Non-wood Biomass Research Articles

The Use of Forestry and Agricultural Biomass in the Production of Pellets

Abstract The use of forestry and agricultural biomass for pellet production represents a significant opportunity to strengthen a sustainable economy characterized by reducing dependence on fossil fuels and more efficient protection of the environment. The aim of this paper is to improve the understanding of the current state of research on the use of forestry and agricultural biomass for pellets production, fostering awareness of their potential for energy production. In the development of the work, various research stages and techniques were used. These included the analysis of international trade data wood pellets, literature review of research dynamics on agricultural biomass pellet production from last decade, identification of articles from prestigious journals to highlight key trends and concerns in research, analysis of research concentration areas, and investigation and analysis of collaboration networks among researchers and institutions. These methodological approaches have contributed to the creation of a comprehensive and updated work, providing a deeper and clearer understanding of the researched topic. The European Union represents a major force in the global consumption of wood pellets, with demand for this product steadily increasing. Additionally, Romania has significant exports of wood pellets to other European countries, indicating considerable potential for the development of the pellet industry in the country. Furthermore, the literature emphasizes the importance of non-wood biomass, such as agricultural residues, as a crucial source for pellet production. The literature review reveals an increasing focus on biomass pellets in recent years, with research concentrating on various domains such as biotechnology, energy fuels, and sustainable green technology.

High-pressure microwave-assisted pretreatment of softwood, hardwood and non-wood biomass using different solvents in the production of cellulosic ethanol

BackgroundPretreatment is an indispensable stage of the preparation of lignocellulosic biomass with key significance for the effectiveness of hydrolysis and the efficiency of the production of cellulosic ethanol. A significant increase in the susceptibility of the raw material to further degradation can be attained as a result of effective delignification in high-pressure conditions. With this in mind, a method of high-pressure pretreatment using microwave radiation and various solvents (water, 40% w/v NaCS, 1% v/v H2SO4, 1% w/v NaOH or 60% v/v EtOH with an addition of 1% v/v H2SO4) was developed, enabling the acquisition of biomass with an increased susceptibility to the process of enzymatic hydrolysis. The medium obtained in this way can be used for the production of cellulosic ethanol via high-gravity technology (lignocellulosic media containing from 15 to 20% dry weight of biomass). For every type of biomass (pine chips, beech chips and wheat straw), a solvent was selected to be used during the pretreatment, guaranteeing the acquisition of a medium highly susceptible to the process of enzymatic hydrolysis.ResultsThe highest efficiency of the hydrolysis of biomass, amounting to 71.14 ± 0.97% (glucose concentration 109.26 ± 3.49 g/L) was achieved for wheat straw subjected to microwave-assisted pretreatment using 40% w/v NaCS. Fermentation of this medium produced ethanol concentration at the level of 53.84 ± 1.25 g/L. A slightly lower effectiveness of enzymatic hydrolysis (62.21 ± 0.62%) was achieved after high-pressure microwave-assisted pretreatment of beech chips using 1% w/v NaOH. The hydrolysate contained glucose in the concentration of 91.78 ± 1.91 g/L, and the acquired concentration of ethanol after fermentation amounted to 49.07 ± 2.06 g/L. In the case of pine chips, the most effective delignification was achieved using 60% v/v EtOH with the addition of 1% v/v H2SO4, but after enzymatic hydrolysis, the concentration of glucose in hydrolysate was lower than in the other raw materials and amounted to 39.15 ± 1.62 g/L (the concentration of ethanol after fermentation was ca. 19.67 ± 0.98 g/L). The presence of xylose and galactose was also determined in the obtained fermentation media. The highest initial concentration of these carbohydrates (21.39 ± 1.44 g/L) was observed in beech chips media after microwave-assisted pretreatment using NaOH. The use of wheat straw after pretreatment using EtOH with an addition of 1% v/v H2SO4 for the preparation of fermentation medium, results in the generation of the initial concentration of galactose and xylose at the level of 19.03 ± 0.38 g/L.ConclusionThe achieved results indicate a high effectiveness of the enzymatic hydrolysis of the biomass subjected to high-pressure microwave-assisted pretreatment. The final effect depends on the combined use of correctly selected solvents for the different sources of lignocellulosic biomass. On the basis of the achieved results, we can say that the presented method indicates a very high potential in the area of its use for the production of cellulosic ethanol involving high-gravity technology.

