Lignin Recovery Research Articles

Optimizing corncob pretreatment with eco-friendly deep eutectic solvents to enhance lignin extraction and cellulose-to-glucose conversion

Deep eutectic solvents (DES) are an eco-friendly, cost-effective alternative to traditional ionic liquids for biomass pretreatment, with unique characteristics encompassed by hydrogen bond donor (HBD), the molar ratio of hydrogen bond acceptor (HBA) to HBD, temperature, and time affecting efficiency. Despite its potential, a comprehensive study exploring the interplay of these factors is limited. This study explores the optimization of pretreatment variables using choline chloride/lactic acid (1:5) via the response surface method (RSM). It aims to evaluate the effects of time and temperature on lignin extraction, cellulose-to-glucose conversion, and hemicellulose removal. Employing a 22 central composite design with temperature (80–140 °C) and time (2–6 h) as variables, optimal conditions were 123 °C for 6 h. Results include 90.08±1.42 % lignin extraction, 68.77±6.9 % cellulose-to-glucose conversion, and 77.34±0.85 % hemicellulose removal, with 52.52±8.07 % lignin recovery. The fractions of pretreated CC and lignin recovered in the optimal condition found were characterized by X-ray diffraction (XDR), Fourier transform infrared spectroscopy (FTIR), 1H, 13C, 2D-HSQC NMR spectroscopy, Thermogravimetric analysis (TGA/DTG), Gel Permeation Chromatography (GPC) to elucidate chemical characteristics of the materials obtained and facilitate downstream valorization. High efficiency was achieved in lignin extraction and cellulose conversion, and addressing solvent viscosity and DES recycling will further enhance the potential for industrial scalability.

Pilot-scale nanofiltration and techno-economic evaluation of lignin recovery from kraft black liquor

This pilot-scale study investigates the possibility of using nanofiltration after ultrafiltration to improve lignin recovery from kraft black liquor in a pulp mill. The nanofiltration step can increase overall lignin recovery and provide a clean permeate that could be used in the smelt dissolving tank to produce green liquor. Nanofiltration of kraft black liquor ultrafiltration permeate was performed under two operating conditions: (A) 50 °C at 25 bar, and (B) 70 °C at 15 bar, which led to a lignin retention of 82% and 75%, respectively. Experimental data from condition A were used in a techno-economic analysis where four scenarios were evaluated: (1) a reference scenario, without lignin separation; (2) a scenario in which the ultrafiltration permeate was returned to the evaporators; (3) a scenario including ultrafiltration and nanofiltration, where the nanofiltration permeate was sent to the smelt dissolving tank; and (4) a scenario including ultrafiltration and nanofiltration, where the nanofiltration retentate was sent to the evaporators and the nanofiltration permeate to the smelt dissolving tank. The reduced energy consumption of the evaporators in scenario 4 resulted in an increase in sold electrical power of 19.4 GWh/y, giving a pay-back time on the investment in the nanofiltration plant of 2.2 years.

Isolation and Structural Characterization of Natural Deep Eutectic Solvent Lignin from Brewer's Spent Grains.

Brewer's spent grains (BSG) offer valuable opportunities for valorization beyond its conventional use as animal feed. Among its components, lignin-a natural polymer with inherent antioxidant properties-holds significant industrial potential. This work investigates the use of microwave-assisted extraction combined with acidic natural deep eutectic solvents (NaDESs) for efficient lignin recovery, evaluating three different NaDES formulations. The results indicate that choline chloride-lactic acid (ChCl-LA), a NaDES with superior thermal stability as confirmed via thermogravimetric analysis (TGA), is an ideal solvent for lignin extraction at 150 °C and 15 min, achieving a balance of high yield and quality. ChCl-LA also demonstrated good solubility and cell disruption capabilities, while microwaves significantly reduced processing time and severity. Under optimal conditions, i.e., 150 °C, 15 min, in the presence of ChCl-LA NaDES, the extracted lignin achieved a purity of up to 79% and demonstrated an IC50 (inhibitory concentration 50%) of approximately 0.022 mg/L, indicating a relatively strong antioxidant activity. Fourier transform infrared (FTIR) and 2D-HSQC NMR (heteronuclear single quantum coherence nuclear magnetic resonance) spectroscopy confirmed the successful isolation and preservation of its structural integrity. This study highlights the potential of BSG as a valuable lignocellulosic resource and underscores the effectiveness of acidic NaDESs combined with microwave extraction for lignin recovery.

