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In this study, we propose a complete biomass fractionation strategy where all three major biopolymers, namely, cellulose, hemicellulose, and lignin, are separated with higher efficiency and purity....

In this study, we report on the synthesis and evaluation of a sodium, magnesium, and aluminum (Na-Mg-Al) layered double hydroxide (LDH) based sorbent for hydrogen chloride (HCl) removal at concentrations found in lignocellulosic biomass derived syngas. The LDH was synthesized by a spontaneous self-assembly method and further calcined at 700 °C to produce a mixed metal oxide sorbent that we evaluated in the hot gas cleanup of hydrogen chloride at 100 parts per million. The performance of this sorbent was evaluated in a fixed bed reactor from 400 to 600 °C against that of a commercial magnesium and aluminum LDH (ComLDH) material that does not contain sodium in the matrix as well as two other commercial sorbents, sodium carbonate (Na2CO3) and sodium aluminate (NaAlO2). Our Na-Mg-Al LDH is thermally stable in the hot gas cleanup temperature range. During fixed bed experiments, our calcined LDH mixed metal oxide was effective in reducing hydrogen chloride’s concentration below the breakthrough concentration of 1 ppm from 400 to 600 °C for more than 14 h. The better performance of our calcined LDH compared to calcined commercial LDH supported our hypothesis that sodium incorporation in the LDH matrix enhances HCl sorption. Based on comparison against the commercial Na-based sorbents, the following rankings by temperature observed: LDH > NaAlO2 > Na2CO3 at 400 °C; LDH = NaAlO2 > Na2CO3 at 500 °C; and Na2CO3 = NaAlO2 = LDH at 600 °C.

The objective of this research was to investigate the presence of residual lignin in cellulose fibers on the efficiency and energy consumption during nanofibers processing. Four kinds of lignin-containing cellulose nanofibers (LCNFs) from switchgrass, yellow poplar, hybrid poplar, and pine, respectively, were isolated via organosolv fractionation coupling mechanical grinding. Nanofibrils were observed after organosolv fractionation. The details of their morphological features, chemical structures, water retention value (WRV), and thermal degradation characteristics were revealed and compared. Mean diameters of nanofibers separated from switchgrass, yellow poplar, hybrid poplar, and pine were 27.9 nm, 25.4 nm, 24.6 nm, and 21.5 nm, respectively. The presence of lignin for the four types of LCNFs led to a decrease in energy consumption and an increase in WRV, among which pine nanofibers show the best with an average energy consumption of 0.511 kWh/kg and a WRV of 537%. It was also demonstrated that increasing lignin content for LCNFs could contribute to the sample’s thermal stability. In conclusion, exact benefits of residual lignin for nanofiber will facilitate its preparation process and extend its application.

Production of nanocellulosic materials from loblolly pine (Pinus taeda) kraft pulp provides an opportunity to diversify the portfolio of traditional pulp and paper industries. In this study, pinewood was first subjected to dilute acid pre-extraction with 0.5% sulfuric acid in order to fractionate the hemicellulose, followed by kraft pulping and elemental chlorine free bleaching in order to obtain up to 97% pure cellulose fractions. CNCs (cellulose nanocrystals) were prepared by hydrolyzing the bleached kraft pulp with 64% sulfuric acid at 45 °C for 30 min; the resultant unhydrolyzed solid residues were homogenized using a microfluidizer in order to produce cellulose nanofibers (CNFs). The dilute acid pre-extraction step resulted in complete hydrolysis of galactan and arabinan from pinewood, as well as in partial removal of mannan (80%) and xylan (58%). As a result of pre-extraction, the CNC yield and crystallinity improved by 44% and 11%, respectively, from the corresponding kraft pulps. CNCs produced from the pre-extracted materials also exhibited 16% reduction in particle size, but a 70% increase in sulfur content as well as 20% increase in zeta potential. Higher purity of kraft pulps resulted in higher exposure of cellulose crystalline domains to sulfuric acid thereby resulting in the observed changes. Thus, pulp purity was found to play a significant role in determining the quantity and quality of nanocellulosic materials derived from loblolly pine.

Ionic liquids (ILs) can be used to sustainably convert lignocellulosic feedstocks into renewable bio-based materials and chemicals. To improve the prospects of commercialization, it is essential to investigate the fate of lignocellulosic biomass during IL-based processing and develop tools for designing and optimizing this “green” technology. In situ characterization during pretreatment and dissolution processes have shown that ILs reduced the inherent recalcitrance of lignocellulosic biomass via swelling of cellulose bundles and formation of fissures in the secondary cell wall layers. It subsequently enhanced the penetration of ILs into the plant cell wall leading to depolymerization and solubilization of matrix polysaccharides, mainly hemicellulose via deacetylation. Lignin also underwent dehydration or reduction reactions, depending on the IL type, with different mechanisms leading to the cleavage of inter-unit linkages. Following this process, the accessibility to cellulose microfibrils increased and induced delamination. Complementary X-ray diffraction analyses have elucidated that ILs also reduced cellulose crystallinity and altered cellulose polymorphs. High throughput in situ analyses, namely bright-field optical microscopy, nuclear magnetic resonance and Fourier transform infrared spectroscopies, have aided in monitoring the degree of swelling and chemical structural changes in lignocellulosic biomass during IL-based processing. Development of novel in situ analytical tools like IL-based gel permeation chromatography and rheometry will further shed light on molecular level changes in lignocellulose. Thus, an overall understanding of physico-chemical changes underwent by lignocellulosic biomass will help develop tools for monitoring and improving IL-based engineering of renewable materials and chemicals.

Biomass processing industries and modern society are both interested in environmentally friendly plant-based polymers, such as lignin, to replace petrochemical derivatives. In this study, an n-buta...

Huanglongbing (HLB), also known as citrus greening, is a bacterial disease that poses a devastating threat to the citrus industry worldwide. To manage this disease efficiently, we developed and characterized a ternary aqueous solution (TSOL) that contains zinc nitrate, urea, and hydrogen peroxide. We report that TSOL exhibits better antimicrobial activity than commercial bactericides for growers. X-ray fluorescence analysis demonstrates that zinc is delivered to citrus leaves, where the bacteria reside. FTIR and Raman spectroscopy, molecular dynamics simulations, and density functional theory calculations elucidate the solution structure of TSOL and reveal a water-mediated interaction between Zn2+ and H2O2, which may facilitate the generation of highly reactive hydroxyl radicals contributing to superior antimicrobial activity of TSOL. Our results not only suggest TSOL as a potent antimicrobial agent to suppress bacterial growth in HLB-infected trees, but also provide a structure-property relationship that explains the superior performance of TSOL.

