Fiber Lignin Research Articles

Stabilization and Reinforcement Effect of Fibers on a Bitumen Binder.

This study investigated fibers' stabilization and reinforcement effect on a bitumen binder. The fibers' microstructures were primarily observed using scanning electron microscopy, and laboratory tests, including the oven heating and mesh-basket draindown, were designed and carried out on three different fiber-bitumen binders (lignin, mineral, and carbon fiber) in this paper to evaluate the bitumen adsorption and thermal stability, respectively. Then, the cone sink experiment was performed to check the rheological properties of these fiber-bitumen binders. These results reveal that the stabilization and reinforcement effect increases with the fiber content increasing to the optimal value. The optimal fiber content depends on the performance of the fiber-bitumen binder, and the value found in this paper is 0.4 wt %. The results indicate that the fiber enhances the toughness of the bitumen effectively via its spatial framework, adhesion, and stabilization of the fiber-bitumen binder. The rheological properties and rutting resistance were tested by a dynamic shear rheometer, and the results suggested that the fiber could effectively enhance the flow resistance and the rutting resistance of the fiber-bitumen binder.

Wood quality of residual branches of Hymenaea courbaril L. from logging in the Amazon rainforest

Abstract Branches remain in the forest environment as logging activity residue. Considering the large size of many Amazonian trees, their branches have considerable dimensions and can contribute to a sustainable wood alternative for various applications. Due to the formation of reaction wood in the branches, relevant macro and ultrastructural changes can occur in its characteristics in relation to the trunk wood. However, the woods of the branches are not technologically well known. Therefore, this work aimed to evaluate the wood quality of branches of Hymenaea courbaril L., comparing it with wood of trunks. The extractives and lignin contents, basic density, shrinkage, fiber biometry, microfibril angle and mechanical resistance to compression parallel to the fibers were analyzed. The branch wood had smaller fiber dimensions and a higher microfibril angle than the trunk wood. The basic density was similar between these materials. The linear and volumetric shrinkages were smaller in the branch wood than in the trunk, while the axial shrinkage was higher in the branch. The parallel compressive strength was also lower in the branch wood than in the trunk. The branch wood has properties suitable for products with higher added value such as furniture, decorative objects, floors and utensils in general.

Cross-Breeding Improvement and Performance Analysis of Dominant Production Traits in Grazing-Type Alfalfa (Medicago sativa L.).

Rhizome-rooted Medicago sativa L. "Qingshui" is an excellent germplasm for establishing grazing and ecological grasslands but inferior in yield, in which both high production and ecological values can be achieved by cross-breeding. We have obtained valuable rhizome-rooted hybrid strains (RSA-01, RSA-02, and RSA-03) by crossing of Qingshui and the high-yielding Medicago sativa L. "WL168." In this study, the Qingshui plants with low production performance were crossed for improvement, and progenies with better production and higher quality than those of Qingshui were selected. The results reveal that the branch number, crude protein (CP) content, and relative feed value (RFV) of RSA-01; the stem thickness, CP content, and ether extract (EE) content of RSA-02; and the plant height, stem thickness, branch number, and dry hay yield of RSA-03 were higher than those of Qingshui. Except for the leaf/stem ratio and plant height of RSA-01, leaf/stem ratio of RSA-02, and plant height of RSA-03, the coefficient of variation (CV) of yield traits of the hybrid strains was lower than those of Qingshui, ranging from 0.1% to 4.28%. In addition to the lignin and acid detergent fiber content of RSA-01 as well as EE content of RSA-02 and RSA-03, the CV of the nutritional traits of the hybrid strains was low, ranging from 0.60% to 3.43%. The tested samples were ranked as follows based on yield performance and nutritional values: WL168 > RSA - 03 > RSA - 01 > RSA - 02 > Qingshui and RSA - 01 > WL168 > RSA - 03 > Qingshui > RSA - 02, respectively. Compared with parental Qingshui, RSA-01, RSA-02, and RSA-03 show better yield performance; meanwhile, RSA-01 and RSA-03 had higher nutritional traits. RSA-01 shows heterosis in branch number, CP content, and RFV; RSA-02 shows heterosis in stem thickness and RSA-03 in plant height, stem thickness, branch number, fresh yield, dry hay yield, and CP content. Notably, the low production performance of Qingshui was improved after crossing it with WL168, substantially resulting in an abundant rhizome-rooted germplasm resource for the establishment of grazing grasslands.

