Alkali Lignin Research Articles

Catalytic hydrogenolysis of alkali lignin in supercritical ethanol over copper monometallic catalyst supported on a chromium-based metal–organic framework for the efficient production of aromatic monomers

The catalytic hydrogenolysis of lignin has been reported as an effective approach for lignin depolymerization owing to its high efficiency for aromatic monomer production. In this study, a series of copper monometallic catalysts over an MIL-101(Cr) support were synthesized and used for the catalytic hydrogenolysis of alkali lignin using supercritical ethanol. First, the optimal copper catalyst for lignin hydrogenolysis was selected. Subsequently, the reaction conditions for catalytic hydrogenolysis were systematically optimized to maximize the total monomer yield. The optimal conditions were determined to be 6 h of reaction time, 20 min of sonication pretreatment, 50% catalyst loading, and 5% lignin loading. Under these conditions, an aromatic monomer yield of 38.5% was obtained; this depolymerized lignin stream, which is mainly composed of G-type monomers, can serve as a promising aromatic feedstock and carbon source for further microbial upgrading and bioconversion to produce various value-added products.

Flame-retardant effect of a functional DOPO-based compound on lignin-based epoxy resins

A simple and environmentally benign synthetic route to lignin-based epoxy resins is highly desirable. Alkali lignin and glyoxal are promising renewable and sustainable alternatives to phenol and formaldehyde, respectively. Their use is demonstrated to produce lignin-phenol-glyoxal novolac epoxy resins (LPG-NERs) through a simple one-pot synthesis. Flame retardancy of LPG-NERs was improved by functionalization with a N, S modified 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) material (termed DBS) obtained via nucleophilic reaction between DOPO and a N, S containing intermediate. FTIR and 1H NMR analyses confirmed the successful fabrication of LPG-NERs and SBD. The introduction of lignin and SBD reduced crosslinking of the epoxy network, weakening mechanical properties, but conferred excellent flame retardancy (including vapor and condensed phases) as determined by LOI (34.5%), UL-94 (V-0 rating), and cone calorimetry tests (lower heat release and smoke production, and higher char formation). The SBD structure imparted a desirable vapor mechanism (blowing out phenomenon caused by the fire quenching effect of PO•/PO2• radicals and dilution effect from non-condensable gases such as NH3, N2, SO2), while lignin (a natural biochar precursor) in synergy with SBD imparted superior charring performance.

Effect of nickel salts on the production of biochar derived from alkali lignin: properties and applications

The massive generation of alkali lignin, has aroused the attention of all walks of life, and an eco-friendly utilization approach needs to be exploited. Herein, a simple pretreatment method with nickel salts was developed for the valorisation of alkali lignin through slow pyrolysis. The pretreatment of nickel salts improved the foaming or swelling behaviors of alkali lignin upon heating, and the specific surface area and total pore size of biochars increased about thirteenfold and eighteenfold, respectively. Additionally, Ni0 particles were generated and embedded in the carbon matrix of biochars. The biochar from Ni(NO3)2 pretreated lignin catalyzed the selective hydrogenation of nitrobenzene, yielding 80.5% of aniline; and that from (CH3COO)2Ni pretreated lignin showed adsorption capacity of lead around 87.1 mg/g. Moreover, the NiCl2 pretreatment contributed to the formation of 1,2-dihydroxybenzene, while Ni(SO4)2 was conducive to the production of 4-methylguaiacol.

Microbe assisted depolymerization of lignin rich waste and its conversion to gaseous biofuel

Biomethanation potential of lignin rich residue (LRR) obtained from lignocellulosic ethanol fermentation was evaluated after subjecting to microbe assisted pretreatment using selectively enriched lignin depolymerizing consortia (LDC). The efficiency of LDC in lignin depolymerization was established using alkali and dealkali lignins (AL and DL) along with LRR as feedstocks. Microbial growth on media having lignin as sole carbon source, activity of lignin depolymerizing enzymes, viz., lignin peroxidase and laccase, ability of culture to decolorize the lignin mimicking dyes like methylene blue and ramezol brilliant blue, were considered to confirm the efficiency of enriched mixed culture. Microbial treatment using LDC showed significant positive impact on lignin breakdown irrespective of the substrate (LRR, 46.33%; AL, 31.37%; DL, 34.20%). The hydrolysate of LRR obtained from microbial pretreatment showed higher biogas yield (424 ml/g VS) owing to the efficiency of lignin depolymerization and availability of readily available biodegradable components in residual lignin from previous processing. Depolymerization of commercial lignins also produced a good amount of biogas (302–324 ml/g VS) after pretreatment with LDC. Overall, an additional energy conversion efficiency of about 11.75 kJ/g VS was obtained by valorizing the residual lignin through integrating biomethanation technology to ethanol fermentation. Outcome of this study indicated the feasibility of using lignin rich residue generated from the second generation cellulosic bioethanol plants as a potential feedstock to meet the current gaseous fuel demands. This integration also helps in closing the biomass based biorefinery loop and also promotes the circular economy.

