WORLD MARKET POTENTIAL FOR BLEACHED BAGASSE

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1 L, Manufacturing - By-Products WORLD MARKET POTENTIAL FOR BLEACHED BAGASSE >., PULP- A TECHNICAL REVIEW i Ti'>' Eduardo J. Villavicencio W. R. Grace & Go, New York, NY ABSTRACT A brief review is given of bagasse fiber's anatomic and chemical composition to comprehend some of its similarities and differences with hardwood fibers. A comparative evaluation is presented of bagasse fiber digestion with caustic soda, kraft and alkaline sulfite processes with significant results in both technical and economic areas in favour of the alkaline sulfite pulping of bagasse. Considerable studies are analysed at laboratory, pilot plant and mill scale trials on bagasse bleaching to obtain 90" plus Elrepho brightness. Evaluation is made of the CEHD versus the CEDH sequence and development of an ideal DcEDH sequence for bagasse four-stage bleaching is given. Characteristics of the market grade bleached bagasse pulp of 90" plus Elrepho brightness are compared against commercial~ardwood pulps. INTRODUCTION Historically, the paper industry has changed its raw material for pulp h and paper making from mixtures of wood waste and cotton rags to long fiber woods such as spruce, fir and pine and then to the short fibered hardwoods as cost conditions changed and new technologies developed. The conditions foreseen for the future should accelerate the use of new fiber sources especially bagasse, the fiber produced from sugarcane residue. Bagasse produces a superior quality short fiber pulp which can replace hardwood pulp in virtually all paperlboard machine applications. Today, bagasse pulp offers an unsually good combination of technical and economic factors that makes it one of the most competitive of the new fiber sources. In the technical area, no pulp, neither short nor long fiber is 100% equivalent to any other pulp. Each pulp offers a spectrum of qualities utilised or adapted by the paper maker. The fact that bagasse pulp has the technical qualities enabling it to be substituted for hardwood pulp is best illustrated by the many years of commercial success in making major types of pulp, papers and board for the paper industry in America, Europe, Africa and Asia. More than a million tons of bagasse pulp were produced in In addition to meeting required technical qualities, the marketability of any fiber offered to meet the future demand for short fiber pulp depends on its profitability relative to other fibers and its ability to attract investment capital. "At optimum size the capital investment cost per ton of output for a bagasse mill is approximately that of a conventional hardwood pulp mill or slightly less, assuming the infrastructure and support facilities are in place. Additionally, with the major exception of the fiber component, the operating costs of all mills of a given size are generally about the same. Therefore, the key variables

2 I EDUARDO J. VILLAVIGENGIO 1783 affecting the relative profitability of the different fibers are the fiber cost, the price at which the pulps can be sold; and the pulp acceptance into the paper industry." (Sundelin, Arne. World Market Potential for Bleached Bagasse Pulp. Prepared for Process Evaluation and Development Corp (PEADCO), May 1972.) It is the purpose of this paper to review the technical characteristics of the bleached bagasse pulp and to compare them with the well established ones of the hardwood bleached pulps and to give a clear technical picture of the future of bagasse pulp in the paper making industry. BAGASSE PULP Heretofore bagasse pulp has been used primarily in captive mills. Extended experience has been accumulated in its manufacturing technology as well as in its final use. Market pulp today requires specific characteristics from the pulp in order to compete and be accepted into the sophisticated market of short fibers known as hardwoods. To a great extent, the characteristics of bagasse pulp depend on the technical procedure followed in manufacturing the pulp and to a lesser extent the sugarcane variety and sugar mill operation. A brief review of the bagasse fiber from its anatomic composition and its chemical analysis will be helpful in order to understand some of its similarities and differences with hardwood fibers. The physical composition of sugarcane bagasse appears in Table 1. The quality of the bagasse pulp is directly related to the fiber classification and selection which is known as depithing. The presence of pith in the pulp imparts undesirable characteristics to the pulp during the wet and dry paper making operation as well as to the finished paper. Pulp slowness and paper brittleness reflect lack of efficiency in the pith removal stage. Good moist and wet depithing of the bagasse are today considered essential in any pulp mill design. For high yield pulping it is,necessary to have an acceptable clean bagasse fiber free of pith, sand, trash and solubles. TABLE 1. Sugarcane bagasse fiber physical composition. Pith Parenchyma cells 20% Other nodes, etc. 5% 25% - Paper making True fibers 55% fibers Vessel segments 20% 75% - Total 100% The fine structures of the bagasse true fiber is similar to that of other bast fibers and of softwood and hardwood tracheids, with one primary wall and three distinct secondary wall layers. The fibrillar structure of these layers is also of the usual type. Thus, on the whole the bagasse true fiber fraction is similar to that of hardwoods. The chemical composition of bagasse does not deviate materially from that of hardwood in percentages. However, there is some difference in the type of lignin and hemicellulose ratios (Xylans/Arabino) as can be observed in Table 2.

