Kraft Pulping Of Wood Research Articles

A review on chemical mechanisms of kraft pulping

Abstract Kraft pulping of wood is based on efficient depolymerization and solubilization of lignin, while cellulose is relatively undamaged. Non-cellulose cell wall polysaccharides are however in some cases heavily degraded, especially pectin and to a lesser degree also glucomannan while, xylan is relatively stable. In this mini-review, the most important reactions in lignin and polysaccharide degradation in kraft pulping are described, both the technically favorable and the problematic reactions, and the chemical background to discuss the advantages and drawbacks of the process. An attempt to put the different reactions in the perspective of the goals of the pulping process is made and a special focus is on the development of color in the pulp fiber during the kraft pulping.

Effects of feeding wood kraft pulp silage containing sweet-potato shochu distillery by-product on feed intake, feed digestibility, rumen fermentation, blood components, and growth performance in Japanese Black fattening steers during early period.

The effects of long-term feeding of wood kraft pulp (KP) silage containing sweet-potato shochu distillery by-product (SDP) on feed intake, feed digestibility, rumen fermentation, and growth performance of Japanese Black steers were investigated during the early fattening period. Ten Japanese Black steers (9.8 ± 0.6months of age) were used in this study. Five steers (KP group) were fed KP silage as a replacement for 10% timothy hay (dry matter bases), in contrast to the other five (control group). KP silage consisted of 92.9% KP and 7.1% SDP (dry matter bases). The experiment was conducted for 18 weeks. No significant differences were observed in terms of feed intake, feed digestibility, or daily body weight gain between the groups. In addition, diurnal changes in the rumen pH and ruminal lipopolysaccharide activity did not differ between the groups. However, the plasma concentration of aspartate transaminase in the KP group was slightly lower (P = 0.078) than that in the control group. Thus, our study suggested that feeding KP silage does not reduce feed intake or affect the rumen fermentation or growth performance of Japanese Black fattening steer.

Effects of wood kraft pulp as a partial replacement for roughage on rumen fermentation and productivity in dairy cows.

In this study, we evaluated the partial replacement of roughage with wood kraft pulp (KP) on rumen fermentation and productivity of dairy cows. Eighteen cows were divided into control and KP groups. The KP group started adaptation to KP 3weeks before calving; after calving, they were fed a total mixed ration for 12 weeks, wherein 18% Timothy hay was replaced with KP. The dry matter intake, body weight, and milk yield and composition were similar in the control and KP groups. The average daily rumen pH was higher with KP feeding, and the average daily ruminal temperature remained lower at 16 days after calving (P < 0.05). The concentration of volatile fatty acids remained unaltered, the molar proportion of acetic acid decreased, and the molar proportion of propionic acid increased, indicating a low acetic acid:propionic acid ratio (P < 0.05). Lipopolysaccharide activity in the rumen fluid was higher in the KP group (P < 0.05); however, the rumen microbiota were unaffected. The digestibility of dry matter and neutral detergent fiber increased 12 weeks after calving, whereas excretion of urinary nitrogen decreased (P < 0.05). Partial replacement of roughage with KP did not suppress rumen fermentation and maintained postpartum productivity.

Bacterial nanocellulose and softwood pulp for composite paper

Abstract: Scaling biosynthesis of bacterial nanocellulose (BNC) allowed samples of composite paper with an increased proportion of BNC to be obtained. This work aims to study BNC samples and bleached soft wood kraft pulp (BSKP) composite paper with a ratio of components varying across a wide range: 10:90, 30:70, 50:50, 60:40, 70:30, 90:10. The method of paper manufacturing was chosen based on the determinations of strength and deformation properties of composite samples with the BNC:BSKP ratio of 20:80. Surface application of BNT on BSKP handsheet provided for an increase in the strength values (tear resistance – by 37%, burst index – by 17%) and deformation characteristics (tension stiffness – by 66%, fracture work – by 8%, breaking length – by 4%) compared to a reference sample. The formation of composites is confirmed in all samples. Scanning electron spectroscopy revealed that paper composites comprise interlaced micro BSKP and nano BNC fibres. As the proportion of BNC in composites elevated, densification of the structure was observed due to an increased fraction of cross-linked nanosized elements. IR spectroscopy indicated the resemblance of cellulose structure in all samples. It was found that an increase in the degree of polymerisation of composite paper is directly proportional to an increase in the BNC amount in the samples. The filtering ability of composite paper samples against microorganisms in the culture liquid of the Medusomyces gisevii Sa-12 producer was studied. It should be noted that yeast retention is achieved with 70% BNC in the paper composite. The presented properties of the new material determine prospects for its use in filtering microorganisms.

