FIELD OF THE INVENTION

The present invention relates to the area of production of a variety of valuable products from biomass. In particular, the present invention relates to production of cellulose, silica, lignin, ethanol and cattle feed from bio mass.

BACKGROUND OF THE INVENTION

Biomass including forest, agricultural waste, crop residues, yard choppings, wood chips, etc. remains a significant renewable source. Biomass derived from plant materials are known to comprise cellulose, hemi-cellulose, lignin and extractives (which comprises significant quantity of silica). Lignin, hemicellulose, cellulose and extractives form unique and complex structures (referred to as natural polymer) in biomass. Depending upon the source of the biomass, the amount of cellulose, hemi-cellulose, lignin and extractives varies. Also, depending upon the source, the nature of the natural polymer varies.

Varied ingredients of the biomass can be used for preparing value added products. For instance, hemicelluloses are used for ethanol or xylitol production. Lignin is used for producing carbon fibers or can be used as fuels (calorific value of 5500 kcal/kg). Cellulose is used in pharmaceuticals and the papermaking industry. Silica can be directly used in variety of industrial processes. However, to produce value-added products, biomass’ components should be separated.

Rice stubble, rice straw, wheat straw and cotton stock are agricultural residues rich in lignocellulosic material. However, the aforesaid types of biomass are troublesome biomass for an industrial application because of its high silica/lignin content and the wax-like substances covering the surface. The surplus availability of these types of biomass, its limited usage and environment pollution caused by inefficient burning has fostered research for its valorization to biofuels. Most bio mass is used for landfill or is burned, but this leads to methane gas production or air pollution. Separating the biomass’ components is a complicated procedure and a variety of processes are reported, depending upon the nature of the biomass and the nature of the product which is intended to be recovered as the final product.

In most cases, one or two products are taken into consideration for recovery from the biomass and, the separation process is optimized accordingly. Such a practice is followed for simple reasons that while extracting certain components from the biomass, some of the other components present in the biomass undergo degradation. Thus, recovery of a variety of value added products from biomass is a tricky proposition.

Reference may be made to “Effects of a steam explosion pretreatment on sugar production by enzymatic hydrolysis and structural properties of reed straw” by Qiulong Hu et al., Biosci. Biotechnol. Biochem., 77 (11), 2181-2187, 2013. As per Qiulong Hu et al., enzymatic hydrolysis is an important step in the production of ethanol. However, due to presence of lignin, hemicelluloses, and celluloses, the efficiency of enzymatic hydrolysis is low. The document recognizes need of pretreatment for disrupting the hydrogen bonds in crystalline cellulose and the covalent cross-linkages in the lignin structure for increasing the efficiency of enzymatic hydrolysis. The document mentions that principal methods for pretreatment include (a) hydrothermal processing, (b) steam explosion, (c) acid and alkali treatment, (d) radiation, (e) ammonia treatment, and (f) ionic liquid treatment. The document however is purely directed towards increasing the production of ethanol and is not directed towards production of three or more valuable products from biomass. This can be inferred from the process which is followed and which includes recovering the steam exploded biomass, drying the same at 80°C for 24 hours in a constant temperature oven, reducing the size of the bio-mass and performing enzymatic hydrolysis on the size-reduced biomass.

Reference may be made to “Effectiveness of Lignin-Removal in Simultaneous Saccharification and Fermentation for Ethanol Production from Napiergrass, Rice Straw, Silvergrass, and Bamboo with Different Lignin-Contents” by Masahide Yasuda et al. http://dx.doi.org/10.5772/54194. As per Masahide Yasuda et al., teaches a process for producing ethanol from Napiergrass, Rice Straw, Silvergrass, and Bamboo which includes alkali pretreatment followed by Simultaneous Saccharification and Fermentation. Once again this document is purely directed towards increasing the production of ethanol and is not directed towards production of three or more valuable products from biomass.