3 1784 MANUFACTURING - BY-PRODUCTS TABLE 2. Chemical composition of some hardwoods and bagasse fibers. Gross composition % Cellulose Hemicellulose Lignin a) Hardwoods Aspen trembling (Populus Tremuloides) White elm (Ulmus Americana) Beech (Fagus Grandifolia) White birch (Betula Papyrifera) Yellow birch (Betula Lutea) Red maple (Acer Rubrum) Hardwoods average b) Bagasse washed clean fiber Peruvian Chiclayo variety CH ,3 21,7 Peruvian - Paramonga variety CH-32 48,lO 29,5 22,4 a) Pulping Processes - Sven A. R~dholm, page b) PEADCO research reports. When comparing bagasse sugarcane varieties on pulping, very little difference is found if the clean fiber has been properly prepared. However, there is definitely an effect of climate and soil conditions in the same studied variety, as can be seen in Table 3. BAGASSE PULPING Based on the chemicals used to pulp the bagasse clean fiber, there is certain similarity in the pulping of woods and the pulping of bagasse. However, the physical and chemical characteristics differ so that that the manner in which the 2 types of materials are handled is quite different. Penetration of the cooking chemicals into the bagasse washed clean fiber is high as compared to chip wood; lignin and hemicellulose (Xylans) distribution in the bagasse fiber, especially in the rind fibers exposed to weather and protection of the cane are chemically tempered and waxes of high melting point cover their surface. It is known that these fibers are the longest of sugarcane as can be seen in Table 4. Table 5 shows the dimensional characteristics of hardwood fibers for comparison purposes. If fiber dimensions and average ratio lengthldiameter of bagasse and hardwood puips are compared, it can clearly be established that although they are similar, bagasse fibers from the point of view of paper making usually behave better than the hardwoods. TABLE 4. Dimensional characteristics of bagasse. (For Table 3 see over) Ratio Length, milimeter Diameter, micron Length/ Min Avg Max Min Avg Max Diameter True fiber 0,80 1,70 2,80 10,2 20,O :l Parenchyma 0, Vessel segments 1, Pulp and Paper Prospects in Latin America. United Nations. New York. p 246.

