Sacrificial Anodes, Merchant Shipping

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

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1 Introduction and scope 1–1

2 Description of emission source 2–1 2.1 Causes 2–1 2.1.1 Passive protection by means of sacrificial anodes 2–1 2.1.2 Active protection by means of impressed current 2–3 2.1.3 Ballast tanks 2–4 2.2 Measures 2–5

3 Explanation of calculation method 3–1 3.1 Exterior of vessel 3–1 3.2 Wet surface area 3–2 3.2.1 Calculation of surface areas based on volume 3–4 3.2.2 Correction for incomplete draught 3–5 3.3 Corrosion rate 3–6 3.3.1 Emissions at sail 3–8 3.4 Interior of vessel 3–9

4 Activity Rates 4–1 4.1 Assessment using statistical data 4–1 4.2 Interior of vessel 4–3 4.3 Time series, 1990-present 4–4 4.4 Time series, present-2027 4–4 4.5 Annual data setting 4–6

5 Description of emission pathways to water 5–8

6 Emission factors 6–1 6.1 Emission factors 6–1 6.2 Application percentages 6–2 6.3 Time series, 1990-present 6–2 6.4 Annual data setting 6–2

7 Emissions calculated 7–1 7.1 Emission figures 2004 7–1 7.2 Emissions 1990-2006 7–1 7.3 Emissions forecast, 2009-2027 7–3

8 Comments and changes in regard to previous version 8–5 8.1 Difference in figures due to mathematical errors 8–5

9 Accuracy and indicated subjects for improvement 9–1 9.1 Most significant areas for improvement 9–1

10 Spatial allocation 10–1 10.1 Seagoing vessels and fishing vessels on NCP 10–1 10.2 Seagoing vessels in Dutch territory 10–3 10.3 Fishing vessels in ports 10–4

iii Anodes, Shipping & Fisheries

11 References 11–1

1–1 Anodes, Shipping & Fisheries

1 Introduction and scope

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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.


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.


2 Description of emission source

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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


Zinc anode

The most commonly material used for cathodic protection of seagoing

vessels is zinc. The electrical capacity (also indicated by the symbol ε, 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

Aluminium Al

Zinc Zn

Iron Fe

Chromium Cr

Nickel Ni

Tin Sn

Lead Pb

Copper Cu

Mercury Hg

Silver Ag

Platinum Pt

Gold Au

Nobility of various metals


2.1.2 Active protection by means of impressed current

In addition to passive protection, active cathodic protection is an

increasingly common method of protection. The impressed current (IC)

system moves potentials to protect the metal.

An IC system uses a transformer, an adjustable rectifier as a power

source and inert, or "non-consumable", anodes. The adjustable rectifier

can be set so that the connected anode(s) provide exactly the

protective current to provide the desired protection potential. See

figure 2.

Theoretically, an IC system could be used to protect the entire exterior

of a vessel, but in practice this system is often used in combination with

passive anodes. The parts of the vessel fitted with passive anodes are

the bow thruster tunnel, the screw and the rudder. These parts require

a higher level of protection because they use unfinished metal (screw),

the coating on these parts has a higher breakdown factor, and the

speed of the water that passes along these parts is higher than at other

parts of the hull. IC systems are not used in ballast tanks, because the

generation of hydrogen gas (H2) constitutes a risk of explosion,

certainly in combination with the electrical system.

Because IC systems do not release metal ions into the water, this is the

most environmentally friendly cathodic protection method. The system

also allows online measurement of the state of the coating, and reduces

organism growth, thereby contributing to reduced fuel use.

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figure 2

Operation and placement of

impressed current system


2.1.3 Ballast tanks

Protection of the ballast tank of a vessel is more complex than the

protection of the hull, for a number of reasons:

• While the ballast tank may be a tank solely used for ballast water,

in many cases the cargo area is also used as a ballast tank, and this

causes the anodes to become soiled and no longer function

properly

• The ballast tank is not always in ballast

• The ballast tank is difficult to reach and consequently difficult to

check;

• The form and structure of a ballast tank (many crossbeams, holes,

etc.) require more anode material to keep the less accessible

locations (the places not easily reached by cathodic protection)

protected

Ballast tanks are

constructed primarily of

aluminium, presumably

due to the longer lifetime

of aluminium at the same

weight. As indicated

above, the anodes in the

ballast tank are difficult to

replace. See figure 3 for

the placement of anodes

in the ballast tanks.

For ships with explosive

cargo (oil, gas, etc.),

ballast tanks are subject

to special requirements

governing the placement

and type of anode

material used:

• Aluminium may not

be used in ballast

tanks for ships

transporting flammable cargo. Anodes coming loose and falling can

cause sparks;

• Likewise, IC systems cannot be used due to the risk of

fire/explosion due to the formation of hydrogen gas (H2) in

combination with the electrical system.

Consequently, in certain cases zinc is used for the anodes mounted

higher in the ballast tank (combining zinc and aluminium anodes is

permitted).

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

figure 3

Placement of sacrificial anodes in

ballast tanks


The average lifetime of anodes in ballast tanks is calculated at 4-6

years.

2.2 Measures

Government policy is focused on reducing the concentrations of toxic substances to target values. To do this, emissions of many of these substances must be reduced. Between 1985 and 1995, copper impact on surface water had to be reduced 50%, and cadmium 70% (North Sea Action Plan). These goals were met and exceeded. For cadmium, a priority substance, minimization of discharge is a goal. Zinc, copper and cadmium are of significance for fresh surface water sources, primarily in relation to the contamination of the sediments.

Although cadmium levels in zinc have been lowered in recent years

(0.001-0.005%), this reduction was not and is not in effect for anode

material, which uses higher contents (NEN, 1996; DNV, 1993; US-

Military specification, 1987) because of the quality requirements set on

the anode material (relating to the composition of the alloy). The issue

is that the anodes must corrode evenly, which requires cadmium

contents between 0.025 and 0.07 percent. Higher contents may also be

found in anodes from less scrupulous suppliers, but there are no figures

available on this.

The emission of zinc and cadmium from anodes was addressed in a

1996 OSPAR report (OSPAR, 1992), which recommended monitoring

emissions. If an increase in the use of zinc is observed, then

supplemental measures should be considered in regard to this cadmium

emission.

The fishery sector has seen a large-scale shift towards replacing anodes

with IC systems. One important reason behind this is that anodes on

the ship's shell increase resistance when sailing, resulting in lower

sailing speed and higher fuel consumption. Since 2000, the acquisition

of IC systems in the fishery sector has been included in the VAMIL2

regulations (a financial environmental regulation system mandated by

the Ministry of Housing, Spatial Planning & the Environment).

