Biomass Components Research Articles

Perspective on Lignin Conversion Strategies That Enable Next Generation Biorefineries.

The valorization of lignin, a currently underutilized component of lignocellulosic biomass, has attracted attention to promote a stable and circular bioeconomy. Successful approaches including thermochemical, biological, and catalytic lignin depolymerization have been demonstrated, enabling opportunities for lignino-refineries and lignocellulosic biorefineries. Although significant progress in lignin valorization has been made, this review describes unexplored opportunities in chemical and biological routes for lignin depolymerization and thereby contributes to economically and environmentally sustainable lignin-utilizing biorefineries. This review also highlights the integration of chemical and biological lignin depolymerization and identifies research gaps while also recommending future directions for scaling processes to establish a lignino-chemical industry.

Interaction Effects between the Main Components of Protein-Rich Biomass during Microwave-Assisted Pyrolysis.

The interaction effects between the main components (proteins (P), carbohydrates (C), and lipids (L)) of protein-rich biomass during microwave-assisted pyrolysis were investigated in depth with an exploration of individual pyrolysis and copyrolysis (PC, PL, and CL) of model compounds. The average heating rate of P was higher than those of C and L, and the interactions in all copyrolysis groups reduced the max instant heating rate. The synergistic extent (S) of PC and PL for bio-oil yield was 16.78 and 18.24%, respectively, indicating that the interactions promoted the production of bio-oil. Besides, all of the copyrolysis groups exhibited a synergistic effect on biochar production (S = 19.43-28.24%), while inhibiting the gas generation, with S ranging from -20.17 to -6.09%. Regarding the gaseous products, apart from H2, P, C, and L primarily generated CO2, CO, and CH4, respectively. Regarding bio-oil composition, the interactions occurring within PC, PL, and CL exhibited a significantly synergistic effect (S = 47.81-412.96%) on the formation of N-heterocyclics/amides, amides/nitriles, and acids/esters, respectively. Finally, the favorable applicability of the proposed interaction effects was verified with microalgae. This study offers valuable insights for understanding the microwave-assisted pyrolysis of protein-rich biomass, laying the groundwork for further research and process optimization.

Study on mechanism of supercritical water gasification of hemicellulose for hydrogen-rich syngas based on experiments and reaction molecular dynamics simulations

Hydrogen-rich syngas from supercritical water gasification (SCWG) of renewable biomass is a promising technology. However, the mechanistic studies related to experiments and simulations on hemicellulose, an important component of biomass, are still limited. Therefore, in this study, the SCWG mechanism of hemicellulose was investigated using a batch reactor and via ReaxFF molecular dynamics simulations. The results indicated that the long chains of xylan broke to short chains during the heating process, which was accompanied by the occurrence of ring-opening reactions. SCWG occurred more completely with increasing temperature or decreasing concentration, when hydrogen was more selective and methane was produced mainly by gas reforming reactions. At 600 °C and 5 g/100 g water, the total gas yield of xylan SCWG was 38.65 mmol g−1, and the hydrogen yield could reach 14.48 mmol g−1. The liquid products mainly included furfural and phenol. The solid products consisted of a high C content, which could reach more than 90 % at 500 °C, and were dominated by polycyclic aromatic hydrocarbons, and at 600 °C by benzene and naphthalene. Xylan formed carbon balls on the surface of the solid products, while hemicellulose exhibited the formation of a dense porous structure.

The Catalytic Effect of Pt on Lignin Pyrolysis: A Reactive Molecular Dynamics Study

Lignin is the second-largest renewable resource in nature, second only to cellulose. Lignin is one of the most significant components of biomass, and it determines the behaviour of biomass in many thermochemical processes. However, limited studies have focused on the influence of metal catalysts on lignin pyrolysis. This study aims to develop a sustainable lignin catalytic pyrolysis technology to improve biomass energy-conversion efficiency, reduce dependence on fossil fuels, and promote the development of clean energy. In this study, the impact of Pt catalyst on the pyrolysis process of hardwood lignin was simulated by using reactive force field (ReaxFF) molecular dynamics. Through the comparison of the system without catalysts, the catalyst exhibited evident attraction to lignin macromolecules, prompting their decomposition at lower temperatures. Additionally, the catalyst has the strongest adsorption capacity for H radical. The activation energy of the reaction was calculated by kinetic analysis. It was found that the addition of catalysts significantly reduced the activation energy of the reaction. By revealing the effect of Pt catalyst on the lignin pyrolysis process, it provides a theoretical basis for biomass pyrolysis and the utilization of metal catalysts in industry.