Streamlined fractionation for recovery of high-yield xylo-oligosaccharides, pure lignin and ethanol from poplar using short-chain organic acid/pentanol biphasic system

Biphasic pretreatment offers a sustainable method by integrating the fractionation of hemicellulose, lignin, and cellulose into a single process, thereby enhancing biomass resource utilization while reducing environmental impact. However, this process faces the challenge of diverse hemicellulose products with low added value. This study employed organic acid-catalyzed water/pentanol biphasic pretreatment to selectively convert hemicellulose into xylooligosaccharides (XOS), while simultaneously separating lignin and cellulose. Both the organic acids and pentanol used are biodegradable and compatible. The lactic acid (LA)/pentanol biphasic system was particularly effective for XOS production and lignin removal, attributed to the high acidity of LA and its relatively low partition coefficients in the water/pentanol system, crucial factors influencing hemicellulose and lignin separation efficiency. The XOS yields reached 46.9 %, while the lignin removal rate was 74.6 %. Additionally, LA/pentanol pretreatment significantly enhanced cellulose digestibility, demonstrated by an ethanol production of 54.1 g/L during simultaneous saccharification fermentation at 15 % solids loading. The recovered lignin from the organic phase retained the structural characteristics of native lignin. It also had a low molecular weight and abundant phenolic hydroxyl groups, indicating its suitability for further valorization. Pentanol maintained its performance after four cycles of reuse, demonstrating the stability and reusability of the solvent system. This study highlighted the potential of the LA/pentanol biphasic system for simultaneous hemicellulose conversion and lignin isolation, offering a simplified and sustainable one-step valorization route for biomass.

Study of Purified Cellulosic Pulp and Lignin Produced by Wheat Straw Biorefinery

With the world population rising, wheat straw production is expected to reach 687–740 million tons per year by 2050. Its frequent application as a fuel source leads to air, water, and soil pollution. Limited literature exists on methods for separating components of residual wheat straw. Optimal conditions for organosolv pulping of hydrolyzed wheat straw include 3% FeCl3·6H2O as a catalyst, a biomass-to-solvent ratio of 1:15 (m/v), and 50% ethanol:water as cooking liquor at 200 °C for 30 min. Desilication conditions involve extraction with 7.5% Na2CO3 at a biomass-to-solvent ratio of 1:20 (m/v) treated at 115 °C for 60 min. Lignin from hydrolyzed wheat straw showed similar properties to organosolv lignin from untreated straw, with minimal lignin alteration during hydrolysis. Hydrolysis significantly degraded cellulose. A 41% lignin recovery rate with 95% purity was achieved from pre-extracted hydrolyzed straw. Recovered cellulose after silica removal had 2% ash and 87% purity. The innovation of this process lies in the development of a comprehensive, sustainable, efficient, and economically viable biorefinery process that efficiently separates key components of wheat straw, i.e., xylose, lignin, cellulose, and silica, while addressing environmental pollution associated with its traditional use as fuel.

