[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: The removal of phosphate from aqueous solution by biochar derived from switchgrass was investigated. Switchgrass-derived biochar was produced through fast pyrolysis at 450℃ and 800℃ and their physicochemical properties were determined. Batch adsorption experiments were performed to investigate the effect of contact time, initial pH, and ionic strength on the removal of phosphate by biochar. The results showed that the adsorption process was time dependant. The phosphate adsorption decreases as pH and electrolyte concentration increase. The removal of phosphate increased by increasing the production temperature. The pseudo second-order model fitted the data better than other mathematical models used to describe the adsorption kinetics of phosphate onto biochar. The adsorption equilibrium fitted well to both the Langmuir and Freundlich models. The characteristics of post-adsorption biochar were measured using XRD and FTIR. Based on the experimental results phosphate seem to be efficiently removed from solution by adsorbing onto MgO particles on the biochar surface. The results suggest that switchgrass-derived biochar pyrolized at higher temperature is an effective alternative inexpensive adsorbent, which can be used to reclaim phosphate from water or reduce phosphate leaching from fertilized soils.
International Annual Meeting American Society of Agronomy/ Crop Science Society of America/ Soil Science Society of America 2013; 11/2013
[Show abstract][Hide abstract] ABSTRACT: The miscibility of cellulose ester blends with varying degree of substitution (DS) of acetates along the chain backbone has been investigated using small-angle neutron scattering. The difference in degree of substitution (ΔDS) between the two components in the blend was systematically varied from 0.06 to 0.63 where each blend was found to be a partially miscible, two-phase system. Miscibility between the two components initially decreases as ΔDS of the blends increases. The Flory interaction parameter, χ, concurrently increases with increasing ΔDS as a result of diminishing van der Waals forces between components. The cellulose acetates with lower degree of substitution, which contain more hydroxyl substituents, however, demonstrate greater miscibility even at higher ΔDS. This is interpreted to be the result of favorable hydrogen bonding between blend components that are possible in the presence of more hydroxyl groups. FT-IR data support this interpretation, indicating an increase in hydrogen bonding in a blend having a lower DS component. These results indicate that while an increase in structural differences between cellulose acetate blend components limits miscibility, the presence of hydroxyl groups on the chain promotes mixing. This competition accentuates the significant impact specific interactions have on blend miscibility for these copolymers.
[Show abstract][Hide abstract] ABSTRACT: A group of biomass-derived lignins isolated using organosolv fractionation was characterized by FT-IR spectral and thermal property analysis coupled with multivariate analysis. The principal component analysis indicated that there were significant variations between the hardwood, softwood, and grass lignins due to the differences in syringyl and guaiacyl units as well as the different processing temperatures and times used to isolate the lignins. Partial least squares regression revealed that the concentration of syringyl units was the foremost factor behind the variation in glass transition temperature (Tg) for each lignin sample. It was concluded that structural variations resulting from alteringthe processing time and temperature and the lignin species directly affect the thermal properties of the lignin. Therefore, by determining the thermal properties of a lignin sample, a basic understanding of its structure can be developed.
[Show abstract][Hide abstract] ABSTRACT: Surface properties of switchgrass-derived biochars produced at fast pyrolysis temperatures of 450, 600 and 800°C were characterized at different solution pHs in order to determine the structural and chemical changes of artificially-weathered biochars when incorporated into soil. As biochars were acidified from pH 7 to 3, crystalline minerals dissolved slowly releasing nutrients; however, residual minerals were still detected in biochars produced at higher pyrolysis temperatures after pH treatment. Moreover, the amount of exchangeable bases and other inorganic compounds released from the biochars increased when pH decreased. As minerals dissolved from the biochars, total surface area and pore volume were found to increase. Surface functional groups and water vapor adsorption capacity at 0.8 P/P(o) also increased, whereas the potential CEC of biochars decreased due to the replacement of exchangeable sites by hydrogen ion. Therefore, during the aging process, it is predicted that soil-incorporated biochars will slowly release nutrients with changes in surface functionality and porosity, which are expected to enhance water holding capacity of soil and provide a beneficial habitat for microbial colonization.
