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  • i Anodes, Shipping & Fisheries

    Emission estimates for diffuse sources Netherlands Emission Inventory

    Sacrificial anodes,

    merchant shipping and

    fisheries

    Version dated June 2008

    NETHERLANDS NATIONAL WATER BOARD - WATER UNIT in cooperation with DELTARES and TNO

  • ii Anodes, Shipping & Fisheries

    Table of Contents

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    1 Introduction and scope 11

    2 Description of emission source 21 2.1 Causes 21 2.1.1 Passive protection by means of sacrificial anodes 21 2.1.2 Active protection by means of impressed current 23 2.1.3 Ballast tanks 24 2.2 Measures 25

    3 Explanation of calculation method 31 3.1 Exterior of vessel 31 3.2 Wet surface area 32 3.2.1 Calculation of surface areas based on volume 34 3.2.2 Correction for incomplete draught 35 3.3 Corrosion rate 36 3.3.1 Emissions at sail 38 3.4 Interior of vessel 39

    4 Activity Rates 41 4.1 Assessment using statistical data 41 4.2 Interior of vessel 43 4.3 Time series, 1990-present 44 4.4 Time series, present-2027 44 4.5 Annual data setting 46

    5 Description of emission pathways to water 58

    6 Emission factors 61 6.1 Emission factors 61 6.2 Application percentages 62 6.3 Time series, 1990-present 62 6.4 Annual data setting 62

    7 Emissions calculated 71 7.1 Emission figures 2004 71 7.2 Emissions 1990-2006 71 7.3 Emissions forecast, 2009-2027 73

    8 Comments and changes in regard to previous version 85 8.1 Difference in figures due to mathematical errors 85

    9 Accuracy and indicated subjects for improvement 91 9.1 Most significant areas for improvement 91

    10 Spatial allocation 101 10.1 Seagoing vessels and fishing vessels on NCP 101 10.2 Seagoing vessels in Dutch territory 103 10.3 Fishing vessels in ports 104

  • iii Anodes, Shipping & Fisheries

    11 References 111

  • 11 Anodes, Shipping & Fisheries

    1 Introduction and scope

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    The source of the emissions is the anode material placed on the exterior

    and interior (in the ballast tanks) of seagoing merchant vessels and

    fishing vessels for the purpose of cathodic protection of metal surfaces.

    In the National Emission Inventory, this emission is assigned to the

    governmental target sector Transport. The emissions in question are

    zinc, aluminium and cadmium. Cadmium is present as a contaminant in

    the zinc, and is released when zinc anodes decay.

    This report is based on a previous quantification of emissions of anodes

    in shipping and fisheries for the Dutch Continental Shelf (NCP) and in

    ports conducted for the Traffic and Transport Advisory Service (AVV)

    under the EMS (Emission Inventory and Monitoring for the Shipping

    Sector). The quantification in this report can be considered to be an

    update of two EMS protocols:

    - EMS protocol for Emissions by Shipping and Fisheries: Anodes

    on ships on the NCP (Kuiper, 2003a)

    - EMS protocol for Emissions by Shipping and Fisheries: Anodes

    on ships in ports (Kuiper, 2003b)

    Here, the quantification of emissions for NCP and ports is integrated

    into a single report. The method of quantification of the two types of

    emissions is different, however, and consequently this distinction will be

    referenced frequently throughout this report.

  • 12 Anodes, Shipping & Fisheries

    This quantification implements a number of recommendations for

    improvement of emissions assessment from the protocols listed above,

    and also incorporates a few new insights. The most significant changes

    in reference to the protocols are:

    - Calculation of the Wet Surface Area (WSA) is improved, with a

    WSA computed for each individual ship in Dutch waters, taking

    partial loading of the ship into account;

    - A traffic and transport database based on the Lloyds traffic file

    has been created for the NCP, which, in combination of the

    WSA per ship, was used to compute the total average WSA

    present in Dutch waters;

    - Emissions from floating tank cooling1 appear to play a much

    smaller role than described in the protocols. Floating tank

    cooling is a cooling system used primarily in inland waterway

    shipping and possibly a few smaller seagoing vessels. Larger

    seagoing vessels have pipe or plate cooling systems.