Urea-lactic acid as efficient lignin solvent and its practical utility in sustainable electrospinning

The development of lignin-based materials presents a promising avenue for advancing green chemistry and mitigating environmental impact. However, the key challenge lies in the processability of lignin, which significantly affects its practical applications. Addressing the issues related to lignin's complex structure, variability, and reactivity is crucial for optimizing its incorporation into high-performance materials. Therefore, in this study we explore the efficacy of a urea-lactic acid-based deep eutectic solvent (ULA) for the dissolution of kraft lignin, aiming to enhance its practical utility in sustainable electrospinning processes, for the first time. Results of elemental analysis, IR and 2D NMR spectroscopy, provide crucial insights into the structural properties of the regenerated material post-DES treatment. The findings confirm a high lignin recovery rate, reaching up to 96.6 % for samples dissolved at 100°C. Additionally, 2D NMR analysis indicates that the process leads to partial esterification of lignin with lactate ions. The ability of the studied DES to effectively solubilize lignin underscores its potential as an efficient lignin solvent and facilitates the fabrication of lignin-based nanofibers via electrospinning. The incorporation of this DES in electrospinning processes promises significant advancements in the development of sustainable, lignin-derived materials and offers a green alternative for production of high-performance nanofibers. Preliminary results of electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements confirm that the EDLC with prepared hydrogel electrolyte demonstrates attractive electrochemical properties (specific capacitance, CSP = 95 F g–1; series resistance RS = 2.2 Ω; charge transfer resistance, RCT = 1.6 Ω), which are comparable with the reference cell based on a commercial glass fibre separator. Hence, the DES-assisted-electrospinned lignin membrane can be viewed as a potential gel electrolyte matrix for practical use in construction of sustainable energy storage devices.

Optimization of Cellulose Recovery Using Deep Eutectic Solvent Fractionation: A Response Surface Method Approach

Lignocellulosic biomass is a crucial renewable energy source for producing biofuels and valuable compounds, making it an attractive alternative to fossil resources. In this study, an environmentally friendly method was developed for cellulose fractionation from sugarcane bagasse using deep eutectic solvents (DESs), focusing on achieving high cellulose purity and specific physicochemical properties. The effects of different parameters were investigated by comparing four DESs: choline chloride–lactic acid (ChCl-LA), choline chloride–glycerol (ChCl-G), choline chloride–urea (ChCl-U), and choline chloride–polyalcohol (ChCl-P), under various reaction temperatures and times. The fractionation process was conducted under standard conditions at a temperature of 100 °C for 120 min with a 1:1 molar ratio. The results indicated that all DESs produced comparable cellulose recovery, ranging from 91.83% to 97.07%. A relatively high cellulose recovery was observed in the presence of ChCl-LA, at 95.47%. In addition, ChCl-LA demonstrated the highest efficiency in removing hemicellulose and lignin, at 95.36% and 93.38%, respectively, and high recovery yields of 70.45% for hemicellulose, and 70.66% for the lignin fraction. The fractionation conditions were further optimized using response surface methodology (RSM), achieving a ChCl-LA ratio of 1:2 v/v at 120 °C for 120 min. This resulted in impressive yields: 97.86% cellulose recovery, 96.50% hemicellulose removal, 74.40% hemicellulose recovery, 77.3% lignin recovery, and 71.5% lignin yield from sugarcane bagasse. These results closely match the predicted values, emphasizing the effectiveness of the process and its potential for economic application in lignocellulosic biorefinery operations.

Effect of sintering temperature on ceramic membrane fabricated using coal flyash and natural clay for lignin recovery

This study explores the utilization of coal fly ash combined with natural clay as a precursor for creating ceramic membranes through the uniaxial compaction method, aiming at lignin separation. These membranes were sintered at varying temperatures from 600 to 1000 °C. Thermal Gravimetric Analysis (TGA) revealed the robust thermal stability of the membranes. Fourier Transform Infrared (FTIR) analysis affirmed the presence of silica and alumina within the membranes. X-ray Diffraction (XRD) peaks indicated the crystalline structure and the presence of metal oxides originating from the fly ash and clay components. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images illustrated the porous nature and rough surface of the ceramic membranes. The average pore radius of the fabricated membrane expanded from 43.12 to 7.91 nm with increasing temperature. Concurrently, membrane flux decreased from 4.13 to 0.96 ×10−6 m3/m2 s with higher temperatures. Lower contact angles indicated the hydrophilic properties of membranes. All membranes exhibited superior corrosion resistance and negative zeta potential, owing to the significant silica content in the fly ash. Lignin separation efficiency increased from 65 % to 81 % with increasing temperatures. The optimal sintering temperature was determined to be 800 °C, achieving a lignin recovery greater than 76 % and a membrane permeability of about 7×10−9 m3/m2 s kPa. Thus, the fly ash-clay-based ultrafiltration membranes synthesized in this study offer the potential for lignin biomass recovery from biorefinery effluent.

