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1 INTRODUCTION
The maritime industry serves as a vital economic
foundation, as ships transport 90% of global trade. The
heavy reliance on shipping operations results in
environmental challenges due to energy consumption
and pollution [1]. The International Maritime
Organization (IMO) emphasizes that shipping must
reduce its greenhouse gas (GHG) emissions to achieve
at least a 50% reduction from 2008 levels by 2050
(International Maritime Organization, 2018). The
shipping industry experiences increased fuel
consumption and emissions primarily due to
biofouling. Biofouling refers to the unwanted
accumulation of microorganisms, plants, algae, and
animals on underwater surfaces, particularly ship
hulls. Ship hulls affected by biofouling exhibit
increased hydrodynamic drag, which leads to elevated
fuel consumption and operational costs. Biofouling
causes energy inefficiencies and poses ecological risks
through the spread of invasive species and the release
of toxic substances from antifouling coatings [2]. This
paper investigates how biofouling control practices
influence ship energy performance and pollution
reduction efforts. It describes biofouling mechanisms,
current management strategies, and emerging
technologies that improve energy efficiency while
mitigating environmental impacts. By implementing
effective biofouling control strategies, the shipping
industry can enhance operational efficiency and
contribute to a sustainable maritime future.
Enhancing Ship Energy Efficiency and Preventing
Pollution through Effective Biofouling Control
Measures as a Future Direction for a Sustainable
Shipping
M. Kawa
Gdynia Maritime University, Gdynia, Poland
ABSTRACT: In recent years, the global emphasis on climate and environmental protection has been increasingly
prominent, with the maritime industry playing a critical role in this endeavour. The path to decarbonizing
maritime transport is marked by the implementation of stringent regulations such as EEXI/CII and EEDI, aimed
at reducing greenhouse gas emissions and enhancing energy efficiency. As industry navigates this transitional
phase, there is a growing need for cost-effective solutions that align with evolving environmental standards. One
frequently underappreciated factor influencing fuel consumption and total emissions is biofouling—the
accumulation of marine organisms on ship hulls. Biofouling significantly increases drag, leading to heightened
fuel consumption and emissions, with severe cases potentially increasing emissions by up to 55%. This article
explores the impact of biofouling on maritime sustainability, discussing its effects on fuel efficiency, emissions,
and environmental pollution, while examining current regulatory frameworks and innovative mitigation
strategies such as in-water cleaning and advanced anti-fouling technologies. By addressing biofouling effectively,
the maritime sector can make substantial strides towards meeting decarbonization targets and reducing its
ecological footprint.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 19
Number 4
December 2025
DOI: 10.12716/1001.19.04.26
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2 BIOFOULING
The natural process of biofouling happens when
aquatic organisms settle on underwater surfaces
especially ship hulls. The maritime industry faces
major difficulties because of this phenomenon which
damages vessel performance while raising fuel costs
and creating risks of invasive species entry into new
environments. The growing global shipping industry
requires better knowledge of biofouling mechanisms
and stages and influencing factors which benefits ship
operators and marine biologists and environmental
managers.
Biofouling describes the unwanted growth of
microorganisms together with plants and animals and
algae on underwater surfaces which mostly occur in
marine environments [3]. The biofouling organisms
include bacteria and diatoms as well as larger species
such as barnacles and mussels and seaweeds. The
accumulation of organisms on ship hulls modifies its
physical structure while simultaneously causing
hydrodynamic performance issues which result in
drag increase and fuel efficiency reduction.
2.1 How Biofouling is Created
The process of biofouling begins with the settlement of
microorganisms on submerged surfaces. Several
factors contribute to the creation of biofouling,
including surface characteristics, environmental
conditions, and biological factors.
2.1.1 Initial Settlement of Microorganisms
The first stage of biofouling starts when
microorganisms begin to attach themselves to ship
hulls. The first stage of biofouling starts when a ship
enters water and continues to develop after that initial
contact. The surface of the hull becomes colonized by
bacteria and phytoplankton through physical and
chemical interactions during this stage.
Mechanisms of Attachment
− Physical Forces: The surface attachment of
microorganisms occurs through three main forces
which include van der Waals forces and
electrostatic interactions and hydrophobic effects
[4]. The forces enable bacteria together with other
microorganisms to stick to the hull during their
initial contact.
