Journal of Cleaner Production (09596526)339
The production of high concentrations of ethanol from N-methylmorpholine N-oxide- (NMMO) and phosphoric acid-pretreated rice straw was investigated at high solid loadings (solid-state) using filamentous fungus Mucor indicus. The impacts of most influential factors on ethanol production by simultaneous saccharification and fermentation (SSF), i.e., enzyme loadings (2.5, 5, 10, and 20 FPU/g substrate), solids loadings (15, 20, and 30% w/w), and SSF time (72 and 120 h), were assessed. The highest glucose concentrations were 106.5 and 94.1 g/L gained from 72-h hydrolysis of the straw pretreated with NMMO and phosphoric acid at 15% (w/w) solids loadings, respectively. The highest ethanol concentrations were 63.4 and 69.0 g/L, achieved by 30% solids loading from 72-h SSF of the straw pretreated with NMMO and phosphoric acid at 20 and 10 FPU celluloses per g substrate, respectively. A prolonged SSF process at enzyme loadings less than 5 FPU/g straw could not improve ethanol concentration from NMMO-pretreated straw, while ethanol concentrations above 40 g/L (61.0 and 59.9 g/L) were achieved through 120-h fermentation of the straw pretreated with phosphoric acid at 30% solid loading. The highest ethanol yields were 73.7 and 100% of the theoretical yield gained from the straw pretreated with phosphoric acid and NMMO, respectively, at the lowest solids loading (15%) and the highest enzyme loading (20 FPU/g substrate). © 2022
Spruce is the most resistant type of lignocellulosic material to anaerobic digestion. Different parts of spruce tree, i.e., leaves, wood, branches, bark, fruit, and mixtures of these parts, were pretreated using the leading pretreatments, i.e., concentrated phosphoric acid, dilute sulfuric acid, and ethanolic organosolv pretreatment, to improve biogas production. The pretreatment effects on methane yield from both solid and liquid fractions of the pretreatments were evaluated. Different parts of the tree showed different behaviors. The maximum methane yields from the pretreated solids were obtained after phosphoric acid pretreatment, which yielded methane yields of 211.7 and 225.5 mL per g volatile solids (VS) of pretreated spruce leaves and mixture, respectively. The improvements were related to opened-up structure, crystallinity reduction, and delignification. Sulfuric acid pretreatment improved biomethane yield from liquids, but not solids. Moreover, organosolv pretreatment improved the yield from solids, but not wood, bark, and the mixture. The maximum methane production yield was 245.3 NmL CH4/gVS which was obtained from the organosolv liquor of spruce leaves. The highest overall methane production (252.9 L per Kg) was gained from the whole solid and liquid fractions from organosolv pretreatment of leaves. This methane yield corresponded to 2.4-fold improvement compared to that of the untreated leaves (107 NmL CH4/gVS). Thus, leaves and branches are less recalcitrant parts and do not need severe pretreatment, while bark and wood are the most recalcitrant parts and required severe pretreatment like concentrated phosphoric acid. Moreover, the mixture of all parts also required severe pretreatment for efficient biogas production. © 2022 Elsevier Ltd
Biological pretreatments and their combination with chemical and physical pretreatments are among the inexpensive methods for the improvement of biogas production from lignocellulosic biomass. In this study, mesophilic aerobic digestion was studied as a biological pretreatment to improve biogas production from pinewood. Its effects in combination with other pretreatments, i.e., liquid hot water (LHW), sodium hydroxide (NaOH), and ultrasonic pretreatments, were also investigated. LHW and Alkali (using 8% w/w NaOH) pretreatments were performed at less severe conditions (100 °C for 10 min) to evaluate the synergistic effect of these thermochemical pretreatments on biogas production. The ultrasonic pretreatment was performed at 40 KHz for 30 min at 40 °C. Biological pretreatment was carried out using aerobic sludge at 37 °C for 10 days. The aerobic digestion was the only pretreatment that could individually improve the methane yield from pinewood by 7.3 folds. However, the highest methane yield (57.7 mL/g VS of pretreated pinewood) was obtained by the combination of NaOH, biological, and ultrasonic pretreatments, which was 11.2 folds higher than that of the untreated substrate. It was concluded that the pretreatment with aerobic digestion could significantly improve the biogas production yield, especially in combination with mild thermo-chemical pretreatments. © 2021 Elsevier Ltd
