Arbejdsrapport fra Miljøstyrelsen Nr. 27 2007 – Udvikling af funktionaliserede enzymer til selvpolerende skibs-bundmaling

Udvikling af funktionaliserede enzymer til selvpolerende skibs-bundmaling

Summary

This report is a follow up of a former report prepared to the Danish Environmental Agency under the EPA project number M 126 – 0380 ”Substitution of biocides with enzymes in ship hull paint”. The report contains two parts. Part 1 concerns the modification of enzymes so they can function and be active in organic solvents and test of this modified enzyme in paint on panels in sea water. Part 2 is describes testing non modified enzymes in paintings on test boats.

Part 1: Modified enzymes tested in paint on panels in sea water

A modification of the enzyme has been made to improve the compatibility in an organic solvent and change the hydrophobic status of the enzyme to a more lipophilic character to “keep the enzyme in the paint in longer period”.

Painted panels have been immersed in Ellsinore Harbour and Oslo Fjord. When the panels are compared on fouling intensity and the type of fouling, the rafts in Ellsinore Harbour and Oslo fjord shows the same tendencies.

The control panel without paint is without antifouling effect and is completely fouled early in the sailing season.

The control panels with the base paint added toxically biocides are as expected without fouling.

The other panels are all with enzyme paint with variation in fouling intensity. The fouling consists mainly of a bacteria layer and diatoms.

Increasing concentration of unmodified enzyme A from 5 % to 10 % in the control paint has no significant effect on the fouling intensity.

The enzyme modification has no negative impact on the effect of the enzyme activity in sea water as well as on the fouling. Both modifications E484 and E486 still have the ability to prevent barnacles and mussels from settlement.

The short enzyme modification E484 has a better efficacy than the longer form E486. It can be concluded that the incretion of the concentration of E484 from 5 % to 10 % in the paint do not have any visible effect on the fouling intensity. It can further be concluded that the enzyme paint in its present form can prevent fouling from mussels and barnacles in a sailing season. It is not clear whether the modification of the enzymes has been an improvement compared to the unmodified enzymes.

It can also be concluded that there can be produced solvent based paint with enzymes that has an effect on the fouling intensity over a sailing season.

Part 2

Preparing the modification of the enzymes took longer time than anticipated. In order not to waste a sailing season some yacht owners were contacted through Danish Sailing Association to test the previous formulation with unmodified enzyme in organic solvent paint Mark 5.

On background of the inspections of the yachts and the owners evaluation the following conclusions has been made.

Enzyme based test paint Mark 5

Enzyme based Mark 5 do not by function separates from the other standard products without enzymes and without biocides. In its present state the test paint can not live up to the expectations the sailors have to reasonable fouling free ship hull and keep the manoeuvrability.

Enzyme and water based test paint

A waterborne formulation of paint was prepared. This formulation included enzymes and was only tested on a single yacht in Ellsinore harbour.

It can be concluded that although the knowledge of enzyme and water based test paint antifouling effect are limited the yacht had less fouling than the other test boats. The degree of fouling was not unacceptable to the owner of the boat.

Before there can be made any conclusions further tests on boats in different harbours are necessary. Hereby a further investigation of the enzymes effect will be necessary.

The Danish Sailing Association still se the enzyme based paint technology as an alternative. The test results in 2005 are better than the results achieved in 2003. In the 2005 test there has not been any problems with the polishing rate and the amount of observed fouling on the boats has in general been low.

Due to the small difference in fouling on the control paint and test paint the better result can unfortunately not bee concluded to be caused only by enzymes.

Danish Sailing Association hopes that there still will be worked on the enzyme technology efficacy towards slime and algae with further tests to the benefit for the environment and the sailors.