Development of biological conversion of lignocellulosic biomass to biogas is one approach to utilize straw comprehensively. However, high lignin contents of lignocellulosic materials results in low degradation. The main aim of this study was to investigate the appropriate pre-treatment to increase biogas production from Chinese agricultural residues. In this study, Chinese corn stalk, rice plant and wheat straw were evaluated as substrates by applying three different pre-treatments. The investigated pre-treatment were mechanical pre-treatment (cut whole straw into 1-1.5cm) combination of thermal and alkali pre-treatment (1M/L NAOH, 80℃,15 hours) and biological pre-treatment(enzymes provided by Scandinavian Biogas Fuels AB). Biogas production of these substrates was evaluated by batch digester; Sewage sludge from Nykvarn treatment plant and current digesters (Scandinavian Biogas Fuels AB )was the co-digestive substrate which seeded in batch with straw of all pre-treatments. The results indicate that at least 50% of organic contents in Chinese agricultural residues could be converted to biogas by these pre-treatments. The optimizing biogas yield is achieved from Chinese corn stalk with combination of thermal and alkali pre-treatment, Chinese rice plant and wheat straw from pre-hydrolysis pre-treatment respectively .Chinese wheat straw has the most biogas potential from combination of thermal and alkali pre-treatment.

Technologies for pretreatment of waste activated sludges (WAS) prior to digestion are of increasing interest to wastewater treatment utilities because of their promise for improving sludge digestibility and reducing the mass of biosolids remaining after digestion. While there has been considerable study of pretreatment processes, a common approach to describing the impact of pretreatments on sludge biodegradability has not been developed. The overall objective of this study was to develop protocols that can be employed to characterize the impact of pretreatment processes on WAS digestion. Sonication and ozonation were employed as models of physical and chemical pretreatment technologies respectively. A range of physical, chemical and biological responses were evaluated to assess the impact of pretreatment on WAS properties as well as digestibility. WAS samples that were generated over a range of solids residence times (SRTs) under controlled operating conditions were employed to facilitate an assessment of the interaction between pretreatment and WAS properties on digestibility. The VS, COD and soluble TKN responses indicated that a significant fraction of the WAS solids were solublized by sonication and ozonation, however, it appeared that the types of materials which were solublized was affected by the SRT at which the WAS was generated and the level of pretreatment. The results indicated that the impact of pretreatment on biodegradability of WAS was not described by solublization values exclusively without considering the SRT of the sludge and the level and type of pretreatment. A higher level of proteinaceous materials was preferentially solublized as the result of pretreatment. Respirometry revealed that both sonication and ozonation substantially reduced the viable heterotrophs in the sludge and modestly increased the readily biodegradable fraction of COD. The ultimate yields of CH4 and NH4 in BMP tests and VFAs in BAP tests revealed that pretreatment marginally increased the ultimate digestibility of the sludges. Only a high dose of ozonation substantially increased the digestibility of the 15 day SRT sludge. However, both sonication and ozonation substantially increased the rate of hydrolysis which is typically the rate limiting process in WAS digestion. The BMP test was not a useful test to evaluate the rate of methane generation due to inhibition of methanogens in the early days of BMP test for pretreated sludges. The comparison between VFA and ammonia responses in day 10 of BAP test and ultimate values of these responses after 60 days in BMP test revealed linear relationships between these responses. According to these relationships, a set of models were introduced in this study. The models can be employed to predict the ultimate methane and ammonia generation using soluble COD, VFA or ammonia responses in day 10 of BAP tests. The BAP test was determined to be a shorter test (10 days) than the BMP (55 to 60 days) test and could provide information on the rates of hydrolysis and acidification/ammonification processes. Characterization of biodegradable and non-biodegradable material in WAS samples was conducted using a simplified ADM1 model. The characterization also revealed that proteins are a substantial fraction of biodegradable materials. The estimated ammonia, VFA and methane values from the stoichiometric model were similar to the corresponding values from the experiments. This supported the validity of the simplified model for all sludges employed in this study.

