AU704809C - Environmentally friendly treatments to extend the functional life of wood structures and novel treated wood structures - Google Patents

Description

Environmentally friendly treatments to extend the life of wood

Field of the Invention The present invention relates to novel, degradation resistance, wood structures and a method for treating wood structures to minimize their degradation.

Background

Wood is one of the most utilized mateπals of human society. However, like any mateπal, wood is susceptible to degradation This degradation, wood decay, is believed to result pπmaπly by physical weatheπng and the biological acUon of bacteπa, fungi and insects.

Current technology for the preservation of wood and wood products relies pnmaπly on treating the wood with chemicals which inhibit microbial and insect activity, most commonly creosote and pentachlorophenol and more recently, the use of Copper-Chromiu -Arsenate (CCA). Unfortunately, the use of such chemicals and metals also represents an exposure πsk to humans and the environment. As such, the use of many of these chemicals has come under government regulation. The recalcitrance of creosote and pentachlorophenol and the transportability of the metals make the widespread use of treated wood in the environment a potentially damaging environmental legacy.

Further, current wood treatment technologies do not completely prevent wood decay, but only delay it. In most cases, treated wood will require penodic re-treatment, with its inherent chemical exposure risks, to maintain effectiveness

Summary of the Invention

The present invention provides a method to extend the functional life of wood structures by alteπng the environment of wood decay organisms while minimizing the use of environmentally hazardous chemicals. The method of the present invention advantageously provides an economical means for extending the life of wood structures placed into service, and/or currently in service, while significantly minimizing the environmental πsks and workplace πsks posed by the current treatment technology, both in initial treatment and reapplication.

According to the method of the present invention degradation of wood structures is retarded through the use of a physical bamer and a microbial treating solution, to affect the nature of the microbes in, on and surrounding the wood structure. As explained in more detail below, the microbial treating solution affects the environment of the microorganisms responsible for wood decay to minimize decay

The method of the present invention is particularly advantageous for treating wood supporting structures including, but not limited to- telephone poles, utility poles, pilings, foundations and other building supports and the like. The method may be utilized to further treat wood structures, such as telephone poles, utility poles and the like, which have already been treated with creosote, pentachlorophenol and/or CCA.

The present invention also provides new wood structures, including the wood supporting structures listed above, with increased resistance to degradation. An advantage of the method of the present invention is that the method minimizes the use of environmentally hazardous chemicals, and the need to retreat wood structures with environmentally hazardous chemicals

Another advantage of the method of the present invention is that the method is simple and economical A further advantage of the method of the present invention is that the method may be performed at a worksite, prior to placement of the w ood structure

An advantage of the wood structures of the present invention is that the wood structures have increased degradation resistant

Further details and advantages of the method and wood structures ol the present invention will become apparent from the following more detailed descπptions

Bπef Descπption of the Drawings

Figure 1 depicts a wood structure (utility pole) of the present invention having been treated according to the method of the present invention

Detailed Descπption of the Invention

According to the present invention, a method for treating wood structures compπses- applying a microbial treating solution to a portion of the wood structure subject to decay from microbial organisms, and coveπng a portion of the wood structure subject to decay from insects with a substantially insect impenetrable mateπal , wherein the covered portion compπses at least a portion of the treated portion Preferably the method for treating wood structures of the present invention further compπses applying additional microbial treating solution to the treated and/or covered portion of the wood structure, and/or the ground surrounding the wood structure, at time intervals sufficient to maintain an altered microbial community in the wood structure. The portion of the wood structure, and/or the wood structure, treated according to the method of the present invention may compπse virgin (untreated) wood, or may compπse wood treated with creosote or another chemical treatment. For example, the method of the present invention is particularly advantageous in treating utility poles which have already been treated with creosote, pentachlorophenol and/or CCA.

For wood structures placed in the ground, the portion of the wood structure subject to decay from microbial organisms includes a portion of the wood structure located where oxygen in present underground to approximately 2 feet above the ground. Similarly, the portion of the wood structure subject to decay from insect includes a portion of the wood structure located where oxygen in present underground to approximately 2 feet above the ground. Generally, for wood structures placed in the ground, the portion of the wood structure treated by the method of the present invention will be a portion extending from approximately 4 feet underground to 2 feet above the ground, preferably from 3 feet underground to 1 foot above the ground, similar portions of the wood structure will generally be covered by the substantially insect impenetrable mateπal according to the method of the present invention.