Process Safety and Environmental Protection (17443598)152pp. 513-526
Orange wastes, including peel and pulp, were used as a biorefinery feedstock to produce pectin, ethanol, and biogas. The orange wastes were subjected to dilute acid treatment with sulfuric acid (1% w/v) at 94, 100, 140, and 180 °C for 60, 30, and 0 min. The sulfuric acid treatment was performed for pectin extraction, sugars hydrolysis, and lignocellulose pretreatment. The pectin was extracted from the hydrolysate, the liquor was used to produce ethanol, and the pretreated solid was anaerobically digested to produce biogas. The highest pectin extraction yield was 24.7 % (w/w) from orange peel and 23.7 % (w/w) from pulp, which was obtained from the supernatants of treatment at 94 °C for 60 min. Fourier transfer infrared spectrometer results confirmed the similar characteristics of the extracted pectin to a commercial product. The galacturonic acid content (an indicator of pectin purity) of pectin extracted from orange peel was 70.2 % and from orange pulp was 69.9 %, at the optimum conditions. The pectin obtained from the acid treatment at 94 °C for 60 min had a degree of esterification higher than 69 %, whereas it was less than 45 % for that obtained after treatment at 140 °C for 30 min. The maximum ethanol yields of 81.5 % (from peel) and 82.9 % (from pulp) were achieved from the hydrolysate of the acid treatment at 140 °C for 30 min. The highest methane yields were 176.8 mL/g volatile solids (from the untreated peel) and 191.8 mL/g volatile solids (from the untreated pulp). Overall, the maximum total product value was 2,472.9 USD/t orange wastes, which was achieved from dilute acid treatment at 94 °C for 60 min. At the optimal conditions for high production of pectin, without any enzyme consumption, 244 kg of pectin, 26.5 L of ethanol, and 36 m3 of methane were produced from 1 t of orange wastes. © 2021 Institution of Chemical Engineers
Renewable Energy (09601481)170pp. 714-723
Sodium carbonate pretreatment, an environmentally-friendly and efficient pretreatment, was used to improve solid-state ethanol production from corn stover (CS). To further enhance ethanol yield from the pretreated CS, especially at low enzyme loadings, a combined pretreatment, including steam and sodium carbonate pretreatments, was developed. The removal/modification of lignin by sodium carbonate pretreatment (at 100 °C for 3 h) helped to obtain high ethanol titer at high solids and low enzymes loadings. The maximum ethanol concentration was about 44 g/L, obtained after 72 h simultaneous saccharification and fermentation (SSF) of CS pretreated with sodium carbonate without mixing and prehydrolysis at 30% solid and 15 FPU/g enzyme loadings. Applying prehydrolysis and increasing the SSF time to 120 h improved ethanol concentration to 59 and 67 g/L, respectively. Steam pretreatment at 190 °C for 10 min before sodium carbonate pretreatment led to 76% increase in ethanol concentration. At the enzyme loading of only 5 FPU/g substrate, the modified pretreatment increased the ethanol concentration from 24 g/L to 41 g/L, compared with that of sodium carbonate pretreatment. The results showed that hemicellulose removal and delignification by steam and sodium carbonate pretreatment, respectively, considerably improved ethanol concentration at high solids and low enzyme loadings. © 2021 Elsevier Ltd
Biomass Conversion and Biorefinery (21906815)11(5)pp. 1909-1920
Improved ethanol production from rice straw, as well as its environmental and socio-economic effects, was studied and compared with fossil fuels. Alkaline, i.e., sodium hydroxide (NaOH) and sodium carbonate (Na2CO3), pretreatments improved the ethanol yield at cold (0 °C), mild (25 °C), and hot (93 °C) pretreatment temperatures. Different substrate characteristics, including enzymatic saccharification, accessible surface area, chemical composition, buffering capacity, enzyme adsorption and desorption, and structural changes, were analyzed to determine the most influencing factors on ethanol yield. Both alkaline pretreatments led to the highest ethanol yields using the pretreatments at 93 °C followed by 0 °C. The maximum ethanol yield (85.1%) belonged to the sample pretreated with NaOH at 93 °C, corresponding to 150% increase compared with ethanol yield of the untreated straw (30.9%). Glucose yield from enzymatic hydrolysis and water swelling capacity were the only characteristics that showed similar trends to the obtained ethanol yield and also presented their optimum values, 84.1% and 5.5 g/g, respectively, at the conditions with the highest ethanol yield (NaOH, at 93 °C). Therefore, glucose yield and water swelling capacity were the factors with the closest correlation with ethanol yield. Environmental assessments estimated that the annual bioethanol production from untreated rice straw in Iran was 141 million L that could be increased up to 615 million L after pretreatment with NaOH at 93 °C. This amount can supply ethanol needs in Iran as E5 for 169 days in a year, which in turn reduces 888 kt of GHG emissions. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Mirmohamadsadeghi, S.,
