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2017 | 14 | 36-46
Article title

Chemical composition and diluted acid hydrolysis pretreatment of Acacia mellifera sawdust as a raw material for bioethanol production

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Biofuels are alternatives to fossil fuels for ensuring energy security and for mitigating climate change. Currently, most biofuels are in the form of a bioethanol that is generated from starch or sugar. Increasing energy demand, food insecurity and ecological concerns leads to evaluating agricultural, forestry and urban lignocellulosic wastes as being very important for energy production. This is because all celluloses and hemicelluloses of lignocellulosic wastes can be converted into bioethanol reducing sugars. Hence, the current study was initiated to determine the chemical composition and best diluted acid hydrolysis pretreatment of Acacia mellifera sawdust for bioethanol production. Our study indicates that the chemical composition of Acacia mellifera sawdust exhibits different composition in extractives such as alcohol, cellulose, lignin and ash. Accordingly, the extractive content of the sawdust was 6.3% soluble alcohol toluene, 52.9% cellulose, 23.9% lignin, 4.2% ash, and 6.92% moisture content, respectively. In our experiment, the biomass at a solid loading rate of 0.66% was pretreated at 121 °C with different sulfuric acid concentrations (0.5, 0.75, and 1 %, w/w) and residence times (10, and 20 min). Total reducing sugars in the hydrolyzed sample with acid and time were then analyzed. The reducing sugars obtained at 0.50%, 0.75% and 1% dilute sulfuric acid concentration with time residence of 10 min and 20 min were, 7.39±0.24 and 8.4±0.9, 8.03±0.64 and 9.18±0.43, 9.68±1.30 and 10.23±0.80, respectively. With the increasing acid concentration and residence time, the amount of glucose in the filtrates increased. Therefore, the total reducing sugar concentration in the hydrolysate of Acacia mellifera saw dust was significantly influenced by the sulfuric acid concentration and residence time. From this study, it can be concluded that total reducing sugars in lignocellulosic wastes are widely available and easily obtainable, they can be considered as potential feedstocks for bioethanol production.
Physical description
  • Bioenergy and Biochemical Research Division, Ethiopia Environment and Forest Research Institution, P.O. Box 2322, Addis Ababa, Ethiopia
  • Bioenergy and Biochemical Research Division, Ethiopia Environment and Forest Research Institution, P.O. Box 2322, Addis Ababa, Ethiopia
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