Suitable substantially insect impenetrable mateπals include plastics, including polyethylene, polypropylene and the like. As understood to those of ordinary skill in the art insects may eventually penetrate any mateπal, particularly where the mateπal is located in an outdoor environment and therefore susceptible to puncture and or other damage. Thus, the present invention should not be construed to require that the substantially insect impenetrable matenal remain impenetrable over its entire life, however preferably it will. A preferred substantially insect impenetrable mateπal is a sheet of plastic matenal is utilized and wrapped around the wood structure and sealed/shπnk fitted by the application of heat.

In addition to providing an insect bamer, the substantially insect impenetrable mateπal will assist in maintaining an altered environment for microbes within, on the surface of, adjacent to the surface of, and in the ground surrounding the wood structure. A further benefit is that the substantially insect impenetrable matenal will help to prevent seepage of any environmentally hazardous chemicals, the wood structure may have been treated with, into the environment.

The combination of the microbial treating solution, and the substantially insect impenetrable mateπal, will generally alter the environment for insects and microbes, withm, on the surface of, adjacent to the surface of, and in the ground surrounding the wood structure. This environment will be further altered by, and constantly changing due to, the effects of precipitation, humidity, temperature and the like, from the outside environment, on the wood structure. For example, the altered environment for insects and microbes will vary from an aerobic environment to an anaerobic environment, a wet to dry environment, a nutπent πch to a nutπent poor environment, etc. While not wishing to be bound by any theory, it is believed that the alteπng environmental conditions result in an altered microbial community (a microbial community with an altered metabolism) which will not be as active in degrading the wood structure.

In order to maintain an altered microbial community, and altered environmental conditions for insects and microbes, additional microbial treating solution may be applied to the wood structure and/or the ground surrounding the wood structure. Additional microbial treating solution may be applied to the wood structure by injecting the solution into or adjacent to the wood surface, preferably at least in part underneath the substantially insect impenetrable sheet. Preferably, additional microbial treating solution is applied through the use of a controlled release reservoir positioned above the substantially insect impenetrable on the wood structure. The reservoir may be filled with microbial treating solution which upon release will travel down the wood structure, due to gravity, and seep into the wood surface and into the area adjacent to the wood surface, underneath and on top of the substantially insect impenetrable mateπal, and into the ground surrounding the wood surface. The reservoir may be constructed from a plastic, including but not limited to, polyethylene or polypropylene, and includes means for stoπng microbial treating solution and means for releasing the microbial treating solution at controlled intervals. The means for stoπng microbial treating solution include, but are not limited to, a reservoir, and/or vascular space in the intenor portion of the reservoir The means for releasing the microbial treating solution include small perforations or holes in the reservoir which will open under certain temperature or humidity conditions to release microbial treating solution from the storage space

Suitable microbial treating solutions include those which will alter the environment for microbes in, on and surrounding the wood structure, and/or alter the metabolism, and/or otherwise render ineffective, microbes and bacteπa which degrade wood in nature.

Wood compπses interlocked layers of cellulose and lignin The decomposition of lignin in nature is generally understood to occur almost exclusively through the agency of fungi called Basidtomycetes and bactena. As each layer of lignin is compromised, more of the readily degraded cellulose becomes available. It is believed the action of these fungi in concert with bactena, which rapidly degrade cellulose, which allows for the degradation of wood in nature. Insects, such as termites can do considerable damage, but even they rely on bacteπa to ultimately degrade the cellulose.

In particular, the preferred microbial treating solution compπses one or more of the following: a readily available carbon source solution, a lysis agent/surfactant solution, a osmotic pressure altenng solution or mixtures thereof. These solutions may be used separately, or in concert, to control the activity of wood decay organisms immediately adjacent to the wood structure. As set forth above, regardless of which treatments are utilized the wood structure will also be wrapped in a sheet of substantially insect impenetrable matenal such as polyethylene. A reservoir with additional treatment solutions may also be utilized. In addition to serving as a bamer to insect penetration of the wood, the substantially insect impenetrable matenal will also help to isolate the microbial community immediately adjacent to the pole so that community can be more readily manipulated by the microbial treating solutιon(s). As explained above, the reservoir will be designed to release treatment solution gradually over time and will thereby help to reduce the need for subsequent re-treatment of the poles, preferably to the point that re-filling ofthe reservoir will only be required approximately every three years.

