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Bamboo engineering materials are made from abundant raw material sources and can be easily prepared with minimal processing and low pollution. However, when used as structural materials, they are limited by their weight, strength, and lack of stable designability. The use of laminated structure and a gluing interface are key factors affecting the performance of bamboo engineering materials. Bamboo exhibits excellent toughness and strength when resisting external forces, with a multi-level interlocking reinforced interface with bamboo's intercellular layer that induces an increase in crack deflection paths (internal toughening) and cell wall energy consumption (external toughening) coupled to microfibril pulling out. Inspired by the functionally graded structure of the lightweight and high-strength bamboo wall layer and the interlocking reinforced interface between vascular bundles and parenchyma cells, we designed a high-performance bamboo engineering material designed to imitate bamboo, Imitation Bamboo Bundle Laminated Veneer Lumber (IBLVL), prepared by uniform lamination and gradient molding. The designed IBLVL is light in weight, with high strength and uniform density. This work demonstrates the feasibility of using resource-rich and sustainable bamboo to manufacture light-weight bamboo engineering materials with high strength and high toughness that can be substituted for non-renewable resources in the fields of construction and transportation. • Explains the mechanism of the excellent properties of bamboo itself. • IBLVL is designed to imitate bamboo features. • IBLVL has excellent strength, toughness and dimensional stability. • The mechanism of the excellent performance of IBLVL revealed. [ABSTRACT FROM AUTHOR]

Bamboo holds great promise as a versatile material in construction and engineering. However, its inherent hydrophilic nature, particularly within its cell walls, presents challenges for dimensional stability, limiting its widespread use. Addressing this challenge, vapor phase furfurylation (VPF) has emerged as a promising technique for bamboo modification. In this study, we applied VPF to bamboo for the first time, resulting in a significant transition towards hydrophobicity and a remarkable enhancement in dimensional stability (ASE > 50 %). Employing a multifaceted approach, we investigated the distribution gradient and penetration depth of FA resin within furfurylated bamboo using advanced methodologies such as scanning electron microscopy (SEM), nanoindentation, dynamic vapor sorption (DVS), and imaging FT-IR microscopy, demonstrating the improvement in dimensional stability is attributed to cell wall bulking from FA resin infiltration. Through meticulous parameter refinement, we identified an optimized protocol comprising 40 h of VPF exposure, a VPF temperature of 115 °C, and a 4.5 % concentration of maleic anhydride (MA). This tailored VPF methodology holds promise for enhancing the dimensional stability of bamboo while minimizing FA consumption, thus expanding its potential applications in construction and furniture industries. • A high-stable bamboo was prepared by a novel VPF modification with low-resin load. • FA resin penetrates into bamboo with a graded distribution after VPF modification. • The VPF process reduces FA usage and energy compare with traditional furfurylation. [ABSTRACT FROM AUTHOR]

Understanding the distribution and accessibility of polymers within plant cell walls is crucial for addressing biomass recalcitrance in lignocellulosic materials. In this work, Imaging Fourier Transform Infrared (FTIR) and Raman spectroscopy, coupled with targeted chemical treatments, were employed to investigate cell wall polymer distribution in two bamboo species at both tissue and cell wall levels. Tissue-level Imaging FTIR revealed significant disparities in the distribution and chemical activity of cell wall polymers between the fibrous sheath and fibrous strand. At the cell wall level, Imaging Raman spectroscopy delineated a distinct difference between the secondary wall and intercellular layer, with the latter containing higher levels of lignin, hydroxycinnamic acid (HCA), and xylan, and lower cellulose. Mild acidified sodium chlorite treatment led to partial removal of lignin, HCA, and xylan from the intercellular layer, albeit to a lesser extent than alkaline treatment, indicating susceptibility of these polymers to chemical treatment. In contrast, lignin in the secondary wall exhibited limited reactivity to acidified sodium chlorite but was slightly removed by alkaline treatment, suggesting stable chemical properties with slight alkaline intolerance. These findings provide valuable insights into the inherent design mechanism of plant cells and their efficient utilization. In this work, the application of Imaging FTIR and Raman spectroscopy, in conjunction with chemical treatments, provided valuable insights into the distribution and accessibility of polymers in bamboo from two distinct species at both tissue and cell wall levels. Specifically, alkaline treatment demonstrated higher sensitivity towards lignin and HCA, particularly within the intercellular layer, suggesting a preferential removal of ester bonds. Conversely, acidified sodium chlorite treatment primarily targeted lignin within the secondary wall, indicating differential reactivity based on the chemical composition and structure of the target polymers. This insight not only enhances our understanding of bamboo's chemical properties but also informs the selection of appropriate processing methods for biorefinery applications. The visualization of chemical treatment on cell wall has reference significance for multiple chemical engineering technologies. [Display omitted] [ABSTRACT FROM AUTHOR]

