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CO 2 is the main pollutant in biogas, reducing its calorific value. Among various technological methods to eliminate carbon dioxide from biogas, membrane separation technology stands out for large-scale industrial biogas purification due to its advantages. The selection of membrane material and preparation process are key factors in membrane separation technology. In this study, a premixing process was initially used to blend different masses of packed molecular sieves TS-1 (or ZSM-5) and cellulose derivatives (ethyl cellulose, cellulose acetate) separately. These mixtures were then coated onto porous PVDF substrates using a coating process to create various bilayer hybrid composite membranes. Among these, PVDF/EC-ZSM-5 (containing 15 % ZSM-5) bilayer hybrid composite membrane is the most fitting. For CO 2 /CH 4 gas mixtures, the gas selectivity of this membrane surpassed Robeson's 1991 standard line (the CO 2 permeability was 597.48 Barrer, and the CO 2 /CH 4 selectivity was 9.14). Overall, this composite membrane, made for the first time from PVDF, ZSM-5, and EC, is expected to be a promising CO 2 selective separation membrane material for biogas purification in large-scale industrial processes due to its simple production process., Competing Interests: Declaration of competing interest The authors report no declarations of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Treating hazardous landfill leachate poses significant environmental challenges due to its complex nature. In this study, we propose a novel approach for enhancing the anaerobic digestion of landfill leachate using silver nanoparticles (Ag NPs) conjugated with eco-friendly green silica nanoparticles (Si NPs). The synthesized Si NPs and Ag@Si NPs were characterized using various analytical techniques, including transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The anaerobic digestion performance of Si NPs and Ag@Si NPs was tested by treating landfill leachate samples with 50 mg/L of each NP. The results demonstrated an enhancement in the biogas production rate compared to the control phase without the nanocomposite, as the biogas production increased by 14% and 37% using Si NPs and Ag@Si NPs. Ag@Si NPs effectively promoted the degradation of organic pollutants in the leachate, regarding chemical oxygen demand (COD) and volatile solids (VS) by 58% and 65%. Furthermore, microbial analysis revealed that Ag@Si NPs enhanced the activity of microbial species responsible for the methanogenic process. Overall, incorporating AgNPs conjugated with eco-friendly green Si NPs represents a sustainable and efficient approach for enhancing the anaerobic digestion of landfill leachate., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The increasing depletion of oil resources and the environmental problems caused by using much fossil energy in the rapid development of society. The bio-oil becomes a promising alternative energy source to fossil. However, bio-oil cannot be directly utilized, owing to its high proportion of oxygenated compounds with low calorific value and poor thermal stability. Catalytic hydrodeoxygenation (HDO) is one of the most effective methods for refining oxygenated compounds from bio-oil. HDO catalysts play a crucial role in the HDO reaction. This review emphasizes the description of the main processing of HDO and various catalytic systems for bio-oil, including noble/non-noble metal catalysts, porous organic polymer catalysts, and polar solvents. A discussion based on recent studies and evaluations of different catalytic materials and mechanisms is considered. Finally, the challenges and future opportunities for the development of catalytic hydrodeoxygenation for bio-oil upgradation are looked forward., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Biodiesel is a typical renewable energy and the previous transesterification processes for biodiesel production mainly focus on thermocatalytic methods. In this paper, the ball-milling process was investigated into the biodiesel production under Kraft lignin activated carbon stabilized K 2 CO 3 . Biodiesel yield increased to 66 % after only 5 min and reached 100 % within 25 min under optimal ball-milling conditions (0.5 g of the catalyst; methanol/oil molar ratio 18:1; 195 g of ball-mill beads; 1400 rpm; 25 °C). The power demand between the thermocatalytic method and the ball-milling method was also compared. Based on the computation, the ball-milling method has lower power demand than the traditional method (38 vs 201 kWh·mol -1 ). Therefore, the ball-milling method is an effective and economical process for biodiesel production., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Lignocellulose can be converted into biofuel or functional materials to achieve high value-added utilization. Biomass utilization process is complex and multi-dimensional. This paper focuses on the biomass conversion reaction conditions, the preparation of biomass-based functional materials, the combination of biomass conversion and traditional wet chemistry, molecular simulation and process simulation. This paper analyzes the mechanism, advantages and disadvantages of important machine learning (ML) methods. The application examples of ML in different aspects of high value utilization of lignocellulose are summarized in detail. The challenges and future prospects of ML in this field are analyzed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Agricultural waste residues (agro-waste) are the source of carbohydrates that generally go in vain or remain unused despite their interesting morphological, chemical, and mechanical properties. With rapid urbanization, there is a need to valorize this waste due to limited non-renewable resources. Utilizing agro-waste also prevents the problems like burning and inefficient disposal that otherwise lead to immense pollution worldwide. In addition, conversion of biomass to value-added products like earthen cups, weaving baskets, and bricks is equally beneficial for the rural population as it provides secondary income, creates jobs, and improves rural people's lifestyles. This review paper will discuss an overview of different applications utilizing agro-waste residues. In particular, agro-wastes used as construction material, bio-fertilizers, pulp and paper products, packaging products, tableware, heating applications, biocomposites, nano-cellulosic materials, soil stabilizers, bioplastics, fire-retardant additive, dye removal, and biofuels will be summarized. Finally, several commercially available agro-waste products will also be discussed, emphasizing the circular economy., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

