝑘𝐶𝐶𝑡𝑡2/𝑘𝑘𝑘𝑘𝐿𝐿2] ∗ 𝑚𝑚𝐻𝐻2= 12,426,573 (7)
With 𝑚𝑚𝐻𝐻2= 𝐶𝐶𝐻𝐻2/ 𝐿𝐿𝐿𝐿𝐿𝐿 (𝑀𝑀𝑀𝑀/𝑘𝑘𝑘𝑘𝐻𝐻2) =12,064,634 𝑡𝑡𝑡𝑡𝑡𝑡 (8)
● Steam Methane Reforming
Figure 12: Schematic of SMR energy flow
If a conventional SMR process was to be performed instead, the total amount of NG needed would be
𝑚𝑚𝑁𝑁𝑁𝑁[𝑡𝑡𝑡𝑡𝑡𝑡] = 𝐶𝐶H2/𝜂𝜂𝑆𝑆𝑆𝑆𝑆𝑆/𝐿𝐿𝐿𝐿𝐿𝐿𝑁𝑁𝑁𝑁= 𝐶𝐶𝐻𝐻2/0.7/13.1[𝑀𝑀𝐺𝐺ℎ/𝑡𝑡𝑡𝑡𝑡𝑡] = 43,911,316 (9) where 𝜂𝜂𝑆𝑆𝑆𝑆𝑆𝑆 is the efficiency of the reforming process.
We can also then estimate the well-to-tank (WTT) emissions by evaluating the median CO2
emission for SMR H2 production,
𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡[𝑡𝑡𝑡𝑡𝑡𝑡𝐶𝐶𝑡𝑡2] = 𝐶𝐶𝐶𝐶𝑆𝑆𝑆𝑆𝑆𝑆∗ 𝑚𝑚𝐻𝐻2= 10.8[𝑘𝑘𝑘𝑘𝐶𝐶𝑡𝑡2/𝑘𝑘𝑘𝑘𝐿𝐿2] ∗ ₂₂₂𝑚𝑚𝐻𝐻2=130,298,049 (10)
3. Results
Similarly to H2, the same equations have been applied to the other alternative fuels in analysis.
Calculations with flow charts depicting the processes considered are available in the next chapters, where results obtained are presented and discussed in the context of Singapore and its energy mix.
3.1 Hydrogen
Figure 13: Schematic of H2 production calculations with used efficiencies included.
The electricity required to produce, via electrolysis, the amount of H2 needed to replace the initial tons of HFO is 𝐶𝐶𝑒𝑒𝑒𝑒= 574,506 𝐺𝐺𝐺𝐺ℎ (4). According to the EMA Government statistics, Singapore's total electricity consumption in 2018 was 50,400 𝐺𝐺𝐺𝐺ℎ, thus 𝐶𝐶𝑒𝑒𝑒𝑒 is 11 times the total electricity consumption of Singapore within the same year. Such electricity could either come from the grid (more than 95% produced from NG) or from solar PV (Energy Market Authority (EMA), 2019). If electricity was to be produced by solar PV, the capacity to install would be 𝐶𝐶𝑦𝑦𝐶𝐶𝑦𝑦𝐶𝐶𝑖𝑖𝑡𝑡𝑦𝑦𝑡𝑡𝑡𝑡𝑡𝑡= 479 𝐺𝐺𝐺𝐺 (6), which, if compared to Singapore's ambitious 2030 solar energy target of 2 GWp capacity, is more than 200 times this target (Energy Market Authority (EMA), 2019).
If a conventional SMR process was to be performed instead, the total amount of NG needed would be 𝑚𝑚𝑁𝑁𝑁𝑁 = 43,911,316 𝑡𝑡𝑡𝑡𝑡𝑡 (9). Taking Singapore's total NG supply of 2018 statistics as a reference (8,883,602 𝑡𝑡𝑡𝑡𝑡𝑡), the amount of NG to supply theoretically is 5 times the supply of the same year (Energy Market Authority (EMA), 2020). Additionally, the incorporation of CCS would require even a higher consumption of NG, but this calculation is not performed.
