Characterization, Utilization, And Optimization of Ethiopian Sugarcane Bagasse (Saccharum Officinarum L.) For Pulp and Paper Making
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Date
2020-06
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Addis Ababa University
Abstract
The current global awareness about the use of non-wood biomass for pulp and paper production
has resulted in significant reduction of deforestation. Based on this, the dissertation investigated
the suitability of Ethiopian sugarcane bagasse (ESCB) (Saccharum officinarum L.) for the pulp
and paper production. The study is focused toward the physical fractionation pretreatment of the
Ethiopian sugarcane bagasse aiming at the reduction of its lignin, extractive, silica, and ash
contents to improve the pulping process. In this regard, chemical compositional analysis was
carried out in order to determine the cellulose, lignin, holocellulose, ash and silica contents.
Furthermore, cold, and hot water solubility, 1% NaOH solubility and the ethanol-toluene extractive
contents were measured. The chemical composition analysis of Ethiopian sugarcane bagasse
revealed a good level of cellulose (50%) and Klason lignin content (18%). The measurement of
the bagasse fiber dimensions (fiber length of 1.86 mm, fiber diameter of 30.02 µm, cell-wall
thickness of 2.53 µm) advocates its suitability for pulp and paper production. The physical
fractionation pretreatment had a significant effect on reducing the lignin, ethanol-toluene
extractive, ash, and silica contents in the Ethiopian sugarcane bagasse, as evidenced from the
Fourier Transform Infrared Spectroscopy analysis.
Based on the above results, the physical fractionation pretreated Ethiopian sugarcane bagasse
(ESCB-B) was further delignified by using soda and Kraft pulping methods followed by a single
stage hydrogen peroxide bleaching. Multilevel categoric experimental design was used to assess
the effects of three independent process variables (pulping temperature, chemical concentration, and time) on the pulp yield and kappa number during the soda and Kraft pulping processes.
Response surface methodology with central composite experimental design was used to assess the
effect of independent bleaching variables (bleaching temperature, H2O2 concentration and time)
on the pulp yield, brightness, and whiteness during the bleaching process. For the optimal pulping
outputs, the pulp yield was 35.99% with 16.73 kappa number and 38.41% with 17.68 kappa
number for soda and Kraft delignification, respectively. The bleaching response for soda pulp with
kappa number of 16.73 and 8.27 were pulp yield of 88.07% and 85.17%, brightness of 62.02%
and 71.86% and whiteness of 84.43% and 90.47%, respectively. The bleaching response for Kraft
pulp with kappa number of 17.68 and 8.41 were pulp yield of 84.12% and 83.91%, brightness of
61.92% and 68.35% and whiteness of 85.36% and 91.43%, respectively. Paper from soda pulp
with kappa number of 16.73 and Kraft pulp with kappa number of 17.68 had higher burst, tensile
and tear strength than paper from soda pulp with kappa number of 8.27 and Kraft pulp with kappa
number of 8.41. Results suggest that the utilization of Ethiopian sugarcane bagasse using soda and
Kraft delignification at the optimum conditions of 130
o
C cooking temperature, 10% sodium
hydroxide concentration at 60 min followed by single stage hydrogen peroxide bleaching is a
promising approach.
Furthermore, the black liquors generated from the untreated and physical fractionation pretreated
Ethiopian sugarcane bagasse by using soda and Kraft delignification processes were characterized.
The lignin, chemical oxygen demand, biochemical oxygen demand and total dissolved solid
contents of pretreated sugarcane bagasse soda and Kraft black liquor were found to be (28.45 g/L,
50000 mg/mL, 328 mg/mL, 145.83 mg/L) and (23.29 g/L, 74100 mg/mL, 192 mg/mL, 157.49
g/L), respectively. On the other hand, the lignin, chemical oxygen demand, biochemical oxygen
demand and total dissolved solid contents of untreated sugarcane bagasse soda and Kraft black liquor were (40.53 g/L, 54300 mg/mL, 356 mg/mL, 157.88 g/L) and (36.51 g/mL, 77400 mg/mL,
200 mg/mL, 164.86 g/L), respectively. The untreated sugarcane bagasse soda and Kraft black
liquor present higher contents of lignin, chemical oxygen demand, biochemical oxygen demand
and total dissolved solid than pretreated soda and Kraft black liquor. The physical fractionation
pretreatment had a significant effect on reducing the lignin, chemical oxygen demand, biochemical
oxygen demand and total dissolved solid contents of the black liquor. The results clearly
demonstrate the efficacy of physical fractionation pretreatment for Ethiopian sugarcane bagasse
for pulp and paper production.
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Keywords
Sugarcane bagasse, physical fractionation pretreatment, soda delignification, Kraft delignification, single stage hydrogen peroxide bleaching, paper mechanical properties, black liquor