2 VAMIL stands for "voluntary amortization of environmental investment." The VAMIL was

established by the Ministry of Housing, Spatial Planning & the Environment.


3 Explanation of calculation method

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The calculation system used is addressed in general terms in the

"method" section. Chapters 5, 6 and 7 cover the activity rates, the

emission factors and the emissions.

3.1 Exterior of vessel

This chapter addresses the method of calculation used to arrive at the

emission assessment. Emissions are ultimately calculated as the product

of an activity rate and an emission factor.

emission = activity rate * emission factor

The emission is expressed in tonnes per year.

The activity rate is the wet surface area (WSA) (in m2) on average

present in Dutch waters at any given time. The total ship area is the

product of the total number of ships found in the NCP and the wet

surface of a seagoing vessel, taking type and tonnage into account. The

traffic and transport database of the risk model SAMSON (Glansdorp,

Van der Tak, 1993) was used to calculate the number of ships sailing

on the NCP and the calculation of the underwater ship area. The basic

data for this database were derived from Lloyds for the year 2000. For

other years, a comparison with figures from Statistics Netherlands of

ship calls at Dutch ports was used.

In the calculations, the activity rate for different years was estimated

taking into account the trend in wet surface area and application rates

of the various technologies of cathodic protection.-{}-

ARx,c = ARy x APPx,c x TRENDxy

Where:

ARx,c = activity rate of technology (t) in year (x)

ARy = total of activity rates in base year (y)

APPx,c = application fraction of technology (t) in year (x)

TRENDxy = trend factor of AR in year x in relation to base

year (y)

The emission factor is the leaching rate of aluminium and zinc,

expressed here in µg cm-2 day-1. These leaching rates used in the

calculations are taken from the report Uitloging anodemateriaal van zeeschepen, produced by BECO for RIZA, the Netherlands Centre for

Water Management (Willems, 2003; see chapter 4.4).


3.2 Wet surface area

If the dimensions of the ship are known, the wet ship area can be

calculated by any of several different methods:

• The Denny-Mumford equation (Man-Diesel, 2002; Kuiper,

2003a,b) was derived by Mumford at the end of the 19th

century using tests of ship models in Denny's experimental

(1750 m3) water tank in Scotland. In Denny-Mumford, the wet

ship area is calculated from the length, depth and a block

coefficient (the ratio of the actual volume of the hull and the

product of length x width x depth)

• The Komsi comparison (Koivisto, 2003; OECD, 2005) based on

measurements of ships in Finland

• The Holtrop-Mennen equation (Holtrop, 1977) is the most

recent method for determining the wet ship area. This formula

is based on the same type of measurements as Denny-

Mumford, factoring in additional insights from hydrological

theory. The Holtrop-Mennen coefficients are obtained through

regression analysis of MARIN model tests

• The ratio from Van Hattum et al. (2002) is more of a first order

approach to the wet ship area, based on a simplified ship

model.

In this study, the methods are compared for the group of Bulk Carriers

in the Lloyds register. The results of the comparison are shown in the

figure below. The volume of all ship's enclosed spaces is expressed in

GT (gross tonnage) to the power of two-thirds.

Bulkers: GT^2/3 vs. oppervlak

0

5000

10000

15000

20000

25000

30000

35000

0 500 1000 1500 2000 2500 3000 3500

grootte^2/3 (GT)

op

perv

lak (

m2)

Denny Mumford

Van Hattum

Komsi

Holtrop-Mennen

Average surface % of Holtrop

Mennen

Denny-Mumford 9072 98%

Van Hattum 7735 84%

Komsi 9250 100%

Holtrop-Mennen 9223 100%

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 4 Comparison of the results of different methods of establishing wet ship area for the group bulk carriers

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2 Comparison of the results of different methods of establishing wet ship area


For bulk carriers, the results using Denny-Mumford, Holtrop-Mennen

and Komsi are very similar. The Van Hattum model produces different

results. Because Holtrop-Mennen seems to be the most theoretically

sound, the most recent and in keeping with Komsi and Denny-

Mumford, this model is recommended.

calculates the wet ship area as follows:

WSA = L(2D+W) x sqrt(CM) x (0.530+0.632CB-0.360(CM-0.5)-

0.00135L/D)

Where:

WSAmax : wet ship area at design draught

D : design draught of the ship

L : length of the ship measured between midship perpendiculars

W : width of ship at widest point

CM : surface area coefficient of the largest rib: the transverse

section measured at the widest rib of the ship divided by the

surface area defined by W x D at the largest rib

CB : the block coefficient of the ship: volume of the ship divided by

the block defined by L x W x D

Values for CM and CB for the various vessel types are shown in table 3

(Man-Diesel, 2002).

Vessel type CB CM

Barge 0,9 0,98

Bulk carrier 0,85 0,98

Tanker 0,85 0,98

General cargo 0,75 0,95

Container ship 0,7 0,95

Ferry 0,7 0,95

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Equation 1 The Holtrop-Mennen

compariso

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 3 Coefficients for use in Holtrop-Mennen equation


3.2.1 Calculation of surface areas based on volume

The current standard of ship measurement is gross tonnage (GT3).

A ship twice as long is generally also approximately twice as wide and

twice as deep. The relationship between volume and vessel length is

therefore a third exponent. The relationship between surfaces and

length is a second exponent. Taken together, all this suggests a

relationship between surface and vessel volume to the power of two-

thirds:

WSAmax ~ Volume2/3

Where WSAmax is the wet surface area at design draught.

Upon further elaboration, this is also shown to apply for most vessel

types across a very wide range of vessel sizes. The wet surface can

therefore be expressed as a function of ship size in GT:

WSAmax = C GT2/3

The value of the constant C differs from vessel type to vessel type.

Table 2 presents an overview of the results.