Fast pyrolysis of pine wood was carried out to yield a liquid bio-oil mixture that was separated into organic and aqueous phases. The organic phase (ORG-bio-oil) was characterized by gas chromatography–mass spectroscopy, 31P-nuclear magnetic resonance spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. It was further used as a raw material for producing a mixture of biphenolic compounds (ORG-biphenol). ORG-bio-oil, ORG-biphenol, and bisphenol-A were reacted with cyanogen bromide to yield cyanate ester monomers. Cyanate esters were characterized using FTIR spectroscopy and were thermally cross-linked to develop thermoset materials. Thermomechanical properties of cross-linked cyanate esters were assessed using dynamic mechanical analysis and compared with those of cross-linked bisphenol-A-based cyanate ester. ORG-biphenol cyanate ester was observed to have a superior glass transition temperature (350–380°C) as compared to bisphenol-A cyanate ester (190–220°C). Cyanate esters derived from bio-oil have the potential to be a sustainable alternative to the bisphenol-A-derived analog.

The recalcitrance bottleneck of lignocellulosic materials presents a major challenge for biorefineries, including second-generation biofuel production. Because of their abundance in the northern hemisphere, softwoods, such as Norway spruce, are of major interest as a potential feedstock for biorefineries. In nature, softwoods are primarily degraded by basidiomycetous fungi causing brown rot. These fungi employ a non-enzymatic oxidative system to depolymerize wood cell wall components prior to depolymerization by a limited set of hydrolytic and oxidative enzymes. Here, it is shown that Norway spruce pretreated with two species of brown-rot fungi yielded more than 250% increase in glucose release when treated with a commercial enzyme cocktail and that there is a good correlation between mass loss and the degree of digestibility. A series of experiments was performed aimed at mimicking the brown-rot pretreatment, using a modified version of the Fenton reaction. A small increase in digestibility after pretreatment was shown where the aim was to generate reactive oxygen species within the wood cell wall matrix. Further experiments were performed to assess the possibility of performing pretreatment and saccharification in a single system, and the results indicated the need for a complete separation of oxidative pretreatment and saccharification. A more severe pretreatment was also completed, which interestingly did not yield a more digestible material. It was concluded that a biomimicking approach to pretreatment of softwoods using brown-rot fungal mechanisms is possible, but that there are additional factors of the system that need to be known and optimized before serious advances can be made to compete with already existing pretreatment methods.

Hemicellulose, a structural polysaccharide and often underutilized co-product stream of biorefineries, could be used to produce prebiotic ingredients with novel functionalities. Since hot water pre-extraction is a cost-effective strategy for integrated biorefineries to partially fractionate hemicellulose and improve feedstock quality and performance for downstream operations, the approach was applied to process switchgrass (SG), hybrid poplar (HP), and southern pine (SP) biomass at 160°C for 60 min. As a result, different hemicellulose-rich fractions were generated and the chemical characterization studies showed that they were composed of 76–91% of glucan, xylan, galactan, arabinan, and mannan oligosaccharides. The hot water extracts also contained minor concentrations of monomeric sugars (≤18%), phenolic components (≤1%), and other degradation products (≤3%), but were tested for probiotic activity without any purification. When subjected to batch fermentations by individual cultures of Lactobacillus casei, Bifidobacterium bifidum, and Bacteroides fragilis, the hemicellulosic hydrolysates elicited varied responses. SG hydrolysates induced the highest cell count in L. casei at 8.6 log10 cells/ml, whereas the highest cell counts for B. fragilis and B. bifidum were obtained with southern pine (5.8 log10 cells/ml) and HP hydrolysates (6.4 log10 cells/ml), respectively. The observed differences were attributed to the preferential consumption of mannooligosaccharides in SP hydrolysates by B. fragilis. Lactobacillus casei preferentially consumed xylooligosaccharides in the switchgrass and southern pine hydrolysates, whereas B. bifidum consumed galactose in the hybrid poplar hydrolysates. Thus, this study (1) reveals the potential to produce prebiotic ingredients from biorefinery-relevant lignocellulosic biomass, and (2) demonstrates how the chemical composition of hemicellulose-derived sources could regulate the viability and selective proliferation of probiotic microorganisms.

The wide-scale production of renewable fuels from lignocellulosic feedstocks continues to be hampered by the natural recalcitrance of biomass. Therefore, there is a need to develop robust and reliable methods to characterize and quantify components that contribute to this recalcitrance. In this study, we utilized a method that incorporates pyrolysis with successive gas chromatography and mass spectrometry (Py-GC/MS) to assess lignification in cell suspension cultures. This method was compared with other standard techniques such as acid-catalyzed hydrolysis, acetyl bromide lignin determination, and nitrobenzene oxidation for quantification of cell wall bound phenolic compounds. We found that Py-GC/MS can be conducted with about 250 µg of tissue sample and provides biologically relevant data, which constitutes a substantial advantage when compared to the 50–300 mg of tissue needed for the other methods. We show that when combined with multivariate statistical analyses, Py-GC/MS can distinguish cell wall components of switchgrass (Panicum virgatum) suspension cultures before and after inducing lignification. The deposition of lignin precursors on uninduced cell walls included predominantly guaiacyl-based units, 71% ferulic acid, and 5.3% p-coumaric acid. Formation of the primary and partial secondary cell wall was supported by the respective ~15× and ~1.7× increases in syringyl-based and guaiacyl-based precursors, respectively, in the induced cells. Ferulic acid was decreased by half after induction. These results provide the proof-of-concept for quick and reliable cell wall compositional analyses using Py-GC/MS and could be targeted for either translational genomics or for fundamental studies focused on understanding the molecular and physiological mechanisms regulating plant cell wall production and biomass recalcitrance.

Materials generated from renewable resources are promising and attractive substitutes for petroleum-based materials. Recently, regeneration of cellulose fibers using ionic liquids (ILs) as green solvents has been a topic of interest to both industrial and academic sectors. However, extraction of cellulose from lignocellulosic biomass requires numerous energy intensive processing steps. Additionally, the deconstruction and removal of lignin and hemicellulose components from lignocellulosic biomass usually involve corrosive pretreatment and the solvation of specific biomass components. Instead, utilization of the whole biomass—particularly woody residues—to manufacture high-performance materials offers an attractive value-proposition. In this study, we demonstrated fiber regeneration of whole hybrid poplar (HP) biomass by a sustainable method. We developed an environmentally friendly approach by partially auto-hydrolyzing the biomass with water before its dissolution in 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) ionic liquid, for large-scale, roll-to-roll production of fibers by solution spinning. We report, for the first time, a fundamental understanding of the inter- and intramolecular interactions in HP biomass–IL solutions, as well as their corresponding spinnability, structural reformation, and mechanical performance of the regenerated fibers. Particularly, the molecular alignment, recrystallization, and crystallinity of the spun fibers were correlated to the chain entanglement, molecular relaxation, and rheological properties of the HP biomass–IL solutions. A window of entangled concentration (4–6.5 wt%) of biomass in the IL was determined to be favorable for fiber spinning.