From energy perspective, with abundant polysaccharides (45-85%), the renewable lignocellulosic is recognized as the 2nd generation feedstock for bioethanol and bio-based products production. Enzymatic hydrolysis is a critical pathway to yield fermentable monosaccharides from pretreated substrates of lignocellulose. Nevertheless, the lignin presence in lignocellulosic substrates leads to the low substrate enzymatic digestibility ascribed to the nonproductive adsorption. It has been reported that the water-soluble lignin (low molecular weight, sulfonated/sulfomethylated and graft polymer) enhance the rate of enzymatic digestibility, however, the catalytic mechanism of lignin-enzyme interaction remains elusive. In this review, optimization strategies for enzymatic hydrolysis based on the lignin structural modification, enzyme engineering, and different additives are critically reviewed. Lignin-enzyme interaction mechanism is also discussed (lignin and various cellulases). In addition, the mathematical models and simulation of lignin, cellulose and enzyme aims for promoting an integrated biomass-conversion process for sustainable production of value-added biofuels., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Members of the genus Populus (i.e., cottonwood, hybrid poplar) represent a promising source of lignocellulosic biomass for biofuels. However, one of the major factors negatively affecting poplar's efficient conversion to biofuel is the inherent recalcitrance to enzymatic saccharification due to cell wall components such as lignin. To this effect, there have been efforts to modify gene expression to reduce biomass recalcitrance by changing cell wall properties. Here, we review recent genetic modifications of poplar that led to change cell wall properties and the resulting effects on subsequent pretreatment efficacy and saccharification. Although genetic engineering's impacts on cell wall properties are not fully predictable, recent studies have shown promising improvement in the biological conversion of transgenic poplar to biofuels., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Waste biomass derived heterogeneous catalyst is an excellent alternative to chemically synthesized catalysts. In this work, calcined Tectona grandis leaves were proposed as an eco-friendly, renewable and low cost heterogeneous base catalyst. The prepared catalyst was examined by FTIR, XRD, XPS, SEM, EDX, TEM, TGA, BET and Hammett indicator test. The catalyst has an appealing nature towards various chemical transformations due to its basic surface sites provided by alkali and alkaline earth metals. The efficiency of the catalyst was successfully investigated by its application in biodiesel production. The products were confirmed by 1 H and 13 C NMR. 100% FAME conversion was attained using a catalyst loading of 2.5 wt% under optimized reaction parameters. The catalyst was further explored for Knoevenagel condensation reaction, in which it showed its effectiveness and recyclability towards the formation of benzylidenemalononitrile derivatives of aryl aldehydes. Thus, it is a potential 'green catalyst' derived from waste biomass without any addition of chemicals that can replace the industrial base catalysts used for biodiesel production and Knoevenagel reaction and makes the protocol environmentally benign., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Despite the enormous potential shown by recent biorefineries, the current bioeconomy still encounters multifaceted challenges. To develop a sustainable biorefinery in the future, multidisciplinary research will be essential to tackle technical difficulties. Herein, we leveraged a known plant genetic engineering approach that results in aldehyde-rich lignin via down-regulation of cinnamyl alcohol dehydrogenase ( CAD ) and disruption of monolignol biosynthesis. We also report on renewable deep eutectic solvents (DESs) synthesized from phenolic aldehydes that can be obtained from CAD mutant biomass. The transgenic Arabidopsis thaliana CAD mutant was pretreated with the DESs and showed a twofold increase in the yield of fermentable sugars compared with wild type (WT) upon enzymatic saccharification. Integrated use of low-recalcitrance engineered biomass, characterized by its aldehyde-type lignin subunits, in combination with a DES-based pretreatment, was found to be an effective approach for producing a high yield of sugars typically used for cellulosic biofuels and biobased chemicals. This study demonstrates that integration of renewable DES with plant genetic engineering is a promising strategy in developing a closed-loop process., Competing Interests: The authors declare no conflict of interest.