Effects of wood kraft pulp feeding on feed digestibility and rumen fermentation of Japanese Black steer in the middle fattening stage.

We investigated the effects of wood kraft pulp (KP) feeding on feed digestibility and rumen fermentation of Japanese Black (JB) steer in the middle fattening stage. The feeding experiment was carried out a replicated 3 × 3 Latin square design using six JB steers (16.2 ± 0.8months of age). Steers were fed rice straw and three concentrated feeds: commercial formula feed (control), formula feed containing 7.5% KP on a dry matter (DM) basis (7.5% KP), and formula feed containing 15% KP on a DM basis (15% KP). Feed digestibility and rumen fermentation parameters were recorded for 3days during the measurement period, after an adaptation phase of 11 days. There was no significant difference in DM intake per day among diets. A slightly higher digestibility of neutral detergent fiber was observed in steers fed 15% KP, compared with those fed other diets (P = 0.059). The butyric acid ratio in rumen fluid was higher in steers fed KP diets than in steers fed control (P = 0.083). The average ruminal pH was unaffected by KP diets. This study suggests that replacing 15% of concentrated feed with KP has little effect on feed digestibility and rumen fermentation in JB fattening steer.

Wood kraft pulp supplementation alters the rumen fermentation characteristics and epithelial transcriptomes in Holstein cattle during the high-grain diet challenge

We investigated the effects of wood kraft pulp (WP) supplementation on ruminal pH, fermentation, and epithelial transcriptomic dynamics in Holstein cattle during the high-grain diet challenge. Five rumen-fistulated Holstein bulls (215.2 ± 20.4 kg of body weight; 7.4 ± 0.3 months of age) were used in a cross-over design without a wash-out period. After two weeks of adaptation period (100% forage feeding ad libitum), cattle were fed a high-grain diet containing corn flakes (control diet) or the WP as a half replacement of corn flakes in the control diet (WP diet) during the first 14 days, and then, the diets were switched for last 14 days. Ruminal pH was measured continuously, and the rumen fluid and epithelium (RE) were collected on the last days of each feeding period simultaneously with blood samples. mRNA expression profiles of the RE were examined by one-color microarray. The differentially expressed genes (DEGs) were investigated using the Ingenuity Pathway Analysis (IPA). The 24 h mean ruminal pH was not different between the control (n = 5) and WP (n = 5) groups (6.39 vs. 6.46, respectively), being higher in the WP group. The proportion of acetic acid tended to be higher in the WP group, and blood urea nitrogen concentration was significantly higher in the WP group compared with the control group. The top differentially expressed candidate genes were involved in inhibition of the immune and inflammatory responses by suppressing the expressions of M-SAA3.2 and IL-36 cytokine signaling pathway (IL36G, IL36A, and IL36RN) in the WP group. In silico analysis revealed that “Remodeling of Epithelial Adherens Junctions” was the most significant signaling pathway, and epidermal growth factor receptor was the most significant upstream regulators, which were involved in the adaptation of the RE to high-grain diet challenge. Furthermore, upstream regulator analysis suggested that microRNAs may be involved in a central role in the RE cellular regulations. These results suggested that WP supplementation as 50% replacement of corn flakes in a high-grain diet did not cause significant contrast in the rumen fermentation and blood metabolite profiles, preferably leading the activation of rumen epithelial transcriptomes to facilitate the development or adaptation of the RE in Holstein cattle during the high-grain diet challenge.

Effect of feeding wood kraft pulp on the growth performance, feed digestibility, blood components, and rumen fermentation in Japanese Black fattening steers.

This study aimed to examine the effects of feeding kraft pulp (KP) on the growth performance, feed digestibility, and rumen fermentation of Japanese Black fattening steers. Ten Japanese Black fattening steers (aged 26 months) were randomly divided into control and KP groups. The control group (n = 5) was fed concentrate feed without KP, and the KP group (n = 5) was fed concentrate feed containing 10% KP. Both the groups were provided rice straw as roughage. The experiment was conducted over a period of 12 weeks. There was no significant difference in dry matter intake, daily body weight gain, and nutrient digestibility between both groups. No difference was observed in the ruminal concentrations of volatile fatty acids among the groups. At weeks 8 and 12 after the onset of the experiment, the acetate‐to‐propionate ratio in the ruminal fluid of the KP group was significantly higher than that of the control group. The average daily pH of ruminal fluid and activity of ruminal lipopolysaccharide did not differ between the groups. Our results suggested that the growth performance and feed digestibility in the Japanese Black fattening steers were not influenced by replacing concentrate feed with KP.

