Surplus availability of rice straw (RS) presents it as a potential feedstock for ethanol production. Steam explosion (SE) is considered as a green approach to extract fermentable sugars at lower cost. The present study deals with the reaction condition optimization for water and dilute acid assisted steam explosion of rice straw at different temperatures and explores the effect of structural properties of solid residue on enzymatic hydrolysis along with mass balance. SE conditions were optimized at pilot scale, raising the temperature from 170 to 200 °C in water assisted SE resulting in an increased glucan conversion from 21.4 to 42.5% at 15% solid loading using 1.5 FPU of cellulases g –1 biomass. Further, it was improved up to 58.7% by increasing the enzyme dosage to 5 FPU, although it might lead to enhanced enzyme cost by threefold. To reduce costs, small amount of dilute acid (DA) was added during SE and lowering of enzyme consumption i.e. 1.5 FPU/g cellulose has been used to achieve 65.5% glucan conversion. Varying temperature and incorporate dilute acid during pretreatment induced structural alterations in biomass evident by compositional analysis, FT-IR and mass balance. Mass balance study revealed that the overall sugar recovery i.e. 58.7 and 38.8% and theoretical yield of ethanol shall be 222 and 186 L ton –1 RS respectively, with and without DA addition. Graphical Abstract

The depletion of fossil fuel reserves with increased fuel demand and global emissions has increased the search for eco-friendly renewable fuels with a low environmental impact. Biodiesel can be considered as mono-alkyl esters of long-chain fatty acids obtained from the transesterification of vegetable oils and animal fats. Economically low-cost biodiesel production has received considerable interest for blending with fossil-based diesel for a more sustainable future. Therefore, the current study focuses on synthesizing an efficient, low-cost heterogeneous CaO catalyst from waste egg and seashell using a solid-state method and applying it to the transesterification of Jatropha oil. The Ca2Fe2O5 solid catalyst was prepared by doping calcined CaO with iron in a 2:1 ratio using ferric oxide (Fe2O3). Furthermore, the catalyst was extruded and analytically characterized using XRD, FT IR, BET, and its basic strength was quantified by Hammett indicators. Later on, transesterification of Jatropha oil was optimized by varying reaction parameters, such as the molar ratio of methanol to Jatropha oil, reaction time, and catalyst loading. The maximum conversion yield was 96.3% at a 20:1 methanol-to-oil ratio and 80 bar N2 pressure using 5% (w/w) catalyst loading. Furthermore, the catalytic recycling study demonstrated that the Ca2Fe2O5 catalyst could retain > 70–80% of transesterification efficiency and stability up to 4 cycles under high acid value and moisture conditions.

This study focused on an approach to improve sugar recovery at low enzyme dosages by maintaining low acid catalyst consumption. Rice straw has been used for ethanol production and steam explosion is applied as a green approach to extract fermentable sugars from biomass. Process conditions were optimized at pilot scale by varying the temperature from 170 to 200 o C in water assisted reactions resulting in a glucan conversion from 21.4 to 42.5% at 15% solid loading using 1.5 FPU g -1 biomass. Further, glucan conversion is improved to 58.7% by increasing the enzyme dosage to 5 FPU consequently enhanced enzyme cost by 3-fold. To reduce cost, a small amount of dilute acid was added in the reaction media producing 65.5% glucan conversion. Mass balance study revealed that the yield of ethanol to be 222 and 186 L ton -1 biomass, with and without acid addition respectively.

Lignin is produced as a byproduct in cellulosic biorefinery as well in pulp and paper industries and has the potential for the synthesis of a variety of phenolics chemicals, biodegradable polymers, and high value-added chemicals surrogate to conventional petro-based fuels. Therefore, in this critical review, we emphasize the possible scenario for lignin isolation, transformation into value addition chemicals/materials for the economic viability of current biorefineries. Additionally, this review covers the chemical structure of lignocellulosic biomass/lignin, worldwide availability of lignin and describe various thermochemical (homogeneous/heterogeneous base/acid-catalyzed depolymerization, oxidative, hydrogenolysis etc.) and biotechnological developments for the production of bio-based low molecular weight phenolics, i.e. polyhydroxyalkanoates, vanillin, adipic acid, lipids etc. Besides, some functional chemicals applications, lignin-formaldehyde ion exchange resin, electrochemical and production of few targeted chemicals are also elaborated. Finally, we examine the challenges, opportunities and prospects way forward related to lignin valorization.