Culture contamination, end-product toxicity, and energy efficient product recovery are long-standing bioprocess challenges. To solve these problems, we propose a high-pressure fermentation strategy, coupled with in situ extraction using the abundant and renewable solvent supercritical carbon dioxide (scCO 2 ), which is also known for its broad microbial lethality. Towards this goal, we report the domestication and engineering of a scCO 2 -tolerant strain of Bacillus megaterium, previously isolated from formation waters from the McElmo Dome CO 2 field, to produce branched alcohols that have potential use as biofuels. After establishing induced-expression under scCO 2 , isobutanol production from 2-ketoisovalerate is observed with greater than 40% yield with co-produced isopentanol. Finally, we present a process model to compare the energy required for our process to other in situ extraction methods, such as gas stripping, finding scCO 2 extraction to be potentially competitive, if not superior.

Consolidated bioprocessing (CBP) by micro-organisms is desired for efficient conversion of lignocellulosic biomass to bioethanol fuels. Potential candidates have been discovered, including cellulolytic bacteria and filamentous fungi. Genetic and metabolic manipulation of these organisms further promotes their fermentation capacities and the ethanol tolerance. In addition, Saccharomyces cerevisiae and several other yeasts were genetically modified to express recombinant cellulases in media or display them on the cell surface for CBP of cellulose. To compensate the insufficient capacity of a single strain, various microbial consortia have also been developed. In this article, we reviewed the recent advances in CBP microbes and focused on the efforts in strain improvement employing genetic engineering.

To overcome the bottlenecks of high cost and low production yields that restrict the commercial production of microalgae biodiesel, the use of xylose was evaluate by Scenedesmus quadricauda FACHB-1297, which was shown to be capable of mixotrophic and heterotrophic growth and lipid production on xylose, rich in the waste streams from pulp and paper industry, with increases in lipid productivities of 35.8-fold (mixotrophic) and 9.2-fold (heterotrophic) in comparison to photoautotrophic lipid yields. Five doses of xylose were tested to determine the effects and mechanisms of the carbon source on microalgae in mixotrophic mode. At the optimal xylose dosage of 4 g/L, the highest lipid content (38.61%) and productivity (139.55 mg/L/d) were achieved besides maximum biomass productivity (361.4 mg/L/d), nutrient removal efficiency of 68.4% (nitrogen), 97.2% (phosphorus) and 35.2% (xylose). Those indicated that S. quadricauda FACHB-1297 was suitable for further development of using xylose from certain waste streams for biofuel production., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The thermal degradation behaviour and kinetic parameter of non-catalytic and catalytic pyrolysis of rice husk (RH) using rice hull ash (RHA) as catalyst were investigated using thermogravimetric analysis at four different heating rates of 10, 20, 50 and 100 K/min. Four different iso conversional kinetic models such as Kissinger, Friedman, Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) were applied in this study to calculate the activation energy (E A ) and pre-exponential value (A) of the system. The E A of non-catalytic and catalytic pyrolysis was found to be in the range of 152-190 kJ/mol and 146-153 kJ/mol, respectively. The results showed that the catalytic pyrolysis of RH had resulted in a lower E A as compared to non-catalytic pyrolysis of RH and other biomass in literature. Furthermore, the high Gibb's free energy obtained in RH implied that it has the potential to serve as a source of bioenergy production., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The pyrolysis behaviors of the three major organic components of eucalyptus alkaline peroxide mechanical pulping (APMP) spent liquor including alkali lignin (AL), lignin-carbohydrate complexes (LCC), and polysaccharide (PLS) were studied with emphasis on the effect and contributions of components on the overall pyrolysates of APMP spent liquor solid (ASLS). Profound differences on product properties from each component pyrolysis were illustrated. The results indicated that the bio-oil during ASLS pyrolysis was mainly attributed to AL, while the bio-gas and char were mostly affected by PLS. Small molecule hydrocarbons released during ASLS pyrolysis mainly came from AL and LCC, and CO and CO 2 mainly produced from PLS. As for bio-oils, AL generated the largest proportion of monomeric phenols and aromatic hydrocarbons (AHs), while PLS and LCC mainly contributed to the production of ketones, furans and acids. The correlation shown here is of interest for further studies on pulping spent liquor grading utilization., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A methane production system with continuous stirred-tank reactor, rumen liquid as inoculate microorganisms, and paper mill excess sludge (PES) as feedstock was studied. The work mainly focused on revealing the effect of feedstock concentration on the biogas production, which was seldom reported previously for the current system. The optimal fermentation conditions were found as follows: pH = 7, T = 39 ± 1 °C, sludge retention time is 20 days, sludge with total solids (TS) are 1, 2, 3.5, 5, 10, and 13% in weight. Daily gas yields were measured, and biogas compositions were analyzed by gas chromatograph. Under such conditions, the optimum input TS was 10 wt%, and the biogas yield and volume gas productivity were 280.2 mL/g·TS and 1188.4 mL L -1 ·d -1 , respectively. The proportions of CH 4 and CO 2 in the biogas were 65.1 and 34.2%. The CH 4 yield reached 182.7 mL/g VS (volatile suspended solid), which was higher than previously reported values. The findings of this work have a significant effect on promoting the application of digesting PES by rumen microorganisms and further identified the technical parameter.