3 Ship size is often expressed in gross tonnage (GT). This gross tonnage is calculated as K * V,

where V is the gross volume of the ship and K a correction, calculated as 0.2 + 0.0210logV .


type no. Vessel types (Samson description

2006)

surface area

1 Tankers (single and double-walled) WSAmax = 9,62

GT2/3

2 Chemical tankers (single and

double-walled)

LPG tankers

WSAmax = 9,35

GT2/3

2a LNG tankers WSAmax = 7,47

GT2/3

3 Bulk carriers WSAmax = 9,70

GT2/3

4 Container ships WSAmax = 8,57

GT2/3

5 General dry cargo WSAmax = 8,76

GT2/3

6 Passenger ships and ferryboats WSAmax = 5,20

GT2/3

6a Unitised Ro-ro WSAmax = 6,60

GT2/3

7 Reefers WSAmax = 10,2

GT2/3

8, 9, 0 Other; supply ships; non-

commercial ships

WSAmax = 8,40

GT2/3

Fishing vessels WSAmax = 8,63

GT2/3

3.2.2 Correction for incomplete draught

The wet ship areas above are wet areas when fully loaded, which also

puts the ship at design draught. If draught is not full, actual wet area

can be calculated from the actual wet area and the percentage draught

(%T)4:

4 Derivative; the average ratio of maximum draught (Tmax) and vessel

width (B) is 1:2.6. The maximum wet area can initially be estimated as

WSAmax = constant * (2Tmax + )B = constant * (2Tmax + 2.6Tmax) =

constant * 4.6Tmax. Tmax = WSAmax/(constant * 4.6)

In the same way, the actual wet ship area (WSA) is equal to constant *

(2Tmax * %T + B) = constant * (2Tmax * %T + 2.6Tmax) = constant * Tmax

(2%T +2.6).

Combining the two comparisons results in WSA = WSAmax (2 * %T

+2.6)/4.6

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 4 calculation of wet ship areas when fully loaded, for each vessel type


WSA = WSAmax (2 * %T +2,6)/4,6

Estimates of relative draught for the various ship types upon arrival and

departure are obtained from MARIN (Van der Tak, 2006).

3.3 Corrosion rate

The draft of the "anode plan" or cathodic protection plan (CB plan) for

the ship takes into account factors such as susceptibility to corrosion of

the type of vessel and the individual parts of the ship. The areas around

the screw and on the rudder, for example, have more anodes placed on

them than on the rest of the ship (see figure 5).

The draft assumes recommended electrical current density per m2 (ic) to

prevent corrosion (Norsok, 1997; DNV, 1993; British Standard, 1991).

The number of anodes to be installed is derived from these current

densities. For untreated steel in North Sea water, electrical current

density must be approximately 85 mA/m2 to prevent corrosion. This

figure applies at a temperature between 5oC and 20oC (fluctuation in

North Sea between 1990 and 1999, with average of 11.8oC) and a

draught between 0 and 30 metres.

The amount of anode material that dissolves in water over a given

period of time (such as one year) can be calculated from the voltage

density and the electrical capacity of the anode material, using

Dwight's equation. This equation is:

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

Equation 2

Correction for incomplete draught

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

Figure 5 Anodes on the rudder and around the screw


( )( )ma

u

tiAm

c

=∗

∗∗∗

ε1000/

Where:

Parameter Unit Description

M Kg Amount of anode material that corrodes in time t

A m2 Wet surface

ic mA/m2 Required electrical current density

t Hours Time spent in water, in hours

−{}−ε Ah/kg Electrical capacity of anode in seawater

u Factor Utilization factor; for emission calculations, u=1

am Factor

Fraction that anode material (zinc or aluminium) used

represents in relation to total use of anodes (total of zinc and

aluminium anodes)

The electrical capacity of a zinc anode in seawater is 780 Ah/kg

(Ampere-hours per kg of zinc anode) and 2,600 Ah/kg for aluminium

anodes. The utilization factor is used to introduce an extra margin for

the use of anodes. Assuming a given lifetime of two years, a utilization

factor of 0.9 results in a theoretical overcapacity of approximately

10%. For emission calculations, the utilization factor is 1. The factor am

indicates the fraction of zinc or aluminium in relation to the total anode

use in shipping or fisheries.

Table 5 shows the required current densities per component and per

type of vessel (Willems et al., 2003).

Required current density (mAmp/m2)

Hull Screw Rudder Turbine bow thruster

Bulk Carrier 12 700 150 120 700

VLCC (Very Large Crude oil

Carrier) 12 700 150 120 700

Coaster 12 700 250 120 700

Ro/Ro Ferries 12 700 150 120 700

Fishing 18 1000 250 120 700

Supply Vessel 18 1000 250 120 700

Work vessel 40 1400 250 120 700

Ice class vessel 20 1400 250 120 700

Container 12 1400 250 120 700

Reefer 12 700 150 120 700

Destroyer 12 700 150 120 700

Naval vessel 12 700 150 120 700

The table above can be used to calculate the leaching of anode

material. Because the surface area and number of screws, rudders,

turbines and bow thrusters is not known for each vessel type, table 6 is

provided to be used for estimates (Willems et al., 2002). This table

shows the required current density for the hull including what is

necessary to protect the screws, rudders, turbines and bow thrusters.

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

Equation 2 Dwight's equation for the calculation of the number of anodes required on a ship

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 5 Required electrical current density by component of and by type of ship


Required current density (mAmp/m2)

Type of vessel Hull

OBO carrier 15

Tankers 15

Bulk Carrier 15

Container 15

Ro-ro 20

General Cargo 20

Reefer 15

Passenger 20

Work vessels 35

Supply 22

Fishing 24

Equation 2 (Dwight's equation) in combination with the recommended

voltage densities allows calculation of both the number of anodes and

the corrosion rate. Dwight's equation can be used to directly derive the

formula for the corrosion rate in µg/cm2-day, which is:

ratecorrosioni

=

∗ε2400c

3.3.1 Emissions at sail

For corrosion rate, the emission estimate distinguishes between

seagoing vessels, Ro-ro, passenger/ferryboats and fishing vessels

(current density 25 mA/m2). See table 7 (EPA, 1996).

Current density and corrosion rate, vessel exterior

corrosion rate in µµµµg/cm2/day Type of vessel Current density

ic in mA/m2 zinc aluminium

Tankers, bulk carriers,

container ships

15 46 13,3

Ro-ro, supply,

passenger, ferry

20 61,5 17,8

Fishing vessels 25 77 22,2

3.3.2 Emissions in ports

The literature shows that the corrosion rate in port is less than at sail by

a factor of 3-5 (EPA, 12). For this reason, the calculation of the

corrosion rate in ports uses an emission factor reduced by a factor of 4

in comparison to the emission factor at sail. The results of this exercise

are shown in table 8 (EPA, 1996; Kuiper 2003a,b).