− Chemical Interactions: The chemical composition of
the hull surface can influence microbial adhesion.
For instance, surfaces with specific chemical groups
may promote or inhibit the settlement of certain
microorganisms
− Biological Factors: The settlement of particular
microorganisms depends on the specific chemical
groups which exist on surface materials. Bacteria
can produce extracellular polymeric substances
(EPS), which create a sticky matrix that enhances
adhesion and serves as a substrate for additional
organisms.
2.1.2 Biofilm Development
The microorganisms establish themselves and
multiply to create biofilms which consist of complex
microbial communities that use EPS as their structural
matrix. The formation of biofilms usually begins within
a time span of days to weeks after the initial settlement
of microorganisms.
Biofilms contain multiple microbial species which
include bacteria together with algae and fungi. The
diverse nature of biofilm communities makes them
more resistant to environmental stressors. Mature
biofilms demonstrate enhanced resistance to
antimicrobial agents and physical removal techniques.
The resistance of biofilms creates difficulties for
cleaning operations and management strategies.
2.1.3 Macrofouling (Settlement of Larger Organisms)
The last phase of biofouling leads to the maturation
of the fouling community which results in stable
species composition and species interactions. The
community maturity stage creates intricate ecological
relationships because species compete for resources
and habitat space. The biofouling community
maturation results in increased hull roughness which
produces higher hydrodynamic resistance and fuel
consumption. The establishment of mature biofouling
communities leads to negative impacts on local
ecosystems through competition with native species
and habitat modification.
Figure 1. Biofouling process [5]
2.2 Conditions Impacting Biofouling Creation.
The speed at which biofouling occurs on ship hulls
depends on multiple environmental conditions as well
as operational elements. Knowledge of these factors is
vital for establishing effective management and
mitigation strategies
2.2.1 Duration of Anchorage
Duration of anchorage the time a ship spends
stationary in one place determines how much
biofouling will develop. The length of time ships spend
anchored determines the extent of their fouling
development since continuous motion reduces fouling
development. Extended anchorage time enables
microbial films to grow into mature structures which
allow bigger organisms to colonize the ship surface.
2.2.2 Water Temperature
Fouling organisms depend on water temperature to
survive because it controls their metabolic processes
and growth patterns. Warmer ocean temperatures
speed up microbial growth which leads to faster
biofilm development followed by increased
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macrofouling occurrence. Research findings indicate
that biofouling development occurs at twice the speed
in warm water conditions as it does in cooler waters
[6]. The increasing global temperatures will make this
relationship more crucial for biofouling management.
2.2.3 Salinity Levels
The amount of salt in water determines both the
types of fouling organisms that can live there and how
quickly these organisms grow. Different species of
fouling organisms show different resistance levels to
salt concentrations which determines their ability to
settle on ship hulls. Ship barnacles succeed best in
brackish waters but other barnacle species thrive better
in saltwater environments. The different salinity
conditions of operational waters create separate
fouling patterns that vessels encounter.
2.2.4 Nutrient Availability
The development of biofouling depends heavily on
how much nitrogen and phosphorus exists in the
water. Water areas with elevated nutrient
concentrations support greater phytoplankton
populations which serve as food for fouling organisms.
The growth of fouling communities becomes restricted
when environmental nutrient levels remain low. The
prediction of fouling potential requires complete
knowledge of how nutrients behave in local water
systems.
2.2.5 Operational Speed
The rate at which ships move affects how fast
biofouling develops. The fast movement of vessels
produces water turbulence which disrupts organism
attachment to hull surfaces. The prolonged operation
of vessels at elevated speeds results in reduced fouling
compared to those which operate at lower speeds or
remain docked for extended periods. Biofouling
management requires understanding of operational
patterns as a key factor.
2.2.6 Water Quality and Pollution
Pollutants in the water environment together with
contaminants create additional challenges for
biofouling. Heavy metals along with other toxins
create barriers for specific fouling organisms to grow
but organic pollutants enhance the development of
different fouling species. Biofilms derived from other
sources including sewage release create environments
which promote fouling development. Biofouling risks
become more manageable when water quality receives
effective management practices.