From Biomass to Nanomaterials: A Green Procedure for Preparation of Holistic Bamboo Multifunctional Nanocomposites Based On Formic Acid Rapid Fractionation

To achieve full utilization of lignocellulosic biomass and easy integration of nanomaterials production, it is essential to develop an efficient fractionation to overcome the highly recalcitrant nature of lignocellulose and facilitate the subsequent valuable conversion. Herein, in a combined process based on the formic acid rapid fractionation of bamboo chips, pure cellulose, and lignin were first obtained as fractionated streams. Compared to wood kraft pulp, the bamboo-originated cellulose was easily converted into cellulose nanocrystals (CNCs) using TEMPO oxidation in a relatively short time, which holds greater potential to meet the commercial cost target. The dissolved lignin was processed into nanoparticles (lignin NPs), which exhibited spherical morphology and a uniform particle size distribution. Dispersions of CNCs and lignin NPs were prepared and further filtrated to form nanocomposite membranes. The nanocomposite membranes exhibited a very smooth surface and homogeneous structure. Most impressiv...

Effect of wood kraft pulp feed on digestibility, ruminal characteristics, and milk production performance in lactating dairy cows.

The effect of wood kraft pulp (KP) feed on dietary digestibility, ruminal fluid pH, rumen fermentation characteristics, and milk production performance in lactating dairy cows was examined. Four lactating dairy cows were used for the feeding experiment by the cross‐over design. The control group and KP group were set up as treatments. The control group was fed total mixed ration (TMR) (40% roughage and 60% concentrate) and the KP group was fed TMR containing 12% KP that replaced half of the rolled corn in the control diet. The dry matter intake, digestibility of the feed components, and milk yield were not significantly different between control group and KP group. The number of times that the ruminal fluid pH was below 6.1 tended to decrease in the KP group compared to the control group (p < 0.10). The acetic acid ratio in the ruminal fluid of the KP group increased compared to the control group (p < 0.05) and the propionic acid ratio in the ruminal fluid of the KP group decreased compared to the control group (p < 0.05). The acetate:propionate acid ratio was increased in the KP group compared with the control group (p < 0.05). Lipopolysaccharide levels in the ruminal fluid of the KP group tended to decrease compared to the control group (p < 0.10). Based on these results, it was indicated that the use of KP feed for lactating dairy cows induced the same rumen fermentation characteristics as those in cows given a large amount of roughage without depressing milk productivity. Therefore, KP could be a valuable feed resource substitute for grains, which would also reduce the risk for subacute rumen acidosis.

Birch wood pre-hydrolysis vs pulp post-hydrolysis for the production of xylan-based compounds and cellulose for viscose application

Hydrothermal treatments of birch wood and kraft pulp were compared for their ability to extract the xylan and produce viscose-grade pulp. Water post-hydrolysis of kraft pulp produced a high-purity cellulosic pulp with lower viscosity but higher cellulose yield than traditional pre-hydrolysis kraft pulping of wood. Post-hydrolysis of pulp also increased the crystallite dimensions and degree of crystallinity in cellulose, and promoted a higher extent of fibril aggregation. The lower specific surface area in post-hydrolyzed pulps, derived from their larger fibril aggregates, decreased the accessibility of OH groups. However, this lower accessibility did not seem to decrease the pulp reactivity to derivatizing chemicals. In the aqueous side-stream, the xylose yield was similar in both pre- and post-hydrolysates, although conducting post-hydrolysis of pulp in a flow-through system enabled the recovery of high purity and molar mass (∼10 kDa) xylan for high-value applications.

Effect of Essential Oils on the Mechanical Properties of Lignocellulosic Materials

Biodeterioration of lignocellulosic materials is a worldwide problem and it causes a great damage especially to unique manuscripts and books stored in libraries. These materials are permanently subject to suffering from physical, chemical, and/or biological changes. Biological deterioration by microorganisms (bacteria and fungi) causes undesirable changes on material properties. Paper made by vegetal fibers, functional additives (glue, optical polishers, consolidating nts), and inks with organic bindings are used as sources of nutrients. Using of EOs (essential oils) for protection against microorganisms appears to be an option, because antimicrobial effects of the main compounds of EOs were proven. This work analyzes the antimicrobial stability of 2 essential oils (citral and linalyl acetate), as well as their stability of mechanical properties, in selected lignocellulosic materials (soft wood and hard wood kraft pulp, softwood sulphite pulp). Some parts of samples were subjected only to the condition of the EOs, other samples were firstly treated by accelerated ageing. Last samples were exposed to the accelerated ageing and afterwards treated by EOs. From the mechanical properties measuring of samples it is possible to state that in some SAJ samples the influence of EOs vapour is positive. This was monitored even when the samples were treated by accelerated ageing.

