Severity Factors Research Articles

Subcritical water hydrolysis of soybean hulls pretreated by steam explosion: High pressure integrated process strategy

Steam explosion (SE) pretreatment and sequentially subcritical water hydrolysis (SWH) was studied. Industrially, there is an advantage in using this process strategy, since it uses the same equipment and instrumentation, without the need to transport the raw material in separate stages. The influence of severity factors (SF) (2.75, 3.05, and 3.35) and solvent used (distilled water and 0.5 % w/w of H2SO4) were evaluated in the SE efficiency. SWH was perform in integrated processing using the best pre-treatment conditions. The influence of temperature (230 and 260 °C) and the solvent/feed ratio (40 and 80) were considered. The integrated system resulted in a FS yield of 19.19 ± 0.49 g/ 100 g SH, for a condition Integrated 230 °C, S/F-40, a FS yield 3.3 times greater than that obtained in the same condition with untreated soybean hulls, demonstrating the advantage of perform the process under this operating strategy (SE + SWH)

SARS-CoV-2 Omicron infection in acohort of hospitalized kidney transplant recipients: Risk factors ofseverity.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron is a major coronavirus variant, which was prevalent in China at the end of 2022 and caused widespread infection. As an immunosuppressed group, renal transplant recipients with SARS-CoV-2 infection are prone to developing serious pneumonia or an adverse outcome event if the infection is not treated in time. Here, we analyze the possible risk factors of infection severity. 92 cases of moderate and severe SARS-CoV-2 infection after renal transplantation were collected. Statistical methods, including Fisher's tests, F test, Spearman relative values, and multi-parameter logistic regression models, were used to analyze the risk factors for severe SARS-CoV-2 infection in renal transplant recipients. 44 cases complicated with hypertension were observed in the study cohort, among whom 30 were severe (OR: 4.63, p<0.001). Out of 51 male patients infected with Omicron, 30 male patients presented with severe SARS-CoV-2 (OR: 2.45, p=0.039). In renal transplant patients, hypertension comorbidity was closely correlated with clinical presentation (R = 0.369, p<0.001). Blood routine test, chemistries, and additional indices showed increased neutrophils and C-reactive protein in patients with severe disease compared with the moderate group according to one-way analysis of variance (p= 0.004), while CD3 (p = 0.02) and CD4 (p = 0.04) showed lower expressional levels. We also observed meaningful correlations between neutrophil levels and hypertension comorbidity (R = 0.222, p = 0.034) and between interleukin-6 (IL-6) levels and diabetes comorbidity (R = 0.315, p = 0.011), with IL-6 considered a key factor in the context of coronavirus disease. Renal transplant recipients were generally susceptible to infection with the Omicron variant, with a more pronounced incidence of severe illness observed in the group with hypertension comorbidity.

Chemical depolymerization of cork suberin with hydrothermal processes

This study presents for the first time results on hydrothermal treatments (autohydrolysis) of cork to assess their chemical effect on its structural components, namely on suberin. Extractive-free cork was autohydrolysed in isothermal conditions with a broad range of severity factors (SF) of 2.1–4.7 (120–180 °C, 60–240 min) determining mass loss and chemical changes in cork, namely on suberin content and composition. Mass loss was small for milder conditions, and increased steadily with severity e.g. 4.0% for SF 3.0, 9.8% for SF 3.8, 14.1% for SF 4.6. However, mass loss of cork by autohydrolysis is much smaller than that of lignocellulosic biomass under comparable treatment severity. Until SF 3.0, little chemical changes were seen, with SF 3.3–4.1, the autohydrolysed cork showed higher dichloromethane (DCM) solubles and suberin, and less polysaccharides, while for the most severe conditions (SF 4.4–4.7), there was a substantial increase of DCM solubles, a downfall in suberin and polysaccharides, and an unaltered lignin content. Cork polysaccharides decreased steadily with SF increase by hydrolysis of hemicelluloses, e.g. 7.1% of cork for SF 3.5% and 3.9% for SF 4.7. Suberin was maintained in cork until SF 4.4 without changes in composition, but decreased subsequently e.g. at SF 4.7, suberin represented 47% of the initial untreated cork (56% in the initial cork) and showed less ω-hydroxy acids and more α,ω-diacids. The amount and composition of suberin and DCM solubles in the autohydrolysed cork under the various reaction severities allow concluding that suberin is stable until 160 °C but depolymerizes at higher temperatures by ester bond cleaving mostly of mono-functional long-chain monomers. Overall cork showed higher hydrothermal stability than lignocellulosic materials.