Karimi, K.,
Azarbaijani, R.,
Parsa yeganeh, L.,
Angelidaki, I.,
Nizami, A.,
Bhat, R.,
Dashora, K.,
Vijay, V.K.,
Aghbashlo, M. Renewable and Sustainable Energy Reviews (13640321)135
As one of the most efficient methods for waste management and sustainable energy production, anaerobic digestion (AD) countenances difficulties in the hydrolysis of lignocelluloses biomass. Different pretreatment methods have been applied to make lignocelluloses readily biodegradable by microorganisms. These pretreatments can affect biogas yield by different mechanisms at molecular scale, including changes in chemical composition, cellulose crystallinity, degree of polymerization, enzyme adsorption/desorption, nutrient accessibility, deacetylation, and through the formation of inhibitors. The present article aims at critically reviewing the reported molecular mechanisms affecting biogas yield from lignocelluloses via different types of pretreatments. Then, a new hypothesis concerning the impact of pretreatment on the microbial community developed (throughout the AD process from an identical inoculum) was also put forth and was experimentally examined through a case study. Four different leading pretreatments, including sulfuric acid, sodium hydroxide, aqueous ammonia, and sodium carbonate, were performed on rice straw as model lignocellulosic feedstock. The results obtained revealed that the choice of pretreatment method also plays a pivotally positive or negative role on biogas yield obtained from lignocelluloses through alteration of the microbial community involved in the AD. Considerable changes were observed in the archaeal and bacterial communities developed in response to the pretreatment used. Sodium hydroxide, with the highest methane yield (338 mL/g volatile solid), led to a partial switch from acetoclastic to the hydrogenotrophic methane production pathway. The findings reported herein undermine the default hypothesis accepted by thousands of previously published papers, which is changes in substrate characteristics by pretreatments are the only mechanisms affecting biogas yield. Moreover, the results obtained could assist with the development of more efficient biogas production systems at industrial scale by offering more in-depth understanding of the interactions between microbial community structure, and process parameters and performance. © 2020 Elsevier Ltd
Tabatabaei, M.,
Aghbashlo, M.,
Valijanian, E.,
Kazemi shariat panahi, H.,
Nizami, A.,
Ghanavati, H.,
Sulaiman, A.,
Mirmohamadsadeghi, S.,
Karimi, K. Renewable Energy (09601481)146pp. 1204-1220
This study reviews the innovations and optimizations in biogas production from the biological perspective reported by recently published patents and research works. The proposed biological strategies can be categorized into three different groups, i.e., upstream, mainstream, and downstream approaches. In the first part of this review, upstream strategies, including pretreatments by fungal, microbial consortium, and enzymatic as well as some other biological methods including microaeration, composting, ensiling, and genetic and metabolic engineering are discussed in detail. The impacts of upstream strategies on biogas production as well as their potentials in further improving the biogas industry are comprehensively scrutinized. Despite their promising impacts on biogas production, such biological innovations are time-consuming and require extra equipment and facilities that should be addressed in future studies. Overall, most information on biogas production has been generated through lab-scale investigations and not by commercial plants, undermining the commercial value of these data for the right decision-making. Pilot data would be necessary for techno-economic analyses with acceptable accuracies. Therefore, the future efforts should be directed toward providing the missing data for re-engineering designs, calculations, and life cycle assessment (LCA) of the newly designed biogas plants. © 2019 Elsevier Ltd
Tabatabaei, M.,
Aghbashlo, M.,
