An integrated closed loop biorefining process for sustainable multi-product valorisation with zero liquid discharge

Abstract

A cost-effective biorefining process has been developed to produce multiple products, including mono-saccharomate syrup, poly-phenolic precursor, and cellulosic derivatives such as (R)-cellulose, (µ)-cellulose and (n)-cellulose, from surplus crop residues. This process involves several steps, including saccharomate recovery, solid-liquid separation, poly-phenol extraction, blanching, density separation, depolymerization, and drying. Furthermore, the by-products generated at each stage of the biorefining process can be utilized to increase the value of the overall process by incorporating a photosynthetic resource recovery strategy. The methods used for extraction and treatment vary depending on the composition and type of the feedstock biomass.

Description

[0001] AN INTEGRATED CLOSED LOOP BIOREFINING PROCESS FOR SUSTAINABLE MULTI-PRODUCT VALORISATION WITH ZERO LIQUID DISCHARGE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to an integrated closed loop biorefining process for sustainable multi-product valorisation with zero liquid discharge. In particular, the present invention relates to a process for producing pharmaceutically valuable chemicals and products from surplus agricultural waste biomass by selective separation. More particularly, the instant invention aims towards sequential extraction of biomass constituents for the production of a myriad product portfolio by using low input of energy and chemicals. The extraction and treatment strategies vary with the composition and type of the Agri-waste biomass. The resulting products are subsequently used for their respective commercial applications. Multi product oriented extraction through biorefinery approach can be considered as an amenable strategy with limited ecological foot prints supporting circular economy as well. The products obtained by the process of the instant invention have potential applications in pharmaceutical, food, and packaging sectors. The invention shall help attain the 12thsustainable development goal of responsible consumption and production.

[0004] BACKGROUND OF THE INVENTION

[0005] The agricultural waste biomass referred to in the invention includes rice straw, sugarcane bagasse, wheat straw, and cotton stalks, which are all examples of lignocellulosic biomass. This type of biomass is composed of cellulose (35-45% by weight), hemicellulose rich in xylose (20-25% by weight), silica (4-14% by weight), and lignin (18-25% by weight). The valorisation of lignocellulosic resources into biofuel and bioproducts involves breaking down the feedstocks, hydrolyzing them, and separating out the different components. For example, the bioconversion process for lignocellulosic materials into biofuel (such as ethanol) typically consists of four basic steps: pretreatment, enzyme hydrolysis, fermentation, and product recovery.

[0006] There are also procedures in place for extracting specific components from biomass feedstock, which always begin with a pretreatment phase that reduces the size of the biomass and increases the available surface area for further processing. The success and cost-effectiveness of the bioconversion process is greatly impacted by pretreatment, and various methods have been developed using mechanical force, steam, acid, alkaline, biological agents, or a combination thereof.

[0007] The biorefining process, aimed at maximizing the value of lignocellulosic biomass, is gaining attention in recent years. Several prior art inventions have focussed on biorefining the lignocellulosic biomass with mechanical methods (grinding, extrusion, milling, and crushing), thermal methods (steam explosion and autohydrolysis), and chemical methods (acid and alkali treatments). Multi product-oriented extraction through biorefinery approach can be considered as an amenable strategy with limited ecological foot prints supporting circular economy as well.

[0008] Reference may be made to WO 2014 / 106221 Al, that describes a process and apparatus for producing fermentable sugars, cellulose solids, and lignin from lignocellulosic biomass. The invention has presented a method for dividing biomass into fractions, which involves: dividing the biomass with the presence of a solvent for lignin, sulphur dioxide, and water to produce a mixture containing hemicellulose, cellulose-rich solids, and lignin; converting the hemicellulose in the mixture into hemi-cellulosic monomers through hydrolysis; breaking down the cellulose-rich solids to produce glucose; and obtaining the hemi-cellulosic monomers and glucose as fermentable sugars. The addition of a metal sulphite or metal bisulphite additive is used to directly or indirectly react with lignin to create sulfonated lignin, which can improve the separation of lignin and increase the value of lignin as a co-product. However, sulphur dioxide, metal sulphites, and metal bisulphites have numerous drawbacks and negative effects on the environment. SO2 is an odourless gas, can adversely affect the respiratory system, causes chronic bronchitis, asthma, and emphysema. It also contributes to acid rain formation, harming the ecosystems and buildings. Metal sulphites and bisulphites are associated with health and environmental concerns. Ingesting sulphites can lead to respiratory and gastrointestinal symptoms, while direct contact causes skin and eye irritation. These substances, when released into water bodies, pose a toxic threat to aquatic life.

[0009] Reference may be made to WO2014092873A1, which provides methods for improving lignin separation during biomass processing. The process involves the use of an acid for releasing sugars and a solvent such as ethanol for lignin. A digester is utilized to fractionate the feedstock in the presence of sulphur dioxide, water and the solvent for lignin, producing a mixture of hemicellulose, cellulose-rich solids and lignin. A solid additive (Gypsum) is added to the digester to combine with at least part of the lignin, and the mixture of the lignin and solid additive is separated from the mixture before hemicellulose recovery. Optionally, the solid additive can also be introduced in the hydrolysis reactor for converting hemicellulose oligomers to monomers, which improves the separation of lignin catalysed by acid. However, it focuses mainly on lignin recovery and the remaining components of biomass were considered for fermentation. The chemicals such as sulphur dioxide, metal sulphites, and metal bisulphites used for lignin recovery have negative effects on the human health and environment. Moreover, the cellulose fraction was not further converted to any other products such as micro cellulose or nanocellulose, as developed in the present invention.