Biomass recalcitrance, a key challenge in biomass utilization, is closely linked to the architectural composition and cross-linkages of molecules within cell walls. With three bamboo species investigated, this study aims to elucidate the inherent molecular-scale structural differences between bamboo fibers and parenchyma cells through a systematic chemical extraction and structural characterization of isolated hemicelluloses, lignin, and lignin-carbohydrate complexes (LCC). We observed that parenchyma cells exhibit superior alkaline extractability compared to fibers. Additionally, we identified the hemicelluloses in parenchyma cells as L-arabino-4- O -methyl-D-glucurono-D-xylan, displaying a highly branched structure, while that in fibers is L-arabino-D-xylan. Furthermore, the parenchyma cell lignin exhibited a higher syringyl-to-guaiacyl (S/G) ratio and β- O -4 linkage content compared to fibers, whereas fibers contain more carbon‑carbon linkages including β-β, β-5, and β-1. This notable structural difference suggests a denser and more stable lignin in bamboo fibers. Importantly, we found that LCC in parenchyma cells predominantly comprises γ-ester linkages, which exhibit an alkaline-unstable nature. In contrast, fibers predominantly contain phenyl glycoside linkages, characterized by their alkaline-stable nature. These findings were observed for all the tested bamboo species, indicating the conclusions should be also valid for other bamboo species, suggesting the competitiveness of bamboo parenchyma cells as a valuable biofuel feedstock. Note: In this work, based on analysis on bamboo lignin, hemicelluloses and LCC, the cell wall deduction pattern of bamboo fibers, characterized by alkaline-stable nature, and parenchyma cells, featured as alkaline-stable nature, was firstly established. The study presented here lays a foundation for future research aimed at optimizing the utilization of bamboo parenchyma cells for sustainable biorefinery applications. [Display omitted] • Bamboo parenchyma cells exhibit superior alkaline extractability than bamboo fibers. • Differences in fibers and parenchyma were found on lignin, hemicelluloses and LCC. • Bamboo parenchyma cells are a valuable biofuel feedstock for bioethanol production. [ABSTRACT FROM AUTHOR]

Developing high-performance plant fiber-reinforced thermoplastic polymer composites using environmentally friendly and cost-effective methods remains a significant challenge. In this study, we present a novel micro-nano strategy for producing robust short bamboo fibers (BFs) reinforced polypropylene (PP) composites (SBFPCs) without the need for chemical modification. Our approach involves the utilization of purified short micron BFs, which is surface-coated with holocellulose nanofibers (HNFs) extracted from bamboo parenchyma cells (BP). Through conventional injection processing, the resulting SBFPCs demonstrate remarkable mechanical enhancements with just a 0.2 wt% addition of HNFs compared to control samples. Notably, the mechanical properties of our SBFPCs surpass those of most reported short plant fiber-reinforced thermoplastic composites. The superior mechanical performance of our SBFPCs can be attributed to several factors, including the use of purified micron BFs with optimal aspect ratios as the primary reinforcement phase, enhanced interfacial mechanical interlocking between BFs and the PP matrix facilitated by the addition of HNFs, and the potential dispersion of HNFs within the PP matrix at submicron or nanoscale as a secondary reinforcement phase. This study highlights the promising application of SBFPCs in engineering areas with stringent mechanical requirements. [ABSTRACT FROM AUTHOR]