A novel deep eutectic solvent-methyl isobutyl ketone biphasic system for the catalytic conversion of wheat straw to furfural and recovery of cellulose and lignin

Currently, the conversion of lignocellulosic biomass into furfural using deep eutectic solvents (DES) as the solvent and catalyst has many shortcomings including low furfural yields and inefficient resource utilization. To address these issues, a novel effective DES-methyl isobutyl ketone (DES-MIBK) reaction system was designed and used to catalyze the transformation of wheat straw to furfural and separate/recover cellulose and lignin in this work. The results showed that the DES-MIBK system could significantly improve furfural yield of up to 76.2 % at a mild condition (at 100 °C for 60 min). Furthermore, cellulose and lignin were fractionated and recovered from the reaction residues and the lignin yield reached 68.7 %. Moreover, the recovered cellulose exhibits high crystallinity (CrI=67.7 %). and the obtained lignin also has good uniformity with a small polydispersity index (PDI=2.36), and the results of FT-IR and 2D NMR indicated that the obtained lignin retains its fundamental structure. This research highlights that the innovative DES-MIBK system has a high-efficient in the production of furfural and the recovery of lignin and cellulose, which could provide a novel strategy for the high-value and sustainable application of lignocellulose biomass.

Response surface methodology to optimize membrane cleaning in nanofiltration of kraft black liquor

Better understanding of membrane fouling and cleaning can help implementation of membrane filtration processes in the pulp and paper industry. The aim of this study was to optimize membrane cleaning in the nanofiltration of kraft black liquor ultrafiltered permeate for the recovery of lignin. This work wants to assess whether the cleaning process removes the main foulants; as well as the economic viability of the optimized cleaning compared to a standard cleaning in a nanofiltration membrane plant on industrial scale.The optimization of membrane cleaning was investigated using the response surface methodology. The factors studied were time, temperature, and cleaning agent (Ultrasil 110) concentration, and flux recovery was used to evaluate the success of cleaning. Experiments were performed on laboratory scale where flat-sheet polymeric membranes were fouled with kraft black liquor ultrafiltered permeate and cleaned using various combinations of the three factors.The model developed predicted a flux recovery of 88 % when cleaning was performed for 60 min with a solution of 0.8 wt% Ultrasil 110 at 40 °C. The flux recovery measured experimentally with these cleaning parameters was 80 %. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy analysis confirmed that the optimized cleaning removed the main foulants from the membrane surface. Moreover, increasing the cleaning agent concentration or the cleaning temperature did not always lead to a higher flux recovery. The techno-economic evaluation revealed that 16 % of the cleaning costs could be saved by optimizing the cleaning process.

Modeling lignin extraction with ionic liquids using machine learning approach

Lignin, next to cellulose, is the second most common natural biopolymer on Earth, containing a third of the organic carbon in the biosphere. For many years, lignin was perceived as waste when obtaining cellulose and hemicellulose and used as a biofuel for the production of bioenergy. However, recently, lignin has been considered a renewable raw material for the production of chemicals and materials to replace petrochemical resources. In this context, an increasing demand for high-quality lignin is to be expected. It is, therefore, essential to optimize the technological processes of obtaining it from natural sources, such as biomass. In this work, an investigation of the use of machine learning-based quantitative structure-property relationship (QSPR) modeling for the preliminary processing of lignin recovery from herbaceous biomass using ionic liquids (ILs) is described. Training of the models using experimental data collected from original publications on the topic is assumed, and molecular descriptors of the ionic liquids are used to represent structural information. The study explores the impact of both ILs' chemical structure and process parameters on the efficiency of lignin recovery from different bio sources. The findings give an insight into the extraction process and could serve as a foundation for further design of efficient and selective processes for lignin recovery using ionic liquids, which can have significant implications for producing biofuels, chemicals, and materials.