Physico-chemical and Energy Characteristic of Charcoal Derived from Two (Different) Sarawak Wild Bamboo Species

Bamboo has a very rapid growth rate and has been considered a promising non-wood biomass material that has the potential as a feedstock for charcoal production. This study was carried out to elucidate the physico-chemical and energy characteristic of bamboo charcoal produced from two (2) different species which were Aur Kuning Bamboo and Beting Bamboo. Each bamboo was carbonized at a temperature of 300 to 400oC for a duration of two hours. It was found that the density and volatile matter content of bamboo charcoal have decreased, while the ash content, fixed carbon (FC) content and calorific value (CV) have increased after being converted into charcoal. The results show that Aur Kuning Bamboo has good quality bamboo charcoal in comparison with Beting Bamboo in terms of its FC and CV content. Based on the average value, the FC (82.10%) and CV of Aur Kuning Bamboo (27.23%) were higher than FC (70.42%) and CV (26.05%) of Beting Bamboo with 16.59% (FC) and 4.53% (CV) different. Statistical analysis showed that there was a significant effect for different species of bamboo and a significant correlation between physical and energy properties. In conclusion, Aur Kuning Bamboo harvested from Sarawak wild forest has a higher potential to be a feedstock for charcoal production that will be useful for various applications in the near future.

Production of versatile biosorbent via eco-friendly utilization of non-wood biomass

Biomass accumulation is an urgent issue of sustainable nature management because its conglomerations occupy vast agricultural areas. Since the non-wood biomass is a source of valuable polymer materials – cellulose and lignin, the development of technologies for this waste processing is an important scientific task. This study proposes an eco-friendly method of Juglans Regia L. walnut shells and Prunus Armeniaca L. apricot kernels processing, which ensures their complete utilization with the production of an effective biosorbent and liquid multicomponent fertilizer. At the first stage, processing of raw biomass with a solution of 25 vol% NH4OH with a specific NH3 consumption of 0.72 g g−1, provides a delignification degree of 85 %, and the specific output of cellulose reaches at least 90 %. Delignification significantly increases the biomass' specific surface up to 110 m2 g−1 and iodine number up to 32 mg g−1, however, exchange capacity decreases by 45–55 %. To improve ion exchange properties, the intermediate cellulose product was phosphorylated in an aqueous solution with urea addition. Obtained biosorbent has a capacity for heavy metals ions up to 270 mg g−1, and uranium – 196 mg g−1. Biosorbent is also capable of removing numerous metal cations and various synthetic dyes from the water, so it can be used in water purification technology. An environmentally friendly method for waste solutions disposal ensures the production of liquid complex fertilizer containing 17 wt% N and 14 wt% P. Feeding grain crops with this fertilizer increases the plants' length by 40–75 %, and their total weight by 20–30 %.

Optimization of Hemp Bast Microfiber Production Using Response Surface Modelling

Non-wood biomass is particularly attractive as a cellulose source because of the lower lignin content. However, optimal cellulose extraction conditions are required as lignin content varies between plant sources. Further, the use of organic acids in place of harsh mineral acids is of interest in “greening” the cellulose production process. This study sought to establish optimum parameters for the extraction of cellulose microfibers (CMFs) from hemp (Cannabis sativa) biomass, using maleic and formic acids. Hemp fibers were pre-treated in NaOH (4 wt%) and aqueous chlorite in acetate buffer before ultrasonic treatment to break down bundles. The CMFs produced were compared with those generated from sulfuric acid hydrolysis. Response surface methodology (RSM) was used to determine combinations of three processing conditions, including acid concentration (45–64%), hydrolysis time (30–90 min), and temperature (45–65 °C). A central composite design (RSM-CCD) model with 21 experimental runs was optimized using MODDE 13.1 software. The model suitably described the data (R2 = 0.99; R2adj = 0.96). Microfibers with an average width of 6.91 µm, crystallinity range 40–75%, and good thermal stability were produced. Crystallinity was influenced by all three factors. The optimal crystallinity predicted by the model was 83.21%, which could be achieved using formic acid 62 wt% formic acid, 36 min hydrolysis time, and 47 °C hydrolysis temperature. These conditions resulted in a crystallinity degree of 82%. These data suggest formic acid can be used as an alternative to sulfuric acid for synthesis of cellulose microfibers from biodegradable hemp waste fibers.

