1. Modelling the economic impact of invasive species and mitigation measures in fouling and ballast waters for the shipping industry
Jose A. Fernandes (Plymouth Marine Laboratory;
Lionel Santos, Thomas Vance, Tim Fileman, David Smith, John Bishop, Frederique Viard, Ana M. Queirós,
Gorka Merino, Erik Buisman, Melanie Austen
Maritime transport and shipping is impacted negatively by biofouling, which can result in a reduction in speed and increased fuel consumption. Thus, costs for the removal or prevention of fouling can be considered an investment to reduce fuel consumption. However, anti-fouling measures also contribute to reducing the rate of introduction of non-indigenous species (NIS). NIS can be also introduced via transport in ballast water tanks, a threat address by IMO and US regulations. Mitigation measures to reduce the transport of NIS on hulls and within ballast water and ballast sediments impose additional costs throughout the maritime transport sector. We estimate that the operational cost of current mitigation measures, together with ballast water treatment systems that comply with both the IMO and US regulations, may represent between 1.6% and 4% of the annual operational cost for a ship, with the higher proportional costs generally relating to smaller ships.
However, our analysis indicates that fouling by NIS may affect fuel consumption more than fouling by native species due to differences in species’ life-history traits and their resistance to antifouling coatings. Therefore, the cost of mitigation measures to reduce the spread of NIS could be smaller than the additional cost of higher fuel consumption arising from fouling by an unconstrained and increasing number of NIS. Better estimates of the economic impact of NIS to the shipping industry will require more comprehensive data on the composition of biofouling communities, the life-history traits of these species and the cost structure of shipping industries.
Fig. 1. Native species and NIS are transported on the hull and in Ballast tanks.
Impact of species on fuel consumption
Economic impact of mitigation measures
A list of 302 species found in fouling was compiled based on publications and the AquaNIS database by two experts in bio-fouling who selected a subset of 59 species considered most problematic for fuel consumption in ships. Then, public datasets (SeaLifeBase, Biotic, WoRMS, MarBEF) were used to gather as much information as possible about the biological traits of these species. The presence of data for each of these traits ranged from 4.5% to 41% for native species and between 9.1% and 18.2% for NIS. We compared the average of each of these traits between native species and NIS in order to observe if there is evidence that native species could have higher impact on fuel consumption (Table I).
To reduce the complexity of calculating the cost of mitigation measures (MM) across a diverse array of ships, we grouped similar ships into a reduced number of categories using 3 criteria that are correlated: dead weight tonnage (DWT), ballast water (BW) capacity and pumping capacity. The IMO uses BW capacity to delimit their deadlines; however, the costs of ballast water treatment systems (BWTS) are determined by the pumping capacity and the total annual cost is related to the DWT. Therefore, for 6 categories of ships, which account for 93% of the world fleet that uses BW, information on annual cost and the cost of measures to mitigate the spread of NIS were compiled. Sparse literature was found. Therefore, other sources of information were used. This included shipping industry talks at international industrial conferences, interviews with experts and a survey that was answered by 6 shipping companies.
Parameters
Native
NIS
Index
Growth (L∞)
9.370
9.760
1.042
Growth (K)
0.330
0.550
1.667
Growth (ø)
1.220
1.470
1.205
Length-Weight (a)
0.103
0.101
0.977
Length-Weight (b)
2.746
2.932
1.068
Bending (degrees)
28.182
33.333
1.183
Salinity (psu)
19.750
12.000
0.608
Panels coverage 1
0.088
0.138
1.422
Panels coverage 2
0.120
0.100
0.833
Panels coverage 3
0.070
1.000
Colonial level
2.850
2.270
1.796
Hydrodynamic drag
2.000
2.480
1.240
Resistance to copper
0.600
Resistance to pollutants
1.070
Index geometric mean
1.041
Type of ship
Bulk
carrier
OSV
Dredger
Ro-ro
cargo
General
Oil
tanker
Dead weight tonnage
1100
2600
12304
31340
73000
113000
% cost antifouling
0.07
0.05
0.13
0.35
0.04
0.03
% cost BWTS
9.91
3.87
1.23
0.88
0.33
Total % cost MM
9.99
3.92
1.36
1.22
0.37
0.36
Table II. Percentage of total annual costs represented by mitigation measures (MM), both antifouling and ballast water treatment system (BWTS).
The results of comparing cost of MM and total annual costs (Table II) shows that the smaller the ship the higher percentage of total costs MM represents. However, bigger ships benefits margin could be very adjusted due to high competition in economies of scale where with more distance travelled and commodities transported more expensive and efficient control measures can lead to lower unitary cost.
Table I. Indices of native species vs. NIS in the North Sea.
Conclusions: Estimates vary, but about 68,000 ships will require ballast water treatment systems (BWTS) to comply with IMO regulation. This adds to current costs of antifouling measures and new antifouling guidelines to reduce NIS spread. Current antifouling mitigation measures have direct benefits due to fuel consumption reduction. However, BWTS can be seen only as a cost unless they reduce the spread of NIS species and NIS have more impact on fuel consumption through biofouling than native species. Our results of the index comparing native species and NIS suggest that could be the case. However, our results are based in sparse data and further research is needed to confirm this hypothesis.
VECTORS project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no