Deep eutectic solvent assists Bacillus australimaris to transform alkali lignin waste into small aromatic compounds

To improve lignin valorization, a combination of chemical depolymerization by choline chloride (ChCl)-based deep eutectic solvent (DES) and bioconversion by Bacillus australimaris was explored. Lignin depolymerization by glycerin/ChCl released more soluble small molecules, predominantly comprising acids, aromatics, and alcohols, when compared with that by water/ChCl or only water. The most diverse depolymerization products were generated by glycerin/ChCl under the conditions of 170 °C and 50 min, releasing 17 acids with relative abundance of 80.66%, five small molecular alcohols, and nine aromatic compounds. In contrast, the maximum number of products species released by water/ChCl or only water was 12 and 21, respectively, at 100 °C. The number of lignin depolymerization products species decreased after bioconversion by B. australimaris, the bacterial strain with advantages of DES tolerance and lignin utilization. Acids presented the most significant decline during fermentation at 130 °C for 30 min, with the number of acids species decreasing from 12 with relative abundance of 73.2% (before fermentation) to six with relative abundance of 7.65% (day 3 and 7). In contrast, the relative abundance of aromatic compounds increased from 7.01% to 92.35% after 7-day bioconversion, although the number of species decreased with the fermentation duration. These results indicated that B. australimaris assimilated diverse products of DES depolymerization for cellular reproduction and further selectively degraded soluble short lignin fragments to aromatic monomers, thus confirming improvement in lignin valorization via the combination of chemical and biological methods.

Preparation and characterization of high-performance activated carbon from papermaking black-liquor at low temperature

The crude commercial Indulin C kraft lignin (InCL) isolated from pulping black-liquor was used to producing the high-value activated carbon (InCL-AC) with excellent performance. High yields (52.46 %) of InCL-AC with high BET surface area were produced from low cost and unpurified kraft lignin at low temperature (350 °C) using the cheap and environmental-friendly activation agent H3PO4. InCL-AC with higher BET surface areas and larger pore volume than the lignin-based ACs obtained from other commercial lignins, such as Indulin AT (InATL), alkali lignin (AlkL), and Norlig 11D (LS). The adsorption processes of InCL-AC followed the pseudo-second order kinetics with maximum MB adsorption monolayer capacity of 508 mg/g. This approach supplied a potential and effective solution of increasing profit and reducing carbon emissions in pulp production, which is very promising in terms of technical, economic, and environmental feasibilities to transform waste biomass into sustainable feedstocks.

Value-added utilization of lignin-derived aromatic oligomers as renewable charge-storage materials

Lignin-derived aromatic oligomers (LDAOs) are the primary components of lignin depolymerization products. They are typically utilized as renewable crosslinking agents or resin materials with a considerably lower application value than aromatic monomers. Notably, LDAOs are rich in quinone groups, which enable storage and release of charges. In this work, the feasibility of LDAOs as renewable charge storage materials was investigated. LDAOs were first reacted with formaldehyde to generate a synthetic polymer (SP-AOF) via a phenol-formaldehyde condensation reaction. SP-AOF was subsequently incorporated with reduced graphene oxide (rGO), namely rGO/SP-AOF. As expected, the hybrid electrode exhibited high specific capacitance (250 F/g), which was approximately three times higher than that of rGO (87 F/g). This was due to the presence of quinone groups in SP-AOF, which could contribute to the overall capacitance with pseudocapacitance. Moreover, the hybrid electrode was able to deliver a high specific capacitance of 210 F/g even at a high specific current of 10 A/g. 1H−13C heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) and phosphorus nuclear magnetic resonance spectroscopy (31P NMR) analyses revealed that SP-AOF displayed higher quinone content (3.76 mmol/g) than commercially available lignin (organosolv and alkali lignin), which resulted in higher energy storage performance. This study provides a promising strategy for the utilization of aromatic oligomers as raw materials to manufacture high-performance lignin-derived energy storage materials.

