Janis Gravitis

Studies of the Brazilian sugarcane bagasse carbonisation process and products properties

Abstract Laboratory-scale experiments in an enlarged scale thermoreactor have demonstrated that the pyrolysis of the bagasse bulk in a mechanically loosened layer yields 23–28% charcoal measured on an oven dry basis. The charcoal is appropriate for the production of fuel briquettes and granules for household and industry uses. To implement an energy self-sufficient production process, yields of condensable matter and gas components were determined. It is shown that their combined heat of combustion exceeds the upper limit of the heat necessary to carbonise the biomass by 1.6 to 1.8 times. To overcome the difficulties caused by a high fine particles content and the fibrous structure of bagasse, the use of a rotary drum type apparatus is suggested to be appropriate. Due to technological considerations, a two-stage process may be recommended: a heating up and pyrolysis stage up to 350°C, and a charcoal glowing stage with the peak temperature 475–500°C. Such a reactor unit with a joint furnace and closed pyroligneous vapour and heat carrier flow system greatly reduces the emission of carbon monoxide (CO) and dust particles. Bagasse can be used as an alternative source of traditional wood for charcoal production. It could prevent the deforestation of native forests.

Carbon materials obtained from self-binding sugar cane bagasse and deciduous wood residues plastics

Abstract It is demonstrated that dispersed biomass residues (bagasse, sawdust) can be processed into hard carbonaceous blocks, panels or boards with good strength and thermodynamic properties. There are two possible approaches: to mould dispersed biomass charcoal with a phenol–formaldehyde binder or to produce this material by carbonising the biomass fiberboard prepared by making use of steam explosion autohydrolysis pulp or steam explosion lignin as a binder. In the first step, steam explosion lignin, as a modifier and a binder is introduced to the lignocellulosic biomass by impregnation or during the hot pressing process to form a hard fiberboard. By subsequent carbonisation of the fiberboard panels or blocks, carbonised panels or blocks with high bending and crushing strength and suitable thermodynamic properties are obtained due to the formation of an internal lignin reinforcement in cell lumina and impregnation of cell walls with lignin solution or molten lignin. The carbonised panels demonstrate a good dimensional stability after a standard treatment with water. The bending strength of the carbonised panels after 24 h soaking in water is 93% of that in dry state. The thermodynamic properties and porosity of the carbonised panels demonstrate their suitability for use as a building material. Lignin, a natural binder of fiberboards, has proven to be suitable for preparation of cabonaceous panels and boards. In this respect new carbon building blocks and panels from moulded biomass and carbonised steam exploded biomass act as a concentrated form of long term carbon storage and will be a factor stabilizing the growing CO2 concentration in the atmosphere. [Proceedings of the First Workshop of QITS, Materials Life-Cycle and Environmentally Sustainable Development, March 2–4, Campinas, UNU/IAS San Paulo, Brazil, 1998, pp. 95–101; Proceedings of the Workshop in “Targeting Zero Emissions for the Utilization of Renewable Resources”, ANESC, Tokyo, 1999, pp. 2–11.]

Fullerene C60 destruction under shear deformation and high pressure action

Abstract Fullerene C 60 was subjected to shear deformation and high pressure (3.3 GPa) action. The products obtained can be divided into unchanged C 60 and a black substance insoluble in benzene. The latter part increases with severity of shear deformation applied. The IR and Raman spectra of the transformed material lacked significant signals, giving evidence of the destruction of the C 60 buckyball structure and formation of a phase closer to the amorphous system of sp 2 and sp 3 hybridized carbon atoms. Scratching and abrasion phenomena observed under SDHP action, must be attributed to the newly formed carbon phase and not to the initial C 60 nature.

Cellulose depolymerization to glucose and other water soluble polysaccharides by shear deformation and high pressure treatment

The simultaneous action of shear deformation and high pressure (SDHP) creates changes in the structure of wood and its main components (cellulose, hemicelluloses, lignin). The formation of water and alkali soluble polysaccharides under SDHP action, proceeds in seconds in the solid state, without the use of any reagents and solvents. Therefore, SDHP seems to be a technologically safe method and friendly to the environment. The amorphization of cellulose crystallites and depolymerization of cellulose chains were observed under a wide range of pressures (1–6 GPa), both for cellulose samples and the cellulose part of wood. Similar depolymerization occurs in the hemicellulose part of wood. The decomposition of polysaccharides under SDHP causes the formation of the water soluble part, whose content increases with pressure and the applied shear deformation. A maximum solubility of 40% and 55% was registered at 6 GPa following treatment of cellulose and birch wood samples. A higher output in the case of wood can be explained by a specific role of lignin under SDHP, which acts as a ‘grinding stone’ during cellulose and hemicelluloses destruction. As shown by high-performance size exclusion chromatography, the water soluble fraction obtained from cellulose contained glucose (2.6%), cellobiose (9.6%), cellotriose (16.6%) and other higher water soluble oligomers (71%). Almost complete dissolution (98%) of the treated cellulose sample can be achieved by extraction with 10% NaOH solution. The SDHP treated birch wood was subjected to submerged fermentation (with Trichoderma viride), and a 13% output of proteins was obtained. In this case, the water soluble part played the role of the so called ‘start sugars’. Abbreviations: ASF, alkali soluble fraction; DP, degree of polymerization; EC, energy consumption; HP, high pressure; LMWS, low molecular weight sugars; MC, moisture content; MCC, microcrystalline cellulose; SD, shear deformation, SDHP, shear deformation under high pressure; SS, shear strength; WSF, water soluble fraction

