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• A porous SiO 2 /C composite was fabricated using wood pulp fiber as scaffold. • Alkali pretreatment could endow prepared SiO 2 /C composite with tubular morphology. • Si element can be distributed on the surface and inner wall of the SiO 2 /C composite. • The prepared SiO 2 /C composite exhibited a high initial coulombic efficiency. The microfibrils of wood pulp fibers in plant cell wall with an intrinsically regular and interlaced arrangement offer a stable porous structure. They could also provide outstanding mechanical strength and promote conductivity for Si-based materials. Upon these benefits, a method using wood pulp fibers to fabricate SiO 2 /C composite is proposed. In this work, the alkali pretreatment interfering hydrogen bonds in wood pulp fibers in situ results in an enlarged spatial distance among cellulose microfibrils, exposing more free-surface. This empowered homogenously inlaid SiO 2 distribution along the carbon skeleton in the subsequent carbonization process. A highly mesoporous and the tubular morphology was achieved in the fabricated SiO 2 /C composite. Furthermore, a high initial coulombic efficiency of 84.9 % and reversible specific capacity of 1130 mA h g−1 with a coulombic efficiency of 98.8 % after 200 cycles at a current density of 0.1 A g−1 was obtained. [ABSTRACT FROM AUTHOR]

• NaOH pretreatment improves spodumene flotation response. • NaOH pretreatment increases relative concentrations of Al at spodumene surface. • Increase in Al density for feldspar is not large enough to enhance oleate adsorption. • Spodumene surface has higher density of Al and unsatisfied Al sites than feldspar. • OH− is more readily to interact with Si sites at spodumene surface. In our latest study, surface dissolution of minerals has been found to be important in the flotation of spodumene. This study provides further information in the role of NaOH in the flotation separation of spodumene from feldspar and quartz using size distribution analysis, micro-flotation experiments, AFM imaging, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-atomic emission spectrometry (ICP-AES) measurements and density functional theory (DFT) calculations. NaOH pretreatment had no significant influence in the size distribution of minerals, while spodumene subjected to pretreatment with NaOH showed an increase in selective oleate adsorption. After being ground in NaOH solution, spodumene surface was smoother than feldspar and quartz surfaces as revealed by AFM imaging. ICP-AES results indicated that the dissolution of quartz was slight, and the concentration of dissolved species for spodumene and feldspar followed the order of Si ˃ Al ˃ Li, and Si ˃ K ˃ Al, respectively. The Al density at feldspar surface was smaller than that at spodumene surface. The increase in the relative concentration of Al at the feldspar surface with NaOH pretreatment was not large enough to significantly enhance oleate adsorption, and the decrease in the relative concentration of K and Na may be unfavorable for oleate adsorption. Increased relative concentrations of Al and Li at spodumene surface due to NaOH pretreatment accounted for the enhanced oleate adsorption. DFT calculation showed that elements at spodumene and feldspar surfaces were likely to dissolve, and OH− was more readily to interact with Si sites at spodumene surface and K sites at feldspar surface. [ABSTRACT FROM AUTHOR]

• Pretreatment of ERL at higher alkali strength relieved the cellulase adsorption. • Alkali pretreatment increased the desorption capacity of cellulase from ERLs. • Recoveries of cellulase from ERLs increased with the alkali strength increasing. • Bound-cellulase on alkali-pretreated ERLs showed activity, and can be reused easily. The knowledge about adsorption/desorption of cellulase on/from residual lignin is essential for efficient cellulose hydrolysis by recycling the cellulase from residual solid fraction. Herein, the impact of alkali pretreatment at different alkali strength on the adsorption/desorption of enzymatic residual lignins (ERLs) with cellulase was investigated. ERLs pretreated at stronger alkali strength had higher molecular weights and negative zeta potentials, but lower hydrophobicity. The inhibition of ERL to the enzymatic cellulose digestion was mitigated by alkali pretreatment, and inhibition degrees decreased from 21.5 % (with un-pretreated ERL) to 18.9 %, 12.9 %, and 10.8 % with the addition of ERLs treated with 0.5 %, 1.0 %, and 1.5 % (w/w) sodium hydroxide aqueous solution, respectively. The affinity of ERLs with cellulase diminished after alkali pretreatment, and the binding strength decreased from 183.0 to 130.7 mL/g with the alkali strength increasing, retaining more cellulase activities in supernatant. Desorption capacity of bound-cellulase from ERL increased after alkali pretreatment, and the recovery increased from 65.3% to 73.1% with the alkali strength increasing. The cellulase released after desorption exhibited hydrolytic activity, and higher glucose yields were obtained by the bound-cellulase on alkali-pretreated ERLs compared with that of un-pretreated ERL. The results provide references for the development of alkali pretreatment and recycling cellulase from residual lignin for efficient lignocellulosics digestion. [ABSTRACT FROM AUTHOR]

