### Viewpoint 

# Challenges in global ballast water management

Øyvind Endresen * 

## , Hanna Lee Behrens, Sigrid Brynestad, Aage Bjørn Andersen, Rolf Skjong

Det Norske Veritas, Veritasveien 1, N-1322 Høvik, Norway

Abstract

Ballast water management is a complex issue raising the challenge of merging international regulations, ship’s specific configurations along with ecological conservation. This complexity is illustrated in this paper by considering ballast water volume, discharge frequency, ship safety and operational issues aligned with regional characteristics to address ecological risk for selected routes. A re-estimation of ballast water volumes gives a global annual level of 3500 Mton. Global ballast water volume discharged into open sea originating from ballast water exchange operations is estimated to approximately 2800 Mton. Risk based decisionsupport systems coupled to databases for different ports and invasive species characteristics and distributions can allow for differentiated treatment levels while maintaining low risk levels. On certain routes, the risk is estimated to be unacceptable and some kind of ballast water treatment or management should be applied.

 2004 Elsevier Ltd. All rights reserved.

Keywords: Ballast water; Risk assessment; Norway; Water exchange; Ship safety

1. Introduction

A wide variety of organisms that are transported in ballast water in ocean trade vessels may establish themselves in new environments when discharged from the ship and alter or impact the receiving ecosystems (Hayes and Sliwa, 2003). The rate of introductions has been increasing exponentially since the 1800s (Carlton, 2001) and invasive marine species are one of the greatest threats to the world’s oceans (GloBallast, 2002a). The economical impacts of these invasions is considerable, the zebra mussel alone accounts for over $500 million a year (Ruiz et al., 2001). Ballast water management is a complex issue raising the challenge of merging international regulations, shiptechnical solutions and ecological conservation. International regulations by nature take a relatively long timeto enter into force, hence regional and national regulations tend to be developed to meet with more local demands. Such developments are of major concern to the shipping industry, which must operate across different jurisdictions. Ecological awareness that forms the public opinion now demands that measures to reduce the risk of invasive species introductions. The current recommended method for controlling the introduction of non-indigenous species is open ocean exchange of ballast water (IMO, 2003). It is expected that the International Maritime Organisation (IMO) member countries will adopt a convention (IMO, 2003) regulating ballast water issues in the Spring of 2004. Open ocean exchange of ballast water involves replacing coastal water with open ocean water during a voyage, either by emptying and refilling ballast tanks (sequential exchange) or by flow-through dilution (three times tank volume). It is important to recognise that open ocean exchange is not always biologically effective and is not always possible to perform due to ship safety and operational issues involved (as access to open ocean water). These operational considerations and safety aspects indicate that a portion of the ballast water transported annually will have to be treated by other methods, or discharged
as untreated ballast water. To determine where most effort should be expended on mitigation and control strategies, a risk based approach that ensures focus on trades posing unacceptable risk should be considered for ballast management. This again raises the challenges of data input and quality, methodology and understanding * Corresponding author. Fax: +47-67-57-75-20.

E-mail address: oyvind.endresen@dnv.com (Ø. Endresen).

0025-326X/$ - see front matter  2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2004.01.016 www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 48 (2004) 615–623of ecological systems that forms the basis for a risk based approach. This is further complicated by the presence of other transfer vectors, as for example hull fouling. The complexity in the situation is shown in this paper by going through some of the elements needed for theunderstanding of ballast water management. We consider the steps of ballast water volume, frequency, safetyand operational issues aligned with regional characteristics to address ecological risk for selected routes.