The water–gas shift (WGS) reaction is an attractive process for producing hydrogen gas from lignocellulosic biomass conversion applications. The goal of this study was to investigate hydrogen production via the WGS reaction using carbon monoxide (CO), one of the significant non-condensable gases formed during biomass fast pyrolysis, as reactant over the range of the intermediate-temperature shift (ITS). WGS reaction is typically carried out as a low-temperature shift (LTS;150–300 °C) or a high-temperature shift (HTS; 300–500 °C) with each shift using a different catalyst. In this study, the WGS was conducted at an intermediate temperature range (200–400 °C) relevant to lignocellulosic biomass fast pyrolysis hydrodeoxygenation over a copper (Cu) based catalyst in a CO-lean environment (70 vol% steam, 20 vol% He, and 10 vol% CO). The experimental temperatures were tested over three different weight hourly space velocities (WHSV = 1220, 2040, and 6110 cm3 g−1 min−1). CO conversion increased with increasing temperature and catalyst weight, with a maximum CO conversion of 94% achieved for temperatures greater than 300 °C. We evaluated four models including two mechanistic Langmuir–Hinshelwood (LH) models, one redox mechanistic model, and one reduced order model (ROM). The first (LH1) and second (LH2) Langmuir–Hinshelwood models differ by the intermediate formed on the catalyst surface. LH1 forms product complexes while LH2 produces a formate complex intermediate. LH2 best described our experimental kinetic data, based on statistical and regression analysis, and provided apparent activation energies between 60 and 80 kJ mol−1 at different space velocities. Furthermore, the ROM fit the experimental data well and, due to its simplicity, has potential for incorporation into computationally expensive simulations for similar experimental conditions.

This study aims to optimize strong acid hydrolysis-based production of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) from pre-extracted and fully bleached kraft pulp of loblolly pinewood, the most abundant and commercially significant softwood species in southeastern United States. The effect of four parameters, including acid concentration, temperature, duration and pulp particle size, on the yield and properties of CNCs was investigated using the central composite design (CCD) of response surface methodology (RSM) for process optimization. While CNC yield was significantly affected by acid concentration and hydrolysis temperature and was adequately explained by an empirical model, none of the characteristic properties of CNCs, including crystallinity index, surface charge and particle size, displayed any strong correlation to the process parameters within the experimental ranges tested. At different hydrolysis severities, we not only analyzed the waste streams to determine the extent of holocellulose degradation, but also evaluated the properties of leftover partially hydrolyzed pulp, called cellulosic solid residues (CSR), to gauge its potential for CNF production via mechanical fibrillation. Conditions that maximized CNC yields (60% w/w) were 60% acid concentration, 58 °C, 60 min and 40 mesh particle size. Twenty percent (w/w) of the pulp was degraded under these conditions. On the other hand, conditions that maximized CSR yields (60% w/w) were 54% acid, 45 °C, 90 min and 20 mesh particle size, which also produced 15% CNCs, caused minimal pulp degradation (

Recurring outbreaks linked to Escherichia coli O157:H7-contaminated lettuce and Salmonella enterica-contaminated sprouts highlight the need for improved food safety measures. The aim of this study was to determine the ability of a bio-based antimicrobial extract prepared from switchgrass, a dedicated energy crop, to reduce E. coli O157:H7 and S. Typhimurium populations on Formica coupons, a model food-contact surface. Overnight cultures of ~7 log CFU/mL E. coli O157:H7 and S. Typhimurium, air-dried on Formica coupons were treated with 0.625% NaClO, 70% ethanol, sterile water or different batches of switchgrass extractives (SE1, SE2, and SE3) for up to 30 min. E. coli O157:H7 was reduced by 4.43 log CFU/mL after 1 min by SE3, and to non-detectable levels after 1 min by all other treatments. Populations of S. Typhimurium LT2 (15-min drying) were reduced by 3.30 log CFU/mL with 70% ethanol, 5.38 log CFU/mL with SE1, and to non-detectable levels with 0.625% NaClO after 1 min, while S. Typhimurium ATCC 23564 (1-h drying) was non-detectable after 1 min by all treatments. Under soiled conditions, 10-min treatment with SE1 and 70% ethanol reduced both bacteria to non-detectable levels. Studies with concentrated switchgrass extractives combined with various other natural disinfectants or in hurdle approaches warrant further investigation.

Development of cross-linked, soft polymeric materials from biomass has been a focus of research. The aqueous phase of biomass pyrolysis oil (bio-oil) has been used as a precursor for monomer synthe...

A statistical response surface methodology (RSM) using a central composite design (CCD) model was applied to identify the optimum thermal desorption conditions for maximum recovery of preservative from copper naphthenate (CuNap) treated wood and subsequent production of a high quality pyrolytic vapor from the thermally treated wood. From the designed experiment, 94% of the total preservative present in the ties was desorbed at temperatures higher than 250 °C and residence times longer than 30 min. Elevating the temperature from 215 °C to 285 °C for 45 min residence time generated a weight loss of 12–36 wt%, an increase in higher heating value (HHV) from 20.1 to 21.9 MJ/kg, and a reduction of energy yield from 90.4 to 71.5% of the resulting thermally treated biomass. Pyrolysis at 450 °C of this material produced a vapor rich in sugars- and lignin-derived compounds. The predicted optimum conditions in terms of a maximum preservative recovery, minimum energy yield loss of the wood, and production of thermally treated biomass that generates a high proportion of sugars- and lignin-derived compounds during pyrolysis were found to be 265 °C and 51 min. Under these optimum conditions, the predicted maximum preservative recovery was 95% while the predicted thermally treated solid retained 77% of the original energy yield and produced high portions of levoglucosan and lignin-derived compounds during subsequent pyrolysis, similar to torrefied wood.

