Utilization of waterhyacinth (Eichhornia crassipes) biomass for production of ethanol
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Date
1999
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University of Dar es Salaam
Abstract
Conversion of Waterhyacinth (Eichhornia crassipes) biomass to fermentable sugars using acid-catalyzed hydrolysis has been studied. Waterhyacinth (WH) biomass was obtained from Lake Victoria, Tanzania. The research was aimed at studying the availability of fermentable sugars in WH biomass, establishing the optimal conditions for both acid hydrolysis and fermentation of the WH hydrolysates. Among the parameters investigated include; acid concentration, hydrolysis temperature, hydrolysis time, particle size and liquid-to-solid ratios. The effect of these parameters on sugar yield and composition of the hydrolysates have been reported. The types and amounts of sugars in Waterhyacinth (WH) samples were determined by using the High Performance Liquid Chromatography (HPLC) method. Waterhyacinth (WH) hydrolysates were found to contain glucose and xylose as the sole types of monomeric (or reducing} sugars. A yield of 18.5% w/w fermentable sugar (based on dry weight of WH biomass) was achieved during hydrolysis of oven-dried Waterhyacinth (ODWH) biomass at 220°C. The observed suitable conditions were: acid concentration, 1.5% by weight H2SO4; temperature, 220°C; liquid-to-solid ratio (m1/g), 30:1; particle size, < lmm and hydrolysis time, 10-25 min. The hydrolysates obtained at these conditions were rich in six-carbon (C6-) sugars, which could be fermented to ethanol. About 23.2% w/w sugar yield was obtained at 70°C and 60.0% H2SO4 acid. However, the hydrolysates were rich in five-carbon (CS-) sugars, which could not be converted to ethanol. It was therefore, concluded that Waterhyacinth hydrolysates obtained from high-temperature dilute-acid hydrolysis process are very appropriate medium for productive alcoholic fermentation. Gas Chromatography (GC) analysis has shown that ethanol yield (in g/g glucose used) of about 0.48 could be achieved at the following conditions: hydrolysate sugar concentration, 100g/L; initial pH, 5.5 and temperature of 30°C when baker’s yeast is used. The overall ethanol yield from the biomass was 111 litres per tonne of dry WH biomass. This is equivalent to TSh. 499,500/= which is an added value to the plant. A two-stage hydrolysis process has been proposed. This involves pre-hydrolysis in which the hemicellulose sugars are hydrolyzed under mild conditions followed by hydrolysis at high temperatures using dilute acid. Since this process involve high temperature dilute-acid hydrolysis, fresh Waterhyacinth biomass could be used and thus avoid the cost of drying the biomass. Further studies are recommended, particularly, in designing a prototype followed by optimization studies to reduce the reaction time and minimize acid usage. Furthermore, the findings of this research should be integrated with other control strategies of Waterhyacinth in Lake Victoria for sustainable solution.
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Keywords
Water hyacinth, Tanzania
Citation
Masende, Z. P. G. (1999) Utilization of waterhyacinth (Eichhornia crassipes) biomass for production of ethanol, Masters’ dissertation, University of Dar es Salaam. Available at (http://41.86.178.3/internetserver3.1.2/detail.aspx)