Severity Factor (SF): An aid to developers for application of refactoring operations to improve software quality

AbstractBad smells are certain flaws in the structure of the code that might not disturb the normal functioning of a program but negatively affects the software quality. Developers use refactoring as a corrective measure for the treatment of bad smells. The current study aids the developers in the application of refactoring by identifying the critical classes, that is, classes that are challenging to maintain and are of degraded quality. In this study, 10 quality metrics and 10 bad smells have been selected to conduct an investigation on different releases of five open‐source systems. A new metric, severity factor (SF) has been introduced that categorizes the classes of the selected systems into four criticality levels—severe, major, mid, and low. Also, the relationship between SF, criticality levels, and the refactoring operations has been analyzed. The findings show that 60% of the total classes have been affected by bad smells, and long statement is the most dominant smell present in 27.6% of the classes. The results show 84% of the refactoring operations have been performed on highly critical classes. Thus, the SF metric plays a crucial role in driving the developer's attention to the critical classes that need to be treated urgently.

Acid assisted-hydrothermal carbonization of solid waste from essential oils industry: Optimization using I-optimal experimental design and removal dye application

Solid waste (SW) generated from extracting of essential oils from medicinal and aromatic plants (MAPs) is an abundant and renewable resource, but proper recycling is necessary to prevent negative environmental impacts from improper disposal. This study focused on converting SW from essential oil (EO) extraction industry by citric acid-catalyzed hydrothermal carbonization (c-HTC) coupled with chemical activation into a carbonaceous material to remove organic pollutants. For this purpose, an I-optimal design coupled with response surface methodology (RSM) was developed to investigate the relationship between the severity factor (SF) of the c-HTC process and citric acid dose (HTCcat) on carbon retention rate (CRR) and hydrochar mass yield (MY). Under optimal conditions (5.32 and 2 g for SF and HTCcat, respectively), an optimized hydrochar (HCop) was characterized by a CRR and MY of 71.02% and 56.14%, respectively. HCop was chemically activated by KOH solution (AHCop) and characterized by a specific surface area of 989.81 m2.g−1, a pore volume of 0.583 cm3.g−1, a higher heating value (HHV) of 37.3 MJ/Kg, oxygenated surface functions such as –OH, –COOH, C-O and a methylene blue (MB) removal rate of 90.71%. In addition, modelling of the adsorption isotherms found that the Freundlich isotherm better describes the experimental data, and the second-order model regulates the adsorption kinetics well. Furthermore, The maximum adsorption capacity of AHCop was 588.24 mg.g−1, with a separation factor of 0.625 under the operating conditions (t = 6 h, T = 25 °C, m(AHCop) = 0.2 g, [MB]0 = 300 mg.L-1, and pH = 7), indicating its potential for effectively removing organic pollutants. Together, these results provide crucial information on using c-HTC to convert waste biomass into functional carbon materials to remove organic pollutants efficiently. Therefore, several studies must be conducted out to discover other application fields of this material.

Optimizing hydrothermal dechlorination of PVC in a SS-316 reactor: From chemistry knowledge to material considerations

PVC remains one of the most challenging wastes for environmental activists and industrial recyclers because its decomposition products cause severe corrosion to equipment and our planet. The current study was designed to systematically investigate PVC dechlorination using the well-known Response Surface Methodology (RSM) to mature the process chemistry and assess the corrosion rate in the common SS-316 alloy. Undercover non-catalytic experiments, Cl removal, reactor wall corrosion rate, and H/C molar ratio of the products made the most argument to comprehend the chemistry and find the optimum operating condition. Based on data collected from different analytic techniques, like FESEM, SEM-EDX, TG, FT-IR, CHN, and AAS, it was found that water drove Cl removal through a combination of SN2 and Elimination pathways where the in-situ production of hydrochloric acid at high Severity Factor (SF) resulted in a desirably high dechlorination rate of 89.42%. However, significant metal leakage into the aqueous phase, e.g., 278.01 mg of Fe, in the Aqueous Phase (AP) necessitated the valorization of different approaches, including multistage dechlorination and application of various hetero and homogeneous catalysts, dealing with chloride and metal salts inside the reaction chamber. Among the solutions applied, the dual-stage and Ni-assisted dechlorination showed promising performances receptively with a corrosion rate as low as 0.034 g and the highest Cl removal efficiency of 96.18%.