The Cladophora glomerata (C. glomerata) is a kind of widely distributed macroalgae in the freshwater ecosystems. It primarily consists of carbohydrates that can be converted into biofuel by pyrolysis. In this study, thermogravimetric analysis (TGA) was used to investigate the thermal behavior and kinetics of C. glomerata during the pyrolysis process. The results showed that heating rates slightly affect the decomposition properties of C. glomerata; with the heating rates increasing, the maximum peak of weight loss rate shifted to higher temperatures. The activation energies of C. glomerata pyrolysis reaction were 244.25 and 238.07kJ/mol, respectively, as calculated by Friedman and Kissinger-Akahira-Sunose (KAS) methods. The pre-exponential factor and reaction order were determined by Coats-Redfern model, and applied to simulate the pyrolysis process of C. glomerata. The model calculated data and experimental data were consistent. This study could provide theoretical supports for designing C. glomerata conversion processes., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This paper critically reviews the impacts of supplementing trace elements on the anaerobic digestion performance. The in-depth knowledge of trace elements as micronutrients and metalloenzyme components justifies trace element supplementation into the anaerobic digestion system. Most of the earlier studies reported that trace elements addition at (sub)optimum dosages had positive impacts mainly longer term on digester stability with greater organic matter degradation, low volatile fatty acids (VFA) concentration and higher biogas production. However, these positive impacts and element requirements are not fully understood, they are explained on a case to case basis because of the great variance of the anaerobic digestion operation. Iron (Fe), nickel (Ni) and cobalt (Co) are the most studied and desirable elements. The right combination of multi-elements supplementation can have greater positive impact. This measure is highly recommended, especially for the mono-digestion of micronutrient-deficient substrates. The future research should consider the aspect of trace element bioavailability., (Copyright © 2016. Published by Elsevier Ltd.)

To understand the structural changes of lignin after soda-AQ and kraft pretreatment, milled straw lignin, black liquor lignin and residual lignin extracted from wheat straw were characterized by FT-IR, UV, GPC and NMR. The results showed that the main lignin linkages were β-aryl ether substructures (β-O-4'), followed by phenylcoumaran (β-5') and resinol (β-β') substructures, while minor content of spirodienone (β-1'), dibenzodioxocin (5-5') and α,β-diaryl ether linkages were detected as well. After pretreatment, most lignin inter-units and lignin-carbohydrate complex (LCC) linkages were degraded and dissolved in black liquor, with minor amount left in residual pretreated biomass. In addition, through quantitative (13)C and 2D-HSQC NMR spectral analysis, lignin and LCC were found to be more degraded after kraft pretreatment than soda-AQ pretreatment. Furthermore, the subsequent enzymatic hydrolysis results showed that more cellulose in wheat straw was converted to glucose after kraft pretreatment, indicating that LCC linkages were important in the enzymatic hydrolysis process., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Fines concentration harms paper machine runability and output quality in recovered paper processing, hence, their extraction would be fundamentally beneficial. In this study, separated fines from an industrial recycled fiber pulp (RFP) were characterized and evaluated for their potential biogas yields with a focus on understanding the role of varying lignin and ash contents. Further, these results were compared with biogas yields from conventional chemical and mechanical pulps. Overall, methane yields of fines from mechanical pulps (21-28mL/gVS) and RFP (127mL/gVS) are relatively low compared to the high methane yields of 375mL/gVS from the chemical pulp fines. However, it was shown that the high ash content in RFP fines (up to 50%) did not negatively influence overall yield, rather, it was the presence of slowly biodegrading lignin-rich fiber fines., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) was applied to poplar NE222 chips in a range of chemical loadings, temperatures, and times. The combined hydrolysis factor (CHF) as a pretreatment severity accurately predicted xylan dissolution by SPORL. Good correlations between CHF and pretreated solids enzymatic digestibility, sugar yield, and the formations of furfural and acetic acid were obtained. Therefore, CHF was used to balance sugar yield with the formation of fermentation inhibitors for high titer ethanol production without detoxification. The results indicated that optimal sugar yield can be achieved at CHF=3.1, however, fermentation using un-detoxified whole slurries of NE222 pretreated at different severities by SPORL indicated CHF≈2 produced best results. An ethanol titer of 41 g/L was achieved at total solids of approximately 20 wt% without detoxification with a low cellulase loading of 15 FPU/g glucan (27 mL/kg untreated wood)., (Published by Elsevier Ltd.)