[Show abstract][Hide abstract] ABSTRACT: Lignin, an abundant, naturally occurring biopolymer, is often considered “waste” and used as a simple fuel source in the paper-making process. However, lignin has emerged as a promising renewable resource for engineering materials, such as carbon fibers. Unfortunately, the molecular architecture of lignin (in vivo and extracted) is still elusive, with numerous conflicting reports in the literature, and knowledge of this structure is extremely important, not only for materials technologies, but also for production of biofuels such as cellulosic ethanol due to biomass recalcitrance. As such, the molecular structures of solvent-extracted (sulfur-free) lignins, which have been modified using various acyl chlorides, have been probed using small-angle X-ray (SAXS) and neutron (SANS) scattering in tetrahydrofuran (THF) solution along with hydrodynamic characterization using dilute solution viscometry and gel permeation chromatography (GPC) in THF. Mass spectrometry shows an absolute molecular weight ≈18–30 kDa (≈80–140 monomers), while GPC shows a relative molecular weight 3 kDa. A linear styrene oligomer (2.5 kDa) was also analyzed in THF using SANS. Results clearly show that lignin molecular architectures are somewhat rigid and complex, ranging from nanogels to hyperbranched macromolecules, not linear oligomers or physical assemblies of oligomers, which is consistent with previously proposed delignification (extraction) mechanisms. Future characterization using the methods discussed here can be used to guide extraction processes as well as genetic engineering technologies to convert lignin into value added materials with the potential for high positive impact on global sustainability.
[Show abstract][Hide abstract] ABSTRACT: Hygroscopicity, low durability, and low thermal resistance are disadvantages of lignocellulosic materials that also plague wood–plastic composites (WPCs). Hemicellulose is the most hydrophilic wood polymer and is currently considered as a sugar source for the bioethanol industry. The objective of this research is to extract hemicellulose from woody materials and enhance the properties of WPC by diminishing the hydrophilic character of wood. Hemicellulose of Southern Yellow Pine was extracted by hot-water at three different temperatures: 140, 155, and 170 °C. Wood flour was compounded with polypropylene in an extruder, both with and without a coupling agent. Injection molding was used to make tensile test samples. The thermal stability of wood flour was found to have increased after extraction. Extraction of hemicellulose improved the tensile strength and water resistance of composites, which may indicate a decrease in the hygroscopicity of wood flour, better compatibility, and interfacial bonding of the filler and matrix.
Composites Part A Applied Science and Manufacturing 04/2012; 43(4):686–694. DOI:10.1016/j.compositesa.2012.01.007 · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Switchgrass- and pine wood-derived biochars produced by fast pyrolysis were characterized to estimate the degree of thermochemical transformation and to assess their potential use as a soil amendment and to sequester carbon. The feedstocks were pyrolyzed to biochars in an auger reactor at 450, 600, and 800 °C with a residence time of 30 s. Ash contents of switchgrass and pine wood biochars varied from 13 to 22% and from 1.3 to 5.2%, respectively. Nutrients, such as N, P, K, S, Mg, and Ca, in switchgrass biochars ranged from 0.16 to 1.77%. Under combustion conditions, switchgrass chars were decomposed at lower temperatures than pine wood biochars because of the structural differences between the two feedstocks. Principal component analysis of the Fourier transform infrared (FTIR) spectra allowed for the discrimination of all biochars by significant contributions of cellulose-derived functionality at low pyrolysis temperatures, while the same analysis of the Raman spectra presented apparent separation of all biochars by two broad bands at 1587 and 1350 cm–1. These two broad peaks were deconvoluted into pseudo-subpeaks, which revealed that the number of aromatic rings linearly increased with the pyrolysis temperature. Cross-linkages between aromatic rings were also found to increase with thermal treatment, and switchgrass biochars contained a higher number of aromatic rings and cross-linkages than pine wood biochars, which was consistent with turbostratic carbon crystallites in the X-ray diffraction (XRD) pattern.