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

Table 6 Average required electrical current density for hull, stern and bow thrusters, by type of vessel

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

Equation 3 Equation for the calculation of the corrosion rate of anodes

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

Table 7 Current densities and corrosion rates for anodes on sea vessels


corrosion rate in

µµµµg/cm2/day

Type of vessel Current density

ic in mA/m2

zinc aluminium

Seagoing vessels 3,8 11,5 3,3

Fishing vessels 6,3 19,3 5,6

3.4 Interior of vessel

For the ballast tanks, the same approach is used as for the exterior of

the ship. To do this, the surface area of the interior of the ballast tanks

is estimated, as well as the corrosion rate and the exposure time of the

ballast water. Ballast water is changed offshore, in part to prevent

contamination by exotic organisms. For this reason, the emission takes

place primarily on the NCP.

The total number of ship tonnage on the NCP is known from the

SAMSON database. Table 9 shows the maximum ballast capacity in

Deadweight Tonnage (DWT) (Willems et al., 2003). This allows a

maximum ballast capacity to be calculated, in m3, for each type of

vessel. From this, the internal surface area of the ballast tanks can be

estimated by multiplying the volume by a factor. This factor depends

on the shape of the ballast tank, and varies from 1 to 5. This report

uses an average factor of 2.5.

Type of vessel Ballast water capacity in % of DWT

OBO carriers 30

Tankers > 80.000 30

Tankers > 80.000 20

Chemical tankers 20

LNG/LPG tankers 25 – 30

Bulk carriers 20

Container 30

Ro-ro 20 – 25

Reefer 10 - 15

General Cargo 10 – 15

Passengers 10 -15

Work vessels 10 -15

Supply 10 -15

Fishing vessel 10 -15

The corrosion rate in µg/cm2-dag can be calculated using equation 3.

According to a statement in the BECO report, an average current

density of 90 mA/m2 can be maintained for ic (this varies from 86 to

120 mA/m2, depending on the type and shape of the ballast tank). For

the anodes in the ballast tanks, the corrosion rate is:

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

Table 8 Current densities and corrosion rates for anodes on sea vessels in port

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

Table 9 Activity rate factor, exterior of ships, at any moment, for year 2000


Corrosion rate in

µµµµg/cm2/day

Current

density ic in

mA/m2 zinc aluminium

All vessels 90 276 79,8

For the fraction of the time that ballast water is in the ballast tank,

BECO estimates a factor of 0.35. An estimate of the discharge on the

NCP is made as follows. In practice, not all ships will change ballast water

on the NCP. It is assumed that of all ships on the NCP, a maximum of

50% sail to ports in the Netherlands, while the other half sailed from

Dutch ports. A few will not call in the Netherlands at all. Consequently, it is

assumed that a maximum of 50% of the ships change their ballast water

on the NCP (these being the ships that sailed to Dutch ports in ballast to

pick up cargo).

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

Table 10 Corrosion rate of anodes in ballast tanks


4 Activity Rates

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

4.1 Assessment using statistical data

The method for assessment of the activity rates is taken directly from

the previous versions of this protocol (Kuiper, 2003). This means that

the wet surfaces are estimated by means of the number of vessels

according to the Statistics Netherlands, multiplied by the average

surface per ship. The wet surface area in 2004 was calculated in detail

from the geographic files. See chapter 10 for the derivation of this

figure. The result is considered determinated for the base year in

question. This means that all other emissions are scaled against this

result. Here, too, the number of vessels is taken from Statistics

Netherlands. This revealed that minor changes in the files have been

introduced since 2003.

NCP

Seagoing vessels

2004 = 735709

NCP

Fishing vessels

2000 = 65551

Year

Number AR(m2) Trend Number AR(m2) Trend

1990 45920 766976 1.04 639 76716 1.17

1995 44056 735843 1.00 563 67592 1.03

2000 42087 702955 0.96 546 65551 1.00

2004 44048 735709 1.00 473 56787 0.87

2005 43189 721362 0.98 441 52945 0.81

2006 44011 735091 1.00 440 52825 0.81

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

Table 11 Activity rate (AR) for Seagoing Vessels and Fishing Vessels on North Sea


NCP

Seagoing vessels

2004 = 735709

NCP

Fishing vessels

2000 = 65551

Year

Number AR(m2) Trend Number AR(m2) Trend

1990 45920 157792 632284 1,04 639 173677 1,35

1995 44056 151387 606618 1,00 563 153021 1,19

2000 42087 144621 579506 0,96 546 148400 1,15

2004 44048 151360 606508 1,00 473 128559 1,00

2005 43189 148408 594680 0,98 441 119862 0,93

2006 44011 151232 605998 0,99 440 119590 0,93

The figures above are compiled from the totals of the figures for Dutch

seaports. This total is higher than the annual total figure published by

Statistics Netherlands, because a ship may call at multiple ports. The

figures above include all calls. The data goes back to the year 1996. For

years prior to 1996 Statistics Netherlands does not publish online

statistics, so these figures are estimates. The following ports are included: Amsterdam, Delfzijl en Eemshaven,

Dordrecht, Harlingen, IJmuiden, Klundert, Moerdijk, Rotterdam,

Scheveningen, Terneuzen, Vlaardingen, Vlissingen, Zevenbergen and

Zaanstad.

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

Table 12 Activity rate (AR) for Seagoing Vessels and Fishing Vessels on North Sea


4.2 Interior of vessel

The activity rate factor for the ballast tanks is the internal surface area

of the tanks in the ships present on the NCP on average permanently.

The calculation of this surface area assumes that 50% of ships are

transporting ballast water, and change this ballast water on the NCP.

The calculation of the wet surface of ballast tanks is directly related to

the wet surface of the ships.

Vessel type AR

(m2)

Factor

%

WSA ballast

(m2)

Anchored vessel 150421 10 15042

Bulker 79728 20 15946

Chemical 67290 20 13458

Container 107886 25 26971

General Dry Cargo 131388 10 13139

Gas tanker

(LPG/LNG) 14763 25 3691

Miscellaneous 7191 10 719

Ore/Bulk/Oil 5574 25 1394

Oil 73725 25 18431

Pass./Ferry 13153 10 1315

Roll-on/Roll-off (ro-

ro) 70749 20 14150

Tug/supply 3416 10 342

Floating workstation 10423 10 1042

Fishery 56787 18 10222

Total

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

Table 13 Activity rate for seagoing vessels and fishing vessels from ballast tanks in 2004


4.3 Time series, 1990-present

The table below shows the time series for the activity rates for the

internal surface area of the ballast tanks.

Year Trend Seagoing

vessels

AR(m2)

Trend Fishing vessels

AR(m2)

1990 1,04 128874 1,35 11963

1995 1,00 123643 1,19 10540

2000 0,96 118117 1,15 10222

2004 1,00 123620 1,00 8855

2005 0,98 121210 0,93 8256

2006 0,99 123516 0,93 8237

The 2004 figures for the above table were determined using the spatial

allocation database. The other figures were determined based on the

trends in number of seagoing vessels and fishing vessels.

