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Summer 2007

Article selected from our quarterly magazine dedicated to the largest and most luxurious boats with information, interviews, technical articles, images and yachting news



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Article by
Andrea Mancini

"Green Star" notation for pleasure craft or certification of low environmental impact yachts

Natural ecosystems are deteriorating at an astonishing rate, unprecedented in the history of the human species. This is demonstrated with great clarity in the WWF's "Living Planet Report 2006": "Making changes that will improve our living standards and reduce our impact on nature won't be easy," said WWF International Director General James Leape, "but if we don't take immediate action the consequences will be certain and dire."


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Tackling this situation, which we'd often prefer to forget, is now a necessity also in the yachting world: increasingly stringent regulations in terms of polluting emissions and limited access to certain areas mean that owners and shipyards are increasingly obliged to install specific "antipollution" devices and employ technical solutions that take account of these new requirements. But above all there is increased awareness and a new sensitivity: the times are fortunately long past when everybody dumped stuff into the sea indiscriminately. Today the systems of management and collection of sewage and bilge water aboard pleasure craft are a reality and have been obligatory since 1998 when European Directive 94/25/CE came into force (which prescribes and governs the so-named CE marking for yachts).

So it's time for a change of attitude: no longer rules and limitations imposed and submitted to but a new mentality which is actively to the point. Nowadays there are shipyards and owners who are aware of the environmental impact problem of their yachts and want to go beyond the limits and rules imposed by the current, insufficient standards by adopting solutions that further reduce environmental impact and subsequent pollution.

This is what's behind the voluntary "GREEN STAR" notation.

On the basis of experience acquired in the merchant shipping sector and especially in the cruise ship sector (among which we point out certain Costa Crociere vessels and the Grimaldi ferry fleet) the Italian Shipping Register (RINA) has taken up the challenge of these years by putting itself forward as the world's first Classification Body to propose a standard - specifically for pleasure craft over 35 metres LOA - that guarantees the highest levels of environmental protection, with regulations that exceed what is prescribed by international regulations. The "Green Star" standard is therefore a notation that enriches a pleasure craft's class certificate, guaranteeing the use of technical solutions aimed at prevention of sea and air pollution, solutions that concern plant engineering aspects and operational type procedures. Indeed good environmental protection is a result, in equal measure, of technology and our own behaviour! Some owners and yards have already embraced these regulations and set out to produce the first ecocompatible yachts: the first yard to take up the challenge was Viareggio Superyacht, beginning in 2005 with the first yacht in the world to be designed in accordance with the criteria of environmental sustainability: the splendid 62 metre megayacht in steel and aluminium "Stella Maris", designed by architect Espen Oino. Launching is envisaged for November of this year and will be shortly followed by the launching of a twin ship that is already under construction.

The regulations of the "Green Star" standard basically derive from those of the MARPOL agreements, standards and prescriptions conceived for merchant vessels with uses and requirements decidedly different from those of a pleasure craft. Precisely for this reason - explains Mr Bennewitz, engineer and managing director of VSY - there was a long job of calibrating and fine tuning the MARPOL regulations to the specific requirements and features of pleasure craft. The work that translated these criteria into the "Green Star" standards notation was carried out by the RINA in close collaboration with shipyards. In particular VSY, as the first yard to design and build an ecocompatible yacht, collaborated actively and profitably with the RINA in translating these ecocompatible criteria into practical rules, rigorous but applicable.

But what does it mean concretely to apply the "Green Star" notation standards to a pleasure craft?

In applying these standards to a yacht like "Stella Maris" the VSY technical team did its utmost to find answers to new problems and requirements.

It's a long list. But even before the individual problems were tackled and the solutions found it was necessary - as VSY's Alex Jacopozzi explains - to consider the prescribed low environmental impact criteria right from the design phase. These requirements must in fact be integrated with the other standards followed in the building of such an important yacht. In a word, it's a question of implementing an integrated design involving environmental regulations, safety and quality, without however forgetting the owner's needs and tastes!

Going back to application of "Green Star" criteria in the building of "Stella Maris", in order to guarantee observance of certain prescriptions, the products and/or solutions identified and selected on the market were only (so to speak) those which guaranteed "Green Star" standards, such as for example: the engines and generator units have reduced emissions while the exhausts have a system that doesn't mix seawater coolant with exhaust gases, thus reducing water contamination. Moreover, all the thermomotors are equipped with a system of filtering and recirculation in the combustion of oil fumes. Ecocompatible antifouling paints and refrigerant gases were used in observance of the most advanced antipollution standards in force. The sacrificial anodes protecting the hull from galvanic currents are in an alloy with a very low percentage of zinc to reduce environmental impact. In order to avoid air and/or water contamination as much as possible, the fire-fighting system is of a water-mist type, without the use of gases or mixtures of any kind, and the refrigeration systems are closed circuit with heat exchange by way of the hull plates.

