Economic Evaluation of Butanol Production and Cost Comparisons

In this study, a cost estimation was performed for butanol production from corn, cellulosic biomass, and food waste. From these feedstocks, sugar was produced and the prices were compared as $/kg sugar. At a current corn price of $208/metric ton, sugar was produced and its price was calculated to be $0.33/kg. Cellulosic biomass and food waste were found to be economic. Cellulosic biomass was obtained at $35/metric ton ($0.035/kg) and from this feedstock sugar was produced at a price of $0.25/kg. The price of food waste was $15/metric ton ($0.015/kg) and at this price, sugar was generated at a price of $0.09/kg. Since these two substrates (biomass and food waste) were most economical, they were used to perform cost estimations of butanol production. Butanol plant capacity was 100 × 10 6 kg/year. Co-products such as acetone, ethanol, lignin, and gases were also produced. The amounts of acetone and ethanol were 50 × 10 6 kg/year and 16.67 × 10 6 kg/year, respectively. These solvents plus other co-products were sold for credit. The selling price of butanol from biomass was estimated at $1.14/kg, while from food waste it was projected to be $0.11/kg. The reasons for such a low butanol production cost from food waste were low substrate cost and the requirement for no hydrolytic enzymes or nutrients such as corn steep liquor (CSL). In this report, the advantages and disadvantages of several product recovery processes were considered and pervaporation was pointed out to be cost-effective. The use of molasses and whey permeate as substrates was also considered; however, their high prices were prohibitive. The application of high productivity reactors was also considered.