4.4 Time series, present-2027

The trend in the activity rate (wet ship area) is dependent on two

factors: - trends in ship activities - trends in ship size

Ship activities A forecast for trends in ship movements can be based on CPB

scenarios. The scenario document Welvaart en leefomgeving (CPB et

al., 2006) outlines a trend in the quantity of goods stored in the ports.

The trend in ship movement (in tonne-km) is assumed to be directly

related to this stored quantity of goods.

The Global Economy scenario is selected, which entails the assumption

that during the period from 2002 to 2040, shipping activities will more

than double (2% growth per year).

In the same period, the fisheries sector is expected to shrink 50% (2%

per year until 2040).

Trend in vessel size Trends in vessel size are important for tracking the development of

emissions from anodes. Growth in average vessel size means a decrease

in total wet surface (at equal total tonnage), because larger ships have

relatively less surface area than smaller ships. The development of

vessel size per vessel type is based on trends in average vessel size over

the past 20 years. Looking at these trends reveals that for a number of

vessel types, there has been no growth in this period, while others have

grown by 20-30%.

- Vessel types that have seen no significant growth are: Tankers

for chemicals and oil products, bulk carriers, reefers and

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

Table 14 Activity rates for ballast tanks for the years 1990-2006


miscellaneous, non-merchant. For these vessel types, no growth

will be assumed for the coming 20 years.

- Vessel types that have seen growth are: oil tankers, OBO,

container ships, general dry cargo ships, ferryboats, passenger

ships/ro-ros and fishing vessels. For these vessel types, a 20%

growth in vessel size will be assumed for the coming twenty

years.

Trends in wet ship surface: Combination of the growth in vessel activities and average vessel size

results in the index figures as compared to 2004 shown in the table

below. The result of growth in average vessel size is that ultimately, the

growth in WSA will be curtailed somewhat. This is because larger ships

have slightly less surface area per unit of cargo capacity than smaller

ships.

Year Index figure WSA

vessels with no

significant vessel

growth1

Index figure WSA

vessels with

significant vessel

growth2

Index figure WSA

fishing vessels

2004 100 100 100

2009 110 107 88

2015 124 116 76

2021 139 125 65

2027 156 135 56 1) Tankers for chemicals and oil products, bulk carriers, reefers and

miscellaneous, non-merchant. 2) Oil tankers, OBO, container ships, general dry cargo ships, ferryboats,

passenger ships/ro-ros and fishing vessels.

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

Table 15 Activity rates for the years 2004 through 2007


4.5 Annual data setting

Source for annual updating of data

The assumed data on the number of calling ships and the size of the

fishery fleet are updated annually against actual figures from Statistics

Netherlands.

The emissions calculated can be easily updated based on recent annual

figures of the number of calls of seagoing and fishing vessels. These

figures are published annually by Statistics Netherlands.

Description of data supply pathway

The data can be obtained from Statistics Netherlands in two ways. The

first is with the assistance of Statistics Netherlands help desk, which is

available to take questions on any published figures by phone and e-

mail. The second method is to use Statistics Netherlands's StatLine

database, which can be accessed via the internet. The data required are

found under the main group Bedrijfsleven ("Industry") by selecting the sub-groups Verkeer, vervoer en communicatie ("Traffic, transport and communication" and then Personen- en goererenvervoer ("Passenger and goods transport"). Under this group, select zeevaart ("sea transport") and then zeevaart, kwartaalcijfers ("sea transport, quarterly figures"). To obtain the correct figures, under the Periodes ("Periods") tab select the annual totals from 1996 through 2006, and under the

Belangrijkste Nederlandse havens ("Biggest Dutch ports") tab, select all

afzonderlijke zeehavens ("individual seaports"). Do not select

Nederland totaal (All Netherlands) under the "Biggest Dutch ports" tab

(this would exclude duplicate records).

For the fishery fleet, select the main group Bedrijfsleven ("Industry") and then the group Landbouw en visserij ("Agriculture and fisheries").

Then select Visserij ("Fisheries"). Under this group, select Zee- en kustvisserij ("Sea and coastal fisheries"). To obtain the correct figures, under the tab Onderwerpen ("Subjects"), select Vloot ("Fleet") and then Aantal schepen ("Number of ships"). All types must be selected.

Under the Periodes ("Periods") tab, select the desired years. Use of this database and the help desk is free. StatLine does not include

any figures for sea transport and traffic from before 1996. Older figures

may be requested from the information desk.


Sources for updating of spatial distribution data

If the spatial allocation must be updated, two data sources are required:

1. For the Dutch shipping lanes and ports, the database for

calculation of air emissions must be used.

2. To update spatial distribution data on the NCP, the MARIN

traffic and transport database must be used.

Both of these functions will most likely require specialist assistance.

For the calculation of the underwater surface area on the NCP, the

traffic and transport database from the risk model SAMSON is the

source for periodic updating against actual figures.

Calculation of the wet surface area of the ships relies on the data from

the SAMSON traffic and transport database. The basic data for the

traffic and transport database over the year 2004 were derived from

Lloyds. In view of their high cost, these basic data will only be

purchased periodically. Updating of the Lloyds database does not result

in major changes in wet ship area. MARIN converts the Lloyds data into

a traffic and transport database. In the future, this database will be

based on AIS data (whether or not this data will still have to be

acquired from Lloyds is uncertain). The traffic and transport database is

available from MARIN or the Traffic and Transport Advisory Service

AVV (E. Bolt). Up to now, the Lloyds database has been used to create

a new traffic and transport database approximately once in four years.


5 Description of emission pathways to water

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

The anodes emissions source has the spatial character of a diffuse

source. As a whole, the emission source can be essentially considered a

line source along the seaways on the NCP, with the strength

proportional to the annual wet ship area travelling those pathways

annually. The fisheries sector is an additional diffuse source. Depending

on size, the ports can be considered a point source (small ports) or an

area source (large ports).


6 Emission factors

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

6.1 Emission factors

For the ship’s shell and ballast tanks, the emission factor is compiled

from the corrosion rate of the anode material and the factors exposure

time and level of application of the anode material in question (zinc or

aluminium).