2. Ballast water volume

Ballast water capacity varies as a function of cargo carrying capacity and ship type as discussed in Endresenet al. (2003c). The annual ballast water amounts transported can be estimated as a function of the total cargo transported annually. The cargo amounts transported are less than capacity, which may be measured by the dead weight tonnage (Dwt). For large tankers, a rule of thumb is that at least 2.5% of the total carrying capacity is reserved for stores, provisions and bunkers. The maximum cargo load factor is hence 0.975, but can also be lower (0.65) due to partial loading and multi-porting (Wijnolst and Wergeland, 1997). The converting factor from Dwt to tonnes of cargo is typically 0.87 for tankers and 0.91 for Dry bulk (Fearnleys, 2002b), and 0.89 is assumed to be a representative figure in our calculations.The ballast capacity is based in these assumptions calculated to about 40% of the cargo transported (36% ballast capacity per Dwt divided by 0.89 tonnage cargo per Dwt). Shipping is the dominant mode of transport, accounting for almost two thirds of world trade, in metric tonnes (Hoffmann and Kumar, 2002). Domestictransport of cargo by ships amounts to some 3300 million tonnes (Mton) while merchant ships in international trade transport about 5434 Mton of cargo annually (Fearnleys, 2002a). The major bulk cargoes are fuel, raw materials for industry, and food. By commodity, crude oil represents the biggest share (30%), followed by coal (9.6%), iron ore (8.4%), oil products (7.7%) and grain (4.2%) (Fearnleys Review, 2001). The global ballast water required for this cargo transport is estimated to be approximately 3500 Mton. This is shared between international (2174 Mton) and national (1300 Mton) trade. Internationally, oil tankers account for some 37% of the ballast water annually transported, while Dry bulk cargo carriers account for 39% (coal, iron ore, grains and other bulk commodities). The remaining 24% includes General Cargo, Container vessels, Ro-Ro,
Chemical tankers and LNG tankers. The contribution of the latter group may be lower since General Cargo and Container vessels rarely operate return voyages in ballast condition and mainly use ballast for adjusting
trim and heel. 3. Ballast water movement

Most of the maritime traffic (85%) takes place in the northern hemisphere, specifically the North Atlantic/ Northern Europe and the northern Pacific (Corbett et al., 1999; Endresen et al., 2003a). This is supported by international cargo statistics (Fearnleys, 2000) and port surveys (ISL, 2001). The major bulk cargoes are mainly transported in large vessels within a fairly well defined system of international sea routes. Fig. 1 presents international sea routes for some of these vessels types (Endresen et al., 2003b). The international sea borne cargo statistics indicate that the US, Europe and Japan are the main export regions of ballast water by crude oil carriers. The main importing regions are the Middle East, the Caribbean and Africa (Fig. 3). The pattern isdifferent for bulk vessels where the most important export areas of ballast water is Asia and Europe while theimporting regions are North and South America, Australia and Asia (Fearnleys, 2000). Table 1 presents cargo trade per region indicating export and import regions of
ballast water.

4. Volume exchanged in open ocean

Ballast water volume uptake in port and volume exchanged in open sea are not necessarily equal. This section evaluates safety and operational issues involved, and estimate the potential ballast water volume that can be exchanged in the open ocean.

4.1. Safety factors

The hazards associated with the sequential methodare presented in two studies performed by the International Association of Classification Societies (Skjong and Dahle, 1997; Skjong and Spouge, 2000). One hazardis that permissible bending moments and the shear forces on the ship’s hull may be exceeded (Rigby and Hallegraeff, 1994; Transport Canada, 1995; Karaminas, 2000). Obviously, the problem may be solved by designing new ships. This would, however, add costs.Other criteria most frequently found difficult to maintain during all stages of the exchange sequence are bridge visibility, propeller immersion and minimum forward draft (Skjong and Dahle, 1997; Skjong and Spouge, 2000; Karaminas, 2000; Japan, 2001). From these studies it is apparent that a vessel carrying out sequential exchange while exposed to wave loads mightexperience excessive bending moments and shear stresses representing a threat to structural integrity. Slamming and tank sloshing increase the risk of causing structural damage to the vessel. Sequential exchange is the option chosen by most ships that exchange ballast water, including 75% of the ships coming into California 616 Ø. Endresen et al. / Marine Pollution Bulletin 48 (2004) 615–623and Texas ports, but there are some variations betweenvessel types (National Ballast Information Clearinghouse, 2002). The continuous flushing method avoids the problem of exceeding safe bending moments and shears forces, since the fresh ocean water is pumped via the ballast pumps into the ballast tanks and allowed to overflow in a safe manner. However, the IMO guidelines (IMO, 1997) require that three times the tank volume must be pumped through the tank, which increases the exchange time and cost significantly compared to the sequential method. One of the major concerns with this process is over-pressurization of the ballast tank(s) or ballast piping system, which could cause damage to the ship’s structure. Other safety issues are interference with the watertight integrity of the main deck during removal of the main deck manhole covers and icing on deck during sub-zero temperature conditions. For new ships all these
hazards could be removed at a cost.