The present study deals to visualise the impact of various process parameters, i.e. particle size and impregnation media over sugar released during steam explosion pretreatment. For this, 5, 10 and 20 mm rice straw sizes were impregnated in water and dilute acid media (1%) followed by steam explosion at 180 and 200 degrees C. Pretreated slurry was further hydrolyzed by 5 and 10 FPU g(-1) of residue varying 15 and 20% solid loading. The result showed that 10 mm particle size gave highest glucan conversion (88.7%) in acid impregnated steam explosion at 180 degrees C using 5 FPU g(-1) of residue with 15% solid loading. Comparatively, water impregnated pretreated biomass results significantly lower glucan conversion (61.1%), which was further intensified to 77.7% at 10 FPU g(-1) of residue with increased temperature. Furthermore, mass balance, compositional and structural transformation studies support our finding. Overall 30.6-81.1% sugar recovery was achieved with/or without acid pretreatment respectively.

Rice straw has a great potential for ethanol production due to its richness in polysaccharides and abundant availability, however, for efficient utilization of these polysaccharides, size reduction is a prerequisite step. Therefore, biomass particle size plays a vital role for cellulosic ethanol commercialization. In this study, the effects of rice straw particle size on dilute acid pretreatment efficiency and enzymatic hydrolysis are investigated. Different sizes; 5, 10 and 20 mm were subjected to dilute acid pretreatment in a continuous pilot scale system with a horizontal screw feeder reactor followed by enzymatic hydrolysis at varying solids (10 and 15%) and enzyme dosages (5 and 10 FPU/g of pretreated residue). The glucan hydrolysis for 5, 10 and 20 mm are 65.6, 80.0 and 60.0% using 5 FPU and 79.5, 93.4 and 72.8% using 10 FPU/g pretreated residue respectively at 10% loading, whereas, at 15% it is significantly lower in respective experiment. Overall sugar recovery with 10 mm is 63.8 and 72.9% with 5 and 10 FPU respectively. RS with 10 mm biomass particle size at both solid loadings and enzyme dosages resulted in much higher enzymatic hydrolysis than others and in turn the overall sugar recovery and this was found to be due to the variation in the degradation products and pseudolignin contents in the pretreated biomass. The insight into the structural intricacies of biomass after pretreatment are studied using FT-IR and SEM revealing significant changes in biomass properties responsible for improved sugar recovery.

Owing to the finite supply of fossil fuels, greenhouse gasses emission, global warming, increasing price, and unexpected fluctuations, there is a need to pay attention for alternative energy resources and thus interest in ethanol which is renewable, environmentally sustainable, and economically viable fuel has been strengthened. Due to economic and environmental concerns cropped up with the use of the first-generation ethanol processes, second-generation ethanol processes which comprise the use of waste biomass, viz., agricultural crop residues, municipal solid waste, sludge, livestock manure, etc., has been contemplated to be the hot emerging field. However, due to many technological issues, development of an effective technology is still a challenge. This chapter, therefore, provides insight into the pretreatment technologies involved in the production of free sugars which can be fermented to ethanol along with discussion on the merits and demerits of each of the technologies and their future prospects. This chapter also deals with various biomass-related issues and the updated technology status along with commercial aspects.

Multiple enzymes are required for efficient hydrolysis of lignocellulosic biomass and no wild type organism is capable of producing all enzymes in desired levels. In this study, steam explosion of wheat straw was carried out at pilot scale and a synthetic enzyme mixture (EnzMix) was developed by partially replacing the cellulase with critical dosages of commercially available accessory enzymes (beta-glucosidase, xylanase and laccase) through central composite design. Highest degree of synergism (DS) was observed with beta-glucosidase (1.68) followed by xylanase (1.36). Finally, benchmarking of EnzMix (Celluclast, beta-glucosidase and xylanase in a protein ratio of 20.40: 38.43: 41.16, respectively) and other leading commercial enzymes was carried out. Interestingly, hydrolysis improved by 75% at 6 h and 30% at 24 h, respectively in comparison of control. By this approach, 25% reduction in enzyme dosage was observed for obtaining the same hydrolysis yield with opitimized enzyme cocktail. Thus, development of enzyme cocktail is an effective and sustainable approach for high hydrolysis efficiency.

