Protecting wood in service

1

• Protecting wood in service
• performance without the downside
• Dr Michael J Kennedy
• Horticulture Forestry Science, DPIF
• 80 Meiers Rd, Indooroopilly QLD 4068
• IAWS 2006 Meeting, Melbourne, November 13-16, 2006

2
Protecting wood in service performance without
the downside
Wood in 2100 the renewable structural material
sans pareil

• Why?
• Addresses global energy carbon balance
  problems
• Sequesters carbon as it grows
• Stores carbon indefinitely in service (if
  protected)
• Processing is energetically frugal (unless
  transported long distances)
• But!
• Timber harvesting from native forests ceased
• Native forest cannot be cleared for plantations
• Plantation water use must not endanger rivers
  aquifers
• Natural biodegradability must be countered in
  service
• Protection systems must be harmless to
  environment

3
Protecting wood in service performance without
the downside
Timber harvesting from native forests
ceased Native forest cannot be cleared for
plantations
4
Protecting wood in service performance without
the downside
Plantation water use must not rob rivers
aquifers
5
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
6
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
7
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
8
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
9
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
10
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
11
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
12
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
13
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
14
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
15
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
16
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
17
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
18
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
19
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
20
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
21
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
22
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
23
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
24
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
25
Protecting wood in service performance without
the downside

Protection systems must be harmless to environment
26
Protecting wood in service performance without
the downside
Biocidal systems used as wood preservatives
2500BC - crude pitch (on specified durable
timber) 50AD - essential oils of cedar, juniper,
valeriana 1705 - mercuric chloride 1730 - sodium
arsenite 1767 - copper sulphate 1815 - zinc
chloride 1838 - coal tar creosote ( from 1965,
fortified with insecticides) 1861 - fluorides (
from 1909 mixed with dinitrophenol,
dichromate..) 1911 - copper naphthenate 1913 -
borates 1925 - ammoniacal copper arsenite 1933 -
CCA (chromated copper arsenate)

Protection systems must be harmless to environment
27
Protecting wood in service performance without
the downside
Biocidal systems used as wood preservatives 1933
- CCA (chromated copper arsenate)
1935 - chlorophenols (TCP, PCP, metal salts of
these) 1945 - lindane, DDT 1950 - heptachlor,
aldrin, dieldrin 1970 - bis (tri-n-butyltin)
oxide (TBTO) 1970 - synthetic pyrethroids
(permethrin, deltamethrin, cypermethrin,
bifenthrin ..) 1984 - tri-n-butyltin naphthenate
(TBTN) 1992 - ammoniacal copper quaternary (Cu
DDAC) - ACQ 1993 - triazole fungicides
(azaconazole, tebuconazole, propiconazole,
cyproconazole) 1996 - copper triazole (Cu
tebuconazole) - CuAzole 2004 - Non-metallic
LOSP treatments (propiconazole tebuconazole
permethrin)

Protection systems must be harmless to environment
28
Protecting wood in service performance without
the downside
Diminishing environmental threat of wood
preservatives e.g. termiticides
Dose rate Persistence in soil 1850 arsenic
trioxide 0.035 infinite 1950 - aldrin,
dieldrin 0.05 25 yrs 1975 permethrin 0.02 1
yr 1985 deltamethrin 0.002 3 months

Protection systems must be harmless to environment
29
Protecting wood in service performance without
the downside
Current state of the art for biocidal wood
preservatives

• H1 H2 (borers termites, protected from
  weather)
• synthetic pyrethroids (permethrin, bifenthrin)
• H3 (insects decay, exposed to weather, out of
  ground)
• Waterborne
• ACQ (Cu DDAC)
• Cu Azole (Cu tebuconazole)
• LOSP
• Non-metallic (triazoles pyrethroid)
• H4 H5 (all risks, in ground)
• Waterborne
• CCA
• ACQ
• Cu Azole
• H6 (marine) Creosote CCA dual treatment

Protection systems must be harmless to environment
30
Protecting wood in service performance without
the downside
Current state of the art for non biocidal wood
preservation

• Heat treatments (180-240C, under N2)
• Heat denatures wood components utilised by fungi
• According to the amount of heat applied
• Durability against fungi increases
• Strength decreases
• Resistance to termites decreases
• Hot oil treatments (100-180C)
• Some denaturation, but less than with the dry
  heat treatments
• Oil imparts resistance to wetting and further
  improves durability
• Chemical modification of wood components (e.g.
  with acetic anhydride)
• Modified wood components cannot be utilised by
  organisms
• These ultimate non-biocidal treatments are
  very expensive, .. commercial?