Deep eutectic solvent pretreatment of sugarcane bagasse for efficient lignin recovery and enhanced enzymatic hydrolysis

This study explores the sugarcane bagasse (SCB) pretreatment with two deep eutectic solvents (DESs) prepared from choline chloride (ChCl) as a hydrogen bond acceptor (HBA) to two hydrogen bond donors (HBD): oxalic acid (OA) and trifluoroacetic acid (TFA) for lignin recovery and enhancing enzymatic saccharification. The pretreatment conditions, reaction time, temperature, and DES concentration were optimized using response surface methodology. The two DESs showed a lignin yield of 74.67 ± 2.75 and 83.50 ± 2.65 mg per gm of SCB, respectively. Enzymatic hydrolysis of the cellulose-enriched material (CEM) obtained after pretreatment showed an enhanced RS yield of around 4-fold compared to the untreated SCB. The CEM was characterized using FTIR, Powder X-ray diffraction, and Scanning Electron Microscopy. The recovered lignin characteristics were studied using FTIR, 1H NMR, and 2D-HSQC NMR analysis. The FTIR spectra of lignin show the presence of aromatic skeletal vibrations, -OH, -CH, C-O stretching vibration, and aromatic C-H deformation. Furthermore, the pretreatment solvent recyclability studies were conducted to evaluate the effectiveness of DES for a sustainable biorefinery process.

Synthesis and Characterization of Lignin-Silver Nanoparticles

Metal nanoparticle synthesis via environmentally friendly methods is gaining interest for their potential advantages over conventional physico-chemical approaches. Herein, we propose a robust green synthesis route for lignin-modified silver nanoparticles, utilizing the recovery of lignin as a renewable raw material and exploring its application in valuable areas. Through a systematic approach combining UV-Vis spectroscopy with AAS and DLS, we identified repeatable and scalable reaction conditions in an aqueous solution at pH 11 for homogeneous silver nanoparticles with high uniformity. The TEM median sizes ranged from 12 to 15 nm with circularity between 0.985 and 0.993. The silver nanoparticles yield exceeded 0.010 mol L−1, comparable with traditional physico-chemical methods, with a minimal loss of silver precursor ranging between 0.5 and 3.9%. Characterization by XRD and XPS revealed the presence of Ag-O bonding involving lignin functional groups on the pure face-centered cubic structure of metallic silver. Moreover, the lignin-modified silver nanoparticles generated a localized thermal effect upon near-infrared laser irradiation (808 nm), potentially allowing for targeted applications in the biomedical field. Our study showcases the potential of lignin as a renewable reducing and capping agent for silver nanoparticle synthesis, addressing some shortcomings of green synthesis approaches and contributing to the development of suitable nanomaterials.

Green approach on pretreatment of rice straw using deep eutectic solvent for lignin recovery and efficient hydrolysis

Green approach on pretreatment of rice straw using deep eutectic solvent for lignin recovery and efficient hydrolysis

High extraction and excellent anti-UV and anti-oxidant proprieties of lignin from Reseda Luteola L. waste by organosolv process