Valijanian, E.,
Kazemi shariat panahi, H.,
Nizami, A.,
Ghanavati, H.,
Sulaiman, A.,
Mirmohamadsadeghi, S.,
Karimi, K. Renewable Energy (09601481)146pp. 1392-1407
This review is aimed at detailing and discussing biological innovations and optimizations including upstream, mainstream, and downstream approaches in biogas production elaborated in the recently published patents and research papers. In the first part of this review, upstream strategies including pretreatments by fungal, microbial consortium, and enzymatic as well as some other biological methods including microaeration, composting, ensiling, and genetic and metabolic engineering were comprehensively presented and duly discussed. Despite the fact that these approaches hold great promise for improving the quantity and quality of the evolved biogas, the need for more processing time and extra equipment are the main drawbacks of such strategies. In the second part of this review, mainstream and downstream strategies are reviewed, and their merits and limitations are outlined. Bioaugmentation, anaerobic co-digestion, and integrated biogas production are evaluated as mainstream strategies. Finally, downstream biological approaches used for removal of CO2, H2S, and other impurities are reviewed and discussed. Among the mainstream biological techniques, bioaugmentation is highly advised to accelerate start-up periods at commercial scale while anaerobic co-digestion is recommended to not only enhance biogas yield throughout the operation but also to take advantage of different waste streams. Such mainstream strategies could contribute to improving the economic facets of biogas plants. Despite their currently underdeveloped status, downstream techniques for biological removal of biogas impurities are expected to replace their physiochemical counterparts at industrial scale in future owing to increasingly stringent environmental regulations. © 2019 Elsevier Ltd
Renewable Energy (09601481)152pp. 399-408
The safflower plant as an attractive feedstock for development of a biorefinery through the multi-biofuel production was evaluated. The safflower plant, composed of straw (79.6 wt %) and oilseed (20.4 wt%), was used for bioethanol, biogas, and biodiesel production. The oil was extracted from the seeds and subjected to methanolic transesterification process to produce biodiesel. The remained seed cake was converted to biogas by anaerobic digestion process. The ethanol production from safflower straw was not satisfactory; thus, the straw was hydrothermally pretreated at 120–180 °C for 1–5 h to maximize the bioethanol production. The increase in the pretreatment time and temperature considerably improved the ethanol yield, and the highest yield of 60.3% was obtained performing the pretreatment at 180 °C for 5 h. The biodiesel and methane production yields from oilseeds and seed cake were 90.3% and 185.8 mL/g volatile solids, respectively. Overall, each kg of safflower plant yielded 97.2 g ethanol, 22.4 L methane, and 46.6 g biodiesel that are totally equivalent to 0.168 L gasoline per kg of safflower plant in this biorefinery concept. © 2020 Elsevier Ltd
Dry/solid-state fermentative ethanol production refers to ethanol production by solid-state fermentation (SSF), performed almost in the absence of free water, unlike submerged fermentation (SmF). This article discusses advantages and disadvantages of SSF process for bioethanol production. Furthermore, various factors that influence the SSF ethanol production, including type of microorganism, moisture content, microorganism concentration, particle size, temperature, mixing, and pH as well as their effects on the process were presented and discussed. Moreover, different bioreactor designs which can be used for ethanol production using SSF process are included. © 2020 Elsevier Inc. All rights reserved
Rice straw and husk are the major by-products of cultivation of rice, which is the second leading agricultural crop after corn. The open field burning of rice straw and husk is gradually being replaced by the recovery and utilization of these resources. For this purpose, silica recovery from rice residues is one of the main options. Different technologies are being developed for silica production from rice straw and husk. In this chapter, various techniques are categorized and reviewed within a platform to explain most existing methods. In addition, the most important characteristics of the recovered silica and their relation to the operational conditions as well as the applications of the produced silica are presented. © 2020 Elsevier B.V. All rights reserved.