The effects of hot water extraction on the removal of inorganic impurities (N, S, Na, K, Mg and Ca) in biomass that are detrimental to gasification were investigated on switchgrass and loblolly pine bark. As hot water extraction severity increased from 13 to 141 h °C, the extraction liquor pH decreased from 6.0 to 4.5 for switchgrass and 3.6 to 3.1 for pine bark, thus resulting in 20.7–69.6% of ash reduction for switchgrass and 57.0–73.3% for pine bark, respectively. In addition, the nitrogen content which results in ammonia (NH3) formation was reduced by 9.3–22.9% for switchgrass and 1.0–6.8% for pine bark following increment of severity. Furthermore, sulfur which leads to hydrogen sulfide (H2S) formation was reduced from 48.3 to 62.5% and 5.6 to 17.3% for switchgrass and pine bark, respectively. The range of potassium, sodium, magnesium and calcium reductions were 94.9–98.8, 47.9–72.4, 58.7–83.5 and 8.5–13.0 for switchgrass and 50.8–67.5, 29.2–60.1, 9.7–50.8 and 3.3–33.0% for pine bark. Finally, statistical analysis was carried out on the statistical significance of the extraction temperature and time as well as their interaction on the removal of inorganic impurities. The extraction temperature, time, and the interaction differed in their effect on liquor pH, ash reduction, mass loss, and reduction of individual inorganics.

Synthesizing lignin-based copolymers would valorize a major coproduct stream from pulp and paper mills and biorefineries as well as reduce the dependence on petrochemical-based consumer goods. In this study, we used organosolv lignin isolated from hybrid poplar ( Populus trichocarpa × P. deltoides) to generate lignin-containing methacrylate hydrogels. The copolymer hydrogels were synthesized by first grafting 2-hydroxyethyl methacrylate (HEMA) onto lignin (OSLH) via esterification and then by free radical polymerization of OSLH with excess HEMA. The copolymer hydrogels were prepared with different stoichiometric ratios of OSLH (e.g., 0, 10, 20, and 40 wt %) with respect to HEMA. Copolymerization with OSLH led to an increase in cross-linking density, which in turn enhanced the hydrogel's material properties; we report up to 39% improvement in water retention, 20% increase in thermostability, and up to a 3 order increase in magnitude of the storage modulus ( G'). The copolymer's properties, such as water retention and glass transition temperature, could be tuned by altering the percent functionalization of lignin OH groups and the ratio of OSLH to HEMA.

© 2017 Elsevier B.V. In this work, FeB, NiB, and FeNiB nanomaterials were examined as catalysts for catalytic transfer hydrogenolysis (CTH) using supercritical ethanol (sc-EtOH) as the hydrogen donor and reaction solvent. The earth-abundant alloys were synthesized using simple aqueous chemical reductions and characterized using ICP-OES, XRD, and STEM-EDS. Using acetophenone to model the desired catalytic reactivity, FeNiB was identified as having superior reactivity (74% conversion) and selectivity for complete deoxygenation to ethylbenzene (84%) when compared to the monometallic materials. Given its high reactivity and selectivity for deoxygenation over ring saturation, FeNiB was screened as a lignin valorization catalyst. FeNiB mediates deoxygenation of aliphatic hydroxyl and carbonyls in organosolv lignin via CTH in sc-EtOH. A combination of gel permeation chromatography, GC/MS, and NMR spectroscopy was used to demonstrate the production of a slate of monomeric phenols with intact deoxygenated aliphatic side chains. In total, these results highlight the utility of CTH for the valorization of biorefinery-relevant lignin using an inexpensive, earth-abundant catalyst material and a green solvent system that can be directly derived from the polysaccharide fraction of lignocellulosic biomass.

The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIM]Acetate) has been widely used for biomass processing, i.e., to pretreat, activate, or fractionate lignocellulosic biomass to produce soluble sugars and lignin. However, this IL does not achieve high biomass solubility, therefore minimizing the efficiency of biomass processing. In this study, [EMIM]Acetate and three other ILs composed of different 3-methylimidazolium cations and carboxylate anions ([EMIM]Formate, 1-allyl-3-methylimidazolium ([AMIM]) formate, and [AMIM]Acetate) were analyzed to relate their physicochemical properties to their biomass solubility performance. While all four ILs are able to dissolve hybrid poplar under fairly mild process conditions (80 °C and 100 RPM stirring), [AMIM]Formate and [AMIM]Acetate have particularly increased biomass solubility of 40 and 32%, respectively, relative to [EMIM]Acetate. Molecular dynamics simulations suggest that strong interactions between IL and specific plant biopolymers may contribute to this enhanced solubilization, as the calculated second virial coefficients between ILs and hemicellullose are most favorable for [AMIM]Formate, matching the trend of the experimental solubility measurements. The simulations also reveal that the interactions between the ILs and hemicellulose are an important factor in determining the overall biomass solubility, whereas lignin-IL interactions were not found to vary significantly, consistent with literature. The combined experimental and simulation studies identify [AMIM]Formate as an efficient biomass solvent and explain its efficacy, suggesting a new approach to rationally select ionic liquid solvents for lignocellulosic deconstruction.

The sorption/desorption of gallic acid, a simple phenolic compound, was studied experimentally in a batch system. The motivation for this project was to provide insight into the recovery of phenolic compounds from switchgrass. Recovery of phenolic compounds could enhance the sustainability and economics of biorefining facilities. The sorption/desorption of gallic acid was shown to be qualitatively similar to that of phenolics extracted from switchgrass; so more extensive studies were made using gallic acid as a surrogate for the complex mixtures of phenolic compounds leached from switchgrass. The kinetics indicate that an approximation of equilibrium was reached within 48 h. Activated carbon was demonstrated to sorb gallic acid and phenolics from water and aqueous switchgrass leachate. The loading capacity of activated carbon for the gallic acid–water-activated carbon system increased with temperature for 20 to 60 °C. Ethanol was shown to be a preferable elution agent for desorbing gallic acid from activa...

In this study, the results from laboratory measurements of the devolatilization kinetics of switchgrass in a rapidly heated fixed bed reactor flushed with argon and operated at constant temperatures between 600 and 800°C was reported. Results indicate that switchgrass decomposes in two sequential stages during pyrolysis: stage I involves the evaporation and devolatilization of water and extractives and stage II involves that of hemicellulose, cellulose, and lignin. The estimated global activation energy for stage II increased from 52.80 to 59.39kJ/mol as the reactor temperature was increased from 600 to 800°C. The maximum conversion of carbon, hydrogen, oxygen, sulfur, and nitrogen ranged from 0.68 to 0.70, 0.90 to 0.95, 0.88 to 0.91, 0.70 to 0.80, and 0.55 to 0.66, respectively. The retention of alkali and alkaline earth metal (AAEM) species in the solid char after complete pyrolysis was significantly higher than in the original feed, indicating the importance of AAEM species in subsequent char processing.