This study investigated the thermal decomposition characteristics and pyrolytic products of anaerobic digested rice straw (ADRS) by thermogravimetric (TG) and pyrolysis-gas chromatograph/mass spectrometry (Py-GC/MS) analysis. Compared with the raw rice straw (RS), the thermal decomposition temperature of ADRS was shifted to higher temperature zone and the second decomposition zone of cellulose (Toffset(c)-Tpeak) became narrower (14 °C less), which indicated that the composition of rice straw were changed significantly by the anaerobic digestion pretreatment. Py-GC/MS analysis showed that the quality of the bio-oil and the selectivity of pyrolytic products could be obviously improved by anaerobic digestion. The total yields of alcohols, acids, aldehydes, furans, anhydrosugars, and ketones pyrolysis substances decreased, while the yield of phenols increased. The yield of 4-Vinylphenol (4-VP) increased from 29.33%, 8.21% and 5.76% to 34.93%, 12.46% and 7.68% at 330, 450 and 650 °C, respectively, after anaerobic digestion., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This study demonstrated at the pilot-scale (50 kg) use of Douglas-fir forest harvest residue, an underutilized forest biomass, for the production of high titer and high yield bioethanol using sulfite chemistry without solid-liquor separation and detoxification. Sulfite Pretreatment to Overcome the Recalcitrance of Lignocelluloses (SPORL) was directly applied to the ground forest harvest residue with no further mechanical size reduction, at a low temperature of 145°C and calcium bisulfite or total SO2 loadings of only 6.5 or 6.6 wt% on oven dry forest residue, respectively. The low temperature pretreatment facilitated high solids fermentation of the un-detoxified pretreated whole slurry. An ethanol yield of 282 L/tonne, equivalent to 70% theoretical, with a titer of 42 g/L was achieved. SPORL solubilized approximately 45% of the wood lignin as directly marketable lignosulfonate with properties equivalent to or better than a commercial lignosulfonate, important to improve the economics of biofuel production., (Published by Elsevier Ltd.)

Pretreatment of wheat straw with a combination of sodium carbonate (Na2CO3) or sodium hydroxide (NaOH) with oxygen (O2) 0.5MPa was evaluated for its delignification ability at relatively low temperature 110°C and for its effect on enzymatic hydrolysis efficiency. In the pretreatment, the increase of alkali charge (as Na2O) up to 12% for Na2CO3 and 6% for NaOH, respectively, resulted in enhancement of lignin removal, but did not significantly degrade cellulose and hemicellulose. When the pretreated solid was hydrolyzed with a mixture of cellulases and hemicellulases, the sugar yield increased rapidly with the lignin removal during the pretreatment. A total sugar yield based on dry matter of raw material, 63.8% for Na2CO3-O2 and 71.9% for NaOH-O2 was achieved under a cellulase loading of 20FPU/g-cellulose. The delignification efficiency and total sugar yield from enzymatic hydrolysis were comparable to the previously reported results at much higher temperature without oxygen., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Four fractions of one commercial sodium lignosulfonate (SXP) with different molecular weight (MW) and anionic polymers were studied to reduce non-productive adsorption of cellulase on bound lignin in a lignocellulosic substrate. SXP with higher MW had stronger blocking effect on non-productive adsorption of a commercial Trichoderma reesi cellulase cocktail (CTec2) on lignin measured by quartz crystal microgravimetry with dissipation monitoring. Linear anionic aromatic polymers have strong blocking effect, but they would also reduce CTec2 adsorption on cellulose to decrease the enzymatic activity. The copolymer of lignin and polyethylene glycol (AL-PEG1000) has strong enhancement in enzymatic hydrolysis of lignocelluloses, because it not only improves the cellulase activity to cellulose, but also blocks the non-productive cellulase adsorption on lignin. Apart from improving the cellulase activity to cellulose, the enhancements of enzymatic hydrolysis of lignocellulose by adding AL-PEG1000 and SXPs are the result of the decreased cellulase non-productive adsorption on lignin., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Furfural residues (FR), the abundant lignocellulosic residues from commercial furfural production, were delignified with alkaline peroxide process and then taken as substrates for ethanol production by simultaneous saccharification and fermentation (SSF). It was apparent that the delignification efficiency was increased with higher chemical addition and temperature, reaching the maximum removal (73.5%) of lignin. The widespread accessible-cellulose in FR favored the enzymatic hydrolysis and achieved the considerable bioconversion (75.7% with 5 FPU+10 IU/g substrate). The delignification process increased the relative glucose content and then the bioconversion efficiency, closely relating to the increased specific surface area. As the cellulose contents were higher than 60%, the final conversions conversely fell to around 75%, probably due to the insufficient utilization of all active cellulose with low enzyme cocktails addition. Although the SSF bioconversion slightly decreased as the elevated amount of fermentable cellulose, the maximum of ethanol concentration (16.9 g/L) was expectedly obtained., (Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.)