Furthermore, total CO2 emissions from the grid electricity (𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡) account for 240,579,215 𝑡𝑡𝑡𝑡𝑡𝑡 (5), versus 130,298,049 𝑡𝑡𝑡𝑡𝑡𝑡 for SMR (10). This result is reasonable taking into account, again, that more than 95% of electricity in Singapore is produced by NG, as a proof that electricity (and
all its final use), unless produced from clean energy can be more polluting than traditional fuel combustion. Particularly interesting is the fact that the grid emissions even exceed those of initial tons of HFO (𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡) which amount to 137,743,651 𝑡𝑡𝑡𝑡𝑡𝑡. The most substantial difference lies in the nature of these emissions, meaning when these emissions are actually issued (production or on board): HFO total CO2 emissions are mostly TTP, while H2’s (both from CH4 and water electrolysis) are only WTT.
3.2 Ammonia
Figure 14: Schematic of NH3 production calculations with used efficiencies included
Assuming an engine and cracking overall efficiency 𝜂𝜂𝑒𝑒𝑒𝑒𝑒𝑒∗𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 = 0.494, the electricity required to produce, via electrolysis, the amount of NH3 needed to replace the initial tons of HFO (𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡) is 𝐶𝐶𝑒𝑒𝑒𝑒 = 1,394,485 𝐺𝐺𝐺𝐺ℎ, while showing a lower value if produced via conventional Haber-Bosch from NG (𝐶𝐶𝑁𝑁𝑁𝑁 = 570,471 GWh), which corresponds to an amount of NG equal to 𝑚𝑚𝑁𝑁𝑁𝑁 =
43,602,897 𝑡𝑡𝑡𝑡𝑡𝑡. This is due to the greater efficiency of the latter production process as it is well known and widely used ( 𝜂𝜂𝑒𝑒−𝑒𝑒𝑙𝑙𝑙𝑙𝑙𝑙𝑙𝑙 = 0.54 𝑣𝑣𝑦𝑦𝑦𝑦𝑖𝑖𝑣𝑣𝑖𝑖 𝜂𝜂𝐻𝐻𝐻𝐻𝑡𝑡𝑙𝑙𝑐𝑐ℎ= 0.66) (The Royal Society, 2020).
Analyzing the obtained numbers, the electricity required to produce the amount of NH3 needed to replace the initial tons of HFO (𝑋𝑋𝑡𝑡𝑡𝑡𝑡𝑡) at the propulsor (𝐶𝐶𝑒𝑒𝑒𝑒) is almost 30 times the total electricity consumption of Singapore in 2019 (Energy Market Authority (EMA), 2019). And even if, absurdly enough, Singapore could meet that demand, it would not be in a sustainable way given the scarcity of renewable resources and its dependence on imports.
Concerning the Haber-Brosch process, taking Singapore’s total NG supply of 2018 statistics as a reference (8,883,602.97 tons), the amount of NG (𝑚𝑚𝑁𝑁𝑁𝑁) to supply theoretically is 5 times the supply of the same year (Energy Market Authority (EMA), 2020).
Furthermore, total CO2 emissions from the conventional fossil based Haber-Bosch (𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡) account for 133,357,774 tons, 10 times those emitted by the renewable electricity equivalent process.
3.3 MeOH
Figure 15: Schematic of MeOH production calculations, with used efficiencies included.
As seen for H2 and ammonia, MeOH production via SMR is well-known, showing the highest efficiency (75%) compared to the three different processes in analysis (Michael Matzen, 2015).
Assuming MeOH to replace Singapore’s HFO bunker fuel is produced via conventional SMR, a mass of NG 𝑚𝑚𝑁𝑁𝑁𝑁 = 45,131,075 𝑡𝑡𝑡𝑡𝑡𝑡 would be needed. Again, taking Singapore’s total NG supply in 2018 statistics as a reference (8,883,602.97 tons), the amount of NG (𝑚𝑚𝑁𝑁𝑁𝑁) to supply
theoretically is 5 times the supply of the same year!
