Sustainable Energy Systems on Ships: Novel Technologies for Low Carbon Shipping

By Francesco Baldi

Sustainable Energy Systems on Ships is a comprehensive technical reference for all aspects of energy efficient shipping. The book discusses the technology options to make shipping energy consumption greener, focusing on the smarter integration of energy streams, the introduction of renewable resources and the improvement of control and operability. Chapters not only describe each technology individually, but also analyze their interconnections when implemented onboard, and compare them in terms of suitability for different vessels and economic viability.

Readers of Sustainable Energy Systems on Ships will find an invaluable reference suitable for researchers, professionals, and managers involved in the shipping industry and those working on related energy efficiency technologies, fuel cells, and in the transport industry generally. Students of maritime engineering will also be well served by this reference.

• Clear analysis of the current implementation status of each technology discussed, the barriers for further development, and the potential for large-scale implementation
• Enables decision-making on the most suitable technologies for each type of vessel
• Integrates energy efficiency and emission control rules, regulations, technologies (including data science), and challenges in relation to the shipping industry
• Includes industry case studies on the integration of novel energy conversion technologies and renewable energy sources in operating ships

• Language: English
• Publisher: Elsevier Science
• Release date: Jul 21, 2022
• ISBN: 9780323859905

Book preview

Part 1: Setting the scene

Outline

Chapter 1. The shipping industry and the climate

Chapter 2. Energy systems on board ships

Chapter 1: The shipping industry and the climate

Karin Andersson    Maritime Environmental Science, Department of Mechanics and Maritime Science, Chalmers University of Technology, Gothenburg, Sweden

Abstract

As by 2020, the past six years, including 2020, are likely to be the six warmest years on record and the global mean temperature was 1.2 °C above the preindustrial level [1]. International agreements, the Kyoto Protocol (1997) and the Paris agreement (2016), has set the aim to keep a global temperature rise during this century well below 2 °C above pre-industrial levels.

The anthropogenic inflow of GHGs to the atmosphere from the shipping industry was estimated by the IMO to totally around 2.5–3% of the global emissions in 2018 (or 1076 million tonnes). This is an increase by 9.6% since the previous study in 2014. The IMO projects the future emissions to increase from 1000 Mt CO2 in 2018 to 1000 to 1500 Mt CO2 in 2050 in a Business as Usual, BAU, scenario.

Two years after the Paris agreement, the IMO adopted a vision, followed by a plan for implementation, in which a global goal of 50% reduction in GHG emissions from shipping by 2050 compared to 2008, and a total phase-out within this century is stated. Action from the IMO has started with a data collection system for fuel oil consumption. Ships of >5000 gross tonnage are required to collect consumption data fuel oil use and data on transport work. The European Union has started work on emission decrease with demands on Monitoring, Reporting and Verification of CO2 emissions from large ships (>5000 tonnes) using EU ports. Also here further measures are expected.

At present here are many different initiatives, internationally, from countries as well as from shipping companies and shipowners to find ways towards zero carbon shipping. The different regulations and incentives introduced will help on the way, but still there is a need for more strict regulations or stronger incentives. The present initiatives give a large potential to make shipping and sea transport an important player also in a carbon neutral, sustainable society.

Keywords

Climate change; Shipping's contribution; Environmental impacts; Regulations; Visions; Strategies; Zero-carbon shipping

1.1 Introduction

The purpose of this chapter is to provide an overview of the current environmental impact of shipping, with a specific focus on its effect on the climate and on what are the current trends in dealing with this challenge.

Section 1.2 provides a general overview of climate change and on how it is influenced by human activities, setting the overall scientific background at the foundation of this book. The discussion naturally evolves into the analysis of the contribution of shipping to climate change (Section 1.3) and, more generally, of its impact on the environment (Section 1.4).

