Results

i. Emissions Abatement Technologies

The project evaluated a wide range of technologies to control emissions of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter (PM) emitted by ships.

• Scrubbers achieved a substantial reduction (approximately 98.8%) in SO2 emissions but led to higher Particle Number emissions and a 2% increase in fuel consumption. In addition, they discharge chemically treated water into the sea.
• Selective catalytic reduction (SCR) effectively reduced NOx, but increased CO emissions downstream.
• Diesel oxidation catalyst (DOC) reduced CO, HC, and PM emissions, with distillate fuel yielding the lowest PM emissions.
• Diesel particle filter (DPF) increased fuel consumption by 1.5% and raised CO2 and SO2 emissions. Positive percentages indicated reduced Emission Factors (EFs) post-treatment.

Table 1: Overview of emission reduction percentage of different emission control technologies. Negative values indicate an increase

Emission control technology	Fuel	SFOC (%)	CO (%)	NOX (%)	SO2 (%)	NMVOC (%)	PM (%)
Wet Scrubber	Bunker Fuel Oil	-2,15	22,7	5,84	98,8	36.3	35,8
	MDO/MGO	n.r.	n.r.	n.r.	n.r.	n.r.	n.r.
SCR	Bunker Fuel Oil	-0,335	-59,3	89,0	9,55	68,5	15,1
	MDO/MGO	-0,452	-100	82,0	6,57	78,3	4,71
DOC	Bunker Fuel Oil	1,09	30,7	-0,814	-0,899	69,0	50,0
	MDO/MGO	1,09	30,7	-0,814	-0,899	69,0	50,0
DPF	Bunker Fuel Oil	n.r.	n.r.	n.r.	n.r.	n.r.	n.r.
	MDO/MGO	-1,50	0,00	0,00	0,00	0,00	91,70

Moreover, eight future scenarios for 2030 and 2050 explored the effects of different marine traffic developments, alternative fuels, and potential bans on scrubber discharges.

These findings help stakeholders tailor solutions to specific operational needs while advancing environmental goals.

ii. Atmospheric and Water Quality Modeling

The EMERGE project refined state-of-the-art models to predict the environmental impacts of shipping emissions:

• STEAM (Ship Traffic Emission Assessment Model): Updated to simulate i) the impact of different weather and sea conditions, including wind, sea waves, sea ice and sea currents, on the fuel consumption and emissions from shipping and ii) the fuel consumption and emissions from ships using methanol as a fuel. Updated emission factors now cover engines running on methanol and other alternative fuels.
• ChemicalDrift Model: Developed to track the transport and degradation of pollutants like heavy metals and PAHs in aquatic ecosystems. The improved ChemicalDrift was applied at European and local scales using STEAM data as input.
• Regional scale atmospheric dispersion models, such as, e.g., WRF-CMAQ (Weather Research and Forecasting – Community Multiscale Air Quality Model) and SILAM (System for Integrated modeLling of Atmospheric composition) and water quality and circulation models, such as, ChemicalDrift (Open source model for the drifting of substances in the ocean) and Delft3D (oceanographic model) integrated inputs from STEAM predicted air emission and water discharge values, ships, land sources, and atmospheric deposition to evaluate pollutant dispersion in sensitive regions such as the Baltic Sea, the North Sea, and the Mediterranean Sea Area.

These models provided critical data for assessing and mitigating shipping-related pollution.

iii. Ecotoxicological Impacts

The impact of scrubber water discharges on marine life was a focal point of the project:

• Toxicity of Scrubber Water: Whole effluent toxicity testing in several laboratories were conducted for a collection of marine species and their different development stages. Based on lab tests and QSAR (Quantitative Structure– Activity Relationship) models, Predictive No Effect Concentration (PNEC) values were determined and alkylated polycyclic aromatic hydrocarbons (alkyl–PAHs) were found to significantly contribute to the toxicity of scrubber water.
• Ecotoxicological Findings: Early life stages of marine invertebrates showed deformations and reduced survival even at extreme dilution (1:1,000,000). At these low concentrations of EGCS effluent, notable effects included diminished egg production, deformations, and abnormal development of the larvae of these species.
• Risk assessment: The environmental impact of both open– and closed–loop EGCS discharge is considerably higher than that of other onboard liquid waste streams, such as ballast water, bilge water, sewage, and grey water.
• Recommendations: Inclusion of alkyl-PAHs in monitoring and regulation criteria alongside standard EPA-listed PAHs.