Bioresource Technology Reports (2589014X)7
Food wastes have a high biomethane production potential because of their high organic matter contents. This review paper presents an overview on the fundamentals of anaerobic digestion (AD) of food wastes. The most important influential parameters on the biomethane production, including feedstock characteristics (nutrient contents, particle size, and inhibitory compounds) and process parameters (process configuration, pH, temperature, retention time, organic loading rate, agitation, hydrogen concentration, moisture content, and inoculum), are discussed in full. Moreover, recent developments aimed at improving the AD of food wastes are classified and discussed as operational parameters optimization, additives application, digestate recirculation, frequent feeding, and feedstock pretreatment. Finally, future challenges and prospects of biogas production from food wastes are presented. © 2019 Elsevier Ltd
Energy Conversion and Management (01968904)182pp. 520-529
High titer ethanol production from rice straw using Mucor indicus fungus was investigated through the solid-state simultaneous saccharification and fermentation (SSSF) process. The straw was pretreated with 0.5 M sodium carbonate solution for 3, 5, and 10 h to improve the efficiency of the process. Effects of the pretreatment on the composition, structural morphology, cellulose crystallinity, swelling capacity, and buffering capacity of the straw were studied. Moreover, the effects of SSSF reaction time, enzyme loading, and solid loading on glucose and ethanol production were investigated. Additionally, the nutritional value of the residue from the SSSF process, as an animal feedstock, was determined in terms of lipid and protein contents. The highest total sugar concentration was 89.2 g/L, obtained from the straw pretreated for 10 h after hydrolysis with 10 FPU/g straw at 15% (w/w) solid loading. Total sugars concentration was not significantly improved by increasing the pretreatment time at low enzyme loadings, whereas it was significantly improved at high enzyme loadings. The highest ethanol concentration and SSSF yield were 99.4 g/L and 89.5% (71.8% based on the raw material), achieved from the straw pretreated for 10 h through the 72-h SSSF at 30% and 15% solid loading, respectively, using 20 FPU/g straw. The low enzyme loadings of 2.5 and 5 FPU/g straw yielded ethanol with concentrations as high as 66.3 and 90.9 g/L, respectively, after 120-h fermentation at 30% solid loading from the straw pretreated for 5 h. © 2018 Elsevier Ltd
Energy (18736785)172pp. 545-554
Safflower straw, an abundant, inexpensive, and renewable lignocellulosic waste, was used as a substrate of anaerobic digestion to produce biogas. Hydrothermal pretreatment was carried out on the straw at 120, 150, and 180 °C for 1, 2, and 5 h to increase the biogas yield. The pretreatment resulted in a solid (mainly cellulose) and a liquid (mainly hemicellulosic monomers). The highest biomethane yield from solid fraction (191.4 NmL/g VS) was obtained at the least severe pretreatment conditions (120 °C for 1 h), which showed 98.3% improvement in comparison to the untreated straw. The maximum methane yield of 406.9 NmL/g VS was attained from the liquid fraction of pretreatment at 180 °C for 1 h. Overall, at the optimum pretreatment conditions (120 °C for 1 h), 148.4 m3 methane was produced from each ton of pretreated safflower straw, whereas the methane production from the untreated straw was 86.9 m3 methane. Furthermore, enzymatic hydrolysis was carried out on solid fractions. The results revealed that the most severe pretreatment conditions (180 °C for 5 h) led to the highest released sugar concentration of 25.1 g/L using the enzyme loading of 10 FPU/g substrate, while it was only 4.5 g/L for the untreated one. © 2019 Elsevier Ltd
Energy (18736785)167pp. 654-660
Ethanol at high concentration was produced from rice straw pretreated with sodium carbonate through dry simultaneous saccharification and fermentation (DSSF). A high concentration of ethanol was obtained without mechanical mixing, an increase in fermentation time, and pre-hydrolysis. The most important influencing factors, including pretreatment time (3–10 h), enzyme loading (5–40 FPU/g substrate), solid loading (15–30 wt %), and DSSF reaction time (48–120 h), were investigated on dry hydrolysis and DSSF. An increase in pretreatment time from 3 to 10 h improved ethanol concentration from 55.1 to 67.7 g/L, obtained through DSSF at 20% solid loading and 10 FPU/g substrate. A glucose concentration as high as 124.6 g/L was obtained from the hydrolysis of the straw treated for 5 h. The highest total sugar and ethanol concentration were 137.3 g/L and 83.1 g/L for the treated straw, while they were 65.2 g/L and 38.6 g/L for the untreated ones, respectively, obtained by hydrolysis and DSSF at 30% solid loading. Changes associated with pretreatment, i.e., composition, crystallinity, and microscopic structure of untreated and treated straws, were investigated to find the reason for the improved hydrolysis and DSSF. © 2018 Elsevier Ltd
Applied Microbiology And Biotechnology (14320614)102(7)pp. 3425-3438