Castor, a non-edible oil crop that flourishes even under extreme cultivation conditions, can be cultivated in wastewater with a lower cultivation cost than similar plants, e.g., rapeseed and soybean. This plant, containing seeds and lignocellulosic residues, has a promising perspective for biofuel production. The oil extracted from the seeds is inexpensive and can be efficiently converted to biodiesel, while the lignocellulosic parts are suitable for ethanol production after pretreatment with NaOH. Biodiesel typically produced from the fossil-based methanol; however, it can also be produced from the ethanol. In this study, ethanol used for biodiesel production is produced from the lignocellulosic residues (scenario 1), which are more sustainable and environmentally friendly; the process was compared with that of the methanol (scenario 2). In this study, techno-economic analyses were used to compare the technical and economic aspects of producing biodiesel from methanol and the produced ethanol. Simulations of the processes were carried out by Aspen plus software, and economic studies were conducted by Aspen Economic Analyzer. The prices of produced ethanol as a byproduct in scenarios 1 and 2 were USD 0.701 and 0.693 per liter, respectively, which are greater than that of gasoline. The prices of biodiesel produced as a primary product for scenarios 1 and 2 are USD 0.410 and 0.323/L, lower than the price of diesel in the Middle East region. The profitability indices for scenarios 1 and 2 are 1.29 and 1.41, respectively. Therefore, despite environmental benefits, the biorefinery based on producing biodiesel from methanol is more economically feasible than that produced from ethanol. [ABSTRACT FROM AUTHOR]

• Methane yields were improved by 11.6–34.5% after pretreatment in batch mode. • Methane yield was positively correlated with lignin removal. • Methane yield increased by 80% after pretreatment in semi-continuous mode. • Low temperature alkali pretreatment was recommended for AD of PTL. • Alkali pretreatment accelerated the growth of Bacteroidetes and Methanosaeta. This study aimed at evaluating the valorization of a typical yard waste, phoenix tree leaf (PTL), through mild alkali pretreatment followed by anaerobic digestion (AD). To this end, L 9 Taguchi orthogonal biochemical methane potential (BMP) tests and semi-continuous AD experiments were conducted to examine the optimum pretreatment condition and the long term effect of alkali pretreatment on AD. The community structure evolutions were analyzed by high throughput 16S rRNA gene pyrosequencing. The results indicated that alkali pretreatment was effective on decrystallization and releasing more surface of PTL for enzyme attacking. The methane yield was positively correlated with lignin removal (R2=0.8242). In semi-continuous mode, 151.5±7.9 mL/g VS of the methane yield was obtained for alkali pretreated PTL, which was 80% higher than that of untreated one. Microbial community analysis indicated that alkali pretreatment led to a higher abundance of dominated bacteria (Bacteroidetes and Clostridia) and archaea of Methanosaeta. [ABSTRACT FROM AUTHOR]