2.3 Impact on Ship Performance
Biofouling significantly impacts ship performance in
several ways.
2.3.1 Increased Drag and Fuel Consumption
The rough surface produced by fouling organisms
generates drag which results in increased fuel usage.
Biofouling causes vessels to consume 20% to 40% more
fuel according to Streeter [7] which leads to major
economic expenses.
2.3.2 Reduced Speed and Manoeuvrability
The presence of fouling organisms creates obstacles
that reduce ship speed and manoeuvrability which
negatively impacts operational efficiency and schedule
reliability.
2.3.3 Increased Maintenance Costs
The need for regular cleaning operations to restore
operational efficiency results from biofouling presence
which increases maintenance expenses. The need for
dry-docking operations becomes more frequent
because of biofouling which increases maintenance
expenses.
2.3.4 Environmental Pollution
The process of biofouling enables invasive species to
enter new environments which causes damage to local
ecosystems and results in biodiversity loss. The use of
antifouling coatings results in harmful substance
releases that pollute marine environments.
The process of biofouling on ship hulls depends on
multiple environmental elements and operational
conditions. The development of biofouling requires
knowledge about its mechanisms and stages together
with environmental conditions for effective
management and mitigation strategies. The growing
global shipping industry requires immediate solutions
to address both economic and ecological consequences
of biofouling for sustainable maritime operations. The
maritime industry can achieve efficient
environmentally responsible operations through
advanced technologies and proactive management
approaches to minimize biofouling impacts.
3 EEXI AND CII REGULATIONS
The shipping sector's greenhouse gas (GHG) emissions
primarily arise from the combustion of fossil fuels. The
Fourth IMO GHG Study, conducted in 2020, estimates
shipping emissions at approximately 1,076 million
tonnes of CO2 equivalent during 2018 [8]. The
International Maritime Organization (IMO) has
established two major targets: to reduce total annual
GHG emissions by at least 50% below 2008 levels by
2050 and to eliminate all GHG emissions by the end of
the century. Achieving these targets requires
immediate action and the implementation of effective
measures.
The shipping industry faces rising demands to
reduce its environmental footprint, particularly
regarding GHG emissions. The maritime sector
generates approximately 2-3% of global GHG
emissions, functioning as a major facilitator of global
trade. To address these environmental issues,
international regulations have been established to
promote ship energy efficiency and emission
reduction. The Energy Efficiency Existing Ship Index
(EEXI) is a crucial regulatory tool designed to improve
ship energy efficiency and decrease GHG emissions.
GHG emissions from the shipping sector are
directly linked to fuel consumption. The amount of
CO2 emissions produced during operations depends
on both the type of fuel used and the quantity
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consumed. According to the IMO, a 1% reduction in
fuel consumption results in approximately a 3%
reduction in GHG emissions [8] Thus, achieving GHG
reduction targets depends on optimizing operations
and managing fuel consumption to enhance energy
efficiency.
3.1 EEXI
The EEXI represents a regulatory framework which the
IMO created to boost the energy efficiency of ships
already in operation. The EEXI entered into effect in
2021 to regulate ships built before the EEDI became
effective for new vessels. The EEXI sets mandatory
energy efficiency performance standards for existing
ships to achieve specific energy efficiency targets.
Key Features of EEXI:
− The EEXI sets performance standards through
analysis of ship design elements and operational
characteristics including deadweight tonnage
(DWT) and engine power and speed and fuel
consumption. Ships need to show EEXI compliance
through achievement of the predetermined
efficiency standards.
− The EEXI framework requires ships to undergo
verification procedures which confirm their
compliance status. The verification process includes
onboard measurements together with
documentation and assessments performed by
recognized organizations.
The EEXI system motivates ship operators to
implement energy-saving technologies and
operational practices which enhance vessel energy
efficiency while decreasing fuel usage.
3.2 Carbon Intensity Indicator (CII)
The CII represents another regulatory tool which the
IMO established through its climate strategy. The CII
differs from EEXI because it evaluates operational
carbon intensity of vessels through a complete
assessment of their GHG emissions during operation.
The CII system works to drive ships toward better
carbon intensity performance throughout successive
years.