Green lignin‐based polyester nanofiltration membranes with ethanol and chlorine resistance

AbstractAs the main water treatment material, polymeric membranes inevitably suffer from membrane fouling. In this work, novel lignin‐based polyester composite nanofiltration membranes (NFM) with ethanol and chlorine resistance were fabricated via interfacial polymerization. Lignin alkali (LA), a green lignin derivative, typically treated as chemical waste in the paper industry, was employed as the aqueous monomer, trimesoyl chloride (TMC) is served as the organic monomer. The structure and separation properties of the lignin‐based NFM were studied, revealing that the dense polyester separation layer may show good performance for dye removal. The rejections of the optimized LA/TMC‐3 membrane with an excellent permeation flux of 13.9 kg m−2∙h−1 for rose Bengal sodium salt, brilliant blue, congo red, rhodamine B, MgSO4, and NaCl are 97.6%, 97.3%, 97.8%, 71.34%, 51.4%, and 31.8%, respectively. Moreover, the LA/TMC‐3 membrane also shows long‐term tolerance in ethanol and sodium hypochlorite solution; the rejection of LA/TMC‐3 to dye only decreases 8% after 8 days when immersed in alcohol, while the normalized rejection maintains 94% after 4000 ppm‐hours of continuous exposure to chlorine. This lignin‐based polyester membrane may broaden the sustainable utilization sphere of lignin derivatives, at that provide a referable direction for the development of membrane materials.

Effects of post-washing on pretreated biomass and hydrolysis of the mixture of acetic acid and sodium hydroxide pretreated biomass and their mixed filtrate

Effects of post-washing [one-volume water (I-VW) or double-volume water (Ⅱ-VW)] on pretreated hemp and poplar biomass and enzymatic hydrolysis of the mixture of HOAc and NaOH pretreated biomass and their mixed filtrate were investigated. Compared to I-VW, Ⅱ-VW increased 3.76–6.80% of glucan content in NaOH pretreated biomass, diminished lignin recondensation, and heightened cellulose-related FTIR peak intensities, crystallinity index, and lignin removal. The pH of mixed filtrate was around 4.80, precipitating the NaOH soluble lignin partially. Although Ⅱ-VW showed lower lignin recoveries than I-VW, their FTIR characteristics were equivalent to the commercial alkali lignin. Enzymatic hydrolysis at solid loadings of 2.5–10% (w/v) demonstrated that I-VW and Ⅱ-VW had marginal variations in sugar concentration and conversion efficiency, indicating that I-VW is sufficient for post-washing pretreated biomass. Glucose concentration exhibited a quadratic correlation with solid loading and hemp biomass reached the maximum glucose (43.88 g/L) and total sugar (57.08 g/L) concentrations with I-VW.

Co-upgrading of ethanol-assisted depolymerized lignin: A new biological lignin valorization approach for the production of protocatechuic acid and polyhydroxyalkanoic acid

This study presents a promising biological co-upgrading of ethanol-assisted depolymerized lignin (EDL) into protocatechuic acid (PCA) and polyhydroxyalkanoic acid (PHA) without any separation process. A depolymerized alkali lignin containing various G-lignin-type monomers at a concentration of 77 mg/mL was used for co-upgrading. An engineered Pseudomonas putida KT2440 strain was constructed by knocking out the protocatechuate 3, 4-dioxygenase, expression of the formaldehyde utilization pathway, and the expression of aldehyde dehydrogenase to enhance the efficiency of the ethanol utilization pathway. The growth and production of value-added bioproducts have been promoted by the utilization of formaldehyde, resulted in 6.73 ± 0.26 mg/L of PCA with a 17.5% (w/w) yield of total lignin monomers, and 303.66 ± 26.75 mg/L of PHA with 21.26% (w/w) of dry cell weight from 0.5 mL EDL. Moreover, the ethanol solvent used for lignin depolymerization was also utilized along with depolymerized lignin for co-upgrading to value-added products.