Lignin is an abundant natural biopolymer found in plant cell walls. Lignin can come from tinctorial plants, whose residual biomass after dye extraction was typically discarded as waste. The main objective of this study was to extract lignin from the residual biomass of Reseda luteola L. using an organosolv process and to optimize the extraction conditions. The extracted lignin was characterized, and its potential applications as an antimicrobial, anti-oxidant, and anti-UV agent were investigated. Response surface methodology based on a Box-Behnken design was employed to optimize the lignin extraction conditions (organic acid concentration, material-to-liquid ratio, extraction time). The extracted lignin was comprehensively characterized using NMR, FTIR, XRD, SEM-EDX, TGA, DSC, and UV–Vis techniques. The optimal extraction conditions yielded a remarkably high lignin recovery of 62.41 % from the plant waste, which was rarely achieved for non-wood plants in previous works. The extracted lignin exhibited excellent thermal stability and radical scavenging anti-oxidant activity but no significant antimicrobial effects. Treating wool fabrics with lignin nanoparticles substantially enhanced UV protection from the “good” to “excellent” category based on the UPF rating. This sustainable valorization approach converted abundant tinctorial plant waste into high-purity lignin with promising anti-oxidant and UV-blocking properties suitable for various applications.

Cellulose and lignin purified from Metroxylon sagu palm fronds by a new technology with 2-methylanthraquinone cooking and peroxymonosulfuric acid bleaching

The demand for high-purity cellulose, optimization of wood utilization, and environmentally friendly processes has increased in dissolving pulp (DP) production. Sago palm fronds (SPF), an abundant agricultural waste in Indonesia, hold great potential as a raw material for cellulose, hemicellulose, and lignin production. This study aimed to explore the production of from SPF by employing a combination of prehydrolysis, soda cooking with 2-methylanthraquinone (MAQ) as a green additive (PHS-MAQ), and totally chlorine-free (TCF) bleaching with peroxymonosulfuric acid (Psa). Furthermore, lignin was recovered from the black liquor of PHS-MAQ. The results showed that prehydrolysis at 150 ºC for 3 h, followed by soda-MAQ cooking at 160 ºC for 1.5 h using 0.03% of MAQ, 23% active alkali (AA), and a five-stage bleaching with oxygen (O), Psa, alkaline extraction with hydrogen peroxide (Ep), Psa, and Ep successfully produced high-purity cellulose as DP, with properties of 94.3% α-cellulose content, 89.9% ISO brightness (SNI ISO 2470–1:2016), 9.1 cP viscosity, and 0.13% ash content. Moreover, the soda-MAQ cooking method exhibited superior delignification compared to prehydrolysis kraft (PHK) and prehydrolysis soda (PHS) processes in a range of kappa numbers of 9.4–22.6 at 17–25% AA. The inclusion of MAQ increased pulp yields by 4.6–4.9% and decreased kappa number by 1.6–3.1 compared to the PHS without additives at similar AA. Lignin was separated from the PHS-MAQ, with yields of 69–77%. This work demonstrated the suitability of SPF processed by PHS-MAQ cooking and Psa bleaching for the preparation of viscose rayon and cellulose derivatives. The lignin recovery could be an attractive biorefinery process in modern pulp mills.

Extraction, recovery, and characterization of lignin from industrial corn stover lignin cake

Lignin utilization in value-added co-products is an important component of enabling cellulosic biorefinery economics. However, aqueous dilute acid pretreatments yield lignins with limited applications due to significant modification during pretreatment, low solubility in many solvents, and high content of impurities (ash, insoluble polysaccharides). This work addresses these challenges and investigates the extraction and recovery of lignins from lignin-rich insoluble residue following dilute acid pretreatment and enzymatic hydrolysis of corn stover using three extraction approaches: ethanol organosolv, NaOH, and an ionic liquid. The recovered lignins exhibited recovery yields ranging from 30% for the ionic liquid, 44% for the most severe acid ethanol organosolv condition tested, and up to 86% for the most severe NaOH extraction condition. Finally, the fractional solubilities of different recovered lignins were assessed in a range of solvents and these solubilities were used to estimate distributions of Hildebrand and Hansen solubility parameters using a novel approach.

From Pulp to Aromatic Products-Reaction Pathways of Lignin Depolymerization.