Alkali pretreatment of anaerobic digestion (AD) was investigated as a strategy to degrade complex organic matter such as fats. AD of food waste (FW) with alkali pretreatment was conducted using batch assays and long-term experiments for 70 days in two reactors. The aim of this study was to compare the impact of alkali pretreatment on solubilization and biogas production and to evaluate the performance in reactors with that of the untreated FW. The alkali pretreatment enhanced the solubilization of organic matter. The best biogas yield (829 mL/g VS) and methane content (65.48%) were obtained by the pretreatment with 1% CaO with the highest P i, n (66.06%) of biodegradable soluble materials. The long-term reactors with pretreatment performed more steadily with higher biogas production under organic loading rates (OLR) over 5 g VS/(L⋅d). The bacterial community structure was different under various conditions. Methanosaeta and Methanospirillum were the dominant archaea in this study, while Methanosaeta increased in R1 at OLR of 6 g VS/(L⋅d). The study concluded that alkali pretreatment with 1% CaO appeared as a potential strategy for AD of FW. • Pretreatment with 1% CaO exhibits the highest biogas yield and methane content. • The P i, n of biodegradable soluble materials improves to over 66% with pretreatment. • The long-term reactors with alkali pretreatment of 1% CaO performed more stably. • Methanospirillum was the dominant microbe in reactor with pretreatment of 1% CaO. [ABSTRACT FROM AUTHOR]

• Black liquor was recycled to pretreat SCB under vacuum conditions. • Peak glucose yields were achieved at 0.35 g/g raw SCB following VABLR pretreatment. • No obvious variance in enzymatic digestibility after at least eight cycles of BL reuse. Black liquor (BL) remains a critical problem during alkaline pretreatment. To solve this issue, a novel pretreatment strategy termed vacuum-assisted black liquor-recycling pretreatment, was established to pretreat sugarcane bagasse (SCB). Firstly, SCB was pretreated with 2% NaOH at 121 °C for 1 h under vacuum conditions. The produced BL was used for subsequent pretreatments after pH recovery with NaOH. The pretreated SCBs were subject to enzymatic hydrolysis and separate hydrolyzation and fermentation (SHF) without washing to neutral pH. BL was recycled on seven occasions. The results indicated that glucose yields did not significantly differ between pretreatment with NaOH and recovered BL. The enzymatic hydrolysis and the fermentation resulted in maximum 0.35 g/g of glucose yield and 116.5 g/kg of ethanol yield respectively. Compared with conventional pretreatment with NaOH, the VABLR method showed high conversion rates of cellulose into monosaccharaides, whilst preserving ~20% and ~46% of alkali and water usage, respectively. [ABSTRACT FROM AUTHOR]

In the present study, the effect of low-temperature thermal and alkali pretreatments on biodegradability of waste activated sludge was evaluated. Combined with low-temperature thermal pretreatment (80 °C), varied proportions of a mixed alkali (i.e., a mixture of NaOH and Ca [OH] 2) were added. The pretreatment procedures were conducted in different orders; thermal-alkali pretreatment (TAP), simultaneous thermal and alkali pretreatment (STAP), and alkali-thermal pretreatment (ATP). Following pretreatment, the sludge with the alkali-thermal pretreatment was most considerably dissolved. The SCOD concentration was up to 18,000 mg/L in the WAS, and the dissolution rate reached 112.8%. Therefore, the anaerobic digestion (AD) performance of waste activated sludge (WAS) by mixed alkali-thermal pretreatment was investigated. With an increase in sodium hydroxide content in the mixed alkali, the cumulative methane production (CMP) of the sludge increased accordingly. The maximum CMP (i.e., 430 mL/g VS [volatile solids]), increased by 308.7% compared with untreated sludge and was obtained by the pretreatment of the mixed alkali (NaOH/Ca(OH) 2 = 4:1) at 80 °C. The results show that low-temperature thermal treatment combined with the mixed alkali treatment can reduce the inhibitory effect of mixed alkali on AD, thereby shortening the inhibition period (6d) and increasing methane production (308.7%). The preliminary economic feasibility analysis also showed that the ATP was a cost-effective pretreatment method. Image 1 • Low-temperature thermal-alkali pretreatment enhanced anaerobic sludge digestion. • Different orders of thermal and alkali pretreatments had different effects. • The optimum ratio of the mixed alkali was 4:1 for NaOH/Ca(OH)2. • Alkali-thermal pretreatment was optimum and the maximum CMP was 429.97 mL/g VS. [ABSTRACT FROM AUTHOR]