Exploring the Valorization of Buckwheat Waste: A Two-Stage Thermo-Chemical Process for the Production of Saccharides and Biochar

To realize the utilization of the valorization of buckwheat waste (BW), a two-stage thermal-chemical process was explored and evaluated to produce saccharides and biochar. During the first stage, BW underwent a hydrothermal extraction (HTE) of varying severity to explore the feasibility of saccharides production; then, the sum of saccharides yields in the liquid sample were compared. A higher sum of saccharides yields of 4.10% was obtained at a relatively lower severity factor (SF) of 3.24 with a byproducts yield of 1.92 %. During the second stage, the contents of cellulose, hemicellulose, and lignin were analyzed in the residue after HTE. Enzymatic hydrolysis from the residue of HTE was inhibited. Thus, enzymatic hydrolysis for saccharides is not suitable for utilizing the residue after HTE of BW. These residues with an SF of 3.24 were treated by pyrolysis to produce biochar, providing a higher biochar yield of 34.45 % and a higher adsorption ability (based on methyl orange) of 31.11 % compared with pyrolysis of the raw BW. Meanwhile, the surface morphology and biomass conversion were analyzed in this study. These results demonstrate that the two-stage thermal-chemical process is efficient for treating BW and producing saccharides and biochar. This work lays a foundation for the industrial application of BW, and for improving the economic benefits of buckwheat cultivation.

Optimization of Autohydrolysis of Olive Pomaces to Obtain Bioactive Oligosaccharides: The Effect of Cultivar and Fruit Ripening

The valorisation of agro-industrial residues presents a challenge in obtaining economically sustainable and environmentally friendly industrial processes. Olive pomace is a by-product generated in large quantities, from olive oil extraction. This residue mostly consists of lignocellulosic materials. The aim of this study was to evaluate the potential use of extracted olive pomaces (EOP) obtained from olives with different ripening indexes (RI) and from different cultivars (Cobrançosa; RI = 2.5; 3.3 and 4.7; and Galega Vulgar; RI = 1.8; 2.9 and 4.8), to produce bioactive oligosaccharides from hemicelluloses by autohydrolysis. The hydrothermal treatment conditions were optimized by Response Surface Methodology, following a central composite rotatable design (CCRD), as a function of temperature (T: 142–198 °C) and time (t: 48–132 min), corresponding to severity factor (SF) values from 3.2 to 4.9. For all pomace samples, soluble sugar production was described by concave surfaces as a function of temperature and time. Autohydrolysis with SF equal or higher than 4.0 produced higher sugar yields, with maximum values around 180 g glucose equivalent/kg EOP for SF of 4.7 (190 °C/120 min) or 4.9 (198 °C/90 min). These values were similar for both cultivars and were not dependent on the ripening stage of the olives. Maximum oligosaccharide (OS) yields of 98% were obtained by autohydrolysis with SF of 4.0. The increase in SF to 4.9 resulted in a decrease in OS yield to 86–92%, due to the release of monomeric sugars. The monosaccharides were mostly xylose (55.8–67.7% in Galega; 50.4–69.0% in Cobrançosa liquid phases), and glucose, galactose, arabinose and rhamnose, in smaller quantities. Therefore, the production of bioactive xylo-oligosaccharides (XOS) from olive pomaces mainly depends on the hydrothermal conditions used.