4 TABLE 3. combined research work: Field - Sugar mill - Paper mill. Analyses and cooking of bagasse from different sugarcane varieties. Cane variety CH - 32 CH- 37 CG Field name San Don Idelfonso Pepe Canaval Corrales Bernabe Alameda Aranzazo Zapallo Carreteria Camotillo Estacada Test, no Cut, no. 2nd 2nd 1st 1st 2nd 1st 3rd 3rd 3rd 5th 3rd Cut age, months 15,2 15,l 16,l 18,O 17,8 19,2 14,2 16,l 15,5 14,2 14,8 Fiber yield, % 53,8 54,2 '53,2 54,6 55,O 54,O 51,6 53,9 53,8 52,8 53,8 Fiber, % 63, ,8 63,r 63, ,0 6 3 ~ Pith, % 37,O 36,8 36,8 36,6 36,2 36,9 37,O 37,2 36,9 37,O 36,7 Solubles Whole Bagasse In cold water, % 16,6 17,5 17,3 16,8 17,2 18,8 18,2 13,8 17,6 15,8 17,O In hot water, % 17,7 18,8 18,2 17,4 18,4 19,7 19,l 15,l 18,9 17,2 18,5 In alcohol, % ,9 &I 10,7 12, ,l 10,7 9,5 In 1 % caustic soda, % 37,9 36,2 37,8 39,6 37,2 39,5 39,6 37,6 40,2 37,8 40,5 Accepted Fiber In cold water, % ,5 5,9 6, ,6 4,O 5, In hot water, % 7, ,6 5,O ,3 In alcohol, % 393 2,9 3,1 3,4 3, ,6 2,9 3,6 In 1 % caustic soda, % 29,9 28,O 29,5 30,2 29,2 29,O 30,l 28,5 30,8 31,l 31,2 Cooking % 12,O 12,O 12,O 12,O 12,O 12,O 12,O 59,O 58,7 61,4 60,9 54,3 59,8-55,8 Caustic soda used, Yield, % 12,O 58,O 12,O 58,8 12,O 58,2 12,O 59,7 KMnO,, number 25,O 22,5 23,7 25,l Physical test at 19,7 22,O 24,O 25,7 23,4 22,6 23,7 Freeness SR 650 ml Tear, factor 48,7 61,3 70,O 69,O 81,3 65,5 64,O 61,2 65,l 68,5 67,5 Tensile, mts Burst, factor 26,7 34,4 27,8 31,O 29,2 Freeness SR 500 ml 31,O 28,O 31,4 34,5 33,4 29,5 58,5 59,3 55,O 59,5 62,8 60, Tear, factor Tensile, mts 39, , , ,l , Burst, factor 30,7 40,5 33,7 38,O 32,4 35,2 31,7 35,O 40,5 36,5 36,5 Source: Peadco Research Report LI

5 1786 MANUFACTURING - BY-PRODUCTS TABLE 5. Dimensional characteristics of hardwoods. Ratio Length, milimeter Diameter, micron Length/ Min Avg Max Min Avg Max Diameter Aspen 1,o 26 40:l Red Gum 1,6 50:1 Birch , :l Rydholm, Sven A. Pulping Processes p ( i L,' TABLE 6. Comparative evaluation of sodi, kraft and alkaline sulfite cooks of bagasse fiber. (8) Soda cook (8) Kraft cook (b) Sulfite cook average average average 3 tests 3 tests 3 tests Chemicals, '$(, 14,13 14,13 14,13 Yield, % 53,58 55,74 75 KMnO,, no. 19,4 19,l 18,5 Brightness, Elrepho 31,5 27,5 48,O Physical test interpolated at cc SR Freeness,ii Tear, factor 62,2 60,8 62,O Tensile, mts ' Burst, factor 29,7 31,3 40,9 500 cc SR Freeness Tear, factor 56,5 54,2 55,O Tensile, mts Burst, factor 34,4 36,6 43,5 Bleaching - 5% NaOCl ' Yield, % 95,9 96,O 96,O Brightness, Elrepho 41,O 41,O 65,O Physical test interpolated at 650 cc SR Freeness Tear, factor 60,6 62,2 60,O Tensile, mts Burst, factor 34,5 38,5 41,O 500 cc SR Freeness Tear, factor 54,6 54,3 55,3 Tensile, mts Burst, factor 40,9 43,4 43,O Viscosity, Tappi cps 22,5 24,5 42,8 a) Peadco Research Report, July 20, 1970, "Bagasse Fiber Kraft Pulping Versus Soda Pulping". b) Peadco Research Report no. 223, June 4, Of the tons of bagasse pulp produced in 1972, practically. all the pulp with the exception of tons produced in Taiwan was digested with caustic soda. The pulp in Taiwan was digested with kraft liquor (sulphatel caustic soda). Table 6 exhibits a comparative evaluation of soda, kraft and alkaline sulfite cooks of bagasse fiber. As can be observed in Table 6, cooking with different chemicals can impart different characteristics to the bagasse pulps; however, caustic soda versus kraft cooking of bagasse does not present much difference in pulp quality, physical characteristics and yields. We can call