The remaining part of the chapter discusses about potential countermeasures to the current situation: current and possible future environmental regulations are presented in Section 1.5, while Section 1.6 focuses on the discussion of visions and strategies for a future shipping at low climatic impact. Section 1.7 concludes the chapter, with a discussion of different visions for how to make shipping completely carbon-neutral

1.2 Climate change. Influence from human activities

As by 2020, the past six years, including 2020, are likely to be the six warmest years on record and the global mean temperature was 1.2 °C above the preindustrial level [1]. The global average temperature is increasing as well as the total amount of carbon dioxide, CO2 in the atmosphere. Other major greenhouse gases (GHG) like methane, CH4, and nitrous oxide, N2O, also continued to increase in 2019 and 2020. Among many measurable effects of climate change, also the Greenland ice sheet continued to lose mass.

Global warming, or climate change, is attributed to an increase of heat absorbing gases in the atmosphere due to anthropogenic (human) activities. The main contributor among the gases is carbon dioxide, CO2, due to the large amounts released when using fossil fuels like petroleum, natural gas or coal. However, CO2 is not a pollutant to the environment, on the contrary, it is part of the natural carbon cycle that constitutes a prerequisite for life on earth. But addition of fossil carbon (earlier immobilized in the ground) since industrialization began, has resulted in the considerable increase in CO2 in the atmosphere. CO2 will also be dissolved in the oceans forming carbonic acid, causing ocean acidification and impact on coral reefs and other sensitive marine species

The heat absorption by gases like CO2 in the atmosphere is necessary to prevent the temperature on earth to sink to very low values during night. As long as the level is constant, the annual average temperature will be kept constant globally. The carbon cycle and the importance of the content of CO2 in the atmosphere to the global temperature was first calculated and discussed in detail by Arrhenius in 1896 [2]. Arrhenius made calculations on the heat balance of earth and on the heat absorption of CO2 and made an estimate of the effect on temperature by variation in CO2 content in the atmosphere, thereby predicting climate change as a result of increased CO2.

In addition to CO2, there are several other heat absorbing gases in the atmosphere, some of which have a much higher absorbing capacity per molecule than CO2. Most of these are also occurring naturally, although human activities have increased also the amounts present. One important among those is methane, CH4, which is the main constituent in natural gas that is used as fuel, compressed as CNG or in liquified form as LNG. Methane is also formed in biological decomposition processes where human activities can indirectly cause increases also in these sources, e.g. by draining of wetlands or intense breeding of cattle. Methane has a warming potential (absorption per molecule) of 30 times or more of that of CO2. Other important greenhouse gases are nitrous oxide, N2O, that is produced by biological activity in soil but also is formed in combustion processes along with other nitrogen oxides like NO and NO2. Water vapor is also an important gas for the climate and human activities may contribute to increased amounts in the atmosphere.

The modern trend of increasing CO2 levels in the atmosphere was observed first at the Mauna Loa observatory on Hawaii, where daily measurements of CO2 started in 1958, see Fig. 1.1. The diagram is sometimes referred to as the Keeling curve. Additional studies of CO2 concentrations, for example in air trapped in glaciers, showed that the increase was a trend since the beginning of industrialization. The preindustrial atmospheric CO2 level of below 280 ppm has today (2021) reached 416 ppm, see Figs. 1.1 and 1.2.

Figure 1.1 Carbon dioxide in air, left, measured at the Mauna Loa observatory since 1958, the Keeling Curve. Right, CO 2 data from 1700 to present, data before 1958 from ice cores [4].

Figure 1.2 Carbon dioxide, CO 2 , in the atmosphere, historically during the last 800 000 years, based on ice core data until 1958 [4].

The international community in the United Nations concluded that there was a need to stop the increase, leading to an agreement, the Kyoto Protocol, which was adopted in 1997. This is an international agreement with binding targets for 37 industrialized countries and the European community for reducing greenhouse gas (GHG) emissions. Continued negotiations have led to the Paris agreement, entering into force in 2016, with the aim to strengthen the global response to the threat of climate change by keeping a global temperature rise during this century well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 °C [3].