At present, the United States generates biofuels (ethanol) from corn grain. Unfortunately, low crop yields and limited growth regions result in limited availability. Furthermore, the use of staple food crops for ethanol production has generated a highly controversial food vs. fuel debate. Because of its high abundance and relatively low cost, lignocellulosic biomass is a promising alternative feedstock for biofuel production; however, structural features of lignocellulose limit accessibility of enzymes or microorganisms. These structural barriers include high lignin content, acetyl groups on hemicellulose, high cellulose crystallinity, cellulose degree of polymerization, and small pore volume. To overcome these barriers, a variety of pretreatment processes (chemical and mechanical) have been developed. Oxidative-lime pretreatment (OLP) is highly effective at reducing lignin content and removing acetyl groups from hemicellulose. Combining OLP with a mechanical treatment process greatly enhances the enzymatic digestibility of lignocellulose. Recommended OLP conditions were determined for Dacotah (120 °C, 6.89-bar O2, 240 min) and Alamo (110 °C, 6-89-bar O2, 240 min) switchgrass. Using recommended conditions, 72-h glucan digestibilities (g glucan hydrolyzed/100 g glucan in raw biomass; 15 filter paper units/g raw glucan) of 85.2 and 88.5 were achieved for Dacotah and Alamo, respectively. Adding ball milling to OLP further enhanced glucan digestibility to 91.1 (Dacotah) and 90.0 (Alamo). In previous studies, shock treatment achieved promising results, but was often inconsistent. This work refined shock treatment with a focus on using consistent procedures and performance analysis. The combination of OLP and shock treatment enhanced the 72-h glucan digestibility of several promising biomass feedstocks: bagasse (74.0), corn stover (92.0), poplar wood (94.0), sorghum (71.8), and switchgrass (89.0). Highly digestible lignocellulose can also be used as ruminant animal feed. Shock treatment plus OLP increased the total digestible nutrients (TDNN; g nutrients digested/100 g organic matter) of corn stover from 51.9 (untreated) to 72.6. Adding in pre-washed corn stover solubles to produce a combined feed (17.8 percent corn stover solubles and 82.2 percent shock OLP corn stover) increased TDNN to 74.9. Mixing in enough solubilized protein to match the crude protein content of corn grain further improved TDNN to 75.5, only 12.6 less than corn grain.

Energy utilization is a determining factor for the standards of living around the world, and the current primary source of energy is fossil fuels. A potential source of liquid fuels that could ease the strain caused by diminishing petroleum resources is bioethanol. Effective exploitation of biomass materials requires a pretreatment to disrupt the lignin and cellulose matrix. The pretreatment utilized for this research was oxygen delignification, which is a standard process stage in the production of bleached chemical pulp. The model substrate utilized as a feedstock for bioethanol was recovered fibre. An analysis of the substrates digestibility resulted in a hexose yield of approximately 23%, which justified the need for an effective pretreatment. An experimental design was performed to optimize the delignification conditions by performing experiments over a range of temperature, caustic loadings, and reaction times. Equations were developed that outline the dependence of various response parameters on the experimental variables. An empirical model that can predict sugar concentrations from enzymatic hydrolysis based on the Kappa number, enzyme loading, and initial fibre concentration was also developed. A study of hydrolysis feeding regimes for untreated recovered fibre (87 Kappa), pretreated recovered fibre (17 Kappa), and bleached pulp (6 Kappa) showed that the batch feeding regime offers reduced complexity and high sugar yields for lower Kappa substrates. In order to evaluate the possibility of lignin recovery, the pH of delignification liquor was reduced by the addition of CO₂ and H₂SO₄, resulting in up to 25% lignin yield. An experiment that looked at effect of post-delignification fibre washing on downstream hydrolysis found that a washing efficiency of approximately 90% is required in order to achieve a hexose sugar yield of 85%.

The City of Winnipeg, MB currently hauls by truck the leachate from the landfill, to be co-treated with the municipal wastewater at a wastewater treatment plant. Pre-treating the leachate with physico-chemical methods would allow for direct discharge to the sewer system, avoiding transportation. The goal of this research is to evaluate the effectiveness of different pre-treatment options as well as their impact on a biological nutrient removal system. In Phase I, the four pre-treatment options evaluated were air stripping, chemical coagulation, electro-coagulation and advanced oxidation with sodium ferrate. Chemical coagulation and air stripping reported the best COD and ammonia removal rates, respectively. Phase II evaluated the effectiveness of the selected pre-treatment methods in the response of a biological treatment system. The pre-treatment was successful in allowing complete nitrification by lowering the influent ammonia concentration. However, if the ratio of leachate to wastewater is low enough; pre-treatment may not be needed as the dilution lowers the impact of the leachate’s higher concentrations.

Canola meal (Brassica napus L.) and oriental mustard bran (Brassica juncea) were subjected to alkali and acid pretreatment to expose pentosan, for enhancing further enzymatic hydrolysis by endo-1,4-β-xylanase from Trichoderma longibrachiatum for the production of oligosaccharides. Pretreatment especially with alkali, effectively increased the relative content of pentosan to about ~ 41% and ~ 72%. Alkali pretreated canola meal and mustard bran resulted in a pentose content of 2.28 ± 0.15 g and 3.20 ± 0.11 g per 100 g substrates at 18 h and 24 h of reaction respectively, which corresponded to ~ 26% and ~ 28% conversion of original pentosan in substrates. UPLC-MS data showed xyloglucuronic acid (XGlcA) as the major oligosaccharide in the hydrolyzates. Reversed-phase HPLC-DAD indicated the principal phenolic compound in the hydrolyzates was sinapine. DPPH radical scavenging assay showed that endoxylananse hydrolyzates of acid pretreated substrates had strong antioxidant activities in comparison to alkali pretreated samples.