A two-step thermochemical process combining a thermal desorption at 250–300 °C and a pyrolysis at 500 °C of used creosote-treated wooden railroad ties was carried out to recover preservative and produce a high quality bio-oil and biochar. Under optimal temperature between 280 and 300 °C, high preservative removal efficiency (70–74%) was achieved with a high proportion of polycyclic aromatic hydrocarbons (PAHs, 80–82%) and a large portion of the original wood mass (67–70%) was retained. This thermally treated biomass had higher heating value (HHV; 19.9–20 MJ/kg) than the starting material. The physical properties of the preservative, such as viscosity and density, and its toxic threshold against a common decay basidiomycete fungus were similar to those of commercially available P2-creosote. Pyrolysis of the thermally treated ties produced bio-oils with lower water content and total acid numbers, and a higher amount of lignin-derived compounds than that of untreated ties. Biochars derived from the thermally...

Reforming whole lignocellulosic biomass into value-added materials has yet to be achieved mainly due to the infusible nature of biomass and its recalcitrance to dissolve in common organic solvents. Recently, the solubility of biomass in ionic liquids (ILs) has been explored to develop all-lignocellulosic materials; however, efficient dissolution and therefore production of value-added materials with desired mechanical properties remain a challenge. This article presents an approach to producing high-performance lignocellulosic films from hybrid poplar wood. An autohydrolysis step that removes ≤50% of the hemicellulose fraction is performed to enhance biomass solvation in 1-ethyl-3-methyl imidazolium acetate ([C2mim][OAc]). The resulting biomass–IL solution is then cast into free-standing films using different coagulating solvents, yet preserving the polymeric nature of the biomass constituents. Methanol coagulated films exhibit a cocontinuous 3D-network structure with dispersed domains of less than 100 nm...

© 2017 American Chemical Society. We have prepared composite materials of hexagonal nickel phosphide and molybdenum carbide (Mo2C) utilizing a simple and scalable two-stage synthesis method composed of carbothermic reduction followed by hydrothermal incubation. We observe the monophasic hexagonal phosphide Ni2P in the composite at low phosphide-to-carbide (P:C) ratios. Upon an increase in the proportion of P:C, the carbide surface becomes saturated, and we detect the emergence of a second hexagonal nickel phosphide phase (Ni5P4) upon annealing. We demonstrate that vapor-phase upgrading (VPU) of whole biomass via catalytic fast pyrolysis is achievable using the composite material as a catalyst, and we monitor the resulting product slates using pyrolysis-gas chromatography/mass spectrometry. Our analysis of the product vapors indicates that variation of the P:C molar ratio in the composite material affords product slates of varying complexity and composition, which is indicated by the number of products and their relative proportions in the product slate. Our results demonstrate that targeted vapor product composition can be obtained, which can potentially be utilized for tuning of the composition of the bio-oil downstream.

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Phosphides and carbides are among the most promising families of materials based on earth-abundant elements for renewable energy conversion and storage technologies such as electrochemical water splitting, batteries, and capacitors. Nickel phosphide and molybdenum carbide in particular have been extensively investigated for electrochemical water splitting. However, a composite of the two compounds has not been explored. Here, we demonstrate preferential deposition of nickel phosphide on molybdenum carbide in the presence of carbon by using a hydrothermal synthesis method. We employ the hydrogen evolution reaction in acid and base to analyze the catalytic activity of phosphide-deposited carbide. The composite material also shows superior electrochemical stability in comparison to unsupported phosphide. We anticipate that the enhanced electrochemical activity and stability of carbide deposited with phosphide will stimulate investigations into the preparation of other carbide–phosphide composite materials.

Development of commercially relevant bioenergy switchgrass cultivars requires reducing recalcitrance for bioprocessing without compromising biomass yield. Low-lignin transgenic switchgrass has been produced via down-regulation of caffeic acid O-methyltransferase (COMT), a lignin biosynthetic enzyme, or by over-expression of the MYB4 transcription factor, a repressor of the lignin biosynthetic pathway. The aim of this study was to evaluate parents and selected hybrids obtained from COMT and MYB4 hybrid families under field conditions for agronomic performance and biomass quality. Plant height, width, number of tillers, dry weight, cell wall composition including lignin content, and sugar release were measured after the establishment year (2014) and the second growing season (2015). For COMT hybrids, biomass yield of the transgenic hybrids was similar to or greater than the wild-type parents selected for high biomass. Lignin content of COMT transgenic hybrids was reduced by 10%, S/G ratio decreased by 27%, and sugar release increased between 20% and 44% compared to their wild-type parents. These results indicate that hybridization of COMT with a high-yielding locally selected genotype resulted in both improved agronomic performance and enhanced biomass quality in the offspring. On the other hand, the MYB transgenic hybrid showed a 10% reduction in biomass yield compared with its wild-type parent in year 1, but not in year 2. The lignin S/G ratio was not reduced in MYB transgenic hybrids, nor was sugar release increased. These data indicate that the MYB transgene may not be suitable for an agronomic setting. More testing is needed of transgenic and wild-type, high-biomass selections for use as breeding parents. These results show that combining low-lignin transgenic switchgrass with a breeding and selection program for biomass yield will allow for the deployment of effective transgenes in high-yielding genetic backgrounds.

© 2019 American Chemical Society. Mixed-metal oxides possess a wide range of tunability and show promise for catalytic stabilization of biomass pyrolysis products. For materials derived from layered double hydroxides, understanding the effect of divalent cation species and divalent/trivalent cation stoichiometric ratio on catalytic behavior is critical to their successful implementation. In this study, four mixed-metal oxide catalysts consisting of Al, Zn, and Mg in different stoichiometric ratios were synthesized and tested for ex-situ catalytic fast pyrolysis (CFP) using pine wood as feedstock. The catalytic activity and deactivation behavior of these catalysts were monitored in real-time using a lab-scale pyrolysis reactor and fixed catalyst bed coupled with a molecular beam mass spectrometer (MBMS), and data were analyzed by multivariate statistical approaches. In the comparison between Mg-Al and Zn-Al catalyst materials, we demonstrated that the Mg-Al materials possessed greater quantities of basic sites, which we attributed to their higher surface areas, and they produced upgraded pyrolysis vapors which contained less acids and more deoxygenated aromatic hydrocarbons such as toluene and xylene. However, detrimental impacts on carbon yields were realized via decarbonylation and decarboxylation reactions and coke formation. Given that the primary goals of catalytic upgrading of bio-oil are deoxygenation, reduction of acidity, and high carbon yield, these results highlight both promising catalytic effects of mixed-metal oxide materials and opportunities for improvement.