Generation of Hydrogen, Lignin and Sodium Hydroxide from Pulping Black Liquor by Electrolysis

Black liquor is generated in Kraft pulping of wood or non-wood raw material in pulp mills, and regarded as a renewable resource. The objective of this paper was to develop an effective means to remove the water pollutants by recovery of both lignin and sodium hydroxide from black liquor, based on electrolysis. The treatment of a 1000 mL of black liquor (122 g/L solid contents) consumed 345.6 kJ of electric energy, and led to the generation of 30.7 g of sodium hydroxide, 0.82 g of hydrogen gas and 52.1 g of biomass solids. Therefore, the recovery ratios of elemental sodium and biomass solids are 80.4% and 76%, respectively. Treating black liquor by electrolysis is an environmentally friendly technology that can, in particular, be an alternative process in addressing the environmental issues of pulping waste liquor to the small-scale mills without black liquor recovery.

Modeling and Optimization of Eucalyptus globulus Bark and Wood Delignification using Response Surface Methodology

Statistical models and optimization of Eucalyptus globulus Labill. wood and bark delignification were achieved using response surface methodology (RSM). A central composite design was outlined to model the simultaneous influence of active alkali (AA), reaction temperature (T), and reaction time (t) on pulp yield (η) and kappa number (k) during the kraft pulping of wood and bark. Experimental results were fitted to a second-order polynomial with linear interaction of factors. The statistical models showed high coefficients of determination for both wood (R2η = 0.991, R2k = 0.975) and bark (R2η = 0.993, R2k = 0.984). Using these models, the optimum conditions to attain a pulp with the highest yield at an acceptable kappa number (below 17) were determined. For wood, the pulp yield was 51.6% (51.5% predicted) and the kappa number was 16.1 (16.9 predicted) under optimized conditions (AA = 21%, T = 151 oC, and t = 118 min). For bark, the pulp yield was 51.3% (51.0% predicted) and the kappa number was 19.4 (16.9 predicted) under optimized conditions (AA = 15%, T = 166 oC, and t = 114 min). The degree of polymerization (DP) of the carbohydrates for the optimized pulps, 1430 and 1151 for wood and bark, respectively, suggests low levels of polysaccharide degradation. The bark delignification showed similar behavior to wood.

Changes in accessibility of cellulose during kraft pulping of wood in deuterium oxide

Fresh birch chips were treated with different concentrations of sodium hydroxide and sodium sulfide in deuterium oxide in typical kraft pulping conditions and the extent of irreversible deuteration of the chips/pulps was followed by Fourier transform infrared (FT-IR) spectroscopy. Water retention values (WRV) of pulps were measured to evaluate accessibility of cellulose. The kraft pulping with deuterium oxide led to significant proton-deuterium exchange that was not reversed when the chips/pulps were washed with water. The deuteration followed a first order dynamics with a maximum obtained in the beginning of delignification stage. Higher dosages of effective alkali resulted in a higher degree of deuteration and lower WRV. An inverse relationship between the extent of deuteration and WRV suggests that both were induced by cellulose microfibril aggregation. Results also indicate that hemicellulose dissolution plays an important role in the induction of cellulose microfibril aggregation, while lignin dissolution has less influence.

Alkali consumption of aliphatic carboxylic acids during alkaline pulping of wood and nonwood feedstocks

Abstract The carbohydrate degradation products have been examined, which are formed during the conventional kraft pulping of a softwood, hardwoods, bamboo, and wheat straw as well as soda and soda-anthraquinone pulping of wheat straw. The focus was on “volatile” acids such as formic and acetic acids and “nonvolatile” hydroxy monocarboxylic and dicarboxylic acids. The different consumption profiles were obtained for the charged alkali required for the neutralization of these aliphatic acids depending on the feedstock and the cooking method. The relative composition of the acid fraction in the black liquors of softwood and hardwood and nonwood feedstocks showed characteristic variations. However, in the case of wood kraft pulping, the variations in cooking conditions (effective alkali 19–21% and cooking temperature 155–170°C) had no significant effect on the acid composition. The total amount of volatile and hydroxy acids formed during pulping at a typical target κ number level for each feedstock ranged from 78 to 174 kg ton-1 based on o.d. feedstock. It was highest in birch kraft pulping and lowest in wheat soda-anthraquinone pulping.