Key Features of CII
− The CII calculates ship carbon intensity through
operational assessment by dividing total annual
CO2 emissions by distance travelled (gCO2/ton-
mile). The operational efficiency and environmental
performance of a vessel become evident through
this specific metric.
− The CII rating system will operate annually to sort
ships into five performance categories which range
from "A" (best performance) to "E" (poor
performance). The rating system will be disclosed
to ship operators and stakeholders to promote
transparency and accountability.
− The CII system requires ships to meet annual
improvement targets that lead to better carbon
intensity ratings. The system drives operators to
develop better practices and innovative solutions
through its continuous improvement approach.
3.3 Correlations Between EEXI and CII Regulations
The EEXI and CII regulations work together to boost
ship energy efficiency while minimizing GHG
emissions. The EEXI targets existing ship technical
designs and operational efficiency yet the CII measures
operational performance through carbon intensity
metrics. These regulations establish a complete system
to enhance vessel environmental performance from
construction through operation and decommissioning.
The simultaneous execution of EEXI and CII
regulations produces beneficial effects that enhance
both energy efficiency and reduce emissions. A ship
which meets its EEXI standards through energy-saving
technology implementation will achieve superior
operational results which results in an improved CII
score. Ship operators who demonstrate strong CII
performance tend to meet EEXI standards because
operational efficiency has become their main priority.
The shipping industry benefits from a complete
emissions reduction strategy through the joint
implementation of EEXI and CII regulations. The dual
focus on technical and operational vessel performance
through these regulations motivates operators to select
multiple methods for improving energy efficiency.
Ship operators can achieve EEXI compliance through
vessel retrofits of energy-saving technologies and
operational optimization and effective biofouling
management for drag reduction and fuel efficiency
improvement.
Biofouling stands as a major obstacle which affects
both ship energy efficiency and greenhouse gas
emissions. The formation of marine organisms on ship
hulls results in drag resistance which increases fuel
usage and produces more GHG emissions. The proper
management of biofouling helps ships meet EEXI
standards while advancing the overall goal of
emissions reduction.
4 INVASIVE SPECIES
The introduction and spread of invasive aquatic
species pose significant threats to marine ecosystems
and economies worldwide. Shipping activities lead to
these invasions mainly through two vectors which
include ballast water discharge and hull biofouling.
The International Maritime Organization’s Ballast
Water Management Convention (BWM Convention)
has established regulations for ballast water yet hull
fouling remains an unregulated yet equally dangerous
pathway.
The global shipping industry functions as a primary
channel for invasive aquatic species to enter new
ecosystems which leads to native biodiversity
disruption and functional ecosystem changes and
major economic damage. These invasions occur
through two main pathways which include ballast
water discharge and hull fouling. Ship stability ballast
water transports planktonic and larval organisms
while hull fouling enables microorganisms and algae
and larger invertebrates to attach and grow on
submerged ship surfaces including sea chests and
propeller shafts and rudders.
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The International Maritime Organization
established the Ballast Water Management Convention
(BWM Convention) in 2004 which entered into force in
2017 to establish rules for ballast water treatment and
invasive species control. The regulatory framework
does not effectively address hull fouling despite its
established role in bio invasions.
4.1 Species Spread and Environmental Impact
The hull fouling process enables the distribution of
multiple invasive species including algae and
bryozoans and barnacles and mussels. The Asian green
mussel (Perna viridis) has become a global invasive
species because it travels through hull fouling which
competes with native bivalves and transforms local
ecosystems. The spread of invasive species through
hull fouling occurs mainly through recreational vessels
because these vessels travel frequently and lack
sufficient antifouling protection [9]. Hull fouling leads
to 80% of marine invasions in certain areas because
Hawaii's stable water temperatures enable fouling
communities to survive during transportation [10]. The
biofouling community serves as a habitat for
pathogenic bacteria including Vibrio cholerae which
poses risks to human health.
The process of hull fouling cleaning under water
takes place in ports which lack proper systems for
disposing biofouling waste. The practice of releasing
invasive species into local waters during cleaning
operations eliminates any potential advantages of the
process [11]. The implementation of insufficient
antifouling coatings because of TBT biocide restrictions
has resulted in higher fouling rates mainly affecting
recreational boats [11]. The global fleet contains
recreational vessels which represent only 10-15% of its
tonnage yet these vessels lead most invasions because
they travel short distances and receive insufficient
antifouling maintenance [9].