[0010] Reference may be made to US 2017 / 0159091A1 which recites a fractionation process for producing value-added products from a lignocellulosic biomass by: a) mechanical refining of the lignocellulosic biomass under mild conditions to result in refined biomass pulp with enhanced susceptibility to separation of hemicellulose, cellulose and lignin, and enhanced digestibility of carbohydrates in hydrolysis; b) separating hemicellulose and sulphur-free high- quality lignin from cellulose in the refined biomass, and optionally; c) producing various bioproducts from the above said process. However, the invention was performed with relatively expensive mechanical fractionation of the biomass followed by enzymatic hydrolysis of cellulose fraction to reducing sugars. Furthermore, the sugars were subjected to alcohol fermentation. This approach for the production of second-generation ethanol is being limited by high capital investment for the pre-treatment.

[0011] Various methods of making specialized cellulose and other products from biomass have been reported in WO2019094444A1, wherein a method for microcrystalline cellulose (MCC) production from cellulosic or lignocellulosic biomass by high temperature and pressure extrusion process has been disclosed. The process also generates other cellulosic compounds (nanocellulose), pure lignin, and C5 and C6 sugars. The method includes pretreatment of the biomass, separation of liquid fraction, alkalization for lignin solubilization and separation. However, the invention was limited by its cost intensive extrusion process which operated at high temperature and pressure. Moreover, the wastewater generated from the process was not addressed in the process.

[0012] Reference may be made to WO2008155639A2 that provides a method of separating cellulose, hemicellulose, and lignin from biomass including: a) alkalizing the biomass with a lignindissolving agent under controlled temperature (90-200°C) and high pressure (7.5-20 bar) to dissolve and remove lignin; b) treating the residue from step (a) with mild acid or water at specific temperature and pressure to hydrolyse the hemicellulose and then removing it from the biomass; c) obtaining a highly reactive cellulose from the remaining biomass. However, the reaction conditions mentioned in the developed biomass separation process, alkalization step carried with high temperature and pressure conditions. Further, the process can result in the loss of some cellulose due to breakdown during the treatment. Along with that, the cellulose fraction was not valorised further.

[0013] Reference may be made to WO2012070072 A2, wherein the inventors produced high molecular weight and pure alpha-cellulose. The process started with treating the feedstock with high- pressure steam (18-20 kg / cm2) at a temperature between 190°C to 200°C for a minimum of 2 minutes to dissolve the hemicellulose. The remaining fibrous material was washed with hot water to prepare the pretreated lignocellulosic material. This material was then pulped using sulfite, alkali, and anthraquinone, with a temperature of at least 120°C and a holding time of at least 15 minutes to dissolve the lignin component. The washed and screened pulp was bleached and washed again to yield a pulp containing at least 92% alpha-cellulose, with a high molecular weight, which can be converted into biodegradable derivatives. Nevertheless, the invention only focussed on the alpha cellulose recovery from the lignocellulosic biomass at extreme reaction conditions, wherein the other components were ignored. Moreover, anthraquinone, utilized in cellulose recovery method, inflicts toxicity endangering workers handling it. Moreover, there is a looming apprehension regarding the environmental harm it poses, particularly in terms of water contamination. Implementing anthraquinone in cellulose recovery systems demands specialized machinery and supplementary processing stages, adding to the cost. Since, the anthraquinone interacts with cellulose, the quality and features of the cellulose fibres may be compromised.

[0014] Reference may be made to W02019230803A1 that recites a process for producing a polyphenol composition from bagasse. The process entails the utilization of thermal treatment of bagasse, coupled with diverse alkalis such as sodium hydroxide, potassium hydroxide, and ammonia. The process also involves pH adjustment, filtration, and aromatic synthetic adsorption implemented via styrene-divinylbenzene resin. Nevertheless, the invention only focussed on the extraction of lignin in the form of polyphenols, where hemicellulose and cellulose were not covered. For this reason, the process would not be considered to be effective.

[0015] Reference can be drawn to WO2021097270 Al which discloses a process to produce cellulose, lignocellulosic sugars, lignosulfonate, and ethanol from lignocellulosic biomass. The process encompasses the steps of steaming (125-133°C), pretreatment, chemical recovery, saccharification, and fermenting. Pretreatment was carried out with sulphur dioxide and water, which results in high conversion of glucan to glucose with low enzyme consumption, high recovery of hemicellulose-based monomeric sugars, a high yield of ligno sulfonate, with no lignin precipitates which eventually enabled in efficient production of ethanol through fermentation. Nevertheless, the invention involved a relatively costly mechanical separation of biomass, followed by enzymatic breakdown of the cellulose fraction into reducing sugars. Additionally, these sugars underwent fermentation with alcohol. In general, the process of producing second-generation ethanol is constrained by the substantial initial investment required for the pretreatment stage. On the other hand, sulphur dioxide and metal sulphites / bisulphites have drawbacks and negative effects on human health and ecosystems.

[0016] After a review of the relevant prior art in the field it may be summarized that there is a growing interest in the biorefining of surplus agricultural waste biomass in order to produce a variety of bio-based products, which can offer a sustainable opportunity for the growth of the bioeconomy.