Adsorption of Ni(II) from Aqueous Media on Biodegradable Natural Polymers—Sarkanda Grass Lignin

Heavy metals are pollutants that pose a risk to living systems due to their high toxicity and ability to accumulate and contaminate. This study proposes an alternative approach to the static adsorption of Ni(II) from aqueous media using Sarkanda grass lignin crystals, the non-cellulosic aromatic component of biomass, as an adsorbent substrate. To determine the best experimental conditions, we conducted tests on several parameters, including the initial and adsorbent solution pH, the concentration of Ni(II) in the aqueous solution, the amount of adsorbent used, and the contact time at the interface. The lignin’s adsorption capacity was evaluated using the Freundlich and Langmuir models to establish equilibrium conditions. The Lagergren I and Ho–McKay II kinetic models were used to determine the adsorption mechanism based on surface analyses and biological parameters such as the number of germinated seeds, energy, and germination capacity in wheat caryopses (variety Glosa) incorporated in the contaminated lignin and in the filtrates resulting from phase separation. The results suggest that Sarkanda grass lignin is effective in adsorbing Ni(II) from aqueous media, particularly in terms of adsorbent/adsorbate dosage and interfacial contact time.

Production of Aromatic Hydrocarbons from Co-Hydropyrolysis of Biomass Components and HDPE with Application of Modified HZSM-5 Catalyst.

Experiments were conducted in this study on the co-hydropyrolysis of three components of biomass (cellulose, hemicellulose, and lignin) and HDPE by using SR-Pd/Trap-HZ-5 as catalyst. To control the variable, we use the same experiment conditions in co-hydropyrolysis: Si/Al ratio of 50, Pd load 1 %, catalyst to reactant ratio of 1 : 10, 1 MPa, 400 °C, reaction time 1 h. Use XRD, TEM, BET, and NH3-TPD to confirm catalyst successful synthesis; use pine sawdust (PW) co-hydropyrolysis with HDPE to analyse catalytic activity; and use GC/MS to characterize the chemical composition of the bio-oil from the co-hydropyrolysis of biomass components and HDPE. The results show that cellulose has a significant synergistic effect with aromatic hydrocarbon production, whose selectivity was 93.3 %; hemicellulose has a synergistic effect; aromatic selectivity can reach 75.1 %; and a negative synergistic effect between lignin and HDPE was shown as the selectivity of aromatic hydrocarbons decreased from 62.1 % to 15.6 %.

Responses of stem growth and canopy greenness of temperate conifers to dry spells

Dry spells strongly influence biomass production in forest ecosystems. Their effects may last several years following a drought event, prolonging growth reduction and therefore restricting carbon sequestration. Yet, our understanding of the impact of dry spells on the vitality of trees' above-ground biomass components (e.g., stems and leaves) at a landscape level remains limited. We analyzed the responses of Pinus sylvestris and Picea abies to the four most severe drought years in topographically complex sites. To represent stem growth and canopy greenness, we used chronologies of tree-ring width and time series of the Normalized Difference Vegetation Index (NDVI). We analyzed the responses of radial tree growth and NDVI to dry spells using superposed epoch analysis and further explored this relationship using mixed-effect models. Our results show a stronger and more persistent response of radial growth to dry spells and faster recovery of canopy greenness. Canopy greenness started to recover the year after the dry spell, whereas radial tree growth remained reduced for the two subsequent years and did not recover the pre-drought level until the fourth year after the event. Stem growth and canopy greenness were influenced by climatic conditions during and after drought events, while the effect of topography was marginal. The opposite responses of stem growth and canopy greenness following drought events suggest a different impact of dry spells on trees´ sink and source compartments. These results underscore the crucial importance of understanding the complexities of tree growth as a major sink of atmospheric carbon.

Inner-particle reaction mechanism of cellulose, hemicellulose and lignin during photo-thermal pyrolysis process: Evolution characteristics of free radicals

Based on the concentrated photo-thermal thermogravimetry analyzer (PT-TGA) reactor, the pyrolysis of the cellulose, hemicellulose and lignin with different ratios at 100 °C/min and 550–850 °C was performed. The interaction among the three components significantly reduced the reaction temperatures and increased the maximum weight loss rate. The cellulose/lignin interactions were the main reason for the increase of gas production, especially for the H2 production which reached 128.13 mL/g biomass, much higher than the calculated value of 75.35 mL/g biomass without considering the interactions. What occurred during the co-pyrolysis of cellulose/lignin was the combination of free radicals without consuming the hydrogen radicals, while the formation of chemicals in others’ interactions integrated with the hydrogen radicals inhibited the production of H2 at high temperatures. For full-component pyrolysis, the yield of C-containing gas can be calculated by adding a coefficient of interaction between two components, indicating that the effect of the three-component interaction was much lower than that of the two-component. This study established the interaction mechanism for the three components of biomass during photo-thermal pyrolysis based on free radicals.