Dilute acid (DA) pretreatment at pilot level failed for cotton stalk (CS) due to the technical issues posed by its inherent nature. Reasonable glucan conversion has been reported via two-stage pretreatment but adds on to the process cost. Proposed herewith is a single-stage steam explosion (SE) process preceded by water extraction resulting in high sugar recovery from CS. Raising the extraction temperature to 80 degrees C increased the glucan conversion from 37.9 to 52.4%. Further improvement up to 68.4% was achieved when DA was incorporated during the room temperature extraction. LC-MS revealed the formation of xylo-oligomers limiting the glucan conversion in proportion to the length of xylo-oligomers. Varying extraction conditions induced structural alterations in biomass after SE evident by compositional analysis, Infrared Spectroscopy, X-Ray Diffraction and Scanning Electron Microscopy. Overall glucose recovery, i.e. 75.8-76.7% with and without DA extraction respectively was achieved. (C) 2017 Elsevier Ltd. All rights reserved.

Cost of cellulases is a major impediment in commercialization of cellulosic ethanol. To reduce the enzyme doses for the production of fermentable sugars from rice straw (RS), a series of alkali conditioning experiments were conducted prior to dilute acid (DA) pretreatment. This approach resulted in removal of a majority of extractives, ash, acetic acid, and part lignin, and thus resulted in lowering pseudolignin formation thereby increasing enzymatic hydrolysis yields. Glucan hydrolysis of 69.8%, 74.0%, and 83.5% was obtained at 10 wt % water insoluble solid (WIS) using 8 FPU enzyme/g WIS of biomass conditioned using 0.2, 0.4, and 0.5 wt % alkali prior to pretreatment, which is 14-37% higher than the control (61.0%). The overall sugar recovery in these experiments were 69.2%, 70.2%, and 68.5% at 15 wt % WIS resulting in a sugar concentration greater than 120 g/L, which in turn can produce approximately 5-6% w/v ethanol concentration in fermentation broth. It was found that this approach resulted in a decrease of the enzyme consumption vis-a-vis the conventional process by 46.4% to recover the same amount of sugars. This lowering of enzyme consumption has resulted in net savings, after taking into account the cost of alkali used in the conditioning steps.

Lignocellulosic biomasses (LCB) differ in their chemical composition and cell wall architecture from one another and within the same LCB due to varying geographical conditions. Thus, pretreatment parameters need optimization for recovery of sugars across different biomasses. In the current study, Acacia mangium has been investigated at bench scale for its potential as a feedstock for fermentable sugar production. Attempts were first made to target hydrolysis of hemicellulose using dilute acid (DA) as a catalyst. Pretreatment at temperature of 160 degrees C, residence time of 30 min and H2SO4 concentration of 2% (w/w) yielded highest overall saccharification efficiency (50%) corresponding to a glucan conversion in enzymatic hydrolysis (57.8%). Further enhancement in glucan conversion and reduction in the formation of inhibitors was brought about by using sodium sulfite (SS). It was observed that SS caused a significant increase in overall sugar recovery. Interestingly, the order in which SS and DA were added to the pretreatment medium was an important strategy to improve enzymatic saccharification. The condition (SS -> DA) where sodium sulfite (SS) was added right in the beginning along with the biomass followed by dilute acid (DA) addition at the desired temperature was more effective in improving the glucan conversion yield (77.0%). Highest BET surface area of SS -> DA residue (3.7 m(2)/g) among all the pretreated residues is one of the factors contributing to this high conversion yield. To get further insight into the basis for improved saccharification, cellulase adsorption studies were conducted. The results showed that the solid residue obtained by SS -> DA despite having the lowest maximum adsorption capacity (sigma(max)) resulted into highest saccharification yield which was supported by its highest affinity constant (K-a = 0.25 mL/mg) for the enzyme. Among the pretreated residual solids, SS -> DA residue showed lignin modification and cellulose peak alterations by FT-IR spectroscopy and increased surface area by BET measurement revealing implication in improved enzymatic saccharification and overall sugar recovery.