[0017] Distinctive to the prior art findings, the present invention aims at an affordable, integrated, biorefining process for recovering commercially viable chemicals / products from agro-waste, namely mono-saccharomate syrup, poly-phenolic precursor, and cellulosic derivatives such as (R)-cellulose, (p)-cellulose and (n)-cellulose, wherein the process is a zero liquid discharge process involving sequential recovery strategy to valorise all the components of biomass without affecting their quality while reusing the consumed water by photosynthetic polishing with minimal impact on the environment.

[0018] OBJECTIVES OF THE INVENTION The main objective of the present invention is therefore to provide an integrated closed loop biorefining process for sustainable multi-product valorisation with zero liquid discharge.

[0019] Another objective of the present invention is to utilize the excessively available crop residue (excess) biomass namely, sugarcane bagasse, rice straw, wheat straw, and cotton stalks as the primary feedstock so as to valorise them into commercially important chemicals mainly, cellulosic derivatives, poly-phenols, and mono-saccharomate syrup, nutrient rich biomass.

[0020] Still another objective of the present invention is to provide a process that uses / treats water in an integrated manner resulting in Zero liquid discharge (ZLD).

[0021] Yet another objective of the present invention is to provide a process that focuses on the sequential recovery strategy to valorise all the components of biomass without affecting their quality, while reusing the consumed water by photosynthetic polishing with minimal impact on the environment.

[0022] Still another objective of the present invention is to provide a process wherein the biomass is comminuted to fragments of size less than 400 microns.

[0023] Yet another objective of the present invention is to provide a process comprising alkaline- oxidative physico-chemical catalysis step for polyphenols recovery, such that the cellulosic products are obtained without any impurities.

[0024] Still another objective of the present invention is to provide a process wherein the carbon rich wastewater streams are treated with photosynthetic polishing for simultaneous production of biomass / soil conditioner.

[0025] SUMMARY OF THE INVENTION

[0026] The present invention provides a sustainable three stage process for sequential recovery of mono-saccharomate syrup (C5 and C6 sugars), poly-phenolic precursors, cellulosic products [(R)-cellulose / (p)-cellulose / (n)-cellulose], by employing sequential mild acid-alkali treatment, and depolymerisation, respectively. Further, the invention provides for the treatment of wastewater streams through photosynthetic polishing strategy to enable zero liquid discharge (ZLD) as integrated part of biorefinery (Fig. 1). In an embodiment, the invented process encompassing a biorefining platform was designed in closed loop format comprising the steps as depicted below:

[0027] 1. The said excess croup residues (biomass) was comminuted and made to fragments of size less than 400 microns;

[0028] 2. The obtained biomass fragments were processed for C5 separation with hydro-catalysed physical treatment;

[0029] 3. The resulting hydrolysate from the hydro -catalysed physical treatment was concentrated to obtain mono-saccharomate syrup;

[0030] 4. Later, the pretreated residual biomass was subjected to alkaline-oxidative physico-chemical catalysis for polyphenols recovery in the form of hydrolysate;

[0031] 5. Further, acid soluble phenolic impurities from the residue were eliminated by mild acid treatment;

[0032] 6. Thereafter, the treated cellulosic residue was processed for blanching to remove colour which further yielded a (R)-cellulosic pulp;

[0033] 7. Subsequently, the (R)-cellulose pulp was subjected to partial depolymerization using active oxygenated compound to result in (p)-cellulosic suspension;

[0034] 8. Alternatively, the blanched (R)-cellulosic pulp was processed for intense depolymerization using intensive acid hydrolysis;

[0035] 9. After the acid hydrolysis, the neutralized suspension was echo -graphic ally treated for homogenization to result in (n)-cellulose;

[0036] 10. The cellulosic derivatives were dried and powdered by employing spray dryer to result in (R)-cellulose or (p)-cellulose or (n)-cellulose depending on the product of interest;

[0037] 11. The carbon rich waste streams were treated with photo-polishing with simultaneous production of soil conditioner;

[0038] 12. The treated water can be used in pretreatment steps for dilution purpose.

[0039] In another embodiment, the present invention provides an integrated closed-loop biorefining process for sustainable multi-product valorization with zero liquid discharge, comprising the steps of:

[0040] (i) comminuting lignocellulosic waste biomass into fragments capable of passing through a mesh size of 400 microns;

[0041] (ii) subjecting the comminuted lignocellulosic biomass obtained in step (i) to hydrocatalyzed physical treatment at a temperature in the range of 80 to 130 degree C and a gauge pressure of 0.5 to 2.7 bar for a period of 15 to 90 minutes to recover a monosaccharomate solution as hydrolysate and residual lignocellulosic biomass;

[0042] (iii) filtering the hydrolysate obtained in step (ii) and concentrating it to form a monosaccharomate syrup;

[0043] (iv) treating the residual lignocellulosic biomass obtained in step (ii) with 5-15% KOH in H2O2 (w / v) at a temperature ranging from 80 to 130 degree C and a pressure of 0.5 to 2.7 bar for 15 to 60 minutes to recover polyphenols as hydrolysate;

[0044] (v) subjecting the hydrolysate obtained in step (iv) to density separation and acidifying the liquid portion with 25 to 35% HC1 to precipitate aromatic phenolic precursors;

[0045] (vi) treating the residual lignocellulosic biomass obtained in step (iv) with 2±0.5% H3PO4 at a temperature of 60+5 °C for 2 hours to remove acid- soluble phenolic impurities;