Influence of sample preparation process on basic properties of biofuels

The characteristic properties of non-wood biomass used in combustion processes are monitored, such as water content, ash, volatile matter. Biomass is usually not homogenous and of suitable dimensions for these determinations. This is the reason for the necessary adjustment of samples for analysis. But modifying the samples may change their properties. In this publication, the influence of the grinding process in a rotor mill on the content of water, volatile matter and ash in non-wood biomass samples was studied. Samples of flax, Crambe abyssinica, amaranth and rye were analyzed. All analyses showed moisture loss from the sample during grinding and in the case of flax, the loss of volatile matter was observed. It means the rotor mill is suitable for sample preparation prior to analysis. But for oil plants it is necessary to choose another mill or adjustment method.

Screw extrusion pretreatment for high-yield lignocellulose nanofibrils (LCNF) production from wood biomass and non-wood biomass

To develop a facile and low-cost nanofibrils process with excellent feedstock adaptability, high-yield lignocellulose nanofibrils (LCNF) are produced directly from wood and non-wood biomass using glycerol solvent via screw extrusion pretreatment. Different LCNFs are obtained from four classical raw materials (polar, pine, bamboo, and wheat straw) in this research, followed by comparing their morphological, thermochemical, and mechanical properties. More than 70 wt% of LCNF could be obtained from low-cost substrates except for LCNF from wheat straw with 62.3 wt% yield. Besides, the morphology property of wood LCNF exhibit more uniform distribution over that of non-wood LCNF due to narrower size distribution. Strikingly, despite of the slightly lower LCNF crystallinity various from 52.4% to 62.6% obtained from four substrates, all the LCNFs separated from wood and non-wood biomass exhibit high thermal stability (Tmax over 330 °C), which is higher than conventional nanocellulose, indicating that the crystal area could be well maintained during the pretreated process. Moreover, all the LCNF films show excellent tensile strength which is close to nanocellulose materials. Besides, the Young's modulus of wood-based LCNF films is higher than that of non-wood based LCNF films. Overall, LCNF with excellent performance could be achieved from low-cost biomass by our facile process, which provides a feasible route for industrial production of bio-based nanofilms.

High-pressure homogenized citrus fiber cellulose dispersions: Structural characterization and flow behavior

Functionalized biomass waste sources of cellulose have drawn attention due to their high availability and sustainability properties. In this work we characterize the structural and flow properties of high-pressure homogenized citrus fiber cellulose dispersions, employing SAXS, rheology and rheo-MRI techniques. The high-pressure treatment disrupts the microfibrillar network within the citrus fibers, but leaves the individual microfibrils intact. Under moderate shear (0.1-100 s-1) in a confined (<1 mm) geometry, these functionalized citrus fiber cellulose dispersions exhibit thixotropic shear-banding behavior accompanied by cooperative flow of microfibril flocs with correlation lengths ξ~ 100 μm. The presented findings form a basis towards understanding and manipulating the structural and rheological properties of non-wood biomass cellulose microfibrils under industrially-relevant conditions.

Utilization of non-wood biomass for pulp manufacturing in paper industry: case of Ethiopia

There are many pulp and paper industries all around the globe and in Ethiopia as well different companies are involved in the production and distribution of paper and paper products. Most of the industries especially those in developing countries like Ethiopia produce paper from pulp obtained from wood cellulose. Ethiopia is not producing its pulp and mostly the paper industries depend on imported pulp or recycled paper. There are critical limitations in synthesizing pulp and paper from wood-based cellulose resources mainly the scarcity of wood in some countries and the impact on altering the ecological balance and through frequent deforestation and replantation practice. The present review assesses the potential sources from non-wood resources which can be used as a substitute cellulose raw material for the pulp and paper industry. The study encompasses possible beneficiation routes for manufacturing pulp from non-wood cellulose resources available in Ethiopia for diversified application in the paper industry. With this regard, potential non-wood raw materials for pulping are assed in line with the fulfilment of the target for import substitution strategy, the realization of a safe working environment, and socio-economic betterment of the nation with specific reference to the paper industry.

The influence of temperature and oxidizing atmosphere on the process of combusting pellets from agricultural and forest biomass in the stream of inert material

Wood pellets are a commonly used biomass for energy production. However, due to the growing demand, many entrepreneurs have begun to produce non-wood biomass pellets. During experimental research, the process of combusting pellets of forest and agricultural origin at different furnace temperatures and different oxidizing atmospheres in a two-phase flow with the use of inert material modelling conditions in the upper zone of the fluidized bed reactor was analyzed. Inert material caused very significant differences in the time and mechanism of forest and agro biomass combustion. These differences are mainly associated with problematic phenomena during combustion, including sintering of ashes. The inert material accelerated the mass loss of forest biomass pellets at all temperatures by about 50–60%. In the case of agro biomass, the combustion time at the temperatures of 650 °C and 750 °C was shortened by about 20–30%, and in the case of the temperature of 850 °C, it was extended by about 10%. Increasing the value of the inert material stream resulted in a reduction of the combustion time at all temperatures. Increasing the concentration of oxidant in the atmosphere of combustion caused the reduction of the combustion time of all tested fuels.