One suitable microbial treating solution compπses a readily available carbon source. In addition to their cooperation in the degradation of wood, bactena and fungi are in competition for available resources in the area adjacent to the surface of the wood. Competition for available resources is a fundamental tenet of biology and is visible on all levels of life. To utilize this competition to control the activity of wood decay organisms, a readily available carbon source is applied to the wood structure. Readily available carbon sources include solutions compnsing 10 to 80%, by weight, preferably 40 to 60%, by weight, a carbon source, including, but not limited to, molasses, corn syrup, fruit sugars, food processing wastes, other sugar solutions and/or mixtures thereof, in water Molasses is a preferred carbon source because molasses also includes sulfur which as explained below provides additional advantages. The competition for a readily available carbon source should tend to favor the bacteπa in the system over the fungi because the bactena are more readily adaptable and will consume the carbon source at a rate approaching the maximum possible rate. The limiting factor in the degradation of molasses will, in fact, be another limited resource for which bacteπa compete with fungi, namely oxygen. This will create anaerobic (defined as extremely depleted oxygen) conditions at, and adjacent to the wood surface, and lead to the πse of organisms which are adapted to life without oxygen. Anaerobic organisms make their energy through the reduction of available compounds and in the absence of oxygen and nitrate the reduction of sulfur compounds is favored. These processes produce far less energy than aerobic processes and as such are much slower. Further, there are no known pathways for the anaerobic biodegradation of lignin Thus, the anaerobic community should be either greatly slowed or completely prevented from the degradation of the wood present. When the microbial treating solution compπses molasses as a readily available carbon source, the reduction of the sulfur in the sulfured molasses should produce hydrogen sulfide (H₂S). H₂S will further inhibit insect activity and in addition make the molasses solution less attractive to larger animals who might seek out the molasses initially. Another suitable microbial treating solution, which may be utilized in conjunction with other microbial treating solutions compπses a lysis agent and a surfactant, or a lysis agent surfactant. A preferred lysis agent/surfactant is sodium dodecyl sulfate (SDS), preferably in a 1 to 20%, by weight, solution in water The application of a dilute (0.5 to 2.0 %, by weight, in water) SDS to the wood surface is intended to have at least two effects on microbial organisms First, SDS is capable of lysing the cell membranes of many bactenal species thereby causing their death. Second, SDS is a surfactant and thus structurally has both lipophilic and hydrophilic moieties As such, through the formation of micelles, SDS can increase the effective solubility of any creosote or pentachlorophenol present in the wood structure. This increase in the effective solubility theoretically increases the microbial reducing activity of the creosote or pentachlorophenol, without adding new amounts of these compounds to the system

Another suitable microbial treating solution is one which will alter the osmotic pressure conditions at the wood surface, and/or immediately adjacent to the wood surface Suitable osmotic pressure altenng solutions include, but are not limited to concentrated salt solutions, sugar solutions, other ion πch solutions and the like. For example, the application of a relatively concentrated salt (NaCl) solution to the wood surface alter the osmotic conditions immediately adjacent to the pole. This additional environmental pressure should affect the microbial community at, and adjacent to, the wood surface The effects are relevant because ofthe cooperation required between the more highly evolved, but less adaptable fungi and the more rapidly adaptable bactena. The salty conditions should therefore favor bacteπa which are not inhibited by the salt to the exclusion of fungi both initially, and subsequently, because while there are known to be halophilic (salt-loving) species of bactena, there are no currently known species of halophilic fungi. High concentrations of salt also can be toxic to and therefore deter insects, should they be able to penetrate the substantially insect impenetrable bamer Salt should also accumulate adjacent to the pole over time if it is prevented from contact with rainwater (e.g. through the use of a plastic substantially insect impenetrable matenal) which will maximize its effectiveness as the greater the concentration of salt the better its effect.

A novel wood structure of the present invention compπses a wood structure which has been treated according to the method of the present invention. More particularly according to the present invention, a wood structure compπses- a wooden member; a microbial treating solution in contact with a portion of the surface of the wooden member; and a substantially insect impenetrable mateπal in contact with the microbial treating solution and thereby in contact with the portion of the surface of the wooden member.

Preferably the wood structure further compπses: a reservoir, with additional microbial treating solution contained within, positioned adjacent to the portion of the surface contacted with the microbial treating solution and including means for dispensing the additional microbial treating solution onto the portion of the surface, and into the area between the portion of the surface and the substantially insect unpenetrable mateπal.

As set forth above, wood structures of the present invention include, but are not limited to, wood supporting structures such as telephone poles, utility poles, pilings, foundations and other building supports and the like. The wood structure of the present invention may compπse "virgin" (untreated) wood or wood that has been treated with creosote, pentachlorophenol, CCA, and/or other treating agents.

Suitable microbial treating solutions, substantially insect impenetrable mateπals and reservoirs for use in the wood structure of the present invention, and details relating to the assembly and use of the wood structure of the present invention are set forth above with respect to the method of the present invention, and in the following paragraphs.

