The production of biofuels from non-edible plant biomass has been necessitated by the concern for the environmental consequences of fossil fuel use and the tightening of supply and demand for liquid fuels. In contrast to first generation biofuels which rely on crops used for food supplies, second generation biofuels, derived from lignin-containing feedstocks, completely eliminate the competition for food. The major challenges associated with second generation biofuels are both technical and economic. Due to the recalcitrant nature of the raw biomass materials to further biological conversion, their structural degradation often requires severe and costly pretreatment processes such as heat, physical and chemical treatments to disturb and fractionate the biomass. Significant research effort has been devoted to understanding the recalcitrant nature and to accelerate the commercialization process of second generation biofuels. In this thesis, three pretreatment methods that belong to different categories have been investigated to understand their impacts on cellulose and/or lignocellulose and the subsequent hydrolysis steps. Physicochemical pretreatments, such as steam explosion, have been identified as one of the most effective and cost-efficient pretreatment methods for lignocelluosic materials. In Chapter 2, SO2-catalyzed steam explosion will be discussed and the effect of pretreatment severity on the substrate characteristics and degradation efficiency is also elucidated. Although the crystallinity index (CrI) of cellulose decreases as the severity increases, significant non-specific degradation and low yield of cellulose was observed at high severity. A new method for cellulose CrI determination has been developed with least squares curve fitting and validated with mechanically mixed cellulose samples. Biological pretreatment is another pathway through which the biomass structure can be modified to obtain a more amenable state for enzymatic degradation. Cellulose-binding domain (CBD) originated from Trichoderma reesei Cel7A (i.e. Tr cellobiohydrolase I) has been discovered as a potential biological pretreatment agent which is capable of modifying cellulose crystal structure. An extensive study on the protein engineering, expression, purification and functionalities of Cel7A CBDs was carried out (Chapter 3). The target mutations were identified with a computational protein engineering method involving principal component analysis (PCA). Due to the lack of catalytic activity and high throughput screening method, the library size was limited to nine. The wild-type and mutated CBDs were compared for their adsorption behavior and decrystallization effect on cellulose. Resulting saccharification efficiency after CBD pretreatment were studied and a possible explanation for the rate enhancement was proposed. In addition to physicochemical and biological pretreatment methods, chemical pretreatment is also a commonly employed method to overcome the recalcitrance of lignocellulosic materials. The most widely studied include dilute acid, alkaline, and organosolv processes. Inspired by the rapidly growing green solvent ionic liquid (IL) researches in biomass pretreatment, substituted imidazoles have been investigated in this thesis to assess their potential as pretreatment agents for lignocelluloses (Chapter 4). 1-Methylimidazole (MI), a precursor to some ILs, has been determined to be the most promising agent for lignocellulose pretreatment due to its exceptional delignification and cellulose expansion efficiency. The chemical recovery and MI process development will also be discussed in Chapter 4. In order to understand pretreatment effect, a semi-quantitative assay utilizing low molecular weight direct dyes and cellulases to estimate the accessibility and pore size distribution has been developed for application on pure cellulose substrates in Chapter 5. Finally, main conclusions as well as future perspectives for this work will be discussed in Chapter 6.

No description available.

Biomass conversion technologies are receiving increasing attention due to global climate change and most recently plans from the President of the United States to reduce fossil fuel consumption. The MixAlco process converts a variety of feedstocks, such as agricultural residues, municipal solid waste, and sewage sludge, into mixed alcohols via microbial fermentation, which can then be used as fuel additives or independently as an alternative fuel. Optimizing the pretreatment step of this process is critical to improving product yields. The process uses lime pretreatment, which can be enhanced using new decrystallization pretreatment methods, namely hydrodynamic cavitation and shock tube pretreatment.Previous studies on biomass decrystallization showed an increase in biomass digestibility when hydrodynamic cavitation was utilized as a pretreatment step. This previous work was expanded by studying both acoustic and hydrodynamic cavitation. Computational fluid dynamics (CFD) was used to model the cavitator to improve its efficiency. The crystallinity before and after pretreatment was analyzed. A new laboratory-scale MixAlco lime-pretreatment system was developed to produce greater quantities of lime-pretreated biomass that could be subjected to decrystallization experiments. The length of pretreatment, water loading, and bagasse loadings were varied for the shock tube experiments. After each pretreatment, enzymatic hydrolysis was performed, and the equivalent glucose yield was measured by the DNS (dinitrosalicylic acid) assay. Additionally, mixed-acid fermentation was performed to show the benefits of reduced crystallinity on the MixAlco fermentation. The acoustic and hydrodynamic cavitation pretreatments had a modest effect on crystallinity. In contrast, the shock tube pretreatment shows greater promise as an effective decrystallization pretreatment, even for lime-treated bagasse. Repeated shocks had little effect on digestibility and the crystallinity; however, the water temperature used in shock tube pretreatment played an important role in bagasse digestibility and crystallinity.

