Ending the use of antifouling paints on boat hulls?

Lauantai 19.6.2021 klo 14:58 - Mikko Nikinmaa

A significant problem with boat and ship hulls is that barnacles and algae attach to them especially in marine environment and, in addition to aesthetic problem cause both increased fuel consumption and decreased maximal speed. Because of these problems, antifouling paints have been used to prevent the growth of organisms on hulls. The problem with the organisms growing on hulls is that they are both animals and algae. Thus, to be effective, the antifouling paints must kill every type of organism.

Paints containing organic tin compounds, especially tributyltin, were used in hulls until it was found that the compounds cause imposex and loss of fertility in oysters in areas close to boat harbours. In addition to these toxic effects, they can cause various other toxic effect at environmentally occurring concentrations. Because of this, paints with these antifouling compounds are banned throughout the world today. Since tributyltin breaks down in a few weeks in pure, oxygenated water in the presence of sunlight, it was thought that toxicity of organic tin compounds would disappear in a year or maximally two of their ban. However, it has now become clear that their toxicity persists for tens of years. This is due to the fact that the compounds are quite stable in anaerobic sediments for tens of years, and become available to aquatic organisms whenever the sediments are dredged.

The organic tin-containing paints have been replaced with copper-containing paints often with booster biocides such as Irgarol 1051 and Diuron. In the paints copper has usually the valency of one. Cu+ is by far more toxic then Cu2+, and the toxicity caused to the aquatic environment is close to that of the organic tin-containing paints. Furthermore, the toxic copper compounds can persist even longer than the organic tin compounds. Consequently, one should be able to stop using the toxic paints altogether.

One possible solution is attaching coating with miniature spikes on boat hulls. Such coating has been developed and has recently received a European Innovation Award. If and when the coating becomes a large-scale solution for antifouling in boat hulls, we may see the end of toxic antifouling paints altogether.

Kommentoi kirjoitusta. Avainsanat: tributyl tin, paints, aquatic toxicity, ship hulls

Environmental Effects of Shipping

Keskiviikko 15.1.2020 klo 15:44 - Mikko Nikinmaa

Close to 70 % of all trade is transported waterborne. In terms of carbon footprint this way of transport is much better than air or road traffic, but there are still several environmental consequences. In addition to carrying cargo, cruises are becoming more and more popular form of tourism. Currently, cruise ships (including ferries) constitute close to 15 % of the world’s total fleet. The environmental consequences of shipping have been reviewed by Jägerbrand et al. (Science of the Total Environment 695, 133647, 2019).

The first environmental problem is the use of marine heavy fuel oil as a source of energy in ships (and petrol in small boats). While the total fuel consumption is only a very small percentage (less than 0.5 %) of total oil use, the fuel has until recently contained very high sulphur oxide concentrations, so that at the time that European and American land-based industries and power plants have been required to remove sulphur oxides from their smoke because of the acid rain problem of 1970’s and 1980’s the ship fuel use has contributed 10-20 % of the world’s sulphur dioxide emissions. Now that European Union has put an upper limit to the allowed sulphur concentration first in the Baltic anIMG_20170802_0109.jpgd North Sea, because of their heavy shipping, the Finnish shipping companies and industries were screaming that such an increase in the transport costs (low-sulphur fuel oil is more expensive than high-sulphur one or alternatively removing sulphur dioxide from fumes cost). However, the EU directive has been in effect a couple of years now, and has not resulted in serious economic disturbances (this incidence, to me, shows the hypocrisy of environmental thinking of many policy makers, as soon as any imagined expenses are increased because of environmental actions, they cannot be tolerated). The World Maritime Organisation is now putting an upper sulphur limit to all maritime heavy fuel oil. But in the long run, one should be able to go to oil-free shipping. Effective wind turbines are developed, and some ships using them may soon sail in the world’s seas. With the use of oil, there are several types of oil spills. Although the shipwrecks with pronounced oil leakage have decreased, most harmful spills are ones in small scale: washing empty oil tanks, using lubricating oils etc. It doesn’t help the seabird losing its insulation and dying of hypothermia knowing that the spill was small.

Another traditional big problem has been the use of antifouling paints on ships. They are used to prevent the growth of organisms on ships, both barnacles and algae. The growth of organisms on ship hulls can increase fuel consumption more than 10 %. Because very different types of organisms are tergeted, the toxic agents must kill all forms of life. Tributyltin (TBT) chloride was initially the common toxic agent, because it was very toxic, but considered to break down in weeks. However, it was noticed in 1980’s that TBT caused imposex (females developed male penis and became infertile) in molluscs near boat harbours. This led to a complete ban of the compound, but it persist in anoxic sediments for tens of years, and there are consequently still toxic TBT concentrations in narrow and shallow shipping routes. The next generation of antifouling paints has used copper ion as the toxic compound. To increase the paint’s toxicity to photosynthetic organisms, herbicides such as diuron are added. Presently, it appears that leaching from the ship paints is the major source of copper in aquatic environment. Further, the problem that cannot be avoided is that antifouling paints must kill everything.

Another problem with ships is that their waste has been disposed to sea with “out of sight out of mind” mentality. This has included both toilet wastewater and solid waste. While in most cases the waste load is very small in comparison to the waste coming from land, the increased cruising activity in Arctic and Antarctic has made the waste from ships a major cause of pollution in these vulnerable areas. The problem could be solved simply by storing all the wastes onboard until visiting the next harbour. Shipping is also a major reason for the introduction of invasive alien species, largely when the tanks with ballast water are emptied. Filtration of water entering or leaving the tanks could suffice to prevent the introduction.

Ships also affect the coasts: the waves generated will erode coastal areas, and the sediments of shallow shipping routes will be affected. Little can be done to avoid this except to site-planning of the harbour. Since most of the harbours have established sites, their location cannot really be affected. Finally, shipping generates noise. In the aquatic environment noise travels much longer than in air, and may disturb the communication of fish and marine mammals. Again, little can be done to reduce noise as long as present type motors are the norm – sailing ships would be much quieter.

In conclusion, many of the environmental effects of shipping could be solved with modest expenses. In this, as in many other cases, applying environment-friendly solutions is more a question of will than of not being able to. One point about goods transport is that we should reduce it by changing to production nearby instead of production thousands of kilometers away to be environmentally friendly.

Kommentoi kirjoitusta. Avainsanat: antifouling paints, oil pollution, invasive alien species, waste management