Mechanical, thermal, viscoelastic and hydrophobicity behavior of complex grape stalk lignin and bamboo fiber reinforced polyester composite

This work aims to investigate the degradation stability of bamboo fiber-reinforced polyester composite toughened with complex lignin biopolymer derived from the waste grape stalks. The properties like mechanical, wear, thermal, DMA, and hydrophobic were studied after the addition of lignin and analyzed how the lignin addition influenced these properties. Prior to composite making the fiber and lignin was treated with silane. According to the results obtained incorporating 40 vol% of bamboo fiber into the polyester resin, the mechanical and wear properties enhanced. Further, the composite containing 2.0 vol% of lignin has maximum tensile strength, tensile modulus, flexural strength, flexural modulus, and ILSS. Similarly, the composite designation having 4 vol% lignin revealed the improved wear loss stability of 0.007 mm3/Nm (sp. wear rate). The highest degradation temperature reported for composite designation UBL4 it was 520 °C, with a relatively lesser weight loss of 19 %. Likewise, the highest storage modulus was about 4.5 GPa, and the lowest loss factor was up to 0.3 for the composite designation UBL4. The contact angle investigation revealed that all composite designations are not fall below 70°, indicating their hydrophobic stability. These composites with enhanced stability against load, heat and water could be utilized in the industrial, automotive and defense sectors where high performance outcomes are required.

Effects of Fiber Type on the Mechanical Properties of the Open-Graded Friction Course Mixture.

The open-graded friction courses (OGFCs) have a large number of interconnected voids, which may cause serious water damage to the pavement. Hence, the road performance needs to be investigated. In this study, the mechanical properties of OGFCs containing two different fibers (lignin and mineral fiber) were investigated. Based on the procedure proposed by the Chinese specification JTG F40-2004, OGFCs were designed with the asphalt content between 4.1 and 4.7 wt % to find the optimal asphalt content (OAC). The mesh-basket draindown test was used to check the fiber's stabilization and absorption of bitumen. OGFCs containing the lignin/mineral fiber with OAC would be preferred in terms of the bulk specific gravity. These results indicate that the fiber can bring higher air voids to the OGFCs, and the different specific gravities of fibers may primarily account for the result. Both the lignin and mineral fibers can bring much more asphalts padded in the pores of mineral aggregates and subsequently larger OAC in OGFCs due to their higher asphalt absorption. Performance experiments were carried out to check the dynamic stability and moisture susceptibility of OGFCs containing the lignin/mineral fiber. The study suggests that the lignin and mineral fiber can be used to adjust the internal environment of OGFCs, enhancing the moisture damage resistance and improving the rutting resistance of OGFCs at high temperatures.

Highly porous and conductive functional carbon fibers from electrospun phosphorus-containing lignin fibers

