TEXTE Environmental Impacts of Exhaust Gas Cleaning Systems for Reduction of SOx on Ships — Analysis of status quo 
Report compiled within the framework of the project ImpEx 
Summary 
The present report provides an overall review on the status quo of Exhaust Gas Cleaning 
Systems (EGCS), with special focus on the environmental aspects of the discharge water. It is 
based on a literature review and covers technical aspects, market analyses, the regulatory 
framework and recent research activities related to this topic. The work was carried out within 
'he project ImpEx (WP 1). 
Open loop (OL), closed loop (CL) and hybrid EGCS have been installed on board ships since the 
introduction of international regulations on sulphur emissions from maritime traffic, EGCS 
discharge water has an acidic pH and contains several pollutants, such as heavy metals, 
polycyclic aromatic hydrocarbons (PAHs), oil residues and nitrate. Thus, there are concerns 
regarding the impacts on the marine environment due to these emissions. The discharge volume 
depends on the type of system. In the case of OL systems, it is strongly dependent on the 
alkalinity of the surrounding water. In the past, 45 m*/MWh was commonly assumed as average 
flowrate; recent studies, however, indicate average flowrates of around 90 m*/MWh. 
Notifications of approved EGCS on board ships from the Global Integrated Shipping Information 
System (GISIS) database of the International Maritime Organization (IMO) were used and 
complemented to generate a database about the current market penetration of this technology. 
This information was compared to market analyses carried out by private entities. The market 
analyses indicate that the current number of ships with EGCS is above 3,000, representing about 
3.1% of the global fleet but more than 16.8% of global dead weight tons (DWT). OL systems 
dominate the market (>80%), followed by hybrid systems (15%). EGCS are now strongly 
present on ship types other than ferries and cruise ships compared to numbers from 2019; bulk 
carriers, tankers and container ships are the top adopters of this technology. 
The current COVID-19 pandemic has impaired the installation progress of EGCS, leading to 
uncertainties in short-term market estimations. Along-term prognosis shows a fuel market 
share of 10% for heavy fuel oil in combination with EGCS by 2050. The actual development of 
EGCS and other regulatory-compliant solutions may be affected by the fluctuation of fuel prices, 
the uncertainty in fuel demand and availability, the modification of legal framework (including 
regulations for other emissions besides sulphur oxide emissions) and the development of new 
technologies and energy sources. 
The EGCS discharge water is internationally addressed by the EGCS Guidelines of the IMO that 
are referenced in the European law and consequently in the German law. However, in several 
ports and regions worldwide additional regional and local restrictions to EGCS discharge water 
were adopted. In this regard, work is currently ongoing within the IMO Marine Environment 
Protection Committee (MEPC) and its Sub-Committee on Pollution Prevention and Response 
(PPR) on harmonization of rules and guidance on the discharge of EGCS discharge water. 
The EGCS Guidelines were recently reviewed and the revised version (“2020 EGCS Guidelines”) 
is expected to be adopted in the session 76 of the MEPC. The “2020 EGCS Guidelines” address 
some of the issues of the current version of the EGCS Guidelines (2015), such as the necessity of 
a definition of phenanthrene equivalent for measurement of PAHs (PAHyne) and the lack of 
clarity for release of tank stored EGCS discharge water. However, the limit values set in the 
discharge criteria remain unchanged. This literature review could not establish any underlying 
documentation resulting in the determination of the limit values referenced by the IMO EGCS 
Guidelines, especially for turbidity and PAHyne. Thus, it is questionable whether these criteria in 
fact ensures the protection of the marine environment. The current discharge criteria (for 
turbidity, PAHyne and nitrates) does not represent any practical restriction for conventional OL 
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