Author : Nripal Adhikary

This paper deals with an experiment by ABARI, a specialized bamboo and adobe research and design firm of Nepal’s experiment with various treatment methods: which included vertical soak diffusion method, traditional soaking method and boucherie treatment method using boron compound and neem solution.

Bamboo has played an important part in the traditional life of Nepal. (Poudyal 2006, Bista 2004, Karki et. at 1998) From the “untouchable” Dalits castes to the “high caste” Brahmins: bamboo has played a vital roll in income generation. (Bista, 2004) Eighty one species (5.2% of the world species) belonging to 23 genera (24% of the world genera) are found in Nepal. (Poudyal 2006) Nepal has both tropical bamboos found in the South-East Asia and temperate bamboos found in Tibet and Bhutan. (Karki, et. at 1998) Traditionally, bamboo is used either for food, fodder, construction material, medicinal and domestic utilitarian uses. (Bista 2004, Karki et. al 1998) Bamboo products such as mats and household items are manufactured by local farmers and artisans, which are sold in local markets. (Bista 2004 Bista, Karki et. all 1998) Despite prominence in the production and lifestyle, owing to the poor infrastructure, disappearing knowledge and poor craftsmanship bamboo based economy only contributes 1-2% to the national GDP. (Karki et. at 1998)

The quality of bamboo craftsmanship, is generally poor due to several reasons: bamboo used for construction is not mature enough, bamboo is not treated, improper handling, lack of connection materials and skills, inadequate tools, lack of finishing materials and lack of exposure to the different bamboo designs. Furthermore, though people are aware of the beauty and the strength of bamboo, they are reluctant to make permanent structures with it because they are scared of its non-durability.

ABARI (Adobe and Bamboo Research Institute)
As an architect, I had been designing with adobe (sun dried bricks) in New Mexico, USA and Mongolia. Due to the lack of wood in either of the deserts, I was promoting woodless dome construction technique. However, after coming back to Nepal, I had to make changes in the construction technique because of the different climatic conditions. I could not use adobe alone because of the wet climate and the seismically active terrain. However, I was fortunate enough to have bamboo at my disposal.

Impressed by its economic, ecological, structural and aesthetical qualities, I began promoting bamboo. Though people were aware of bamboo’s superior strength and its beauty, people were reluctant to use it because it decayed fast. Even if they did, the middle class people only built temporary structures, as an annex to their existing concrete house and the poor people did not want to use it altogether because the high maintenance symbolized poverty.

It is in this context, I initiated a specialized research and design institution (ABARI Adobe and Bamboo Research Institute http://www.abari.org), that would systematically investigate these material, so they could address the modern housing need of Nepal. Our main focus has been to promote a sustainable housing by mobilizing local human and natural resources in order to provide safe and sanitary living condition.

Before ABARI could push the bamboo-adobe design concept, we had to find a solution for the fast decaying bamboo. The traditional wisdom of soaking in water, using mature bamboo or drying did not suffice. A more efficient technique for treatment was need. Therefore, we initiated a project whose main objectives were:

1. To find a fast and efficient treatment method, that would take care of the common termite and powder beetle problem.
2. To find a system that is cheap and easy to construct, which a poor can emulate.
3. To find a system that can be developed locally.
4. To develop a system that is portable, so it can be taken to the remote parts the country which are not accessible by road.

Vertical Soak Diffusion (VSD) Method,
It is a method, where all the nodes except the last one are penetrated with a long iron rod with a spearhead welded on one end and a T-shaped handle on the other. After which, the bamboo are vertically placed, and preservative are poured on to them.

VSD method was not feasible because,
1. It is hard to penetrate bamboo if they are curved or long.
2. It is time consuming. One has to soak the bamboo in a rain-protected area for at least 2 weeks.
3. To make an elevated platform is sometimes expensive and not feasible.
4. One 10 meter bamboo requires about 6 liters of boron compound. It cost Nepali Rs. 300(5USD) for 6 liter solution, while the bamboo only cost Rs. 70 (1USD). The cost ratio is too high and not affordable to many.

Therefore, mainly considering the cost issue, this technique was abandoned.

           Bamboo are submerged for 6-10 weeks

Then we tried the traditional soaking method

Traditional Soaking Method
In this technique bamboo are submerged in water for about 6 weeks. This method increases the durability of bamboo, according to a local belief, by 10 years. It is believed that since starch is soluble in water, by submerging the starch gets dissolved.

1. Safe and effective non-technical approach.
2. Economical.
3. Time tested treatment method.

1. Leaving bamboo for about 6 weeks under water was not always safe.
2. Time consuming.
3. Very resource consuming when done in a large scale.
4. Transportation to the water source is not always easy.

However, I do endorse this technique, if all the resources are available and the alternative is not there.

With the impracticality of VSD method, we experimented with a modified Boucherie Technique. In Nepal, Abari was the first organization to try this technique in a local scale, so there was very little literature or help to ask for. Our main resources was INBAR’s website and other resources on the web. From the web resources we could get the general concept of the Boucherie technique, but we had to basically design and build everything on our own since we did not find a detailed manual on its construction. Everything in this plant was built and improvised by a local technician.