6 I EDUARDO J. VILLAVICENCIO 1787 them practically identical and that is why caustic soda cooking has been more widely used for bagasse cooking plus the consideration that caustic soda does not give air pollution and corrosion problems. However, when comparing bagasse caustic soda or kraft cook versus sulfite cook the difference is greater and more significant in both technical and economical aspects in favor of the sulfite cook. Sulfite pulp is higher in yield as can be seen in Table 6 and physical properties in general are superior to those of caustic soda and kraft cookings. Viscosity expressed in cps is almost twice and it influences the strength of the pulp as well as its suitability for dissolving pulps (if hemicelluloses are reduced previously). BLEACHING OF BAGASSE PULP Considerable studies on bagasse bleaching have been carried on in order to obtain a 90" plus Elrepho brightness pulp that will compete with hardwood pulps in quality and international prices. In this field, the studies were accomplished with the collaboration of Hooker Chemicals, Improved Machinery, Allied Chemicals, Modocell AB, L'Air Liquide/Kamyr Inc and the Herty Foundation. All the technical work has been directed by the PEADCO ResearchlTechnical Group. The CEHD sequence (chlorine/caustic extraction/hypochlorite/chlorine dioxide) - the most adopted sequence for hardwoods bleaching - was evaluated. The conclusion was arrived at that through this CEHD sequence it was technically impossible to achieve a bagasse pulp of 90" plus ~ lre~ho brightness without submitting the fiber to a strong degradation, subsequent brightness reversion and low cooking and bleaching yield (refer to Table 7). An improved sequence was found by reverting this sequence and using the chlorine dioxide prior to the hypochlorite stage (CEDH). In this case, it was possible to reduce the total amount of chemicals, increase the brightness and viscosity, and decrease the brightness percent of reversion as can be observed in Table 8, Pulp Sample # 2. Furthermore, with the introduction of a small amount of chlorine dioxide in the first stage of chlorination (DcEDH), it was possible to hold the brightness, reduce again the total amount of bleaching chemicals, increase the viscosity of the final bleached pulp and reduce to a minimum the brightness percentage of reversion - (refer to Table 8, Sample # 2, Experiment no. 19). An increase of 3 points in yield (caustic soda cook) also brings an increase in the K number of the pulp from 13,2 to 16,7 (Table 8, Sample # 8, Experiment no. 6) which gives a better bagasse pulp (higher wire drainage and physical strengths), although the total required chemicals for bleaching is also increased. When bagasse fiber is cooked with sodium sulfite, the yield is higher than that of the caustic soda cooking for the same K number of the pulp (refer to Table 6). A bleaching study was also conducted on bagasse sulfite pulp in order to appreciate its bleachability versus increase in pulp yield. Table 9 shows the response of the sulfite pulp to the same DcEDH sequence adopted for the soda pulp. After reviewing the bleaching work conducted on bagasse fiber in order to obtain a market grade pulp of 90" plus Elrepho brightness, it can be concluded that the 4-stage DcEDH sequence (chlorine and chlorine dioxide as one step/caustic extraction/chlorine dioxide/hypochlorite) has given the best

TABLE 8. A comparative evaluation of bleach response, pulp properties, and levels of chemical application for bagasse soda pulp to 4 and 5 stage bleaching sequences.