Process Optimization and Stability of Waste Orange Peel Polyphenols in Extracts Obtained with Organosolv Thermal Treatment Using Glycerol-Based Solvents

This study was focused on the simultaneous organosolv treatment/extraction of waste orange peels (WOP) for the effective recovery of polyphenolic antioxidants. The treatments were performed with aqueous glycerol mixtures, which were acidified either with citric acid or hydrochloric acid (HCl). Process optimization was carried out using response surface methodology and comparative appraisal of the different processes tested, based on both the extraction efficiency factor (FEE), severity factor (SF) or combined severity factor (CSF). Metabolite stability was also of major concern, and it was examined by deploying liquid chromatography-mass spectrometry. The results drawn suggested 90% (w/w) glycerol to be the highest-performing system, providing a yield in total polyphenols of 44.09 ± 5.46 mg GAE g−1 DM at 140 °C for 50 min, with a FEE of 2.20 and an SF of 2.88. Acidification with 1% citric acid was proven less efficient and equally severe, whereas acidification with 1% HCl was less severe but also less efficient. The major disadvantage associated with the use of HCl was its detrimental impact on the polyphenolic composition of WOP since major metabolites, such as narirutin, hesperidin and didymin, did not survive the process. By contrast, the formation of lower molecular weight compounds was observed. With regard to antioxidant properties, the extract obtained with aqueous glycerol displayed significantly higher antiradical activity and reducing power, which was in line with its higher concentration in total polyphenols. It was concluded that organosolv treatment with aqueous glycerol under the conditions employed may boost polyphenol recovery from WOP, thus giving extracts with powerful antioxidant characteristics.

Effect of highly efficient steam explosion treatment on beech, poplar and spruce solid wood physicochemical and permeable performances

The effect of steam explosion treatment (SE) on the appearance and water permeability of solid beech, poplar, and spruce wood was investigated. Wooden test specimens were steam blasted after water or acid impregnation at 10 ~ 16 bar for 5 ~ 15 min, and their chemical composition was determined by chromatographic analysis after hydrolysis and infrared spectroscopy. Macro/micro cracks with shrinkage and reduced sphericity after drying were observed by scanning electron microscopy. Darker color and more severe changes in colorimetric parameters were measured spectrophotometrically for SE treated samples, especially under acidic conditions or higher severity factors (SF). To some extent, the physicochemical and permeability properties of SE treated wood samples could be simulated by considering the correlations of the different factors. No significant deterioration in chemical content, longitudinal compressive modulus of elasticity (MOE//) and modulus of rupture (MOR//) was observed in SE specimens treated with water. Higher permeability was obtained under a mild condition of 180 °C-5 min for poplar and a higher SF condition for beech and spruce. Therefore, SE could be an efficient method for modifying solid wood to improve its permeability and functionality.

Optimum Torrefaction Range for Macaw Husks Aiming Its Use as a Solid Biofuel

Abstract Biomass feedstock is broadly available in many countries, and a significant amount of residual biomass comes from agriculture and forest crops. This study aims to identify a consistent criteria for optimize Macaw husks torrefaction process maximizing the energy content and minimizing the mass loss. The optimization criteria is based on the severity factor (SF), HHVTorrefied, and ηSolid-Yield. The energy density (ρEnergy) does not provide consistent and indisputable evidence as an optimization criteria; the same applies to energy-mass co-benefit index (EMCI) and ηEnergy-Yield. This investigation combined few temperatures (180 °C, 220 °C, and 260 °C) with different residence times (20, 40, and 60 min) and found that the optimum torrefaction range for Macaw husk is 220 &amp;lt; T (°C) &amp;lt; 240 and 10 &amp;lt; t (min) &amp;lt; 40. The best experimental result was 220-40 (dry torrefaction at T = 220 °C and t = 40 min) corresponding to SF ∼ 5.14 and HHVTorrefied ∼ 21.71 MJ/kg (ηSolid-Yield ∼ 0.86 and HHVRatio ∼ 1.14). As the raw material has small ρBulk or ρEnergy, the authors suggest the use of a densification process previously to torrefaction. The obtained solid final product had high-quality biofuel following properties: FCdb, H/C, and O/C ratios, high heating value (HHV). The gain and loss optimization method seems promising to identify the optimum torrefaction parameters for any biomass species and the obtained optimum temperature is not far from the ones available as waste heat in industrial processes.