[0046] (vii) bleaching the residual biomass obtained in step (vi) with 5 to 10% H2O2 at a temperature in the range of 45 to 55 degree C for 2 hours to obtain bleached (R)-cellulosic suspension;

[0047] (viii) filtering the bleached (R)-cellulosic suspension obtained in step (vii) and spray drying to produce white-coloured (R)-cellulose powder;

[0048] (ix) optionally bleaching and depolymerizing the lignocellulosic biomass obtained in step (vii) using 20 to 40% H2O2 (v / v) at a temperature in the range of 45 to 55 degree C for 2 hours at a pH of 11.0 to 11.5 to produce (p)-cellulose suspension;

[0049] (x) neutralizing and filtering the cellulose suspension obtained in step (ix) and spray drying to produce white- coloured (p)-cellulose powder;

[0050] (xi) depolymerizing the (R)-cellulose powder obtained in step (viii) using 40 to 60% H3PO4 / HCI at a temperature of 40±2°C for 2 hours, followed by neutralization and density separation, resulting in (n)-cellulosic suspension;

[0051] (xii) echo-graphically treating the neutralized suspension obtained in step (xii) for homogenization to produce (n)-cellulose, and filtering the suspension followed by spray drying to produce white-colored fine (n)-cellulose powder;

[0052] (xiii) combining the waste streams of the process and subjecting them to photosynthetic treatment in a mixotrophic cultivation mode to treat the waste process water and produce nutrient-rich biomass; (xiv) separating and recycling the treated water obtained in step (xiii) for use in the washing and filtration unit operations of the above process.

[0053] In still another embodiment, the present invention provides an integrated closed-loop biorefining process, wherein the invention utilizes circular chemistry principles via a cost- effective biorefinery module to convert lignocellulosic biomass into products such as (R)- cellulose, (p)-cellulose, (n)-cellulose, mono-saccharomate syrup, and a poly-phenolic precursor with minimal chemical input.

[0054] In yet another embodiment, the present invention provides an integrated closed-loop biorefining process wherein the process emphasizes qualitative and quantitative recovery of products applicable in various industrial sectors, demonstrating versatility across diverse biomass sources and employing a closed-loop system with net- zero liquid discharge to enhance resource efficiency and minimize emissions.

[0055] BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Fig. 1 : Schematic illustration of the invented process depicting the unit operation (Numerical in Roman) and the products of biorefinery process (Pl-7).

[0057] DETAILS OF BIOLOGICAL RESOURCES USED IN THE INVENTION

[0058] DETAILED DESCRIPTION OF THE INVENTION

[0059] The present invention aims to utilize the excessively available crop residue (excess) biomass namely, sugarcane bagasse, rice straw, wheat straw, and cotton stalks as the primary feedstock to valorise into commercially chemicals mainly, cellulosic derivatives, poly-phenols, and mono-saccharomate syrup, nutrient rich biomass, and treated water in an integrated biorefinery with Zero liquid discharge (ZLD) approach. The invention is focused on the sequential recovery strategy to valorise all the components of biomass without affecting their quality and reusing the consumed water by photosynthetic polishing with minimal impact on the environment.

[0060] In an aspect, the present invention provides an integrated, affordable biorefining process for the production of multiple products, namely mono-saccharomate syrup, poly-phenolic precursor, and cellulosic derivatives such as (R)-cellulose, (p)-cellulose and (n)-cellulose from the surplus / waste crop residues. The process involves C5-separation, solid-liquid separation, poly-phenol extraction, blanching, density separation, depolymerization, and spray drying. Additionally, the streams generated from each stage of the biorefinery were used for value addition by integrating with photosynthetic resource recovery strategy. The extraction and treatment approaches vary with the composition and type of the feedstock biomass. The resulting products, subsequently can be used for their respective commercial applications.

[0061] The lignocellulosic biorefinery process is a promising approach for the sustainable recovery of components such as cellulose, lignin, hemicellulose, silica, etc. The process of the present invention starts with saccharomate recovery through pretreatment of the biomass to break down the lignocellulosic structure. Subsequently, the biomass is subjected to alkali catalysed pretreatment to recover the lignin as polyphenolic precursor. Further, the cellulose was separated and three different methodologies were followed to produce (R)-cellulose, (p)- cellulose and (n)-cellulose. The process operates in a closed-loop mode, where the water used in the process is treated in photosynthetic route, recovered and reused, leading to a significant reduction in water consumption and waste generation. In a zero liquid discharge mode, this process leverages the conversion of Agri-waste (lignocellulosic) biomass into valuable products without generating waste streams. This approach not only reduces the environmental impact of the process but also makes it economically viable. The process supports the concept of ‘Chemurgy ’ that deals with the study of the industrial use of agricultural products as raw materials in the production of chemicals, fuels, and other products to create a more sustainable and circular economy by utilizing waste products and reducing the reliance on non-renewable resources. Semisynthetic chemicals, produced from natural components, are a necessary step towards promoting sustainability and circularity in the chemical industry.

[0062] All the steps of the developed process operate in the temperature range of 80 to 130 degree C, at 1 to 2 bar pressure. However, the photosynthetic polishing is effective at ambient conditions (25-35°C; 1 bar).

[0063] The detailed characterisation of the biorefinery products monosaccharomate syrup, poly phenolic precursor, (R)-cellulose, (p)-cellulose, (n)-cellulose, treated water, photosynthetic biomass is depicted in Tables 1-3).