Inorganic elements present in lignocellulosic biomass and introduced during harvesting and handling of the feedstock negatively affect biomass conversion to fuels and products. In particular, alkali and alkaline earth metals act as catalysts during thermochemical conversion, contribute to reactor degradation, and decrease the yield and quality of the reaction products. In this study, we investigated an approach to reduce ash content of switchgrass. Several reagents (chelating agents ethylenediaminetetraacetic acid (EDTA) and citric acid, as well as acetic acid, sulfuric acid, and water) under various extraction times (5, 10, 15, and 20 min) were tested using a microwave-assisted extraction method. After the extraction, mass loss, total ash, individual inorganics, and concentration of sugars in the hydrolyzates were measured. EDTA afforded the highest inorganics removal, with near complete extraction of alkali and alkaline earth metals K, Ca, and Mg, and high removal of S and Si. Citric acid and sulfuric acid removed similarly high amounts of K, Ca, and Mg as EDTA, but less Mg, P, S, and Fe. Additionally, extraction with water resulted in near complete removal of K; however, more modest removal of other inorganics was observed compared to other treatments. The mass loss was significantly higher in the sulfuric acid extractions due to hydrolysis of the structural carbohydrates, while EDTA resulted in little carbohydrate degradation due to the more neutral pH conditions. This study illustrated the benefits of extracting with chelating agents, as opposed to mineral acids, to remove inorganics and improve biomass quality.

While previous studies have shown that white-rot fungal pretreatment reduces the severity of chemical pretreatments and improves enzymatic saccharification yields, very few have investigated the synergistic effects of fungal pretreatment combined with organosolv pretreatment on lignin recovery and quality. In this study, loblolly pine chips were incubated with Trametes versicolor for 15, 30 and 45 days, prior to organosolv pretreatment and enzymatic saccharification. Fungal pretreatment for 15 days improved the saccharification yield by 23%, and higher amounts (56%) of lignin-enriched fractions were obtained. Fungal pretreatment for 45 days led to extensive depolymerization, structural modification and enrichment of lignin in the organosolv precipitates (OP). Characterization of the OP fraction showed that samples pretreated for 30 and 45 days contained higher amounts of hydroxyl groups and p-hydroxyphenyl (H) subunits, and showed increases in depolymerization of carbohydrates as well as decreases in G/H lignin ratio. It became apparent that further investigations are needed to explore the benefits of combining fungal and organosolv pretreatments for improving lignin yields from softwoods.

The aim of this work was to evaluate the efficiency of an ionic liquid (IL) 1-butyl-3-methylimidazolium acetate ([C4mim][OAc]) pretreatment (110°C for 30min) in comparison to high severity autohydrolysis pretreatment in terms of delignification, cellulose crystallinity and enzymatic digestibility. The increase in severity of autohydrolysis pretreatment had positive effect on glucan digestibility, but was limited by the crystallinity of cellulose. [C4mim][OAc] pretreated sugarcane bagasse exhibited a substantial decrease in lignin content, reduced cellulose crystallinity, and enhanced glucan and xylan digestibility. Glucan and xylan digestibility was determined as 97.4% and 98.6% from [C4mim][OAc] pretreated bagasse, and 62.1% and 57.5% from the bagasse autohydrolyzed at 205°C for 6min, respectively. The results indicated the improved digestibility and hydrolysis rates after [C4mim][OAc] pretreatment when compared against a comparable autohydrolyzed biomass.

Used creosote-treated wood ties were thermally treated between 250 and 350 °C to recover preservative and upgrade the wood to provide an improved quality biomass for thermochemical processes. With thermal treatments ranging from 250 to 300 °C, the amounts of creosote, mostly consisting of polycyclic aromatic hydrocarbons (PAHs), recovered were from 47 to 79% of total creosote present in the used ties. Thermal treatment at 350 °C recovered 97% of total PAH compounds. Larger amounts of PAHs with higher molecular weights (HMWs) and lower vapor pressures (LVP) were recovered at elevated temperatures. Temperature above 300 °C decomposed the wood matrix, with a mass loss ranging between 50 and 63 wt% and produced large amounts of light organics, anhydrosugars, and phenolic compounds that would contaminate the recovered creosote. Our study concluded that thermal treatment ranging between 275 and 300 °C would be preferred to recover preservative for recycling and improve the wood quality, i.e., high carbon content and caloric value, and low hazardous pollutants (creosote residues) for thermochemical processes such as pyrolysis or gasification. These findings suggest that the proposed approach could be a commercially viable and environmentally beneficial alternative to landfill for used railroad ties.

We present an investigation related to catalytic upgrading of cellulose pyrolysis vapors using mixed-metal oxide catalysts derived from layered double hydroxide precursors. We performed principal component analysis on the pyrolysis-gas chromatography/mass spectrometry data to elucidate changes in the product slate between noncatalytic fast pyrolysis, catalytic pyrolysis using the oxides of magnesium, aluminum, and zinc, and catalytic pyrolysis using our synthesized mixed-metal oxides containing the same cations. Our investigations demonstrate that the mixed-metal species behave differently than even a physical mixture of their monometal counterparts, and that they are capable of producing more furanic compounds by fast pyrolysis of cellulose. We also demonstrate that the metal ratio and identity in these catalysts impart different selectivities to the resulting product slates. Taken together, these data establish the utility of the mixed-metal oxide catalysts in producing a liquid product with low oxygen ...

The purpose of this study was to determine the effects of three particle sizes of feedstock and two types of novel bale wraps on the quality of switchgrass by monitoring the chemical changes in cellulose, hemicellulose, lignin, extractives, and ash over a 225-day period. Using NIR (Near-infrared) modeling to predict the chemical composition of the treated biomass, differences were found in cellulose, lignin, and ash content across switchgrass bales with different particle sizes. Enclosing bales in a net and film impacted the cellulose, lignin, and ash content. Cellulose, hemicellulose, lignin, extractives, and ash were different across the 225-day storage period. A quadratic response function made better prediction about cellulose, lignin, and ash response to storage, and a linear response function best described hemicellulose and extractives response to storage. This study yields valuable information regarding the quality of switchgrass at different intervals between the start and end date of storage, which is important to conversion facilities when determining optimal storage strategies to improve quality of the biomass feedstock, based on potential output yield of a bale over time.

The vapors produced from pine wood using an intermediate auger pyrolysis process under various sweeping gas flow rates were condensed by three temperature-controlled condensers and analyzed. Increasing sweeping gas flow rate from 20 to 40 L/min did not change the yield of the pyrolysis products, however, noticeable changes were found in the bio-oil composition, such as a decrease in water content and an increase of amount of organic compounds. Increasing sweeping gas flow rate influenced the bio-oil fractionation in each temperature-controlled condenser with a reduction in bio-oil yield in the first condenser controlled between 85 and 90 °C and outgoing vapor temperature of 121 °C. There were no changes in the second condenser maintained at 45⿿50 °C and outgoing vapor temperature of 107 °C, and an increase in the third condenser regulated at 10⿿15 °C and outgoing vapor temperature of 25 °C. Higher sweeping gas flow rates also resulted in changing the bio-oil composition in the first and second condensers including a reduction in water content and an increase in viscosity and density, suggesting that refining this fraction as an intermediate source would be a more efficiency way to produce fuels and chemicals than treating the whole bio-oil. The bio-oil from the third condenser contained elevated water content, acidity and light oxygenated compounds with increasing sweeping gas flow rate, suggesting that this fraction would be more suitable as an energy source for hydrogen production via microbial electrolysis processes. In summary, the sweeping gas flow rate used for pyrolysis with an intermediate auger reactor is an important factor to change bio-oil properties in temperature-controlled multistage condensation processes.