Toxoplasma gondii as a possible risk factor for COVID-19 severity: a case-control study

Background: COVID-19 is a worldwide pandemic that stroke almost all countries of the world causing thousands of deaths and disabilities and burdened the economy of countries. One of the main criteria of the immune response against COVID-19 is the “immune exhaustion”, due to increased expression of T cell suppressor molecules e.g. programmed death-1 (PD-1), that leads to flaring of viral multiplication and disastrous clinical outcomes. This immune exhaustion is not restricted to COVID-19 but is also a common complication of chronic infections with the widely spreading protozoan, Toxoplasma (T.) gondii. Thus, theoretically, the toxoplasmosis-associated immune exhaustion can worsen that of COVID-19 and consequently increases its severity. However, the studies on this theory are still insufficient. Objective: this work was designed to answer two questions. Does T. gondii co-infection affect the severity of COVID-19 manifestations? Is this action related to T. gondii-induced PD-1 changes? Methodology: Covid-19+ patients with moderate and severe conditions were screened for T. gondii IgG and compared to healthy controls. Serum levels of IL-1β, IL-6, TNFα, IFNγ, IL-1α cytokines were assessed to evaluate COVID-19 severity and prognosis. Lymphocytic expression of PD-1 was assessed by flowcytometry. Results: We recorded a higher incidence of toxoplasmosis among COVID-19 patients especially patients with severe/critical manifestations. T. gondii positive cases exhibited a statistically significant increase in lymphocytic expression of PD-1 that correlated positively with the proinflammatory and bad prognosis cytokines. With fixation of other risk factors for severity, toxoplasmosis still scored a significant value. Conclusion: toxoplasmosis increased the severity of COVID-19. These effects can be related to the Toxoplasmaassociated increased lymphocytic PD-1 expression. So, toxoplasmosis can be considered as an unrecognized independent risk factor for COVID-19 severity.

Evaluation of Steam Explosion Pretreatment and Enzymatic Hydrolysis Conditions for Agave Bagasse in Biomethane Production

The production of biofuels from lignocellulosic biomass includes a pretreatment step to alter the biomass structure and facilitate the enzymatic degradation of the polymers to obtain assimilable compounds. In this study, agave bagasse (AB) was used as a feedstock for obtaining methane, for which AB was pretreated with steam explosion and enzymatically hydrolyzed. The pretreatment conditions corresponded to severity factors (SFs) within a range from 1.65 to 2.89, while enzymatic hydrolysis was performed with enzyme loads of Cellic CTec2 within a range from 0.12 to 3.6 mgprotein g−1AB. The best global yields (including pretreatment and enzymatic hydrolysis) of total carbohydrates (TCs), glucose (GLU), xylose (XYL), and chemical oxygen demand (COD) were 0.7 g TC g−1AB, 0.12 g GLU g−1AB, 0.03 g XYL g−1AB, and 0.20 g O2 g−1AB obtained using 2.4 mgprotein g−1AB of Cellic CTec2 with agave bagasse pretreated with an SF of 2.41. The contribution of pretreatment to the global TC yield ranged from 13 to 34% for the different systems evaluated. The biochemical potential of methane (BMP) of hydrolysates (pretreatment at SF 2.41 and 2.4 mgprotein g−1AB of Cellic CTec2) was 0.284 ± 0.02 in NL CH4 g−1 COD with a COD removal of 78.4 ± 1.3. This BMP value was 40% higher than the BMP obtained in the system without enzymatic hydrolysis, indicating the impact of this step on conversion to biomethane. The results at the BMP level indicated the potential of this residue for biofuel production.

Effect of Severity Factor on the Subcritical Water and Enzymatic Hydrolysis of Coconut Husk for Reducing Sugar Production

Preventing the further degradation of monomeric or oligomeric sugar into by-product during biomass conversion is one of the challenges for fermentable sugar production. In this study, the performance of subcritical water (SCW) and enzymatic hydrolysis of coconut husk toward reducing sugar production was investigated using a severity factor (SF) approach. Furthermore, the optimal condition of SCW was optimized using response surface methodology (RSM), where the composition changes of lignocellulose and sugar yield as responses. From the results, at low SF of SCW, sugar yield escalated as increasing SF value. In the enzymatic hydrolysis process, the effect of SCW pressure is a significant factor enhancing sugar yield. A maximum total sugar yield was attained on the mild SF condition of 2.86. From this work, it was known that the SF approach is sufficient parameter to evaluate the SCW and enzymatic hydrolysis of coconut husk. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Effects of operational conditions on auto-catalyzed and sulfuric-acid-catalyzed hydrothermal pretreatment of sugarcane bagasse at different severity factor