Utilization of lignin powder for manufacturing self-binding HDF

Abstract The preparation of self-binding lignocellulosic fibreboards has been investigated. Different high-density fibreboards (HDF) were hot-pressed based on a mixture of grey alder (Alnus incana L. Moench) wood chips processed by steam explosion auto-hydrolysis (SE) and 15% or 25% lignin content from three different industrial sources: softwood kraft lignin (SWKL), soda wheat straw lignin (SoWhStL) and hydrolysis wheat straw lignin (HWhStL). Density, thickness swelling (TS) after immersion in water for 24 h, modulus of rupture (MOR), modulus of elasticity (MOE) and strength of internal bond (IB) of the board samples were determined. The amount (15% or 25%) and moisture content (MC) (18±1% or 5±2%) of the added lignin affected all the tested properties of the HDF except for density. However, the kind of the added lignin affects the obtained fibreboard more significantly compared to the control sample made without an admixture of lignin. In some cases, the tested values were diminished to half. The tested properties of the HDF samples produced with SoWhStL or HWhStL are compatible with standard requirements for medium-density fibreboard (MDF) for general use under dry conditions (EN 622-5, MDF), however, it depends on the lignin amount and MC.

A Simple Analytical Model for Remote Assessment of the Dynamics of Biomass Accumulation

Efficient means for assessment of the dynamics and the state of the stocks of renewable assets such as wood biomass are important for sustainable supplies satisfying current needs. So far attention has been paid mainly to the economic aspects of forest management while ecological problems are rising with the expected transfer from fossil to renewable resources supplies of which from forest being essential for traditional consumers of wood and for emerging biorefineries. Production of biomass is more reliant on assets other than money the land (territory) available and suitable for the purpose being the first in the number. Studies of the ecological impacts (the “footprint”) of sustainable use of biomass as the source of renewable energy encounter problems associated with the productivity of forest lands assigned to provide a certain annual yield of wood required by current demand for primary energy along with other needs. Apart from a number of factors determining the productivity of forest stands, efficiency of land-use concomitant with growing forest depends on the time and way of harvesting (Thornley & Cannell, 2000). In the case of clear-cut felling the maximum yield of biomass per unit area is reached at the time of maximum of the mean annual increment (Brack & Wood, 1998; Mason, 2008). The current annual increment (rate of biomass accumulation by a forest stand or rate of growth) culminates before the mean annual increment reaches its peak value and there is a strong correlation between the maximums of the two measures. Knowing the time of growth-rate maximum (inflection point on a logistic growth curve) allows predicting the time of maximum yield (Brack & Wood, 1998). However, the growthrate maximum is not available from field measurements directly. Despite the progress in development of sophisticated models simulating (Cournede, P. et al., 2009; Thurig, E. et al., 2005; Welham et al., 2001) and predicting (Waring et al., 2010; Landsberg & Sands, 2010) forest growth, there still remains, as mentioned by J. K. Vanclay, a strong demand for models to explore harvesting and management options based on a few available parameters without involving large amounts of data (Vanclay, 2010). The self-consistent analytical model described here is an attempt to determine the best age for harvesting wood biomass by providing a simple analytical growth function on the basis of a few general assumptions linking the biomass accumulation with the canopy absorbing

Biomass conversion into blow-in heat insulation materials by steam explosion

Abstract The study of converting grey alder (Alnus incana) chips and silver birch (Betula pendula) flakes – residues from plywood manufacture – into blow-in insulation material by steam explosion (SE) is reported. The SE was conducted at temperatures between 200 and 235°C, for 0–5 min at pressures between 16 and 32 MPa. The severity parameters (logR0) of the SE was calculated, from which logR0≈3.6 was the most appropriate for production of blow-in materials. Thermal conductivity of the obtained insulating material was found to be in the range of 0.053–0.057 W m−1·K−1.

Limits to Sustainable Use of Wood Biomass

Amounts of wood biomass from fast-growing forest stands are assessed with respect to maximum land productivity and with account for the capacity of photosynthesis. The results expressed in normalised coordinates of time and stock in general are relevant to any even-age stand. By comparing the energy densities of solar radiation transformed by photosynthesis and photovoltaic devices the authors argue that generating electricity by burning wood is an extremely inefficient use of land under conditions of sustainable supply of the fuel and conclude that transfer to bio-energy without radical changes in the existing economic system would further aggravate the environmental crisis.

SYNTHESIS AND PROPERTIES OF NOVEL POLYELECTROLYTE ON THE BASIS OF WOOD POLYMER

ABSTRACT In this work, diluted reaction aqueous mixtures, containing polymer cation (PC), a weak polymer base, and sodium salt of birch nitrolignin (Na-Nlig) in a composition range of 0.1 ≤ Z ≤ 5, where Z = [PC]/[Na-Nlig] have been studied. Nitrolignin is an environmentally compatible by-product of the nitrate pulping process and possesses pronounced biostimulating action. The presence of various ionogenic groups imparts polyelectrolyte properties to the lignin macromolecule. It has been shown that the interaction between the reaction mixture components proceeds according to an electrostatic mechanism and results in the formation of novel polyelectrolytes (NPE), differing from Na-Nlig and PC, in terms of their behavior in aqueous media. The water solubility of the NPE formed is determined by the composition of the reaction mixture and depends on the extent of conversion in the interpolyelectrolyte reaction. An enhanced ability of adsorbing on the liquid/gas and liquid/liquid interfaces is conditioned by the presence of hydrophobic domains in NPE structure formed by the interacted regions of polycation and lignin-polyelectrolyte macromolecules. It has been shown that it is possible to regulate the hydrophilic-hydrophobic balance of the water soluble NPE structure by varying the extent of conversion in the interpolymer reaction. The last feature is of interest from the viewpoint of the use of NPE as a regulator of surface tension on various interfaces.