Functional carbon fibers were prepared by carbonization of thermostabilized electrospun lignin-fibers at 500–900 °C followed by a high temperature thermal treatment at 1200–1600 °C. The effect of the preparation temperature on their surface chemistry, structural order, textural properties and electrochemical behavior has been stablished. Maximum porosity development is obtained at 900 °C. The addition of phosphoric acid in the electrospinning lignin solution shortens the stabilization time of the fibers, increases the carbonization yield, generates phosphorus functional groups (P content as high as 3% wt.) and increases the BET surface area of carbon fibers from 840 to 1143 m 2 g −1 . Interestingly, when phosphorus-containing carbon fibers are treated even at very high temperature, 1600 °C, most of the porosity is preserved (A BET = 822 m 2 g −1 ). XPS depth profile reveals the presence of reduced phosphorus in the core of carbonized fibers. XRD and TEM analysis make evident that the presence of phosphorus induces curvature of the graphitic layers, which seems to hinder the stacking of the graphene layers, explaining the preservation of microporosity after the thermal treatment at high temperature. However, Raman and XRD analyses point out that the presence of phosphorus does not affect the lateral growing of the crystallites. Thus, phosphorus preserves the porosity and allows the development of the electrical conductivity after the thermal treatments. Gravimetric capacitances of 79 F g −1 and capacitance retention of 63% at 68 A g −1 have been determined for phosphorus-containing carbon fibers prepared at 1200 °C. • Electrospinning of H 3 PO 4 lignin solution produced P-containing carbon fibers. • Experimental evidence about curvature of graphitic layers induced by P is reported. • P impedes the stacking of graphene layers while allowing their lateral growing. • P in carbon fibers core prevents from porosity shrinkage after heat treatment at 1600 °C. • Electrical conductivity and capacitance retention is promoted after heat treatment.

Study on Composite Improvement of Silt Sites by Lignin and Sodium Methylsilicate and Its Micro Mechanism

Kaifeng Zhouqiao site is located in the traffic trunk line in Gulou District of Kaifeng City. The dynamic load of urban traffic is large. In addition, the silt has poor stability of its particle skeleton structure, large porosity and poor mechanical performance. Under the action of dynamic load, the soil of the site will suffer from cracking, collapse, unstable deformation and overall stability damage. In order to enhance the stability of the soil, this paper uses sodium methylsilicate and lignin fiber to modify the site soil, evaluates the mechanical properties of the improved soil through the compression and shear tests, evaluates the durability of the improved soil through the dry wet cycle test, and reveals its modification mechanism through the micro experiment, so that the mechanical properties of the site soil can be improved, so as to achieve the purpose of repair and reinforcement. The experiment shows that the effect of improving the compressive strength of soil is the best when the content of sodium methylsilicate is 0.3%–0.5%, and the effect of improving the shear strength of soil is the best when the content of lignin is 0.5%–2%. The maximum mass loss rate of the composite modified sample after 10 dry and wet cycles is only 0.71%. The comprehensive analysis determines that the best proportion of the composite is 0.5% sodium methylsilicate and 2% lignin fiber. The modified soil has good waterproof and mechanical properties.

Fischer-Tropsch synthesis over lignin-derived cobalt-containing porous carbon fiber catalysts

Cobalt-containing lignin-based fibers were synthesized in one step by electrospinning of Alcell lignin solutions as carbon precursor, a low-cost and renewable co-product of the paper making industry. The lignin fibers were thermostabilized in air to avoid the fusion during the carbonization process between 500 and 800 °C to obtain cobalt-containing porous carbon submicron fibers. These carbon fibers catalysts were studied for the Low-Temperature Fischer-Tropsch synthesis. The lignin-derived fibers containing Co catalyst located on the overall carbon fiber surface (internal and external) heat-treated at 500 °C (Co@CF-500) showed the best catalytic performance after 70 h on stream, with 75% and 60% selectivity to C5+ at 220 °C and H2/CO ratios of 1 and 2, respectively, attributed to the high Co dispersion, optimal Co-particle size and better Co accessibility. Higher heat-treatment temperatures leaded to Co-containing carbon fibers with larger metallic cobalt nanoparticles encapsulated in graphitic-type carbon, which rendered them inaccessible for FTS.

Effect of Biomass as Nucleating Agents on Crystallization Behavior of Polylactic Acid.

