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BioResources, Volume 2, Issue 2
NOTE: Each current issue of BioResources continues to build as new articles are approved.
In this editorial the author proposes that scientists and technologists can play essential roles in the selection of technological alternatives that are appropriate to people’s long-term needs. Lessons learned in the 1970s and 80s, involving the design of simple and reliable mechanical systems for underdeveloped regions, can have relevance today in an increasingly interdependent, crowded, and polluted world. Specialists can help in two ways to promote technologies that make sense, providing for future well-being, and minimizing risks. First, we can exercise personal judgment in our work, as we pursue technological progress. We need to consider whether the likely products of our work are compatible with the world that we want to leave for our grandchildren. Second, we can provide guidance to our fellow citizens, as society grapples with the political and economic choices associated with progress. PDF
Hervillard, T., Cao, Q., and Laborie, M.-P. G. (2007). "Improving water resistance of wheat straw-based medium density fiberboards bonded with aminoplastic and phenolic resins," BioRes. 2(2), 148-156.
A long standing problem in the manufacture of wheat-straw based composites with cost-effective formaldehyde-based resins is their poor water resistance as demonstrated by their large water thickness swell. In this study, wheat straw based medium density fiberboards were manufactured using 3 resin/wax systems: a melamine-urea-formalde-hyde resin with either low or high wax content, and a phenol-formal-dehyde resin with low wax content. The flexural properties, internal bond strength, and thickness swell of the resulting composites were evaluated and compared according to ASTM methods. The three MDF compos-ites passed the requirements for MDF in interior application, except for the MDF manufactured with the aminoplastic resin and low wax content that failed to provide acceptable thickness swell. Using the phenolic resin in combination with low wax content resulted in a higher grade MDF composite, grade 120, than with the aminoplastic and high wax content. This study demonstrates that wheat straw based MDF manu-factured with cost-effective aminoplastic and phenolic resins can have flexural properties, internal bond strength and thickness swell perfor-mance above the requirements from the American National Standards Institute. PDF
Siverio, F. O., Barbosa, L. C. A., Maltha, C. R. A., Silvestre, A. J. D., Pilo-Veloso, D., and Gomide, J. L. (2007). "Characterization of lipophilic wood extractives from clones of Eucalyptus urograndis cultivate in Brazil,"BioRes. 2(2), 157-168.
The chemical compositions of the lipophilic extractives from four clones of Eucalyptus urograndis cultivated in Brazil were studied by gas chromatography-mass spectrometry (GC-MS) before and after alkaline hydrolysis. The four E. urograndis clones showed similar amounts of dichloromethane soluble (lipophilic) extractives (0.38-0.55% w/w). The major groups of compounds identified in the lipophilic fraction of extractives consisted mainly of fatty acids (mainly palmitic linoleic and oleic acids and small amounts of a- and w-hydroxyacids), steroids (mainly b-sitosterol, b-sitostanol), followed by minor amounts long chain aliphatic alcohols, hydrocarbons and aromatic compounds. The relative abundances of these groups were similar for three of the clones with exception of the clone Ugc, which was shown to have much higher amounts of fatty acids and sterols. The high amounts of extractives found in these clones, and particularly of Ugc, when compared with other Eucalyptus species, suggests an increased risk of pitch formation during bleached pulp production. PDF
Qualitative lignin analysis relies rather much on studies of lignin degradation products. As concerns precise quantification of lignin’s composition such studies in general have obvious limitations. Aromatic acids obtained on permanganate oxidation of pretreated lignins (cleavage of ethers and alkylation of phenolic groups) offer a possibility to estimate the amounts of differently substituted aromatic units in lignins. An equation is derived for the calculation of the gross composition of lignins based on the yields of methoxy-substituted aromatic acids obtained on permanganate oxidation of lignins with methylated phenolic groups. The equation could also be used for the calculation of the phenolic content in a lignin sample based on permanganate oxidation data, provided that such data are available for a similar lignin sample with known phenolic content. Literature data for milled wood lignin from spruce are used to exemplify the calculations. PDF
