Reduction Potential of Gaseous Emissions in European Ports Using Cold Ironing

: Providing electrical power to ships while they are docked, cold ironing allows ships to turn off their engines and reduces emissions of air pollutants and greenhouse gases. This study identifies and assesses ship and port emissions and analyzes the potential for emission reduction achievable by cold ironing in European ports. It includes (1) a review of the current state of cold ironing in European ports; (2) an analysis of the time spent in ports by ships; (3) a quantification of emissions potentially avoided by means of a larger-scale use of cold ironing in Europe; (4) an estimation of the benefits achievable and the perspective to play a role in meeting emission reduction targets, improving air quality in port cities; (5) an analysis of the challenges and limitations of larger-scale cold ironing implementation; (6) potential solutions to overcome them. The results of this study could have important implications for (a) the shipping industry, which could benefit from the need for additional standardized electrical equipment onboard; (b) port authorities, which could benefit from providing additional services to the ships; (c) policymakers working to reduce emissions and promote energy efficiency, who could better approach their local and global targets.


Introduction
Globalization, concentration, and the specialization of production increase the focus on the global supply chain, where seaports play a key role as transshipment hubs.In the last few decades, ports have become more and more important as global logistic actors [1].A vital part of port efficiency and port value proposition is seaside and landside connectivity and services.Moreover, the role of hinterland logistics and transportation is receiving increasing attention, and ports' strategies and management focus more and more on incorporating and coordinating hinterland logistic activities with the activities of the seaport [2].Ports are often publicly owned but often privately operated, normally by means of concessions.Ports are an interesting focal point since their activities, directly and indirectly, heavily affect the local and regional traffic system [3].Ports have the potential for the internalization of both social and environmental externalities by means of differentiated fees and other incentives.Indeed, sea transport has traditionally been seen as a green form of transportation due to the low emission of carbon dioxide per t-km compared to any other transport mode.However, given that around 90% of world trade is carried by international shipping and the sector is experiencing significant year-on-year growth, it nevertheless represents a major source of carbon emissions.In this framework, the cold ironing solution, consisting of shore electricity supply to ships, should play an increasing role in favor of the global decarbonization process.

General Approach to Maritime Decarbonization
As a follow-up to the Paris Agreement on global climate change and the UN Sustainable Development Goals (SDG) issued in 2015, the International Maritime Organization (IMO) target of a 50% reduction in emissions by 2050 for the shipping sector followed in 2018.The IMO deal represents a significant shift in climate ambition for a sector that accounts for 2-3% of global carbon dioxide emissions.It means a minimum greenhouse gas (GHG) emission reduction of at least 50% from 2008 levels by 2050 with a strong emphasis on increasing the cut towards 100% by 2050 if this becomes technically possible.The deal signals to the industry, and investors in general, that a clear switch away from fossil fuels is now decided.It means that ocean-going vessels built in the 2030s will no longer be dependent on fossil fuels only, and ships built in the 2020s will likely switch progressively to non-fossil fuels and alternative power sources.At the port level, actions in favor of environmental sustainability are increasing in number and effectiveness, as depicted in [4] by connecting these actions with the UN SDG.
More recently, adopted in July 2023 as part of the Commission's Fit for 55 legislative package to reduce EU greenhouse gas emissions by at least 55% by 2030, the FuelEU Maritime Regulation [5] promotes the use of renewable, low-carbon fuels and clean energy technologies for ships, essential to supporting decarbonization in the sector.It sets maximum limits for the yearly average GHG intensity of the energy used by ships above 5000 gross tonnages calling at European ports, regardless of their flag.Targets will ensure that the greenhouse gas intensity of fuels used in the sector will gradually decrease over time, starting with a 2% decrease by 2025 and reaching up to an 80% reduction by 2050.Those targets will become more ambitious over time to stimulate and reflect the necessary developments in technology and the uptake in the production of renewable and low-carbon fuels.The targets also cover methane and nitrous oxide emissions over the full life cycle of the fuels used onboard on a Well-to-Wake basis.The regulation also introduces additional zero-emission requirements for ships at berth-mandating the use of on-shore power supply or alternative zero-emission technologies in ports by passenger ships and containerships-with a view to mitigating air pollution emissions in ports, which are often close to densely populated areas.
Moreover, in June 2024, the directive [6] clearly states that "Member States shall provide the necessary legal framework to facilitate the connection to the distribution networks of public and private access recharging points with smart charging and bi-directional charging functionalities in accordance with Article 20a of Directive (EU) 2018/2001.Member States shall ensure that distribution system operators cooperate on a non-discriminatory basis with any undertaking owning, developing, operating or managing charging points for electric vehicles".This is also applicable to the grid connection of ships in ports.
By taking a life cycle, goal-based, and technology-neutral approach, the FuelEU Maritime Regulation allows for innovation and the development of new sustainable fuels and energy conversion technologies, offering operators the freedom to decide which fuels to use based on ship-specific or operation-specific profiles.The regulation also provides for different flexibility mechanisms, supporting existing fleets in finding suitable compliance strategies and rewarding first-movers for early investment in energy transition.It will enter into force completely from January 2025.Within this framework, it is more than natural that ports are increasingly interested in sustainable practices and their adoption to align themselves with the SDG within their area of responsibility.Today, shipping is responsible for a significant amount of CO 2 , NO x , SO x, and PM pollution and is estimated to be responsible for 3% of global greenhouse gas (GHG) emissions.Some European and American ports have implemented various technologies and operational measures to minimize emissions, achieving important global reductions that reach 50-95% at the local level.Cold ironing is one of the technologies implemented to achieve these goals.