    Consequently, emissions from floating tank cooling are not

    reported separately in this report;

    - Along with historical development in emissions, this report

    provides a forecast of emissions up to the year 2027;

    - The emissions are spatially allocated by body of water identified

    in the Water Framework Directive. This data is provided as a

    separate database.

    1 Cooling system for ship engines involving a steel tank welded to the hull, in contact with the

    water, and containing a bundle of thin, corrosion-proof pipes. In some versions, the tank is an

    inverted box on the bottom of the ship with an opening in the bottom. The tank contains a

    heat exchanger consisting of a package of many thin tubes that come into contact with the

    outside water on all sides.

  • 21 Anodes, Shipping & Fisheries

    2 Description of emission source

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    2.1 Causes

    Ships are coated to prevent corrosion. This protective layer, however, is

    not sufficient to fully protect the ship from corrosion. For this reason, as

    well as to protect the uncoated sections of a ship (screw, damage, etc.)

    and ensure that the ship remains protected as the coating deteriorates,

    cathodic protection is used.

    If two metals are electrically

    connected in an electrolyte

    (such as seawater), the

    electrons of a base metal

    will flow to another, more

    noble metal. This is due to

    the difference in electrical

    potential. The more noble

    metal is referred to as the

    "cathode" and the other as

    the "anode." As the anode

    supplies electrons to the cathode, it gradually dissolves into ions, with

    the result that the cathode becomes negatively polarised and thus

    protected against corrosion. See figure 1. Cathodic protection can be

    classified as passive or active. This is explained in more detail in the

    following subsections.

    2.1.1 Passive protection by means of sacrificial anodes

    Passive cathodic protection of a ship involves the use of "sacrificial

    anodes". As already indicated, these sacrificial anodes must be of a

    metal that is less noble (more base) than the metal to be protected. The

    two metals used as anodes in shipbuilding are zinc and aluminium.

    Table 1 shows the various metals in order of nobility. The effectiveness

    of the anode material in seawater is determined by the composition of

    the alloy.

    Because the anodes dissolve in the seawater, the blocks must be

    replaced at regular intervals. On average, the blocks are replaced every

    two to two-and-a-half years, when approximately 15% of the original

    weight remains. For fishing vessels, the ratios are different. A fishing

    vessel goes into dry-dock every year, and so the blocks are replaced

    every year, when some 30% of the original weight remains.

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . figure 1 Functioning anode

  • 22 Anodes, Shipping & Fisheries

    Zinc anode

    The most commonly material used for cathodic protection of seagoing

    vessels is zinc. The electrical capacity (also indicated by the symbol , see chapter 4.1) of a zinc anode in seawater is 780 Ah/kg (Ampere per

    hour per kg of zinc anode). This is a function of the amount of valence

    electrons that can be moved from the zinc to the less noble metal per

    hour. If the amount of valence electrons the metal to be protected

    gives off under the influence of seawater is known, the rate at which

    the zinc anode dissolves can be calculated.

    The zinc anodes installed in ships are generally designed for a lifetime

    of between 1 and 3 years.

    Aluminium anode

    Aluminium is being used as an anode material more and more

    frequently. The electrical capacity of an aluminium anode in seawater is

    2,600 Ah/kg. Aluminium anodes perform better than the zinc anodes

    (2,600 valence electrons per hour per kilogram versus 780 for zinc),

    and as such require fewer to achieve the same effect. Although

    aluminium is a more expensive material than zinc, the end cost of

    aluminium anodes is less because they require 3.33 times less material.

    Another significant environmental advantage is that the aluminium

    alloys used do not contain cadmium, unlike the zinc alloys used (and

    prescribed by standardization; see chapter 3.2).

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    table 1

    Metals in order of nobility

    Nobility of various metals

    Metal Symbol

    Potassium K

    Sodium Na

    Calcium Ca

    Magnesium Mg

    A