Lignin is widely recognized as a key factor influencing the recalcitrance of lignocellulosic biomass, yet the specifics of this relationship remain complex and not fully understood due to the complex interplay between lignin content variation and cell wall structure. Bamboo, which exhibits greater recalcitrance compared to wood in biorefinery processing, was chosen as the focus of investigation in this study. Three variants of Dendrocalamus farinosus with high, middle and low lignin contents were systematically analyzed and compared, in terms of molecular structure of lignin, hemicelluloses and cellulose, cell wall polymer spatial orientation, lignin-carbohydrate complex (LCC) linkages, cell wall geometrical size, as well as deconstruction efficiency, including delignification, alkaline extraction, and cellulose enzymatic hydrolysis efficiency. Findings reveal that an increase in lignin content generally lowers bamboo's deconstruction efficiency, but the mechanisms are more nuanced than previously thought. While lignin content variations do not significantly affect the molecular structure of xylan, cellulose and the chemical linkage type of LCC linkages, they do impact cellulose crystallinity, xylan orientation and notably, the thickness of fiber cell wall in the free fiber stands of bamboo. These findings highlight that lignin's role extends beyond mere physical protection of the cell wall, but also induces subtle variations in polymer structure and cell wall morphologies, which collectively influence the deconstruction efficiency of bamboo cell walls. [ABSTRACT FROM AUTHOR]

• The detection model realizes identifying, positioning, and counting intelligently. • The number of vascular bundles in bamboo grown in different areas is 7196 ± 698. • The differences result from the culm dimension and the growing environment. • From the base to top, the number of vascular bundles decreased from 8000 to 300. • Vascular bundles in node decrease mainly due to the Type 2 & 3 vascular bundles. The vascular bundle is the most important structural unit of bamboo that determines the growth of bamboo and the properties of bamboo-based materials. A systematic understanding of the characteristics of vascular bundle is the key to clarify the structure-property relationship of bamboo. In this paper, the YOLO (You Only Look Once) algorithm was applied to the field of bamboo structure and a detection model was proposed to solve the key technical problems regarding automatic detection, positioning, counting, and automatic measurement of relevant parameters of vascular bundles. The precision of the detection model was up to 99.59 %, and able to achieve the work in minutes that cannot be done manually. Furthermore, we studied the variation of inter-plant and the variation of axial direction of Moso bamboo [ Phyllostachys edulis (Carr)H. de Lebaie]. The results indicated that the total number of vascular bundles of Moso bamboo from 12 different areas was 7196 ± 698, the distribution density of vascular bundles was 2.49 ± 0.58 per mm2, the fiber volume fraction was 23.68 ± 1.89 %. The apparent differences of vascular bundles in different areas result from the growing environment. There were approximately 8000 vascular bundles in the base of Moso bamboo while the number decreased to around 300 at the top, and the decreased vascular bundles were mainly semi-open type and open type. The total area of fiber sheath decreased linearly from base to top of internodes, while the fiber volume fraction was 20–30 % constantly. [ABSTRACT FROM AUTHOR]

Highlights • Hydrophobic and compressible CNF aerogel are prepared by a facile synthesis method combing aqueous silylation and freeze-casting. • The hydrophilicity and fragility of CNF aerogel were simultaneous addressed without requiring any post-treatments. • Freeze-casted silylated aerogel exhibited direction-dependent structure and compression properties. Abstract Cellulose aerogels have shown outstanding potential as renewable functional materials; however, their practical applications are still limited by inherent hydrophilicity and weak mechanical properties. To overcome hydrophilicity and fragility issues of aerogels, in this study, silylated bamboo-derived cellulose nanofibrils (CNF) aerogels with aligned porous structures were achieved by directionally freeze-casting a mixture of CNF suspension and methyltrimethoxysilane sol. The silylated CNF aerogels exhibited distinct aligned lamellar structures and significantly anisotropic mechanical properties. They had improved strength and stiffness in the axial direction (along the freezing direction) and excellent rapid shape recovery ability in the radial direction (perpendicular to the freezing direction) with a significant high shape recovery ratio of 92% after 100 cycles at 80% compression. Owing to their ultra-low density, hydrophobicity, and high compressive recoverability, the silylated CNF aerogels can be potentially used in a wide range of industrial applications, such as hydrophobic polymer nanocomposites, absorbents, and biomedical scaffolds. [ABSTRACT FROM AUTHOR]

