Dark Water: Ships Are Polluting The Air Less But More Water Pollution


    In News

    According to the International Maritime Organization’s (IMO’s) Sulphur 2020 vision, the ships are creating less air pollution but their water-pollution footprint is rising. 


    • The use of exhaust scrubbers, a move to reduce pollution of the air by ships, ironically, seems to be driving up water pollution.
    • There are two types of scrubbers:
    • Open-loop: dumps the scrubber wastewater into the sea/at the port and 
    • Closed-loop: treats the wastewater before dumping. 
    • Sulphur from ships’ exhaust is a significant contributor to ozone depletion

    IMO’s Move to Contain Sulphur

    • On January 1, 2020, the International Maritime Organisation (IMO) started the enforcement of a rule banning sulphur-heavy fuel
    • International Maritime Organization’s (IMO’s) Sulphur 2020 vision estimates that the capping standards for sulphur content in ship’s fuel will lead to a 77% drop in overall sulphur oxide emissions from the ships annual reduction of 8.5 million tonnes of SOx.
    • Since sulphur-light fuel can be very expensive, it allowed ships to install exhaust scrubbers that use high-volume, high-speed, water spray to absorb pollutants from the exhaust.
    • The IMO adopted the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI in 2008 that regulates the prevention of air pollution from ships and prohibits deliberate emissions of ozone-depleting substances such as sulphur oxides and nitrous oxides.


    (Image Courtesy: IMO)

    Issues with Exhaust Scrubbers

    • Both kinds of scrubbers have led to the dumping of 10 gigatons of scrubber wastewater containing dangerous pollutants and toxic chemicals, including carcinogenic hydrocarbons.
    • This has endangered sensitive marine ecosystems along the most popular sea routes.
    • Alien species get introduced from one place to another. Sometimes these alien species are invasive and thereby hampering the ecological diversity of the area where they are introduced.
    • It threatens human health through seafood consumption. 


    • At the time of adopting the new norms, it was hoped that more ships would get fitted with closed-loop scrubber systems. But, both types of scrubbers are increasing water pollution.
    • It is clear that air pollution can not be reduced at the cost of water pollution. Thus, there can be some best ways to reduce water pollution from ships such as:
      • Making necessary and stringent laws for enforcement agencies, for example, UNCLOS, MARPOL etc.
      • Awareness among ship owners, operators etc. to minimize water pollution.
      • Polluter pays principle should be brought into more use to deter any violations.
    • As India embarks on its Sagarmala programme, it needs to ensure ships are fitted with closed-loop scrubbers to prevent water pollution
      • The Sagarmala programme is a port-led development programme that seeks to improve infrastructure development across the coastline.

    International Maritime Organization (IMO)

    • It was established in 1948.
    • Headquarters at London, United Kingdom.
    • It is a specialized agency of the United Nations. 
    • IMO currently has 174 Member States and three Associate Members.
    • India (joined in 1959) is a member state.
    • IMO is the global standard-setting authority for the safety, security and environmental performance of international shipping. 
    • Its main role is to create a regulatory framework for the shipping industry that is fair and effective, universally adopted and universally implemented.

    International Convention for the Prevention of Pollution from Ships (MARPOL)

    • It is the main international convention covering the prevention of pollution of the marine environment by ships from operational or accidental causes.
    • It was adopted on 2 November 1973 at IMO.
    • The Convention includes regulations aimed at preventing and minimizing pollution from ships – both accidental pollution and that from routine operations.
    • All ships flagged under countries that are signatories to MARPOL are subject to its requirements, regardless of where they sail and member nations are responsible for vessels registered on their national ship registry.

    IMO 2020 (Sulphur 2020 vision)

    • On 1 January 2020, a new limit on the sulphur content in the fuel oil used onboard ships came into force, marking a significant milestone to improve air quality, preserve the environment and protect human health.
    • The rule limits the sulphur in the fuel oil used onboard ships operating outside designated emission control areas to 0.50% m/m (mass by mass) – a significant reduction from the previous limit of 3.5%. 
    • Within specifically designated emission control areas the limits were already stricter (0.10%). 
    • This new limit was made compulsory following an amendment to Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL).

    Source: TH