Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 13 replies
  • Subscribers 14 subscribers
  • Views 1385 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Pollution from ships vs cars

Alasdair Anderson
In a recent article (E&T Feb - Hybrid Ships - https://eandt.theiet.org/content/articles/2019/01/hybrid-ships-take-to-the-high-seas/) it is stated that "According to figures originally published in the Guardian in 2009, one giant container ship can emit almost the same amount of cancer- and asthma-causing chemicals as 50 million cars, and around 50,000 premature deaths in Europe have been attributed to international shipping".  This seems a bit much to me, since there are only about 30 million cars in the whole of the UK. Can one container ship with say two diesel engines of 40,000 hp each produce the equivalent pollutants of the exhausts of 50 million cars with a combined engine power of perhaps around 2.5 billion hp? (Note that I am ignoring issues such as the 15,000-20,000 lorries kept off the road). As this information was originally published in the Guardian, does anyone know how the journalists gather and, more importantly, validate their statements?

Alasdair
  • 0
    Hi Alasdair,  as a very quick thought without crunching any numbers. Are they assuming that a ship lasts for many car lifetimes and multiplying from that assumption?
  • 0
    Roy,

    Good thought and not one that I had considered, perhaps because I know too much through working in the industry, as our last car went to the great scrapyard in the sky at the beginning of this year, first registered in 1998, so it lasted 21 years, compared to the normal lifespan of a ship which is 25 years, so perhaps not that much different.

    Alasdair
  • 0
    Have they also allowed for cars spending 90% of the time parked?  A ship will spend day and night sailing back and forth between ports.
  • 0

    Simon Barker:

    Have they also allowed for cars spending 90% of the time parked?  A ship will spend day and night sailing back and forth between ports.




    If they have it means they still consider a ship equivalent to 5 million cars running continuously. Ships still spend time in port, probably 10% of their time for a container ship, and their engines are subject to strict emission requirements which can't be fudged, unlike some car results. I am still curious about how the journalists have validated their information.

    Alasdair

  • Former Community Member
    0 Former Community Member
    I think we need to understand some minimal assumptions:


    average life of a large container cargo ship (30 years?) versus a life of a car (15 years?)

    average annual fuel consumption of a continuously used cargo ship versus average annual consumption of a domestic/travel to work diesel and petrol car

    CO2e conversion factor for dirty Marine fuel oil versus CO2e conversion factor for diesel and petrol


    If we don't know these basic assumptions then no reasonable comparison can be made.
  • 0
    There are no assumptions stated in the E&T article, presumably because there are no assumptions stated by the Guardian in the original article being quoted. Please note the reference is to cancer- and asthma-causing chemicals so it is not the CO2 that is in question. It is probably the NOX and similar compounds. If we assume that NOX is absent from petrol (spark ignition) engines but a product of diesel (compression ignition) engines then I guess only counting the diesel cars is valid. The figures show that 40% of the cars in the UK are diesel so that would mean out of 50 million cars, 20 million would be diesel.

    The lifespan of a ship is 25 years - it is unusual for a ship to be economically viable beyond its fifth special survey (every five years) due to the cost of rectifying the maintenance and corrosions issues to ensure another five years of life, though some only last 20 years.

    If you want the fuel consumption of one of these container ships I reckon you would be looking at around 1000 tonnes per day while at sea (call it a million litres). This would equate to one million cars driving around ten miles each (or to take the number of diesel cars mentioned above, 20 million diesel cars driving around half a mile each - an annual mileage of less than 200 miles).

    Even if you work on the total lifetime emissions you are not going to alter this significantly to get it anywhere near the normal annual mileage. Perhaps you can see why I am struggling to accept the comparison.

    Alasdair
  • Former Community Member
    0 Former Community Member
    Ships emissions can be higher than expected if the crew use the wrong fuel; https://www.theguardian.com/world/2018/nov/26/cruise-ship-captain-fined-100000-for-using-dirty-fuel 

    Unlike cars where the fuel quality is tightly controlled. 

    And of course, ships have other emissions that cause environmental harm
    https://www.theguardian.com/environment/2016/dec/02/the-40m-magic-pipe-princess-cruises-given-record-fine-for-dumping-oil-at-sea
    https://www.theguardian.com/environment/2018/oct/22/po-cruise-ship-dumped-27000-litres-of-waste-on-great-barrier-reef-senate-hears


    Shipping needs to clean up, quickly
  • 0
    As far as I can see the 50,000 deaths figure comes from this report http://ceeh.dk/CEEH_Reports/Report_3/CEEH_Scientific_Report3.pdf. I have no way of V&V ing it as it is well outside of my competence to try and do so. I can say that, currently, the plume from engine exhausts of  Cruise Ships,  berthed in Southampton, extends over my house as they run their engines whilst alongside. This is set to change when the port gets better quayside electricity supplies - or so I am led to believe-. That can't come too soon as far asI am concerned
  • 0
    This is one for Tim Harford of More or Less, he may even have covered it. But the emissions from shipping is now a hot topic in that industry as people have woken up to it, see here https://www.intercargo.org/topics/emissions/. Most of the heavy materials in the World are shipped as Dry Bulk. Ships burn stuff they call "bunkers", nasty low grade sulphurous oil.
  • 0
    BBC Radio 4 More or Less investigated the origin of the claim in a programme from October 2017.  It is available as a podcast here: https://www.bbc.co.uk/sounds/play/w3cstyfd


    The calculation only relates to the amount of sulphur in the fuel and assumes the ship uses the worst possible fuel (allowed in 2009 in heavy fuel oil) and the cars use the best possible fuel!

Community Rules & Guidelines