Scrubbers are a hot item in the European Sustainable Shipping Forum discussions. However, the difference in implementation between international (UN) and the United States needs more attention.

Clean Marine Exhaust Gas Cleaning System; hybrid system that can run in closed and open loop.

International regulation

The UN International Maritime Organisation (IMO) 2009 Guidelines for Exhaust Gas Cleaning Systems (MEPC.184/59)) provide effluent limits for pH, PAH, nitrates, turbidity, and temperature. These guidelines allow the pH to meet a limit of 6.5 at 4 metres from the discharge pipe, meaning that an open loop scrubber may discharge wash water with a pH as low as 3.0 before being diluted in the receiving water.

This dilution discussion was on the Marine Environment Protection committee (MEPC) agenda in January 2015 and covered alternative modelling and calculation methods, titration curves and pH normalisation.

US federal effluent requirements

The Environmental Protection Agency Vessel General Permit (EPA VGP) last updated in 2013 and dealing with 27 discharges of marine vessels, more specifically rules the discharges of exhaust gas scrubber wash water in US waters within 3 nautical miles of the coastline. According to the EPA, the effluent pH should be as low as 6.0 at the discharge pipe, but no dilution trials or models at any distance from the discharge pipe are accepted. In practice, this makes the EPA limit extremely more restrictive and could prevent the use of open loop scrubbers within the 3 nautical miles of the US coastline.

Moreover, there are quite some no discharge zones, preventing any discharges:

  • California: within Water quality Protection Areas, no discharge, except in discharges occurring in transit associated with vessel traffic separation lanes;
  • Connecticut: discharge of wash water explicitly prohibited;
  • Hawaii: no discharge to natural fresh water lakes, saline lakes, and anchialine pools;
  • Marine sanctuaries: no explicit prohibition of wash water discharge, but recommendation to avoid discharge.

European regulation

The European Sustainable shipping Forum (ESSF) is also drafting guidelines for enforcing sulphur regulations / wet exhaust gas cleaning systems, covering topics such as “how to handle accidental breakdown, instrumentation malfunction and perceived non-compliance”.

We will update you when a common approach is in place.