2017 Volume 71 Issue 8 Pages 915-926
Since June 2009, we have been operating a pilot plant to evaluate a process for producing bio-ethanol from lignocellulosic biomass, wherein lignin is removed using soda-anthraquinone（ soda-AQ） cooking as a pretreatment for enzymatic saccharification. By the end of September 2012, we completed all pilot plant operations and obtained the following results. Using a semi-batch cooking method, Sugi （Cryptomeria japonica） soda-AQ pulp was produced at an yield of 44%. The Sugi pulp was hydrolyzed using a commercial cellulase to obtain a sugar yield of 97%. The produced sugar solution was concentrated from 3.1% to 7.4% using a reverse osmosis membrane and then fermented using a yeast to obtain an ethanol yield of 96.5%. The volume of ethanol produced was then calculated to be 216 L from 1 BDT of Sugi chips.
Based on these operational data, we estimated the energy balance and manufacturing costs at a chip consumption rate of 250 t/day. In the entire process from pretreatment to ethanol distillation, the steam and electric energy consumption was 824.6 eT/day and 118.7 MWh/day, respectively. However, the energy generated was calculated to be 1,102.2 eT/day of steam and 189.8 MWh/day of electricity from the discharged black liquor, which exceeds the energy consumed. From these calculations of operating costs, we estimated the variable and total costs associated with producing 1 L of ethanol to be 98 yen and 263 yen, respectively. These estimations suggest that the cost of Sugi chips and depreciation expense would be substantially reduced to use this process.