Ad hoc solutions were studied and developed in observance of other prescriptions, such as for example:

  • A monitoring system for real-time execution and checking of all operations that might cause pollution of air and water.
  • A power management system that gives maximum yield from the generator units.
The solutions adopted for treating all polluting liquids are complex and many sided, starting with grey and sewage water. In fact the "Green Star" standards, as engineer Paolo Moretti of the RINA Marine Yachting Division explains, prescribe a different evaluation and behaviour where sewage or grey water is or is not subject to a treatment defined as "advanced". If the yacht has no such "advanced" system then suitably sized collection tanks must be kept on board - in proportion to vessel size and number of people aboard - which may be emptied only ashore or while under way in areas not subject to environmental restrictions, but in all cases at least one mile from the coast. Whereas if the yacht has an "advanced" treatment system which ensures that the treated water contains pollutants below the levels shown in Table 1 then the water may be recycled for technical uses and washing and there is no need for collection tanks. The "Stella Maris" carries tanks for discharge ashore but also has an innovative and advanced purification system.

In designing a low environmental impact vessel it is very important to limit possible leakage of fuel, oil and oily bilge water. For example the "Green Star" regulations prescribe that these liquid container tanks must have a reduced volume, in function of vessel size, and must not be positioned in places potentially more exposed to collision and holing. Figure 1 shows how these tanks must be set at distance D, no less than 0.7 m. from the full load waterline, which is to say the part of the hull where collision with floating bodies is more probable with consequent leakage of pollutants. As for the treatment of oily bilge water there is a specific collection tank in which separation and purification take place: the sludge is collected in a special tank for discharge ashore while the purified water with oily content less than 5 ppm (a value lower than the 15 ppm prescribed by IMO standards) is dumped overboard. Moreover there's a special tank for collection of exhausted lubricant oil from engines and generators which is discharged ashore for reuse.

Lastly, solid organic and inorganic waste is treated with special care: first of all there is the "obligatory" procedure of differentiated collection aboard if the yacht is to be really of low environmental impact. To this end everything has been done to favour and facilitate this method, and in particular:

  • Organic waste discharge from the kitchen macerator is separated in such a way as not to flow into the grey water collection plant;
  • There's a waste compactor that compacts and freezes bags of waste ready to be stored in the special refrigerated cell for preservation;
  • There's a special refrigerated cell for the collection of solid perishable waste which is subsequently disposed of ashore;
Over and above these significant and costly modifications to be implemented aboard, to make a yacht ecocompatible on the basis of the "Green Star" prescriptions is also costly in terms of operational management. To keep in line with the "Green Star" ecological features means constant maintenance of antipollution apparatus which is also subject to yearly inspection by RINA inspectors. Aware of the greater burden involved in all this, as engineer Bennewitz explains, VSY delivers its yachts with the periodic visits included for 12 months. A sort of free "MOT" to set in motion the regular process of maintaining the ecological and class features of the vessel and - why not? - instilling the "environment friendly" habit also in the yachting world.

So what are the reasons behind "Green Star" yacht certification? What are the advantages as against the greater initial and management costs?

"Green Star" documents the owner's policy of respect for the environment. It gives shipbuilders and designers a precise and clear technical reference. It gives guests and passengers aboard a luxury yacht the idea of thoroughgoing respect for the environment they're sailing in. Lastly, to the authorities and organisations responsible for controlling and safeguarding the sea, it gives the certainty of having achieved high environmental performance.

To these reasons we may add others linked to the increasingly stringent rules found in national and international situations. For example in order to gain access to certain coveted areas of the sea - such as the nature reserves of Alaska or Yucatan - you must comply with certain prescriptions of the MARPOL agreements, which are also part of "Green Star" certification. Italy too is heading towards standards that divide vessels in accordance with their environmental impact, standards that privilege less polluting vessels. So sailing aboard a "clean" yacht not only gives you a clear conscience but is also wise! You have free access to places where polluting boats can no longer go.

Increased awareness of planet-polluting problems is necessary today if we want our planet to have an acceptable future! Just as it is now obligatory and necessary also in the yachting and luxury world to not only talk about but actually tackle the themes of the environmental impact of a yacht, of the lifestyle on board. And it would be a fine thing to hope that these marvellous yachts should be desired and imitated not only for their luxury and beauty, their design and high technology, but also for their new constructional and management solutions that respect the environment. And the budgets necessary for building and managing such ships permit investment in research into solutions like those adopted by VSY for "Stella Maris", solutions which are perhaps trend-setting and will become a must to imitate. So why shouldn't we envisage even small vessels with on-board water purifying systems and ecological propulsion? Technically speaking it isn't as impossible as it might seem: if a trend is set, a culture is spread, if the market demands it it'll soon be done! And perhaps this new culture will at last oblige us to seek a term analogous to bio- architecture in the sailing world, a world of boats that pollute increasingly less and are environment friendly right from the materials used for building them, which must be less polluting during production and be ecologically disposable and/or recyclable. We shall be obliged at last to face the problem of the environmental impact of fibreglass, a problem that is important today and cannot be put off till tomorrow.

The "Green Star" additional class notation is a first approach to this new culture, a first step in this direction. These Yachts will be sailing next year, and we hope that many more will join them.

