Trans RINA, Vol 152, Part A4, Intl J Maritime Eng, Oct-Dec 2010 DISCUSSION
LIFE-CYCLE CO2 EMISSIONS OF BULK CARRIERS: A COMPARATIVE STUDY
G A Gratsos, Hellenic Chamber of Shipping, Greece H N Psaraftis, Technical University of Athens, Greece P Zachariadis, Atlantic Bulk Carriers Management Ltd., Greece
(Vol 152 Part A3 2010)
COMMENT N Mikelis, IMO, UK
The authors are to be thanked and congratulated for pursuing their efforts towards a holistic assessment and comparison of ships built in accordance with minimum classification rules, and ships built to more robust designs incorporating corrosion margins commensurate to longer operating life. Having concluded in their earlier work that the robust ship, compared to the minimum scantlings’ ship, is economically advantageous over its life time, in this paper the authors compare the carbon footprint of the robust ship against the ship built to current minimum class rule requirements.
The paper contributes a reasoned methodology and useful data to the debate that is taking place in the context of rational Goal Based Standards. It is hoped that the paper will generate further debate which should eventually lead to generally accepted conclusions on meaningful minimum design and standards.
classification rule
The writer wishes to bring the authors’ attention to one wrong assumption, one error and one omission they have made in the way they have accounted for ship recycling in their analysis. Although the magnitude of the resultant error is small enough not to affect the conclusions reached in the paper, it is nevertheless better to discuss these issues here so that possible future applications of the authors’ methodology may account properly of the ship recycling phase of a ship’s life cycle.
The authors have assumed (see section 5.7) that steel produced from ship breaking in the major ship recycling centres in India and Bangladesh is exported to industrial centres, such as Japan, Korea, or China. In Tables 5 and 6, the authors account for CO2 emissions from the transport of the recycled steel from the recycling States to these major industrial centres. In fact steel produced from ship breaking in the recycling centres of South Asia is not exported but
construction industries (buildings, analysis should therefore have assumed that
instead is used in the domestic bridges, etc). The the
production of steel from ship breaking simply reduces a country’s needs for imports of scrap steel and steel billets for cold and hot re-rolling (and on some occasions may also reduce the imports of iron ore for smelting).
This brings us to the error in the paper’s accounting of CO2 emissions from transport relating to ship recycling. As noted above, if the ship recycling countries did not produce steel from ship breaking, then these countries would have to import equivalent quantities of scrap steel, or steel billets, or iron ore, in order to satisfy the needs of their construction industries. The more steel that is being obtained from ship breaking, the less steel (or scrap, or iron ore) has to be imported. It should therefore follow that the CO2 emissions from transport relating to ship recycling in Tables 5 and 6 of the paper should in fact be accounted as credits and not as debits to the total. In other words, Ship A, in the 60 year super-cycle, yields more steel for ship recycling (greater lightship), and consequently results in fewer emissions from the transport of fewer raw materials.
Finally, the authors may wish to include in their methodology one additional consideration for the recycling phase. The production of re-rolled steel (i.e. steel from ship recycling) leads to lesser CO2 emissions than the production of new steel from smelting of iron ore. This additional consideration would yield another credit for Ship A in Tables 3 and 4. It has to be noted however that this credit would be much smaller in value than the debit arising from the emissions from steel fabrication (i.e. new steel that would be needed if the recycled steel was not available). Again, this is a secondary contribution whose inclusion in the analysis would not change this excellent paper’s conclusions.
J Kokarakis, Bureau Veritas, Greece
The authors are to be congratulated for an excellent application of Life Cycle Analysis (LCA) applied on a ship, attempts to quantify the full range of environmental impacts associated with the vessel by considering all inputs of resources and materials and all outputs of wastes and pollution at each stage of the ship's life. In their work they consider (for Handymax and Panamax sizes) a design complying with the CSR rules (Ship A) and another somewhat enhanced design with heavier scantlings (Ship B). Key assumption is that the lifetimes of the rule-compliant and the enhanced-scantlings design are respectively 20 and 30 years. independently of the
validity of the
Nevertheless, lifetime ratio
between the two designs it is a fact that the more robust ship will be subject to reduced repairs and will be available more time for carrying cargo.
Table below
reflects the CO2 emissions in a percentage form for the two sizes considered:
© 2010: The Royal Institution of Naval Architects
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