Polylactic acid (PLA) is one of the most productive biodegradable materials. Its bio-based source makes it truly carbon neutral. However, PLA is hard to crystallize as indicated by a low crystallization rate and a low crystallinity under conventional processing conditions, which limits its wider application. One of the most effective ways to enhance the crystallization ability of PLA is to add nucleating agents. In the context of increasing global environmental awareness and the decreasing reserves of traditional petroleum-based materials, biomass nucleating agents, compared with commonly used petroleum-based nucleating agents, have received widespread attention in recent years due to their abundance, biodegradability and renewability. This paper summarizes the research progress on biomass nucleating agents for regulating the crystallization behavior of polylactic acid. Examples of biomass nucleating agents include cellulose, hemicellulose, lignin, amino acid, cyclodextrins, starch, wood flour and natural plant fiber. Such green components from biomass for PLA are believed to be a promising solution for the development of a wholly green PLA-based system or composites.

Influencing factors and evaluation methods of reinforcement effect of fiber‐modified asphalt binder

AbstractThe reinforcement of fiber is the linchpin of improving the strength of the asphalt binder and its mixture. This study aims to evaluate the reinforced shear effect and influence factors of fiber materials (i.e., lignin fiber, basalt fiber, polyester fiber, and hybrid fiber) by the self‐developed direct shear test. The micro‐reinforcement mechanism of fiber was explained based on the scanning electron microscope and basket leak test. Besides, the effects of fiber type, content, loading temperature, and rate on the asphalt binder's shear strength were analyzed systemically. The results indicate that the direct shear strength of asphalt binder was positively correlated with fiber content and loading rate but negatively associated with temperature. Meanwhile, when the fiber content is too large, the raise of shear strength will decrease. Gray entropy correlation analysis shows that the fiber type had the most effective influence on the binder's shear strength. The four fibers' reinforcing effects in descending order were composite fiber, polyester fiber, basalt fiber, and lignin fiber. Based on the growth rate of direct shear strength, the optimal lignin and basalt fiber content was 7%, polyester fiber was 6%–7%, and composite fiber was 6%. Furthermore, lignin fiber and basalt fiber were more sensitive to temperature, while polyester fiber had a better mid‐temperature weather resistance. Composite fibers and basalt fibers performed more stable behavior at high loading rates, decreasing 39% and 40%, respectively. Polyester fibers were stable when applied to the low loading rates, with an attenuation rate of 42%.

158 Predicting Intake and Digestibility of Nutrients in Beef Cattle fed High Forage Diets Using Near Infrared Spectroscopy (Nirs) of Feces and Internal Markers

Abstract Objectives of this study were to determine the potential of near infrared-spectroscopy (NIRS) scanning of feces to predict diet digestibility and intake in beef cattle fed high forage diets, and to investigate the use of acid detergent lignin (ADL) and undigestible neutral detergent fiber (uNDF) as internal markers to determine digestibility. Beef heifers were fed 12 different forage-based diets ( > 95% forage dry matter basis) in 3 total collection studies, resulting in individual fecal samples and related spectra (n = 135) corresponding to apparent total tract digestibility (aTTD) and intake data. Dried and ground fecal samples were scanned using a FOSS DS2500 scanning monochromator (FOSS, Eden Prairie, MN). Modified partial least squares (MPLS) regression was performed to develop equations to predict digestibility [dry matter (DM), organic matter (OM), NDF, and nitrogen (N)], and intake [DM, OM, NDF, N, uNDF]. Digestibility prediction equations for DM, OM, NDF, and N resulted in R2CV or 0.72, 0.65, 0.74 and 0.69, respectively, and standard error of cross validation (SECV) between 2.20 to 2.82. Intake calibrations for DM, OM, N, NDF, ADL and uNDF resulted in R2CV values between 0.59 and 0.91, SECV for intake (kg/d) of 1.12, 1.10, 0.02, 0.69, 0.06, 0.24, respectively, SECV for intake % body weight (BW) between 0.00 and 0.16; and SECV for g/kg BW0.75 between 0.60 and 0.86. Significant correlations (P < 0.01) were identified between NDFD determined by aTTD and by the internal marker ADL (r = 0.72) or uNDF (r = 0.57). Developed calibrations predicting marker calculated digestibility resulted in R2CV(SECV) values of 0.85(2.70) and 0.80(2.46) for lignin and uNDF, respectively. We confirm the potential of NIRS to predict digestibility and intake of cattle fed high forage diets. Future steps include further validation of the intake calibration equations using internal marker and energetics modeling.

