The main type of “bunker” oil for ships is heavy fuel oil, derived as a residue from crude oil distillation. Crude oil contains sulphur which, following combustion in the engine, ends up in ship emissions. Sulphur oxides (SOx) are known to be harmful to human health, causing respiratory symptoms and lung disease. In the atmosphere, SOx can lead to acid rain, which can harm crops, forests and aquatic species, and contributes to the acidification of the oceans.
Limiting SOx emissions from ships will improve air quality and protects the environment.
IMO regulations to reduce sulphur oxides (SOx) emissions from ships first came into force in 2005, under Annex VI of the International Convention for the Prevention of Pollution from Ships (known as the MARPOL Convention). Since then, the limits on sulphur oxides have been progressively tightened.
From 1 January 2020, the limit for sulphur in fuel oil used on board ships operating outside designated emission control areas is reduced to 0.50% m/m (mass by mass). This will significantly reduce the amount of sulphur oxides emanating from ships and should have major health and environmental benefits for the world, particularly for populations living close to ports and coasts.
Limiting SOx emissions from ships will have a very positive impact on human health: how does that work?
Simply put, limiting sulphur oxides emissions from
ships reduces air pollution and results in a cleaner environment. Reducing SOx also
reduces particulate matter, tiny harmful particles which form when fuel is
burnt.
A study on the human health impacts of SOx emissions
from ships, submitted to IMO’s Marine Environment Protection Committee (MEPC)
in 2016 by Finland, estimated that by not reducing the SOx limit
for ships from 2020, the air pollution from ships would contribute to more than
570,000 additional premature deaths worldwide between
2020-2025.
So a reduction in the limit for sulphur in fuel oil used on board ships will have tangible health benefits, particularly for populations living close to ports and major shipping routes.
Do small ships have to comply with the sulphur limit from 2020?
Yes, the MARPOL regulations apply to all ships. Only larger ships of 400 gross tonnage and above engaged in voyages to ports or offshore terminals under the jurisdiction of other Parties have to have an International Air Pollution Prevention Certificate, issued by the ship’s flag State. But all sizes of ships will need to use fuel oil that meets the 0.50% limit from 1 January 2020.
Some smaller ships may already be using fuel oil that meets the limit, such as a marine distillate suitable for their engines. (Small ships operating in the already-designated emission control areas will be using fuel oil that meets the 0.10% limit in those emission control areas.)
Does the sulphur limit apply only to ships on international voyages?
The sulphur oxides regulation (MARPOL Annex VI, regulation 14) applies to all ships, whether they are on international voyages, between two or more countries; or domestic voyages, solely within the waters of a Party to the MARPOL Annex.
What was the regulation on SOx in ships emissions and by how much has it improved?
We have seen a substantial cut: to 0.50% m/m (mass by mass) from 3.50% m/m.
For ships operating outside designated emission control areas the previous limit for sulphur content of ships’ fuel oil was 3.50% m/m.
The limit is now 0.50% m/m, since1 January 2020.
There is an even stricter limit of 0.10% m/m in effect in emission control areas (ECAS) which have been established by IMO. This 0.10% m/m limit applies in the four established ECAS: the Baltic Sea area; the North Sea area; the North American area (covering designated coastal areas off the United States and Canada); and the United States Caribbean Sea area (around Puerto Rico and the United States Virgin Islands).
Fuel oil providers supply fuel oil which meets the 0.10% m/m limit (such as marine distillate and ultra-low sulphur fuel oil blends) to ships which require this fuel to trade in the ECAs.
What must ships do to meet the new IMO regulations?
The IMO MARPOL regulations limit the sulphur content in fuel oil. So ships need to use fuel oil which is inherently low enough in sulphur, in order to meet IMO requirements.
Refineries may blend fuel oil with a high (non-compliant) sulphur content with fuel oil with a sulphur content lower than the required sulphur content to achieve a compliant fuel oil. Additives may be added to enhance other properties, such as lubricity.
Some ships limit the air pollutants by installing exhaust gas cleaning systems, also known as “scrubbers”. This is accepted by flag States as an alternative means to meet the sulphur limit requirement. These scrubbers are designed to remove sulphur oxides from the ship’s engine and boiler exhaust gases. So a ship fitted with a scrubber can use heavy fuel oil, since the sulphur oxides emissions will be reduced to a level equivalent to the required fuel oil sulphur limit.
Ships can have engines which can use different fuels, which may contain low or zero sulphur. For example, liquefied natural gas, or biofuels.
Are all types of scrubbers allowed under IMO rules?
Yes, so long as they achieve the same level of emissions reduction.
Regulation 4 of MARPOL Annex VI allows for Administrations (flag States) to approve “equivalents” – any “fitting, material, appliance or apparatus to be fitted in a ship or other procedures, alternative fuel oils, or compliance methods used as an alternative to that required” – that enables the same standards of emission control to be met.
