Utilization of Agricultural Food Waste Products for Bioethanol Generation, Kiambu County, Kenya
Osei, Janet Appiah
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Increase in food supply has led to the generation of high quantities of wastes from agricultural products. Globally, 40-50% of food wastes arise from fruits, cereals and vegetables. Wastes from agricultural food products are easily degraded and difficult to separate from the whole quantity of wastes. There are also difficulties in handling and storage because of their high water and rich organic compositions. The study employed rare incubation techniques which are not yet utilized by researchers to produce bioethanol. The main objective was to utilize agricultural food wastes to generate bioethanol. The specific objectives were: i) To determine the amount of bioethanol that can be generated from different types of selected agricultural waste products (cereals, vegetables, fruits) under different incubation conditions and durations. ii) To optimise different incubation techniques at different temperatures for bioethanol production from selected agricultural food waste products. iii)To optimise different fermentation durations for bioethanol production from the selected agricultural food waste products. Food wastes were collected and subjected to physical pre-treatment and then enzymatic hydrolysis by the use of commercial enzyme cellulase from Aspergillus niger and finally anaerobic fermentation to convert the produced sugars into ethanol. The different incubation techniques used for fermentation took place in an incubator set at 30oC, in the dark room at temperature 21oC and under the soil at temperature 19oC with different fermentation durations of 48 hours, 96 hours and 144 hours. All collected data were entered in excel before being subjected to analysis of variance using Genstat statistical package (Discovery version 4) at 5% level of probability (P<0.05). Ethanol productivity, concentration and yield were the three parameters used to determine the amount of bioethanol produced from each wastes. The highest bioethanol yield of 240.6 ml/kg was recorded from cereal wastes followed by fruits (156.0 ml/kg) and vegetables (63.5 ml/kg). There was decrease in bioethanol concentration and yield with increasing fermentation time in fruits and vegetables but for the cereals, there were gradual increases. In all the substrates used, there were decreases in bioethanol productivity with time. There were slight decreases in bioethanol concentration and yield from 19oC to 21oC and sharp increase from 21oC to 30oC in cereal substrates. In vegetable substrate, there were slight increases in bioethanol concentration and yield from 19oC to 21oC but sharp decrease at temperature 30oC whilst in fruit substrates, there were slight decreases from 19oC to 21oC but sharp decrease at temperature 30oC. Results showed that the optimum temperatures for cereals, fruits and vegetables were 30oC, 19oC and 21oC respectively. The findings of this work suggest that agricultural food waste products are rich in fermentable sugars and can be used effectively for bioethanol production. This will be beneficial to the Ministry of Environment in Kenya in solving waste management issues confronting the nation. Also the use of incubators for fermentation especially in vegetable and fruit substrates can be replaced with dark room and under soil which are more economically feasible.