Performance evaluation of lignin-fibre reinforced asphalt mixture modified by anti-rutting agent

• The ARA could enhance the road performance of the LFSMA-13 for different ages and decrease the performance sensitivity to age. • The lignin fibers physically interact with the asphalt, while the ARA could chemically interact with the asphalt mixture. • The peak area of the imino and methyl in the asphalt decreases, and the peak area of the carbonyl and sulfoxide increases with age. • The correlation between the peak areas of imino, methyl, carbonyl, and sulfoxide, and the physical property indices of the LFSMA-13 and ALSMA-13 is good. This paper aims to analyze the long-term road performance of anti-rutting agent (ARA) reinforced asphalt mixture, and reveal its road performance from the micro morphology and chemical perspective. ARA was used to modify the lignin fiber-reinforced SMA-13 asphalt mixture (LFSMA-13). The unaged, and the short and long-term aged specimens were used to test the road performance (high and low-temperature properties, water stability, and anti-cracking) of the LFSMA-13 and ARA modified LFSMA-13 (ALSMA-13). In addition, the micromorphology of the additives and asphalt mixture and the chemical property of asphalt in the mixture were analyzed using the scanning electron microscope (SEM) test and Fourier transform infrared (FTIR) test. The relationship between road performance and chemical property was also analyzed. The results showed that the performance of the ALSMA-13 was better with age than the LFSMA-13. The SEM images showed that the lignin fiber and the ARA could form a network structure in the SMA-13 mixtures. The FTIR test indicated that the ARA's amino group (–NH–) could chemically interact with the asphalt in SMA-13. The peak area of the carbonyl and sulfoxide chemical group increased, and the imino and methyl decreased with age. The results showed a good correlation between the FTIR parameters and road performance.

Valorization of sugarcane bagasse through biofuel and value-added soluble metabolites production: Optimization of alkaline hydrothermal pretreatment

Sugarcane bagasse (SCB) is increasingly considered as a potential source for bioenergy or bulk chemicals production. However, efficient pretreatment techniques need to be developed to make full use of its potential. A central composite design was employed to evaluate the effect of temperature (146.4–213.6 °C), NaOH concentration (0.7–2.3 M) and treatment time (3.2–36.8 min) on the hydrothermal pretreatment of SCB. Glucose was the abundant fermentable sugar released in the hydrolysate (4.0 g/L) and its concentration was significantly (p-value < 0.05) affected by temperature and NaOH concentration. Sugars released in the hydrolysate and the remaining cellulose, hemicellulose, and lignin in the pretreated fiber were anaerobically co-digested in batch thermophilic assays (55 °C). Propionate, one of the most promising platform chemicals, was the main metabolite produced (0.5 g/L) and its concentration was significantly affected by temperature and NaOH concentration. Both NaOH concentration and pretreatment duration significantly affected methane composition in the biogas (p-value <0.05 and 0,10 respectively). Defluviitoga, and Methanothermobacter genera were favored in response to alkaline hydrothermal pretreatment at the central point conditions (180 °C, 1.5 M NaOH, 20 min).