As interest in soil organic carbon (SOC) dynamics increases, so do needs for rapid, accurate, and inexpensive methods for quantifying SOC. Objectives were to i) evaluate near infrared reflectance (NIR) spectroscopy potential to determine SOC and soil organic matter (SOM) in soils from across Tennessee, USA; and ii) evaluate potential upper limits of SOC from forest, pasture, no-tillage, and conventional tilled sites. Samples were analyzed via dry-combustion (SOC), Walkley–Black chemical SOM, and NIR. In addition, the sample particle size was classified to give five surface roughness levels to determine effects of particle size on NIR. Partial least squares regression was used to develop a model for predicting SOC as measured by NIR by comparing against SOM and SOC. Both NIR and SOM correlated well (R2 > 0.9) with SOC (combustion). NIR is therefore considered a sufficiently accurate method for quantifying SOC in soils of Tennessee, with pasture and forested systems having the greatest accumulations...

A two-step thermal process, an initial thermal treatment at mild temperature followed by a fast pyrolysis step, was investigated to recover wood preservatives and produce preservatives-free wood for production of high quality bio-oil from used creosote-treated railroad ties. During the initial thermal treatment at temperature of 280 °C for 10–30 min, the treated wood ties underwent a 20–25% weight loss with energy yield (77–83%). Energy yield at 280 °C was lower than that at 200 and 250 °C (92–97%) but higher than that at the 300 °C (64–74%). Recovery level of creosote at 280 °C was comparable to that at 300 °C. Fast pyrolysis at 450 °C of the 280 °C-treated wood ties produced high amount of levoglucosan and phenolic compounds with a traceable amount (1.7–1.9% of the total peak area) of creosote compounds.

Non-structural components, such as inorganics and organic extractives, present in switchgrass were extracted with water and ethanol, and the resulting non-structural components-free materials were pyrolyzed to investigate the effect of the inorganic species on the pyrolytic products. The extraction was performed for switchgrass materials harvested from three consecutive growing seasons, removing 8.5 wt% of the organic extractives in the first season biomass, and 5.8 and 6.3 wt% in the second and third season, respectively, on total dry basis of biomass. In addition to organic extractives, from 0.7 to 2.7 wt% of ash were extracted. Specifically, 99% and 59% of total K and Mg were removed from the switchgrass harvested in the second and third growing season. Thermogravimetric analysis demonstrated that a predominant reduction of K and Mg content in the biomass increased temperature at which mass loss rate is maximized in the decomposition of cellulose, hemicellulose, and lignin. The reduction of K and Mg content also affected pyrolytic products generated at 450°C. The chromatographic peak area percentage of levoglucosan from the extracted samples in the second and third growing season was two to three times higher than that from the extracted samples in the first growing season, showing a strong negative correlation with K and Mg content, whereas most of the light oxygenated and furanic/pyranic/cyclopentanic products exhibited a strong positive correlation with K and Mg content. We concluded that the removal of non-structural components prior to thermochemical conversion processes such pyrolysis can potentially produce a valuable extractives stream while removing catalytic inorganics that negatively impact downstream pyrolysis process.

Background Lignocellulosic biomass requires either pretreatment and/or fractionation to recover its individual components for further use as intermediate building blocks for producing fuels, chemicals, and products. Numerous ionic liquids (ILs) have been investigated for biomass pretreatment or fractionation due to their ability to activate lignocellulosic biomass, thereby reducing biomass recalcitrance with minimal impact on its structural components. In this work, we studied and compared 1-allyl-3-methylimidazolium formate ([AMIM][HCOO]) to the commonly used 1-ethyl-3-methylimidazolium acetate ([EMIM][CH3COO]) for its potential to activate hybrid poplar biomass and enable high cellulose and hemicellulose enzymatic conversion. Although [EMIM][CH3COO] has been widely used for activation, [AMIM][HCOO] was recently identified to achieve higher biomass solubility, with an increase of 40% over [EMIM][CH3COO]. Results Since IL activation is essentially an early stage of IL dissolution, we assessed the recalcitrance of [EMIM][CH3COO] and [AMIM][HCOO]-activated biomass through a suite of analytical tools. More specifically, Fourier transform infrared spectroscopy and X-ray diffraction showed that activation using [AMIM][HCOO] does not deacetylate hybrid poplar as readily as [EMIM][CH3COO] and preserves the crystallinity of the cellulose fraction, respectively. This was supported by scanning electron microscopy and enzymatic saccharification experiments in which [EMIM][CH3COO]-activated biomass yielded almost twice the cellulose and hemicellulose conversion as compared to [AMIM][HCOO]-activated biomass. Conclusion We conclude that the IL [AMIM][HCOO] is better suited for biomass dissolution and direct product formation, whereas [EMIM][CH3COO] remains the better IL for biomass activation and fractionation.

An abundant, low-cost, and high-quality supply of lignocellulosic feedstock is necessary to realize the large-scale implementation of biomass conversion technologies capable of producing renewable fuels, chemicals, and products. Barriers to this goal include the variability in the chemical and physical properties of available biomass, and the seasonal and geographic availability of biomass. Blending several different types of biomass to produce consistent feedstocks offers a solution to these problems and allows for control over the specifications of the feedstocks. For thermochemical conversion processes, attributes of interest include carbon content, total ash, specific inorganics, density, particle size, and moisture content. In this work, a series of switchgrass and pine residues blends with varying physical and chemical properties were evaluated. Physical and chemical properties of the pure and blended materials were measured, including compositional analysis, elemental analysis, compressibility, flowability, density, and particle size distribution. To screen blends for thermochemical conversion behavior, the analytical technique, pyrolysis gas chromatography mass spectrometry (Py-GC/MS), was used to analyze the vapor-phase pyrolysis products of the various switchgrass/pine residues blends. The py-GC/MS findings were validated by investigating the bio-oils produced from the selected blends using a lab-scale fluidized-bed pyrolysis reactor system. Results indicate that the physical properties of blended materials are proportional to the blend ratio of pure feedstocks. In addition, pyrolysis of pine residues resulted in bio-oils with higher carbon content and lower oxygen content, while switchgrass derived pyrolysis products contained relatively greater amount of anhydrosugars and organic acids. The distribution of the pyrolysis vapors and isolated bio-oils appear to be a simple linear combination of the two feedstocks. The concentration of alkali and alkaline earth metals (Ca, K, Mg, and Na) in the blended feedstocks were confirmed to be a critical parameter due to their negative effects on the bio-oil yield. This work demonstrates that blending different sources of biomass can be an effective strategy to produce a consistent feedstock for thermochemical conversion.