The pore structure of the cell wall is closely related to biomass recalcitrance. Bamboo fibers and parenchyma cells constitute the main body of bamboo but have significantly different chemical decomposition efficiencies. This study compared the influence of chemical removal on the porosity, pore size distribution, and hygroscopicity of fibers and parenchyma cells in bamboo. The results exhibited that parenchyma cells were more porous and hygroscopic as compared to fibers. However, both cell types exhibited similar changes during sequential chemical removal. The removal of extractives produced many more micropores than mesopores in the cell walls, which were mainly concentrated in the size ranges of 0.4–1.0 nm and 2–10 nm. Delignification reduced both the cell wall porosity and micropore volume, which was attributed to the easy collapse of delignified cell walls in powder samples, as well as the disappearance of micropores in lignin. Several mesopores with a diameter of 2–10 nm were created upon removing hemicellulose after delignification, but almost all micropores disappeared. Changes in the porosity and chemical compositions synergistically affected the water sorption and hysteresis of bamboo. The delignified samples contained more exposed sorption sites, which displayed stronger dynamic water vapor sorption. After removing hemicellulose, the sample exhibited lower water sorption, primarily due to a reduction in the number of sorption sites. The absorption hysteresis of bamboo decreased upon decreasing the cell wall porosity. • Cell wall pore structures are related to chemical removal and specific cell types in bamboo. • Removal of lignin and hemicellulose reduced cell wall porosity of bamboo. • There is a good correlation between moisture sorption hysteresis with cell wall porosity. [ABSTRACT FROM AUTHOR]

Mainly composed of fibers and parenchymal cells with strikingly different chemical compositions and cell wall structures, bamboo represents an important alternative resource for bio-refinery. Therefore, this study proposes a potentially novel, low-energy consumption approach for producing high-quality nanocellulose fibrils (NCFs) made from bamboo at large scale. For this purpose, bamboo pulping sheets (mainly composed of fibers) and bamboo processing residues (mainly composed of parenchymal cells) were chosen as starting materials from which NCFs were isolated with a simple high-pressure homogenization process. Wet chemical analysis, Scanning Electron Microscope (SEM), and microtensile tests were applied to investigate the effects different cell types had on the properties of prepared NCFs, as well as the amount of energy required to produce them. The results show that the energy required for isolating NCFs from parenchymal cells was significantly lower than that from bamboo fibers, while the quality of NCFs produced from the two types of cells were similar. In addition to the relative ease of the procedure and the low-energy required, as bamboo processing residues produced in a number of industrial bamboo applications normally contain a high ratio of parenchymal cells and can be obtained at relatively low costs, this represents a very promising source of raw material for the production of NCFs. [ABSTRACT FROM AUTHOR]

Bamboo fibers are known for their outstanding mechanical properties and could be a potential replacement for synthetic fibers used in fiber-reinforced composites. In this paper, mechanical variation related to age for elementary fibers of two important sympodial bamboo species ( Dendrocalamopsis oldhami and Dendrocalamus latiflorus Munro) was analyzed using a microtension technique. From the investigation of elementary fibers ranging from 1 to 6 years in age, our results showed the average tensile modulus of the two types of bamboo fibers ranged from 42.84 GPa to 44.29 GPa and 33.51 GPa to 37.35 GPa, whereas the tensile strength ranged from 1.50 GPa to 1.70 GPa and 1.34 GPa to 1.52 GPa, respectively. These values are significantly higher than equivalent properties found in most natural plant fibers. Furthermore, bamboo fibers were found to have nearly reached their optimal mechanical properties after just 1 year, with subsequent variations in older fibers proving statistically insignificant. This highlights the suitability of using young bamboo fibers as the reinforcing phase in polymer composites. [ABSTRACT FROM AUTHOR]

