Bamboo resources and their utilization in China - Yang Yuming and Xue Jiru

Southwest Forestry College, Kunming, Yunnan 650224, China.

Introduction

The survival and progress of human beings depend on recognizing and exploiting natural resources, which are very much threatened at present.

Wood is widely used and it is well-known that trees have long growth cycles. Unfortunately, the excessive timber harvest has turned out to be disastrous and every country has adopted protection measures to limit the utilization of wood material obtained from the forests. In the past ten years, China's forest areas have been reduced by 23.1% and wood production volume by 22%. By the end of this century, the country's mature wood for logging will decrease from 2.6 billion m³ to 1.248 billion m³. With this challenge, the utilization of bamboo resources has been highlighted. Bamboos, with high strength, elasticity and wear resisting characteristics, grow rapidly and mature in a short period (3-5 years) with high yield, easy to manage and strong in regeneration. Each planting lasts for long time and sprouts new shoots after yearly harvests. Therefore, harvest and utilization of bamboo resources has become a significant agenda.

Bamboo resource and their potential in China

There are more than 1250 species in 75 genera of bamboos in the world. The total area of bamboo forest in the world amounts to 14 million ha distributed mainly in bamboo zones of Asia, Pacific, Americas and Africa. However, East Asia and Southeast Asia have the largest bamboo forest areas including some 80% of the species of the world.

China is located from the subtropical zone to the temperate zone and the southern part is in the tropical zone (particularly Yunnan province), within the reach of East Asian and Southeast Asian monsoon zone. With large area, varied geographical conditions and advantageous natural environment, many bamboo species grow in China. It is recognized as one of the original bamboo diversity areas named “Bamboo Kingdom”. Both in terms of species and the growing area, it ranks first in the world. There are more than 500 species of bamboos belonging to 40 genera in China, nearly half of the globe's total. The number of species and genera are more than in any other country or region in the world. The bamboo forest area in the country is more than 4 million ha and occupies 1/4 of the worlds total, 2 million of which are covered by Phyllostachys pubescens, in man-made forests.

The bamboos are distributed from the southern part of the tropical zone to the northern part of the temperate zone, reaching Yellow River Valley and they are found in the plains, hills, mountains and alpine or subalpine altitudes of 4500 m in 24 provinces.

The south and southwest part of China, particularly in Yunnan, Guangdong, Guangxi, and Hainan, south of 25°N, are in the southeast tropical monsoon region. The major bamboos belong to sympodial type of tropical and subtropical zones. Most of them form large natural bamboo forests, including largest bamboos species of Dendrocalamus, Bambusa, Schizostachyum, Cephalostachyum, Chimonocalamus, Gigantochloa, Thyrsostachys, Neosinocalamus, and others.

The central and eastern parts of China, from 26°N to the Yangtze River (33°N) belong to the subtropical region, influenced by East Asian subtropical monsoons. There are many monopodial and sympodial bamboos. The major genera are Phyllostachys, Indosasa, Sinobambusa, Indocalamus, Pleioblastus, Dendrocalamopsis and others. Among them, Phyllostachys is the most economically important genus in this region, particularly Ph. pubescens, that is concentrated in Yangtze Valley, largest man-made bamboo forest that occupies 58.85% of total bamboo forest area in China.

In the Northern part, from Yangtze River to the Yellow River, equivalent to 33°-37°N, is the warm temperate zone of the middle and downstream valley of the Yellow River. Both monopodial and amphipodial types, like Phyllostachys, Bashania, Pleioblastus, Semiarundinaria, and Thamnocalamus are found. The bamboos play an important role in soil and water conservation as well as windbreaks in this region, where the soil and wind erosion is very serious and irrigated bamboo forests were established. The irrigation is particularly important before and after the bamboo shoot emerges because there is insufficient rainfall during that period.

Bamboo plantation total reserve volume is 150-170 million tons. Under the present management and marketing level, 20-30 million tons of bamboo culms and 3.2-4.0 million tons of bamboo shoots are produced yearly, with an estimated value of 5 billion US$. Natural bamboo forest can provide a total of about 50-70 million tons of culms and 270 000-300 000 tons of shoots annually, with value of 1-1.2 billion US$. There is great potential for further development in the country.