Recrystallization of Cellulose, Chitin and Starch in Their Individual and Native Forms.

Semi-crystalline natural polymers are involved in many technological processes. Biopolymers having identical chemical compositions can differ in reactivity in heterogeneous transformations depending on their crystal structure (polymorphic modification). This paper compares the crystal structure recrystallization processes occurring in natural polysaccharides (cellulose, chitin, and starch) in the individual form and as a component of native biomass. Aqueous treatment of pre-amorphized semi-crystalline biopolymers was shown to result in swelling, thus alleviating the kinetic restrictions imposed on the restoration of crystalline regions and phase transition to the thermodynamically more stable polymorphic modification. During recrystallization, cellulose I in the individual form and within plant-based biomass undergoes a transition to the more stable cellulose II. A similar situation was demonstrated for α- and β-chitin, which recrystallize only into the α-polymorphic modification in the case of both individual polymers and native materials. Recrystallization of A-, B-, and C-type starch, both in the individual form and within plant-based flour, during aqueous treatment, results in a phase transition, predominantly to the B-type starch. The recrystallization process depends on the temperature of aqueous treatment; longer treatment duration has almost no effect on the recrystallization degree of polymers, both in the individual form and within native materials.

Effect of Biochar Using N, P, and K Fertilisers on Growth and Quality of Lithocarpus litseifolius

Objective: In this study, we aimed to investigate the effects of facile combinations of biochar and N, P, and K fertilisers on the growth and physiological characteristics of Lithocarpus litseifolius seedlings, and to optimise the biochar/NPK ratio of Lithocarpus litseifolius. Method: A four-factor three-level orthogonal method was used to conduct a field experiment using 2-year-old Lithocarpus litseifolius. Nine fertiliser treatments and one control treatment (CK, i.e., no fertiliser) were established in a completely randomised block group with six replications of ten treatments. The plants were planted in October 2020 and harvested in November 2021, and fertiliser was applied once in April 2021 and once in July 2021. Results: Rational application could effectively promote the growth of Lithocarpus litseifolius, and T4(C2N1P2K3) produced the highest increase in plant height growth (17.03 cm), diameter growth (5.47 mm), soluble sugar (94.60 mg/g), soluble protein (4.59 mg/g), and phlorizin (old leaf: 16.00%; tender leaf: 15.13%); T8(C3N2P1K3) resulted in the highest chlorophyll a content (1.46 mg/g), chlorophyll b content (0.62 mg/g), and total chlorophyll content (2.08 mg/g), and T1(C1N1P1K1) resulted in the highest contents of starch (11.60 mg/g) and trilobatin (old leaf: 0.29%; tender leaf: 2.28%). The indicators corresponding to the above three treatments were significantly higher than those under the other treatments (p < 0.05). The results as analysed by the affiliation function method show that the highest mean value of the affiliation function was 0.645 after T4(C2N1P2K3) treatment. Conclusions: The combination of biochar and nitrogen, phosphorus, and potassium fertilisers can effectively increase the biomass and active components of Lithocarpus litseifolius while reducing the amount of chemical fertiliser applied. A comprehensive analysis of the results showed that the T4 treatment (biochar: 20 g/plant; urea: 10 g/plant; superphosphate: 9 g/plant; potassium chloride: 12 g/plant) resulted in the highest comprehensive score, with the highest increase in plant height growth, ground diameter growth, root–crown ratio, soluble sugar, soluble protein, and phlorizin, as well as other indicators.