Physiological Characteristics
Bamboo culms are divided into nodes and internodes and are composed of two types of tissue; parenchyma cells and vascular bundles. The latter consist of vessels, thick walled fibers and sieve tubes and it is through these that water movement takes place in the living plant. (Rao 17) In Modified Boucherie Technique, (aka. sap displacement technique), pressurized preservative solution is applied on the basal end, which pushes the sap contained in the vascular bundle out and then replaces it with a preservative solution. This technique is only possible on a freshly cut bamboo because vascular bundle is still wet.

1. A big cylinder, fitted with:
• A pressure gauge: The pressure inside the cylinder is always kept at 20-25 psi, which is enough to send the solution inside the bamboo.
• Solution inlet: a mixed solution is poured through this inlet.
• Solution regulator: it regulates how much solution is to be let out of the cylinder.
• Hand pump: a simple manual pump to put pressure into the cylinder. An electric compressor can be used if labor is expensive.
• Pressure regulator: to regulate how much pressure is to be let inside the cylinder.
• Solution outlet, which was later, split into 7 outlets, to let the solution out. See the fig.

    Modified Boucherie Treatment Plant (Fig. 1)

                                                        Modified Boucherie Treatment Plant (Fig. 2)

                                         Modified Boucherie Treatment Plant (Fig. 3)

   Men and women using the treatment plant (Fig. 1)

This is a very simple technique, which can be operated by almost anyone. We have taken our treatment plant to the rural areas and more then 50% of the operators have been women.

• The cylinder is ¾ filled with preservative. We are now using boron compound, and we are testing neem and cow urine.
• The cylinder is pressurized (up to 20-25 psi) using a simple manual pump.
• Valve in the nozzle is open for a split second to let the air out
• Nozzle is connected to the bamboo, which is made airtight using rubber tube. Fig. 3
• Sap starts dripping from the branch in almost 5 minutes. It takes about half hour for the preservative to come out from the opposite end)
• Treatment is done for atleast an hour so that the preservative can reach all parts of the bamboo.
• Bamboo is then stored horizontally in a rain-protected area till it dries.

• We have tried this process only on three kinds of bamboo: Bambusa Tulda, Bambusa Nutan and Bambusa Balcooa locally known as Mal, Chanp, and Harot respectively.
• All these bamboo were between 3-5 years of age and they were treated almost immediately after felling.

• We are currently using Boron Compound, i.e. Borax, boric acid and water were used in 1:1:10 ratio.
• We have also used neem.


  Example of an infected bamboo.(fig. 1)

Results using Boron Compound:
Six months after the treatment, we found the following results:
• Molds were formed on the outside and the inside of the ends in almost all the bamboo.
• If the parts where molds were formed were split open, they were found to be clean and unaffected. Thus mold were only limited to the outside.
• Most of the bamboo had white termite like bugs, but they did not penetrate inside. They seemed to content living in the mold.
• 30% of the bamboo’s end where attacked by powder beetle, however they were limited only to the top ends. Only 6 out of 50 bamboos were infected inside. See Fig. 1

 Storage space for freshly treated bamboo (Figure 6)

The reason most of the bamboo had mold in it is because they were not properly dried. They were dried in a closed environment, which had very little sunlight and air circulation. So a new kind of storage was built for another batch of treated bamboo, which had enough air circulation and sunlight yet they were protected against the rain (see Figure 6). In the treated batch the mold were not formed but they still had beetle infection, but yet again they were only in the top ends. It is not a big problem because during design and construction, by protecting the ends, we can stop the infection.

• ½ kilo neem was first boiled in 10 liters water for about half an hour. It was then cooled down; the result was a very thick black neem concentrate. However, it was very difficult to penetrate the solution through the treatment plant so the solution was again diluted at 1: 5 ratio with water.
• The solution was forced into the bamboo using boucherie treatment plant. The solution started coming out from the other end but not through the branches. The explanation was that vascular bundles are wider on the inner part compared to the periphery; therefore the solution could only penetrate on the inner part.
• The solution was then filtered to get rid of the particles, after which the solution easily penetrated the bamboo!

The experimented was successful in terms of penetrating the neem solution into the bamboo. The effect of the solution on preservation has yet to be studied. We are also planning on using cow urine because traditionally it has been used to treat wood.

• The treatment plant can be locally and economically constructed.
• Our three treatment plant successfully treated 1200 bamboo in a month.
• Traditional treatment preservative can be used with this technique: for example neem and cow urine.
• It can be operated with a simple instruction by almost anyone.
• Since this can be taken to rural areas, it can be provide employment to the locals.
• It is a fast and effective process.

• The treatment can only be done for freshly cut bamboo.
• It is only cost effective (compared to VSD) when one is treating more then 25 bamboo.
• Boron compound is not available everywhere, and the alternative like neem and cow urine have to be explored.

As per our objective we have found a simple and effective way of treating bamboo Modified Boucherie Technique. We have successfully treated more then 2000 bamboo using this technique and have trained many people in the process. If we get enough funding we will further explore neem and cow urine solution. However, with the success of the technique, we have already started design and construction in many parts of Nepal. After seeing the technique and our bamboo craftsmanship, more people are interested in using bamboo. Let bamboo prevail. Please check www.abari.org to see our projects.

I would like to thank our dedicated technician Ram Krishna Thapa, who whole-heartedly helped in realizi g this project. And also my parents Shova Adhikary and Basanta Adhikary who financially sponsored this project. And all the bamboo lovers who sent regular emails to encourage the project.

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