As the concentration of CO2 in the atmosphere rises, so too does the concentration of CO2 in the oceans. This affects ocean chemistry, lowering the average pH of the water, a process known as ocean acidification. All these changes have broad range of impacts in the oceans and coastal areas [1]. The ocean absorbs around 23% of the annual emissions of anthropogenic CO2 to the atmosphere, thereby helping to alleviate the impacts of climate change on the planet. This affects the ecology of the ocean, since the CO2 reacts with seawater, lowering its pH, a process known as ocean acidification. Ocean acidification affects many organisms and ecosystem services, and it is threatening food security by endangering fisheries and aquaculture. This is particularly a problem in the polar oceans because of the ocean chemistry of these cold regions. It also affects coastal protection by weakening coral reefs, which shield coastlines.

Some expectations on positive effects on global trade by making new arctic fairways available are also discussed, but this is unlikely to compensate for the many negative impacts.

Global warming is a challenge for all sectors of industry, all nations and all people on earth. We will all be affected by the impacts that are global and shared, and we all share the challenge to reduce our emissions of greenhouse gases (GHG) drastically in the coming years.

1.3 The contribution of shipping to climate change

Today, the international shipping is carrying close to 2 000 000 tonnes of cargo annually [5] and there has for many years been an expected growth of international trade and thus shipping, that adds to the challenge of decreasing emissions of GHG but also of other pollutants. However, the shipping sector is very diverse, being an important part of international trade, but also contributing to regional and local transports and activities. This includes cargos and public transport but also fishing vessels, offshore construction and maintenance, and many other things, some examples are illustrated in Fig. 1.3. Although shipping follows main routes over the globe and thus the emissions of GHG are unevenly distributed, as is seen in Fig. 1.4, the impact on global warming is the same, independent of where the emission occurs, since the gases have a long residence time and will be mixed into the atmosphere. Thus, in order to assess the total contribution to climate change from the shipping sector, estimates of the fossil fuel consumption of the whole global fleet are needed. The task to make a global estimate has been taken on by the IMO. Until now, the IMO has published four reports on GHG emissions from global shipping, in 2000, 2009, 2014, and the latest in 2020 [6].

Figure 1.3 Shipping is very diverse with different challenges and opportunities for decreasing GHG emissions. Some examples, from upper left: cruise ship, RoPax ferry, traditional passenger steam ship, passenger ferry in public transport, fishing vessel, road ferry, taxi boat, tank cargo ship, container ship at berth, cargo ship. Photo Karin Andersson.

Figure 1.4 Global distribution of shipping GHG emissions 2015 [11].

In the 4th GHG report, estimates of past (2012–2018) and future (2018–2050) emissions based on bottom-up as well as top-down calculations are performed. The bottom-up method is based on individual vessels' operational activity, using estimates of emissions from AIS-transmitted data. These data are then used to calculate the fuel consumption and emissions on an hourly, per-vessel basis for each year in the inventory. Individual ships are identified as in service using the IHS database. Emissions are allocated to either international or domestic shipping activity, consistent with the IPCC guidelines and definitions. The top-down approach uses World Energy Statistics provided by IEA to estimate global shipping emissions for the period 2012–2017 applying emissions factors based on the total mass of absorbing compounds divided by the total mass of fuel consumption, estimated using the bottom-up approach. The heat absorbing compounds are found among gases as well as particulate matter, and in the study a number of compounds emitted from shipping are included. Both potent GHGs and other compounds causing other environmental impact were taken into account: carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOCs), carbon monoxide (CO), particulate matter (PM) sulfur oxides (SOx), and black carbon (BC).

The IMO inventory includes global emissions from ships of 100 GT and above engaged in both domestic and international voyages. This means that the total emissions, when taking also the smaller ships sizes into account, are larger. The emissions from the smaller ships are, at least some extent, included in national emission data and are part of national commitments for GHG reduction.