Besides free sugars, sweet sorghum stalks contain cellulose and hemicellulose that can be used for biofuel production. The pretreatment of stalks without the extraction of free sugars is more complicated than typical lignocelluloses, because of the degradation of free sugars during most pretreatment processes. In this study, the bioconversion of sweet sorghum stalks into biogas and bioethanol was studied using an improved organosolv pretreatment within a biorefinery framework. The organosolv pretreatment was developed using an aqueous solution of ethanol (EtOH) and isopropanol (IPOH). The process was optimized to obtain a liquor containing free sugars with the least sugar degradations together with a highly degradable solid fraction. The liquor was subjected to anaerobic digestion for biomethane production, while the solid was used for ethanol production via simultaneous saccharification and fermentation (SSF). The most influencing pretreatment parameters, i.e., temperature, time, alcohol to water ratio, EtOH to IPOH ratio, and the presence or absence of sulfuric acid (as a catalyst), were adjusted to achieve the highest yields of bioconversion. The maximum methane and ethanol production yields of 271.2 mL CH4/g VS and 87.8% (equal to the gasoline equivalent of 0.170 and 0.241 L/kg, respectively) were achieved from the liquor and pretreated solid, respectively; however, they were obtained at different optimum conditions. Considering the biorefinery perspective, the highest gasoline equivalent of 0.249 L/kg was efficiently obtained from the whole process after pretreatment at 140 °C for 30 min using 60:20 EtOH/IPOH ratio in the presence of 1% sulfuric acid. Further analyses, including enzymatic adsorption/desorption, compositional analysis, FTIR, and SEM, were conducted to investigate the effects of this newly developed pretreatment on the substrate. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
BioResources (19302126)13(1)pp. 1872-1884
Rice straw burning is the most widely used industrial process for silica production, resulting in the loss of carbohydrate energy and environmental pollution. In this study, dry anaerobic digestion was applied to convert an organic fraction of rice straw into biogas while generating a solid digestate rich in silica. The methane yield obtained from the dry digestion was 119 L per kg of volatile solids of the straw. The silica content in the ash of the digested straw was 20.7% higher than that of the ash from raw rice straw. The X-ray diffraction pattern revealed the existence of amorphous silica in the ash of the digested straw. The Fourier transform infrared analysis dispelled concerns about the addition of silica impurities by the anaerobic digestion process. The transmission electron microscopy results revealed the formation of nanosilica with particle sizes between 15 nm and 30 nm. It was concluded that high-quality nanosilica can be obtained from anaerobically digested rice straw. The application of this process can decrease the annual global greenhouse gas emissions by 10.5 million tons.
Fuel (00162361)218pp. 41-48
Waste jeans, containing cotton and polyester, are among the widely available sources for bioenergy production. In this study, the cotton part of waste jean was used for biogas and ethanol production. The hydrolysis of non-cellulosic part, i.e., polyester, and the pretreatment of cellulosic part was performed by sodium carbonate treatment. The effects of Na2CO3 concentration (0, 0.5, and 1 M) and temperature (50, 100, and 150 °C) on the cotton, polyester, and textile structure were investigated. The pretreated textile, with over 90% cellulose, was subjected to anaerobic digestion, enzymatic hydrolysis, and fermentation to produce biogas, sugars, and ethanol, respectively. The maximum methane yields of 328.9 and 361.1 mL/g VS were achieved from pure cotton and jeans after pretreatment with 0.5 M Na2CO3 at 150 °C for 120 min, respectively. Using the pretreatment, the highest glucose yields of enzymatic hydrolysis were 88.0% and 81.71% for cotton and textile, respectively, while the corresponding values for untreated samples were 36.9 and 28.0%. The maximum ethanol yields of 69.4% and 59.5% were obtained from cotton and textile, respectively. It was concluded that the pretreatment is promising for the hydrolysis of the synthetic polymer of textile and the improvement of the biodegradability of the cellulosic part with negligible cellulose destruction. © 2018
BioResources (19302126)11(2)pp. 3230-3243
Cellulose Solvent-And organic Solvent-Based lignocellulose fractionation (COSLIF) has been repeatedly shown to be a Cost-Effective and promising process to modify the structure of different lignocelluloses. It has been repeatedly reported to improve enzymatic hydrolysis and ethanol production from different lignocelluloses. In this study, COSLIF was used to improve biomethane production from pine (softwood), poplar (soft hardwood), and berry (hard hardwood) via solid state anaerobic digestion (SSAD). Feed to inoculum (F/I) ratio, which plays a major role in SSAD, was set to 3, 4, and 5. After the pretreatment, 39, 33, and 24% higher methane yield from pine was achieved for F/I ratios of 3, 4, and 5, respectively. However, the methane yield from the hardwoods was not improved by the pretreatment, which was related to overloading of the digester. Compositional analysis showed considerable reduction in hemicellulose and lignin content by the pretreatment. Structural changes in the woods, before and after the pretreatment, were examined by X-Ray diffractometer and scanning electron microscopy. The results showed that the crystallinity of cellulose was decreased and accessible surface area was drastically increased by the pretreatment.