Four commercial barrier coated boards (i.e., internally-sized uncoated board, one-side polyethylene coated board, double-side polyethylene coated board, and multilayer laminated board) were examined for biodegradation using a soil burial approach on a laboratory scale. It was observed that the base-boards were fully biodegradable in a matter of weeks or months, and the degradation process could be accelerated either by sample size modification or enrichment of the soil microbial population. Freezing pretreatment of boards or the fiber directionality of boards had no influence on the rate of degradation. The boards were also found to be recyclable following a simple procedure of re-slushing and screening. The base-boards became almost fully separated from the polyethylene coated material without any special pretreatment. PDF
The effects of thermo-compression on the physical properties such as bulk density, mass yield, surface area, and also adsorption capacity of activated carbon were studied. The activated carbon samples were prepared from thermo-compressed and virgin fir-wood by two methods, a physical activation with CO2 and a chemical activation with KOH. A preliminary thermo-compression method seems an easy way to confer to a tender wood a bulk density almost three times larger than its initial density. Thermo-compression increased yield regardless of the mode of activation. The physical activation caused structural alteration, which enhanced the enlargement of micropores and even their degradation, leading to the formation of mesopores. Chemical activation conferred to activated carbon a heterogeneous and exclusively microporous nature. Moreover, when coupled to chemical activation, thermo-compression resulted in a satisfactory yield (23%), a high surface area (>1700 m2.g-1), and a good adsorption capacity for two model pollutants in aqueous solution: methylene blue and phenol. Activated carbon prepared from thermo-compressed wood exhibited a higher adsorption capacity for both the pollutants than did a commercial activated carbon. PDF
Chakraborty, A., Sain, M. M., Kortschot, M. T., and Ghosh, S. B. (2007). "Modeling energy consumption for the generation of microfibres from bleached kraft pulp fibres in a PFI mill," BioRes. 2(2), 210-222.
The objective of this paper is to model the energy consumed in generating cellulose microfibres, 1 μm in diameter, as reinforcing agents, by refining bleached softwood kraft pulp in a PFI mill. An average initial fibre diameter of 13 μm was assumed. 125,000 revolutions in a PFI mill was found to produce a high yield of fibres 1.3 μm in diameter, and the minimum refining energy needed to reduce the fibre diameter to 1.3 μm was estimated as 1875 kJ for each 24 g charge in the PFI mill. Since elastic deformation of the fibres was found to be negligible, the size reduction was assumed to follow Rittinger’s Law. This gave a Rittinger’s constant of 28 J.m/kg for the given system. Using this value of Rittinger’s constant, the energy required to generate microfibres 1 μm in diameter was predicted as 2480 kJ for each 24 g charge in the PFI mill. It was deduced that microfibres generated in this way would cost a minimum of $2.37 per kilogram. Hence even this relatively inefficient method of grinding would not be prohibitively expensive, provided the resulting microfibres can be used as high quality reinforcements. PDF
Industrially made kraft pulps obtained by a modified cooking process may contain 60-75 mmol/kg of hexenuronic acids (HexAs), which represents 6-7.5 kappa units. HexAs do not react with oxygen and very little of it is actually removed across the oxygen delignification stage, causing low efficiencies in the range of 25-35%. In this study, an economical evaluation of the ECF bleaching processes was carried out, having none and double-stage oxygen delignification, when applied to eucalyptus pulps of kappa varying in the range of 14-21. The bleaching processes included sequences containing specific stages for HexAs removal (Z, A/D and DHT). Results indicated that the use of oxygen delignification was not economically attractive, particularly for HexA-rich low-kappa pulps, but processes without oxygen delignification present significant environmental challenges. PDF
Ruelle, J., Yamamoto, H., and Thibaut, B. (2007). "Growth stresses and cellulose structural parameters in tension and normal wood from three tropical rainforest angiosperm species," BioRes. 2(2), 235-251.