The research represents a first approach to measure the utilization potential of ultrasonic pretreatment on six different substrates: fat, oil and grease (FOG), paper sludge, ground switch grass, ground hay, ground wheat straw, and cut wheat straw. Several laboratories techniques were applied to determine the influence of ultrasonication on biogas production and yield, biogas quality, and digestibility ratio. With the data, mathematical definitions of Net Energy Balance and Net Economy Balance were computed to draw a first justification or rejection of the use of this pretreatment technology for the specific substrates. Ultrasonic pretreatment has a significant effect on biogas production and yield as well as digestibility ratio (p-value < 0.0001) from the early stages of digestion until as far as 50 days of digestion. Ultrasonication and macro particle size management did not influence significantly the methane (CH4) content in the biogas (p-value = 0.1793). Also, the impact of ultrasonication on the substrate varies between all studied feedstock. Most of the ultrasonicated digestion cases studied provided a negative Net Energy and Economic Balance except for FOG where a certain window of utilization was found. In the context of an ultrasonication process retrofit upgrade, the technology looks to be more useful for substrates that are hard to digest when the retention time is, unfortunately, longer than common retention time. In the context of a new facility, a design that includes an understood ultrasonication technology has yet a small potential success depending on several variables. The ultrasonication technology for anaerobic digestion is hard to recommend due to its energy consumption that, in many cases, overshadows the energy surplus derived from its use. / MITACS

With recent emphasis on development of alternatives to fossil fuels, sincere attempts are being made on finding suitable lignocellulosic feedstocks for biochemical conversion to fuels and chemicals. Sweet Sorghum is among the most widely adaptable cereal grasses, with high drought resistance, and ability to grow on low quality soils with low inputs. It is a C4 crop with high photosynthetic efficiency and biomass yield. Since sweet sorghum has many desirable traits, it has been considered as an attractive feedstock. Large scale sweet sorghum juice extraction results in excessive amounts of waste sweet sorghum bagasse (SSB), which is a promising low cost lignocellusic feed stock. The ability of two pretreatment methods namely conventional oven and microwave oven pretreatment for disrupting lignocellulosic structures of sweet sorghum bagasse with lime [Ca(OH)2] and sodium hydroxide [NaOH] was evaluated. The primary goal of this study was to determine optimal alkali pretreatment conditions to obtain higher biomass conversion (TRS yield) while achieving higher lignin reduction for biofuel production. The prime objective was achieved using central composite design (CCD) and optimization of biomass conversion and lignin removal simultaneously for each alkali separately by response surface method (RSM). Quadratic models were used to define the conditions that separately and simultaneously maximize the response variables. The SSB used in this study was composed of cellulose, hemicellulose, and lignin in the percentage of 36.9 + 1.6, 17.8 + 0.6, and 19.5 + 1.1, respectively. The optimal conditions for lime pretreatment in the conventional oven at 100 °C was 1.7 (% w/v) lime concentration (=0.0024 molL-1), 6.0% (w/v) SSB loading, 2.4 hr pretreatment time with predicted yields of 85.6% total biomass conversion and 35.5% lignin reduction. For NaOH pretreatment, 2% (w/v) alkali (=0.005 molL-1), 6.8% SSB loading and 2.3 hr duration was the optimal level with predicted biomass conversion and lignin reduction of 92.9% and 50.0%, respectively. More intensive pretreatment conditions removed higher amount of hemicelluloses and cellulose. Microwave based pretreatments were carried out in a CEM laboratory microwave oven (MARS 6-Xpress Microwave Reactions System, CEM Corporation, Matthews, NC) and with varying alkali concentration(0.3 - 3.7 % w/v) at varying temperatures (106.4 - 173.6 °C), and length of time (6.6 - 23.4 min). The NaOH pretreatment was optimized at 1.8 (% w/v) NaOH, 143 °C, 14 min time with predicted yields of 85.8% total biomass conversion and 78.7% lignin reduction. For lime pretreatment, 3.1% (w/v) lime, 138 °C and 17.5 min duration was the optimal level with predicted biomass conversion and lignin reduction of 79.9% and 61.1%, respectively. Results from this study were further supported by FTIR spectral interpretation and SEM images.

