| Autohydrolysis, a simple and environmental friendly process, has long been studied but often abandoned as a financially viable pretreatment for bioethanol production due to the low yields of fermentable sugars at economic enzyme dosages. The introduction of mechanical refining can generate substantial improvements for autohydrolysis process, making it an attractive pretreatment technology for bioethanol commercialization.;In this study, several lignocellulosic biomass including wheat straw, switchgrass, corn stover, waste wheat straw have been subjected to autohydrolysis pretreatment followed by mechanical refining to evaluate the total sugar recovery at affordable enzyme dosages. Encouraging results have been found that using autohydrolysis plus refining strategy, the total sugar recovery of most feedstock can be as high as 76% at 4 FPU/g enzymes dosages. The mechanical refining contributed to the improvement of enzymatic sugar yield by as much as 30%.;Three non-woody biomass (sugarcane bagasse, wheat straw, and switchgrass) and three woody biomass (maple, sweet gum, and nitens) have been subjected to autohydrolysis pretreatment to acquire a fundamental understanding of biomass characteristics that affect the autohydrolysis and the following enzymatic hydrolysis. It is of interest to note that the nonwoody biomass went through substantial delignification during autohydrolysis compared to woody biomass due to a significant amount of p-coumaric acid and ferulic acid. It has been found that hardwood which has a higher S/V ratio in the lignin structure tends to have a higher total sugar recovery from autohydrolysis pretreatment.;The economics of bioethanol production from autohydrolysis of different feedstocks have been investigated. Regardless of different feedstocks, in the conventional design, producing bioethanol and co-producing steam and power, the minimum ethanol revenues (MER) required to generate a 12% internal rate of return (IRR) are high enough to discourage investors due to the high capital investment relative to low US ethanol price. Nevertheless, the economics of autohydrolysis can be substantially improved by upgrading the value of unhydrolyzed residues, such as the fuel pellets. Moreover, the utilization of proven technology and equipment renders autohydrolysis adaptable to pulp and paper industrial. Attractive economics have been found when autohydrolysis based bioethanol plant is co-located to a pulp and paper mill or the distressed pulp and paper mill is being repurposed to produce bioethanol.;An alternative to autohydrolysis combined with refining, thermomechanical pulping (TMP) process has been evaluated using corn stover as the feedstock. A significant low solids yield after the pretreatment process has been observed due to the harsh condition operated and the limitation of lab equipment. But the TMP process has great potential to be employed as a pretreatment for bioethanol production in an industrial scale if the process is optimized. |