Feasibility of producing biodegradable disposable paper cup from pineapple peels, orange peels and Mauritian hemp leaves with beeswax coating

While past studies have been carried out to form eco-friendly disposable tableware using non-wood biomass, there is no present groundwork so far where fruit peels waste composited with Mauritian hemp (Furcraea foetida) has been used for such purpose, which is novel to this research work. This study therefore assesses whether the production of 100% biodegradable disposable paper cups with acceptable strength properties using pineapple (Ananas comosus) peels, orange (Citrus sinensis) peels and Mauritian hemp as feedstock is feasible. Soda pulping followed by vacuum molding was done to produce hemp:pineapple peels and hemp:orange peels composite paper cups in different ratios. The cups were tested using relevant standards in terms of appearance and structure, burst strength, tensile strength, weight load, water leakage and biodegradability to find the optimum cup composition by comparing with a suitable control. All cups were visually conformant in terms of color and base stability. The 40:60 hemp–pineapple peels composite cup had characteristics closest to the control, with no cracks and variation rate of weight load, average thickness of 1.42 mm and burst and tensile indexes of 0.25 kPa m2/g and 3.30 Nm/g, respectively. Beeswax coating thickness of 0.70 mm on the optimum cup was adequate to retain cold water for 30 min (minimum) without any leakage. The cup also biodegraded completely in both active soil and damp sand environments within 5 and 6 weeks, respectively. Results therefore reveal that fiber extraction from fruit peel wastes and hemp leaves to produce eco-friendly, biodegradable disposable paper cups is viable.

Paper Production from Mauritian Hemp Fibres

The study examines the potential of Mauritian hemp (Furcraea foetida L.), a lignocellulosic non-wood biomass, as a more environmental friendly substitute to virgin wood for printing paper production. The best pulping method for Mauritian hemp was first investigated. A4 sized papers were then produced using 100% Mauritian hemp fibres and mixtures of Mauritian hemp fibres with Elephant grass fibres and wastepaper. Using Standard tests, the physical (thickness, grammage, apparent density, water absorbency) and mechanical (tensile strength, burst strength, crease recovery, abrasion resistance) properties of the papers produced were evaluated and compared with those of an 80 gsm A4 commercial printing paper used as control. Lastly, internal sizing was done by adding different proportions of starch to the paper whose properties were closest to the control (judged most printable) to investigate any property enhancement. Soda cooking with 12% Wt/V NaOH solution at a temperature of 90 °C for 90 min was found best for pulping Mauritian hemp. The 100% Mauritian hemp paper had characteristics closest to the control, with apparent density 141.54 kg/m3, water absorbency time 1.436 s, burst strength 0.323 kPa m2/g, tensile strength 10.97 Nm/g, abrasion resistance 37.5 cycles before rupture and crease recovery angle 34.8°. Increasing the starch content from 10 to 40% caused the 100% Mauritian hemp paper’s characteristics to increasingly approach those of the control, thus showing printability improvement. The methodologies adopted for papermaking and testing demonstrated that Mauritian hemp is a suitable alternative to wood to produce good quality printing paper.

Cellulose acetate production from paddy rice straw and oil palm empty fruit bunch: trichloroacetate catalyst

The utilization of non-wood biomass for fuels and chemicals production is widely studied in recent years. This paper reported the application of trichloroacetate as catalyst in the production of cellulose acetate from paddy (Oriza sativa) rice straw and oil palm (Elaeis guineensis) empty fruit bunch (EFB). Firstly, pre-treatment by using H2O in acidic condition was carried out prior to the soda pulping by using NaOH 10%, solid to liquid ratio 1:7. The pre-treatment and pulping aim to separate cellulose from lignin and hemicellulose. Furthermore, in order to purify the cellulose, bleaching was applied to the pulps by using NaClO2 0.5% and H2O2 10%. Finally, the paddy rice straw pulp and oil palm EFB pulp were subjected to the acetylation by using acetic anhydride as acetylating agent in CH3COOH condition with catalyst CCl3COOH and H2SO4. The analysis results by using Fourier-transform infrared spectroscopy showed that C=O stretching from cellulose acetate at around 1730 cm−1. Furthermore, the morphological surface and crystallinity of the raw materials and products was analysed by using scanning electron microscopy and X-ray diffraction, respectively. The acetylated cellulose diameter and cristallinity decreased after the acetylation reaction.