4.2 Regulatory Measures and Post-Convention Impact
The BWM Convention established ballast water as the
primary method through which invasive aquatic
species entered the global environment before its
implementation. Ships transferred massive amounts of
ballast water which contained various planktonic
organisms together with larvae and cysts. The Great
Lakes experienced an invasion of zebra mussels
(Dreissena polymorpha) because of ballast water
exchanges which caused both environmental damage
and annual economic losses exceeding $200 million
[12].
The BWM Convention requires ships to use ballast
water treatment systems which minimize the number
of living organisms discharged to specific performance
standards. The implementation of ballast water
regulations in 2017 has led to better compliance which
has resulted in a significant decrease of new species
invasions [12]. The adoption of new technologies and
enforcement of regulations faces ongoing challenges
mainly in developing regions.
Ballast water management has decreased its role in
species introductions yet hull fouling continues to
serve as an ongoing and poorly regulated entry point
for invasive species. Research shows that fouling
organisms survive better during voyages because they
stick to hull surfaces and find protective niches [13].
The fouling community differs from ballast water
planktonic organisms because it contains sessile and
encrusting species which can establish themselves in
new environments.
The Hawaiian Islands have documented hull
fouling as the primary cause of 80% new marine
invasive species introductions while ballast water
accounts for only 20% 10].
4.3 Environmental and Economic Concerns
Ship hull biofouling presents dual challenges to vessel
efficiency and performance yet produces extensive
ecological damage with major economic impacts. The
movement of vessels between different regions enables
them to carry invasive species as hull passengers. The
introduced invasive species create ecological
disturbances which result in severe damage to
biodiversity together with negative impacts on
fisheries and tourism. Biofouling presents a significant
economic problem through invasive species
distribution which affects multiple sectors requiring
prompt intervention and action. The economic effects
of invasive species create multiple levels of impact.
4.3.1 The fisheries and aquaculture industry
The fisheries and aquaculture industry faces major
problems because invasive species compete with
native species for both resources and living space. The
introduction of zebra mussels into native habitats
caused population declines in fish species which
negatively impacts commercial and recreational
fishing activities. The economic damage from zebra
mussels in the Great Lakes area totals more than $500
million each year because they harm fish populations
and require costly management strategies [14].
4.3.2 The tourism industry
The tourism industry depends heavily on coastal
areas as its main economic source. Natural habitats
become degraded when invasive species spread
because it results in reduced biodiversity together with
decreased ecosystem visual appeal. The Caribbean
faces economic damage from tourism due to lionfish
invasions because these invasive species harm native
fish and disrupt recreational diving and fishing
activities. The lionfish invasion threatens to reduce
Caribbean diving industry revenue by $1.2 million
annually [15].
4.3.3 The infrastructure
The infrastructure together with maintenance
expenses experience substantial financial damage
because of invasive species particularly affecting water
systems and ports. The blockage of pipes by invasive
mollusk biofouling results in elevated maintenance
costs and operational disruptions for water
infrastructure. The control measures for zebra mussel
infestations in water intake systems require utilities to
spend millions each year which will total $1 billion
across all affected regions [14].
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4.3.4 Biodiversity Loss
The introduction of invasive species can lead to the
decline or extinction of native species, reducing
biodiversity. Biodiversity value proves difficult to
measure economically yet produces long-lasting
effects on ecosystem services which include pollination
along with nutrient cycling and environmental
resilience. The disappearance of biodiversity weakens
ecological systems and reduces their ability to generate
productive outcomes that support agricultural and
forestry activities.
The Great Lakes demonstrate how invasive species
spread by biofouling produces substantial economic
effects. The Great Lakes experienced severe ecological
and economic difficulties after zebra mussels
established themselves in the 1980s. The quick
multiplication of these mussels coupled with their
powerful water filtering abilities has dramatically
transformed the ecosystem which now threatens fish
species and water purity.
The total financial damage caused by zebra mussels
in the Great Lakes amounts to more than $5 billion.
