Compositional Characterization and Pyrolysis of Loblolly Pine and Douglas-fir Bark Shaobo Pan & Yunqiao Pu & Marcus Foston & Arthur J. Ragauskas Published online: 31 May 2012 # Springer Science+Business Media, LLC 2012 Abstract Two potential biofuel resources, Douglas-fir and Loblolly pine bark, were subjected to extensive chemical and compositional analysis. The barks were initially extracted with dichloromethane, and the resulting extracted compounds were characterized by gas chromatography cou- pled with mass spectrometric analysis. Characterization of the major bark biocomponents indicated that Douglas-fir and Loblolly pine bark contained 22.5 and 13.2 % tannins, 44.2 and 43.5 % lignin, 16.5 and 23.1 % cellulose, and 7.6 and 14.1 % hemicellulose, respectively. Of particular inter- est is the high content of tannins and lignin, which make these barks excellent potential precursors for bio-oils and/or other value-added chemicals. 13 C nuclear magnetic reso- nance (NMR) was used to characterize the chemical struc- ture of the lignin and tannins. These samples were also analyzed by 31 P NMR after phosphitylation of the hydroxyl groups in lignin and tannins. The NMR spectral data indi- cated that the lignin in both barks contained p-hydrox- yphenyl (h) and guaiacyl (g) of lignin monomers with an h/g ratio of 10:90 and 22:78 for Douglas-fir and Loblolly pine bark, respectively. Gel permeation chro- matography was used to analyze the molecular weight distributions of extracted tannins, isolated cellulose, and ball-milled lignin. The pyrolysis of Douglas-fir and pine bark at 500°C in a tubular reactor generated 48.2 and 45.2 % of total oil, of which the light oil contents are 14.1 and 20.7 % and heavy oil are 34.1 and 24.4 %. Similarly, fast pyrolysis at 375°C yielded 56.1 and 49.8 % of total oil for Douglas-fir and pine bark, respectively. Keywords Loblolly pine bark . Douglas-fir bark . Extractive . Inorganic elements . Ball-milled lignin . Tannin . Cellulose . 13 C . 31 P NMR spectroscopy Introduction The use of renewable energy resources is now considered an essential component to address energy security and sustain- able economic development. Lignocellulosics are an abun- dant renewable feedstock for the global production of biofuels and valuable chemicals [1–3]. Among lignocellu- losic bioresources, bark is a highly under-utilized material. Apart from extractives and plant polysaccharides, softwood barks usually contains 40–55 % lignin which is a bio- component with higher energy density. Every year in the USA, an estimated 30 million tons of bark is generated whereas 27 million tons of the bark is currently employed as a low value thermal resource [4]. Therefore, the conversion of bark to bio-oils or chemicals is of significant interest and a topic of considerable research effort. Many researchers have attempted to convert barks by liquefaction [5–7] or pyrolysis [8–10] to bio-oils that could be further upgraded to transportation biofuels. These bio- oils have also been identified and evaluated as a potential feedstock for a variety of other fine and bulk chemicals. For example, pyrolysis-derived phenols are being examined to synthesize bio-based phenol-formaldehyde resins [11, 12]. However, the challenge of efficiently and cost-effectively S. Pan : Y. Pu : A. J. Ragauskas Institute of Paper Science and Technology, Georgia Institute of Technology, Atlanta, GA 30332, USA S. Pan : M. Foston : A. J. Ragauskas (*) School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA e-mail: arthur.ragauskas@chemistry.gatech.edu Bioenerg. Res. (2013) 6:24–34 DOI 10.1007/s12155-012-9223-1