Switchgrass (Panicum virgatum L.) is a leading lignocellulosic bioenergy feedstock. Cellulose is a major component of the plant cell walls and the primary substrate for saccharification. Accessibility of cellulose to enzymatic breakdown into fermentable sugars is limited by the presence of lignin in the plant cell wall. In this study, putatively novel switchgrass secondary cell wall cellulose synthase PvCesA4 and primary cell wall PvCesA6 genes were identified and their functional role in cellulose synthesis and cell wall composition was examined by overexpression and knockdown of the individual genes in switchgrass. The endogenous expression of PvCesA4 and PvCesA6 genes varied among including roots, leaves, stem, and reproductive tissues. Increasing or decreasing PvCesA4 and PvCesA6 expression to extreme levels in the transgenic lines resulted in decreased biomass production. PvCesA6-overexpressing lines had reduced lignin content and syringyl/guaiacyl lignin monomer ratio accompanied by increased sugar release efficiency, suggesting an impact of PvCesA6 expression levels on lignin biosynthesis. Cellulose content and cellulose crystallinity were decreased, while xylan content was increased in PvCesA4 and PvCesA6 overexpression or knockdown lines. The increase in xylan content suggests that the amount of non-cellulosic cell wall polysaccharide was modified in these plants., possibly as a compensation response to the decreased cellulose content; the result would be maintenance of cell wall integrity. The results suggest an interconnection between the cellular machinery controlling cellulose and xylan biosynthesis. Taken together, the results show that the manipulation of the cellulose synthase genes alters the cell wall composition and availability of cellulose as a bioprocessing substrate. Understanding the enzymes responsible for the synthesis and regulation of cellulose synthesis is key to engineering biofuel crops for cellulose production and more efficient extraction of glucose from cellulose.

Organosolv fractionation is a promising pathway to separate cellulosic biomass into high purity cellulose, hemicelluloses, and lignin. This work specifically investigates the properties of lignins isolated at specific time points as fractionation progressed, with the intent of correlating fractionation time with lignin purity, yield, thermal and chemical properties. Yellow poplar (Liriodendron tulipifera) was fractionated using a mixture of methyl isobutyl ketone, ethanol, and water with sulfuric acid as catalyst at 140 °C over a two-hour period. Aliquots of the liquor were collected by sampling every 15 min during the fractionation to generate a series of lignins. The results showed that with increased fractionation time, lignin purity improved from 90.3 to 94.6% and the glass transition temperature increased from 117 to 137 °C. The loss of aliphatic OH and increase of phenolic OH with fractionation time led to an increase in condensed structures and increased polydispersity at times greater than 90 min. Principal component analysis of Fourier transform infrared spectroscopic data confirmed the shift to higher purity and more condensed chemical structures with increasing fractionation time. Overall, this study demonstrates that thermal and chemical properties of lignin change with the organosolv fractionation time.

A new approach to hydrogen production using an integrated pyrolysis–microbial electrolysis process is described. The aqueous stream generated during pyrolysis of switchgrass was used as a substrate for hydrogen production in a microbial electrolysis cell, achieving a maximum hydrogen production rate of 4.3 L H2/L anode-day at a loading of 10 g COD/L-anode-day. Hydrogen yields ranged from 50 ± 3.2% to 76 ± 0.5% while anode Coulombic efficiency ranged from 54 ± 6.5% to 96 ± 0.21%, respectively. Significant conversion of furfural, organic acids and phenolic molecules was observed under both batch and continuous conditions. The electrical and overall energy efficiency ranged from 149–175% and 48–63%, respectively. The results demonstrate the potential of the pyrolysis–microbial electrolysis process as a sustainable and efficient route for production of renewable hydrogen with significant implications for hydrocarbon production from biomass.

Ionic liquids (ILs) are benign solvents that are highly effective for biomass pretreatment. However, their applications for scale-up biorefinery are limited due to multiple expensive IL recovery and separation steps that are required. To overcome this limitation, it is very critical to develop a compatible enzymatic and microbial biocatalyst system to carry the simultaneous saccharification and fermentation in IL environments (SSF-IL). While enzymatic biocatalysts have been demonstrated to be compatible with various IL environments, it is challenging to develop microbial biocatalysts that can thrive and perform efficient biotransformation under the same conditions (pH and temperature). In this study, we harnessed the robust metabolism of Yarrowia lipolytica as a microbial platform highly compatible with the IL environments such as 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). We optimized the enzymatic and microbial biocatalyst system using commercial cellulases and demonstrated the capability of Y. lipolytica to convert cellulose into high-value organics such as α-ketoglutaric acid (KGA) in the SSF-IL process at relatively low temperature 28 °C and high pH 6.3. We showed that SSF-IL not only enhanced the enzymatic saccharification but also produced KGA up to 92 % of the maximum theoretical yield.

The anatomical and chemical characteristics of sweetgum were studied after 11 years of elevated CO2 (544 ppm, ambient at 391 ppm) exposure. Anatomically, branch xylem cells were larger for elevated CO2 trees, and the cell wall thickness was thinner. Chemically, elevated CO2 exposure did not impact the structural components of the stem wood, but non-structural components were significantly affected. Principal component analysis (PCA) was employed to detect differences between the CO2 treatments by considering numerous structural and chemical variables, as well as tree size, and data from previously published sources (i.e., root biomass, production and turnover). The PCA results indicated a clear separation between trees exposed to ambient and elevated CO2 conditions. Correlation loadings plots of the PCA revealed that stem structural components, ash, Ca, Mg, total phenolics, root biomass, production and turnover were the major responses that contribute to the separation between the elevated and ambient CO2 treated trees.

The success of the biorefinery will depend on deriving value from the lignin fraction of lignocellulosic feedstocks. Thus, it will be necessary to develop procedures that provide a separate and usable lignin stream for chemical transformation. A wide range of processes have been developed that afford isolated lignin, but very few of these methods are practical for the biorefinery, as they target lignin analysis or lignin removal, and are largely impractical for large scale use or introduce severe structural changes in the lignin that significantly reduces its potential as a chemical feedstock. This chapter will introduce several methods that isolate lignin for analytical purposes, or for its removal from lignocellulose. The majority of the chapter then discusses processes for biomass fractionation – methodology that gives lignin streams in high yield and purity, and which offer potential utility within the biorefinery.