Trends in the production of cellulose nanofibers from non-wood sources

The rise of biomass-derived nanocellulose addresses the sustainability criteria now demanded of new materials, which have been widely overlooked in the plastics era—renewability, abundance, biodegradability, and recyclability. Cellulose nanofibers have conventionally been extracted from wood products, supported by an established forestry infrastructure, but the drive for biomass sustainability has encouraged researchers to explore non-wood sources over the past 15 years. Non-wood sources, including agricultural residues and industrial wastes, offer an attractive alternative due to their abundance, fast generation, and low starting value. Moreover, agricultural residues can improve the sustainability of cellulose nanofiber processing from multiple angles. The biochemical composition of the typical agricultural residue, which is lower in lignin and higher in hemicellulose than wood stems, improves the fibrillation efficiency of cellulose bundles into nano-scale fibers. In addition, agricultural residues yield high biomass volume from short growth cycles with improved land utilisation, whilst offsetting environmental issues associated with their current uses. In this work, we performed a comprehensive literature evaluation of the biomass sources used to produce cellulose nanofibers. Of the 3358 cellulose nanofiber publications from 2004 to 2018 with an identifiable source material, 57% were derived from wood-based biomass and 30% from non-wood biomass, with 100 unique biomass sources identified. Furthermore, the top research fields associated with non-wood publications included general characterisation (36%), plastic nanocomposites (19%), bionanocomposites (9%), biomedical products (8%), and electronic devices (6%). As social, political and economic drivers reinforce sustainability as a key focus in nanocellulose production, this bibliometric resource provides a timely snapshot of the sustainability trends in cellulose nanofiber research.

Production and characterization of lignin containing nanocellulose from luffa through an acidic deep eutectic solvent treatment and systematic fractionation

In this study, lignin and hemicelluloses were partially separated from non-wood biomass of luffa sponge using an acidic deep eutectic solvent (ADES) composed of choline chloride and oxalic acid dihydrate, and the obtained cellulose-rich residue was further disintegrated into lignin containing cellulose nanocrystal (OA-CNC) and nanofiber (OA-CNF) fractions with a two-step ultrasonication treatment. The ADES had a dual purpose: to produce fractions of biomass and to accelerate the nanofibrillation of cellulose. Under optimal reaction conditions (at 90 °C for 150 min), solid fractions with cellulose content of 76.4 wt% (initially 51.8 wt%) and residual lignin content of 10.7 wt% (initially 17.8 wt%) were achieved. Ultrasonication resulted in lignin containing nanocelluloses with a high total yield (59.1 wt% vs. 50.5 wt% from reference 60% sulfuric acid hydrolysis). They consisted mainly of elongated cellulose nanofibers (OA-CNF) with an average diameter of 28 nm. The OA-CNF were further converted to flexible and foldable self-standing films with tensile strength of 134 MPa and elongation at break of 10.6%. This simplified method also presents great potential for using biomass waste (e.g., wheat straw, branches, and sawdust) to produce lignin containing nanocellulose.

The influence of the oxidizing atmosphere on the mass loss of biomass pellets combusted in the inert material stream

Biomass is a renewable energy source with high growth potential due to wide availability around the world. Wood pellets are commonly used biomass for modern energy production, however, due to the growing demand, the issue of sustainable development has encouraged many entrepreneurs to produce pellets from non-wood biomass. On the one hand, the versatile nature of biomass enables its use in all parts of the world, on the other hand, this diversity makes biomass a complex and difficult fuel. Especially because of the high percentage of alkali (potassium) and chlorine in some types of biomass that can generate problems during combustion. The production and use of pellets from various types of biomass, therefore, opens up opportunities and challenges for existing technologies. In recent years, fluidized combustion technology has been considered as one of the main directions of development of professional energy in the world. Fluidized bed boilers also allow the implementation of the dynamically developing oxy-combustion technology, which perfectly fits the prevailing trends due to the key advantages of increased energy conversion, as well as the possibility of direct sequestration of carbon dioxide. During experimental research, the mass loss of individual biomass pellets of various origin combusted in a laboratory reactor with a circulating fluid layer under various conditions of the furnace chamber (oxidizing atmosphere and intensity of inert material stream) was analyzed. The obtained results allow stating that the large variety of biomass offered by suppliers requires a thorough knowledge of its properties and determination of its impact on the process and installations when used in the power industry.