Pseudo-lignin, which can be broadly defined as aromatic material that yields a positive acid-insoluble (Klason) lignin value, has been reported to generate from biomass polysaccharides during dilute acid pretreatment (DAP). To investigate the fundamental chemistry of pseudo-lignin, a series of state-to-art analytical techniques including GPC, FT-IR and ¹³C NMR were applied to characterize pseudo-lignin extracted from poplar α-cellulose and holocellulose after DAP. The results showed that pseudo-lignin is polymeric (Mn ~ 1000 g/mol; Mw ~ 5000 g/mol) and consists of carbonyl, carboxylic, aromatic, methoxy and aliphatic structures, which can be produced from both dilute acid-treated cellulose and hemicellulose. During DAP, the hydrolysis of polysaccharides, which leads to some release of monosaccharides, and their subsequent dehydration reactions to form furfural and 5-hydromethylfurfural (HMF) takes place. Further rearrangements of furfural and/or HMF can produce aromatic compounds, which undergo further polymerization and/or polycondensation reactions to form pseudo-lignin. More importantly, pseudo-lignin was revealed to bind with cellulase enzymes unproductively and significantly retard enzymatic conversion of cellulose. As compared to native lignin after DAP, the inhibition effect arise from pseudo-lignin is much stronger, which clearly indicates pseudo-lignin formation should be avoided during DAP. Process optimization study indicated that addition of dimethyl sulfoxide (DMSO) to the DAP reaction medium can effectively increase sugar recovery and reduce pseudo-lignin formation, even under high-severity pretreatment conditions. The pseudo-lignin suppression property of DMSO has been attributed to the preferential arrangement of DMSO in the vicinity of the C1 carbon of the HMF molecule, thereby protecting HMF from further reactions to form pseudo-lignin.

No description available.

The rapid accumulation of municipal solid waste is a significant environmental concern in our rapidly growing world. Due to its low cost, high energy recovery and limited environmental impact anaerobic digestion (AD) is a promising solution for stabilizing the organic fraction of municipal solid waste (OFMSW). Hydrolysis is often the rate-limiting step during AD of wastes with high solid content; this step can be accelerated by pretreatment of waste prior to AD. This thesis presents the results of alkaline pretreatment of OFMSW using NaOH and KOH. Four different pH levels 10, 11, 12 and 13 at two temperatures 23±1°C and 80±1°C were examined to study the effects of the pretreatment on (i) enhancing the solubility of the organic fraction of the waste, and (ii) enhancing the AD process and the biogas production. The effects on solubility were investigated by measuring changes in the soluble COD (SCOD) concentrations of pretreated wastes and the enhanced AD was investigated by measuring volatile solids (VS) destruction, total COD (TCOD) and SCOD removal in addition to biogas and methane production using biochemical methane potential (BMP) assay and semi-continuous laboratory reactor experiments. Pretreatment at pH 13 at 80±1°C demonstrated the maximum solubility for both NaOH and KOH pretreated samples; however the BMP analysis demonstrated that pretreatment at pH 12 at 23±1°C showed the greatest biogas yield relative to the removed VS for both chemicals. Thus pretreatment at pH 12 at 23±1°C using NaOH and KOH were examined using semi-continuous reactors at three different HRTs: 10, 15 and 20 days. Pretreatment demonstrated a significant improvement in the AD performance at SRTs of 10 and 15 days.

Energy utilization is a determining factor for the standards of living around the world, and the current primary source of energy is fossil fuels. A potential source of liquid fuels that could ease the strain caused by diminishing petroleum resources is bioethanol. Effective exploitation of biomass materials requires a pretreatment to disrupt the lignin and cellulose matrix. The pretreatment utilized for this research was oxygen delignification, which is a standard process stage in the production of bleached chemical pulp. The model substrate utilized as a feedstock for bioethanol was recovered fibre. An analysis of the substrates digestibility resulted in a hexose yield of approximately 23%, which justified the need for an effective pretreatment. An experimental design was performed to optimize the delignification conditions by performing experiments over a range of temperature, caustic loadings, and reaction times. Equations were developed that outline the dependence of various response parameters on the experimental variables. An empirical model that can predict sugar concentrations from enzymatic hydrolysis based on the Kappa number, enzyme loading, and initial fibre concentration was also developed. A study of hydrolysis feeding regimes for untreated recovered fibre (87 Kappa), pretreated recovered fibre (17 Kappa), and bleached pulp (6 Kappa) showed that the batch feeding regime offers reduced complexity and high sugar yields for lower Kappa substrates. In order to evaluate the possibility of lignin recovery, the pH of delignification liquor was reduced by the addition of CO₂ and H₂SO₄, resulting in up to 25% lignin yield. An experiment that looked at effect of post-delignification fibre washing on downstream hydrolysis found that a washing efficiency of approximately 90% is required in order to achieve a hexose sugar yield of 85%.