Bagasse, a major by-product of sugarcane-processing industries, has potential to play a significant role as feedstock for production of cellulosic ethanol, platform chemicals, and bio-based commodities. Pretreatment is essential for efficient processing of lignocellulosic feedstocks by biochemical conversion. In this work, auto-catalyzed (A-HTP) and dilute sulfuric-acid-catalyzed (SA-HTP) hydrothermal pretreatment of sugarcane bagasse was investigated, setting the temperature (175−205 °C) and the time (4−51 min) in such a way that the severity factor (SF) was always maintained at one of three predetermined values (2.8, 3.8, and 4.8). The investigation covered the effects of different operational pretreatment conditions on (i) the formation of sugars and water-soluble bioconversion inhibitors, including newly discovered inhibitors such as formaldehyde and p-benzoquinone, in the pretreatment liquid, (ii) the chemical composition and recovery of constituents in the solid phase, as determined using two-step treatment with sulfuric acid, Py-GC/MS, and solid-state NMR, (iii) pseudo-lignin formation, (iv) furan aldehydes in condensates from the gas phase, (v) enzymatic digestibility of pretreated solids, (vi) enzyme inhibition by pretreatment liquids, and (vii) fermentability of pretreatment liquids using Saccharomyces cerevisiae yeast. Glucose and xylose were the predominant sugars in pretreatment liquids from SA-HTP and A-HTP, respectively. For A-HTP, the enzymatic digestibility of the pretreated solids was proportional to the SF, while for SA-HTP no clear trend was observed. The best enzymatic digestibility (above 80%) was achieved for A-HTP performed at SF 4.8. The highest total yields of glucose and xylose, the predominant sugars, were achieved for A-HTP at SF 3.8 and temperatures of 190 °C and 205 °C. The fermentability of the pretreatment liquids by Saccharomyces cerevisiae was lower for SA-HTP than for A-HTP. The investigation suggests that hydrothermal pretreatment of sugarcane bagasse can be performed with good results without addition of sulfuric acid, but that the conditions must be just harsh enough to almost quantitatively solubilize the hemicelluloses.

Binderless fuel pellets from hydrothermal carbonization of municipal yard waste: Effect of severity factor on the hydrochar pellets properties

It has become crucial to understand the combined effect of temperature and time on hydrochar pellets quality if large scale pellets production is envisaged. This study investigated the effect of hydrothermal carbonization (HTC) of yard waste at different severity factor (SF) based on the Arrhenius equation on the fuel, mechanical, storage, transport and combustion characteristics of the hydrochar pellets. No additional binder was used. The increasing SF level during HTC has a direct effect on the calorific value and energy density of the hydrochar pellets. Tensile strength of the hydrochar pellets increased from 1.53 MPa to 4.80 MPa for lowest and highest SF level respectively. The natural length expansion of hydrochar pellets was maximum (21%) for lower SF, and was minimum (7%) for higher SF level pellets. Higher SF level increased the mass (1662 kg/m3) and energy (42 MJ/m3) density of pellets as compared to lower SF level (1473 kg/m3 and 27 MJ/m3 respectively). The result of hydrophobicity, impact resistance and length expansion revealed that the lower SF level hydrochar pellets has lower durability as compared to higher SF level hydrochar pellets. Higher SF level improved combustion performance of hydrochar pellets which was evident from the improved burnout and ignition temperature. The study revealed that densified, durable, energy-rich fuel pellets could be produced from municipal yard waste using HTC at a higher SF level without using any binders thus identifying itself as a valuable renewable energy source.