Municipal wastewater activated sludge contains a mixed microbial community, which can be manipulated to produce biocrude, a lipid feedstock for biodiesel production. In this study, the potential of biocrude production by activated sludge microorganisms grown in three different types of pulp and paper mill wastewaters was investigated. A 20% (v/v) activated sludge was inoculated into pulp and paper wastewater, supplemented with glucose (60 g/L) and nutrients (nitrogen and phosphorus) to obtain a high carbon to nitrogen ratio (70:1). The culture was incubated aerobically for seven days. The results showed that the activated sludge microorganisms were able to grow and accumulate lipids when cultivated in amended wastewaters. Microorganisms growing in anaerobic settling pond effluent water showed the highest lipid accumulation of up to 40.6% cell dry weight (CDW) after five days of cultivation compared with pulp wash wastewater (PuWW) (11.7% CDW) and mixed wastewater (MWW) (8.2% CDW) after seven days of cultivation. The lipids mostly contained C16-C18 fatty acids groups with oleic acid and palmitic acid being the dominant fatty acids. The maximum biodiesel yield was about 6-8% CDW for all the wastewaters. The results showed the potential of utilizing pulp and paper mill effluents and other waste streams, such as activated sludge for the sustainable production of lipids for biofuel production.

Woody biomass is renewable only if sustainable production is imposed. An optimum and sustainable biomass stand production rate is found to be one with the incremental growth rate at harvest equal to the average overall growth rate. Utilization of woody biomass leads to a sustainable economy. Woody biomass is comprised of at least four components: extractives, hemicellulose, lignin and cellulose. While extractives and hemicellulose are least resistant to chemical and thermal degradation, cellulose is most resistant to chemical, thermal, and biological attack. The difference or heterogeneity in reactivity leads to the recalcitrance of woody biomass at conversion. A selection of processes is presented together as a biorefinery based on incremental sequential deconstruction, fractionation/conversion of woody biomass to achieve efficient separation of major components. A preference is given to a biorefinery absent of pretreatment and detoxification process that produce waste byproducts. While numerous biorefinery approaches are known, a focused review on the integrated studies of water-based biorefinery processes is presented. Hot-water extraction is the first process step to extract value from woody biomass while improving the quality of the remaining solid material. This first step removes extractives and hemicellulose fractions from woody biomass. While extractives and hemicellulose are largely removed in the extraction liquor, cellulose and lignin largely remain in the residual woody structure. Xylo-oligomers, aromatics and acetic acid in the hardwood extract are the major components having the greatest potential value for development. Higher temperature and longer residence time lead to higher mass removal. While high temperature (>200°C) can lead to nearly total dissolution, the amount of sugars present in the extraction liquor decreases rapidly with temperature. Dilute acid hydrolysis of concentrated wood extracts renders the wood extract with monomeric sugars. At higher acid concentration and higher temperature the hydrolysis produced more xylose monomers in a comparatively shorter period of reaction time. Xylose is the most abundant monomeric sugar in the hydrolysate. The other comparatively small amounts of monomeric sugars include arabinose, glucose, rhamnose, mannose and galactose. Acetic acid, formic acid, furfural, HMF and other byproducts are inevitably generated during the acid hydrolysis process. Short reaction time is preferred for the hydrolysis of hot-water wood extracts. Acid hydrolysis presents a perfect opportunity for the removal or separation of aromatic materials from the wood extract/hydrolysate. The hot-water wood extract hydrolysate, after solid-removal, can be purified by Nano-membrane filtration to yield a fermentable sugar stream. Fermentation products such as ethanol can be produced from the sugar stream without a detoxification step., (Copyright © 2012 Elsevier Inc. All rights reserved.)