Cold Ironing Concept
The cold ironing concept is a consolidated concept based on electricity supply onboard ships through a connection to a main fixed electrical grid instead of the use of the ship's generators [7].Nonetheless, the technological solutions are various and suffer from poor standardization [8].The power supply is provided through a high-voltage line and a main substation to reduce the voltage.Afterward, the current is distributed via underground cables to various quays, where a further conversion into the voltage and frequency required for the specific ship is normally necessary.The frequency conversion is an important aspect because the majority of ships' grids use 60 Hz frequency, while the fixed electricity network normally provides 50 Hz standard frequency.
The last step of the process is the connection, through the cables, of the dock's station with sockets placed onboard.Furthermore, depending on the onboard voltage, an additional transformer inside the ship may be required for the end use of electricity.Normally, during navigation, the main engine, supported by the auxiliary ones, generate the power for the motion and all other services of the ship.However, in ports, the main engine is switched off, and the energy need is normally satisfied by the auxiliary engines alone.Nevertheless, some big and modern cruise ships use diesel-electric propulsion during navigation and are not equipped with auxiliary engines.
Therefore, cold ironing allows engines to be turned off in ports and emissions to be drastically reduced because internal combustion engines are not working during berthing, and the emission of CO 2 in the atmosphere is prevented, as are local emissions of pollutant matter, noise, and vibrations.
The phases of the processes are the following: (1) The ship enters a port and docks at a berth or pier, The port provides an electrical connection point, (3) The electrical system of the ship is connected to the electrical connection point using a cable and a plug, (4) The electrical system of the ship is powered by the onshore electrical connection point, (5) The engines and the generators of the ship are switched off, and the zero-emission phase starts, (6) The electrical system of the ship powers all necessary onboard systems during the time spent at berth, (7) The ship is declared ready to depart, (8) The main engines and the auxiliary generators of the ship are switched on, and the zero-emission phase ends, (9) The onshore electrical connection is interrupted.

Methodological Approach
The research is organized according to the following methodological phases: (1) Extensive overview of the current state of cold ironing in European ports, which includes the following: a.
Search and analysis of data on cold ironing usage across EU ports, b.
Selection of a sampling group of 10 ports for the development of further investigations, c.
Estimation of power demand of ships at berths, d.
Estimation of emission/energy [g/kW/h] for auxiliary engines and electricity production, (2) Quantification of the time spent by ships in ports, based on a survey on a selected sampling group of ports, which includes the collection of MarineTraffic ® data for 2 weeks on dwell time in the sampling group of ports with cold ironing in operation, (3) Estimation of the potential reduction of gaseous emissions of various typologies of ships in ports achievable by cold ironing implementation, which includes the calculation of emissions from auxiliary engines in a reference scenario (without cold ironing) and during cold ironing in full operation (auxiliary engines switched off), (4) Estimation of global potential benefits, implementation challenges, and identification of technological and operational solutions, (5) Assessment of potential solutions and identification of further research needs.