The emission factors for the various components are shown in table 16.

corrosion rate in

µg/cm2/day

Exposure

Days/year

Application factor Emission factor

kg/m2-year

Type of

vessel

zinc aluminium zinc aluminium zinc aluminium

Exterior of vessel

Tankers,

bulk

carriers,

container

ships

46 13,3 365 0.7 0.125 0,1175

0,0607

Ro-ro,

supply,

passenger,

ferry

61,5 17,8 365 0,7 0,125 0,1571 0,0812

Fishing

vessels

77 22,2 365 0,2 0,1 0,1967 0,1013

Ballast tanks

All vessels 276 79,8 128 0,1 0,3 0,0353 0,0306

corrosion rate in

µg/cm2/day

Exposure

Days/year

application factor Emission factor

g/m2/year

Type of

vessel

zinc aluminium zinc aluminium zinc aluminium

Seagoing

vessels

11,5 3,3 (~1,5)* 0,7 0,125 0,12 0,0062

Fishing

vessels

19,3 5,6 (~160)* 0,2 0,1 6,16 0,88

*) See chapter 10

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

Table 16 Emission factors for anodes on the exterior and interior of the vessel

Table 17 Emission factors for anodes on sea vessels in port


6.2 Application percentages

In practice, zinc and aluminium anodes are used. Additionally, IC

systems are used, and these systems cause no emissions. Percentages

used on the exterior of seagoing vessels are as follows (Willems et al.,

2003):

• 70.0% zinc anodes

• 12.5% aluminium anodes

• 17.5% ICCP systems

The proportion of cathodic protection systems in use by fishing vessels

is different than that of other seagoing vessels. IC systems are used in

70% of cases. For fishing vessels, the percentages are (Willems et al.,

2003):

• 20% zinc anodes

• 10% aluminium anodes

• 70% ICCP systems

Not all ships use anodes in their ballast tanks. 40% of ballast tanks are

equipped with anodes, while the other 60% use only coating

protection. Of the ballast tanks equipped with anodes, some are coated

and some are not. No information is available on percentages. The

percentages of anode materials in ballast tanks are (Willems et al.,

2003):

• 60% no anodes

• 30% aluminium anodes

• 10% zinc anodes

6.3 Time series, 1990-present

Ascertaining trends in application percentages will require further

research, mainly in the degree of use of materials. Such research could

be carried out by means of a survey among ships. This would require

considerable effort. So far, figures for the years from 1990 to the

present have been based on an assumption of the emission factors in

tables 16 and 17.

6.4 Annual data setting

There are no other estimates for the emission of zinc originating from

the corrosion of anode material on vessels for the NCP. In the coming

years, attention can be devoted to the trend in the application of the

type of cathodic protection (zinc, aluminium, IC systems) as well as

methods of handling ballast water.


7 Emissions calculated

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

7.1 Emission figures 2004

Emissions for 2004 for the ships of the spatial distribution database are

as follows:

Process description Zinc Cadmium Aluminium

Anodes on exterior of seagoing vessels sailing on NCP 90625 45 4680

Anodes on ballast tanks of seagoing vessels sailing on NCP 4367 2 3788

Anodes on exterior of seagoing vessels sailing from/to/in ports 18269 9 943

Anodes on exterior of seagoing vessels in port 17831 9 910

Subtotal, seagoing vessels 131093 66 10321

Anodes on exterior of fishing vessels sailing on NCP 3193 2 460

Anodes on ballast tanks of fishing vessels sailing on NCP 361 0,2 313

Anodes on exterior of fishing vessels in port 1811 1 263

Subtotal, fishing vessels 5204 3 897

7.2 Emissions 1990-2006

Tables 19, 20 and 21 show emissions by the anodes on the exterior and

interior of the vessel for the years 1990 through 2006.

Process description 1990 1995 2000 2005 2006

Anodes on exterior of seagoing vessels

sailing on NCP 94477 90642 86591 88858 90549

Anodes on ballast tanks of seagoing

vessels sailing on NCP 4553 4368 4173 4282 4364


sailing from/to/in ports 19045 18272 17456 17913 18253


in port 18589 17835 17037 17484 17816

Subtotal, seagoing vessels 136664 131117 125257 128536 130983

Anodes on exterior of fishing vessels

sailing on NCP 4313 3800 3685 2977 1685

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

Table 18 Emission by anodes on the exterior and interior of the vessel in 2004 (kg/year)

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

Table 19 Emission of zinc by anodes on the exterior and interior of the vessel since 1990 (kg/year)


Anodes on ballast tanks of fishing


Anodes on exterior of fishing vessels in

port 2447 2156 2091 1689 2573

Subtotal, fishing vessels 7031 6195 6008 4852 4549



sailing on NCP 47 45 43 44 45






in port 9 9 9 9 9



sailing on NCP 2,2 1,9 1,8 1,5 1,3


vessels sailing on NCP 0,2 0,2 0,2 0,2 0,1


port 1,2 1,1 1,0 0,8 0,8

Subtotal, fishing vessels 3,5 3,1 3,0 2,4 2,3

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

Table 20 Emission of cadmium by anodes on the exterior and interior of the vessel since 1990 (kg/year)




sailing on NCP 4879 4681 4471 4589 4676






in port 948 910 869 892 909



sailing on NCP 622 548 531 429 370




port 355 313 303 245 244

Subtotal, fishing vessels 1212 1068 1035 836 868

7.3 Emissions forecast, 2009-2027

Tables 22, 23 and 24 show the forecasts for emissions by the anodes

on the exterior and interior of the vessel for the years 2009 through

2027.

Process description 2009 2015 2021 2027

Anodes on exterior of seagoing vessels sailing on

NCP 97797 107187 117513 128873

Anodes on ballast tanks of seagoing vessels sailing

on NCP 4703 5142 5623 6151

Anodes on exterior of seagoing vessels sailing

from/to/in ports 19870 21984 24331 26937

Anodes on exterior of seagoing vessels in port 19224 21046 23047 25246

Subtotal, seagoing vessels 141595 155359 170513 187206

Anodes on exterior of fishing vessels sailing on NCP 2813 2416 2075 1783

Anodes on ballast tanks of fishing vessels sailing on

NCP 318 273 235 202

Anodes on exterior of fishing vessels in port 1596 1371 1177 1011

Subtotal, fishing vessels 4585 3939 3383 2906

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

Table 21 Emission of aluminium by anodes on the exterior and interior of the vessel since 1990 (kg/year)

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

Table 22 Emission of zinc by anodes on the exterior and interior of the vessel for 2009 through 2027 (kg/year)




NCP 49 54 59 64


on NCP 2 3 3 3


from/to/in ports 10 11 12 13



Anodes on exterior of fishing vessels sailing on NCP 1,4 1,2 1,0 0,9


NCP 0,2 0,1 0,1 0,1

Anodes on exterior of fishing vessels in port 0,8 0,7 0,6 0,5

Subtotal, fishing vessels 2,3 2,0 1,7 1,5



NCP 5050 5535 6068 6655


on NCP 4080 4460 4877 5335


from/to/in ports 1026 1135 1256 1391



Anodes on exterior of fishing vessels sailing on NCP 405 348 299 257


NCP 276 237 204 175

Anodes on exterior of fishing vessels in port 232 199 171 147

Subtotal, fishing vessels 790 679 583 501

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

Table 23 E mission of cadmium by anodes on the exterior and interior of the vessel for 2009 through 2027 (kg/year)

. . . .