Using these methods, the anthropogenic inflow of GHGs to the atmosphere from the shipping industry was estimated to totally around 2.5–3% of the global emissions in 2018 (or 1076 million tonnes) [6]. This is an increase by 9.6% since the third IMO GHG study in 2014 [7] and an increase in the share of global emissions from 2.76% in 2012 to 2.89% in 2018. In the study only emissions from operation of the ships were included. There are also emissions related to the fuel, both CO2 from energy use for fuel production and distribution but also losses of CH4 in LNG production and distribution [8]. The IMO results can be compared to the data obtained in the first report from the European Monitoring Reporting and Verification, MRV, where it is concluded that over 3% of the total European Union CO2 emissions or >138 million tonnes, came from shipping [9].

The emission trends follow the trend in total fuel consumption over the period 2012–2018. Some observations in the IMO study are:

–  Methane, CH4, was increased by 87% over the period. This was partly due to an increase in consumption of LNG, but the increase is dominated by a change in the machinery mix associated with the increased use of LNG as a fuel. This has led to a significant increase in the use of dual-fuel machinery, that has higher specific exhaust emissions of CH4.

Also for other pollutants, some observations were made:

–  SOX and PM emissions increased over the period in spite of an overall reduction in HFO use and a simultaneous increase in MDO and LNG use (associated with the limits on sulfur content of fuels). The explanation is that the average sulfur content increase in the HFO used over the period exceeds the sulfur content reduction associated with the change in fuel use. (the global sulfur cap of 0.5% is in force from 2020, so the requirement for low sulfur fuel only occurred in the SECA areas).

–  NOX emissions showed lower rates of increase over the period than the trend in fuel consumption. This is consistent with the increased number of ships fitted with, and where appropriate operating with, NOX Tier II and Tier III compliant machinery.

In the 4th IMO GHG study, scenarios, the future emissions of shipping are projected to increase from 1000 Mt CO2 in 2018 to 1000 to 1500 Mt CO2 in 2050 in a Business as Usual, BAU, scenario. This represents an increase of up to 50% over 2018 levels and is equal to 90–130% of 2008 levels. This is related to an increase in trade and the carbon intensity, g CO2 per ton km, has already improved between 2012 and 2018 for international shipping as a whole, as well as for most ship types. The overall carbon intensity, as an average across international shipping, was up to 29% better than in 2008, but the improvements have not decreased in a linear way, and more than half of the reduction has been achieved before 2012. Since 2015, the pace of improvement has slowed, with average annual percentage changes ranging from 1 to 2% [6]. In order to achieve large reduction in GHG emissions, there is thus a need for a significant decrease of emissions.

Recently (2020), the predictions of future trade and thus shipping have become more difficult due to the outbreak of the Covid-19 pandemics [6]. (See also BOX.) However, the conclusion in the IMO study is that, depending on the recovery from the pandemics, the emissions in the next decades may be a few percent lower than projected, but in all, the impact of Covid-19 is likely to be smaller than the uncertainty range of the presented scenarios in the IMO study [6]. A possibility is that, taking the age of the fleet in several sectors into account, the demands for rebuilding of the cargo fleet in the coming 20 years are real, and it provides an opportunity to use the new technologies developed as a result of the zero carbon and energy efficiency demands [10].

1.4 Other major environmental impacts from shipping

In order to make shipping contribute to fulfillment of as many as possible of the 17 United Nations Sustainable Development Goals, SDGs [12], and not only number 13, Climate Action, there are many parameters to take into account. Important among the other goals are number 14, Life Below Water, and 15, Life on Land, 3, Good Health and Well-being, and several other. In addition to the contribution to global warming, shipping contributes to several other impacts on health and natural environment due to emissions to air. Some important emissions are sulfur oxides, nitrogen oxides, particles and hydrocarbons, all related to the energy system.

Among emissions related to fuel combustion, sulfur and nitrogen oxides are already regulated in various ways and areas, globally, regionally and locally. The emissions of particles, soot and various hydrocarbons are generally not included in global or regional regulations, but are strongly related to fuel quality and sulfur content.

Many of the compounds and elements released to the atmosphere will finally end up in the oceans and lake waters. The water is also affected by releases directly to water from ships, as from the hull, but also by direct emissions, intentionally or by accidents of waste, oil or cargo.