Ports with Cold Ironing in Operation
The EU target to reduce local and global emissions during the time spent at berths is to provide shore power facilities for ships in all major ports by 2025, which seems very optimistic right now.
A present picture is also not easy to build because many projects are announced to be ongoing with potential short-term completion [9], but the investigation carried out with reference to the systems in operation in EU countries, Norway, and the United Kingdom highlighted 25 ports with at least one berth equipped to provide onshore electricity (cold ironing) to ships.A schematic map representing the geographic distribution of these ports is reported in Figure 1.
(3) Estimation of the potential reduction of gaseous emissions of various typologies of ships in ports achievable by cold ironing implementation, which includes the calculation of emissions from auxiliary engines in a reference scenario (without cold ironing) and during cold ironing in full operation (auxiliary engines switched off), (4) Estimation of global potential benefits, implementation challenges, and identification of technological and operational solutions, (5) Assessment of potential solutions and identification of further research needs.

Ports with Cold Ironing in Operation
The EU target to reduce local and global emissions during the time spent at berths is to provide shore power facilities for ships in all major ports by 2025, which seems very optimistic right now.
A present picture is also not easy to build because many projects are announced to be ongoing with potential short-term completion [9], but the investigation carried out with reference to the systems in operation in EU countries, Norway, and the United Kingdom highlighted 25 ports with at least one berth equipped to provide onshore electricity (cold ironing) to ships.A schematic map representing the geographic distribution of these ports is reported in Figure 1.For these 25 ports, a deeper analysis was finalized to check the availability of data concerning typologies of berths and usability by the various typologies of ships.The results showed that enough data were available to proceed with the study for only 10 of these 25 ports (Table 1).Therefore, this was considered the sampling set of ports for the next methodological steps.For these 25 ports, a deeper analysis was finalized to check the availability of data concerning typologies of berths and usability by the various typologies of ships.The results showed that enough data were available to proceed with the study for only 10 of these 25 ports (Table 1).Therefore, this was considered the sampling set of ports for the next methodological steps.
The sampling set is numerically limited but includes the largest European ports: Rotterdam, Antwerp, Hamburg, Amsterdam, Le Havre, and Genoa are in the top 10 of the EU ports for freight traffic.

Power Needs and Gaseous Emissions in Ports
An intriguing problem and possibly one of the greatest obstacles to an extensive application of cold ironing is the huge power needs of the ships during their stay in ports.An extensive investigation carried out from various typologies of sources, such as shipbuilders, ship owners, and cold ironing early implementers, allowed identification of the range of power needs per ships' categories summarized in Table 2.The next step was the calculation of the energy need depending on the estimations of the time spent in ports and the emission factors of auxiliary engines, e.g., in grams per kilowatt-hour [g/kWh], which are almost consolidated and moderately variable values, assumed from [10] for the present study (Table 3).Additionally, available data on the average emission factors from electricity production in the European Union according to the average mix of sources have been collected (Table 4).

Time Spent in Ports by the Ships
The next step was the quantification of the time spent by ships in ports.For this purpose, a two-week investigation focused on collecting data from the 10 sampling set ports.It was carried out by a systematic individual (ship-by-ship) analysis of the duration of the port's calls.The data source was the MarineTraffic ® portal.As an example, the graph in Figure 2 depicts the duration of the various ships' typologies at the 10 sampling ports in the first two weeks (336 h) of the year 2023.

Time Spent in Ports by the Ships
The next step was the quantification of the time spent by ships in ports.For this purpose, a two-week investigation focused on collecting data from the 10 sampling set ports.It was carried out by a systematic individual (ship-by-ship) analysis of the duration of the port's calls.The data source was the MarineTraffic ® portal.As an example, the graph in Figure 2 depicts the duration of the various ships' typologies at the 10 sampling ports in the first two weeks (336 h) of the year 2023.The differentiation among ports is very relevant, as is the variability by ship typologies: the average number of ships in ports is variable between 0.4 in Goteborg and 4.6 in Piraeus.Therefore, the potential effectiveness of the will be accordingly variable, with the highest values in the most crowded ports (e.g., Piraeus) and for the longest-staying ships (e.g., bulk carriers).