Torrefaction performance prediction approached by torrefaction severity factor

Torrefaction is a crucial biomass upgrading technology to produce biochar for fuel, soil amendment, and bio-absorbent. A number of indicators such as weight loss (WL), torrefaction severity index (TSI), and severity factor (SF) have been conducted to describe the torrefaction degree. However, operating conditions such as torrefaction temperature and duration are not considered in weight loss and torrefaction severity index, while biomass nature is not taken into account in the severity factor. To overcome these drawbacks, an indicator termed torrefaction severity factor (TSF) is proposed by introducing a time exponent in the severity factor. Four different biomass materials of Chinese medicine residue, Arthrospira platensis residue, C. sp. JSC4, and spent coffee grounds are examined. After the optimization of the time exponent, TSF can accurately correlate weight loss and thereby torrefaction severity, and improve the prediction up to 13% when compared to severity factor. In addition, the results suggest that TSF is able to appropriately predict the enhancement factor of HHV and energy yield where the coefficient of determination (R2) is beyond 0.83. Overall, TSF has successfully combined the operating conditions (temperature and duration) and biomass species, can be utilized for predicting torrefaction performance. This gives a simple and fast way for torrefaction operation and reactor design, thereby achieving time-saving and efficient predictions.

A Mild Thermal Pre-treatment of the Organic Fraction of Municipal Wastes Allows High Ethanol Production by Direct Solid-state Fermentation

A solid standard mixture (SSM) representing the annual composition of fresh fruits and vegetables residues generated at the Supply Center in Mexico City was used for bioethanol production. This type of residues allows bioethanol production with a single thermal pre-treatment instead of hard thermochemical or enzymatic treatments. The release of fermentable carbohydrates from the SSM by a mild thermal pretreatment was firstly optimized. After that, mixed and single cultures of Saccharomyces cerevisiae, Scheffersomyces stipitis, and Schwanniomyces occidentalis were evaluated for bioethanol production. The maximum ethanol production, 282.61 ± 13.09 L ethanol per ton of dry matter (DM), was reached using a severity factor (SF) of 2.35 and a mixed culture composed of Saccharomyces cerevisiae, Scheffersomyces stipitis, and Schwanniomyces occidentalis. The improved lab scale conditions were evaluated in a pilot scale (18 Kg) stirred bioreactor with an SF of 2.35 and the mixed culture, obtaining 245.72 ± 17.76 L ethanol per ton DM. The obtained results demonstrate for the first time the use of fresh fruits and vegetables residues for bioethanol production under solid-state culture conditions without any thermochemical or enzymatic pre-treatment.

Effect of severity factor on the hydrothermal pretreatment of sugarcane straw

The recalcitrant structures of sugarcane straw and related lignocellulosic biomasses require a pretreatment step to enable a better enzymatic attack during the hydrolysis. Factors like the energy consumption and the formation of inhibitors require the optimization of the pretreatment step. Thus, the influence of different severity factors (SF) on hydrothermal (also called liquid hot water, LHW) pretreatment was evaluated using a factorial design 22 with central point. The obtained results showed that low values of SF (<3.39) did not promote reasonable alteration in the sugarcane straw structures, whereas high SF values (>4.70) resulted in loss of hydrolyzed sugars, generation of inhibitors such as furfural, and formation of pseudo-lignin structures, despite high hemicellulose removal (∼97%). The residence time exhibited low influence on LHW. An optimum condition was found for the process (10 min and 195 °C) with low cellulose solubilization (9.80%) and a reasonable hemicellulose removal (85.45%).

A novel hybrid first and second generation hemicellulosic bioethanol production process through steam treatment of dried sorghum biomass

Sweet sorghum was subjected to an impregnation step, which recovered most of the 1st generation sugars, prior to a steam-treatment extraction of the 2nd generation sugars, at three different severity factors (SF). A medium severity (3.56 SF) treatment proved to be an optimal compromise between the amount of sugars extracted and the fermentation inhibitors generated following the subsequent depolymerization approaches applied on the broth. Next, a series of detoxification approaches (ozonation, overliming and a combination of both) were investigated following a concentration and depolymerization step. Results show that higher steam-treatment severity required more intense detoxification steps. However, when combining the 1st and 2nd generation streams at a 2:1 ratio, the inhibitors did not affect the fermentation process and ethanol yields above 90% of the theoretical maximum were achieved.