Tri-Perm Processes Ltd of Dundee, a business offshoot from the Scottish Institute for Wood Technology at the University of Abertay, has reported encouraging results from initial industrial-scale tests using fungus to colonise poles and thereby make them more permeable to preservatives.
While no industrial concerns have yet become formally involved in the research venture, Tri-Perm director Dr Alan Bruce has confirmed that the SMART-supported project has already aroused the interest of a major, as yet unnamed, British timber group.
The background to the experiments can be traced to the early 1990s when the Electricity Council was looking to satisfy its pole requirements with home-grown timbers. This ultimately led to a EUREKA project, involving the University of Abertay and Lignocell – an Austrian bio-technology company linked to the Technological University of Vienna – to improve the permeability of spruce to preservatives.
Researchers noted in their early studies that many species – including sitka spruce, Norway spruce and Douglas fir – did not permit full commercial exploitation because ‘the anatomical features of the timbers mean that, even when using pressure treatment systems, it is very difficult to achieve satisfactory penetration of preservative, particularly in the roundwood state’. For spruce in particular, the number, structure and condition of the pit membranes in the cells make the timber particularly impermeable, they pointed out.
Experiments conducted in the mid to late 1990s showed that careful selection of organisms and their application in a formulated product using a suitable delivery system had the potential to improve significantly the penetrability of spruce pole sections to subsequent conventional pressure treatment with creosote. This was achieved adopting relatively short incubation times and, in some cases, without any subsequent strength losses in the timber.
Indeed, work to date has concentrated on the use of the trichoderma fungus which is ‘able to open up pits in the timber and to increase flows from one cell to another without producing any decay,’ according to Dr Bruce.
Having successfully achieved increased permeability in wooden blocks, the experiments were subsequently extended to green logs of around 600mm in length and 100-120mm in diameter. Logs were rolled in an inoculum base and incubated in bags for four weeks, prior to being kiln dried and
creosoted. Subsequent analysis at the University of Abertay revealed that penetration depth had increased from 6mm to around 30mm. Dr Bruce observed: ‘It was exciting to get that increase in penetration – it was well beyond our expectations.’
At the end of the EUREKA project in the late 1990s, attempts were made to involve the business world in the further development of this treatment technique but, according to Dr Bruce, ‘they wanted commercial-scale certainty’. At this point, a £45,000 SMART Scotland award from the government – to which the University of Abertay added a further £15,000 of its own money – paved the way for a two-year project aimed at developing an industrial-scale process and at assessing its performance.
Tri-Perm Processes Ltd was formed late last year to pursue the project and currently comprises a team of three based at university buildings in Dundee.
Since then, a pilot plant designed and built by James Boyack and Sons of Fowlis in Angus has been trialled at Finn Forest BBH Ltd’s pole treatment yard at Leven in Fife. Under this technique, poles are first dressed and then introduced into the treatment plant via a series of trolleys to avoid manhandling. The 12ft-long treatment box allows for a completely sealed operation with a sterilisation system at one end comprising a manifold of nozzles for the even application of steam. Continuing through the treatment chamber at a rate of around 2m per minute, the pole cools down prior to application of a corn steep liquor solution via a nozzle and pump configuration. This diluted sugar solution, based around a relatively inexpensive by-product of the brewing industry, is designed to introduce both the fungal spores as well as necessary nutrients to encourage their growth. The majority of the drippage from this process is captured inside the treatment area for subsequent recycling. Poles emerging from the treatment chamber are both shiny and sticky to the touch.
During trials at the Leven yard, they were stacked under tarpaulins for a six-week period of incubation. Initial examination prior to ‘dry down’ and creosote treatment has revealed an encouraging degree of fungal colonisation in the poles although Dr Bruce has still expressed concerns about the uniformity achieved in the incubation stages.
He concluded: ‘We could not be more happy with how the plant handled the poles and we know we have got good fungal colonisation in some of the poles. Penetration of the trichoderma has been measured to 80mm but we don’t know yet whether we will get the same depth of creosote penetration. We did have some problems with the incubation stage – too high a temperature for the fungus has meant that the fungal growth has been patchy and uneven on some poles.’
While acknowledging that more work was required, Dr Bruce went on to insist: ‘We have identified some of the process problems and none of them is insurmountable – all of them can be remedied quite easily.’
The next stage of the project will involve creosoting some of the incubated poles to determine the level of penetration, while the remaining poles will be cut into smaller lengths and treated with CCA to assess the potential of this treatment route for fencing materials. Dr Bruce confirmed that the major industrial interest was focusing on use of the technique in treating sawn wood lumber.
While the first priority remained to complete tests and analyses on the pole material, Dr Bruce said he was aiming to conduct tests on sawn wood lumber possibly some time next summer. The incubation period required for sawn timber should be considerably shorter than the six weeks adopted for the poles, he anticipated.
Dr Bruce was also planning a small trial involving the treatment of 2m-long logs immediately following de-barking as part of the bid to ‘iron out difficulties encountered in the initial tests’. But more immediately, Tri-Perm Processes was hoping to extend testing of the process by the end of November from sitka spruce to Douglas fir. As well as demonstrating the applicability of this process to another species, ‘this will also allow us to incubate over a winter period, since this process needs to be able to work at all times of the year,’ explained Dr Bruce.
And with industrial interest already apparent in the UK, work continues with Tri-Perm’s Austrian partner to examine the possibilities for exploiting this treatment route at a European level. Meanwhile, Tri-Perm Processes continues to develop the patented process and to seek industrial partners to assist in the full commercialisation of a technology which, it believes, has ‘many and varied’ uses within the timber industry and will widen the range of applications for Scotland’s timber resource.
