The new regulations that have already, and continue to, come into effect around the world regarding the control of Sulphur Oxides (SOx) and Nitrogen Oxide (NOx) gases has raised the cost of operations by forcing the use of low sulphur fuel and other mitigating alternatives. However, the changes in legislation have also ignited and fostered innovations in cleaning of marine exhaust gases. The sustainability of the advances in scrubbing technology are only possible while the return on investment fits a sound business case and although lower fuel prices threaten the progress in technological advances it is certain that environmental legislation will move the efforts along.
The existing MARPOL Annex VI legislation that came into effect May 19, 2005, adoption of several European Union directives, and California Air Resources Board (CARB) are among the leading legislations that have molded the impact of the performance of marine diesel on the environment. Although some ports and local jurisdictions have adopted alternatives the gist of the legislation roll out is as follows:
January 1, 2000 to January 1, 2011: Newly installed Diesel Engines are stipulated to cap NOx at 17 g/kW standard while existing Marine Diesel Engines with a power output of more than 5,000 kW and a displacement per cylinder at, or above, 90 liters installed on a ship constructed on or after January 1, 1990 are capped at an emission limit of 17 g/kWh – as per MARPOL Annex VI
January 1, 2010: European Union ports start enforcing a Sulphur limit of 0.10% (1,000 ppm) – as per EU Directives
March 1, 2010: Countries that have adopted to an Emission Control Area (ECA) start imposing a Sulphur limit of 1.00% (10,000 ppm) which is reduced from the current 1.50% (15,000 ppm) – as per MARPOL Annex VI
January 1, 2011 to January 1, 2016: Newly installed Marine Diesel Engines must comply to a NOx cap of 14.4 g/kW standard – as per MARPOL Annex VI
January 1, 2012: The global sulphur cap will be reduced to 3.50% (35,000 ppm), from the current 4.50% (45,000 ppm) – as per MARPOL Annex VI
January 1, 2012: Greek ferries at Greek ports start enforcing a Sulphur limit of 0.10% (1,000 ppm) – as per EU directives
January 1, 2015: Countries that have adopted to an Emission Control Area (ECA) start imposing a Sulphur limit of 0.10 % (1,000 ppm) – as per MARPOL Annex VI
January 1, 2016: Newly installed Marine Diesel Engines must comply to a NOx cap of 3.4 g/kWh standard while operating within areas of Countries that have adopted to an Emission Control Area (ECA) otherwise the 14.4g/kWh applies – as per MARPOL Annex VI
January 1, 2020: The global sulphur cap would be reduced to 0.50% (5,000 ppm). The enforcement is subject to a feasibility study to be completed by 2018 and with a negative conclusion, the effective date would default to 1 January 2025 – as per MARPOL Annex VI
In addition: Introduction of fuel availability provision under regulation 18 Fuel Oil Availability and Quality that outlines what actions are appropriate should a ship be unable to obtain the fuel necessary to comply with a given requirement under regulation 14 – as per MARPOL Annex VI
Ideally the improved performance of diesel engines and the use of distilled quality fuels would simplify matters. However, the cost implications from higher quality fuel and increased CO2 emissions at refineries.
SOx scrubbers (wet and inert gas type) are the technologies that have emerged as leading candidates to the impending legislation even though the lack of clarity by the disparity in geographical requirements in wash water discharge criteria has clouded the path ahead. Scrubbers that fall under IMO Resolution MEPC.130(53) will need a Sulpher Emissions Control Area (SECA) Compliance Plan (SCP) and similarly to NOx regulations for Diesel Engines that call for several technical documents describing details of the equipment, the scrubber performance needs to be demonstrated and approved under a SECA Compliance Certificate (SCC). The wash water from the scrubber is also subject to IMO regulation under the Wash Water Guidelines while the EU Directives provide unit approval and continuous monitoring schemes. The challenge however resides in the understanding of the effluent and residue wash water and how the different techniques used vary. Unlike the inert gas type scrubbers, some typical marine wet scrubbers “open-loop” models are dependent on sea water alkalinity while “closed-loop” models are not. For the “open-loop” type, the lower the alkalinity of the sea water, the lesser efficiency of the sea water scrubber because alkalinity is the ability to resist change in pH. The sea water alkalinity is used to neutralize the sulphur in the exhaust gas and it needs a high flow of seawater and even higher when the alkalinity is low. Alternatively a fresh water, or “closed-loop”, wet scrubber can be used with the introduction of caustic soda (NaOH) to neutralize the sulphur filled exhaust gases. Although the added cost of using caustic soda can fluctuate additional expenses from 0.5% to 4.0% of the cost of fuel, and even include additional energy requirements, the ability to operate with HFO in an environmentally sound way make it a feasible proposition.