Ethanol is one of the widely used liquid biofuels in the world. The move from sugar-based production into the second-generation, lignocellulosic-based production has been of interest due to an abundance of these non-edible raw materials. This study interested in the use of Napier grass (Pennisetum purpureum Schumach), a common fodder in tropical regions and is considered an energy crop, for ethanol production. In this study, we aim to evaluate the ethanol production potential from the grass and to suggest a production process based on the results obtained from the study. Pretreatments of the grass by alkali, dilute acid, and their combination prepared the grass for further hydrolysis by commercial cellulase (Cellic® CTec2). Separate hydrolysis and fermentation (SHF), and simultaneous saccharification and fermentation (SSF) techniques were investigated in ethanol production using Saccharomyces cerevisiae and Scheffersomyces shehatae, a xylose-fermenting yeast. Pretreating 15% w/v Napier grass with 1.99 M NaOH at 95.7 °C for 116 min was the best condition to prepare the grass for further enzymatic hydrolysis using the enzyme dosage of 40 Filter Paper Unit (FPU)/g for 117 h. Fermentation of enzymatic hydrolysate by S. cerevisiae via SHF resulted in the best ethanol production of 187.4 g/kg of Napier grass at 44.7 g/L ethanol concentration. The results indicated that Napier grass is a promising lignocellulosic raw material that could serve a fermentation with high ethanol concentration. [ABSTRACT FROM AUTHOR]

• Alkaline pretreatment was the most effective in lignin removal of olive pomace. • Alkaline pretreatment increased methane produced by 30%. • Lipid contents in alkali and ultrasonic pretreated solids were highly reduced. • Single microwave and ultrasound were less effective than combined pretreatments. This study aims to investigate the effects of microwaves, ultrasonic and alkaline pretreatments on olive pomace properties and its biomethane potential. Alkaline pretreatment was found to reduce lipid and fiber contents (especially lignin) and to increase soluble matter. The alkali pretreatment at a dose of 8% (w/w TS) under 25 °C and for 1 day removed 96% of initial lipids from the solid olive pomace. Unlike NaOH addition, mild microwaves and ultrasonic pretreatments had no impact on lignin. However, in the case of long microwaves pretreatment (450 W-10 min), cellulose and lignin contents were reduced by 50% and 26% respectively. Similarly, the combination of ultrasonic and alkali reagent showed a positive effect on fiber degradation and lipid solubilization as well as a positive impact on methane production. Statistical analysis highlighted the correlation between NaOH dose, solubilization and methane production. The alkaline pretreatment at ambient temperature appeared the most energetically efficient. [ABSTRACT FROM AUTHOR]

• Non-valuable Cogongrass was effectively pretreated with NaOH under mild conditions. • Black liquor and wastewater were sequentially recycled for the next treatment step. • Alkali and water consumption were noticeably improved by recycling-based strategy. • Supplementation with Tween-80 significantly enhanced hydrolysis yield to over 90%. • The recycling-based pretreatment noticeably improved bioethanol process efficiency. The present investigation evaluated Cogongrass as a prospective non-edible feedstock for second-generation bioethanol. An innovative recycling-based strategy was employed to minimize chemical consumption and wastewater generation during the mild-alkali pretreatment. The biomass was pretreated with 2% (W/V) sodium hydroxide (SH) solution at 85 °C for 90 min and subsequently subjected to separate saccharification and fermentation. Accordingly, the produced black liquor (BL) and waste wash-water (WWW) were sequentially withdrawn and partially fed back to the next pretreatment and washing processes, respectively. The results indicated that enzymatic hydrolysis of the biomass was substantially improved from 24.8% up to 90.8% following the alkali pretreatment; and afterward, it was progressively decreased to a minimum value of 66.4% upon recycling BL and WWW for ten times. Parallel hydrolysis experiments were conducted in the presence of three non-ionic environmentally-friendly surfactants at different concentrations (0.25–2% V/V). Notably, supplementation with 0.5% (V/V) Tween 80 significantly improved hydrolysis yield of recycled BL (RBL) pretreated substrate to a maximum value of ~88%. Fermentation of the RBL-pretreated Cogongrass did not reveal any cell inhibition and resulted in maximum ~76% ethanol production yield, while also saving 59% of the water consumption and over 45% of the alkali usage. Detailed analyses of the biomass using semi-quantitative techniques revealed that enhanced cellulose accessibility to the enzyme, decreased crystallinity, and extensive lignin and hemicellulose removal were the key factors contributing to the observed improvements. [ABSTRACT FROM AUTHOR]

