Elephant grass (pennisetumi purpureum) as a potential raw material for pulp and paper manufacture in Ghana

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
Considering the growing demand for paper making raw materials, coupled with uncertainties in the prediction of the global supply and demand for plant fibre resources as well as the diminishing resources and rising wood prices, the growing interest in alternative raw material resources such as annual plants and grasses for the pulp and paper industry is becoming important in recent times. Indigenous samples of Ghana-grown elephant grass (Fennisetum purpureum) of ages 2, 4, 6 and 12 months were micropulped using 14, 15 and 16% soda and 1% anthraquinone on oven dry mass at total pulping times of 50, 100, 120, 140 and 160 minutes to obtain an optimum pulping schedule. An optimum pulping schedule of 15% soda, 1% anthraquinone and total pulping times of 120 minutes for the 2, 4 and 6 months old individual grasses and their composite mixtures (2/4, 2/6,4/6 etc.) as well as 140 minutes for the 12 months old grass and its composite mixtures (12/6, 12/4, 12/2 etc.) were obtained and used for the macro or laboratory scale pulping. The unscreened pulp yield, alkali consumption and percentage solid contents of the black liqour of the micropulped samples were 35 - 48%; 1.00 - 91.27%; 7.34— 9.00% and those of the macropulped were in the range of 51 - 57; 98.60 - 99.60% and 7.7 - 10.10% respectively. The reject formation of the macropulping was between 0.30 and 5%. Unbleachable pulp grade samples of Kappa number 8.5 to 23.3 which gave an Elrepho brightness level range of 30.7 to 35.9%. The Ghana-grown Elephant grass showed potential physical strengths properties of 5.70 - 8.85mNm2/g (for tear index), 1.0 - 4.0KPam2/g (burst index); 4.6 - 13. 9km (breaking length), 25 - 202.2J/m2 (tensile energy absorption) and 3.1- 7.5 geometric means [(breaking length x burst index)1/2 x tear index ]1/2= geometric means] respectively. The chemical composition of the whole stem was 39 - 47%, 19 - 27% and 4 - 6% for cellulose, lignin and alcohol-benzene extract content respectively. The outer part of the elephant grass which comprised well over 85% of the mass and volume of the grass, had a fibre length, fibre diameter, cell wall thickness and lumen diameter of 1.66 - 1.76mm, 14.5 - 18.9.tm, 2.5 - 2.7iim and 9.5 - 13.5im respectively. The Runkel, Flexibility and Slenderness ratios as well as the Fibre Density of the outer part of the elephant grass were 0.4 - 0.53, 0.65 - 0.71, 92 - 120.6 and 0.29 - 0.35 respectively. Generally the 2- months old Elephant grass exhibited the greatest potential with respect to pulp yield and quality hence the optimum cutting cycles for the Ghana - grown Elephant grass is recommended to be 2 months
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of Master of Science Degree in Wood Technology and Management, 2000