Lignocellulosic material (LCM) is promising alternative resource for sustainable energy production such as ethanol and butanol and biohydrogen. Cellulose is an abundant renewable polymer of LCM found in plant cell walls (30-50%). The high crystallinity of cellulose makes it recalcitrant to hydrolysis into its individual sugar subunits for biofuels production. Moreover, ionic liquids are considered as green solvents and have been used for biomass solubilization. The present work describes three properties: Kamlet-Taft (K-T) parameters, viscosity and surface tension of five imidazolium-based ionic liquids (ILs); namely [C(2)mim][OAc], [C(4)mim][OAc], [C(2)mim][Cl], [C(4)mim][Cl] and [C(4)mims][BF4], and their efficiency in the cellulose structural transformation for improved enzymatic glucose recovery. Crystalline cellulose was treated with ILs at two different temperatures, i.e. 100 and 130 degrees C for 5 and 2 h, respectively, with 10% solid loading followed by enzymatic saccharification using 10 and 20 FPU/g substrate of commercial cellulases. ILs treatment of crystalline cellulose significantly reduces the crystallinity, which resulted in a very sharp increase of sugar yields after enzymatic saccharification. Cellulose treated for 130 degrees C/2 h resulted in better glucose yields as compared to 100 degrees C/5 h. ILs comprising acetate anion resulted in highest glucose yields and chloride based ILs performed moderately, whereas BF4- based IL was ineffective in transforming the cellulose structure. In order to decipher the possible reasons of varying efficiency of these ILs, the K-T parameters; hydrogen bond acidity (alpha), hydrogen bond basicity (beta), solvent polarizability (pi*), kinematic viscosity (eta) and surface tension (sigma) were calculated for 100 and 130 degrees C. These results show that, among all the properties of ILs, hydrogen bond basicity (beta) is relatively more important than kinematic viscosity and surface tension for impacting the structural transformation and subsequent enzymatic hydrolysis. [C(2)mim][OAc] with high beta value (1.32) and lower viscosity (4.4 cSt/s) and surface tension (30.3 mN/m) was found to be most efficient in cellulose transformation resulting in higher glucose yields (89.8%) upon saccharification. Effect of size of cation and anion of ILs and properties of regenerated cellulose is also examined by PXRD and FT-IR to further support the findings. (C) 2015 Elsevier Ltd. All rights reserved.

Novel acid catalysts for alkane isomerization were synthesized with silica alumina supported heteropolyoxometallets by wet incipient method. Two series of catalysts were prepared by dispersing TPA or MPA. Characterization of catalysts was done by BET and TPD methods. Objective was to find high surface and acidity catalysts and to see the effect of synthesis parameter as loading or impregnation time on catalyst physicochemical properties as surface area, pore size, pore volume and acidity of HPA based oxide Seralox-5. TPA or MPA loading affected acidity and pore volume of catalysts, however no effect of impregnation time has been revealed. Surface area of catalysts was found in the range of 154–198 m2/g and acidity 10.1–17.7 ml/g of NH3 at STP. Among all the catalysts optimum characteristic catalysts were found from both the series, selecting one from each. These two catalysts exhibit high surface area, mesopore structure and high acidity.

This study presents preparation of a novel, cost effective and recyclable catalyst from natural waste for production of biodiesel. Novel catalyst composition has been developed using combination of seashell and eggshell in complexation with transition metal oxide TiO2 to form A-B-O type metal oxide complex, where A is alkaline metal and B is transition metal. Catalyst composition has been evaluated and a robust cost effective method for biodiesel production is proposed.

The production and use of biodiesel has seen a quantum jump in the recent past due to benefits associated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants producing biodiesel by transesterification of vegetable oils and fats based on base catalyzed (caustic) homogeneous transesterification of oils. However, homogeneous process needs steps of glycerol separation, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodiesel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The present report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel production. This review shall help in selection of suitable catalysts and the optimum conditions for biodiesel production.