[0064] Table 1: Compositional analysis of selected Agri-waste feedstocks

[0065] Table 2: Characteristics of water streams

[0066] Table 3: Composition of biomass from photosynthetic polishing

[0067] NEW RESULT(S) ACHIEVED DUE TO THE INVENTIVE STEPS ADOPTED

[0068] • Comminution of the Agri-waste biomass to fragments of size less than 400 p facilitates in relatively low chemical consumption.

[0069] • The alkaline-oxidative physico-chemical catalysis step for polyphenols recovery is an effective strategy so that the cellulosic products can be obtained without any impurities.

[0070] • The carbon rich wastewater streams from the process are treated with photosynthetic polishing for simultaneous production of biomass / soil conditioner.

[0071] • The conversion of (n)-cellulose from the blanched (R)-cellulose through intense depolymerization using acid hydrolysis, neutralization and echo-graphic treatment is an innovative approach.

[0072] Specifications of Cellulosic derivatives

[0073] The Fourier Transform Infrared (FTIR) spectrum of (R)-cellulose, (p)-cellulose, and (n)- cellulose samples shows different spectroscopic absorbance peaks in the frequency domains of 3425-3310 cm-1 and 2900-2850 cm-1, which correspond to the oscillation of alcoholic functional groups and aliphatic C-H groups, respectively. Bending vibrations of -OH (alcoholic) water, in-plane bending of C-H bonds, and vibrational signatures associated with the glucose ring and auxiliary groups, comprising of C-C, C-OH, and C-H vibrations, were attributed to absorbance maxima observed near 1640 cm-1, 1380 cm-1, and 1050 cm-1, respectively. Additionally, distinctive peaks at 1160 cm-1 and 895 cm-1 were attributed to the ether linkage and glycosidic bond stretching, respectively. A band occurring near 1435 cm-1, known as the "crystallinity band," indicated the existence of more crystalline domains within (p)-cellulose and (n)-cellulose due to the asymmetric bending of the methylene moiety. The X-ray diffraction (XRD) analysis of the samples showed the presence of distinctive peaks at 15°, 18°, 22° (regarded as the crystallinity peak), and 35° of 29 values, as observed in the X- ray diffractograms. All the samples exhibited four specific crystalline planes (101, 101, 002, and 040). The percentage crystallinity of (R)-cellulose, (p)-cellulose, and (n)-cellulose was determined from the XRD plots as 76%, 85%, and 89%, respectively. The increase in crystallinity of (p)-cellulose and (n)-cellulose samples was associated with a corresponding decrease in amorphous domains caused by depolymerization or the breakage of glycosidic linkages in the cellulosic polymer chain.

[0074] The characteristic heterogeneity of cellulosic materials in terms of their shapes and sizes was evident from the field emission scanning electron microscopic (FE-SEM) images of (R)- cellulose, (p)-cellulose, and (n)-cellulose samples. The SEM images showed that the (p)- cellulose and (n)-cellulose particles were considerably smaller in size than the (R)-cellulose particles. The fibers in the (R)-cellulose sample were larger, typically greater than 20 microns, and were visible at lower magnifications. In contrast, the smaller size and mostly crystalline nature of (p)-cellulose and (n)-cellulose particles required higher magnifications to be observed. The FE-SEM images revealed a distinct difference in morphology among the three samples.

[0075] TGA revealed variations in weight loss and degradation with increasing temperature. A gradual weight loss starting at 60°C was attributed to the surface-bound moisture, with intermolecularly hydrogen-bonded water eliminated near 110-120°C. The cellulose degraded at 260°C, with maximum decline occurring at 360°C, comprising roughly 80% of the overall degradation. For (n)-cellulose, the maximum weight loss was detected between 250°C and 350°C, accounting for approximately 80% of its degradation. The observed lower thermal stability in (p)-cellulose and (n)-cellulose may be due to particle size degradation, heterogeneity of particles, the presence of free ends in cellulose chains, and reduction in molecular weight through depolymerization and elimination of amorphous domains during acid hydrolysis. Therefore, TGA results demonstrate disparate thermal stability among the samples.

[0076] Specifications of polyphenolic precursor FTIR was used to identify functional groups in a polyphenolic precursor extract. Various absorption patterns at different wave numbers were detected, including a carbonyl stretch vibrations of aromatic alcohol, aromatic skeletal vibrations, syringyl and guaiacyl ring vibrations, and primary alcohol vibrations. These peaks (at 1600, 1510, 1325-1330, and 1030 cm1) indicated the sample's quality. Unlike cellulose samples, the polyphenolic precursor showed more peaks in the range of 1600-1000 cm1. This suggests that the precursor is structurally complex and contains methoxylated derivatives of benzene, like phenylpropanoid alcohols, as well as the structural units coniferyl, sinapyl, and coumaryl alcohols.

[0077] The UV-Vis spectrum of the polyphenolic precursor sample revealed specific absorption in the range of 200-400 nm. Deconvolution of the spectrum showed characteristic peaks at 218 nm (from conjugated double bonds of aromatic rings), 247 nm (from Free -OH groups), 290 nm (from the phenolic group), 325 nm (from conjugated double bond and carbonyl groups in phenolic rings), and 356 nm (from dissociated aromatic carboxylic acids, conjugated double bonds of phenols, and carbonyl groups). The third peak (285-295 nm) indicated a larger number of syringyl units in the skeleton.

