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There are many techniques of extending the life of bamboo under use is through preservation treatments. These techniques include non-chemical and chemical methods. Full training on the most useful and economical methods are will be conducted at Kitil farm.

Why preserve bamboos?

Bamboos are a natural material and under natural conditions will gradually decay. If they are used as structural components they will need to be replaced after a period of time. The costs of this may prove prohibitive and the status of the bamboo will need constant monitoring to determine when it needs to be replaced. Preserving bamboos extends their life, reduces costs in the long run and improves safety of the structures they are used to form.

What are sap displacement preservation methods?

Sap displacement methods replace the sap in the vessels of a fresh bamboo culm with preservative. The culms are then left to stand for two weeks in order that the preservative can diffuse into the surrounding tissues and the preserving salts can be fixed in the cells. Sap displacement can be done by using natural capillary action or by one of a small range of simple pressurised techniques.

What is the role of a sap displacement preservation unit in rural development?

The unit itself offers employment opportunities to its employees and to many people in its forward and backward linkages. The unit can only treat freshly harvested bamboos and so a source of bamboos near to the unit is required. Local bamboo plantations can be established to supply the unit and create further income generating opportunities. Bamboos can be intercropped with food plants and the plantations can thereby increase the food security of the rural people that manage them.

How do I establish a sap displacement unit?

A sap displacement preservation unit can be established very cheaply. The only requirements are a supply of freshly harvested bamboos, labour and information from the secondary processors of their requirements. If a pressurised unit is to be established then a source of energy for the compressor will be needed. A pressurised unit capable of treating 50 bamboos per day can be established for USD $500, including a compressor, and non-pressurised units can be established for considerably less.

http://www.inbar.int/totems/bamboo-preservation-by-sap-displacement/

How to treat bamboo?

Preservation treatment methods of bamboo are of 2 types: the traditional or non-chemical methods and chemical methods. Others alternatives methods are rarely used, Chalet & Bamboo has developed on 100% eco-friendly method. The choice of treatment method will depend on the state of bamboo, whether it is green or dry, whether whole cane or split, its future application, quantity to be treated and the time available.

Traditional or non-chemical methods

These are ancient methods widely used for centuries by villagers and artisans in countries where bamboo grows, and often the skills are passed on from generation to generation. The most commonly methods used are smoking, white-washing, storage in water.

Smoking:

Smoking is carried out ​​in chambers. Heat and toxic agents produced by smoke destroy the starch in bamboo making it immune to insect attack and also blackens the culms. There are, in Japan, bamboo houses older than 100 years. The smoke from the kitchen (fireplace without chimney) spreads throughout the house and thus preserves the bamboo structure from any attack.

Baking over open fire

Baking over fire after applying oil on the surface of green round bamboos. This causes rapid drying of the outer shell and induces partial charring and decomposition of starch and other sugars. This method is very useful for simultaneous straightening of bamboos in round form.

White washing

Bamboo culms are painted with slaked lime, thereby prolonging their lifespan by delaying and reducing the absorption of moisture while being a repellent against insects.

Soaking in water:

Freshly cut bamboo is stored either in water ponds or in running water for 3-4 weeks to leach out starch. This process protects the bamboo against insects. When stored in water basins, water must be changed frequently to avoid fouling.

Although traditionally treated bamboo shows increased resistance to insects and fungi attack compare to the freshly cut culms, these methods do not however provide complete satisfaction in the long term.

Chemical treatment methods

Chemical preservatives are used to protect bamboo products from degradation. These are well established methods providing good protection even in adverse conditions.

Tanalised method - chromated copper arsenate (CCA)

As for wood, bamboo products are often tanalised, impregnatedunder pressure or by boiling with highly toxic substances such as chromated copper arsenate (CCA)to protect against rot. TheCCA has been very effective but very toxic and carcinogenic. Other products are used as "ammoniacal copper arsenate" or ACA. Ammoniac facilitating penetration in bamboo or wood makes this product effective against fungi, bacteria and insects. Ammoniac and copper components are highly and eco-toxic non-degradable. They therefore pose problems in end of life of the product. Due to these toxins, it is advised that not to burn tanalised products, since arsenic (which is a poison) is immediately released into the ambient atmosphere. Since the 1990s, this product is prohibited gradually increasing number of countries and a growing number of uses. Unfortunately, these products are still widely used in some bamboo factories without much consideration.

Treatment with Boric acid / Borax

The preservative used is a mixture of boric acid and borax which result in the formation of disodium octaborate, which is easily soluble in water. Boron salts are effective against borers, termites and fungi (except soft rot fungi), and is widely recognized to be environmentally acceptable and safe for the mammals. These boron salts are dissolved in water. After treatment, the water evaporates leaving the salts inside the bamboo. Boron salt is non-fixing type, that is, the preservative is leachable. Therefore this process is recommended for bamboo culms that would not be exposed to water or rain. Borax/boric acid seem to be non toxic to the environment, but is highly saline, and little is known environmental toxicity. However, as it hasafungicideandinsecticideaction thatsuggestsit would not beenvironmentally neutralin caseofmajor pollution. It is mildly toxic to humans. Simple exposure can cause respiratory and skin irritation; ingestion may cause gastrointestinal distress including nausea, persistent vomiting, abdominal pain, and diarrhea.

There are various way methods of treatment of bamboo.
  • Bamboo could be impregnated under pressure in autoclave or by boiling.
  • Bamboo could be soak in a solution in an open basin for several days (for slats) until one week if bamboo culms.
  • Or by using the “boucherie” method.
  • However, in all cases, borax/boric acid diffuse better into bamboo when bamboo is moist i.e. in the green condition.

