Abstract

A simple process for on-farm bioethanol production from cassava, using cassava kojisupplemented with crude liquid enzyme and yeast was described. On a small scale, a fed-batch mode where 4 kg of koji, 2 kg of gelatinized cassava flour and 30 g of yeast cells were mixed and allowed to ferment for 2 days, followed by addition of 1.5 kg of cassava flour and fermenting for another 3 days, gave higher ethanol concentration of 7.05% (0.34 g-ethanol/g-cassava flour) than when 3.5 kg of gelatinized cassava flour, 4 kg of koji and 30 g of yeast cells were mixed at the same time and allowed to ferment for 5 days. The process was scaled up 100 times and economic feasibility was evaluated. The total investment cost was seven million, five hundred thousand Nigerian naira (₦) (US$46,875). With a payback period of five years, the cost of cassava tubers represented 71.73% of the total production cost. At a market price of fresh cassava tubers of ₦10,000/ton, the ethanol production cost was ₦102.5/l (US$0.641/l), which is not profitable considering the current market price of ethanol (US$0.597~0.748/l). The process becomes profitable only when the price of fresh cassava tuber is reduced to ₦5,000/ton (US$31.25/ton). At this price, the ethanol production cost would be ₦58.53/l (US$0.366/l). The process is recommended for vertically integrated system (on-farm process) where the cassava produced in the farm is used, thereby shielding it from high and fluctuating market prices of cassava.

Key words: Fuel ethanol, bioenergy, koji, economic analysis, cassava ethanol.