Energy & Fuels 09/2011; 25(10). DOI:10.1021/ef200915s · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hot-water pretreatment was performed on wood strands to investigate effects of the extraction of hemicellulose under different
temperature (140, 155, and 170°C) and time durations (30 and 60min) conditions. Hydrolysate was analyzed by means of high-performance
liquid chromatography. Chemical changes in the surface of wood strands were studied by infrared spectroscopy. The effects
of hemicellulose extraction on the wettability of wood strands were studied by measuring the contact angle and surface free
energy. The mechanical properties of wood cell walls before and after treatment were studied by nanoindentation. Among the
extracted monosaccharides, mannose was found in the highest concentration. The mechanical properties of cell walls showed
little decrease after extraction. The chemical changes in the surface of the wood strands reduced wettability of wood surface
by water and produced hydrophobic characteristics after extraction.
KeywordsHot-water extraction–High-performance liquid chromatography–Infrared spectroscopy–Wettability–Nanoindentation
[Show abstract][Hide abstract] ABSTRACT: Abstract
Hemicellulose is the most hydrophilic
polymer of wood, and as a polysaccharide
, it has potential applications in conversion to biofuels. The objective of this study was to enhance properties of flakeboard by extracting hemicellulose. Hotwater pretreatment
was performed to extract hemicellulose under different temperatures (140[degrees]C, 155[degrees]C, and 170[degrees]C) and times (30 and 60 min). The flakes were blended with 5 percent liquid phenol-formaldehyde resin and 1 percent wax emulsion. The mat was pressed at 200[degrees]C for 5 minutes. The physical and mechanical properties and the susceptibility of flakeboard to mold were studied. Panels made from the hemicellulose-extracted flakes showed remarkable decreases in water absorption and thickness swelling without a decrease in mechanical properties. Resistance of the panels to the mold growth also increased with increasing mass loss due to extraction. The most severe condition of extraction (170[degrees]C, 60 min), in addition to having the lowest water absorption and thickness swelling, showed the highest mold resistance.
[Show abstract][Hide abstract] ABSTRACT: Interest in recovering cellulose from biomass has grown steadily over the last few years as cellulose can be enzymatically hydrolyzed to sugars and fermented to ethanol. Under the Energy Independence and Security Act of 2007, refiners must produce 16 billion gallons of cellulosic ethanol per year by the year 2022. Switchgrass is a very promising lignocellulosic source for this ethanol. Switchgrass is a versatile and adaptable plant, as it can grow in different weather conditions. It is a perennial and can grow in poor soils that cannot support any food crops. It is not a food source so it will not compete for food crops. We are investigating solvent fractionation (organosolv processing) to isolate the required cellulose from switchgrass. Solvent fractionation is a process of choice for pretreatment because it is suitable for use with several different biomass feedstocks, giving favorable separations, easy isolation of products after fractionation, and offers recovery of each component in a high yield and purity amenable to conversion to other chemicals. Fractionation technology developed at the National Renewable Energy Laboratory is being used at the University of Tennessee for the separation of switchgrass into its primary components. The fractionation employs a mixture of organic solvents and water to separate switchgrass into cellulose, lignin and hemicellulose for the production of fuels and chemicals. Fractionation is carried out by adding biomass, a ternary solvent mixture, and a sulfuric acid catalyst to a 3.5 L, 3 bore, pressurized, Hastelloy flow-through reactor, controlled via LabVIEW and operating at three temperatures: 120 deg C, 140 deg C, and 160 deg C. The recovered solvent is subjected to a phase separation, giving an organic phase containing lignin and an aqueous phase containing hemicellulose. The cellulose fraction is obtained as a solid in an average yield of 38.6% by weight (7 runs). Lignin yield at an average of 6.3% by weight (9 runs) is fairly constant and independent of temperature and pressure. 2D NMR data used to determine structural changes in lignin as a function of separation conditions will be presented.