    The products made with treated bamboo with borax are not toxic. However treated bamboo must not be burned, as the gases of such a fire are toxic.

    There is a debate either the boric acid / borax is toxic or not.

    Boric acid / borax has low toxicity to humans through ingestion or inhalation. Median lethal dose (LD50) rating of 2,660 mg/kg body mass for man. Boric acid is poisonous if taken internally or inhaled in large quantities. It is generally considered to be not much more toxic than table salt. Some ethnic groups use it however as a food additive. However in some countries it is requested to farmers and restaurateurs not to use it because of unacceptable risk to consumer health.

    In France, the boron content should not exceed 1 milligram per litre according to health standard for drinking water.

    At high concentrations it is irritating to eyes, skin and respiratory tract where short exposure but may have effects on the kidney in cases of prolonged or repeated exposure.

    The European Community decided to amend its classification as repro-toxic category 2 and to apply the risk phrases R60 (may impair fertility) and R61 (may cause harm to the unborn child).

    Therefore, if it is said that borax and boric acid is already a more environmentally friendly as well as an efficient way to preserve bamboo, it is sure that it should be used carefully by operators with safety precaution.

    Other alternatives methods:

    Treatment of bamboo with limewater

    What is Lime?

    Lime has been known for centuries in the sector of buildings. After several decades when it fell into disuse, lime now finds again a new interest particularly in connection with renovation of old buildings. Lime is a 100% natural since it consists only of stones fired at very high temperatures. Strictly, it is an oxide of calciumwith varying oxide magnesium but the common name of lime can encompass various chemical states of this product. The quicklime is the direct product of pyrolysis of limestone, mainly of calcium oxide (CaO). The lime or slaked lime is obtained by the reaction of quicklime with water. It consists mainly of calcium hydroxide (Ca(OH)2). Other forms of lime have common applications in agriculture and gardening, including dolomic lime containing magnesium and hydrated lime

    What are the properties of lime?
  • Natural product
  • Healthy and Green
  • Antiseptic
  • Antifungal
  • Disinfectant
  • Antistatic
  • Protection against insects - Insect Repellent
  • Good thermal and sound insulation
  • Anti-humidity excellent adaptation to changes in temperature and freezing
  • Apply to walls: Great diffusing capacity (let the walls breathe)
  • An excellent fire retardant.
  • In terms of ecology, the lime does not contain any product of petroleum chemistry. Lime residues can even be composted. Healthily, lime contains no formaldehyde or VOCs and no other allergen product. With its antistatic properties, the amount of dust is minimized. Moreover it is naturally antifungal and is ideal for wet rooms. Lime is recommended for people suffering from allergies, from various sensitivities and, of course, for anyone concerned about his health.

    Given these many properties of lime, and aiming to provide a 100% eco-friendly and non-toxic treatment for our bamboo, Chalet & Bamboo has developed a unique method of treatment with “lime water”.

    How is the water lime treatment?

    To prepare lime water, we mix the lime (slaked lime) with water. It is sparsely soluble, it is necessary to stir the mixture for some time. This step results in a white solution called milk of lime, which is a suspension of calcium hydroxide particles in water.

    To eliminate the unsolved lime in suspension, we proceed to a decantation of the milk of lime for 24 hours. As a result we obtain the lime water, a clear solution. Lime water is the common name for saturated calcium hydroxide solution (Ca (OH) 2) In contact of carbon dioxide (CO2) it will form calcium carbonate (CaCO3), which can be seen as a white film on the surface of the lime water.

    Once limewater ready, it is transferred by gravity into the basin where we placed the bamboo to be treated. Bamboos are impregnated with lime water by soaking for one week.

    As with borax, it is important to perform this treatment on freshly cut bamboo. Indeed, unlike wood, bamboo undergoes anatomical changes and begins to shrink once it begins to lose water.

    Sap in the vessels is precipitated, clogging the openings to the adjacent tissues. This reduces the treatability of bamboo and therefore the diffusion of preservative agents in the cells of bamboo.

    Treatment in boiling linseed oil / oleo-thermal process

    The culms or slats of bamboo are soaked in linseed oil heated to between 100 and 120 ° C. The treatment of bamboo by oleo-thermal process is to our knowledge not developed mainly due to the excessive cost of energy to boil the oil in large basins.

    Thermo-treatment

    The principle of the process is to heat the bamboo in an autoclave at a temperature high enough (for bamboo between 150 and 200 ° C), in anoxic condition and to regularly inject steam to avoid the bamboo to ignite. Bamboo is "cooked" in some way and stabilized while remaining solid. Its ability to absorb water is reduced by half.

    The technique thermo-treatment of bamboo is an alternative to preservative treatment with use of insecticides and chemicals. However, heating the bamboo at high temperatures makes it stable and virtually rot-proof. It thus makes naturally resistant to borers, termites, fungi and moisture.

    Bamboo products treated by this method can also be used as a structural element of a building. But bamboo from thermo-treated tends to reduce strength and flexibility, and their implementation in structure requires special precautions (such as use of larger section).

    They are also ideal for flooring, decks, exterior, siding etc.

    The bamboo processing under high temperatures is to our knowledge not yet developed. Chalet & Bamboo seriously considering this method of treatment but requires a significant investment.

    Ref: http://www.chalet-bamboo.com/treatment.html