Potential Savings of Emissions
The combination of the time spent in ports differentiated by typology of ships (Figure 2) and the average emission factors (Figure 3) allowed the calculation of the global emissions of auxiliary engines at berths without cold ironing (Figure 4) and the global (CO2) and local (NOx and SOx) emissions savings achievable by using cold ironing according to EU25 electricity production mix and the corresponding average emission factors (Figure 5).The differentiation among ports is very relevant, as is the variability by ship typologies: the average number of ships in ports is variable between 0.4 in Goteborg and 4.6 in Piraeus.Therefore, the potential effectiveness of the will be accordingly variable, with the highest values in the most crowded ports (e.g., Piraeus) and for the longest-staying ships (e.g., bulk carriers).

Potential Savings of Emissions
The combination of the time spent in ports differentiated by typology of ships (Figure 2) and the average emission factors (Figure 3) allowed the calculation of the global emissions of auxiliary engines at berths without cold ironing (Figure 4) and the global (CO 2 ) and local (NO x and SO x ) emissions savings achievable by using cold ironing according to EU25 electricity production mix and the corresponding average emission factors (Figure 5).
According to these data, the potential global and local emissions savings at berths in the scenario with full implementation of cold ironing will be the following: The achievable results are very important.The reductions in local emissions (NO x , SO x , VOC, and PM) oscillate in the range of 94-97%; meanwhile, the reductions of CO 2 emissions are still over 50% and could be relevantly improved by the planned increase in renewable sources use to produce electricity that was 39.4% for EU27 in 2022, with big fluctuations across coastal countries, ranging between 79% in Denmark and 13% in Malta.Therefore, the achievable reductions would be amplified in ports with a national ratio of renewable sources to produce electricity over the average value, such as Amsterdam, Rotterdam, Piraeus, Barcelona, Hamburg, and Goteborg, and mitigated in Antwerp, Le Havre, London, and Genova.According to these data, the potential global and local emissions savings at berths in the scenario with full implementation of cold ironing will be the following: The achievable results are very important.The reductions in local emissions (NOx, SOx, VOC, and PM) oscillate in the range of 94-97%; meanwhile, the reductions of CO2 emissions are still over 50% and could be relevantly improved by the planned increase in renewable sources use to produce electricity that was 39.4% for EU27 in 2022, with big fluctuations across coastal countries, ranging between 79% in Denmark and 13% in Malta.Therefore, the achievable reductions would be amplified in ports with a national ratio of renewable sources to produce electricity over the average value, such as Amsterdam, Rotterdam, Piraeus, Barcelona, Hamburg, and Goteborg, and mitigated in Antwerp, Le Havre, London, and Genova.

Potential Benefits of Cold Ironing in European Ports
The analyses carried out highlighted that cold ironing implementation could potentially play a significant role in meeting emissions reduction targets and improving air quality in port cities, in alignment with various previous studies, including those from outside Europe [11].
The potential reduction of local and global emissions from ships in port docked and connected to the electrical grid with their engines turned off can help European ports to achieve important benefits: 1.It can significantly reduce emissions of air pollutants and greenhouse gases that have a negative impact on the health of humans and the planet, improving the local air quality and decelerating the global warming process; 2. It can help to save energy and reduce costs for ships: its utilization can decrease fuel utilization by about 50%, which can yield substantial fuel cost reductions for ships, thereby making them more competitive and ecologically sustainable; 3. It can bring economic benefits to ports, increasing revenue and creating jobs, thereby fostering economic development;

Potential Benefits of Cold Ironing in European Ports
The analyses carried out highlighted that cold ironing implementation could potentially play a significant role in meeting emissions reduction targets and improving air quality in port cities, in alignment with various previous studies, including those from outside Europe [11].
The potential reduction of local and global emissions from ships in port docked and connected to the electrical grid with their engines turned off can help European ports to achieve important benefits:

1.
It can significantly reduce emissions of air pollutants and greenhouse gases that have a negative impact on the health of humans and the planet, improving the local air quality and decelerating the global warming process; 2.
It can help to save energy and reduce costs for ships: its utilization can decrease fuel utilization by about 50%, which can yield substantial fuel cost reductions for ships, thereby making them more competitive and ecologically sustainable; 3.
It can bring economic benefits to ports, increasing revenue and creating jobs, thereby fostering economic development; 4.
It can help European ports and countries to meet their emissions reduction targets set by the European Union; 5.
It is a key element in the transition towards a low-carbon economy and sustainable shipping; 6.
It can also significantly reduce noise pollution as ships turn off their engines while docked; 7.
It can reduce the risk of accidents caused by ships' engines and auxiliary systems, such as oil spills and fires.
Consequently, investments in cold ironing technologies can ameliorate the ecological impact of shipping and advocate for clean and sustainable practices.

Potential Barriers for Cold Ironing Implementation
There are several barriers potentially challenging the implementation of cold ironing in European ports, which include the following [12]: Technical and logistics: the introduction of cold ironing technology requires significant investment in infrastructure and equipment, installing power supplies, transformers, and cables; this can be a complex and time-consuming process, requiring the involvement of multiple stakeholders, including port authorities, ship owners, and energy companies, Funding and financing: cold ironing can be a costly investment, and funding the necessary infrastructure and equipment can be challenging; ports and ship owners may need to work with governments, financial institutions, and other stakeholders to secure it.According to the literature, the total cost of retrofitting a ship with shore-side power equipment can range from 0.2 to 2.0 MEUR/berth, which demonstrates the importance of the local complexity of the connection between grid and berths, 3.
Standards and regulations: cold ironing is a relatively new technology, and there are currently no standardized guidelines for its implementation; this can make it difficult for ports and ships to define required equipment and infrastructure and ensure that the system is operating safely and efficiently [13], 4.
Limited availability of shore power: cold ironing is not widely available in all ports and ships, which can make it difficult for ships to plan their routes and schedules and limit the overall benefits of its use [9,14], 5.
Interoperability: different countries and ports have different standards, regulations, and infrastructure for cold ironing, which can make it difficult for ships to use the technology across ports; it is a significant challenge for shipping companies that operate in multiple countries and regions, 6.
Lack of awareness: some ports and ship owners may not yet be completely familiar with the technology and its benefits and may not be motivated to invest in it, which can be a significant barrier to the implementation of cold ironing, 7.
Grid infrastructure: some ports may not have the necessary power grid infrastructure to support the large power needs of cold ironing; this can make it difficult to implement the technology, 8.
Environmental regulations: cold ironing requires a large amount of energy, which can be derived from fossil fuels if renewable sources are not sufficient to cover the need; this can be a significant challenge for ports and ships that are looking to implement it in compliance with environmental regulations and targets [15], 9.
Safety: cold ironing systems can be vulnerable to power failures, power surges, and other issues that can affect the safety of ships, ports, and cargo; this can be a significant concern for ports and ships and can limit the overall benefits, 10.Technological progress: cold ironing technology is still in the development phase, and there are continuous advancements in the technology, which can be adopted in the future, such as hydrogen-based and other forms of alternative maritime power that could offer even greater emissions reduction benefits; therefore, ports and ships must be prepared to continuously update and improve their systems to stay competitive and maximize the benefits.