The RINA "Green Star" notation

The "Green Star" standards are intended as a first approach to standards that should become obligatory for all vessels. They derive from the MARPOL standards agreed upon at the IMO "International Convention for the Prevention of Pollution From Ships" which since 1973 have defined and constantly updated the criteria and regulations to be observed with view to avoiding pollution of the sea (in fact MARPOL stands for Marine Pollution). The same standards are the basis for the additional class notation "Green Star" which the RINA drew up some years ago for merchant vessels.

The "Green Star" standards derive from the prescriptions of the so- named MARPOL annexes (in particular annexes I, IV, V and VI) but actually go beyond them, introducing further innovative and improving elements: for example, limitations to the size of oil and fuel tanks have been introduced to reduce spillage to a minimum in the case of leaks.

The slogan of a "Green Star" certificated yacht may be summed up as "Clean Sea, Clean Air". In fact the "Green Star" notation for the prevention of marine pollution envisages:

1) Plant for handling bilge water and any spillage of fuel into the sea. The plant consists of a series of structural fuel and lubricant tanks protected by a double skin hull, and of on-board antipollution equipment in the case of hydrocarbons spilling into the sea. Depending on the size of the yacht, there must be an anti gush-back system with sensors and alarms, a preseparation and decantation tank for bilge water and emergency procedures against spillage of fuel into the sea.

2) Modern, technological plant for treatment of grey water and sewage, designed and built according to international standards, consisting also of storage tanks for treated sewage and grey water, sized to capacities suitable for 2-4 days. Periodic analysis of the effluents is also envisaged.

3) The quickwork of the hull must be painted with antifouling paint that does not contain TBT (a pesticide harmful to marine fauna) .

4) Deposits and double bottoms for ballast water must be managed with view to avoiding contamination of the water.

5) Separate collection of on-board waste is envisaged, with refrigerated cells for preservation and operational procedures for controlled disposal and recycling.

Requirements for the prevention of air pollution are as follows:

1) Gases that damage the ozone layer are prohibited. Only ecocompatible refrigerant gases are allowed on board (which do not damage the ozone layer and have low greenhouse effect). Measures must be taken to prevent leakage of refrigerant gas.

2) Internal combustion engines for propulsion must be designed, built and certificated in accordance with international standards that limit emission (SOx, NOx). The yacht must use low sulphur content fuel.

3) Periodic exhaust fume analysis is required for fine dust particles.

These in brief are the requirements for beginning to sail the sea in a more responsible way.

The "Green Star" additional class notation is assigned by the RINA to pleasure craft over 35 metres. It is renewed with class every 5 years but checked every year.

Water purification aboard

An innovative and advanced device for treating sewage and grey water is installed aboard "Stella Maris". Purifying is carried out by a process that is technically defined as biological-aerobic-dynamic. The plant was created by T.A.N. s.r.l. - TECNOLOGIA AMBIENTE NAVALE ( a company specialised in on-board environmental protection technologies and capable of tackling, in integrated and innovative terms, situations related to the new technologies for treatment and control of liquid, solid and gaseous waste. T.A.N., which has already created advanced liquid waste treatment plant aboard many civilian and military vessels, has also designed and fine-tuned small size plant suitable for pleasure craft. The company offers specific, global consultancy for purchase, during the building phase of "GREEN STAR" vessels, and subsequent maintenance. Fausto Strozzi, engineer and proprietor of TAN, gave us a detailed description of the grey water and sewage purification plant installed aboard "Stella Maris", a plant which with the BIODISK FVN system can treat up to 4000 litres daily. The liquid from the sewage and grey water tanks, which have a special geometry that facilitates a first purification process (primary sedimentation), is conveyed into what is called a pre-oxidisation and mixing tank in which the first process of fermentation is triggered. The liquid is then transferred into the biological treatment plant proper which consists of a single block not much larger than a 1 metre cube. Here, by a simple process of oxidisation with supported biological growth, the biological purification treatment is carried out which takes place on more than thirty discs of 1 metre diameter rotating at roughly 10 rpm. On the surface of these disks, by cellular synthesis, the biomass which feeds on polluting substances is born, lives and dies, a biomass that increases in thickness, in function of how much pollutant there is, until it is detached by the centrifugal forces of rotation. The resulting biological muds, produced in quantities of about 50 litres/day, of which the solid part is only 3-4%, are extracted and put in the sewage tank where they function as biological process activators and are subsequently disposed of ashore. Whereas the water handled in this way undergoes another 3 treatments (secondary clarification, filtering to eliminate suspensions and surface-active agents, bacterial sterilisation) after which it can be confidently reused.

In brief, the main advantages of the BIODISK FVN® system are:

  • high purification efficiency;
  • capability to treat temporary hydraulic and organic overloads;
  • compact, small size and easy to install;
  • fully automatic control from the command unit;
  • easily run (specialised personnel unnecessary);
  • each part of the plant easy to inspect;
  • selected high quality materials mean top reliability;
  • unaffected by the movements of the vessel;
  • possibility of modular units.