Oxidative valorisation of lignin into valuable phenolics: Effect of acidic and basic catalysts and reaction parameters

The aromatic nature of lignin makes it a good source for the production of numerous platform chemicals. The valorization of lignin into valuable compounds depends upon the type of bonds and functionality present in lignin. Here, we have studied the depolymerization of rice straw alkali lignin in N2 and O2 with acidic (ZSM-5), basic (MgO) catalyst and with their mixtures (1:1, 3:7 and 7:3). The effect of hydrogen peroxide on lignin depolymerization was also examined. Maximum yield of bio-oil (50 wt%) was obtained with pure ZSM-5 and 1 ml hydrogen peroxide in nitrogen atmosphere, while maximum conversion (60%) was observed in oxygen environment during the non-catalytic depolymerization of lignin. Bio-oil characterization through GC–MS showed maximum selectivity towards 2-methoxy-4-vinylphenol with 38.5 area% in the bio-oil of ZSM-5-N2. The bio-oils have also been characterized using 1H NMR, FT-IR and GC–MS.

Catalytic hydrothermal liquefaction of alkali lignin over activated bio-char supported bimetallic catalyst

Carbon-based support catalysts are beneficial on account of low material cost, prominent surface area, and stability at high temperature. In this study, biochar derived activated carbon (AC) supported metal catalysts were tested for hydrothermal liquefaction (HTL) of alkali lignin. Catalytic HTL of alkali lignin was carried out at various temperatures (260 to 300 °C) with varying catalysts quantity (5 to 20 wt%), and solvents (water, ethanol, methanol) for 15 min reaction time. As the reaction temperature increased from 260 to 300 °C, conversion increased from 76.2 to 85.5 wt%. Bimetallic catalyst Ni-Co/AC with ethanol solvent system at 280 °C gave highest bio-oil yield (72.0 wt%). Lignin catalytic depolymerization produces monomer phenolic compounds due to efficient breaking of the lignin macromolecule. Thus, the presence of catalyst and solvent increased the cleavage of β-O-4 bonds resulting in increased selectivity towards vanillin (32.3–36.2%).

MeRAV5 promotes drought stress resistance in cassava by modulating hydrogen peroxide and lignin accumulation.

Cassava, an important food and energy crop, is relatively more resistant to drought stress than other crops. However, the molecular mechanism underlying this resistance remains elusive. Herein, we report that silencing a drought stress-responsive transcription factor MeRAV5 significantly reduced drought stress resistance, with higher levels of hydrogen peroxide (H2 O2 ) and less lignin during drought stress. Yeast two-hybrid, pull down and bimolecular fluorescence complementation (BiFC) showed that MeRAV5 physically interacted with peroxidase (MePOD) and lignin-related cinnamyl alcohol dehydrogenase 15 (MeCAD15) invitro and invivo. MeRAV5 promoted the activities of both MePOD and MeCAD15 to affect H2 O2 and endogenous lignin accumulation respectively, which are important in drought stress resistance in cassava. When either MeCAD15 or MeRAV5 was silenced, or both were co-silenced, cassava showed lower lignin content and drought-sensitive phenotype, whereas exogenous lignin alkali treatment increased drought stress resistance and alleviated the drought-sensitive phenotype of these silenced cassava plants. This study documents that the modulation of H2 O2 and lignin by MeRAV5 is essential for drought stress resistance in cassava.

Mechanism of lignin degradation via white rot fungi explored using spectral analysis and gas chromatography-mass spectrometry

The mechanism of lignin degradation via white rot fungi was studied. Phanerochaete chrysosporium and Pleurotus ostreatus were used for all the experiments, i.e., measuring the concentration and structure of alkali lignins and studying the effect of the substrate concentration and enzyme activity on the removal. Gas chromatography-mass spectrometry was performed on the reaction liquid of the lignin degradation enzyme system. Alkali lignin had a characteristic absorption spectrum with a peak at approximately 280 nm. Precipitation in the laccase (Lac) degradation system occurred earlier, as well as being more obvious than that in the manganese peroxidase (Mnp) degradation system. The maximum removal was 29.4% in the Mnp degradation system at a concentration of 40 mg/L. The removal increased in a concentration-dependent manner in the Lac degradation system. The increase in Mnp and Lac enzyme activity led to an increased alkali lignin removal. The removal of the control group was significantly lower than the experimental degradation systems. The degradation mainly produced organic acids, esters, and aromatic substances. In conclusion, white rot fungi could effectively remove alkali lignin, in which precipitation played a major role, followed by enzymolysis; the enzymolysis was associated with the alkali lignin concentration and enzyme activity.