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

Table 24 E mission of aluminium by anodes on the exterior and interior of the vessel for 2009 through 2027 (kg/year)


8 Comments and changes in regard

to previous version

The methodology for determining the emissions is the same as the

previous version of the fact sheets (Kuiper, 2003a and 2003b). A few

mathematical errors in the calculation of the emissions from the ballast

tanks and fishing vessels were corrected. Additionally, the emissions

from ships sailing from/to/in Dutch ports were added, applying the

same emission factors as applied on the NCP. The emissions from

floating tank cooling were removed, because the floating tank cooling

system is not in general use.

No changes in the methodology were made for the 2008 emission

round.

8.1 Difference in figures due to mathematical errors

The tables below show the differences in figures for the years 1999 and

2000. Principally, the differences can be traced back to mathematical

errors in the derivation and/or application of the emission factors

presented in the previous version. This version uses the same corrosion

rates as the previous version.

This addresses the mathematical errors referred to in section 7.4.

Process description 1990

old

1990

new

2000

old

2000

new


NCP 100,8 94,5 95,3 86,6


on NCP 17,0 4,6 16,1 4,2


from/to/in ports - 19,0 - 17,5

Anodes on exterior of seagoing vessels in port 24,6 18,6 23,2 17,0

Subtotal, seagoing vessels 142,4 136,7 134,6 125,3



NCP 2,5 0,5 2,3 0,4



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

Table 19 Emission of zinc by anodes on the exterior and interior of the vessel since 1990 (tonnes/year)



old

1990

new

2000

old

2000

new


NCP 50 47 48 43

Anodes on ballast tanks of seagoing vessels

sailing on NCP 8 2 8 2


from/to/in ports - 10 - 9



Anodes on exterior of fishing vessels sailing on

NCP 2,6 2,2 2 1,8

Anodes on ballast tanks of fishing vessels sailing

on NCP 1,2 0,2 1,1 0,2

Anodes on exterior of fishing vessels in port 9 1,2 7 1,1


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

Table 20 Emission of cadmium by anodes on the exterior and interior of the vessel since 1990 (kg/year)



old

1990

new

2000

old

2000

new


NCP 5,4 4,9 5,2 4,7


on NCP 14,8 3,9 14,2 3,8

Anodes on exterior of seagoing vessels from/to/in

ports - 0,9 - 0,9

Anodes on exterior of seagoing vessels in port 1,3 0,9 1,3 0,9

Subtotal, seagoing vessels 21,5 10,6 20,7 10,3



NCP 2,1 0,4 2,0 0,4


Subtotal, fishing vessels 4,4 1,4 4 1,2

There are also known studies for other areas. These studies usually

assume the estimated amount of anodes on a ship, the estimated

lifetime of the anodes and the amount of anode material still present at

the end of the lifetime (or at time of replacement). Comparison with an

American study (EPA, 1996) by this method reveals results very much

similar results compared to the emission findings of this report. Based

on the previous version of this protocol, an estimate was made of

emissions on the entire North Sea (Walraven, 2006) using the number

of seagoing vessels calling in other countries. For the year 2000, the

emissions of zinc in the entire North Sea were estimated at just under

1,800 tonnes. In view of the intensity of shipping traffic on the NCP

and the ratio of the areas of the entire NCP and the entire North Sea,

this estimate on the part of Walraven appears to be too high. This

apparent overestimate is most likely due to the very high total number

of seagoing vessels calling at Danish and English seaports. The size of

vessels and time spent in port were not accounted for in that study.

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

Table 21 Emission of aluminium by anodes on the exterior and interior of the vessel since 1990 (kg/year)


9 Accuracy and indicated subjects for improvement

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

The above can be expressed in the classification system used in the

Emissieregistratie publication series (Van Harmelen, A.K., 2001). This

method is based on the CORINAIR (CORe emission INventories AIR)

methodology.

CORINAIR uses the following quality classifications:

A: a value based on a large number of measurements from representative

sources

B: a value based on a number of measurements from some of the sources

that are representative of the sector

C: a value based on a limited number of measurements, together with

estimates based on technical knowledge of the process

D: a value based on a small number of measurements, together with

estimates based on assumptions

E: a value based on a technical calculation on the basis of a number of

assumptions

The number of seagoing and fishing vessels on the NCP is carefully

tracked, which means a classification of A for that component of the

activity rate. The wet surface of the ships on the NCP is derived from

model-based estimates. In total, this results in a classification of B for the

activity rate.

The emission factors are based on recommendations drafted based on

technical knowledge and experience from practice. This means that we can

classify the emission factors in category C.

As far as the distribution of emissions among individual compartments and

emission pathways to water is concerned, it is clear that all the emissions

directly enter the surface water, so category A applies here. Spatial

allocation is further explained in chapter 10. Because this is fairly detailed,

it can be classified as category B.

Element of emission calculation Classification Activity rates B Emission factors C (E for ballast water) Distribution among compartments A Emission pathway to water A Spatial allocation B


The number of ships on the NCP in this study is established for the year

2004. So as to also be able to present figures for the years 1990

through 2006, this figure was compared to the Statistics Netherlands

annual figures for the total number of seagoing vessels calling at Dutch

ports. Both the figures of the Statistics Netherlands and Lloyds were

considered reliable, but a linear relationship between the number of

ships on the NCP and the number of ships calling at Dutch ports is not

assured.

There are no good data available on trends in the application of the

various alternatives for cathodic protection (choice of zinc, aluminium

or IC). The precise degree to which ballast water is changed on the

NCP is not known.

Information on the number of vessels on the NCP and their underwater

surface area is only known for the year 2004, and this data comes from

the Lloyds database. So as to still be able to present figures for the

years 1990 through 2006, a constant average surface (that for the year

2004) per ship was assumed.

Both the figures of the Statistics Netherlands and Lloyds were

considered reliable, but whether the data on the ships on the NCP can

be directly projected onto the ships in port is uncertain.