The mechanical performance and dimensional stability of bamboo is highly dependent on the microfibril orientation in its cell wall sublayers. However, a comprehensive and quantitative description of this orientation at the sublayer scale of cell wall is very challenging to do. Here, we proposed a new approach to quantitatively estimate the cellulose microfibril orientation across the whole cell wall of both fibers and parenchyma cells in bamboo. This new approach is based on the geometrical correlation between the actual and apparent dimensions of cellulose microfibril aggregates, which are respectively determinedly with CP/MAS 13C NMR and high-resolution field emission scanning electron microscopy (FE-SEM). For comparison, the average microfibril angle (MFA) of both fibers and parenchyma cells were also measured using X-ray diffraction (XRD). It was concluded that the cellulose microfibrils in the broad sublayers of the bamboo fibers exhibited a relatively small MFA of about 10°, while those in the narrow sublayers were nearly oriented in the transverse with a MFA of about 80°. For parenchyma cells, the MFA of the broad and narrow sublayers were estimated to be 50–70° and 70–80°, respectively. Modified cell wall structural models for the two types of cells were then proposed. • Microfibril orientation of bamboo at cell wall sub-layers were estimated using a new method. • Microfibril angle in narrow sublayers of bamboo fibers is about 80º. • The broad sublayers of bamboo fibers has a small microfibril angle of about 10º. • Microfibril angle of parenchyma cells is much larger than that of fibers. [ABSTRACT FROM AUTHOR]

Biomass recalcitrance is believed to be related to the hierarchical and heterogeneous structures of plant cell walls. In this study, the alkaline extraction efficiency of bamboo fibers and parenchyma cells is found to be highly related to their structural differences on both anatomical and molecular level. Advanced NMR spectroscopy demonstrated the lignin and hemicelluloses (mainly xylan) from fibers and parenchyma cells are significantly different in their molecular structure. The parenchyma lignin contains more β- O -4 linkages with much higher syringyl/guaicyl (S/G) ratio. By contrast, the fiber lignin contains more stable β-β and β-5 linkages as compared to parenchyma lignin. Although the hemicelluloses from both bamboo fibers and parenchyma cells shows similar molecular structure of L -arabino-4- O -methyl- D -glucurono- D -xylan, the latter contains more 4- O -methyl-α- D -glucuronic acid units. These structural discrepancies can provide explanations why the parenchyma cells have much higher "alkaline extraction efficiency" than fibers, further indicating the former is a promising feedstock in the current biorefinery scenario. Bamboo dominantly consists of stiff sclerenchyma fibers (account for 40% by volume) and soft matrix parenchyma cells (account for 52% by volume). Solution-state 2D heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) demonstrated that bamboo parenchyma cells lignin has a higher S/G ratio and more β- O -4 substructures, but lower content of β-β and β-5 linkages, which contribute to a relatively high reactivity under alkaline treatment. Bamboo parenchyma cells, with both the unconsolidated cell structure and the instable macromolecule structure, could be regarded as a highly competitive "easy bio-conversion" materials. [Display omitted] • Bamboo fibers and parenchyma cells exhibits distinct differences at both anatomical and molecular levels. • Parenchyma cells are easier to be extracted by alkali than fibers. • Lignin in parenchyma cells contained more β- O -4 linkage with higher S/G ratio. • Bamboo parenchyma cells are ideal easily-converted feedstock. [ABSTRACT FROM AUTHOR]

Abstract: Rice straw pellets are the main type of biomass solid fuel and have great potential as a bioenergy resource of the future in China. But it also showed important problems because of its high content of ashes and its low gross calorific value, reducing the possibility to be used in domestic heating. It was certified that mixing different types of biomass materials was helpful to improve the properties of pellets. To improve properties of rice straw pellets and investigate the effect of mixing bamboo and rice straw on the pellet properties, some properties of pellets, manufactured using different mixing ratio of bamboo and rice straw particles, were determined in this research. It can be concluded from this research that physical properties of all pellets meet the requirements of Pellet Fuels Institute Standard Specification for Residential/Commercial Densified except for bulk density of pellets, manufactured using mixing ratio (≤3:2) of bamboo and rice straw. The inorganic ash and gross calorific value of rice straw pellets cannot meet the requirement of Pellet Fuels Institute Standard Specification for Residential/Commercial Densified (8.0%) and the minimum requirement for making commercial pellets of DIN 51731 (>17,500 J/g). Both properties are improved through mixing bamboo particles and rice straw particles. It is significant that inorganic ash content and gross calorific value of pellets, manufactured using mixing ratio (≥3:2) of bamboo and rice straw, were lower than 8.0% and higher than 17,500 J/g, respectively. This also shows that mixing different biomass materials is an effective way to optimize properties of biomass solid fuel. All pellets after improvement are proposed as biomass solid fuel and have the potential to be developed as commercial pellets on an industrial scale in China. [Copyright &y& Elsevier]