• 4-Vinylphenol (4-VP) was selectively produced from pyrolysis of alkali pretreated bagasse. • Ca(OH) 2 showed better ability than NaOH and Na 2 CO 3 to promote 4-VP formation. • The maximal 4-VP yield and selectivity reached 6.37 wt% and 58.90%. • Possible mechanism of alkali pretreatment on 4-VP formation was explained. Herbaceous biomass has been confirmed as a promising renewable source to produce the valuable phenol compound 4-vinylphenol (4-VP) from low temperature fast pyrolysis process. In this work, a novel and simple method was proposed to increase 4-VP production via alkali pretreatment of herbaceous biomass. Three alkali compounds, i.e., Ca(OH) 2 , NaOH and Na 2 CO 3 , were adopted to pretreat sugarcane bagasse for catalytic fast pyrolysis to selectively produce 4-VP. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were firstly conducted to investigate the effects of alkali type, alkali content, pyrolysis temperature, and pretreatment time on 4-VP formation. Quantitative results of 4-VP yield and selectivity suggested that Ca(OH) 2 was the optimal catalyst for bagasse pretreatment. Under pyrolysis temperature of 280°C with impregnation time of 10 min and Ca(OH) 2 content of 1 wt%, the highest 4-VP yield of 6.37 wt% and selectivity of 58.90% were obtained, compared with the yield and selectivity of 4.28 wt% and 39.95% from raw bagasse. Furthermore, a lab-scale fixed bed reactor was employed for fast pyrolysis of Ca(OH) 2 pretreated bagasse to quantitatively determine the distribution of solid, liquid and gas products. The maximal yield of 4-VP was 6.57 wt% obtained at 310°C. In addition, characterization of Ca(OH) 2 pretreated bagasse samples indicated that alkali pretreatment facilitated the release of 4-VP precursor during the impregnation process. [ABSTRACT FROM AUTHOR]

This paper evaluated the effectiveness of nitric acid pretreatment on the hydrolysis and subsequent fermentation of Jerusalem artichoke stalks (JAS). Jerusalem artichoke is considered a potential candidate for producing bioethanol due to its low soil and climate requirements, and high biomass yield. However, its stalks have a complexed lignocellulosic structure, so appropriate pretreatment is necessary prior to enzymatic hydrolysis, to enhance the amount of sugar that can be obtained. Nitric acid is a promising catalyst for the pretreatment of lignocellulosic biomass due to the high efficiency with which it removes hemicelluloses. Nitric acid was found to be the most effective catalyst of JAS biomass. A higher concentration of glucose and ethanol was achieved after hydrolysis and fermentation of 5% (w/v) HNO3-pretreated JAS, leading to 38.5 g/L of glucose after saccharification, which corresponds to 89% of theoretical enzymatic hydrolysis yield, and 9.5 g/L of ethanol. However, after fermentation there was still a significant amount of glucose in the medium. In comparison to more commonly used acids (H2SO4 and HCl) and alkalis (NaOH and KOH), glucose yield (% of theoretical yield) was approximately 47–74% higher with HNO3. The fermentation of 5% nitric-acid pretreated hydrolysates with the absence of solid residues, led to an increase in ethanol yield by almost 30%, reaching 77–82% of theoretical yield. [ABSTRACT FROM AUTHOR]