Down-streaming Small-Scale Green Ammonia to Nitrogen-Phosphorus Fertilizer Tablets for Rural Communities

This study aims to evaluate the growth and production of sweet corn plants in response to the application of commercial NPK fertilizer and various doses of nitrogen-phosphorus fertilizer tablets. From early October 2022 to late January 2023, research was conducted at Research and Development Luas Birus Utama to produce nitrogen-phosphorus fertilizer tablets and at Research and Development Syngenta Indonesia Cikampek Station, Karawang, to perform a semi-field analysis. A factorial randomized block design with two treatment factors was employed in this study. The first factor was five types of nitrogen-phosphorus fertilizer tablets, namely, A (0% nitrogen and 6.3% phosphorus), B (0.81% nitrogen and 6.3% phosphorus), C (1.57% nitrogen and 6.1% phosphorus), D (2.33% nitrogen and 6.2% phosphorus), and E (3.06% nitrogen and 6.2% phosphorus). The second factor was F (standard nitrogen, phosphorus, and potassium). The results revealed that applying different dosages of nitrogen-phosphorus fertilizer tablets in combination with potassium chloride fertilizer yielded no different effect on the growth, biomass, and yield components of sweet corn plants when compared to applying NPK fertilizer. A comparison between the soil test results before and after application revealed that the formulation of fertilizers in tablet form helps plants to effectively absorb the required nutrients. It is currently possible to develop small-scale or microscale green ammonia production technology to fulfill the fertilizer requirements of rural communities because of its low cost, low carbon emissions, and low renewable energy consumption. The scarcity of fertilizer supplies endangers Indonesia’s food sustainability. Nitrogen-phosphorus fertilizer tablet production technology can be used in areas with a scarcity of inorganic fertilizers but with the potential for low-grade phosphate mines using commercial ammonia solutions. Thus, understanding how to produce nitrogen-phosphorus fertilizer tablets from ammonia solution will aid in the acceptance of microscale green ammonia production technology. Doi: 10.28991/ESJ-2024-08-02-016 Full Text: PDF

Interaction between lignin and cellulose during the pyrolysis process

The hierarchical and heterogeneous structures and the interactions between biomass components within cell walls are closely related to the pyrolysis characteristics. In this work, thermogravimetric analysis (TGA) and pyrolysis kinetics analysis were used to investigate the pyrolysis characteristics of windmill palm (Trachycarpus fortunei (Hook.) H. Wendl.) culm and silk after delignification. The results demonstrate cellulose pyrolysis temperature of silk is much higher than that of culm, attributed to the higher lignin content of the former. After delignification, the cellulose pyrolysis temperature of silk decreased by 48 °C, which is much higher than that of culm by 18 °C, suggesting a strong interaction between lignin and cellulose during the pyrolysis process. Futhermore, pyrolysis kinetics analysis also found that the frequency factor of slik and culm increased by 129 % and 26 %, respectively, attributed to the disappearance of the carbon layer formed by lignin pyrolysis process. And, differ in lignin content is responsible for the discrepancy of frequency factor increase. In conclusion, we propose a mechanism model for lignin hindering cellulose pyrolysis, which is of great significance for understanding the pyrolysis interactions of biomass components in complex supramolecular cell wall.

Process simulation of flax straw pyrolysis with kinetic reaction Model: Experimental validation and exergy analysis

Pyrolysis, a viable method for converting organic material into value-added products, has significant potential to reduce environmental footprints. In this study, slow and fast pyrolysis of flax straw biomass was modeled in an Aspen Plus. This was followed by validation of the product yields (biochar, bio-oil, and gas) with our earlier experimental data with slow pyrolysis. The Aspen Plus model incorporated a kinetic reaction model based on the three main components of lignocellulosic biomass: cellulose, hemicellulose, and lignin. The kinetic reaction model includes 21 reactions representing the volatilization, degradation, and decomposition processes inherent in biomass pyrolysis. The Aspen Plus confirmed the consistency of the findings by validating the biogas yield (which ranged from 21.4 wt% to 38.6 wt%), biochar (29.5 wt% to 42.8 wt%), and bio-oil (35.8 wt% to 40.3 wt%). The robustness of the model was verified by experimental data using controlled pyrolysis tests of flax straw feedstock at different temperatures, showing strong agreement. The kinetic reaction model is adaptable for predicting pyrolysis yields for various lignocellulosic biomass feedstocks under typical pyrolysis conditions. Furthermore, energy and exergy analyses were briefly assessed using the product yields, pyrolysis temperature, and heating values of the products at slow and fast pyrolysis conditions. The conventional exergy analysis showed an exergy efficiency of 87–95 % with varying temperatures from 400 to 600 °C for slow pyrolysis, with the highest efficiency obtained at 500 °C. Fast pyrolysis has resulted in a higher exergy efficiency than slow pyrolysis, ranging from 89 % to 98 %.