Preparation and performance of lignin-based waterborne polyurethane emulsion

The unmodified industrial Alkali Lignin (AL) was used as a hydrophilic chain extender to prepare a series of Lignin-based Waterborne Polyurethane (LWPU) emulsions with different lignin contents by step-growth addition polymerization with polypropylene glycol (PPG) and isophorone diisocyanate (IPDI). The lignin content in the series of LWPUs was determined by elemental analysis, with a maximum content of 24.68 wt%. The infrared spectrum and SEM diagram of the LWPU film show that the AL reacts well with isocyanate, the section of the film is flat and smooth, and there are no agglomerated lignin particles in the film, which indicates that the film is homogeneous. With the increase of AL content, the particle size of the LWPU emulsion decreased gradually from 233 nm to 127 nm, the Zeta potential decreased gradually from -44.8 mV to -56.9 mV, and the emulsion has good stability in the pH range of 5–12. The thermogravimetric analysis of the LWPU film show that the introduction of AL can improve the thermo stability of the polyurethane material, and the mechanical properties test results show that the highest tensile strength of the LWPU film can reach 1.29 times that of the pure polyurethane film. Ultraviolet aging test show that the introduction of AL can significantly improve the UV aging resistance of the polyurethane film. The lignin-based waterborne polyurethane emulsion prepared in this study can be used as a new type of bio-based polyurethane material.

Microwave Hydrophobized Lignin with Antioxidant Activity for Fused Filament Fabrication

The poor compatibility and aggregation propensity of lignin in nonpolar polymer matrices greatly limits its application in polymer blends and composites. We demonstrate an efficient, solvent-free, and catalyst-free microwave-assisted approach for hydrophobization of alkali lignin to enhance its compatibility with polylactide. Effective modification with up to 98% substitution of lignin’s hydroxyl groups was achieved under mild and catalyst-free reaction conditions. The modified acetylated and hexanoated lignins exhibited enhanced thermal stability and thermoplasticity, which were reflected by the good melt-extrusion and 3D printing properties of the corresponding polylactide/lignin blends. The tensile properties varied somewhat depending on the degree and type of substitution and the amount of hydrophobized lignin but in general the tensile properties were in the same range as those of polylactide. Blends consisting of up to 50 weight-% acetylated lignin were successfully extruded to filaments and 3D printed, demonstrating good processability and tensile properties regardless of the high lignin content, while it was not possible to extrude continuous filaments of polylactide and nonmodified alkali lignin even at low concentration (10 weight %). Additionally, the polylactide/acetylated lignin blends exhibited antioxidant activity as revealed by radical scavenging ability and improved thermo-oxidative stability with up to 40 °C increase in oxidation induction temperature compared to neat polylactide. The sustainable compatibilization strategy proposed herein paves the way for value-added utilization of lignin in fully biobased 3D printing filaments with improved oxidative stability.

Minimizing water consumption for sugar and lignin recovery via the integration of acid and alkali pretreated biomass and their mixed filtrate without post-washing

Excessive post-washing of pretreated biomass leads to huge water consumption and chemical loss. To address this issue, parallel HOAc and NaOH pretreatments of biomass followed by integration of their biomass and filtrate were investigated. Pretreatment effectiveness including morphology, crystallinity, and component recovery, were elucidated. Results showed that HOAc and NaOH in the mixed filtrate were neutralized to achieve a pH of around 4.80 prompting the alkali lignin precipitation. Lignin (46.01 and 48.38 g/kg-biomass for hemp and poplar, respectively) exhibiting comparable FTIR characteristics with the commercial alkali lignin was recovered. Compared to sodium acetate buffer as a control, integrating HOAc and NaOH pretreated biomass and their mixed filtrate for enzymatic hydrolysis boosted total sugar concentration (hemp: 42.90 vs. 38.27 g/L; poplar: 43.18 vs. 38.76 g/L) without compromising glucose yield (hemp: 70.86 vs. 70.69%; poplar: 66.48 vs. 69.48%) but improving xylose yield (hemp: 60.10 vs. 35.92%; poplar: 56.90 vs. 29.39%).

