Optimization of Parameters and Production of Bioethanol From Raw Coffee Wet Processing Waste
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Date
2015-06
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Addis Ababa University
Abstract
A large amount of coffee waste water is generated from coffee processing plants. These
residues possess serious environmental problems following the direct discharge in to the
nearby water bodies and cause serious environmental and health problems. This study
aimed to: (i) review wet coffee processing waste management practice in Ethiopia, (ii)
characterize wet coffee processing waste and determine its total reducing sugar potential,
(iii) quantify wet coffee processing waste and estimate its bio-ethanol potential and also
evaluate the feasibility of bio-ethanol production and (iv) optimize the parameters and
produce bio ethanol from wet coffee processing waste. The review of wet coffee
processing waste management practice in Ethiopia revealed that there are about 1026
operational wet coffee processing industries and many more industries are under
construction. In 2012, the estimated amount of wet coffee processing waste from
operational industries in Ethiopia was about 291,600 tones / year. The study also
examined the characteristics of wet coffee waste. The volatile solid of the Pulp juice and
Mucilage were determined and showed that the wastes have high organic component, i.e.
Pulp juice, 66.5% and Mucilage, 90.2%. The study shows the waste (pulp juice and
mucilage) is acidic with pH 4.75 and 3.67, respectively. Pulp juice and Mucilage had
very high BOD and COD Concentration, i.e. BOD = 25,600 mg/L and COD = 45,000
mg/L for pulp juice and BOD = 19,810 mg/L, COD = 33,600 mg/L for Mucilage. The
COD: BOD ratio is less than 2:1, which shows the wastes are bio-degradable. This study
shows that the coffee wastes are potential environmental problems and cause water
pollution due to high organic component and acidic nature. The waste was hydrolyzed by
dilute H2SO4 (1, 2, 3 and 4%) and distilled water. Total sugar content of the sample was
determined titrimetrically and using refractometer.
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Maximum total sugar content (90%) was obtained from hydrolysis by 3% H2SO4. The
results obtained at hydrolysis of 4, 2, 1% H2SO4 and distilled water are 72.86, 76.50,
63.75 and 56.66%, respectively. Ethanol production was monitored by gas
chromatography. The maximum ethanol yield of 78% was obtained from coffee waste
hydrolyzed by 0.4 M H2SO4 for 1 hour hydrolysis, temperature of 100 0C and
fermentation for 24 hours and initial pH of 4.5. Based on the data, it was concluded that
coffee may be considered as one of the most valuable primary products in world trade,
crucial to the economies and politics of many developing countries. As a consequence of
big market, the reuse of the main coffee industry wastes is of significant importance from
environmental and economical view points. In conclusion, this study has proposed to
utilize the wet coffee processing waste to produce bio-ethanol which provides the
alternative energy source from waste biomass and solves the environmental waste
disposal as well as human health problem.
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Keywords
Processing Waste