9.1 Most significant areas for improvement

Simply based on the above, the most significant areas for improvement

can be identified as follows (in order of importance):

- In a subsequent year, a study can be set up to establish trends in the

use of the various different types of cathodic protection over time;

- An attempt can be made to obtain a better picture of the exchange

of ballast water on the NCP and the use of zinc and aluminium

anodes.


10 Spatial allocation

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

10.1 Seagoing vessels and fishing vessels on NCP

The emissions per 5x5 km map square are determined using the wet

surface area (WSA) calculated per vessel type by MARIN using the

Lloyds traffic and transport database for the year 2004.

The traffic types this includes are:

- Route-specific shipping transport

- Ships at anchor

- Fishing vessels

- Work ships

For every ship sailing on the Dutch Continental Shelf (NCP), the

maximum wet surface area is calculated using the vessel dimensions

known from the Lloyds ship register. Where possible, this calculation

was based on the Mennen-Holtrop equation (equation 1); where this

was not possible due to the lack of data, calculation was based on the

derived method for determining WSA based on ship size in GT

(equation 2). The actual wet ship area was obtained after correction for

actual cargo using equation 3. MARIN then applied this data to the

traffic and transport database after first averaging across the SAMSON

vessel types and SAMSON vessel size classes. Next, a determination of

the location of each kilometre square (in which water body defined in

the Water Framework Directive the square is situated) was made. The

emissions were then calculated for each Water Framework Directive

water body.


Figures 7 through 11 below show the wet ship area of the four types of

shipping traffic in spatial terms.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 7 Distribution of the total wet underwater surface area of ships on the Dutch Continental Shelf (NCP).

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

. Figure 9 Distribution of the wet underwater surface area of ships at anchor on the Dutch Continental Shelf (NCP).

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 8 Distribution of the wet underwater surface area of route-specific ships on the Dutch Continental Shelf (NCP).

. . . . . . . . . . . . . . . . . . . . . Figure 11 Distribution of the total wet underwater surface area of work ships on the Dutch Continental Shelf (NCP).

. . . . . . . . . . . . . . . . . . . . Figure 10 Distribution of the total wet underwater surface area of fishing vessels on the Dutch Continental Shelf (NCP).


10.2 Seagoing vessels in Dutch territory

Spatial allocation of the shipping emissions calculated was performed

based on the data on seagoing vessels calling at the major seaports.

In this calculation, a distinction is made by vessel type and the phase

the ship is in: sailing in, manoeuvring and in port. All basic data are

drawn from the EMS models for the calculation of air emissions. The

activity rates from the air module are expressed for these phases in GT-

km for sailing in, GT-hours for manoeuvring and GT for in port. These

quantities are assigned per port and per phase to shipping lane

segments from the database “Nationaal Wegenbestand” (NWB, a

publication of the Traffic and Transport Advisory Service, an agency of

the Ministry of Public Works & Water Management). The activities are

assigned to each port in proportion to the length of the shipping lane

segments traversed.

For each phase that the vessels sail in Dutch territory, a different

formula is used for the calculation of the average wet ship area (WSA)

present.

The formula for conversion of ships in port is:

GT * WSA/GT * Time in port / 8760

The GT of ships in port is derived from the file supplied by AVV for the

calculation of air emissions.

The formula for conversion of ships at sail is:

GT-km / Speed * WSA/GT / 8760

The GT-km of sailing ships is calculated using the model with which the

air emissions of sailing ships are calculated.

The formula for conversion of manoeuvring ships is:

GT-hours * WSA/GT / 8760

The GT-hours of manoeuvring ships is calculated using the model with

which the air emissions of manoeuvring ships are calculated.

Table 22 shows the factors used for conversion from GT to WSA.

Vessel type WSA/GT

(m2/GT)

Time in

port

(hours)

Speed

(km/hour)

Oil Tankers (Crude) 0,23 28 17,3

Other Tankers (Juice,

Chemical)

0,43 24

19,2

Bulk carriers 0,24 52 20

Container Ships 0,25 21 20,2

Conv. General Cargo 0,54 25 20,2

Ferries/Ro-ro 0,18 24 23,1

Reefers 0,51 31 24,8

Other Ships 0,5 46 26,3

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 22 Conversion factors for ships in port, manoeuvring and at sail, by wet surface


The red lines5 on the map below (figure 12) indicate which line

segments from the NWB are linked to the emissions from seagoing

vessels in port. GIS was used to determine what portion of a given

shipping lane segment falls within a given Water Framework Directive

water body. These segments were used to assign the emission to a

Water Framework Directive water body.

10.3 Fishing vessels in ports

The underwater surface area of fishing vessels in fishing ports is

determined using the LEI's VIRIS system, which records all fishing vessel

movements at sea. VIRIS does not record the number of days in port

directly. The number of days in port is 365.25 days (number of days in

the year) minus the number of sailing days. A ship may call at multiple

ports in the course of a year. The number of days in a specified port is

computed by multiplying the ratio of total number of journeys per year

to number of journeys from the port in question by the number of days

in port as calculated above. The number of days in a port is multiplied

by 24 to obtain the number of hours in that port.

The number of hours in a port is multiplied by 1.0*GT of ship to obtain

the underwater surface area. The underwater surface area is then

aggregated per port and divided by 8760 (hours per year).

5 The protruding line segments at Scheveningen and Goeree-

Overflakkee were left out of the database.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 12 : Seagoing vessels en route to ports and in Dutch ports and Emden


Table 23 shows the underwater surface area per fishery port in 2005,

and figure 13 shows the locations of the ports. The Water Framework

Directive area of each port is known. Not all ports are located in Water

Framework Directive areas that are classified as saline.

Port WSA6

Oostburg - Breskens 952

Schouwen Duiveland 51

Delfzijl 1770

Harlingen 19569

Den Helder 9199

Hemelumer-Oldeferd (municipality of Nyefurd) 20

IJmuiden 52300

Katwijk 3

Ulrum - Lauwersoog 5559

Terneuzen 19

Scheveningen - Den Haag 14577

Goedereede - Stellendam 6369

Stavoren (municipality of Nyefurd) 98

Terschelling 158

Texel 4320

Urk 253

Vlissingen 10309

Wonseradeel 116

Wieringen 2522

Yerseke 385

Zierikzee 10

128559

6 Corrected for calls of foreign fishing vessels (approx. 30 percent)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 23 Average wet surface of fishing vessels present in fishing ports in 2005, (m2)


. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 13: Location of Fishing Ports


11 References

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