[0078] The TGA graphs showed weight loss as a function of temperature due to the complex chemical structure of the sample, which contains mainly aromatic rings with various bonds and branching. The sample had a wide degradation temperature range, from 100-800°C, with 20- 25% remaining undegraded even at 600°C due to the presence of highly condensed aromatic groups. TGA revealed three degradation patterns: initial weight loss from 50-120°C due to water evaporation, further weight loss from 200-300°C likely due to phenolic ring breakdown, and gradual degradation from 310-600°C involving different phenolic groups, aromatic alcohols, and aldehydes. DTG ax was observed in the range of 240-280°C. Scanning electron microscopic (SEM) image of poly phenolic precursor depicted that the particles are diverse and minute, ranging from 50 to 200 nm, exhibiting a porous composition.

[0079] Specifications of Monosaccharomate Syrup

[0080] High performance liquid chromatography (HPLC) of the recovered monosaccharomate syrup. The chromatogram clearly depicted the presence of reducing sugars namely Glucose at retention time 12.722 min and Xylose at retention time 13.560 min with 1.5 g / L (84% recovery) and 12 g / L (95% recovery) concentrations, respectively. EXAMPLES

[0081] The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention in any manner.

[0082] Example 1: Biorefining process using Sugarcane Bagasse

[0083] The collected Sugarcane Bagasse (SCB) was sorted and dried in sunlight. The dried SCB was fragmented into small pieces, powdered and the portion passing through 400 p size mesh was separated and selected as raw material for the biorefinery. The chemicals such as phosphoric acid, hydrochloric acid, potassium hydroxide, and hydrogen peroxide were technical grade. The cellulose extraction method from SCB was performed by selective and sequential removal of hemicellulose and lignin fractions. The ground SCB was added with water in 1 : 12 ratio (w:v) and physically treated in an closed reactor 8O-13O°C for about 15-90 minutes to separate the C5 fraction as hydrolysate(Table 4). The resulting slurry was subjected to filtration. Further, the residue from filtration was added with 5% and 10% KOH and treated at 8O-13O°C for 15- 90 minutes to recover the poly-phenolic content. Subsequent filtration, the residual biomass is treated with 1.5% H3PO4 at 55°C for 2 hours to get rid of impurities (Table 5).

[0084] The resulting liquor was added with 10 folds of the distilled water to cease the reaction. Thereafter, neutralization of the post-filtration residue was achieved with deionized water. Then the delignified pulp was added with 5% H2O2 at treated at 55°C for 2 hours and the resulting suspension was filtered, appeared as a white and pulpy lump [(R)-cellulose] which was further used for (p)-cellulose / (n)-cellulose preparation. The resulted(R)-Cellulose was subjected for oven drying for overnight at a temperature of 60°C and ground to powder and subsequently subjected for depolymerization in presence of 20-40% H2O2 at 50°C in alkaline medium (pH 11.5+0.1) for 1 hour to result in formation of (p)-cellulose suspension. The suspension was washed five times with water and filtered. The (p)-cellulose was added with deionized water and spray dried to get a white crystalline powder. Whereas, (n)-Cellulose preparation from the extracted (R)-cellulose was carried by intense acid-hydrolysis by adding with 40-60% of Phosphoric acid (1: 10 w / v) dropwise by keeping the set up in ice bath. Further, it was hydrolysed under continuous stirring at 45°C for 2 hours. Thereafter, chilled de-ionized water, ten times the volume of the reaction solution was added to stop the reaction. The resulting suspension was centrifuged, and the solid residue was neutralized with diluted NaOH. Then the resulted suspension was added with 5% H2O2 for final bleaching and eco-graphically treated in pulse mode of 10 seconds for 2hours in the ice bath (Table 6).

[0085] Subsequently, the suspension was dialyzed against distilled water to remove excess acid was spray dried to get (n)-cellulose powder. The liquid stream from first step rich in reducing sugars was subjected for solvent extraction to get mono-saccharomate syrup. Whereas the hydrolysate from the alkali treatment give rise to poly -phenolic precursor which was further precipitated at pH 2 by adding cone. HC1. The wastewater streams other than mono-saccharomate syrup, were combined and the composite stream was subjected to photosynthetic polishing to generate nutrient rich biomass, which can be used as the soil conditioner / biofertilizer. After tertiary treatment / polishing, the treated water is looped into the process chain for dilution at various pretreatment steps.

[0086] Table 4: Monosaccharomate syrup recovery (%) from Sugarcane Bagasse Biorefinery

[0087] Table 5: Poly-phenolic precursor recovery (%) from Sugarcane Bagasse Biorefinery