[Show abstract][Hide abstract] ABSTRACT: With the advancement of cellulosic ethanol technologies in recent years, more emphasis is being placed on the production of a sustainable supply of biomass for commercial scale facilities. These facilities will require significant supplies of biomass that will, in the southeast, come from private lands. The University of Tennessee, through its Biofuels Initiative, is working with private farmers to produce switchgrass on a large scale. The UT Biofuels Initiative is a research and demonstration effort to advance cellulosic ethanol technologies by establishing a dedicated biomass supply and constructing a pilot scale cellulosic ethanol production facility.
Working with private farmers, the Initiative is well on its way to planting 6,000 acres of switchgrass in a 50-mile radius area around the pilot plant site. The Initiative has developed an incentive program to attract participation from local farms. To participate in the program, Farmers submit an application and are selected based upon a set of criteria. In return for their participation and through a three-year contract, famers receive seed, technical support, and a yearly per acre payment to establish switchgrass. Once the switchgrass is harvested, the bales become property of the University. In 2008, the Initiative planted 723 acres. In 2009, a planned 2,000 acres will be planted, with an eventual scale-up to 6,000 acres.
The establishment of a dedicated energy crop on this scale creates a unique opportunity to conduct a range of research and development activities. The optimization of practices agronomic production, transportation and logistics, storage, preprocessing, biochemical cellulosic ethanol production, and bioproduct production are important to the success of a biorefinery.
[Show abstract][Hide abstract] ABSTRACT: Lignin is an abundant natural, renewable, polymer that constitutes roughly 30 percent of lignocellulosic biomass. Lignin is a high volume byproduct of any cellulose based biorefinery and a potentially important revenue stream. However, lignin's chemical and structural complexity and variability has limited its processing ability, which restricts its use in fibers, films, and other products. Understanding the rheological properties of lignin is fundamental for its successful use in polymer melts and solution processing. In order to achieve this goal, the shear rheology of different lignin samples was studied by measuring the complex viscosity and dynamic moduli at different temperatures. The lignin samples used were an alkali 2-hydroxy-proply ether, acetate organosolv, aspen organosolv and other derivatives of organosolv lignin. Master curves were generated for complex viscosity and dynamic moduli by using Cross, Carreau and Sisko viscosity models to fit the variability of the experimental data. From the Arrhenius plots of the shift factors with respect to temperature, the activation energies for shear flow were determined. The complex viscosity curves showed typical and atypical shear thinning behavior indicating that the lignin samples had a wide range of rheological properties. At lower temperatures, all the lignins appeared to have normal shear thinning behavior; however at higher temperatures the aspen lignin and the organosolv lignin derivatives exhibited an increase in viscosity. This indicated that at a certain temperature threshold, the lignin underwent a shift in its rheological properties.
[Show abstract][Hide abstract] ABSTRACT: To take advantage of the unique characteristics of the wood flour by combining them with plastic in conventional panel pressing methods, a wet process was developed to make composites using polypropylene and steam-exploded (SE) flour from small-diameter loblolly pine. Wet-laid wood flour/polymer composites were fabricated using a standard TAPPI handsheet method followed by compression molding. The variables that may affect the product properties were investigated using an orthogonal test design. The results revealed that the modulus of elasticity (MOE) of composites increased, while modulus of rupture (MOR) decreased with increasing SE wood flour content. Both MOE and MOR of the composites increased with maleic anhydride grafted polypropylene content. Dynamic mechanical analyzer and differential scanning calorimetry measurement gave insight into the structure of these composites, and scanning electron microscope was used to characterize the interfacial adhesion.
Holz als Roh- und Werkstoff 11/2009; 67(4):449-455. DOI:10.1007/s00107-009-0339-8 · 1.11 Impact Factor