Figure 1 depicts a utility pole treated according to the method of the present invention, and which is a wood structure of the present invention. Referπng to Figure 1, a utility pole 2 includes a substantially insect impenetrable matenal 4 sunounding a portion 3, of the surface of the utility pole near ground level and a reservoir 6, surrounding pole 2, and located at, or adjacent to surface portion 3.

H_a is the height (depth) of mateπal 4 above ground level and H_u is the height (depth) of material 4 beneath ground level. As set forth above, H_u is preferably equal to the soil depth where oxygen is present. Generally, for most soils, H_u will be 0.5 foot to 4 feet, preferably 1 to 3 feet, more preferably approximately 3 feet. H_a is preferably equal to the distance above ground (height) where microbial and insect populations are substantial. Generally, H_a will be 0.25 foot to 2 feet, preferably 0.5 foot to 1.5 feet, more preferably approximately 1 foot. H_r is the height of reservoir 6 above matenal 4. H_r is preferably a distance which will permit microbial solution to contact the portion 3 of the surface of the utility pole near ground level, and to travel into the space adjacent to the wood surface at portion 3 and underneath mateπal 4. Generally, H_r will be 0.0 inches to

6 inches, preferably 0.0 inches to 3 inches.

Treated utility pole 2 may be assembled pπor to placement in the ground or after placement in the ground pπor to back-filling the hole. For assembly, a microbial treating solution is applied to surface portion 3 of utility pole 2. Then the substantially insect impenetrable mateπal 4, is wrapped around pole 2, over at least a portion of the microbial treating solution. Reservoir 6, is then affixed to pole 2 utilizing adhesives, and/or fasteners such as nails, screws, or the like Reservoir 6 may be filled with microbial treating solution pπor to affixing the reservoir to the pole, or after affixing the reservoir to the pole Utility pole 2, may then be placed upnght in a hole in the ground and utilized

As will be understood to those of ordinary skill in the art, the portion 3, of the pole's surface to be treated may be determined by knowing the depth of the hole in which the pole will be placed and which end of the pole will be placed into the ground. The portion 3 may then be easily determined by determining the portion of the pole which will end up at ground level. Additionally, the portion of the pole treated with the microbial treating solution and the portion of the pole covered with the substantially insect impenetrable bamer may be the same or different but will generally overlap at least in part.

It will thus be seen that the advantages set forth, among those made apparent from the preceding descπption, are efficiently obtained by the method and wooden structure of the present invention. Since certain changes may be made in carrying out the above embodiments of the method and wooden structure system of the present invention, and in their manner of construction, without departing from the spiπt and scope of the invention, it is intended that all matter contained in the above descπption shall be inteφreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the geneπc and specific features of the invention herein descπbed and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims (13)

1. Claims: 1. A method for treating wood structures compnsing: applying a microbial treating solution to a portion of the wood structure subject to decay from microbial organisms; and coveπng the a portion of the wood structure subject to decay from insects with a substantially insect impenetrable mateπal , wherein the covered portion compπses at least a portion of the treated portion.
2. 2. The method of claim 1 further compnsing: applying additional microbial treating solution to the wood structure at time intervals sufficient to maintain an altered microbial community in the wood structure.
3. 3. The method of claim 1 wherein the microbial treating solution is selected from the group consisting of: a solution compnsing a readily available carbon source, a solution compnsing a lysis agent and a surfactant, a solution compnsing as osmotic pressure affecting agent and mixtures thereof.
4. 4. The method of claim 1 wherein the microbial treating solution compπses: a readily available carbon source.
5. 5. The method of claim 4 wherein the readily available carbon source is molasses.
6. 6. The method of claim 1 wherein the substantially insect impenetrable mateπal compπses a plastic.
7. 7. The method of claim 4 wherein the substantially insect impenetrable matenal compπses a plastic.
8. 8. The method of claim 7 wherein the plastic is selected from the group consisting of: polyethylene and polypropylene
9. 9. The method of claim 1 wherein the microbial treating solution compnses: a lysis agent and a surfactant.
10. 10. The method of claim 9 wherein sodium dodecyl sulfate is the lysis agent and the surfactant.
11. 1 1. The method of claim 1 wherein the microbial treating solution compπses a salt solution.
12. 12. A wood structure compnsing: a wooden member; a microbial treating solution in contact with the a portion of the surface of the wooden member; and a substantially insect impenetrable mateπal in contact with the microbial treating solution and thereby in contact with the portion of the surface of the wooden member.
13. 13. The wood structure of claim 12 further compnsing a reservoir containing additional microbial treating solution, positioned adjacent to the portion of the surface contacted with the microbial treating solution, and including means for dispensing the additional microbial treating solution onto the portion of the surface, and into the area between the portion of the surface and the substantially insect impenetrable matenal