[0088] Table 6: Depolymerization of Sugarcane Bagasse Biorefinery

[0089] Example 2: Biorefining process using Rice Straw

[0090] Rice Straw (RS) was collected from local paddy field and the straw was sorted and dried in sunlight. The dried RS was chopped into small pieces (2-3 cm), powdered and the portion passing through a mesh (400pm size) was separated and was used as raw material for the study. The adopted biorefining methodology is like the SCB, however it is adequately modified according to the rice straw biomass composition. Firstly, the powdered RS was added with water in a 1: 10 (solid to liquid) ratio (Table 7-9). The suspension was agitated well for uniform mixing and then, the suspension was treated in a sealed reactor for 15-90 minutes at 8O-13O°C. The resulted solution was cooled to room temperature and filtered to remove of maximum C5- rich saccharomate from RS biomass as filtrate. Further, the residue was processed for polyphenol recovery and silica removal by treating the solid residual with IN and 2 N KOH at 80- 130°C for 15-90 minutes in closed reactor. The reaction mixture was filtered, and the dark brown coloured filtrate was used for poly -phenol recovery and the resulted solid was washed thoroughly with water and filtered. Then the solid residue was subjected to acid treatment (2% H3PO4 at 60°C for 2 hours) to remove any impurities. After successive recovery of mono- saccharomate syrup, phenolic precursor, and silica from RS, cellulosic fraction has remained as a creamy solid residue. Further blanching of the cellulosic fraction with 5% H2O2 at 50°C for 2 h facilitated in colour removal. The blanched (R)-cellulose was subsequently subjected for partial depolymerization in presence of 20-40% H2O2 (pH-10) at 45°C for a reaction time of 2 h to result in (p)-cellulose suspension and the suspension was washed several times with water and filtered. The (p)- cellulose was added with deionized water and spray dried to get a white crystalline powder. In another way, (n)-cellulose preparation from the extracted (R)-cellulose was enabled by intense acid-hydrolysis by adding with 40-60% of hydrochloric acid (1: 10 w / v) dropwise by keeping the set up in ice bath. Further, it was hydrolysed under continuous stirring at 40°C for 2 hours. Thereafter, chilled de-ionized water, ten times the volume of the reaction solution was added to stop the reaction. The resulting suspension was centrifuged, and the solid residue was neutralized with 0.1 N KOH. Then the resulted suspension was added with 5% H2O2 for final bleaching and eco-graphically treated in pulse mode of 15 seconds for 1.5 hours in the ice bath. Subsequently, the suspension was dialyzed against distilled water to remove excess acid was spray dried to get (n)-cellulose powder. Lignin precipitation and wastewater stream valorisation through algal polishing was performed in similar way, as discussed in Example.1.

[0091] Table 7: Monosaccharomate syrup recovery (%) from Rice straw Biorefinery

[0092] Table 8: Poly-phenolic precursor recovery (%) from Rice straw Biorefinery

[0093] Table 9: Depolymerization of Rice straw Biorefinery

[0094] Example 3: Biorefining process using Wheat Straw

[0095] Wheat straw / stubble (WS) burning is a relatively recent problem with the use of new mechanized harvesting techniques that make WS unsuitable for its regular use cattle feed. Owing to its rich cellulose content WS, was considered for the biorefining approach (Table 10- 12). WS after collection was washed with water for the removal of soil and dirt followed by oven drying. The dried WS was cut into pieces and shredded into powder (less than 400 micron). In the first step, the processed WS powder added with water in closed reactor for 15- 90 minutes at 8O-13O°C for solubilization and recovery of saccharomate content from the biomass. The resulted residue was washed using distilled water until neutral pH attained and then filtered, the solid residue was dried for 18 h at 50°C in hot air oven.

[0096] The residual biomass was further subjected to poly-phenol removal process by treating with 5- 10% KOH at 8O-13O°C for 15-90 minutes in a sealed container. The resulted hydrolysate was processed for phenolic recovery. The left-over residue was washed using distilled water to neutralized (pH-7). The solid portion, after filtration is treated with 2.5% H3PO4 at 65°C for 2 hours for the removal of acid soluble phenolic impurities. The reaction mixture was filtered and the residual (cellulosic) biomass was subjected for colour removal, and then dried to obtain (R)-cellulose powder. Further the (R)-cellulose was fragmentarily depolymerized with 20-30% H2O2 (at pH 10-11) for 1.5 hour at 55°C. Then reaction mixture was passed through a filter to get (p)-cellulosic residue, which was further washed thoroughly and filtered, then the resulted white pulp was spray dried to (p)-cellulose powder, (n)-cellulose recovery from (R)-cellulose was carried in the methodology as mentioned in Example. 2. Whereas the lignin precipitation and wastewater stream valorisation through algal polishing was performed in similar way, as discussed in Example.1.

[0097] Table 10: Monosaccharomate syrup recovery (%) from Wheat straw Biorefinery

[0098] Table 11: Poly-phenolic precursor recovery (%) from Wheat straw Biorefinery Table 12: Depolymerization of Wheat straw Biorefinery

[0099] Example 4: Biorefining process using Cotton Stalks

[0100] Cotton stalks (CS) was collected from a harvested cotton field and the stalks were sorted and dried in sunlight. The dried CS was chopped into small pieces (2-3 cm), powdered and the pulverised fraction that passed through a 400 pm pore sized mesh. The powdered CS was subjected to organosolv extraction [methanol-toluene, 1 :2 (v / v)], at a temperature of 60°C for 4 h to remove coloured organics, and this biomass was considered as the feedstock for the biorefining study. The adopted biorefining methodology is like the previous examples, however it is adequately modified according to the CS biomass composition (Table 13-15). Firstly, the processed CS was added with water in a 1:15 (solid to liquid) ratio. The suspension was agitated well for uniform mixing and then, then subjected to hydro -treatment in a closed reactor for 15-90 minutes at 8O-13O°C. The resulted solution was fdtered to remove of maximum C5 rich saccharomate from CS biomass in the filtrate. Subsequently, the residue was processed for poly-phenol recovery, when subjected with 5-7.5% KOH at 8O-13O°C for 15-90 minutes in closed reactor. Then the filtrate was used for poly-phenol recovery and the resulted solid was washed thoroughly with water and filtered. The solid fraction, from the filtration operation was added with 2.5% H3PO4 at 55°C for 2 hours for eliminating the acid soluble phenolic impurities. The remained cellulosic residue was subsequently blanched by adding 5% H2O2 at 50°C for 2 h and the colour of the (R)-cellulose was removed. The blanched (R)- cellulose, further treated for partial depolymerization in presence of 20-40% H2O2 (pH-11) at 50°C for a reaction time of 1 h to yield (p)-cellulosic suspension, which was washed 5 times with water and then filtered. The (p)-cellulose was added with deionized water and spray dried to get a white crystalline powder (Table 16). (n)-cellulose recovery from (R)-cellulose was carried in the methodology as mentioned in Example. 1. Moreover, the lignin precipitation and wastewater stream valorisation through algal polishing was performed in similar way, as discussed in Example 1.