Oil sludge addition enables prediction of biomass pyrolysis product profiles by synergistic behaviors between biomass components and oil sludge

The complex composition of biomass leads to wide variations of pyrolysis products, which makes the prediction of pyrolysis product profiles greatly difficult. This study firstly found that biomass co-pyrolysis with oil sludge (OS) made product profiles well-predictable. Co-pyrolysis of three biomass components, hemicellulose (Hemi), cellulose (Cel), and lignin (Lig) with OS increased the comprehensive pyrolysis index compared to OS pyrolysis alone. Moreover, co-pyrolysis with OS led to a weaker intensity of gas release (CH4, H2O, CO, and CO2) and lower apparent activation energies than pyrolysis of individual biomass components. OS/Hemi and OS/Cel co-pyrolysis promoted the formation of char and gaseous products as well as the generation of oxygenates in oil products. On the other hand, OS/Lig co-pyrolysis enhanced gas production and contributed to the formation of hydrocarbons like long straight-chain alkanes with less oxygenates formation. Using co-pyrolysis results of OS/Hemi, OS/Cel, and OS/Lig, the product yields and oil compositions of OS/real biomass co-pyrolysis (woody biomass and rice straw) were successfully predicted based on only Hemi/Cel/Lig composition ratios of the biomass. Because direct interactions between OS and biomass components might be prior to pyrolytic interactions among biomass components, it enables the excellent predictability. It also proposes that OS or other appropriate materials might facilitate the industrial applications of miscellaneous biomass pyrolysis owing to reliable predictions of product profiles based on the biomass composition ratios.

Assessing the influence of biomass origin and fractionation methods on pyrolysis of primary biomass fractions

Pyrolysis has emerged as a highly promising technology for the efficient utilization of organic materials, particularly lignocellulosic materials. This study investigates the behavior and influence of three primary biomass fractions (cellulose, hemicellulose, and lignin) derived from different sources (trees, shrubs, and agricultural residues) on the kinetic of the pyrolysis process. With this objective, different fragmentation methods were employed to isolate the main components of the lignocellulosic biomass, followed by thermogravimetric analysis to examine the pyrolysis process. The activation energy was determined using both, the Friedman differential kinetic models of and the Flynn-Wall-Ozawa integrated method, with the latter being found to be more efficient. The activation energy (Ea) was found to be influenced by several factors, including the fractionation process and the origin of the raw material. For hemicellulose, the Ea was in the range of 200–300 kJ mol−1, while cellulose showed Ea values of about 180–220 kJ mol−1. In contrast, lignin displayed a wider range of Ea variation, with its values being more sensitive to the fractionation method used. Gas samples were collected through adsorption tubes during pyrolysis for analysis of gas stream compositions from different lignocellulosic fractions using gas chromatography/mass spectrometry. Furfural, among other compounds, was predominantly detected in the pyrolysis of hemicellulose fractions, ranging from 6.6 % to 19.3 %.

Effect of Fe and its oxides on steam gasification mechanism of lignin using ReaxFF molecular dynamics simulations

Lignin is an important biomass component and its gasification process has been extensively studied. Iron is widely found in nature, and the corresponding iron-based catalysts have been heavily used in the study of various systems. The advantages are that it is inexpensive and not easy to pollute the environment, and it can also be extracted from the system and reused. However, studies on the effect of iron and its oxides on the steam gasification of lignin are limited, most studies have focused on supercritical water gasification. In this study, the effects of Fe and its oxides on the steam gasification process of lignin dimers were simulated using reactive force field (Reaxff) molecular dynamics (MD). By analyzing the gas products and the evolution of the structures. It was found that low valence Fe greatly improved the efficiency of lignin steam gasification, while higher valence iron oxides were significantly less effective. There were also significant differences in the distribution of gas products for different valence states of Fe. Low-valent Fe greatly improves the yield of combustible gases such as H2 and CO, while high-valent Fe is better at generating CO2. Carbon accumulation occurs on the surface of the catalyst, which reduces the catalytic effect. By comparing the effects of different temperatures on the steam gasification of lignin, it was found that increasing the temperature accelerates the decomposition process of lignin, and that the steam gasification of lignin has a critical temperature at which the yield of the main gaseous products of lignin is the highest.