Potential of Thermo and Alkali Stable Xylanases from Thielaviopsis basicola (MTCC-1467) in Biobleaching of Wood Kraft Pulp

Thermo- and alkali-stable xylanases produced from Thielaviopsis basicola (MTCC-1467) on low-cost carbon source like rice straw were evaluated for their potential application in biobleaching of wood kraft pulp. Enzyme treatment at retention time of 240 min with 20 IU/gm of dried pulp resulted in ~85.2 % of reduction in kappa number. When compared to control, 110.8, 93, and 72.2 % of enhancement in brightness (percent International Organization of Standardization), whiteness, and fluorescence, respectively, were observed for enzyme-treated pulp. Spectroscopic analysis showed significant release of chromophoric compounds from enzyme-treated pulp. Furthermore, scanning electron microscope studies of unbleached and enzyme bleached pulp revealed the effectiveness of enzymatic treatment. The enzyme-treated pulp subjected to later stages of chemical bleaching resulted in 16 % decrease in chlorine consumption along with considerable reduction in chemical oxygen demand percentage (14.5 %) level of effluent. Various pulp properties like fiber length, fiber width, burst strength, burst index, tear strength, tear index, tensile strength, and breaking length were also significantly improved after enzyme treatment when compared to control.

Bio-Treatment of Natural Fibers in Isolation of Cellulose Nanofibres: Impact of Pre-Refining of Fibers on Bio-Treatment Efficiency and Nanofiber Yield

Biodegradability, renewability and high specific strength properties of cellulose nanofibres and microfibrils have made them very attractive in nano-biocomposite science. Treatment of natural fibers with suitable enzymes or fungus has been found to substantially alleviate the high energy requirement associated with the isolation of cellulose nanofibers via high shear refining and subsequent cryocrushing. This article briefly describes a novel enzymatic fiber pretreatment developed to facilitate the isolation of cellulose nanofibres and explores the effect of pre-refining of fibers on the effectiveness of bio-treatment. Soft wood Kraft pulp was pre-sheared to different degree and treated with a genetically modified fungus isolated from fungus infected Dutch elm tree. Cellulose nanofibres were isolated from these treated fibers by high shear refining. The percentage yield of nanofibres from pre-refined fibers in the less than 50 nm range showed a substantial increase and at the same time the number of revolutions required during the high shear refining to attain a comparable level of nanofibres isolation decreased. This observation may be attributed to the better fiber internal accessibility of the enzymes due to loosening up of the fibers and increased number of fiber ends as a result of pre-refining.

Kraft pulping of wood treated with carbon-based preservatives

No abstract available

Potential of xylanase from thermophilic Bacillus sp. XTR-10 in biobleaching of wood kraft pulp

An extracellular xylanase produced under optimal conditions by a thermophilic strain of Bacillus sp. XTR-10 was evaluated for its potential application in biobleaching of wood kraft pulp. Spectrophotometric analysis showed considerable release of lignin derived compounds and chromophoric material by the xylanase treated pulp samples. Xylanase was found to be effective in the liberation of reducing sugars in the pulp filtrates with increment in enzyme dose and reaction time. Eight hours pretreatment with 40 IU of xylanase/g of dry pulp resulted in 16.2% reduction of kappa number with 25.94% ISO increase in brightness as compared to the control. The same treatment slightly lowered the tensile strength and burst index, however. Enzyme pretreatment of the pulp saved 15% active chlorine charges in single step and 18.7% in multiple steps chemical bleaching with attainment of brightness at the level of the control. These results indicate the potential of enzymatic pretreatment of pulp for reduction in environmental discharge of hazardous waste from the pulp and paper industry.

Heterogeneous studies in pulping of wood: Modelling mass transfer of alkali

In this paper a heterogeneous lumped parameter model is proposed to describe the mass transfer of effective alkali during the kraft pulping of wood. This model, based on the spatial mean of the concentration profile of effective alkali along the chip thickness, enables the estimation of the effective diffusion coefficient that characterizes the internal resistance to mass transfer and the contribution of the external resistance to mass transfer which has often been neglected. The experimental data that support this study comprise measurements of alkali concentration in the liquid phases, both inside and outside the chips. The kraft pulping of Eucalyptus globulus was carried out using broad range of temperature (80–165 °C) and effective alkali charge (10–45 g Na 2 O (100 g odw) −1 ). The model describes the effective alkali concentration profiles in the free liquor along the cooking with accuracy. The effective diffusion coefficient has been expressed by an Arrhenius-type equation and the estimated value of the activation energy for diffusion ( E a = 20.7 kJ mol −1 ) is in agreement with previous studies. The contribution of the external resistance to the overall mass transfer resistance showed to be significant and to increase with both temperature and effective alkali charge at industrial operation conditions. This result confirms the relevance of building a model that takes into account the heterogeneous nature of the kraft pulping of E. globulus .