Energy Analysis of Bioethanol Production from Cow Manure

Abstract

This research focuses on energy consumption in eight defined unit operations (mixing, sieving, alkaline treatment, drying, milling, hydrolysis, fermentation, distillation) of bioethanol production from cow manure. Data for energy analysis were obtained through direct measurements from a developed bioethanol plant for the production of ethanol from cow manure.  The energy analysis was evaluated with 10, 15 and 20 kg of cow manure using ASTM standards. Standard energy equations were used to analyse Energy Input, Energy Output, Energy Efficiency, Energy Productivity, Net Energy and Net Energy Value (NEV). The computation of energy use was done using Microsoft Excel. The results show that the Energy Input (269.37, 336.12, 402.65 MJ/kg); Energy Output (94.40, 147.50, 236.00, MJ/kg); Energy Efficiency (35.04, 43.88, 58.61%); Energy Productivity (0.0148, 0.0186, 0.0248 MJ/kg)); Net Energy (-174.97, -188.62, -166.65 MJ/kg) and Net Energy Value (0.25, 0.16, 0.10) were obtained for 10, 15 and 20 kg of cow manure, respectively. These samples indicated that energy was not efficiently used. Sieving, drying, hydrolysis and distillation were the major energy intensive operations, accounting for over 96% of total energy consumption in the bioethanol production. Thermal energy was mostly used in the bioethanol production stages, represented over 94% of total energy consumption. The NEV of less than 1.0 implied that ethanol production from the cow manure was not viable from energy perspectives.