Tunable Boc modification of lignin and its impact on microbial degradation rate

A new type of modified lignin, lignin-p-Boc, was obtained through reaction with di-tert-butyl dicarbonate (Boc2O) in aqueous media catalyzed by 4-dimethylaminopyridine (DMAP). Boc modification occurred regardless of type of lignin, was tunable, and proceeded well in recovering lignin at high purity from sodium lignosulfonate (a common byproduct from pulping industry; lignin content: 60%). Lignin-p-BOC was demonstrated as a potential reactive filler in green plastic and as a potential crosslinker in design of bioresorbable composite polymeric implants. Furthermore, the effect of the modification on breakdown rate of alkali lignin by microbes was investigated, and results showed that the modification substantially decreases the breakdown rate. The tunable Boc modification process was designed via a system thinking, including availability of raw lignin, economical/green modification, potentiality of drop-in-change to current thermoplastic processing, modification impact on microbial degradability/disposed environment at the end of use life; hence the holistic consideration makes this alternative method for upgrade of technical lignins very practical for future industrial application. Via “in-situ” forming “easily breakable covalent bonds” with existing thermopolymers inside, Lignin-p-BOCs are also promising to play an important role as both excellent binders via “random match” and reductants in transforming linear plastic waste into circular plastics.

Characterization and Evaluation of Hydrothermal Liquefaction Char from Alkali Lignin in Subcritical Temperatures.

An evaluation of hydrothermal liquefaction (HTL) char is investigated in this work. Morphological studies, N2 adsorption behavior, FTIR analysis, thermal behavior, and elemental composition are studied. The HTL char yield showed an increase with higher operating temperatures. It increased from 11.02% to 33% when the temperature increased from 573 K to 623 K. At lower temperatures, the residence time showed an impact on the yield, while close to the critical point, residence time became less impactful. Elemental analysis showed that both higher operating temperatures and longer residence times increased the nitrogen content of the chars from 0.32% to 0.51%. FTIR analysis suggested the char became more aromatic with the higher temperatures. The aliphatic groups present diminished drastically with the increasing temperature. Residence time did not show a significant impact as much as the temperature when considering the functional group elimination. An increase in operating temperatures and residence times produced thermally stable chars. HTL char produced at the lowest operating temperature and showed both the highest surface area and pore volume. When temperature and residence time increase, more polyaromatic char is produced due to carbonization.

Improving fire behavior and smoke suppression of flame‐retardant PBS composites using lignin chelate as carbonization agent and catalyst

AbstractA copolymer of alkali lignin and polyacrylamide was fabricated by graft copolymerization, and further chelated with Fe3+. The obtained lignin chelate with star structure was used as synergistic agent and catalyst with the incorporation of intumescent flame retardants (IFRs) to prepare flame‐retarded poly (butylene succinate) (PBS) composites. The replacement of IFR by lignin chelate favors the enhancement of mechanical performance, resulting in the synchronous improvement of tensile and flexural properties. Compared with the specimen used 25 wt% IFRs (75P/25I), the tensile strength, flexural strength, and modulus of specimen prepared by 23 wt% IFRs and 2 wt% lignin chelate (75P/23I/2LC) exhibited significant increased. A synergistic effect between IFR and lignin chelate occurred when they were combined with an appropriate ratio. When IFR and lignin chelate loadings were 24 and 1 wt%, respectively (75P/24I/1 LC), the limited oxygen index (LOI) value of 36.2% and UL‐94 V0 rate of composite could be achieved. Compared with 75P/25I, the char residue mass of 75P/24I/1 LC increased by 35.7%. Moreover, SEM images indicated that a more compact, smooth, and continuous char layer of 75P/24I/1 LC could be formed during combustion. The peak heat release rate (pHRR) and total heat release (THR) of 75P/24I/1 LC decreased by 58.9% and 9.9% compared with PBS, also decreased by 10.3% and 4.8% compared with 75P/25I, respectively. TGIR and FTIR analysis also indicated that lignin chelate exhibited an excellent synergistic effect with IFRs, and gave PBS a good flame retardancy by making contribution to char‐formation and gas‐phase flame retardancy. This study provides an alternative way for the application of natural polymers such as lignin in flame retardant materials.