Role of Lignin Enriched Natural Sesbania aculeata (Dhaincha) Fiber for Ultraviolet Protection and Thermal Comfort of Woven Textiles

ABSTRACT Sesbania aculeata (Dhaincha), a lignocellulosic bast fiber, has been explored here as an ultraviolet blocker due to the presence of natural lignin of about 19% on its surface. Various woven fabrics are prepared with various dhaincha/jute-blended yarns as weft to measure ultraviolet (UV) protection ability, drying rate, and thermal conductivity. Effect of linear density of blended yarn, blend ratio, and pick density of the prepared fabrics on UV protection ability, drying rate, and thermal conductivity have been studied and optimized using 33 Box–Behnken response surface design. The optimum level of these parameters to obtain high UV protection, high drying rate, and high thermal conductivity are reported. The UV protection factor (UPF), drying rate, and thermal conductivity of the fabric are achieved as high as 92.68, 0.3589 ml/H, and 0.185754 W/mK, respectively. The presence of lignin in jute and dhaincha fibers is evidenced by FTIR study. This research work establishes the new application of dhaincha fiber in the field of textiles for UV protection and thermal comfort.

Ultra-light polylactic acid/combination composite foam: A fully biodegradable flame retardant material

In this study, low-density polylactic acid (PLA) flame retardant foams were prepared using lignin fiber (LF), ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP) and SiO2 aerogel. LF, RDP and SiO2 aerogel alone did not improved the flame retardancy of PLA composites; however, APP alone required a higher addition of amount to achieve a better flame retardancy. The synergistic effect between the four can improve the flame retardancy of PLA at a lower addition level. The intumescent flame retardant system composed of LF/APP/RDP/SiO2 aerogel can not only form a dense carbon layer on the surface of the material when burning to improve the flame retardant performance, but also improve the thermal stability of PLA, increase the degradation temperature and reduce the thermal weight loss rate. The final PLA flame retardant foam (density: 0.022 g/cm3) prepared by supercritical foaming can reach V-0 rating in UL-94 vertical combustion test, and the limiting oxygen index (LOI) can reach 30.5 %.

Effect of Fibers on the Performance of a Porous Friction Course.

In this paper, the preparation of a porous friction course (PFC) with styrene–butadiene–styrene (SBS)-modified asphalt and fibers instead of a high-viscosity-modified asphalt was investigated. The aggregate gradation B was chosen to prepare the PFC, and the optimal asphalt content in the PFC containing lignin or basalt fibers was determined to be 4.5% by the Cantabro abrasion experiment and Schellenberg draindown experiment. The freeze-thaw split experiment and immersed Marshall experiment indicated that with the addition of the fiber, the residual stability increased by 7.6 and 2.4% for the PFC with the lignin and basalt fibers, respectively, indicating that fibers can enhance the moisture damage resistance of the PFC. Furthermore, the dynamic stability increased by 17.9 and 6.0% for the PFC with the lignin and basalt fibers, respectively, indicating that fibers can significantly enhance the rutting resistance of the PFC at high temperatures. These results prove that the PFC prepared by SBS-modified asphalt and lignin/basalt fibers reaches the standard of pavement performance.

Biological delignification of rice straw using laccase from Bacillus ligniniphilus L1 for bioethanol production: A clean approach for agro-biomass utilization

The recalcitrance of lignocellulosic biomass due to severe lignification and complex cross-linking between lignin and cellulose fibers is a major hindrance in its clean and economical conversion to bioethanol . In the present study, the ligninolytic activity of purified bacterial laccase (BLac) from Bacillus ligniniphilus L1 was evaluated for delignification of rice straw for environment-friendly bioethanol production . BLac showed significant delignification activity at varying pH (3, 4, 7, and 9), and decreased the lignin (8.93%) and phenolic (44.8%) contents of rice straw. The chemical and structural changes in rice straw caused by BLac pretreatment determined via scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Fourier transform infrared (FTIR) spectroscopy confirmed the successful delignification of rice straw. BLac improved the cellulase (CL) hydrolysis of rice straw by releasing 15.8 mg/mL glucose and 21.8 mg/mL reducing sugar, and produced 22.3 mg/mL bioethanol. These findings indicate that BLac has the potential to efficiently utilize the rice straw resources for economical and environmentally feasible bioethanol production. • BLac reduced lignin (8.93%) and phenolic contents (44.8%) of rice straw. • BLac enhanced the release of glucose (15.8 mg/mL) and reducing sugar (21.8 mg/mL). • BLac caused significant physicochemical changes in rice straw biomass. • High ethanol production (22.3 mg/mL) from rice straw via BLac pretreatment.