4.2. Modelling ofballast water exchange

Ships on ballast voyages will have to exchange ballast water mid-ocean. Based on the above studies, we have assumed that the safety critical significant wave height is 3 m, and that this applies to all vessels executing open sea exchange. This is clearly a simplification since the critical limits will depend on actual sea-state (direction,periods, spectrum, etc.) and ship specifics (arrangements, design, ballast condition, etc.). Ballast voyages are normally shorter in distance compared to cargo voyages. A study that followed 1580 cargo vessels, demonstrated significant variations in operational Fig. 1. Vessel traffic densities for year 2000 based on the AMVERdata (AMVER, 2001). Upper left : all cargo and passenger ships in the merchant fleet, upper right : oil tankers, lower left: bulk carriers, lower right : container vessels (from Endresen et al., 2003b).

Table 1 World seaborne cargo trade per region in 2000 (in Mton) (Hoffmann and Kumar, 2002)

Region Exports Imports Total

Asia Pacific 1395.0 2106.1 3501.2 Europe 673.4 1421.8 2095.2
North America 536.2 910.7 1446.9

Latin America

and the Caribbean 948.3 313.0 1261.3

Persian Gulf 832.3 76.2 908.5

Other 829.2 386.6 1215.8

Total 5214.5 5214.5 Ø. Endresen et al. / Marine Pollution Bulletin 48 (2004) 615–623 617profile of different vessel types/sizes and type of trade (United Kingdom, 2002). They reported a mean total time at sea for all vessel types involved in all trades of 5.8 days and up to 13–14 days for larger vessels. Taking this into account we assume that on average a ballast voyage by vessels in international trade takes 7 days. Of these 2 days are spent within the 200 nm zones leaving 5days for open ocean exchange. The probability of performing ballast water exchange under these criteria (5 days and 3 m critical wave height) is estimated by MonteCarlo simulation using hind cast wind data (The Norwegian Meteorological Institute, 1955) from the period 1955–1999 for a representative sector for the NorwegianSea (for details see Endresen et al., 2002). These calculations show that 7% of the ships will not be able to exchange ballast water by open ocean exchange if 1 day is needed, and 30% of the ships will not be capable of performing exchange if 2 days are needed. Note that thenecessary ballast water exchange period varies, but larger ships may use up to 2 days for ballast water exchange. Seasonal variations in traffic, geographical variations and weather conditions may influence the results. As an example, for vessels operating on routes north of the 25th latitude during winter the possibility of performing ballast water exchange will be significantly reduced (Young and Holland, 1996; Gulev and Hasse, 1998; Bitner-Gregersen et al., 1995). 5. Operational issues

Medium and small vessels operating in shallowcoastal routes (such as the North Sea) will not necessarily comply with the IMO Guideline for ballast water exchange (Spain, 2000; Endresen et al., 2002). Such routes exist between the North Sea and other European countries, in the Mediterranean Sea and between the
Caribbean Sea and North/South seas of America. Theseand other shallow and near coastline sea routes represent a large portion of the traffic. The global traffic data
from AMVERshows that about 60% of the traffic in the North Atlantic operates within 200 nautical miles (nm) from shore at any given time (Fig. 2). The AMVER system is used to track about 30% by number of the world cargo and passenger fleet greater than 2000 Dwt (more than 7300 vessels) that daily report to AMVERduring voyage (AMVER, 2002). These findings correspond with those of Corbett et al. (1999) and Oftedal (1996), who reported that 74–83% of the ships are within 200 nm of land at all times (Liberia, 1996; Norway, 1994). A large fraction will also be employed in regional or coastal trade. For example, Whall et al. (2002) claimed that some 60–65% of the traffic in European waters was regional. Table 2 summarizes the results of our analyses, and presents cargo and ballast water inventories (uptake and discharge). Based on the above analyses we assume the

