Optimization of Parameters and Production of Bioethanol From Raw Coffee Wet Processing Waste

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Addis Ababa University


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. iv 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.



Processing Waste