Thermal Stability Analysis of Cellulose From Sago Fiber Waste (Metroxylon sago)

Sago pulp is a lignocellulosic waste rich in cellulose, so that it can be used optimally as a source of carbon and cellulose. Fixed carbon can be obtained maximally by determining the carbonization temperature. This research aims to determine the temperature of the cellulose sample starting to decompose and the energy required at the time of decomposition. The process of extracting cellulose from sago fiber waste uses NaOH alkalinization for delignification, bleaching with H2O2, and hydrolysis with HCl. Identification of lignin in sago fiber is known by the appearance of the C=O group in the wave region of 1734.01 cm-1 with strong intensity; after extraction, no peak number was found in the extracted cellulose FTIR spectrum. TGA analysis of cellulose underwent two stages of mass change, the first stage of decomposition of water molecules at a temperature of 47°C-203°C obtained a mass decrease of 5.69%, and the second stage of decomposition at a temperature of 287°C-397°C obtained a mass decrease of 58.95%. DSC analysis obtained two thermal properties of physical changes contained in two endothermic peaks, the first peak of water evaporation which required energy of 28,1120 J/g, and the second peak of decomposition, which required energy of 9.6188 J/g.

Methane production of banana plant: Yield, kinetics and prediction models influenced by morphological parts, cultivars and ripening stages

Banana trees and fruits with three ripening stages, including green, ripe, and overripe, of two cultivars, namely Nam wa and Hom were separated into different morphological parts for biogas yield determination. Specific methane yields (SMY) were significant different among banana parts (p ≤ 0.05). High non-structural carbohydrates and high non-lignocellulosic residual in substrates promoted high SMY. Pseudostem showed the highest share of energy yields among farm wastes which Nam wa cultivar provided higher energy potential than Hom. Peel presented the major energy source from fruit wastes which ripening stages did not have a significant effect on its SMY. Modified Gompertz model presented the best fit for methane production of most substrates. The SMY prediction models based on chemical constituents were developed to obtain conveniently used methane estimating tool which showed that a combination of lignin, hemicellulose, non-lignocellulosic residual, and crude fiber contents presented the highest performance for banana substrates.

Effect of pre-oxidation temperature and heating rate on the microstructure of lignin carbon fibers

Lignin is a biopolymer with high carbon content, making lignin-based carbon fiber an important research direction. In the process of carbonization to prepare carbon fibers, lignin fibers are easily softened and fused, which destroys the microstructure of fibers, thereby reducing the quality of lignin-based carbon fibers. Therefore, it is non-negligible to pre-oxidize lignin fibers before carbonization to prevent fiber fusion and maintain fiber structure. Therefore, the effects of pre-oxidation temperature and heating rate on the structure of pre-oxidation lignin fibers with controllable diameter and thickness prepared by melt-blowing were studied in detail. During pre-oxidation, crosslinking and aromatization of lignin fibers occurred, and alkyl and benzene rings were mainly oxidized to form carbonyl groups. The aromatization degree of the pre-oxidized product was recorded at 280 °C and 0.25 °C/min, and the oxygen content reached 15 %–20 %, making it suitable for the preparation of bio-based carbon fibers. On this basis, carbon fibers with porous morphology can be prepared with a graphitization of 0.54 and a resistivity of 0.02 Ω cm−1. These materials are expected to be applicable in sensors, catalytic materials and other fields.