Fig. 2. Shows ship traffic density and bottom topography (GEBCO, 1997; AMVER, 2001), which illustrates that a significant portion of the ship traffic occurs in costal and shallow waters. When compared with the reported ballast water exchange locations for individual ballast tanks (Ruiz et al., 2001) it is apparent that much of the ballast water exchange is not performed in deep ocean water. 618 Ø. Endresen et al. / Marine Pollution Bulletin 48 (2004) 615–623national part of the ballast water, i.e. about 1300 Mton, will not be handled through open sea exchange. Taking into account the practical and operational aspects it is expected that about 10% of the loaded international ballast water or 200 Mton will not be exchanged in open
sea. It is assumed that 25% of the international vesselswill use the three times dilution of flow through exchange, and the rest sequential exchange (75%). The total ballast water volume exchanged in open waters will then be 2788 Mton (Table 2). The estimated volume exchanged in open ocean might be too low, when the considering location reported for completion of ballastexchange (see above). The cost of an open ocean exchange of 2788 Mton of ballast water is estimated to be USD 40–60 million, assuming 1.6–2.4 cents/m 3 , converted from Australian cents, i.e. 2.5–3.7 cents/m 3 and
assumed 1 m3  1.025 ton based on Rigby and Taylor (2001).

5.1. Ecological risk assessments

Ballast water exchange is not always possible to perform due to safety issues as well as to geographical constraints (see above). In addition, it is not always biologically efficient, thus providing motivation for thedevelopment of technologies to reduce the risk of unwanted invasions via ballast water and risk based approaches that determine what type of treatment is called for. Risk based decision support systems are currently being used by the Australian government (AQIS, 2002),and being developed for developing countries by GloBallast (GloBallast, 2002b, 2003), and have been developed by Det Norske Veritas (Behrens et al., 2002). Risk based systems must be able to couple data bases that include the potentially invasive species present ineach port, port characteristics and animals characteristics and distribution spatially and seasonally. Thedevelopment of good data bases and systems for utilising data can allow for differentiated treatment levels of ballast water while maintaining low risk levels. If a ship on a route can be shown to represent an acceptable risk in of introducing unwanted organisms, the level of treatment required could be different compared to routes posing an unacceptable risk of transfer. Presentefforts are still focusing on developing risk based evaluation methodologies able to assess the need for ballast water treatment. It is important to recognise thatcurrent knowledge does not allow for predictive modelling of ecological systems. In addition, the data collection is difficult and needs to be organised so thatthe data can be used in ecological models. The development of empirical ecological modelling approaches and associated risk evaluation systems will enhance the understanding of data needs and the development of a
common framework to assess this information. This section presents a general risk assessment for transport of ballast water with Crude oil carriers from different donor areas into Europe (recipient area) applying the risk evaluation approach using the DNV EMBLA concept, which is outlined in Fig. 4.

5.2. Risk assessment for ballast transport into the western coast ofNorway

The origin of ballast water discharged in ports by large vessels is normally well defined according to vessels types and/or cargo. Thus it is possible to undertake risk assessments for transport of ballast water from one area to another area. The risk assessment approach allows differentiation on the use of treatment (exchange or any other type of treatment) based upon the risk posed by the ballast water transported. A crude oil transport model has been developed by means of a Geographical Information System (GIS). Fig. 3 illustrates the relations between loading and unloading locations for Crude oil carriers greater than 50,000 Dwt (Endresen et al., 2003a). Based on the GIS model input data, the amount of ballast water, dischargefrequency and voyage duration are calculated. Combining these results with ecological information it ispossible to estimate the overall risk for this fleet segment by applying the risk evaluation methodology in Table 2 National and international cargo and ballast water inventories, separated on ballast water uptake and ballast water exchanged (Mton)

