Process Development and Fundamental Study on Enzymatic Hydrolysis of Cellulosic Biomass to Fermentable Sugars for Ethanol Production

Waste paper materials such as office paper, newspaper and paper sludge present unique advantages for bioethanol production. They are abundant, low lost and require less intensive pretreatment to open up the lignocellulosic structure for enzymatic hydrolysis. The objective of this research is to develop conversion processes that are technically and economically feasible for producing ethanol from waste paper materials. Identifying and understanding the inhibition factors in lignocellulosic biomass and enzymes that influence enzymatic hydrolysis of fermentable sugars are also covered. A fundamental study of the effects of pretreatment and lignin removal on softwood was also conducted because softwood is a major wood resource in many parts of the world and a major source of paper materials.;Different types of waste paper materials were studied in this research in terms of their feasibility for fermentable sugar production via enzymatic hydrolysis. In Chapter 2, low enzyme dose on recovered office paper was investigated. Ash removal was identified to be necessary since both acid soluble and acid insoluble ash adsorbed enzyme during enzymatic hydrolysis. This ash-enzyme interaction was proven to have higher affinity than cellulose-enzyme interaction. The effect of hornification - irreversible pore collapse in lignocellulosic fibers was also studied. Mechanical refining by a PFI mill of previously dried fibers improved sugar recovery to similar or higher levels as never dried fibers.;Paper sludge is another attractive biomass source for the conversion to ethanol. A mechanical fractionation process was proposed in Chapter 3 in order to remove ash from sludge prior to enzymatic hydrolysis. This process removed 82-98% of the ash with fiber yields from 39-69%. Fractionation efficiency was also evaluated by testing different size mesh screen openings, aiming to optimize this fractionation process. The ash rich streams had a lower C:N ratio than the original sludge, which improved its suitability as soil amendment.;In Chapter 4, process simulation using engineering process simulation software WinGEMS and financial analysis on the feasibility of the process developed in Chapter 3 were conducted. The financial impact of the addition of the sludge fractionation step was discussed based on using sludge from virgin and recycled paper mills. The most profitable case was fractionated virgin sludge (from a virgin paper mill) to ethanol (F-VK1) with a net present value (NPV) of US;Newspaper contains high lignin content among various waste paper materials. Chapter 5 is focused on developing a pretreatment process ideal for newspaper saccharification. The effects of non-ionic surfactant and flexo link were also studied. Tween 80 improved sugar conversion of newspaper and flexo ink was proven to have no inhibition effects on enzymatic hydrolysis. Pretreatment including autohydrolysis, mechanical refining, oxygen, alkaline and green liquor (GL) pretreatments were evaluated on newspaper. Except mechanical refining and oxygen pretreatment, all the other pretreatment methods adversely affected enzymatic hydrolysis of newspaper. It was presumably due to the pore collapse in the fibers during the pretreatment process.;Softwoods are the dominant lignocellulosic feedstocks in the Northern hemisphere and viewed to be attractive and sustainable for ethanol fuel production. However, lignocellulosic biomass, especially softwood, is recalcitrant to biological degradation due to its rigid and compact structure, as well as its chemical compositions. In Chapter 6, a fundamental study on the effect of lignin removal by different pretreatments was performed. Lignin by oxidative treatment yielded higher enzymatic hydrolysis efficiency than kraft pulping and this was especially significant with sodium chlorite pretreatment. Factors affecting softwood saccharification were investigated by generating softwood fibers with the same bulk lignin content (11.3%-13.7%) by kraft pulping, sodium chlorite, oxygen and high consistency ozone delignification. Lignin hydrophobicity was identified as one of the most important factors influencing enzymatic hydrolysis of softwood.