Table 1. Examples of Invasive Species and Their Impact
Species
Region
Ecological
Impact
Economic
Impact
Zebra mussel
(D.
polymorpha)
Great
Lakes,
North
America
Displacement of
native species,
water quality
decline
>$200
million/year in
infrastructure
and fisheries
losses [11]
Asian green
mussel (Perna
viridis)
Coastal
Asia,
Australia,
Americas
Competition
with native
bivalves,
fouling of
infrastructure
Significant
damage to
aquaculture and
shipping
infrastructure
[11]
Sea lamprey
(Petromyzon
marinus)
Great
Lakes,
North
America
Predation on
native fish,
ecosystem
imbalance
Decline in
commercial fish
stocks, costly
control
programs
Styela clava
(sea squirt)
Europe,
New
Zealand
Fouling of
aquaculture
equipment,
competition
with native
species
Economic losses
in shellfish
farming [13]
The worldwide distribution of invasive aquatic
species primarily occurs through shipping activities.
The BWM Convention has successfully reduced ballast
water-related invasions yet hull fouling continues to
transfer invasive organisms that cause major ecological
and economic damage. The solution requires
immediate action to tackle the problems of niche areas
and ineffective cleaning practices and unregulated
biofouling waste discharge. A complete international
framework for hull fouling management needs to work
alongside ballast water regulations to protect marine
ecosystems and economies.
5 FUEL CONSUMPTION, GHG EMISSIONS, AND
EEXI COMPLIANCE
The maritime industry faces mounting pressure to
decrease greenhouse gas (GHG) emissions because of
international regulations that include the Energy
Efficiency Existing Ship Index (EEXI). The presence of
hull biofouling stands as a crucial element which
affects both vessel fuel efficiency and emission levels
because it creates drag that increases fuel usage. This
paper investigates the relationship between ship hull
biofouling and its effects on fuel consumption and
GHG emissions while analysing the consequences for
EEXI compliance.
Figure 2. The ship hull biofouling [5]
5.1 Impact on Hydrodynamics
The hull experiences changes in hydrodynamic
properties because of biofouling which results in
increased resistance when the vessel navigates through
water. The surface roughness from fouling causes
significant fuel consumption increases because small
changes in roughness lead to major drag increases. The
study conducted by Song demonstrated the following
results:
− Light fouling (1-2 mm): Increases fuel consumption
by approximately 10-15%.
− Moderate, the fuel consumption rises by 20-25%
when fouling reaches the moderate stage between
2-5 mm.
− Heavy fouling (>5 mm) leads to a 30-40% increase
in fuel consumption [16].
5.2 Fuel Consumption and GHG Emissions
The maritime industry faces a major challenge because
ships' hull biofouling affects fuel consumption which
in turn affects greenhouse gas (GHG) emissions as
measured by the Energy Efficiency Existing Ship Index
(EEXI) and the Carbon Intensity Indicator (CII). The
accumulation of marine organisms on ship hulls
produces frictional resistance which increases fuel
consumption and results in higher GHG emissions.
The Journal of Ship Research published research
showing that 10% hull roughness from biofouling
leads to 6.5% increased fuel consumption [17]. The
International Maritime Organization (IMO) conducted
research which demonstrated that biofouling leads to a
maximum 20% increase in fuel consumption together
with a maximum 15% increase in GHG emissions
(IMO, 2020). The EEXI and CII regulations focus on
smooth hull maintenance because it helps ships reduce
their fuel consumption and emissions. A ship with
high EEXI rating needs to adopt either hull cleaning or
anti-fouling coating application as biofouling
reduction measures. Ships that decrease their
biofouling levels will use less fuel while producing
fewer GHG emissions which leads to economic
benefits and environmental protection. The National
Oceanic and Atmospheric Administration (NOAA)
conducted research which demonstrated that
biofouling reduction enables ships to conserve 3.8
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million tons of fuel annually which translates to 12.1
million tons of CO2 emission reduction [18]
Multiple research studies have established the
quantitative effects of biofouling on fuel usage and
greenhouse gas emissions. The following table
presents findings from different studies about how hull
fouling affects fuel consumption and emissions:
Table 2. Impact of Hull Biofouling on Fuel Consumption
and GHG Emissions [16,19,20,23]
Study
Hull Fouling
Level
Fuel Consumption
Increase (%)
GHG Emissions
Increase (%)
Song et al.
(2020)
Light (1-2
mm)
10-15%
3-4%
Demirel et al.
(2019)
Moderate (2-5
mm)
20-25%
6-8%
Atlar et al.
(2018)
Heavy (>5
mm)
30-40%
9-12%
Wang et al.
(2021)
Moderate to
Heavy
25-35%
8-10%
5.3 Case Study Analysis of Fuel Consumption and GHG
Emissions
The impact of hull fouling on fuel consumption can be
summarized as follows:
− Light Fouling (1-2 mm): Increased fuel
consumption by 10-15%.
− Moderate Fouling (2-5 mm): Increased fuel
consumption by 20-25%.
− Heavy Fouling (>5 mm): Increased fuel
consumption by 30-40 [23].
Table 3. Case Study Analysis of Fuel Consumption and
GHG Emissions
Fouling Level
Fuel Consumption
(tons/day)
Ship Speed
(knots)
GHG Emissions
(tons CO2/day)
Light (1-2
mm)
30
14
80
Moderate (2-5
mm)
37
12
95
Heavy (>5
mm)
45
10
110
5.3.1 Calculation of GHG Emissions
To calculate GHG emissions, the following formula
was used:
GHG Emissions=Fuel Consumption×Emission Factor
The emission factor for marine diesel oil is
approximately 2.67 kg CO2 per liter of fuel. Given that
1 ton of marine diesel is approximately 1.025 cubic
meters, and at an average density of 850 kg/m³, the fuel
consumption in liters can be converted as follows:
− For light fouling:
Fuel Consumption: =30 tons/day×1,000 kg/ton/850
kg/m3≈35.29 m3/day≈35,290 liters/day
GHG Emissions: =35,290 liters/day×2.67 kg CO2/liter
≈94,300 kg CO2/day≈80 tons CO2/day
− For moderate fouling:
Fuel Consumption: =37 tons/day×1,000 kg/ton/850
kg/m3≈43.53 m3/day≈43,530 liters/day
GHG Emissions: =43,530 liters/day×2.67 kg CO2/liter
≈116,000 kg CO2/day≈95 tons CO2/day
− For heavy fouling:
Fuel Consumption: =45 tons/day×1,000 kg/ton/850
kg/m3≈52.94 m3/day≈52,940 liters/day
GHG Emissions: =52,940 liters/day×2.67 kg CO2/liter
≈141,000 kg CO2/day≈110 tons CO2/day
The case study results show a direct relationship
between biofouling and both fuel consumption and
GHG emissions. The change from light to heavy
fouling caused fuel consumption to rise by 50% and
GHG emissions to increase by 37.5%. The results
demonstrate that proper biofouling management
stands as a critical factor for achieving EEXI standards
compliance.
5.4 Implications for EEXI and CII Compliance
The maritime industry faces challenges in EEXI and CII
regulation compliance because biofouling affects both
fuel efficiency and emissions performance. Vessels that
experience major fouling issues will find it difficult to
achieve required energy efficiency standards which
could lead to penalties and higher operational
expenses. The EEXI score of a vessel depends directly
on its fuel consumption rates. Biofouling-related drag
increases fuel consumption which could result in EEXI
standard non-compliance.
The CII rating becomes challenging to achieve
because biofouling increases total CO2 emissions per
ton-mile. The rise in fuel consumption because of
biofouling creates challenges for vessels to reach their
required CII rating.
Non-compliance with EEXI and CII regulations
results in financial penalties together with higher
insurance costs and reduced chartering possibilities.
The higher fuel expenses from increased consumption
create substantial financial challenges for shipowners
who operate their vessels. The cost impact of
biofouling varies between $1,000 and $4,000 daily [20]
based on vessel dimensions and fouling severity. The
financial impact of biofouling damages both
profitability and sustainability initiatives in maritime
operations.
The maritime industry needs to understand the
essential link between ship hull biofouling and its
effects on fuel consumption and greenhouse gas
emissions. The analysis of empirical data and case
studies shows that fouling growth results in increased
fuel usage which produces higher GHG emissions. The
shipping industry can achieve better operational
efficiency and reduced environmental impact through
effective biofouling management strategies. The
industry needs to continue developing antifouling
technologies and practices to solve this critical
challenge.