If a systems perspective on the fuel used, including impact from Well-to propeller, also other impacts for example on ecosystems from growing and harvesting biofuel or social impacts arising in competition for energy that have to be taken into account. The decision on energy carrier and energy conversion for shipping will require a systems perspective, taking many different criteria into account [13].

1.5 Present state of environmental regulations

The pathway towards decrease of emissions from shipping requires commitments from all involved stakeholders. The origin of the energy carrier and an efficient use of energy are key factors to achieve this. However, the knowledge and acceptance of this will most certainly not be enough, since there are many barriers, economy being one, but not the only, there is also a need for regulations and incentives to make technology and management that supports zero GHG emissions the first choice. Also, this has to happen while also fulfilling other criteria for sustainability.

The Kyoto Protocol contains provisions for reducing GHG emissions from nations, but also from international aviation and shipping. However, aviation and shipping are treated in a different way due to their global activities. The responsibility for measures for global aviation lies at the International Civil Aviation Organization (ICAO) and for global shipping at the International Maritime Organization (IMO). Emissions from domestic aviation and shipping are included in national targets [14].

Two years after the Paris agreement, in April 2018, the IMO adopted a vision document, later followed by a plan for implementation [15], in which a global goal of 50% reduction in GHG emissions from shipping by 2050 compared to 2008 and a total phase-out within this century is stated [14]. This was not the first action from the IMO regarding CO2 emissions, the Energy Efficiency Design Index, EEDI, and the Ship Energy Management Plan, SEEMP, were already in place, as discussed later in this chapter, but the vision had a goal that needs much more reduction than can be achieved by the EEDI.

Some of the measures for an emission decrease are indeed cost efficient, like energy efficiency, which decreases fuel consumption, while others, like change to a cleaner energy carrier and new conversion technology will usually come at an increased cost. The fact that the fossil fuels, especially heavy fuel oil, HFO, have a very low winning and production cost, affects the economy of change. In short, it is difficult, if not impossible, to produce an alternative energy carrier at the same low cost as HFO. In addition, there are many other criteria beside economy and environmental impact that are of importance and that will influence the choice of energy carrier and energy system. Examples are readiness of technology, available infrastructure for fuel bunkering, health and safety on board, environmental impact of fuel spill to soil and water and many other. For the change from fossil to non-fossil fuel, it is also obvious that different criteria may apply to different sectors and regions as well as different stakeholders [13,16].

An important conclusion when examining the criteria for decisions on fuel change as well as for new conversion technology is that it is not enough to focus only on the emissions directly from the ship, although most strategies and regulations today only mention these. In order to find a sustainable solution, the whole fuel system, including winning of primary energy, processing and distribution of fuel is also of large importance, as is discussed further in Chapter 8.

1.5.1 Who regulates?

The economic dependence on shipping for trade between countries and regions has made regulations and agreements necessary. The regulatory framework for shipping has a very long history, and agreements or regulations start in early civilizations. Preserved documents from the Sumer, dating from around 1700 BC provide early examples of this [17]. The more formal start of maritime law is attributed to old Greece, where the seafarers at Rhodes made a maritime code, The Rhodian Law [18]. In making regulations, the demands for freedom of navigation on the oceans have to be balanced by the need for sovereignty protecting the coasts of nations.

The framework for shipping regulations today, taking this balance into account, is related to the definition of different maritime zones, as described in the 1982 United Nations convention of the Law of the SEA (UNCLOS) [19,20]. The most Important zones for this purpose are 1) internal waters, 2) the territorial sea (reaching to 12 nautical miles (nm)), 3) the contiguous zone (up to 24 nm from land), 4) the exclusive economic zone (up to 200 nm), and 5) the high seas. For domestic shipping and inland waterways, mainly performed in the first two zones, there are national and local emission regulations, often similar to those for land traffic. But for the international shipping, performed to a large degree outside the territorial sea, and also in different territorial seas, there is a demand for coordinated frameworks and regulations at a global scale. For the GHG reduction, also the impacts are at a global scale and not restricted to a specific nation or even region, setting demands for global agreements. For land-based activities, the responsibility lies on nations based on an international agreement (the Paris Agreement [3]). As mentioned above, the International Maritime Organization, IMO, has the corresponding responsibility the international shipping sector's GHG reduction.

