Summary

Fortsat udvikling og test af TeredoStop

New, promising wood preservative against marine borers

New, promising wood preservative against marine borers

The results of the tests in the project ”Continued development and test of TeredoStop” substantiate the innovative and promising perspectives of TeredoStop which combines the solution (TS) and the method of impregnation. After further product development TeredoStop will have the potential to become an environmentally friendly alternative to the existing preservatives against borers in maritime woodwork.

At the same time the method provides a unique possibility for treatment of poles already in service with only minimal impact on the maritime environment.

Background and purpose

Background

Chemical protection of wood against marine borers (Teredo) is traditionally targeted at treatment of the wood with ingredients that are toxic and dangerous to the environment. This is why there is a large potential in developing new products and technologies, which can reduce the environmental impact on the maritime environment resulting from the use of such substances.

The present project - “Continued development and test of TeredoStop” - focuses on the development and documentation of the mode of operation and efficiency of specific technologies and methods, with the perspective to replace the traditional methods for prevention against borers and treatment of timber already damaged.

TeredoStop derives from an idea, where the problems caused by marine borers are viewed from a new angle. This has resulted in a chemical formulation, in which the active ingredient is granted the “EU Flower” - the symbol of the European Eco-label - as it is environmentally friendly. The labeling originates from another application, as the active ingredient has never before been used in relation to the present purpose.

The TeredoStop-concept combines the TeredoStop-solution and a new method for impregnating poles “inside-out”. This entails - as something completely new - that poles already in service can be treated and thus protected. Both elements of the technology are covered by patents (pending), and the solution as well as the method are developed and owned by Teredo Marine Protection ApS.

The project builds on previously obtained, positive results of tests of effectiveness and aims at contributing to an optimization and further development of the technologies with respect to functionality and method of impregnation.

Purpose of project:

c) Test and documentation of the function of TeredoStop (prevention and reduction of attacks by marine borers).

d) Test and documentation of the method of impregnation (Teredo-method) (retention and distribution in wood)

Research activities

The project was carried out between February 2007 and April 2008.

The activities included different laboratory experiments and field trials of impregnated materials in order to investigate the importance of composition of TeredoStop and the method of impregnation. All laboratory experiments - leaching tests, impregnation of poles etc. - were carried out by the Danish Technological Institute in Taastrup. All field trials of functionality, including impregnated wood items were carried out in harbours of Skagen and Rudkøbing.

Main conclusions

Testing of the functionality

Despite a certain degree of leaching, TS has been documented to be effective in preventing and reducing attacks of marine borers. As long as sufficient active ingredient is present in the specimens, there is a significant effect on attacks of marine borers.

TS continue to be effective at extremely low concentrations of active ingredient in the wooden items. After having solved the leaching issue, TS therefore seem to have the potential to become very effective against attacks of marine borers (Teredo).

Focus for future product development of the TS function should be on fixation of the product in the wood.

Testing of the impregnation method (Teredo-method)

By using the Teredo-method it is possible to impregnate 5 m poles of Scotch Pine (Pinus sylvestris) through the heartwood with TS.

Pressing liquid through heartwood (axial impregnation) in this way (Teredo-method), has not previously been done successfully.

Heartwood of Scotch Pine (Pinus sylvestris) is generally considered as one of the most difficult types of wood to impregnate (DS/EN 350-2). A significant proportion of the poles for maritime use are Norway Spruce (Picea abies), which is categorized in the same treatability class as heartwood of Scotch Pine. This emphasizes the potential usefulness of the method even further.

Focus of future developments of the TS-method should be on the development and optimization of the technology in order to increase the retention in the heartwood and the transport/movement from the heartwood out into the sapwood.

Project results

Selected results concerning testing of function

Table 1 and 2 show the correlation between average attack and content of active ingredient in TeredoStop (TS).

Table 1 - Correlation between average attack and content of active ingredient

in specimens exposed in Skagen Harbour for 6 month. Grey color in the same column indicates significant differences (p<0,05).

Treatment	Exposure site	Average attack		Index fore remaining active ingredient in the specimens
		No of borers	% of area attacked ^*
Untreated	Skagen	2,4 (±0,6) ^a	1,6 (±0,6) ^b	0
TS (5)	Skagen	1,8 (±1,2)	1,0 (±0,6)	20
TS (10)	Skagen	0,5 (±1,0) ^a	0,3 (±0,5)^b	420

* According to the rating in DS/EN 275

Note: Numbers in brackets indicate standard deviation. Same letter in the table indicates a Significant difference between the 2 cells (p<0,05, Student’s t-test).

Table 2 - Correlation between average attack and content of active ingredient of specimens exposed in Rudkøbing Harbor for 6 month. Grey color in the same column indicates significant differences (p<0,10).

Treatment	Exposure site	Average attack		Index fore remaining active ingredient in the specimens
		No of borers	% of area attacked ^*
Untreated	Rudkøbing	1,4 (±1,1) ¹	0,8 (±0,4) ²	0
TS (5)	Rudkøbing	1,6 (±1,7)	0,6 (±0,5)	30
TS (10)	Rudkøbing	0,6 (±1,0) ¹	0,4 (±0,5) ²	190

* According to the rating in DS/EN 275

Note: Numbers in brackets indicate standard deviation. Same numbers in the table indicate a significant difference between the 2 cells (p<0,10, Student’s t-test).

The number of attacks and the size of the attacked areas were significantly different from the non-treated control specimens to specimens treated with TS(10) in both harbours.

Selected results concerning testing of impregnation method

Figure 1 provides an overview of the most important results of the testing of the impregnation method (Teredo-method)

Figure 1 - Overview of distribution of TS through the pole when impregnated in the heartwood. The arrows represent the retention of TS in kg/m³.

Figure 1 - Overview of distribution of TS through the pole when impregnated in the heartwood. The arrows represent the retention of TS in kg/m³.

By employing the Teredo-method it was possible to impregnate poles of 5 m (diameter 20-30 cm) of Scotch Pine (Pinus sylvestris) through the heartwood with TS.

Scotch Pine - as well as Douglas Fir (Pseudotsuga sp) is according to DS/EN 350-2 regarded as some of the most difficult types of wood to impregnate with respect to the heartwood. Therefore these are very encouraging results, which has hitherto not been obtained by employing this method i.e. pressing liquid through heartwood (axial impregnation).

A significant proportion of the poles for maritime use are Norway Spruce (Picea abies), which - according to DS/EN 350-2 - is categorized in the same treatability class as heartwood of Scotch Pine. This emphasizes the potential usefulness of the method even further.