Inventory International National Comments

Cargo 5434 3300 Year 2000 Ballast uptake 2174 1300 40% of cargo Ballast uptake oil tanker 804 – 37% of ballast uptake Ballast uptake bulk ships 848 – 39% of ballast uptake Ballast uptake other ships 522 – 24% of ballast uptake Ballast uptake not exchanged 217 – 10% of total uptake Ballast uptake and exchanged 1956 – 90% of total uptake Flow through exchanged 1467 – 25% of exchanged, three times diluted Sequential exchanged 1320 – 75% of exchanged Sum exchanged at sea 2788 – Ø. Endresen et al. / Marine Pollution Bulletin 48 (2004) 615–623 619EMBLA. To illustrate this method, risk is estimated for selected sea routes into the western coast of Norway (Table 3).
The overall risk evaluation indicates that ballast water from the northeast coast of the US poses a high riskirrespective of season. This is due to the high biogeographical compatibility level between the east coast of the US and western coast of Norway, 1994, and the overlap in physical conditions as temperature and salinity. Water from Piraeus, Greece is estimated to have a high risk level during spring and a medium risk level for the rest of the year. A more detailed risk analysis on species and ship level can be undertaken when more
data is available.

5.3. Risk reduction

For the high and medium risk routes, assessment of the ballast management onboard is recommended for the purpose of minimising the risk potential throughimproved internal ballast water management. For further reduction of the environmental risk, ballast water exchange or treatment by an approved technology should be used. Ideally, for high risk routes, open oceanexchange should only be accepted if it can be documented that the exchange is biologically efficient, otherwise other technology should be applied. Currently no ‘‘silver bullet’’ technology is available, but the new opportunities for good technological solutions are driving research, and a number of technologies are Fig. 3. Export (loading) and import (discharge) areas of ballast water by large crude oil carriers in 1996.

Fig. 4. EMBLA risk assessment structure (Behrens et al., 2002). 620 Ø. Endresen et al. / Marine Pollution Bulletin 48 (2004) 615–623under development (Hallegraeff, 1997; Buchholz et al., 1998; Oemcke, 1999; GloBallast, 2002a; Ruiz et al., 2001; AQIS, 2002; Brynestad, 2002, Cangelosi et al., 2001, Rigby et al., 1999; Tamburri et al., 2002, URS/Dames and Moore, 2000). As physical methods cannot practically remove all organisms and most of the chemical/ionisation methodsrequire an initial ‘‘clean-up’’ step before the desired effect can be assured, the use of combinations of methods is often considered. There is a need for the development of internationally agreed and approved performance standards and evaluation procedures for the formal acceptance of any new techniques that are developed to ensure compliance with defined ballast water standards (i.e. the IMO ballast water standard to be outlined in the forthcoming convention). Such performance standards must also take into account the occupational safety and health issues. Several institutions are at present working on developing such standards (Andersen et al., 2003; Stevens et al., 2003) that are expected to be finalised during 2004.

6. Discussion

The total amount of ballast water unloaded from ships in international trade is estimated to be 2200 Mton
in 2000. Tankers and bulk carriers account for about 76% (37% oil tankers + 39% bulk carriers) of the total ballast water volumes. These vessels mainly operate within a fairly well defined set of international trade routes. General Cargo and Container vessels, often sailing with a mix of ballast and cargo comprise a major part of the remaining 24%. Untreated ballast water discharged by ships in national trade is estimated to be 1300 Mton, resulting in global annual amount of 3500 Mton. This figure is significantly lower than previous reported estimates. The global ballast water amount discharged into open sea is estimated to be around 2788 Mton taking into account the use of flow through method and practical and operational issues. A mid-ocean exchange of 2788 Mton of ballast water represents an annual treatment cost of USD 40–60 millions. Using alternative treatment methods is expected to introduce higher costs to the industry. The ballast treatment methods used will vary according to ship type and requirements set by the authorities, but developing methods for large volumes of water is a challenge that has not yet been adequately

met. Risk based decision support systems coupled to databases for different ports and invasive species characteristics and distributions can allow for differentiated treatment levels while maintaining low risk levels.
Within certain routes as from the northern US to western coast of Norway, the risk is estimated to be unacceptable and some kind of ballast water treatment or management should be applied.Another challenge is the documentation of potentially invasive species in the water taken on board. An international harbour monitoring network and database regime is necessary to make risk assessment a viable alternative. As the presence of organisms can vary greatly by season, monitoring would have to be on a regular basis. Advances in rapid genetic detectionmethods may enable the development of simple diagnostic tests that can detect the presence of selected indicator species. Although this paper focuses on the ballast water transfer the authors acknowledge that other vectors may be equally important and must be considered for any ecological system.

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