0335-A2

Future fibers for pulp mills in Bangladesh

M. Sarwar Jahan ¹

Abstract

Bangladesh are facing acute shortage of fiber for pulp and paper industry. On the other hand, the demand of paper and paper products is increasing day by day. Nonwood or agro-based fibers are potential sources for pulp production. However, these fibers have tremendous variations in chemical and physical properties compared to wood. This study presents the availability of nonwood raw materials for pulp production in Bangladesh and focused its quality. It is also discussed the problems related to nonwood pulping. Bangladesh have huge amount of unused jute fiber, which is the best source for pulp production in Bangladesh. Other agricultural wastes like cotton stalks, corn stalks, Dhaincha, Straw etc. may be used for pulp production. Jute pulp may be used as reinforcing agent with other nonwood pulps for better quality paper. Big pulp mills could be established based on jute and a few small pulp mills may be set up based on agricultural wastes. An integrated pulp mill may also be established depending on different nonwood raw materials.

INTRODUCTION

The basic raw materials for pulp and paper industries come from forest. Currently 90% of chemical and mechanical pulps are produced from wood. The global consumption of paper and board increased to 314.4 millions ton in 1999 from 231.6 million ton in 1989 (Anon 1990; 2000). This increase is expected to rise further with increasing world population, literacy rate, and quality of life. The continued high growth in paper consumption will lead to increase demand of fiber, creating additional pressure on the world diminishing forest resources. To maintain the growth of paper industry, thereby increasing supply of raw materials, government as well as executive of industry have to take a policy of reforestation, plantation management, recycling and development of alternative fibrous raw materials, such as annual plant, agricultural wastes, which are commonly called nonwood.

In Bangladesh paper industry is using bamboo and mixed hardwood. Both of these raw materials come from forest. Presently about 38,000 acrors of forest is being used for pulp and paper industry. Tribal peoples live in the forest region of Bangladesh. Traditionally, they use land for jhoom cultivation. Therefore, huge amount of forest is destroyed during jhoom cultivation. Hence allocated forestland for paper industry could not meet the demand. On the other hand the gap between demand and supply of pulp and paper in Bangladesh is increasing day by day. Therefore, more pulp and paper industry is needed which demanding more fibrous raw materials. This article describes the possibility of utilization of nonwood raw materials for pulp production.

NONWOOD FIBERS

In general, fibers can be classified into three categories wood, nonwood and nonplant. The term `nonwood' was to distinguished from the two main sources of wood fiber hardwoods and softwoods. Nonwood or ago-based fibers are derived from selected tissue of various mono- or dicotyledonous plants and are categorized botanically as grass, bast, leaf or fruit fibers.

Some nonwood fibers are classified by means of production; fibers such as sugar cane bagasse, wheat straw and corn stalks are by products. Other nonwood fibers are grouped as "fiber plants" plants with high cellulose content that are cultivated for the sake of their fibers such as jute, kenaf, flax etc.

GLOBAL AVAILABILITY OF NONWOOD FIBER

In commercial development, there must be a long term guaranteed supply of resources. In order to insure a continue fiber supply, management of the agricultural producing land should be under a proactive system of land management whose goal is both sustainable agriculture and the promotion of healthy ecosystems.

Worldwide, nonwood pulping capacity was 23 million ton/yr in 1997, which represented 10.9% of total paper pulp capacity. By 1998, it was reached to 24.1 M ton/yr (11.2%). Since 1975, nonwood pulping capacity has grown at more than double the rate of wood pulping capacity, with the period 1993-98 averaging 3.4% pa (as compared with 1.2% pa for wood pulping). Most nonwood pulp is used in integrated mills, but some pulps and raw material are imported into developed countries for the manufacture of specialty grade papers and environmentally friendly paper grades. Some long fiber length nonwood pulps are used in nonwovens (eg: cotton).

Table-1 shows the estimated annual availability of nonwood fibrous raw materials worldwide - and thus the potential material for further expansion. Corn stalks contribute the highest amount of nonwood fiber. Among the straw fibers wheat straw contribute largest amount followed by rice straw.

AVAILABILITY OF NONWOOD FIBER IN BANGLADESH

Table 2 shows the availability of nonwood fiber in Bangladesh. There is no data available on agricultural wastes in Bangladesh. Data reported here based on the production of crops. Agricultural wastes were calculated by the ratio of crops and wastes from one acore of land. It is clearly seen from the Table 2 that rice straw is the highest agricultural waste followed by bagasse and wheat straw. Also huge amount of jute is available in Bangladesh.

CHEMICAL AND PHYSICAL PROPERTIES OF NONWOOD

The data of chemical and morphological characteristics of nonwood shows wide variation from one raw material to others (Table 3). Nonwood raw materials contain lower lignin compared to wood. Its fiber length is similar to hardwood. But fiber length of jute and bamboo is similar to softwood. Ash content is higher as compared to wood, which creates difficulties during recovery. Rice straw contains highest amount of ash.