Figure 1. The lowest observed effect concentration (LOEC) of EGCS effluent on different tested organisms and endpoints from experiments carried out within the EMERGE project. The different organism groups and species tested are shown on the X-axis and the dilution of EGCS effluent is shown on the Y-axis.

This research highlights the urgent need for stricter controls on scrubber discharges to protect marine ecosystems.

Figure 2. ChemicalDrift simulations of dilution factor of scrubber water for baseline year 2018 and scenario 3 (2050) indicating areas with harmful concentrations. For further explanation and details, see D6.2 and D6.3. PNEC (Predicted No Effect Concentration) was derived in D6.1.

v. Economic Evaluation of EGCS Usage

The economic analysis of emission control systems provided mixed insights:

• Cost Efficiency: The majority of the global EGCS fleet has already amortised the costs of their investments. Within a period of five years, almost all of the global EGCS fleet makes profit with the continued use of high sulfur fuels when compared to switching to low sulfur fuels.
• Policy Implications: Prolonged EGCS usage delays the adoption of cleaner alternatives like low-sulfur fuels and aligns poorly with global greenhouse gas reduction targets.

This research underscores the importance of aligning economic incentives with environmental objectives

vi. Decision Support Tool and Cost-efficient methods for reducing shipping emissions and environmental Impacts

A web-based decision support tool developed by EMERGE enables stakeholders to evaluate the environmental and economic impacts of various shipping scenarios. This tool is online and can be accessed https://gains.iiasa.ac.at/dashboard/eiindex/index.menu upon registration in GAINS (Greenhouse Gas – Air Pollution Interactions and Synergies). In particular, it:

• Integrates seven impact endpoints linked to Sustainable Development Goals (SDGs).
• Provides spatial and temporal assessments for informed decision-making.
• Is available online for policymakers, researchers, and industry leaders.
• Bridges the gap between complex data and actionable strategies.

Assessment of the costs of emission reduction for atmospheric pollutants showed that the reduction of SO2 and NOx from shipping is cost-efficient, while PM and CO2 reductions are cheaper for land-based sources.

vii. Conclusions and Recommendations

The EMERGE project delivered a comprehensive framework for understanding and mitigating the environmental impacts of shipping emissions. Key recommendations include:

• Adopting policies that quickly discourage the use of EGCS with high-sulfur fuels,
• Adopting cleaner and sustainable energy sources within the maritime industry,
• Considering both atmospheric deposition and direct discharges of pollutants into marine environments during the regulatory process.
• Swiftly implementing a policy to restrict scrubber water discharge in regional sea areas

By providing data-driven insights and practical tools, EMERGE project has played a major role in advancing our knowledge of the environmental effects of shipping, specifically in relation to EGCS usage and its impacts on the atmosphere and marine ecosystems.

Tidelines Initiative

The Tidelines initiative is an innovative, multi-media, multi-stakeholder collaboration involving university academics, the University of Southampton’s Widening Participation and Social Mobility team, local schools, scientists from EMERGE, and a local professional artist, Ricky Tart. Led by the University of Southampton’s Ian Williams (an EMERGE partner) and Ricky Tart (Director of “Trickyart”), the project aimed to engage young people, particularly those from disadvantaged backgrounds, in addressing climate change and marine pollution.

Through field visits, scientific investigations, and creative workshops, primary and secondary school students explored coastal environments, discussed shipping-related impacts on coasts, and sustainable solutions, including technological and environmental strategies. These experiences inspired the children to express their ideas through poetry, drawing on scientific knowledge from the EMERGE project.

A highlight of the initiative is the “Listen Up Businesses” rap song and video, alongside three eBooks, capturing the children’s voices and their call for sustainable solutions. This creative piece reflects the energy and impact of the initiative and is showcased below: