As fuel costs continue to be a a key factor and ship owners and operators examine new strategies aimed at improving vessel operating efficiency, the options relating to investments in effective hull coatings are increasingly complex.
A new decision-making tool, developed by
International Paint, has been designed to assist ship operators as they face the challenge of choosing between different fouling control products by comparing both economic and environmental costs and benefits.
Eco Efficiency
Since the first oil crisis nearly 40 years ago, the world’s leading marine coatings manufacturers have developed a wide range of hull coatings designed to limit plant and animal growth on the underwater hulls of ocean-going ships and coastal vessels. Untreated, fouling growth creates significant additional hull resistance and, as a result, leads to higher fuel bills and increased emissions.
These coatings have been based on various technologies with ongoing research and development on the part of the world’s leading coatings companies enabling new and more effective products to be brought to market on a regular basis.
Coatings fall into two broad categories,
biocidal antifouling coatings and
biocide-free foul release coatings, each of which has subsets. Biocidal antifoulings – whether self polishing copolymers or controlled depletion polymers – all function by releasing active ingredients, biocides, into the marine environment, repelling organisms and thereby preventing their adhesion to ships’ hulls. Copper forms the basis for the most widely used biocides today.
The second group are biocide-free and are known generically as foul release coatings. Unlike biocidal antifoulings, they do not release any active ingredients into the marine environment but work on a purely physical basis using advanced polymer technologies. Again, there are subsets within the foul release grouping – some coatings are based on silicone technology; others are known as fluoropolymers. It is the development of these coatings on which more research and development is becoming focused. They have less environmental impact and are generally more effective.
The ongoing challenge facing owners and operators is to formulate an effective comparison between the relative costs and benefits of different fouling control products.
Effective hull coatings can have a notable impact on ships’ fuel consumption, with some of the most sophisticated foul release coatings typically cutting fuel use, and therefore greenhouse gas emissions in the form of carbon dioxide, by up to 9 percent.
However, any comparison between products is complex. Almost every coating comes with a different set of “user instructions”. Paints are applied in different dry film thicknesses, in varying numbers of coats, sometimes involving several different products which together make up the “paint scheme”; some must be blasted off and the hull re-coated regularly at docking intervals; others can be scrubbed clean and touched up; they have different application requirements and drying times; some work better at higher speeds, others are better suited to slower vessels.
Recognising the complexity of the decision-making process, International Paint developed an “Eco-Efficiency Analysis”, to be tailored specifically for use in the fouling control sector.
What is Eco-Efficiency Analysis?
The term Eco-Efficiency is defined as maximising efficiency while minimising environmental impact. Thus Eco-Efficiency Analysis, which is also known as Life Cycle Assessment, compares and contrasts the financial and environmental costs and benefits of different products providing the same customer benefit over their entire lifetime. It is a particularly useful process when comparing new products with competing products in the market, within both an economic and environmental framework.
Undertaking such an Analysis is covered by two ISO standards:
ISO 14040:2006 Environmental management – lifc cycle assessment: Principles and framework; and
ISO 14044:2006 Environmental management – Life cycle assessment: Requirements and guidelines.
In a fouling control context, the customer benefit was identified as optimising vessel efficiency by ensuring a clean underwater hull. The Eco-Efficiency Analysis supports the best decision-making, taking into account a broad range of variables including raw materials and energy consumption, through-life costs relating to maintenance, repair and replacement, the benefits of use through limiting marine fouling thereby reducing fuel consumption, and ultimately the costs of waste disposal and any end-of-life requirements.
The International Paint Eco-Efficiency Analysis
Three products were identified for consideration in the International Paint study which, company executives agreed, would require external management, full compliance with the ISO standards and sign-off by an independent third-party auditor.
The products consisted of:
• A standard copper containing biocidal antifouling;
• A foul-release coating based on silicone technology (
Intersleek 700);
• A foul-release coating based on fluoropolymer technology (
Intersleek 900);
However, each of these three products is a component within a paint scheme and therefore an analysis of each of the products involved in each scheme was required. Six separate coatings were assessed therefore, comprising the three finish coatings above, an anti corrosive epoxy coating, and an epoxy tie-coat and silicone tie-coat to ensure good adhesion between the foul release coating and the anticorrosive.
A sustainability consultant,
Tobias Boren, who works at
Akzo Nobel’s central Sustainable Development division in Gothenburg was asked to oversee the Eco-Efficiency Analysis, and the
Swedish Environmental Institute was retained to audit the Analysis and verify its conclusions.
The biocidal antifouling works by releasing biocides which repel fouling organisms and prevent them from adhering to the hull. The biocides in such coatings, however, leach out over time, reducing efficacy, and ships’ hulls must be re-coated at every docking.
Intersleek 700, a silicone-based foul release coating, works through the hydrophobic nature of its surface. This means that marine organisms can only stick to the surface weakly. No biocides are released into the marine environment but mechanical abrasion reduces coating efficacy over time, and the finish coat of this scheme needs to be refreshed every five years.
Intersleek 900, a fluoropolymer foul release coating, works through the very smooth and amphiphilic nature of its surface. Most organisms are repelled whilst those that do stick to the surface, do so only weakly. Once again, there is no release of biocides, mechanical abrasion reduces coating efficacy over time and the finish coat needs to be refreshed every five years.
The process for considering the life-cycle inventory for this product includes:
• the mining of copper ore – resources consumed, emissions, fuel used, human exposure, waste and cost
• transportation to factory – fuel used, emissions, cost
• processed into Cuprous Oxide – fuel used, emissions, land fill, human exposure, cost
• transported to paint factory – fuel used, emissions
• converted into paint – energy use, emissions, waste, human exposure
• product transported to drydock – fuel used, emissions
• paint applied to ship – environmental/human toxicity, fuel used, emissions, waste creation and disposal
• ship enters service – fuel savings, emissions savings, higher speeds, cuprous oxide dissolves into ocean
• ship drydocked - environmental/human toxicity, fuel used, emissions, waste creation and disposal
• ship re-enters service – fuel savings, emissions savings, higher speeds, cuprous oxide dissolves into ocean
The data gathering continues over the pre-determined period of analysis or until ultimate disposal.
The subject vessel
For the purposes of the Eco-Efficiency Analysis, a specific vessel was chosen – a 300,000 dwt Very Large Crude Carrier (VLCC) assumed to have a trading speed of 15 knots, an activity level of 80 percent and fuel consumption of around 100 tonnes of heavy fuel a day, leading to greenhouse gas emissions of 320 tonnes of CO2, six tonnes of SOx and 0.5 tonnes of NOx.
A coating life-cycle of 15 years was adopted during which time the VLCC would be coated three times – once when it was built, and twice more at subsequent drydockings. It was assumed that at the end of the 15 years, the ship’s hull would have to be fully blasted and all coatings renewed.
All of the data inputs relating to this tanker’s 15-year operation were then collated. These included, but were not limited to total environmental burden including energy consumption, acidification potential, photochemical ozone potential; global warming potential, specifically carbon dioxide emissions; through-life costs of paint, application, drydockings; operating costs, notably fuel consumption; and paint volumes.
The results provided the basis for a chart, the Overall Eco-Efficiency Assessment, mapping environmental impact on the x-axis and financial impact on the y-axis. The key result was as follows:
• Intersleek 900 was most effective, both financially and environmentally, principally because of the largest fuel savings and a corresponding reduction in emissions, and substantially reduced paint volumes.
The Eco-Efficiency Calculator – an interactive model
One of the aims of this initiative was to provide a means of comparing different antifouling products, potentially on the hulls of a broad range of ships.
Therefore, International Paint has devised an interactive model which can produce a tailored Eco-Efficiency Analysis based on information supplied by a customer for a specific ship.
The Eco-Efficiency Calculator is an Excel program which uses “Macros” to process data.
Entering variables relating to specific ships, including vessel particulars, fuel price, drydocking frequency and costs, surface preparation and costs, and coating costs over the stipulated period the model then calculates results including:
• Likely ship operating costs assuming the use of each coating over the period;
• Greenhouse gas, namely carbon dioxide, released in each scenario, affecting onshore global warming rates;
• Greenhouse gas released from vessel activity;
• Other relative data outputs, including paint volumes, waste tins, volatile organic compound (VOC) content, and biocide content.
The result is a chart in which relative operating costs and savings can be easily compared. The figures vary directly with assumed fuel price but the model is said to enable sensitivity analyses by adjusting other variables. This, in turn, enables identification of factors in hull coating equations that have the most bearing on ship operation over time.