PULP PROPERTIES OF NONWOOD PULPS

On a worldwide basis, the future use of nonwood fibers on a large scale is indeed a reality. For a medium- and long-term future, greater use of these raw materials in the world will become a reality as well. About 11% of world pulp production are made from nonwood fibrous raw materials, some of which are agricultural raw materials. Most nonwood pulp is produced in China and India. These two countries account 80% of the total nonwood pulp production. Bangladesh have potential nonwood fibrous sources for pulp production. Pulping properties of a few important nonwoods of Bangladesh is given below;

Jute

Jute is abundantly grown in Bangladesh. Jute has a long historical role in the socioeconomic development of Bangladesh. Once jute was known as golden fiber of Bangladesh. The export of jute and related products accounts for a significant portion of total export. In addition, it provides considerable employment opportunities to the country's work force. Traditionally jute was used in backing, sacking, gunny bag, hasein etc. In recent years, jute has faced stiff competition from synthetics. Therefore, traditional uses of jute have declined. As a result, its demand in local and overseas markets has been shrunk. This has caused jute prices drop and jute growers are the ultimate victims. Therefore, diversified usage is needed to regain the lost glory of jute. The chemical and morphological characteristics of jute favor it as pulping raw material (Akhtaruzzaman et al 1988; Nahar, N. 1987). In the northern region of Bangladesh, about 0.2 million ton of jute remain unused in every year due to its low quality in traditional uses. Therefore, farmers don't get proper price. But it produce a good quality pulp, pulp yield is above 60% with kappa number less than 20. The papermaking properties are very high like softwood pulp (Akhtaruzzaman and Shafi 1993). The SR number of unbeaten pulp is below 15, which are acceptable for subsequent processing. Utilization of jute in pulp production creates a new horizon for farmers.

If whole jute plant is used in pulping, pulp yield is about 45-50% with kappa number about 20-25. Whole jute plant consists of stick (woody portion) and bark (fiber) in the ratio of 2.5:1. Stick contains high lignin and has short fiber length, hence pulp produced from whole jute plant shows higher tensile but low tear strength as compared to jute fiber pulp. The SR number is above 15, so whole jute plant pulp need special design equipment for pulp washing.

Straw

Straw can be an important source of raw materials for the production of paper. Cereal straw, in particular wheat straw is a major source of pulp for paper production in China and other Asian countries. The high silica content of rice straw (9-14%) however prohibits the economic use of rice straw for this purpose. The silica will cause problems in the recovery of chemicals used in the pulping process. For rice straw, there is currently no commercially available solution for this problem. Other problems with the use of straw for pulp are the higher water retention capacity of straw, the lower yield per ton of raw material compared to wood (straw yields 45% of pulp whereas wood yields 55% pulp), and the low bulk density of straw. A little study has been made on straw pulping in Bangladesh. Bangladesh produce huge amount of rice straw and wheat straw. Therefore, more study should be done straw pulping. A method should be developed on the desilication of rice straw.

Cotton stalks

After cotton cultivation, stalks are remained in the field. Now it is being used as domestic fuel in the rural area in a limited extent and rest is left in the field. Disposal of the stalks increases production cost of the farmer. Therefore, it is burnt in the field, which is not environmental friendly. Utilization of this agricultural waste reduces the production cost of cotton. It is a wood like nonwood raw material. The chemical and morphological properties of cotton stalks are comparable to hardwoods. The pulp yield is about 40-45% with kappa number 30-35 (Jahan et al 2001). The SR number of unbeaten cotton stalks pulp is about 12-15. The tensile strength of cotton stalks pulp is very high but tear index is very low. Blending cotton stalks pulp with jute pulp could increase tear index (Jahan 2001). The bleachability of cotton stalks pulps is very good in ECF bleaching (Jahan et al.2002).

Corn stalks

The chemical and morphological characteristics of corn stalks are comparable to hardwood species. It is easier to delignify than wood. Corn stalks require lower temperature for pulping. The pulp yield is about 50% at kappa number 20 (Jahan 2002). The papermaking properties are very good except teat strength. Blending of corn stalks pulp with jute pulp increased tear strength (Islam and Jahan 2001). Due to high fine content water retention is very high. Therefore, pulp-processing equipment should be similar to straw pulp mill.

Bagasse

One pulp mill in Bangladesh is based on bagasse. Bagasse is a by-products of sugar mills. Sugar mills in Bangladesh use bagasse as fuel for steam generation. Therefore, sugar mills consume almost all bagasse. Recently, Bangladesh government connects gas pipeline in the northern region, where almost sugar mills are situated. If sugar mills use this gas for steam generation then bagasse can be used for pulp production. Pith is the main problem for bagasse pulping. It creates problem during pulp washing, clogging in machine wire etc. Therefore, pith must be removed before pulping and also fiber treatment is needed.

Kash (Saccharum spontaneum)

Saccharum spontaneum is produced the wet and sandy land. It is similar to bagasse. In Bangladesh it is called Kash and in India it is Kan grass. Now it is used as fencing in rural area to a limited extent. About 20 thousands metric tons of S. spontaneum is available in Bangladesh. Pulp yield from Saccharum spontaneum is very high and kappa number is very low (Jahan et al. 2002). The initial brightness (about 50%) of S. spontaneum pulp is suitable for newsprint. The papermaking properties are comparable to tropical hardwood (Miller and Gounder 1986).

Dhanicha

Dhanicah is grown in sandy region of Bangladesh. It protects land from erosion. It also fixes nitrogen to the soil. Therefore, it is most useful annual plant for our agricultural system. Now it has no industrial uses but it is used as domestic fuel in the rural area. Chemical and morphological properties favor it as pulping raw material. Pulp yield and kappa number are similar to hardwood. The papermaking properties of dhanicha are also similar to hardwood.

CONCLUSION

From this investigation it may be concluded that:

• Jute is the best source for pulping in Bangladesh.
• Cotton stalks, Corn stalk, Dhanicha, Straw etc. may be used as pulping raw materials in Bangladesh.
• Blending of jute pulp with other nonwood pulps may produce better quality of pulp.
• An integrated pulping system may be adapted for nonwood pulping.
• Inventory of nonwood raw materials in Bangladesh is needed.

LITERATURE CITED

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¹ Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Dr. Qudrat-E-Khuda Road, Dhaka-1205, Bangladesh