For the production of e-MeOH, the process undergoes an efficiency reduction of about 40%
compared to conventional pathways (Michael Matzen, 2015), thus higher energy consumption (𝐶𝐶𝑒𝑒𝑒𝑒= 962,715 𝐺𝐺𝐺𝐺ℎ) , which corresponds to almost 20 times the total electricity consumption of Singapore in 2018.
More reasonable results are obtained instead from the production of bio-MeOH, which is among the other two options both in terms of efficiency range (55%) (Michael Matzen, 2015) and energy consumption 𝐶𝐶𝑏𝑏𝑙𝑙𝑡𝑡−𝑆𝑆𝑒𝑒𝑀𝑀𝐻𝐻=805,179 𝐺𝐺𝐺𝐺ℎ . Assuming woody biomass as feedstock (𝐿𝐿𝐿𝐿𝐿𝐿 = 20 𝑀𝑀𝑀𝑀/𝑘𝑘𝑘𝑘), the biomass to supply is 𝑚𝑚𝑤𝑤𝑡𝑡𝑡𝑡𝑤𝑤 =144,932,293 𝑡𝑡𝑡𝑡𝑡𝑡. Taking as a reference the annual woody biomass production in natural forests projected for 2020 (359,300,000.00 tons), the woody biomass feedstock mass obtained is around 40% the resource available locally (Nophea Sasaki, 2009).
The environmental assessment of MeOH used as ship fuel shows that, for a life-cycle
perspective, MeOH produced with NG has higher emissions than conventional fuels, with most emissions due to the combustion, or TTP (𝐶𝐶𝐶𝐶𝑖𝑖𝑡𝑡𝑡𝑡𝑡𝑡= 142,685,842.87 𝑡𝑡𝑡𝑡𝑡𝑡 𝐶𝐶𝑡𝑡2). However, at much higher energy consumption charges (+60%), a 90% reduction in total emissions compared to conventional SMR can be achieved through the production of e-methane if produced from clean electricity(𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡= 14,268,584.29 𝑡𝑡𝑡𝑡𝑡𝑡 𝐶𝐶𝑡𝑡2), where emissions are mainly attributable to electricity
production itself. (Joanne Ellis, 2018). The environmental benefits of MeOH are indeed highly dependent on the feedstock used to make it: if made with an electricity mix that does not have a high share of renewables, even e-MeOH (or bio-MeOH) is not necessarily much improved over HFO. Instead, using relatively clean electricity, good potential for emissions reduction in MeOH production is achievable through the production from biomass (𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡= 27,102,338.87 𝑡𝑡𝑡𝑡𝑡𝑡 𝐶𝐶𝑡𝑡2).
WTT emissions are in this case related to biomass growing, harvesting and transportation while conventionally TTP emissions from biofuels, including bio-MeOH, are considered zero because biogenic (see section 2.4 Assumptions).
3.4 Biodiesel
Figure 16: Schematic of biodiesel production calculations, with used efficiencies included.
If HFO must be substituted by biodiesel, the same low speed two-stroke diesel engine can still be used. Taking the same engine efficiency (𝜂𝜂𝑒𝑒𝑒𝑒𝑒𝑒= 42%), 𝐶𝐶𝑏𝑏𝑙𝑙𝑡𝑡𝑤𝑤𝑙𝑙𝑒𝑒𝑙𝑙𝑒𝑒𝑒𝑒 = 1,594,255 𝑇𝑇𝑀𝑀 is obtained for the energy needed from biodiesel fuel. Assuming biodiesel is FAME (𝐿𝐿𝐿𝐿𝐿𝐿 = 38 𝑀𝑀𝑀𝑀/𝑘𝑘𝑘𝑘) and biomass-to-fuel conversion is 0.35 (Jonathan Goffé, 2019), 41,954,084.94 of FAME biodiesel, thus 119,868,814.11 tons of feedstock are to be supplied. Just to have an order of magnitude, the biodiesel needed to replace HFO bunker in Singapore is 9 times the yearly production that Neste Group, the world’s largest and most advanced refinery for high-quality renewable diesel in Singapore, expects by 2022 (Neste Group, 2016).