Increasing demand for fresh water in arid and semi-arid areas, similar to the Middle East, pushed for the use of seawater desalination techniques to augment freshwater. Seawater Reverse Osmosis (SWRO) is one of the techniques that have been commonly used due to its cost effectiveness. Recently, the use of Ultrafiltration (UF) was recommended as an effective pretreatment for SWRO membranes, as opposed to conventional methods (i.e. sand filtration). During UF operation, intermittent cleaning is required to remove particles and contaminants from the membrane's surface and pores. The different cleaning steps consume chemicals and portion of the product water, resulting in a decrease in the overall effectiveness of the process and hence an increase in the production cost. This research focused on increasing the plant's efficiency through optimizing the cleaning protocol without jeopardizing the effectiveness of the cleaning process. For that purpose, the design of experiment (DOE) focused on testing different combinations of these cleaning steps while all other parameters (such as filtration flux or backwash flux) remained constant. The only chemical used was NaOCI during the end of each experiment to restore the trans-membrane pressure (TMP) to its original state. Two trains of Dow™ Ultrafiltration SFP-2880 were run in parallel for this study. The first train (named UF1) was kept at the manufacturer's recommended cleaning steps and frequencies, while the second train (named UF2) was varied according to the DOE. The normalized final TMP was compared to the normalized initial TMP to measure the fouling rate of the membrane at the end of each experiment. The research was supported by laboratory analysis to investigate the cause of the error in the data by analyzing water samples collected at different locations. Visual inspection on the results from the control unit showed that the data cannot be reproduced with the current feed water quality. Statistical analysis using SAS JMP® was performed on the data obtained from UF2 determined that the error in the data was too significant, accounting for 42%. Laboratory inspection on water samples concluded that the water quality feeding to the UF membranes was worse than that of the raw water. This led to a conclusion that severe contamination occurred within the main feed tank where the water was retained before arriving to the UF modules. The type of contamination present in the feed tank is yet to be investigated. Though, frequent cleaning or flushing of the feed tank is recommended on regular basis.

No description available.

The depletion of fossil fuel reserves and global warming are the two main factors contributing to the current demand in clean and renewable energy resources. Biofuels are renewable energy resources and have an advantage over other renewable resources due to biofuels having a zero carbon footprint and most feedstock is abundant. The use of biofuels brought about major concerns and these include food, water and land security. The use of lignocellulose as bioethanol feedstock can provide a solution to the food, water and security concerns. Biofuels such as bioethanol can be produced from lignocellulose by breaking down the structure of lignocellulose liberating fermentable sugars. Amaranth lignocellulose has a potential to be used as a feedstock for bioethanol production because amaranth plants has a high yield of biomass per hectare, require very little to no irrigation and have the ability to withstand harsh environmental conditions. The aim of this study was to investigate the viability of amaranth as a feedstock for bioethanol production by using alkaline assisted microwave pretreatment. Alkaline pretreatment of amaranth using Ca(OH)2, NaOH and KOH at various concentrations (10-50 g kg-1 of alkaline solution in water) was carried out at different energy input (6-54 kJ/g). The pretreated broth was enzymatically hydrolysed using Celluclast 1.5L, Novozyme 188 and Tween 80 at pH 4.8 and 50oC for 48 hours. The hydrolysate was further fermented to ethanol using Saccharomyces cerevisiae at a pH of 4.8 and 30oC for 48 hours. The effect of microwave pretreatment on amaranth lignocellulose was evaluated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The monomeric sugars and ethanol were quantified using high performance liquid chromatography (HPLC). A maximum sugar yield of 0.36 g/g of biomass was obtained for pretreatment with 30 g kg-1 Ca(OH)2 solution in water, 0.24 g/g of biomass was obtained for pretreatment with 50 g kg-1 NaOH solution in water and 0.21g/g of biomass was obtained for pretreatment with 50 g kg-1 KOH solution in water at 32 kJ/g of energy input. After enzymatic hydrolysis the yields increased to 0.43 g/g, 0.63 g/g and 0.52 g g-1 of biomass for Ca(OH)2 , KOH and NaOH pretreated biomass respectively. The highest ethanol yield obtained was found to be 0.18 g/g of biomass from fermentation of KOH pretreated broth. The ethanol yield obtained from fermentation of Ca(OH)2 and NaOH pretreated broth was 0.13 g/g of biomass and 0.15 g/g of biomass respectively. The results showed that an increase in concentration of alkaline solution and an increase in energy input liberate more sugars. A decrease in biomass loading was found to increase the total sugar yield. Pretreatment with KOH was found to liberate more pentose sugars than the other alkaline solutions. The morphological changes shown by the SEM images showed that microwave irradiation is effective in breaking the structure of amaranth lignocellulose. The structural changes shown by the FTIR also validated that alkaline bases were effective in breaking the lignin, cellulose and hemicellulose linkages and liberating more sugars in the process. This work has demonstrated the enormous potential that amaranth lignocellulose has on being a feedstock for bioethanol production. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