The International Maritime Organization, IMO The International Maritime Organization, IMO, is a specialized agency of the United Nations with responsibility for measures to improve the safety and security of international shipping and to prevent pollution from ships [21]. The IMO currently has 174 member states. The main technical work is carried out by committees, among those the Marine Environment Protection Committee (MEPC) is handling issues related to environmental impact. The pollution prevention work of the IMO is defined by the International Convention for the Prevention of Pollution from Ships, MARPOL, adopted in 1973 with later amendments. The MARPOL addresses pollution from ships in six Annexes; by oil (Annex I), by noxious liquid substances carried in bulk (Annex II), by harmful substances carried by sea in packaged form (Annex III), by sewage and garbage (Annex IV), and also the prevention of air pollution from ships (Annex V). Annex VI treats Prevention of Air Pollution from Ships, which also includes GHG emissions.

The role of the IMO is to adopt legislation, but after adoption it has to be accepted by the individual member states, who, by accepting also agrees to make it part of the national law. The procedure to enact international maritime legislation is slow, due to the need for acceptance by the members and the following national processes, but when in place, it is implemented in a large number of countries globally.

The European Union, EU Regional regulations and agreements may also have large impact on the shipping sector's emissions. One large actor is the European Union, in which the European Commission, EC, is the politically independent executive arm. The EC is responsible for drawing up proposals for European legislation and implements the decisions of the European Parliament and the Council of Europe. There are different types of legal acts in the EU [22]. A regulation by the EU is a binding legislative act for the member states. The EU also issues directives, which are legislative acts that sets goals that all EU countries must achieve. The individual countries then have the freedom to devise own laws on how to reach the goals. A decision is binding on those addressed, e.g. an EU country or an individual company. A recommendation is not binding, but an advice to the countries and has no legal consequences. EU institutions can also express an opinion, which is not legally binding.

1.5.2 Present and coming regulations for low-carbon shipping

International shipping has for many years been focusing on reducing the emissions that have a high impact on human health as well as on local and regional environment. In the area of MARPOL Annex VI, air pollution from ships, emissions of sulfur oxide and nitrogen oxides have been regulated for a number of years. See Table 1.1.

Table 1.1

In the second IMO GHG study in 2009, there was an estimate of the potential emissions savings by different technologies and practices [23]. It was then concluded that the potential could be somewhere in the range between 25 and 75%. The operational speed was identified as an important parameter, but also hull and superstructure design has a large influence. In order to make a reduction of CO2/GHG emissions by design and operational measures, the Energy Efficiency Design Index (EEDI) was made mandatory for new ships and the Ship Energy Efficiency Management Plan (SEEMP) for all ships at MEPC 62 (July 2011) with the adoption of amendments to MARPOL Annex VI (resolution MEPC.203(62)), by Parties to MARPOL Annex VI. This was the first legally binding climate change treaty on shipping to be adopted since the Kyoto Protocol [24]. The EEDI requires a minimum energy efficiency level per capacity mile, like tonne mile, for different ship types and sizes. All new ships over 400 gross tonnages from the 1st of January, 2013 have to fulfill the minimum criteria of the EEDI [25] Tightened levels every five years are used to stimulate continued innovation and technical development. However, since the EEDI is only valid for new building, and with expected life-times of ships of 25 or more, the increase in energy savings rate is slow.

In the EEDI, the most energy intense segments of the merchant fleet were included from the beginning. These are tankers, bulk carriers, gas carriers, general cargo ships, container ships, refrigerated cargo carriers and combination carriers. In 2014 amendments were adopted to include also LNG carriers, ro-ro cargo ships, ro-ro passenger ships and cruise passenger ships having non-conventional propulsion. By 2021, the EEDI includes ship types that give rise to approximately 85% of the CO2 emissions from international shipping.