For reduction of sulphur oxide emissions, some flag States have accepted and approved scrubbers – otherwise known as “Exhaust Gas Cleaning Systems”, as meeting the requirements for sulphur oxide reduction.
There is an important requirement in the same regulation on Equivalents, which says that in paragraph 4 “The Administration of a Party that allows the use of an equivalent …. shall endeavour not to impair or damage its environment, human health, property, or resources, or those of other States”.
IMO has adopted strict criteria for discharge of washwater from EGCS. Any residues, where generated by the EGC unit usually in a closed-loop configuration, should be delivered ashore to adequate reception facilities. Such residues should not be discharged to the sea or incinerated on board.
Open-loop scrubbers add water to the exhaust gas which turns sulphur oxides (SOx) to sulphates/sulphuric acid. Open-loop scrubbers return washwater to the sea. The washwater must meet strict criteria, so that discharge washwater should have a pH of no less than 6.5. There are also strict limits on discharge of PAHs (Polycyclic Aromatic Hydrocarbons) and nitrates.
The guidelines, with the washwater criteria, (last revised and adopted in 2015), are currently under review in the IMO Sub-Committee on Pollution Prevention and Response (PPR).
Some Member States have raised environmental concerns about EGCS discharge and the Marine Environment Protection committee (MEPC) at its last session in May 2019 asked the PPR Sub-Committee to look into “Evaluation and harmonization of rules and guidance on the discharge of liquid effluents from EGCS into waters, including conditions and areas”.
IMO is liaising with the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP), an advisory body that advises the United Nations (UN) system on the scientific aspects of marine environmental protection. A GESAMP task team was established to assess the available evidence relating to the environmental impact of discharges of exhaust gas cleaning system effluent. its findings are being reported to the PPR Sub-Committee (PPR 7, 16-21 February 2020). (Note: submissions to IMO can be found on the IMODOCS website, registration required)
Why have some ports already banned discharge of washwater?
Some IMO Member States have taken a precautionary approach towards washwater discharge and have taken measures to limit or restrict discharge of washwater in their local ports and coastlines.
States have the right under UNCLOS to adopt their own laws and measures to reduce and control pollution of the marine environment from ships in their ports, internal waters and territorial seas.
Are new fuels being used to meet the 2020 limit?
Yes, new blends of fuel oil for ships have been developed. For example, a gas oil, with a very low sulphur content can be blended with heavy fuel oil to lower its sulphur content.
Ships can also choose to switch to a different fuel altogether. Or they may continue to purchase heavy fuel oil, but install ”scrubbers” to reduce the output of SOx in order to have an equivalent means to meet the requirement.
Of course, some ships were already using low sulphur fuel oil to meet the even more stringent limits of 0.10% m/m when trading in the established emission control areas. So those fuel oil blends suitable for ECAS, also meet the 0.50% m/m limit in 2020.
A study commissioned by IMO into the “Assessment of fuel oil availability” concluded that the refinery sector has the capability to supply sufficient quantities of marine fuels with a sulphur content of 0.50% m/m or less and with a sulphur content of 0.10% m/m or less to meet demand for these products, while also meeting demand for non-marine fuels.
Are low sulphur blend fuel oils safe? Can new low sulphur fuels cause problems for a ship’s engine?
All fuel oil for combustion purposes on a ship must meet required fuel oil quality standards, as set out in IMO MARPOL Annex VI (regulation 18.3). For example, the fuel oil must not include any added substance or chemical waste that jeopardizes the safety of ships or adversely affects the performance of the machinery.
IMO has discussed how to identify any potential safety issues related to new blends of fuel oil as it is recognized that if these fuels are not managed appropriately, there could be compatibility and stability issues. Guidance on best practice for fuel oil suppliers has also been issued. The Guidance is intended to assist fuel oil purchasers and users in assuring the quality of fuel oil delivered to and used on board ships, with respect to both compliance with the MARPOL requirements and the safe and efficient operation of the ship. The guidance pertains to aspects of the fuel oil purchase up to the loading of the purchased fuel oil on board.
An International Standardization Organization (ISO) standard (ISO 8217) specifies the requirements for fuels for use in marine diesel engines and boilers.
ISO has issued a further standard: ISO/PAS 23263:2019 Petroleum products – Fuels (class F) – Considerations for fuel suppliers and users regarding marine fuel quality in view of the implementation of maximum 0.50 % sulphur in 2020. It addresses quality considerations that apply to marine fuels in view of the implementation of the sulphur 2020 limit and the range of marine fuels that will be placed on the market in response. It defines general requirements that apply to all 0.50% sulphur fuels and confirms the applicability of ISO 8217 for those fuels. It gives technical considerations which might apply to particular fuels for the following characteristics: kinematic viscosity; cold flow properties; stability; ignition characteristics; and catalyst fines. Additionally, it provides considerations on the compatibility between fuels and gives additional information on ISO 8217.
Source: http://www.imo.org/en/MediaCentre/HotTopics/Pages/Sulphur-2020.aspx