8 TABLE 8. A comparative evaluation of bleach response, pulp properties, and levels of chemical application for bagasse soda pulp to 4 and 5 stage bleaching sequences. Brightness, % Total Chemical Application, % MP Reversion, % sample no. Source K no. Sequence Exp no. 3rd stg Final A1 hr A18 hrs Visc cp Eq C1,% C1, % C10, % NaOH %* 2 Peru 13,2 CEHD 5 83,3 90,4 2,7 5,5 14,2 7,32 6,OO 0,50 4,90 CEDH 7 84,8 91,5 1,5 4,4 17,6 6,84 5,OO 0,70 3,39 CEDED 10 75,3 91,l 1,l 3,O 19,4 5,82 4,50 0,50 3,25 DcEHD 18 84,9 91,3 1,2 3,8 17,3 6,82 2,80 1,53 4,15 DcEDH I9 86,7 92,5 1,2 3,l 17,6 6,84 2,75 1,55 3,39 8 Peru 16,7 DcEDH 6 85,9 90,3 1,4-14,5 9,63 3,75 2,24 4,OO (Herty-1) DcEDHD 15A 83,2 89,8 0,9 3,2 17,O 10,16 3,75 2,44 4,24 DcE/HDH 11 85,2 87,8 0,7 3,8 17,9 10,13 4,25 2,24 4,60 9 Peru 17,5 DcEDH 2 87,l 90,l 0,8 3,l 17,5 10,13 4,OO 2,33 4,OO (Herty-2) 10 Peru 15,5 DcEDH 16 87,9 90,3 1,0-11,5 9,43 3,80 2,14 4,68 (Herty-3) DcEDED 17 88,5 90,2 0,4-16,l 9,94 3,OO 2,64 4,20 DcEDE/H 19 88,9 89,5 0,3 13,8 9,98 3,30 2,54 4,14 DcEDD 18 88,5 89,9 0,5-17,6 9,94 3,OO 2,64 3,90 11 Peru, 13,O DcEDH 1 88,5 90,7 1,2 3,O 11,9 6,94 2,80 1,58 3,44 :(-Jap&) DcHsDH 3 88,8 90,2 1,4 4,O 13,O 7,32 4,OO 1,26 3,70 DcHsED 6-89,7 1,4 3,O 16,4 7,42 3,80 1,38 3,40 6 Australia 17,O DcEDH 2 84,4 89,6 1,2 3,l 14,5 7,87 2,50 2,04 3,18 * Includes NaOH for ph Adjustment Source: "The Development of a Four Stage Bleaching Sequence, DcEDH, for Bagasse Soda and Sulfite Pulp". Report from Hooker Chemical Corporation to PEADCO.

9 TABLE 9. A comparative evaluation of bleach response; pulp properties, and levels of chemical application for bagasse sulfite pulp to 4 and 5 stage bleaching sequences. pulp sample no. Source K no. Sequence Exp no. 3rd stg Final Brightness, % A1 hr A18hrs Total Chemical Application, % 3 Australia 15 CEDH 36 84,2 88,3 2,O - - 7,67 5,30 0,90 3,96 DcEDH 19 82,3 86,7 1,7 5,3 24 7,96 2,80 1,96 3,12 CEDEIHD 30 82,4 87, ,43 5,OO 1,30 4,06 Composite -7 Australia 15 DcEDH 1 85,5 90,5 1,4 3,4 22,9 6,08 2,lO 1,51 3,12 Unscreened-4 Peru 18,5 CEDH CEDEIHD 3 81,3 90,O 1,l 4,6 5 Peru 14,7 DcEDH 2 82,6 - * Includes NaOH for ph Adjustment.

10 EDUARDO J. VILLAVICENCIO 1791 results in both cost of bleaching as well as pulp physical characteristics. The laboratory conclusions were confirmed on the bleaching pilot plant of the Herty Foundation. Under the responsibility of the Peadco Research Group, the supervision of Hooker Chemicals and the assistance of the Herty Foundation personnel, a series of 5 bleaching trials were successfully conducted on the Herty continuous bleaching pilot plant equipped with chlorine dioxide generator. A total of 500 pounds first quality, in commercial type sheets, 90" Elrepho brightness bagasse pulp was produced during these trials. Further to the pilot plant trial, a complete run of 50 tons caustic soda pulp was conducted by the Marubeni Corporation, Materials & Products Department in their Nagoya Pulp and Paper Mill in Japan. The unbleached pulp was shipped from our Paramonga, Peru operations. Once again the success obtained in bleaching the bagasse soda pulp to commercial bleached market pulp has been demonstrated and there can be optimism about its acceptance into the world market when the bagasse bleached pulp is compared with commercial hardwood pulps. COMPARATIVE STUDY OF BLEACHED BAGASSE PULP AND BLEACHED HARDWOOD KRAFT PULP Physical characteristics of the bagasse pulp bleached on the Herty pilot plant were evaluated and compared against the market grade pulps available in the world today. Table 10 exhibits the good characteristics of the bagasse pulp; in the case of the soda cook - it is outstanding for opacity, brightness and tensile. Bulk and density are average and tear is comparable to that of the Eucalyptus Celbi pulp. Dirt count is certainly acceptable. Testing of the pulps was done according to TAPPI Standard Procedures T200 6s-66, laboratory processing of pulps (beater method) T205 M-58 forming handsheets for physical test of pulp; and T220 M-60 physical testing of pulp handsheets., TABLE 10. Comparative study of bleached bagasse pulps and bleached hardwood kraft pulps. Regular bleached Premium hardwoods bleached Bleached hardwoods Bagasse Hudson Burgess Hammer- Celbi B1 Prime Brown mill Westvaco Euca- kraft soda sulfite Co lyptus birch InitialOpacity,% 74/78 84/87 76/80 77/82 81/83 69, Original Brightness, G.E. 90,5 88,7 88, / ,5 Tear Factor* ,7 44,8 Tensile, mts.* Burst Factor* ,4 62,O Bulk, cc/g* 1,52 1,47 1,49 1,39 1,39 1,30 1,40 1,60 Density, g/cc* 0,66 0,68 0,68 0,72 0,72 0,77 0,68 0,76 Dirt count, ppm 0,5 0,2 0,2 0,4 0,9 < 1,0 <1,0 <l,o Sourcet * Properties at 500 cc SR Freeness. t Source refers to number of reference in Peadco Research Reports.