In this study, cornstalk was pretreated by an acid-chlorite delignification procedure to enhance the conversion of cornstalk to bio-oil in hot-compressed water liquefaction. The effects of the pretreatment conditions on the compositional and structural changes of the cornstalk and bio-oil yield were investigated. It was found that acid-chlorite pretreatment changed the main components and physical structures of cornstalk and effectively enhanced the bio-oil yield. Shorter residence time favored production of the total bio-oil products, whereas longer time led to cracking of the products. A high water loading was found to be favorable for high yields of total bio-oil and water-soluble oil. GC-MS analysis showed that the water-soluble oil and heavy oil were the complicated products of C(5-10) and C(8-11) organic compounds.

In this work, the potential of Acacia dealbata as raw material for ethanol production was evaluated, as well as its composition with regard to cellulose, hemicelluloses, lignin, extractives and ash. The tree samples were subjected to several dilute acid pretreatments using a combined severity parameter ranging from 0.7 to 3.7. The highest ethanol concentration obtained was 10.31 g ethanol/L within 24 h by using a separate hydrolysis and fermentation of the water insoluble fraction after pretreatment at 180 °C with 0.8% of sulfuric acid for 15 min. With simultaneous saccharification and fermentation, results obtained for the washed solids of water insoluble fraction were better than those obtained with the whole slurry., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Biofuels from lignocellulosic materials like wood are renewable and sustainable alternatives to petroleum and other fossil fuels. Wood can be grown and harvested without adding to the carbon load of the atmosphere and thus can be part of the solution to the problem posed by global climate changes. Recently much interest has developed on the concept of the forest product biorefinery, where wood is hydrolyzed prior to conventional pulping and papermaking processes and the hydrolyzate consisting of hemicellulose sugars are to be used as a feedstock for biofuels or bioplastics. The purification of the hydrolyzate stream and the separation of fermentable sugars from it thus constitutes an important step in biorefinery processes. The separation of particulate material from wood hydrolyzates is considered in this paper. Sugar maple hardwood was extracted with hot water at 160 degrees C. The extracts contain hemicelluloses (primarily xylooligomers, xylose and xylan), acetic acid and smaller amounts of lignin. The colloidal stability of the extracts plays a critical role in the separation and purification of the wood extracts. Here, we report the size and charge of the particles in the extract measured using standard instruments based on light scattering and microelectrophoresis. Particles were found to be in the size range from approximately 220nm to 270nm. Zeta potential measurements showed them to be negatively charged. By treating the extracts with a cationic flocculating agent poly-DADMAC, it was possible to preferentially precipitate out the colloidal fraction containing lignin and lignin derived compounds. Upon the addition of poly-DADMAC the turbidity of the suspension reduced from 920 NTU to 4 NTU in a 24 h period and particulates sedimented from the extract. The lignin concentration was reduced in the supernatant, while the sugar content remained unchanged. The addition of an indifferent electrolyte hindered the effectiveness of the polyelectrolyte. The optimum pH for the effectiveness of the polymer was found to be around 4.5. In order to accelerate the sedimentation of the particles, Kaolin was added to attach to the flocs after adding the polyelectrolyte. Kaolin helped accelerate the separation of the particulates by almost an order of magnitude. This work shows that flocculation with a cationic polyelectrolyte followed by separation by sedimentation, centrifugation or microfiltration can be an effective technique to purify biorefinery wood extracts.

The conversion of biomass to chemicals and energy is imperative to sustaining our way of life as known to us today. Fossil chemical and energy sources are traditionally regarded as wastes from a distant past. Petroleum, natural gas, and coal are not being regenerated in a sustainable manner. However, biomass sources such as algae, grasses, bushes and forests are continuously being replenished. Woody biomass represents the most abundant and available biomass source. Woody biomass is a reliably sustainable source of chemicals and energy that could be replenished at a rate consistent with our needs. The biorefinery is a concept describing the collection of processes used to convert biomass to chemicals and energy. Woody biomass presents more challenges than cereal grains for conversion to platform chemicals due to its stereochemical structures. Woody biomass can be thought of as comprised of at least four components: extractives, hemicellulose, lignin and cellulose. Each of these four components has a different degree of resistance to chemical, thermal and biological degradation. The biorefinery concept proposed at ESF (State University of New York - College of Environmental Science and Forestry) aims at incremental sequential deconstruction, fractionation/conversion of woody biomass to achieve efficient separation of major components. The emphasis of this work is on the kinetics of hot-water extraction, filling the gap in the fundamental understanding, linking engineering developments, and completing the first step in the biorefinery processes. This first step removes extractives and hemicellulose fractions from woody biomass. While extractives and hemicellulose are largely removed in the extraction liquor, cellulose and lignin largely remain in the residual woody structure. Xylo-oligomers and acetic acid in the extract are the major components having the greatest potential value for development. Extraction/hydrolysis involves at least 16 general reactions that could be divided into four categories: adsorption of proton onto woody biomass, hydrolysis reactions on the woody biomass surface, dissolution of soluble substances into the extraction liquor, and hydrolysis and dehydration decomposition in the extraction liquor. The extraction/hydrolysis rates are significantly simplified when the reactivity of all the intermonomer bonds are regarded as identical within each macromolecule, and the overall reactivity are identical for all the extractable macromolecules on the surface. A pseudo-first order extraction rate expression has been derived based on concentrations in monomer units. The reaction rate constant is however lower at the beginning of the extraction than that towards the end of the extraction. Furthermore, the H-factor and/or severity factor can be applied to lump the effects of temperature and residence time on the extraction process, at least for short times. This provides a means to control and optimize the performance of the extraction process effectively., (Copyright 2010 Elsevier Inc. All rights reserved.)