The depletion of fossil fuel reserves and global warming are the two main factors contributing to the current demand in clean and renewable energy resources. Biofuels are renewable energy resources and have an advantage over other renewable resources due to biofuels having a zero carbon footprint and most feedstock is abundant. The use of biofuels brought about major concerns and these include food, water and land security. The use of lignocellulose as bioethanol feedstock can provide a solution to the food, water and security concerns. Biofuels such as bioethanol can be produced from lignocellulose by breaking down the structure of lignocellulose liberating fermentable sugars. Amaranth lignocellulose has a potential to be used as a feedstock for bioethanol production because amaranth plants has a high yield of biomass per hectare, require very little to no irrigation and have the ability to withstand harsh environmental conditions. The aim of this study was to investigate the viability of amaranth as a feedstock for bioethanol production by using alkaline assisted microwave pretreatment. Alkaline pretreatment of amaranth using Ca(OH)2, NaOH and KOH at various concentrations (10-50 g kg-1 of alkaline solution in water) was carried out at different energy input (6-54 kJ/g). The pretreated broth was enzymatically hydrolysed using Celluclast 1.5L, Novozyme 188 and Tween 80 at pH 4.8 and 50oC for 48 hours. The hydrolysate was further fermented to ethanol using Saccharomyces cerevisiae at a pH of 4.8 and 30oC for 48 hours. The effect of microwave pretreatment on amaranth lignocellulose was evaluated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The monomeric sugars and ethanol were quantified using high performance liquid chromatography (HPLC). A maximum sugar yield of 0.36 g/g of biomass was obtained for pretreatment with 30 g kg-1 Ca(OH)2 solution in water, 0.24 g/g of biomass was obtained for pretreatment with 50 g kg-1 NaOH solution in water and 0.21g/g of biomass was obtained for pretreatment with 50 g kg-1 KOH solution in water at 32 kJ/g of energy input. After enzymatic hydrolysis the yields increased to 0.43 g/g, 0.63 g/g and 0.52 g g-1 of biomass for Ca(OH)2 , KOH and NaOH pretreated biomass respectively. The highest ethanol yield obtained was found to be 0.18 g/g of biomass from fermentation of KOH pretreated broth. The ethanol yield obtained from fermentation of Ca(OH)2 and NaOH pretreated broth was 0.13 g/g of biomass and 0.15 g/g of biomass respectively. The results showed that an increase in concentration of alkaline solution and an increase in energy input liberate more sugars. A decrease in biomass loading was found to increase the total sugar yield. Pretreatment with KOH was found to liberate more pentose sugars than the other alkaline solutions. The morphological changes shown by the SEM images showed that microwave irradiation is effective in breaking the structure of amaranth lignocellulose. The structural changes shown by the FTIR also validated that alkaline bases were effective in breaking the lignin, cellulose and hemicellulose linkages and liberating more sugars in the process. This work has demonstrated the enormous potential that amaranth lignocellulose has on being a feedstock for bioethanol production. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Donghai Wang / Cellulosic ethanol is a renewable source of energy. Lignocellulosic biomass is a complex material composed mainly of cellulose, hemicellulose, and lignin. Biomass pretreatment is a required step to make sugar polymers liable to hydrolysis. Mineral acids are commonly used for biomass pretreatment. Using acid catalysts that can be recovered and reused could make the process economically more attractive. The overall goal of this dissertation is the development of a recyclable nanocatalyst for the hydrolysis of biomass sugars. Cobalt iron oxide nanoparticles (CoFe[superscript]2O[subscript]4) were synthesized to provide a magnetic core that could be separated from reaction using a magnetic field and modified to carry acid functional groups. X-ray diffraction (XRD) confirmed the crystal structure was that of cobalt spinel ferrite. CoFe[superscript]2O[superscript]4 were covered with silica which served as linker for the acid functions. Silica-coated nanoparticles were functionalized with three different acid functions: perfluoropropyl-sulfonic acid, carboxylic acid, and propyl-sulfonic acid. Transmission electron microscope (TEM) images were analyzed to obtain particle size distributions of the nanoparticles. Total carbon, nitrogen, and sulfur were quantified using an elemental analyzer. Fourier transform infra-red spectra confirmed the presence of sulfonic and carboxylic acid functions and ion-exchange titrations accounted for the total amount of catalytic acid sites per nanoparticle mass. These nanoparticles were evaluated for their performance to hydrolyze the β-1,4 glycosidic bond of the cellobiose molecule. Propyl-sulfonic (PS) and perfluoropropyl-sulfonic (PFS) acid functionalized nanoparticles catalyzed the hydrolysis of cellobiose significantly better than the control. PS and PFS were also evaluated for their capacity to solubilize wheat straw hemicelluloses and performed better than the control. Although PFS nanoparticles were stronger acid catalysts, the acid functions leached out of the nanoparticle during the catalytic reactions. PS nanoparticles were further evaluated for the pretreatment of corn stover in order to increase digestibility of the biomass. The pretreatment was carried out at three different catalyst load and temperature levels. At 180°C, the total glucose yield was linearly correlated to the catalyst load. A maximum glucose yield of 90% and 58% of the hemicellulose sugars were obtained at this temperature.