11 1792 MANUFACTURING - BY-PRODUCTS CONCLUSIONS As a result of several years of commercial experience in the manufacture of pulp and paper from sugarcane bagasse followed by our own research work and contracted facilities which culminated in recent pilot and commercial plant trials, the following conclusions can be reached : a) Bleached bagasse pulp of 90" Elrepho brightness obtained through the DcEDH sequence has a high opacity (80%) which certainly is better than average. b) The bleached pulp has excellent paper making characteristics which enables it to compete with f~~i'dwood bleached pulps in the market. c) The dirt count of the pulp produced was acceptable (less than 1,O TAPPI Standard). It can be improved by following the PEADCO Process bagasse flotation followed by wet depithing. In general, it can be stated that the bagasse pulp obtained through our process meets the pulp market standards and certainly is an excellent product to assist the WOI-19 pulp shortage. However, it is important to note that the bagasse pulp advantage in cost, and today in quality, as developed by our group requires that each project for plant construction be evaluated in detail and on its own merits, taking into consideration the conditions specific to a particular mill site, the potential customers and markets and the financing conditions. ACKNOWLEDGEMENT We would like to express our gratitude to Hooker Chemicals, Niagara Falls, New York, the Herty Foundation, Savannah-Georgia, and Sociedad Paramonga Ltda, Paramonga-Peru, whose continued collaboration and efforts made possible the successful development of our investigations to obtain a market grade bleached bagasse pulp. POTENCIAL DEL MERCADO MUNDIAL PARA LA PULPA DE BAGAZO TERIDA REVISION TECNICA Eduardo J. Villavicencio RESUMEN Un breve repaso de la composicion anat6mica y quimica de la fibra del bagazo para comprender algunas de sus similitudes y diferencias con las fibras maderables. Una evaluaci6n comparativa de la digesti6n de la fibra de bagazo con soda ciustica, kraft y sulfito alcalino con resultados significativos en ambas ireas, t6cnica y econbmica, es presentada en favor de la pulpa de bagazo con sulfito alcalino. Considerables estudios de blanqueo de bagazo en laboratorio, planta piloto y prueba a nivel de factorias se analizaron, para obtener 90" y mis de brillantez Elrepho. Evaluaci6n del CEHD contra la secuencia CEDH y el desarrollo de una secuencia ideal DcEDH para la cuarta etapa del blanqueo del bagazo. Se cornparan las caracteristicas de la pulpa de bagazo en el mercado con 90" y mis de brillantez Elrepho con las pulpas maderables comerciales.

Nalgrass: A Nonwood Fiber Source Suitable for Existing US Pulp Mills

Reprinted from: Trends in new crops and new uses. 2002. J. Janick and A. Whipkey (eds.). ASHS Press, Alexandria, VA. Nalgrass: A Nonwood Fiber Source Suitable for Existing US Pulp Mills Mark Lewis and