Furthermore, total emissions are either about the same as or higher than regular diesel,
depending on the feedstock used. Taking the data for palm oil biodiesel (with methane capture at oil mill) WTT emissions provided by the European Energy Directive of 2018 (46.3 𝑘𝑘𝐶𝐶𝑡𝑡2, 𝑦𝑦𝑒𝑒/
𝑀𝑀𝑀𝑀), the CO2,eq emissions to replace HFO with FAME biodiesel are 𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡=
73,814,017 𝑡𝑡𝑡𝑡𝑡𝑡 𝐶𝐶𝑡𝑡2, 𝑦𝑦𝑒𝑒. If an open effluent pond would be used instead, total emissions would rise to 𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡= 101,235,206 𝑡𝑡𝑡𝑡𝑡𝑡 𝐶𝐶𝑡𝑡2, 𝑦𝑦𝑒𝑒. (General Secretariat of the Council, 2018). Even though combustion of biological materials adds CO₂ to the atmosphere similar to combustion of fossil fuels, biofuels are regarded as CO2-neutral, given that the CO₂ captured from the atmosphere by the feedstock plants as they grow. Thus, TTP emissions are considered nil.
3.5 LNG
Figure 17: Schematic of LNG production calculations, with used efficiencies included.
In order to replace HFO with LNG, a diesel-ignited gas engine with dual fuel capability with
𝜂𝜂𝑒𝑒𝑒𝑒𝑒𝑒= 0.47 is considered. The amount of LNG required to substitute the initial tons of HFO with
LNG is 𝑚𝑚𝑁𝑁𝑁𝑁 = 30,247,423 𝑡𝑡𝑡𝑡𝑡𝑡𝑖𝑖 which corresponds to 𝐶𝐶𝑁𝑁𝑁𝑁 = 1,424,653 𝑇𝑇𝑀𝑀 of energy to supply.
According to the Port Information for Singapore LNG Terminal, in 2018 the capacity of the terminal was 11 𝑀𝑀𝑡𝑡𝐶𝐶𝑦𝑦of LNG, with possible further extension up to 15 𝑀𝑀𝑡𝑡𝐶𝐶𝑦𝑦.Therefore, it would require twice the capacity potentially installable in the terminal to provide the required amount of LNG (Singapore LNG Corporation, 2020).
LNG combustion emits less amount of pollutants in comparison with those emitted by
conventional fuels. The main environmental concern of LNG is due to methane slip which, for the high-pressure injection engine in analysis, have been neglected. Total emission (𝐶𝐶𝐶𝐶𝑡𝑡𝑡𝑡𝑡𝑡) account for 95,279,381.40 tons, 80% of which TTP.
3.6 Sensitivity analysis
The key quantity of the calculation to assess feasibility of alternative fuels’ adoption is the fuel cell. Today, only H2 PEM fuel cells are commercially viable and suitable in marine applications, with 40-60% energy efficiency (US. Department of Energy, 2011) and 83% maximum theoretical energy efficiency based on the World Energy Council (World Energy Council, 2014). But direct alcohol fuel cells (DAFCs) running on ammonia or MeOH, for example, have great potential as alternative power source because of a much higher energy density than H2 (M.Fadzillah, 2019).
NH3 and MeOH linked to FC might potentially offer higher thermal efficiency and lower emissions of air pollutants, but no driven propulsion technologies for marine operation have been commercialized yet (Hansson, 2020). It would be interesting, thus recommended in section 5.2.
Recommendations for Future Work, to carry out a sensitivity analysis on the use of ammonia and MeOH in DAFCs instead of ICEs. However, for lack of data is not part of this research.
Taking H2 calculation as an example (section 2.6 Example calculation: ), the first sensitivity performed provides the resources needed (grid electricity or NG) for H2 production against amelioration of FC efficiency. The mass of H2 to produce (𝑚𝑚𝐻𝐻2) is sensitive to the FC efficiency improvement. Assuming the energy required for propulsion (𝐶𝐶𝑝𝑝𝑐𝑐𝑡𝑡𝑝𝑝) remains constant (improving efficiencies in conventional ICEs are neglected), the decrease in resources needed is shown in Figure 18, where the fuel cell maximum theoretical efficiency (83%) is used as the threshold value. For simplicity, it is also assumed that electrolyzers continue to use Alkaline Electrolysis
Cell (AEC) technology, a very mature technique whose efficiency will likely remain stable (O.Schmidt, 2017).