Few studies have been conducted about relation between cellulose para-meters and biomechanical properties of wood in tropical angiosperms species. For this purpose, on 13 trees from 3 species of French Guyana tropical rainforest in a clear active process of restoring verticality, i) growth strains were measured in situ in order to determine the occurrence of tension wood within samples and ii) cellulose structural parameters were estimated on all the samples using X-ray diffraction method. Crystallite size was estimated from the full-width at half-maximum of the Miller index (002) arc diffraction and angle T was measured following Cave’s method. Relationships between these parameters and growth stresses were good and the variations between normal and tension wood were significant, i.e. a lower angle T and a larger crystallite size in tension wood. In order to have a good estimation of the microfibril angle in the main layer of the secondary wall for each species, an experimental calibration was done between angle T and microfibril angle observed with scanning electron microscopy. PDF
Scale formation in the digester during kraft pulping represents a great problem in pulp mills. Scaling reduces pulping control and efficiency, increasing energy costs and leading to cleaning breakdowns, with subsequent losses in productivity. The kraft process promotes CaCO3 scaling due to high calcium ion and carbonate concentrations, as well as high alkalinity and temperature levels, which increase the speed with which liquors reach a state of supersaturation. This work examines the action of diethylene triamine penta(methylene phosphonic acid) (DTPMPA), either alone or combined with commercial anti-scaling agents, as an inhibitor of calcium carbonate precipitation in the kraft pulping of Pinus taeda. The theoretical amount of calcium deposited in the digester was obtained by mass balance. Soluble calcium was stable throughout cooking when using the phosphonates alone or combined with anti-scaling agents. When adding only DTPMPA, calcium stays in the pulp, rather than forming deposits. PDF
In this study, clove bud oil, which was cultivated in the Mediterranean region of Turkey, was provided from a private essential oil company in Turkey. Essential oil from clove (Syzygium aromaticum L.) was obtained from steam-distillation method, and its chemical composition was analyzed by GC and GC-MS. The results showed that the essential oils mainly contained about 87.00% eugenol, 8.01% eugenyl acetate and 3.56% β-Caryophyllene. The chemical composition of the Turkish clove bud oil was comparable to those of trees naturally grown in their native regions. PDF
Pérez, J. M., Rodríguez, F., Alonso, M. V., Oliet, M., and Echeverría, J. M. (2007). "Characterization of a novolac resin substituting phenol by ammonium lignosulfonate as filler or extender," BioRes. 2(2), 270-283.
In this work two types of lignin-novolac resins have been formulated, partially substituting phenol by softwood ammonium lignosulfonate as filler or extender (methylolated) to study the viability of that substitution when resins will be employed as adhesives in textile felts. A commercial novolac resin was used as reference. Free phenol, free formaldehyde, water content, softening point, and flow distance values were determined in all cases to verify whether the material fulfills specifications. In addition, FTIR and NMR spectroscopic techniques were employed for the characterization of three resins samples tested to discuss their structural differences and similarities. The results obtained have shown that the substitution proposed is feasible from the point of view of the resins synthesis to get the pre-polymer. PDF
Wood cell wall polysaccharides can be probed with monoclonal antibodies and carbohydrate-binding modules (CBMs). Binding of monoclonal antibodies to β-1-4-xylan, β-1-4-mannan, β-1-3-glucan, and α-1-5-arabinan structures were observed in native Sitka spruce (Picea sitchensis (Bong.) Carrière) wood cell walls. Furthermore CBMs of different families, differing in their affinities for crystalline cellulose (3a) and amorphous cellulose (17 and 28), were shown to bind to the native wood cell walls with varying intensities. Resin channel forming cells exhibited an increased β-1-4-xylan and a decreased β-1-4-mannan content. Focusing on severe compression wood (CW) tracheids, β-1-3-glucan was found towards the cell lumen. In contrast, α-1-5-arabinan structures were present in the intercellular spaces between the round tracheids in severe CW, highlighting the importance of this polymer in cell adhesion. PDF
Cellulosic fibers in aqueous suspensions are subject to flocculation effects that involve two contrasting scales of dimension. The net effect of flocculation determines how uniformly fibers can become formed into a sheet during the manufacture of paper. At a macroscopic level, the highly elongated shape of typical wood-derived fibers in agitated suspensions can give rise to frequent inter-fiber collisions and the formation of fiber flocs. At a submicroscopic scale, surfaces of suspended materials can become joined by macromolecular bridges. Although such bridges tend to reduce paper’s uniformity, polyelectrolyte flocculants are used in most paper machine systems to achieve relatively high retention efficiencies of fine particles as paper is being formed. By adjusting the papermaking equipment, judiciously selecting points of addition of chemicals, and by managing chemical dosages, papermakers employ a variety of strategies to achieve favorable combinations of retention and uniformity. This review considers scholarly work that has been directed towards a greater understanding of the underlying mechanisms. PDF