While EEDI is only applicable to new-built ships, the Ship Energy Efficiency Management Plan, SEEMP, adopted in 2016, is valid for existing ships [24]. The SEEMP is a tool for managing ship and fleet efficiency performance. The IMO has made it mandatory for every vessel over 400 gross tonnage to have on board a vessel specific plan. In order to support the implementation, a monitoring tool, Energy Efficiency Operational Indicator, EEOI, has been developed.

From March 2018 an amendment to Annex Vi on Data collection system for fuel oil consumption of ships entered into force. Here ships of 5000 gross tonnage and above are required to collect consumption data for each type of fuel oil the use and in addition data on transport work. The data is reported annually to the flag State who issues a Statement of Compliance. These data re transferred to an IMO Ship Oil Consumption Database. The summarized global data are then entered into an annual report to the MEPC.

The IMO has also adopted a resolution on Promotion of Technical Co-operation and Transfer of Technology relation to the Improvement of energy Efficiency of Ships [26]. This is focusing efforts on technical cooperation and capacity building to ensure smooth and effective implementation and enforcement of new regulations. The IMO is executing several projects in all regions of the world to support the implementation of measures to address GHG emissions from international shipping.

1.5.3 Other environmental regulations of importance

MARPOL Annex VI, emissions to air, had an early focus on regulations related to emissions to air in the form of sulfur and nitrogen oxides. This was due to observed impacts in ports and along fairways. The main impacts are related to human health as well as the natural and built environment. Sulfur is a source of acid precipitation as well as of particle formation. Lower sulfur content in fuel also reduces particle formation. NOx emissions are causing acid precipitation but also lead to formation of secondary pollutants like photochemical oxidants, which harm health as well as growth of plants. Since the sensitivity to acidification as well as to environmental is higher in some area, the establishment of Emission Control Areas, ECA, was performed. These today (2021) include the Baltic Sea, the North Sea, the English Channel, the United States Caribbean Sea and areas along the coasts of the United States and Canada.

The term SECA is sometimes used for the sulfur regulation. The sulfur is regulated as allowed content in the fuel and the limit is slower in SECAs. From 2015, permitted emissions of SO2 are limited to the equivalent of 0.1 wt. percent sulfur in combusted fuel within the SECAs, see Table 1.2. The emission level can be reached by using fuel of sulfur content less than 0.5 or 0.1 percent or by removing the sulfur from the exhausts. There is also a global sulfur cap. The global limit on the sulfur content of marine fuels was reduced to 0.5 percent sulfur by 2020. The earlier cap was 3.5 percent.

Table 1.2

For NOX, the regulations are also valid in the ECA areas as is shown in Table 1.2. Since the nitrogen mainly comes from the combustion air, it is not as straight-forward to set the limit, but it is related to the combustion engine with a relation to the rated engine speed, see Fig. 1.5.

Figure 1.5 NO x emission regulations.

In MARPOL (Annexes I, II, IV, V), there is a definition of certain sea areas as "special areas" in which there are special mandatory methods for the prevention of sea pollution required. The special areas are provided with higher level of protection than other areas of the sea. This relates specially vulnerable areas from oceanographic or ecological conditions.

There are also marine areas designated as Particularly Sensitive Sea Areas, PSSA, by the IMO. These are areas that need special protection, and which may be vulnerable to damage by international maritime activities. The criteria may be ecological, such as unique or rare ecosystem, diversity of the ecosystem or vulnerability to degradation by natural events or human activities. Also social, cultural and economic criteria such as significance of the area for recreation or tourism or scientific and educational criteria such as biological research or historical value can be the reason [27].

1.6 The potential for low carbon shipping – how do we get there?

The use of fossil fuel (coal, oil, gas) as an energy carrier for shipping has a quite short history as compared to shipping itself. Man has been sailing the oceans using wind power and without engines or emissions of GHG for centuries. But, if the demands and possibilities of today concerning travel times, time-tables, safety, working environment on board and other parameters are taken into account, the traditional sail ship is not fulfilling all criteria. There is a need for other energy carriers and technical solutions in most shipping applications. The available solutions for future shipping are dependent on the shipping segment and also the conditions of the geographical area of operation. There are special conditions where a modern sail ship can perform the desired task, although at a lower speed than today, and there are also concept ships under construction [28]. But, as is discussed in further detail in other chapters of this book, there are also many other technical, and other, solutions to low carbon propulsion that have the possibility to fulfill the demands.