History of bamboo utilization

Bamboo utilization began 4000-5000 years ago in China. During the Yin and Shang Dynasties (B. C. 16th to 11th C.), bamboo was used to make arrowheads. In the Spring and Autumn Dynasty (B. C. 700-746), it was used as a messenger strip with words carved on it. In Qin Dynasty (B. C. 221-207), people made pens of bamboo and in Western Jin Dynasty (A. D. 265-316) paper was made from bamboo.

In Song Dynasty (A. D. 960), bamboo was widely used in people's life. Su Shi, the well known scholar in Song Dynasty, wrote: “bamboo shoot for food, bamboo tile for house making, bamboo hat for rain sheltering, bamboo wood for fuel, bamboo skin for clothing, bamboo paper for writing and bamboo shoes for foot wearing, that is the life - we can not do without bamboo.”

Bamboo also was used in famous Du Jiangyuan hydraulic engineering works 2000 years ago and Han Dynasty people in Sichuan province dug a salt well 480 chi (160 m) deep and used bamboo rope in the industry.

Bamboo shoot is one of the important fields in development. Knowing the delicious taste and rich nutrition food, people considered it a treasure dish in Tang Dynasty 1200 years ago and there was a saying “there is no banquet without bamboo”. In B. C. 1006, Emperor Zhou Cheng entertained his subordinates with “bamboo shoot banquet”. The story reflected the high value of shoots in ancient time.

The protein content is as high as 1.49-4.04%, with 17 kinds of amino acids which come up to 35% of total protein. It is completely free from pollution, people's demand for fresh bamboo shoot cans increased by 12% annually over the world and production volume increased by 8%. With the growing demand of natural food, the gap between supply and demand will be wider and bamboo shoot production will be remarkably profitable.

Bamboo has natural firmness, tenacity, pressure-resisting, tensile strenth and erosion-resisting. It proves to be a quality construction material. Minority ethnic people inhabiting Yunnan, Burma, Laos, Thailand and the Philippines still construct houses with bamboo. An old saying goes “rather to live in bamboo civilization”. Joseph Lee, the famous British scholar, concluded after studying Chinese history of science and technology, “East Asian civilization is bamboo civilization”.

Bamboo can substitute for wood

Even though bamboo has been used for a very long period, there are some defects such as narrow stem, numerous internodes, low durability and ready attack by insects. Since the 1930s, many experts and scholars have been engaged in bamboo utilization research. Encouraged by modern processing techniques, bamboo is used in industrial production.

Here we define the industry as high value-added and environmentally friendly and with comprehensive utilization (Table 1).

Table 1. Bamboo production and utilization in China

Item	Production and Utilization
Bamboo Shoots	Dry shoot, shoot canned, soft package keeping fresh shoot, ready shoot food, healthy and nutritious food.
Bamboo Culms	1.	Craft Product: Artificial products, Handicraft articles, Furniture, and tools
	2.	Construction: Bamboo house, Construction frame, Cement products, Ornamental material
	3.	Industrial Products: 1) Artificial board(including plywood/chip board, veneer covers, sandwich mat board, particle or fiber board) Bus floor board, for construction work, package board, etc.. Use of wood board in furniture, package, construction and ornament or decoration. 2) Parquet (including radial parquet, horizontal parquet, bamboo mosaic, vertical cut parquet)
	4.	Other Products: Paper making/pulp, bamboo rayon, triacetate, artificial fiber, disposable sterilized chopsticks, incense stick, tooth pick, cotton swab, bamboo table ware, etc.
Bamboo Juice	1.	Medicinal bamboo drip;
	2.	Bamboo juice drink, soft drink, bamboo wine, etc.

The equipment for production and techniques for the above products are available in China, including some special equipment, like “bamboo knitting machine”. These equipment are also used in the Southeast Asian countries.

Bamboo is good raw material to replace wood in the industrial process. There is a little difference in the anatomical structure and even in the chemical composition of bamboo and wood. The necessary research in developing and designing alternative technology and equipment should be carried out. Bamboo can be used for making many products, but it should be pointed out that bamboo-based boards can be used in any situation as wood-based boards. The quality depends on the technology, equipment, structure of boards and the glue used.

Bamboo based composites can be produced by covering with: decorative wood veneer, laminated thermosetting plastic coverlayer for strength or decoration. Furthermore, the delicate ornamental designs woven with bamboo skin, or veneer peeled from the bamboos of large diameter may be overlaid on bamboo or wood to make composites particularly of bamboo colour with simplicity and elegance. However no special technology or equipment is needed for making these composites, only for peeling bamboo veneer.