[0101] Table 13: Monosaccharomate syrup recovery (%) from Cotton stalks Biorefinery

[0102] Table 14: Poly-phenolic precursor recovery (%) from Cotton stalks Biorefinery

[0103] Table 15: Depolymerization of Cotton stalks Biorefinery

[0104] Table 16: Physical properties of (p)-cellulose samples

[0105] ADVANTAGES OF THE INVENTION

[0106] • Keeping in line with the principles of circular chemistry, this invention explores a biorefining approach to convert lignocellulosic biomass into multiple versatile products, including (R) -cellulose, (p)-cellulose and (n)-cellulose, mono-saccharomate syrup, and a poly-phenolic precursor with zero liquid discharge approach.

[0107] • Low cost biorefinery module with multiple products,

[0108] • Low chemical inputs and low environmental impacts • Qualitative and quantitative recovery of the biorefinery products

[0109] • The developed process can be applicable to various kinds of lignocellulosic biomass

[0110] • Closed loop process with Net Zero Liquid discharge approach with limited emissions

[0111] • Optimal recovery of the lignocellulosic components and production of pharmaceutically value-added chemicals

Claims

We claim:

1. An integrated closed-loop biorefining process for sustainable multi -product valorization with zero liquid discharge, comprising the steps of:(i) comminuting a lignocellulosic waste biomass into fragments capable of passing through a mesh size of 400 microns;(ii) subjecting the comminuted lignocellulosic biomass obtained in step (i) to hydrocatalyzed physical treatment at a temperature in the range of 80 to 130°C and a gauge pressure of 0.5 to 2.7 bar for a period of 15 to 90 minutes to recover a monosaccharomate solution as hydrolysate and a residual lignocellulosic biomass;(iii) filtering the hydrolysate obtained in step (ii) and concentrating it to form a monosaccharomate syrup;(iv) treating the residual lignocellulosic biomass obtained in step (ii) with 5-15% KOH in H2O2 (w / v) at a temperature ranging from 80 to 130°C and a pressure of 0.5 to 2.7 bar for 15 to 60 minutes to recover a polyphenols as hydrolysate;(v) subjecting the hydrolysate obtained in step (iv) to density separation and acidifying the liquid portion with 25 to 35% HC1 to precipitate aromatic phenolic precursors;(vi) treating the residual lignocellulosic biomass obtained in step (iv) with 2+0.5% H3PO4 at a temperature of 60±5°C for 2 hours to remove acid-soluble phenolic impurities;(vii) bleaching the residual biomass obtained in step (vi) with 5 to 10% H2O2 at a temperature in the range of 45 to 55 degree C for 2 hours to obtain a bleached (R)- cellulosic suspension;(viii) filtering the bleached (R) -cellulosic suspension obtained in step (vii) followed by spray drying to produce a white-coloured (R)-cellulose powder;(ix) optionally bleaching and depolymerizing the lignocellulosic biomass obtained in step (vii) using 20 to 40% H2O2 (v / v) at a temperature in the range of 45 to 55 degree C for 2 hours at a pH of 11.0 to 11.5 to produce a (p)-cellulose suspension;(x) neutralizing and filtering the cellulose suspension obtained in step (ix) and spray drying to produce a white-coloured (p)-cellulose powder;(xi) depolymerizing the (R)-cellulose powder obtained in step (viii) using 40 to 60% H3PO4 / HCI at a temperature of 40±2°C for 2 hours, followed by neutralization and density separation, resulting in a (n)-cellulosic suspension;(xii) echo-graphically treating the neutralized suspension obtained in step (xii) for homogenization to produce (n)-cellulose, and filtering the suspension followed by spray drying to produce a white-colored fine (n)-cellulose powder;(xiii) combining the waste streams of the process and subjecting them to photosynthetic treatment in a mixotrophic cultivation mode to treat the waste process water and produce a nutrient-rich biomass;(xiv) separating and recycling the treated water obtained in step (xiii) for use in the washing and filtration unit operations of the above process.

2. The process as claimed in claim 1 , wherein the process utilizes circular chemistry principles via a cost-effective biorefinery module to convert lignocellulosic biomass into products such as (R)-cellulose, (p)-cellulose, (n)-cellulose, mono-saccharomate syrup, and a polyphenolic precursor with minimal chemical input.

3. The process as claimed in claim 1, wherein the process emphasizes qualitative and quantitative recovery of products applicable in various industrial sectors, demonstrating versatility across diverse biomass sources and employing a closed-loop system with net- zero liquid discharge to enhance resource efficiency and minimize emissions.

Images