Production and Optimization Of Bioethanol From Agroindustrial Waste-Brewer’s Spent Grain
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Date
2018-06
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Journal ISSN
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Publisher
AAU
Abstract
This work basically focuses on the production and optimization of bioethanol from brewer`s
spent grain-lignocellulose, which is a by-product from breweries. The proximate analysis for
brewer`s spent grain was conducted and found that BSG contains: moisture content of 12.08%,
extractives and ash 2-4%, cellulose 34.62%, hemicellulose 18.84%, lignin 11.23% and the
balance protein and fiber, high composition of cellulose which was used to produce fermentable
sugar. Hydrolysis was conducted in two stages. First stage hydrolysis was conducted at moderate
process conditions: temperature of 130
Addis Ababa University Institute of Technology School of Chemical and Bio Engineering process
stream page ii
0
C, retention time of 20min, and acid concentration of 1%
and liquid to solid ratio of 10v/w; a second stage hydrolysis was conducted at extreme conditions
of process parameters due to the high crystallinity of cellulose. The process parameters:
temperature, time, and acid concentration were held at 140-150
0
C, 20-30min, and 2-3%,
respectively by holding liquid to solid ratio of 10v/w and particle size of 2mm-1mm constant.
Two levels randomized with one block full factorial design with three replicate for three factors
was conducted and total number of runs were 2
3
*3=24+6=30 with 6 center points. By using
analysis of variance the statistical data were generated and results that show the effect of process
parameters on the yield of total reduced sugars produced during hydrolysis process were
analyzed and found a maximum yield of 57.8% at a temperature, time and acid conc. of 150
C,
20min and 3%, respectively. After collecting reduced sugars from the hydrolysis stages,
fermentation was conducted at a temperature range of (30, 32, 34, 36 and 38)
0
C and pH of 4.5, 5,
5.5, 4.8 and 5.2, by holding concentration of substrate to yeast strain 10 v/v and fermentation
time of 72hr constant. Power law assumption was considered for fermentation and the optimum
fermentation temperature and pH were identified as 32
0
C and 5, respectively. Thermodynamic
and kinetic analysis was conducted for the fermentation step and 2.4
and 16.133KJ of
frequency factor and activation energy were found, respectively. Water-ethanol mixture and
other heavy compounds were separated in the distillation column and recovered ethanol was
characterized
Description
Keywords
brewer`s spent grain, bioethanol, kinetics, cellulose, hydrolysis