Both for existing ships and for newbuilds, there are possibilities of technical nature that alone or in combination contribute to reach the goal of low or zero emission of GHG:

–  Increase the energy efficiency

–  Change to alternative (fossil free) fuel

–  Change energy conversion technology to fossil free

Increase of the energy efficiency can be performed in various ways, most easily by operational changes, sometimes including addition of new technology or refurbishment for existing ships. Using new and efficient technology and also applying a ship energy system perspective in the design of new ships will increase the possible savings [29].

Change to alternative (fossil free) fuel Since the traditional use of fossil fuels is well established and implemented with a well-developed infrastructure and, in many cases, long term contracts for fuel delivery, the driving force for change of fuel is quite low. Even with demands on low sulfur fuel and low NOx combustion, fossil fuels ((Low sulfur) Heavy Fuel Oil, (LS)HFO, Marine gas oil, MGO, and other distillates, low sulfur hybrid oils, Liquified Natural Gas, LNG etc.) provide the alternative that comes at lowest price

Change energy conversion technology to fossil free The most radical way of achieving the zero emissions is to change the energy conversion technology, for example to use fuel cells powered with hydrogen produced from renewable sources or batteries using electricity from renewable sources. The usefulness will depend both on technology availability as well as infrastructure and will also be dependent on shipping segment and geographical area.

The amount of emissions is very closely connected to the amount of (fossil) fuel used, and compared to road vehicles, each ship is often a large fuel consumer, although energy efficient in comparison. The large size gives opportunities to a large saving per unit in an efficient way. It is obvious that to minimize the use of fuel by energy efficiency, thus avoiding losses of energy and making the propulsion energy efficient, has potential to be both economical and, in comparison to other measures, easy to implement. This can be achieved not only for new-builds but also for existing ships and engines. Slow steaming is often mentioned, and it can be efficient and quick to implement, although there may by a conflict in running engines and ships far from design conditions that counteracts parts of the savings. Also demands on transport time, especially for passengers and sensitive goods can be a challenge. Maintenance can also be an important parameter to energy efficiency.

1.6.1 Visions

Since more and more countries, regions and organizations adhere to the strategy of phasing out fossil carbon use, at least to a large degree until 2050, also the shipping community sees more and more initiatives and consortia aiming at promoting this goal.

In its vision, the IMO states that [14]:

IMO remains committed to reducing GHG emissions from international shipping and, as a matter of urgency, aims to phase them out as soon as possible in this century.

The European Commission aims to make Europe the first climate-neutral continent by 2050, to counteract climate change [30].

Some examples of specific commitments in North Europe are that Denmark has a commitment to reduce GHGs by 70% from 1990 levels by 2030 [31], Finland aims to be net zero by 2035 [32], and Sweden by 2045 [33]. Among non-EU European countries in the region, Norway has the aim to reduce its greenhouse gas emissions by at least 40% from 1990 levels by 2030 and at least 80% by 2050 [34]. Iceland aims at carbon neutrality by 2040 [35]

1.6.2 Strategies

In order to decrease environmental impact in a sustainable manner, the goal has to be considered, not the specific (technical) solution, and there are various strategies to reach the coal that can be applied. These come at different cost and effort. The primary goal, independent of strategy, is to reduce emissions of GHG, and to do so as fast as possible. Also, if possible, to reduce the amount of GHGs present in the atmosphere. However, this has to be done while keeping high ambitions also to reduce or not cause new environmental impacts. Since the emission goals and statistics are made for the direct emissions from the ship, from a global sustainability perspective it is crucial to be careful not to move emissions from shipping to other sectors, e.g. by producing zero-emission fuel by processes that are high emitters and energy