Bamboo Preservation and Treatment
Unfortunately, most bamboo species have very low resistance to biological degrading organisms and need specialized bamboo preservation techniques. A wide range of treatment methods are known to prevent such degradation, and to improve bamboo durability.
Many developing counties (where most bamboos grow) suffer a lack of awareness and professional treatment facilities. Furthermore, not all curing methods ensure satisfying results which leads to uncertainties about the advantages of using bamboo all together.
A lot of bamboos used for structural purposes in rural housing are untreated (or the wrong species) and deteriorate in just a couple of years, hence the reason bamboo is still considered as a poor man's timber.
Not only does the incorrect use affect the reputation of bamboo, it also puts heavy pressure on the resource, since frequent replacement is necessary.
We think it is important to promote the correct use of bamboo in order to increase the durability, utilization, and popularity of this versatile and environmentally friendly material. Increasing the shelve-life of bamboo poles by using the appropriate treatment is obviously more economical in the long run.
Natural Durability of Bamboo
Without any protective treatment, most bamboo species have an average durability of less than 2 years. Stored under cover, untreated bamboo may last 4-7 years.
These variations in bamboo durability strongly depend on the species, the length of the culm, the thickness of the wall, but also, and equally important, the time of harvesting.
The lower portion of the bamboo culm is considered more durable, while the soft inner part of the wall deteriorates faster than the outer harder portion. This is related to the anatomical and chemical nature of the woody cells. Although some of the characteristics of bamboo resemble those of wood, its growth characteristics and microstructure is different. Unlike timber varieties like teak, the structure of bamboo is void of toxic deposits.
The large amounts of starch present in bamboo makes it highly attractive to mold and fungi, termites and powder-post beetles. They cause much damage during drying, storage, and subsequent use. Tests have also shown that bamboo is more prone to soft rot and white rot attack than to brown rot.
Bamboo consists of 50-70% hemicellulose, 30% pentosans, and 20-25% lignin. The lignin present in bamboos is unique, and undergoes changes during the growth of the culm. Bamboo is also known to be rich in silica (0.5 to 4%), but the entire silica is located in the outer layer (1mm), with hardly any silica in the rest of the wall. Bamboos also have minor amounts of waxes, resins and tannins, but none of these have enough toxicity to improve its natural durability.
Bamboo Preservation Methods
1. Non-Chemical, Traditional Bamboo Treatment Methods:
These are ancient methods which have been practiced in areas where bamboo commonly grows. They are simple and cost-effective without the use of chemicals or supporting equipment. However, these methods are in general not appropriate for long-term protection of bamboo.
2. Chemical Bamboo Treatment Methods:
Chemical preservatives are used to protect bamboo products from degradation. These are well established methods providing good protection even in adverse conditions.
The selection of the appropriate treatment method depends on various factors:
- State of bamboo; green or dry.
- Form of the bamboo: round bamboo or splits.
- End applications; in ground contact, exposed to atmosphere, undercover, structural/non-structural.
- Scale; quantity to be treated and available time.
- Potential causes of decay; biotic (fungus/insects) and abiotic (cracks/weathering).