Potential Solutions to Overcome Barriers: Next Research Developments
Overcoming the identified barriers is firstly a matter of port-ship cooperation and collaboration with industry organizations, governments, and other stakeholders to develop and implement guidelines and best practices for cold ironing.These multidisciplinary aspects merit further development in future research streams combining technical solutions with normative and economic aspects capable of amplifying the achievements, which include the following: 1.
Technical and logistics: establishing standardized guidelines and protocols for the installation and operation of cold ironing systems can help to ensure safety and efficiency and reduce costs and complexity of the implementation, 2.
Funding and financing: establishing funding mechanisms, such as grants and lowinterest loans, to support the implementation of cold ironing.Additionally, ports and ship owners can collaborate with local governments, financial institutions, and other stakeholders to secure the needed funding [16], 3.
Standards and regulations: accelerating the multilateral standardization in equipment and the international agreements about concerned rules and regulations will pave the way to faster and more efficient implementations; the high-level framework recently consolidated by [5,6] should be enriched by the concerned harmonized technical standards, 4.
Limited availability of shore power: increasing the availability of shore power in ports by encouraging investment in the necessary infrastructure and equipment and by working with governments and other stakeholders to support the implementation, 5.
Interoperability: establishing a harmonized approach in the European Union and beyond by adopting a common set of standardized infrastructures can help to ensure that ships can use the technology while traveling across ports, 6.
Lack of awareness: increasing evidence of the achievable benefits among ship owners and other operators by providing information and training on the technology, as well as by promoting the benefits of cold ironing to the public, 7.
Grid infrastructure: upgrading the power grid infrastructure to support the large power needs by working with power companies and governments to invest in new infrastructure and equipment, 8.
Environmental regulations: using clean energy sources, such as wind, solar, and hydroelectric power, to generate the energy needed to make cold ironing compliant with environmental regulations and targets, 9.
Safety: establishing guidelines by working with industry experts and regulatory bodies to develop protocols for the safe operation of systems and components, 10.Technological progress: staying updated with the latest technological advancements so that ports and ships can adopt them, which can provide better results than the traditional cold ironing; additionally, ports and ships can invest in research and development to further improve the technologies and make them more efficient, reliable, and cost-effective.
Based on the remarks above, the implementation of cold ironing in European ports is encountering several challenging barriers, but with systematic and harmonized cooperative approaches and solutions, these can be overcome.

Conclusions
The extensive application of cold ironing is a promising solution to reduce emissions, improve the air quality in European ports, and limit GHG production, depending on electricity production processes.
Indeed, significant savings are achievable in emissions of SO x , NO x , PM and GHG.Nevertheless, various accompanying measures are recommended, such as investments in reliable power infrastructure, development of clear and consistent regulations, implementation of financial incentives for ship owners, and more intensive collaboration among stakeholders.
The research carried out also highlighted some limits, such as the following: A still restricted sampling group of ports with cold ironing in operation, partially limiting the generalizability of findings and feedback on implementation hurdles, resistance to adoption, etc., A certain lack of data on emissions and energy demands, often considered sensible and not disclosable by the concerned stakeholders.
Beyond these limits, the following set of further primary research developments finalized to remove remaining technical, socio-economical, and normative uncertainties and hurdles have been identified: Enlargement of the sampling groups of ports in Europe and worldwide, Comparison of effectiveness and integration with other initiatives, such as electric or hydrogen-powered cargo handling equipment, Addressing concerns and educating stakeholders, Prediction of long-term impacts, Prediction of effects on local communities, such as health and well-being, including noise and vibration reduction,

Figure 1 .
Figure 1.Ports with berths equipped to provide cold ironing services.

Figure 1 .
Figure 1.Ports with berths equipped to provide cold ironing services.

Figure 3 .
Figure 3. Emissions factors of auxiliary engines using 2.7% sulphur fuel, 0.1% sulphur fuel, and shore connection (cold ironing) based on EU25 power generation mix.

Figure 4 .
Figure 4. Global emissions of auxiliary engines at berths without cold ironing.

Figure 4 .
Figure 4. Global emissions of auxiliary engines at berths without cold ironing.Figure 4. Global emissions of auxiliary engines at berths without cold ironing.

Figure 4 .
Figure 4. Global emissions of auxiliary engines at berths without cold ironing.Figure 4. Global emissions of auxiliary engines at berths without cold ironing.

Figure 5 .
Figure 5. Emissions savings achievable by using cold ironing according to EU25 electricity production mix and the corresponding average emission factors.

Figure 5 .
Figure 5. Emissions savings achievable by using cold ironing according to EU25 electricity production mix and the corresponding average emission factors.

Table 1 .
Sampling set of ports providing cold ironing services.

Table 2 .
Power needs of ships [MW] during their stay in ports, reported in decreasing order.

Table 3 .
Average emission factors of auxiliary engines operating in ports [g/kWh].

Table 4 .
Average emission factors from electricity production in the EU [g/kWh].