The fibre length, chemical composition, and the cellulose content of bamboos are similar to those of wood. Most of the bamboo species in China provide excellent raw material for producing pulp for paper. Schizostachyum and Dendrocalamus species have over 50% of cellulose, with the length of the fibre reaching over 3 mm.

Bamboo artificial board, bamboo-based composite board, bamboo parquet, bamboo floor board and other bamboo products are also used for furniture, vehicles, packaging and in architecture. Those new kinds of bamboo based material are used by Dai, Hani, Wa and other tribes; people in the South part of Yunnan province to substitute the traditional old bamboo house that was made with raw bamboo culms and rough bamboo mat. The modern bamboo house is more stable and lasts longer. Bamboo buildings and bridges built in France and Germany, have attracted many Europeans. Relevant properties of bamboo products are shown in Tables 2-6.

Table 2. Performance of bamboo plywood
(Test standard: Chuan Q533-84)

Test items	Type 1			Type 2
	Super class	First class	Second class	Super class	First class	Second class
Static bending strength (kg/cm2)	1000	800	600	900	700	500
Boiling-drying (periods)	6	5	4
Soaking-drying (periods)				3	2	1.5

Note:

a. Conventional bamboo plywood type 1 is glued with adhesives such as Arcolite or other equivalents. The plywood is characterized as weatherproof, water resistant material, suitable to outdoor usage.

b. Conventional bamboo plywood Type 2 is glued with adhesives such as NQ-TS pollopas or other equivalents. The plywood can be soaked in cold water and can resist short time hot water soak, but never resists boiling. This plywood is suitable for indoor usage.

Test items	First class	Second class
Static bending strength (N/m.m2)	>18	>15
Plain tensile strength	>0.4	>0.3
Moisture thickness buckling	<6%	<11%

Notes:

a. Moisture under test: 5-11%
b. Density 0.5-0.85 g/cm³

Volume-Weight (g/cm3)	0.74-0.78
Moisture content of air dried board (%)	12-14
Shrinkage (%) at 5-15% moisture content	1. horizontal	0.027
	2. vertical	0.140
	3. radial	0.072
Crush strength (Mpa)	15.4
Hardness (Mpa)	58.1

Notes:

a. Thermal conductivity: 0.1802 W./M. degree C

b. Electric resistance: 32.11X10⁶ Ohm. M.

c. Acoustic absorption: 0.273(125Hz), 0.182(250Hz), 0.202(500Hz), 0.077(1KHz), 0.155(2KHz), 0.298(4KHz)

	Name
Items	Dendrocalamus giganteus	Gmelina arborea	Tectona grandis	Quercus altissima	Pinus massoniana
Moisture content of (%)	10	12.1	15	14.8	14.6
Volume Weight (g/cm3)	788.5	509.0	479.0	963.0	450.0
Horizontal Hardness (Mpa)	0.139	-	0.221	0.332	0.169
Bending Strength (kg/cm2)	1405.0	1059.3	1032.0	1260.0	883.0

Table 6. Comparison of structures made from Phyllostachys pubescens and Pinus yunnanensis

Test Items	Bamboo	Wood
Horizontal Tensile Strength (kg/cm2)	2112.30	1179.50
Horizontal Compressive Strength (kg/cm2)	490.70	461.00
Bending Strength (kg/cm2)	1399.30	917.20
Modulus of Elasticity-Tensile (kg/cm2)	21X104-
	37.89X104
Modulus of Elasticity-Compressive (kg/cm2)	1612.90-
	2433.60
Modulus of Elasticity-Bending (kg/cm2)	10.38X104-	12.9X104
	12.65X104

Conclusions

It is possible for bamboo to substitute wood as a raw material. It is feasible to encourage investment in bamboo industry where bamboo is in sufficient supply. This will result in considerable economic benefits.

Concerned international organizations and local governments should adopt useful policies to use bamboo resources, particularly in China and Southeast Asia, to substitute bamboo for wood, in any possible industrial use and also to strictly limit cutting of wood and deforestation. This will be a significant contribution to the improvement of natural resources and solve many ecological problems.

Rational plans should be developed and carried out to make use of bamboo resources, so that the existing bamboo forests would not be destroyed, as wood forests have been. At the same time, there are advantages of using cultivated bamboo with its short rotation period. With improved practices there should be more bamboo wood for industries and edible shoots for human consumption.