Bioresource Technology (09608524)209pp. 386-390
This study examined the effects of mild sodium carbonate (Na2CO3) pretreatment on enzymatic hydrolysis of different feedstocks (i.e., corn stover, Miscanthus, and switchgrass). The results showed that sodium carbonate pretreatment markedly enhanced the sugar yields of the tested biomass feedstocks. The pretreated corn stover, Miscanthus, and switchgrass gave the glucose yields of 95.1%, 62.3%, and 81.3%, respectively, after enzymatic hydrolysis. The above glucose yields of pretreated feedstocks were 2-4 times that of untreated ones. The pretreatment also enhanced the xylose yields, 4 times for corn stover and 20 times for both Miscanthus and switchgrass. Sodium carbonate pretreatment removed 40-59% lignin from the tested feedstocks while preserving most of cellulose (<5% cellulose loss). Corn stover appeared to be least resistant to breakdown by Na2CO3 and enzymatic hydrolysis. Our study indicated that mild sodium carbonate pretreatment was effective for reducing biomass recalcitrance and subsequently improving the digestibility of lignocellulosic biomass. © 2016 Elsevier Ltd.
Chemical Engineering and Technology (09307516)38(10)pp. 1802-1808
Inhibitory effects of high glucose and ethanol concentrations on ethanol production from wheat enzymatic hydrolysate by the zygomycetes fungus Mucor hiemalis were investigated and modeled. The ethanol yield was reduced by increasing the glucose concentration. Among different kinetic models, i.e., linear, Emerson, and modified Williams models, the latter successfully described the fungal growth kinetics. Considering the inhibitory effect of glucose, a model was developed for expressing the rate of ethanol production. In addition, the inhibitory effect of ethanol on ethanol yield was modeled. The model prediction satisfactorily covered the experimental data. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
BioMed Research International (23146141)2014
Organosolv pretreatment was used to improve solid-state anaerobic digestion (SSAD) formethane production fromthree different lignocellulosic substrates (hardwood elm, softwood pine, and agricultural waste rice straw). Pretreatments were conducted at 150 and 180°C for 30 and 60 min using 75% ethanol solution as an organic solvent with addition of sulfuric acid as a catalyst. The statistical analyses showed that pretreatment temperature was the significant factor affecting methane production. Optimum temperature was 180°C for elmwood while it was 150°C for both pinewood and rice straw. Maximum methane production was 152.7, 93.7, and 71.4 liter per kg carbohydrates (CH), which showed up to 32, 73, and 84% enhancement for rice straw, elmwood, and pinewood, respectively, compared to those from the untreated substrates. An inverse relationship between the total methane yield and the lignin content of the substrates was observed. Kinetic analysis of the methane production showed that the process followed a first-order model for all untreated and pretreated lignocelluloses. Copyright © 2014 Safoora Mirmohamadsadeghi et al.
Applied Clay Science (01691317)59pp. 8-12
A new type of modified clay was produced from a Ca-bentonite treated with hydrochloric acid as a surface modifier agent and then with hexadecyltrimethylammonium bromide (HDTMA) as a surfactant to produce an organophilic adsorbent. The specific surface area of the modified clays was 40% higher than the specific surface area of bentonite treated only with HDTMA. A series of kinetic and equilibrium tests was carried out to study the effectiveness of the modification method to improve the bentonite ability to remove phenol from aqueous solutions. The adsorption capacity of modified bentonite was 10 times greater than the natural bentonite. Phenol adsorption was fast and reached equilibrium in 30. min. Adsorption was physical and exothermic and was described with Henry and Freundlich isotherms. © 2012 Elsevier B.V.