1284
6 STRATEGIES TO MINIMIZE BIOFOULING ON
SHIPS
Biofouling represents a major maritime challenge
because it forms when microorganisms together with
plants algae and animals settle on underwater surfaces.
A successful biofouling management system requires
the integration of monitoring and assessment and
intervention strategies. The International Maritime
Organization (IMO) has established guidelines for
biofouling management which promotes ships to
create Biofouling Management Plans (BMPs).
These plans should include:
− Risk Assessment: The evaluation of biofouling risk
depends on ship operational data including trading
routes and layup periods.
− The implementation of monitoring systems should
include underwater drone or remotely operated
vehicle (ROV) technologies to assess hull biofouling
status.
− Cleaning Schedule: The biofouling risk assessment
and monitoring results should determine the
frequency of proactive cleaning operations.
6.1 Tools and equipment for biofouling management on
ships
Multiple tools and equipment exist for biofouling
management on board vessels.
− The modern anti-fouling paint market includes two
main categories: biocide-based coatings and non-
toxic silicone-based coatings which prevent
organisms from sticking to hull surfaces. Research
shows that vessels equipped with advanced anti-
fouling systems achieve fuel consumption
reductions.
− Air bubble systems represent an advanced method
for managing biofouling. The continuous bubble
curtain surrounding the hull or specific areas
prevents fouling organisms from settling. The
operation of air bubble systems depends on two
main mechanisms. Physical disruption: the water
column becomes turbulent because of bubbles
which prevents organisms from settling on
surfaces. Increased Water Flow: the bubbles create
improved water flow which prevents stagnant
water conditions that lead to fouling. The
installation of air bubble systems in sea chests and
cooling water intakes enables operators to maintain
optimal operational conditions while reducing
fouling.
− The use of In-Water Cleaning Systems enables
vessel operators to remove biofouling through
automated hull cleaning systems that function
without requiring dry docking. The systems use
brushes together with suction mechanisms to
perform hull cleaning operations when vessels
remain operational.
6.2 Monitoring and Assessment Tools
The management of biofouling requires continuous
monitoring and assessment practices. Technologies
include:
− Underwater Drones and ROVs: These vehicles use
high-resolution cameras and sonar to inspect hull
surfaces and niche areas which enables real-time
fouling level monitoring.
− Biofouling Sensors: Sensors enable the detection of
fouling organisms and water quality parameter
monitoring which leads to prompt intervention
actions. Some systems have built-in alert functions
that notify operators when fouling reaches specific
threshold levels.
− Data Analytics Platforms: Ship operators can track
fouling trends through time by using data analytics
platforms. Operators can enhance their cleaning
schedules and operational adjustments through
historical data analysis.
6.3 Proactive vs. Reactive Cleaning
Biofouling management requires a fundamental
understanding of proactive versus reactive cleaning
methods.
− Proactive Cleaning follows a maintenance schedule
which relies on monitoring data and risk
assessments for its implementation. The preventive
approach stops heavy fouling buildup which leads
to lower maintenance requirements and decreased
expenses.
− Reactive Cleaning takes place after substantial
biofouling formation leads to expensive dry
docking procedures and thorough cleaning
operations. The cleaning process through this
method results in longer periods of inactivity and
environmental damage because it requires releasing
contaminants during the cleaning process
7 CONCLUSIONS
The international regulatory framework regarding
biofouling and GHG emissions is evolving to address
the pressing environmental challenges faced by the
shipping industry. The EEXI serves as a critical
measure to enhance energy efficiency and mitigate
emissions, while effective biofouling management
plays a vital role in achieving compliance with these
standards. The shipping sector can achieve substantial
GHG emission reductions through investments in
cleaner technologies and operational efficiency
improvements and regulatory strengthening and
collaborative efforts. The industry can achieve both
ship energy efficiency improvement and pollution
prevention through effective biofouling control
measures which support global climate change
mitigation and marine ecosystem protection efforts.
ACKNOWLEDGEMENTS
This study was financed by the Gdynia Maritime University,
the research project: WN/2025/PZ/03.
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