To better understand the high recalcitrance of bamboo during bioconversion, the fine spatial distribution of polymers in bamboo was studied with Imaging FTIR microscopy under both transmission and ATR modes, combined with PCA data processing. The results demonstrated that lignin, xylan and hydroxycinnamic acid (HCA) were more concentrated in the fibers near the xylem conduit, while cellulose was evenly distributed across the whole fiber sheath. PCA processing produced a clear separation between bamboo fibers and parenchyma cells, indicating that the parenchyma cells contains more pectin and HCA than fibers. It also demonstrated that cellulose, xylan and S-lignin were concentrated most heavily in bamboo fiber secondary cell walls, while G-lignin, pectin and HCA were found more in the compound middle lamella. The revealed information regarding polymer distribution is of great significance for better understanding of the inherent design mechanism of plant cell wall and its efficient utilization. Imaging FTIR with ATR first demonstrated that for bamboo, in similarity with wood species, the spatial distribution of cellulose, xylan and S-lignin were concentrated most heavily in the fiber secondary cell walls, while G-lignin, pectin and hydroxycinnamic acid (HCA) were found more in the compound middle lamella. At the tissue level, imaging FTIR with transmission mode first demonstrated that lignin, xylan and HCA were more concentrated in the fibers near xylem conduit, while cellulose was evenly distributed across the whole fiber sheath. [Display omitted] • The polymers distribution in bamboo at both tissue and cellular scale was revealed with Imaging FITR • Xylan and lignin were found to be more concentrated in the fibers near the xylem conduit in bamboo • Cellulose, xylan and S-lignin were more concentrated in the secondary wall [ABSTRACT FROM AUTHOR]

• A surface furfurylation was studied to improve the dimensional stability and durability of bamboo. • The dimensional stability and durability of bamboo have significant increase with a low WPG. • The mechanical properties did not decrease after surface furfurylation. • A starting processing parameters was proposed for the simple surface furfurylation. Furfurylation has long been adopted for wood modification, and found to be effective for bamboo as well. However, traditional full impregnation furfurylation would reduce the dimensional stability of bamboo although its biological durability was improved. Here, we found surface modification with furfuryl alcohol (surface furfurylation) was particularly suitable for bamboo, which is extremely hard to be treated due to its low transverse mass transportation. To optimize the surface furfurylation process for bamboo, an orthogonal experiment was designed with several key physical and mechanical properties tested, including weight percent gain (WPG), equilibrium moisture content (EMC), anti-swelling efficiency (ASE), modulus of rupture (MOR), modulus of elasticity (MOE). Using this process, dimensionally stable (ASE could reach as high as 50% by volume) and highly biological durable (strong resistance against mould, decay and termite) bamboo material with low consumption of furfuryl alcohol (FA) (average WPG lower than 15%) were prepared avoiding significant reduction in mechanical properties. Furthermore, a parameter combination of 70% FA concentration, 105 ℃ curing temperature, and 5 h curing time was proposed as an optimized process for pilot-scale production based on orthogonal experiments and range analysis. [ABSTRACT FROM AUTHOR]

• Furfurylation was demonstrated for the first time to be highly efficient for bamboo modification due to the high permeability of furfural alcohol (FA). • The modified bamboo was found to be highly resistant to mold, decay fungi and termites with low FA weight percentage gain (WPG). • The mechanical properties of furfurylated bamboo could be moderately enhanced at low FA concentrations. Bamboo is an important sustainable material for construction industry due to its combined advantages of easy availability, fast renewability, and excellent mechanical performance. However, its low biological durability and poor treatability limit its use for structural and outdoor building material. In this study, highly durable bamboo materials were prepared through a facile modification process called bulk furfurylation for the first time. The modified bamboo was found to be highly mold resistant and exhibited strong resistance to decay fungi and termites with a furfuryl alcohol (FA) weight percentage gain (WPG) as low as 10%. A strong positive correlation was detected between WPG and termite resistance, but not for mold or decay resistance. The mechanical properties of the furfurylated bamboo were moderately enhanced at low FA concentrations and were much less affected by curing temperature and time. Based on these results, it is concluded the furfurylated bamboo would have wide application in construction. [ABSTRACT FROM AUTHOR]