Structural characterization of carboxyl cellulose nanofibers extracted from underutilized sources

Two different chemical methods, TEMPO-oxidation and nitro-oxidation, were used to extract carboxyl cellulose nanofibers (CNFs) from non-wood biomass sources (i.e., jute, soft and hard spinifex grasses). The combined TEMPO-oxidation and homogenization approach was very efficient to produce CNFs from the cellulose component of biomass; however, the nitro-oxidation method was also found to be effective to extract CNFs directly from raw biomass even without mechanical treatment. The effect of these two methods on the resulting cross-section dimensions of CNFs was investigated by solution small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The UV-Vis spectroscopic data from 0.1 wt% TEMPO-oxidized nanofiber (TOCNF) and nitro-oxidized nanofiber (NOCNF) suspensions showed that TOCNF had the highest transparency (> 95%) because of better dispersion, resulted from the highest carboxylate content (1.2 mmol/g). The consistent scattering and microscopic results indicated that TOCNFs from jute and spinifex grasses possessed rectangular cross-sections, while NOCNFs exhibited near square cross-sections. This study revealed that different oxidation methods can result in different degrees of biomass exfoliation and different CNF morphology.

Evaluation of high purity cellulose production from pretreated various agricultural biomass wastes

Four kinds of non-wood biomass were studied as raw material for high purity cellulose production. Cajuput (Melaleuca Leucadendron) twigs, sugarcane (Saccharum officinarum) bagasse, oil palm (Elaeis guineensis) empty fruit bunch and rice (Oryza sativa) straw were treated by NaOH 1 % at boiling temperature and atmospheric pressure for 2 h. The surface structure of these materials and chemical modification of cellulose, hemicellulose, and lignin during the treatment were analyzed. The result showed that the highest cellulose increasing was from 29.6 to 62.7% for rice straw. Meanwhile, the highest and the lowest cellulose content after treatment were 69.7% for sugarcane bagasse and 48.0% for cajuput, respectively. Scanning electron microscopy (SEM) image showed that the smoother surface for all biomass after pre-treatment.

Understanding the Effect of Machine Technology and Cellulosic Fibers on Tissue Properties – A Review

Hygiene tissue paper properties are a function of fiber type, chemical additives, and machine technology. This review presents a comprehensive and systematic discussion about the effects of the type of fiber and machine technology on tissue properties. Advanced technologies, such as through-air drying, produce tissue with high bulk, softness, and absorbency. Conventional technologies, where wet pressing is used to partially dewater the paper web, produces tissue with higher density, lower absorbency, and softness. Different fiber types coming from various pulping and recycling processes are used for tissue manufacturing. Softwoods are mainly used as a source of reinforcement, while hardwoods provide softness and a velvet type surface feel. Non-wood biomass may have properties similar to hardwoods and/or softwoods, depending on the species. Mechanical pulps having stiffer fibers result in bulkier papers. Chemical pulps have flexible fibers resulting in better bonding ability and softness. Virgin fibers are more flexible and produce stronger and softer tissue. Recycled fibers are stiffer with lower bonding ability, yielding products that are weaker and less soft. Mild mechanical refining is used to improve limitations found in recycled fibers and to develop properties in virgin fibers. At the same time that refining increases strength, it also decreases bulk and water absorbency.

Silica Retention by the Addition of Sodium Metaaluminate During the Impregnation Stage of Bamboo Kraft Pulping

Bamboo is the most utilized non-wood biomass in China. One of its most important applications is in the pulp and paper industry. In such an application, one of the significant challenges is decreasing the silica dissolution in the pulping process. In this study, the use of sodium metaaluminate (NaAlO2) to decrease the silica dissolution into liquor was investigated. The results showed that an alkali-resistant Si–Al coating layer was formed onto the silica particles by the addition of NaAlO2. Under the impregnation conditions, NaAlO2 reacted with Na2SiO3 and produced poly-condensated Si/Al compounds, which are insoluble under kraft pulping conditions. It was found that the silicon retention in bamboo chips was 90% with the addition of NaAlO2 under the conditions studied. This novel silica-retaining technology has a great potential for industrial applications.