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Atlanta, GA, United States

David K.,Institute of Paper Science And Technology | Ragauskas A.J.,Institute of Paper Science And Technology
Energy and Environmental Science | Year: 2010

Over the past two decades, the use of biomass as a resource for biofuels and bioenergy has garnered much interest. The reduction in green house gas emissions of renewable fuels as compared to conventional fossil fuels, coupled with the sustainability of these technological approaches, has fostered increased research into this field. Switchgrass is a perennial grass native to North America, and as a feedstock for biofuels it has garnered much interest because of its high productivity, adaptability and potential ease of integration into existing agricultural operations. In order to maximize the use of switchgrass as an energy crop, the chemical constituents as well as the chemical processes involved in its conversion to biofuels need to be understood. The goal of this paper is to review the published work on the chemistry of switchgrass as it pertains to biofuel production including elemental composition, chemical composition, biopolymer constituents and their structure. In addition, the impacts of these chemical constituents on the biological conversion to ethanol and pyrolysis oils are summarized. © The Royal Society of Chemistry 2010.

Kosa M.,Institute of Paper Science And Technology | Ragauskas A.J.,Institute of Paper Science And Technology
Green Chemistry | Year: 2013

A metabolic route yielding lipids from lignin would represent innovative applications for this recalcitrant biomass component. In this study ethanol organosolv lignin (EOL) and ultrasonicated EOL (us-EOL) were utilized in Rhodococci bioconversions. Both lignins proved to be sufficient carbon sources, moreover, lipid formation was also observed, up to 4.08%. © 2013 The Royal Society of Chemistry.

Ben H.,Institute of Paper Science And Technology | Ragauskas A.J.,Institute of Paper Science And Technology
Green Chemistry | Year: 2012

The torrefaction of Loblolly pine (Pinus taeda) was examined at 250 and 300 °C, to determine the effects of treatment temperatures on the chemical structure of the torrefied Loblolly pine. Solid-state cross-polarization/magic angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) spectroscopy was used to characterize the torrefied and native Loblolly pine. The NMR results indicate that aryl-ether bonds in lignin were cleaved during the torrefaction. The methyl carbons in hemicellulose acetyl groups were no longer present after the torrefaction at 250 °C for 4 h, which is consistent with HPLC carbohydrate analysis of the torrefied wood which indicated that the hemicellulose fraction of pine was completely absent, whereas the cellulose and lignin remained largely intact. Under these conditions the torrefied wood has a relatively high energy yield of 81.29% and a HHV of 24.06 MJ kg -1. After torrefaction at 300 °C for 4 h, the cellulose and hemicellulose in the wood were completely eliminated, the residue contains enriched amounts of carbonyl groups, aromatic carbons and methoxyl groups, which represent complex condensed aromatics, these aromatics units were linked with aliphatic C-O and C-C bonds and the product has a very high HHV of 32.34 MJ kg -1. © 2012 The Royal Society of Chemistry.

Foston M.,Institute of Paper Science And Technology | Ragauskas A.J.,Institute of Paper Science And Technology
Biomass and Bioenergy | Year: 2010

Dilute acid pretreatment (DAP) is commonly employed prior to enzymatic deconstruction of cellulose to increase overall sugar and subsequent ethanol yields from downstream bioconversion processes. Typically optimization of pretreatment is evaluated by determining hemicellulose removal, subsequent reactivity towards enzymatic deconstruction, and recoverable polysaccharide yields. In this study, the affect of DAP on the supramolecular and ultrastructure of lignocellulosic biomass was evaluated. A series of dilute acidic pretreatments, employing ~0.10-0.20 mol/m 3 H 2SO 4 at ~160-180 °C, for varying residence times were conducted on both Populus and switchgrass samples. The untreated and pretreated biomass samples were characterized by carbohydrate and lignin analysis, gel permeation chromatography (GPC) and 13C cross polarization magic angle spinning (CPMAS) NMR spectroscopy. GPC analysis shows a reduction in the molecular weight of cellulose and change in its polydispersity index (PDI) with increasing residence time, indicating that pretreatment is actually degrading the cellulose chains. 13C CPMAS and non-linear line-fitting of the C 4 region in the carbon spectrum of the isolated cellulose not only showed that the crystallinity index increases with residence time, but that the lateral fibril dimension (LFD) and lateral fibril aggregate dimension (LFAD) increase as well. © 2010 Elsevier Ltd.

Ben H.,Institute of Paper Science And Technology | Ragauskas A.J.,Institute of Paper Science And Technology
Bioresource Technology | Year: 2013

The pyrolysis of softwood (SW) kraft lignin and pine wood in different pyrolysis systems were examined at 400, 500 and 600°C. NMR including quantitative 13C and Heteronuclear Single-Quantum Correlation (HSQC)-NMR, and Gel Permeation Chromatography (GPC) were used to characterize various pyrolysis oils. The content of methoxyl groups decreased by 76% for pine wood and 70% for lignin when using fast pyrolysis system. The carbonyl groups also decreased by 76% and nearly completely eliminated in 600°C pine wood fast pyrolysis oil. Compared to the slow pyrolysis process, fast pyrolysis process was found to improve the cleavage of methoxyl groups, aliphatic CC bonds and carbonyl groups and produce more polyaromatic hydrocarbons (PAH) from lignin and aliphatic CO bonds from carbohydrates. Another remarkable difference between fast and slow pyrolysis oils was the molecular weight of fast pyrolysis oils increased by 85-112% for pine wood and 104-112% for lignin. © 2013 Elsevier Ltd.

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