Hemicellulose is a potential by-product currently under-utilized in the papermaking industry. It is a hetero-carbohydrate polymer. For hardwood hemicelluloses, D-xylose is the major component upon depolymerization. At SUNY-ESF, wood extracts were obtained by extracting sugar maple wood chips with hot water at an elevated temperature. The wood extracts were then concentrated and acid hydrolyzed. Ethanologenic bacteria, E. coli FBR5, had a good performance in pure xylose medium for ethanol production. However, FBR5 was strongly inhibited in dilute sulfuric acid hydrolyzate of hot-water wood extract. FBR5 was challenged by hot-water wood extract hydrolyzate in this study. After repeated strain adaptation, an improved strain: E. coli FBHW was obtained. Fermentation experiments indicated that FBHW was resistant to the toxicity of hydrolyzate in the fermentation media of concentrated hydrolyzate, and xylose was completely utilized by the strain to produce ethanol. FBHW was grown in the concentrated hydrolyzate without any detoxification treatment and has yielded 36.8g/L ethanol., (Copyright 2010 Elsevier Inc. All rights reserved.)

This study investigated the effects of chemical pretreatment and disk-milling conditions on energy consumption for size-reduction and the efficiency of enzymatic cellulose saccharification of a softwood. Lodgepole pine wood chips produced from thinnings of a 100-year-old unmanaged forest were pretreated by hot-water, dilute-acid, and two SPORL processes (Sulfite Pretreatment to Overcome Recalcitrance of Lignocellulose) at acid charge on oven dry (od) wood of 0% and 2.21%. The pretreated wood chips were then milled using a laboratory disk mill under various solids-loadings and disk-plate gaps to produce substrates for enzymatic hydrolysis. We found that post-chemical-pretreatment size-reduction of forest biomass can decrease size-reduction energy consumption by 20-80% depending on the pretreatment applied under 20% solids-loading and a disk-plate gap of 0.76 mm in milling. SPORL with a sodium bisulfite charge of 8% and sulfuric acid charge of 2.21% on wood was the most effective in decreasing size-reduction energy consumption. Solids-loading had the most significant effect on disk-milling energy. When solids-loading was reduced from 30% to 3%, disk-milling energy could be decreased by more than a factor of 10 for wood chips pretreated by both SPORL and dilute-acid at an acid charge of 2.21%. The enzymatic hydrolysis glucose yields (EHGY) from the substrates produced by all pretreatments were independent of the solids-loading in milling, indicating that these energy savings in size-reduction can be realized without affecting EHGY. When wood chips were pretreated by SPORL with 2.21% acid charge, size-reduction energy consumption was decreased to less than 50 Wh/kg od wood at a practical solids-loading of approximately 10-20%, equivalent to that used in size-reduction of agriculture biomass, with excellent EHGY of about 370 g per kg od wood. Similar effects on size-reduction energy savings and excellent EHGY were also achieved when large disk-plate gaps (up to 1.52 mm studied) were applied in disk-milling of wood chips pretreated by SPORL with acid., (Published by Elsevier Ltd.)

A novel qualitative method has been developed for the determination of the various types of hydroxyl groups present in biodiesel production streams. The use of 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane as a phosphitylation reagent for quantitative (31)P NMR analysis of the hydroxyl groups in biodiesel process samples has been fully developed. This experimental protocol allows for rapid analysis of biodiesel mixtures of alcohols, fatty acids, glycerol, and mono- and disubstituted glycerides. Characteristic chemical shift ranges were developed with model compounds and used to fully characterize the conversion of triglyceride samples to biodiesel for two commercial production processes.