Precursor screening of fruit shell derived hard carbons for low-potential sodium storage: A low lignin content supports the formation of closed pores

Biomass hard carbons are being explored for anode materials of sodium-ion batteries due to the wide availability. However, the precursor screening for optimal microstructure and sodium storage performance is tedious and time-consuming. Here, we selected three kinds of fruit shells to prepare hard carbons for sodium-ion batteries and investigated their structure characteristics and sodium storage performance. It is demonstrated that a low lignin content in fruit shells is favor to the formation of closed pores in the derived hard carbons, thus generating a high low-potential plateau capacity. Among the main component of biomass, lignin with rich aromatic ring structure possesses higher thermal stability than cellulose and hemicellulose. During the pyrolysis and carbonization, lignin may decompose to large-size crystalline domains, which hinders the random stacking of carbon layers. Therefore, as the lower lignin content than pine nut shell and macadamia nut shell (28.4% vs. 39.2% and 37.4%), the walnut shell derived hard carbon shows a largest interlayer distance of 0.397 nm and a highest closed pore area of 391 m2 g−1, contributing to the supreme specific capacity of 362.6 mAh g−1, with a plateau capacity of 195.8 mAh g−1 as well as a remarkable cycle stability. The assembled WNSC//NVP full-cell remains a discharge capacity of 53.1 mAh g−1 after 100 cycles at 0.1 A g−1. This work gives a deep insight of the relationship between biomass composition and microstructure of the derived hard carbons to explore its high sodium storage ability in low-potential region.

Critical review of the role of ash content and composition in biomass pyrolysis

In the face of environmental challenges (e.g., dramatically increasing greenhouse gas emissions and climate change), it is utmost of importance to sustainable energy systems. Biomass consisting of agricultural and forest waste, municipal solid waste, and aquatics, has been identified as alternative and promising fuel sources. Thermochemical conversion approaches like pyrolysis can turn various types of biomass into three valuable product streams, namely, bio-oil, biochar, and syngas. To date, past review articles have considered the major operating parameters of kinetics, chemistry, and the application of pyrolysis products. However, ash content is one of the key biomass components that lacks investigation on its influence during biomass pyrolysis with respect to products yield and properties. This review article examines: i) the ash content and composition in different types of biomass; ii) effects of ash content on catalytic pathway and biomass thermal degradation; iii) ash related problems in the thermal degradation of biomass; and iv) available deashing techniques for biomass. The review aims to provide new understandings and insights regarding the effects of ash content and composition on biomass pyrolysis.

Ecosystem importance of roots: A literature review

Fine roots are all those with a diameter ≤2 mm. These roots are responsible for a significant portion of the primary productivity of terrestrial ecosystems, being important for providing resources to the soil microbial community and for influencing the cycling of carbon and nutrients. Despite their recognized importance, fine roots are commonly neglected in plant biomass studies. Root biomass studies are generally limited throughout the world, mainly due to the methodological complexity involved in the analytical processes. The objective of this work was to carry out a review of studies on the topic of roots, addressing the development of technologies in the analytical process and the importance of this dynamic biomass component in ecosystem processes related to carbon cycling and soil nutrients. We emphasize here the importance and need for new scientific research that seeks to develop methods of analysis, as well as to estimate the underground primary productivity, especially that of fine roots, so that the processes involved in the cycling of carbon and nutrients are better elucidated.

Research on the hot densification mechanism of biomass wastes based on molecular dynamics simulation and components adjustment method

The hot densification process can be used to prepare the biofuel pellets and diversified densification materials with suitable mechanical strength to overcome the natural defects of low energy density and loose structure of biomass wastes and achieve the high value utilization of the renewable resources. In this study, the two typical biomass wastes, cotton stalk (CS) and Chinese fir wood sawdust (WS) are used for the hot densification investigation (85 °C), and the microscopic evolution behavior of the biomass components during the hot densification process is explored through the combination of the component adjustment method and molecular dynamics simulation. The results show that cellulose is the key component to the mechanical strength of biomass pellet, which plays the crucial role of skeleton support in the densification process, and the strength of pellet is positively correlated with the increasing addition ratio of cellulose. Furthermore, crystalline cellulose exhibits the strongest bonding properties in the hot densification process due to the formation of rich hydrogen bonds and the increasing intermolecular attraction force. Lignin has the poorest capability for hydrogen bond formation, and its addition increases the van der Waals repulsive forces, resulting in the poorest densification performance. Hemicellulose shows the better adhesion capability than lignin due to its glassy transition (83.34 °C) and the suitable addition can greatly improve the mechanical property of the pellet, up to 14.26 MPa. There exists the strongest synergistic effect between cellulose and hemicellulose, which is beneficial to the bonding performance between particles to different extent. Hot densification process can promote the formation of hydrogen bond connections between molecules/atoms and the increase of the van der Waals repulsive force in the further compression. The densification performance of biomass is the combined effect of the physical forces, including electrostatic force and van der Waals force.