Anaerobic bioconversion of newsprint and waste office paper was performed in bench-scale reactors with three inocula sources: landfill, rumen, and anaerobic digester. Office paper bioconversion was nearly complete within 20 days but continued for about 165 days with methane yield efficiencies ranging from 71-85% of potential chemical oxygen demand (COD) conversion. Average newsprint methane conversion efficiencies ranged from 32-41% of total COD under strictly anaerobic conditions for 300 days. Mass balance calculations revealed that more than 80% of newsprint cellulose was biodegraded. The apparent limiting factor for anaerobic bioconversion of newsprint was the physical association between lignin and cellulose. After proper acclimation, the threeinocula tested equally well for methane production under strictly anaerobic conditions. Testing of ground, shredded strips, and whole paper pieces showed no effects of feedstock size on bioconversion rate or extent. Alkali pretreatment with NaOH concentration up to 10% significantly improved newsprint biodegradability. Treatment for longer duration or at elevated temperatures increased the solubilization of lignin, but did not improve bioconversion of newsprint to methane. Neutralizing treated samples with carbon dioxide gave higher methane yields compared to sulfuric or hydrochloric acids, suggesting that digester neutralization could be combined with biogas scrubbing. [ABSTRACT FROM AUTHOR]

Background: Enzymatic hydrolysis is a crucial step of biomass conversion into biofuels and different pretreatments have been proposed to improve the process efficiency. Amongst the various factors affecting hydrolysis yields of biomass samples, porosity and water accessibility stand out due to their intimate relation with enzymes accessibility to the cellulose and hemicellulose fractions of the biomass. In this work, sugarcane bagasse was subjected to acid and alkali pretreatments. The changes in the total surface area, hydrophilicity, porosity and water accessibility of cellulose were investigated by scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR)., Results: Changes in chemical and physical properties of the samples, caused by the partial removal of hemicellulose and lignin, led to the increase in porosity of the cell walls and unwinding of the cellulose bundles, as observed by SEM. (1)H NMR relaxation data revealed the existence of water molecules occupying the cores of wide and narrow vessels as well as the cell wall internal structure. Upon drying, the water molecules associated with the structure of the cell wall did not undergo significant dynamical and partial moisture changes, while those located in the cores of wide and narrow vessels kept continuously evaporating until reaching approximately 20% of relative humidity. This indicates that water is first removed from the cores of lumens and, in the dry sample, the only remaining water molecules are those bound to the cell walls. The stronger interaction of water with pretreated bagasse is consistent with better enzymes accessibility to cellulose and higher efficiency of the enzymatic hydrolysis., Conclusions: We were able to identify that sugarcane bagasse modification under acid and basic pretreatments change the water accessibility to different sites of the sample, associated with both bagasse structure (lumens and cell walls) and hydrophilicity (lignin removal). Furthermore, we show that the substrates with increased water accessibility correspond to those with higher hydrolysis yields and that there is a correlation between experimentally NMR-measured transverse relaxation times and the efficiency of enzymatic hydrolysis. This might allow for semiquantitative estimates of the enzymatic hydrolysis efficiency of biomass samples using inexpensive and non-destructive low-field (1)H NMR relaxometry methods.

The present investigation aims at studying the effectiveness of alkali-assisted ultrasonication on pretreatment of garden biomass (GB). Dry and powdered GB suspended in 1% NaOH was ultrasonicated for 15, 30 and 60 minutes at a frequency of 25 KHZ. The mode of action and effectiveness of alkali-assisted ultrasonication on GB was established through microscopic, scanning electron microscopic and X-ray diffraction studies. A perusal of results showed that alkali-assisted ultrasonication led to fibrillation of GB which ultimately facilitated enzymatic hydrolysis. The results also indicated that alkali-assisted ultrasonication is an efficient means of pretreatment of GB at moderate (45-50°C) working temperature and low (1%) concentration of alkali. The yield of reducing sugar after enzymatic hydrolysis increased almost six times as compared to control due to alkali-assisted ultrasonication.