This study investigated the depolymerization of lignin into aromatic monomer compounds under hydrothermal conditions. A reaction scheme highlighting secondary alkylation reactions as well as the molecular weight shift was developed based on the experimental data. Lignin is produced in large quantities in paper production and dissolved in what is known as black liquor (BL). To avoid lignin recovery as an additional process step, BL is used directly as feedstock in the hydrothermal liquefaction (HTL) in this work. We performed various batch experiments in micro autoclaves with BL and model substances at different reaction temperatures (TR = 250-400 °C) and a holdingtime of tR = 20 min, as well as continuous experiments (TR = 325-375 °C, tR = 20 min). We were able to show that different derivatives of catechols are the main products among the monomers in our process. With the help of the model substance experiments, we were able to work out three main reactions: demethoxylation, demethylation, and alkylation. This behavior could be observed in the case of BL from hardwood as well as from softwood. 31P nuclear magnetic resonance (NMR) spectroscopy analysis has shown that these reactions take place on aromatic monomers as well as on larger aromatic oligomer structures. At higher temperatures, a large fraction of the carbon ends up in the solid product, while the yields of the monomers decrease sharply. 13C NMR spectroscopy of the solid material shows that the monomers are probably incorporated into the solid phase by repolymerization. We were also able to see this effect using size exclusion chromatography analysis based on the relative molecular weight. From all of the analytical results of the products, a reaction scheme was developed that describes the reaction pathways of the lignin during HTL. Based on this, a reaction kinetic model can be developed in the next step.

Intensification of evaporative precipitation of lignin in a spinning disc evaporator

A continuous process for the evaporative precipitation of lignin derived from Organosolv black liquor was successfully developed and implemented in a spinning disc evaporator (SDE). A maximum of 95 % of the lignin was recovered at a disc speed of 1200 rpm, black liquor feed flow rate of 1 ml s−1 on a smooth disc surface heated to 100 ⁰C. These optimal flow rate and disc speed values corresponded to conditions which maximised residence time to <1 s in 4 disc passes without compromising on the rate of evaporative heat transfer. The lignin precipitate did not have any detectable impurities present after being washed and dried. The particle size for the lignin precipitate was in the region of 3 – 9 µm with minor agglomeration occurring, providing good filterability. A scaled up version of the process was modelled for benchmarking purposes and it was found that the SDE had a better theoretical performance than a falling film evaporator (FFE) system developed for the same process, with the energy consumption reduced by 23% and a higher lignin recovery rate per volume of black liquid processed once adjusted for processing time (38.1 g L−1 h−1 for the SDE vs. 3.23 g L−1 h−1 for the FFE).

Steam Explosion-Based Method for the Extraction of Cellulose and Lignin from Rice Straw Waste

This paper focuses on the optimisation of an efficient extraction process for cellulose and lignin from rice straw waste from the Albufera of Valencia using the steam explosion method. This method is particularly pertinent given the environmental and economic challenges posed by the current disposal practices of agricultural waste. The technique comprises a high-temperature cooking stage followed by instantaneous decompression, effectively altering the biomass’s physical and chemical properties to enhance its surface area and porosity. Our adaptation of the steam explosion technique specifically addresses the challenges of rice straw waste, marking a significant departure from previous applications. This innovation is crucial in addressing the urgent need for more sustainable waste management practices, as it effectively deconstructs the lignocellulosic matrix of rice straw. This facilitates the selective extraction of cellulose at a 70% efficiency, with a 20% yield and the subsequent recovery of lignin. The results of this study are significant for sustainable biomaterial production, offering novel insights into optimising these crucial biomass components. By refining the process and focusing on critical parameters, our work advances the application of steam explosion methods for agricultural waste, enhancing efficiency and sustainability. By utilising rice straw biowaste, this research not only proposes a solution to a pressing environmental issue but also demonstrates the potential to create new market opportunities, increase the economic value for rice producers, and significantly reduce the environmental footprint of existing waste disposal methods. The holistic and ecological approach of this study underscores the vital need for innovative strategies in agricultural waste management, positioning the valorisation of rice straw waste as a key component in the pursuit of environmental sustainability.