Protection systems must be harmless to environment
31
Protecting wood in service performance without
the downside
Current state of the art for impregnation systems

• Envelope impregnation (insects only)
• Spray or dip systems achieve protective envelope
  of pyrethroid (2-5mm)
• Cost effective, suitable for treating final
  form timber

Protection systems must be harmless to environment
32
Protecting wood in service performance without
the downside
Current state of the art for impregnation systems

• Glueline addition (insects only)
• Stable pyrethroid in adhesive survives pressing
  process in plywood
• Bifenthrin is locked into the glueline,
  inaccessible to all but termites
• Very cost effective

Protection systems must be harmless to environment
33
Protecting wood in service performance without
the downside
Current state of the art for impregnation systems

• Waterborne impregnation (general purpose, CCA,
  ACQ, CuAzole)
• Low treatment cost (solvent is water)
• Wood swells and must be re-seasoned before
  dressing to final form
• Planer shavings are contaminated with
  preservative components
• The current preservatives contain metal (but it
  is only Cu)
• Cu is less well fixed in ACQ and CuAzole than in
  CCA treatments
• ACQ and CuAzole are 15-30 more expensive than
  CCA

Protection systems must be harmless to environment
34
Protecting wood in service performance without
the downside
Current state of the art for impregnation systems

• LOSP impregnation (white spirit etc solvent)
• Does not swell the timber, no re-seasoning or
  dressing required after, suitable for treating
  final form timber
• Currently using dual triazoles permethrin,
  excellent non-metallic system
• Does not penetrate some non-durable heartwood
  well (e.g. radiata pine)
• 30-40 L/m3 of solvent retained in timber after
  treatment, lost to air - likely near-future
  regulatory problems with VOC emissions, future is
  not bright

Protection systems must be harmless to environment
35
Protecting wood in service performance without
the downside
Current state of the art for impregnation systems

• Supercritical CO2 impregnation (1 plant only -
  in Denmark)
• No swelling, no re-seasoning, no re-dressing,
  treating final form timber
• Currently using dual triazoles permethrin,
  excellent non-metallic system
• Closed system recycles CO2 solvent - no solvent
  costs, no VOC emitted!
• Packs can be impregnated without spacers,
  wrapped!
• Timber can be painted immediately after
  impregnation
• All LOSP benefits without LOSP disadvantages -
  is this IT?

Protection systems must be harmless to environment
36
Protecting wood in service performance without
the downside
Current state of the art for impregnation systems
Supercritical CO2 impregnation - is this IT?

• Unfortunately, NO
• Plant operates at VERY high pressure - huge
  capital cost
• (80M DKK for 60,000 m3/yr throughput)
• Operating pressures tend to damage timber
• Cannot deliver in-ground preservatives at
  present (H1, H2, H3 only)

Protection systems must be harmless to environment
37
Protecting wood in service performance without
the downside
Current state of the art for impregnation systems

• Supercritical CO2 impregnation - is this IT?

Protection systems must be harmless to environment
38
Protecting wood in service performance without
the downside
The next state of the art for impregnation
systems??

• Currently under development in Australia
• Uses compressed gases as carrier solvent, at
  current treatment plant pressures
• Achieves full penetration of radiata pine
  heartwood, at same retention as sapwood
• Initial work with spruce looks good
• 100 recovery of solvent from timber
• Possibility of sequential treatments

(WO/2006/092673) IMPREGNATION APPARATUS AND METHOD

Protection systems must be harmless to environment
39
Protecting wood in service performance without
the downside

• So, well before 2100, we will have
• Non-biocidal wood modification systems partially
  reducing the inherent susceptibility of timber to
  W.D.O.s without seriously diminishing desirable
  timber properties
• Supplementary biocidal treatments that ..
• use biocides presenting no threat to the
  environment
• are applied in closed systems that release no
  solvent
• and require no dressing after, no contaminated
  shavings

Protection systems must be harmless to environment
40
Protecting wood in service performance without
the downside
To achieve this, we need RD

• 1. For non-biocidal wood modification systems
• Find the right balance between non-biocidal and
  biocidal for the most effective protection, the
  least reduction in other wood properties and the
  least release to the environment
• Develop simple measures of the quality of the
  non-biocidal treatment process specifications
  are not enough we need verifiable results-type
  specifications that can be applied in the
  marketplace

Protection systems must be harmless to environment
41
Protecting wood in service performance without
the downside
To achieve this, we need RD

• 2. For the biocidal supplementation systems
• Develop current excellent above ground
  mixtures of low environmental impact biocides to
  produce combinations capable of protecting in
  ground
• Develop penetration disclosing tests for the new
  generation organic biocides, to facilitate
  in-plant quality control of the treatment process

Protection systems must be harmless to environment
42
Protecting wood in service performance without
the downside