Figure 18: Sensitivity Analysis of H2 resources consumption
The second sensitivity analysis provides the CO2 emissions against improvements in FC effciency. The descending emission trend of Figure 19 is a direct consequence of the first sensitivity: as the development of FC progresses, for the same energy at the propulsion the input resources decrese and with them the corrisponding CO2 emissions.
Figure 19: Sensitivity Analysis of H2 CO2 emissions 0
100 000 200 000 300 000 400 000 500 000 600 000
0,5 0,6 0,7 0,8 0,83
Resources consumption against improvements in FC efficiency
electricity (GWh) NG (kton)
0 50 100 150 200 250 300
0,5 0,6 0,7 0,8 0,83
CO2 emissions against improvements in FC efficiency (Mtpa)
CO2,el (Mtpa) CO2, NG (Mtpa)
To now contextualize this analysis to the situation in Singapore, it is arbitrarily (and
optimistically) assumed 78% efficiency of FCs for 2050 (Figure 20: Schematic of H2 production calculations in 2050. Following the procedure of section 2.6 Example calculation: , the mass of H2 to be delivered amounts to 𝑚𝑚𝐻𝐻2 = 7,733,740 𝑡𝑡𝑡𝑡𝑡𝑡 (8) which is equivalent to 𝐶𝐶𝑒𝑒𝑒𝑒 =
368,273 𝐺𝐺𝐺𝐺ℎ ( 4) of electricity if produced via electrolysis or 𝑚𝑚𝑁𝑁𝑁𝑁 = 28,148,280 𝑡𝑡𝑡𝑡𝑡𝑡 (9) of NG if produced via SMR (efficiency improvement of SMR neglected).
Figure 20: Schematic of H2 production calculations in 2050
Following the BAU scenario of the NUS Energy Studies Institute, the value of electricity (𝐶𝐶𝑒𝑒𝑒𝑒) obtained corresponds to 4 times the forecasted total electricity demand of Singapore in 2050 (Nian, 2015), compared to the 11 times of the current scenario to date (section 3.1).
The potential for gas demand growth in Asia Pacific for the upcoming 30 years is enormous (+2.1% per annum), 1,633 𝑏𝑏𝐶𝐶𝑚𝑚 (1,435 𝑀𝑀𝑡𝑡𝑡𝑡𝑡𝑡)are expected to be consumed by 2050 according to the GECF Global Gas Outlook 2050 and the amount of NG required(𝑚𝑚𝑁𝑁𝑁𝑁) corresponds to about 2% of the total forecasted gas consumption of the area, against the present 5%.
3.7 Summary of results
Within the scope of this study, two parallel aspects show up when discussing alternative fuels compared to conventional fossils: the environmental benefits of the fuel, quantifiable in terms of CO2 emissions reduction, and the energy consumption related to the fuel’s production. The latter can also be an indicator of procurement of resources, thus used to compare the resources locally available versus those needed to produce the fuel.
The main findings of this research reveal that today none of the alternative fuels considered possesses overall performances comparable with those of conventional fuels. This statement applies even more in the context of Singapore, where primary resources are scarce and land extension is extremely constrained as shown in Figure 21, where energy availability in Singapore, in terms of electricity and feedstocks, and needed are put in comparison.
Figure 21: Energy needed vs. Energy available in Singapore
By way of example, the first column to the right (Figure 21) shows that 11 times the sources available in Singapore today, whereby in this case resources means electricity, are needed to produce enough e-H2.
As far as the availability and procurement of resources are concerned, under this model only bio-MeOH could be covered by the resources available on site (Figure 22).
0 5 10 15 20 25 30
times
Energy needed vs. Energy available in Singapore (2018)
Electricity Needed Feedstock Needed Singapore Sources Available
