Hydrolysis of Poplar for Cellulosic Ethanol Production

A preliminary process design has been conducted for a facility for biochemical conversion of poplar hardwood to hexose (C6) and pentose (C5) sugars via enzymatic hydrolysis. This facility is in contrast to conventional plants, which use corn stover as the primary feedstock. The three primary process sections are (1) dilute-acid pretreatment, (2) saccharification, and (3) ethanol precipitation and sugar separation. The design was based on existing pilot plants including Zeachem and National Renewable Energy Laboratory (NREL) facilities. The dilute-acid pretreatment section utilizes sulfuric acid as a catalyst to break down the woodchips entering the system. This acid is then neutralized with lime and the solution is sent to the saccharification section. This section uses magnetic nanoparticle immobilized cellulase enzymes to break down the complex sugars into the desired hexose and pentose sugars. Once the enzymes are collected and the extra solids are removed and recycled, ethanol precipitates out the pentose sugars. A scaled economic analysis including feed, product, and capital costs, with a twenty-year cash flow, indicates a profitable process.