Reference may be made to Indian Patent Application No. 201821024153 which discloses a process for pre-treating lignocellulosic biomass to hydrolysable polysaccharide enriched biomass comprising steps of: a) providing a feedstock comprising cellulosic biomass; b) chopping of cellulosic biomass using knife-mill to have a cellulosic biomass feed material of size in the range of 1 mm to 40 mm; c) feeding of feed material obtained from the preceding step b) in to a horizontal counter current extraction unit through one end; d) removing excess of water from the feed material obtained from the preceding step c); e) soaking the feed material obtained from the preceding step d); f) optionally removing excess of water from the feed material obtained from preceding step e); g) steam pre-treating the feed material obtained from the preceding step f); h) neutralizing the slurry obtained from the preceding step g); and i) optionally saccharifying the neutralized slurry obtained from the preceding step h). Once again this document is purely directed towards increasing the production of ethanol and is not directed towards production of three or more valuable products from biomass.

Reference may be made to “Comparison of alkaline pulping with steam explosion for glucose production from rice straw” by Maha M. Ibrahim et al., Carbohydrate Polymers 83 (2011) 720-726, which discloses utilization of rice straw as a lignocellulosic biomass feedstock to produce a value-added product. As per the document, different pretreatment methods, such as chemical pretreatment process using alkaline pulping and steam explosion were applied to pretreat the lignocellulosic biomass. A Spezyme CP® cellulase enzyme was used to hydrolyze the pretreated material into glucose, which can be further fermented to produce ethanol. Once again this document is purely directed towards increasing the production of ethanol and is not directed towards production of three or more valuable products from biomass.

Reference may be made to “Rice straw as a feedstock for biofuels: Availability, recalcitrance and chemical properties” by Alok Satlewal et al. Alok Satlewal et al., summarizes the current pre-treatment trends for obtaining ethanol from rice straw. Once again this document is purely directed towards increasing the production of ethanol and is not directed towards production of three or more valuable products from biomass.

Reference may be made to “Environmentally Friendly Method for the Separation of Cellulose from Steam-Exploded Rice Straw and Its High-Value Applications” by Guangjun Gou et al. in http://dx.doi.org/10.5772/intechopen.79014. Guangjun Gou et al. discloses separation of cellulose from agricultural straw pretreated with steam explosion, which include delignification with recyclable water-polar aprotic organic solvent, selective biodegradation of the lignin component, and extraction of cellulose with imidazolium-based ionic liquids from the steam-exploded rice straw. Once again this document is purely directed towards producing Cellulose and is not directed towards production of three or more valuable products from biomass.

Reference may be made to US 20140170713 which discloses a process for fractionating lignocellulosic biomass, said process comprising: (a) providing a feedstock comprising lignocellulosic biomass; (b) extracting hemicelluloses from said feedstock in the presence of steam or hot water, and optionally a first hydrolysis catalyst, thereby generating a first solids stream and a first liquid stream; (c) contacting said first solids stream with an acid or acid precursor, water, and a solvent for lignin, to produce a second liquid stream containing cellulose-rich solids and lignin; (d) recovering said cellulose -rich solids from said second liquid stream; (e) hydrolyzing said hemicelluloses to produce monomeric sugars; and (f) recovering said monomeric sugars. The process as described is complicated and no proof of working is provided in this document. Furthermore, the number of products as taken out is limited.

Reference may be made to “Valorization of Rice Straw for Ethanol Production and Lignin Recovery Using Combined Acid- Alkali Pre -treatment” by Amandeep Kaur et al., BioEnergy Research, https://doi.org/10.1007/sl2155-019-Q9988-3. As per Amandeep Kaur et al. rice straw was sequentially pre-treated with sulphuric acid (3% v/v) and sodium hydroxide (4% w/v) which resulted in the removal of ~ 90% hemicelluloses and ~ 55% lignin, respectively. The pre-treated rice straw was saccharified with cellulases to produce reducing sugars, which were further fermented with Saccharomyces cerevisae HAU. The acid hydrolysate produced after acid treatment was also subjected to fermentation. The black liquor obtained as a by-product of alkali treatment was used to recover lignin by direct acidification with HC1. The process as described is complicated and no proof of working is provided in this document. Furthermore, the number of products as taken out is limited.

Indian Patent Application No. 201821005003 discloses a method for production of fermentable sugars from lignocellulosic biomass, comprising: a) feeding a grounded lignocellulosic biomass feedstock into a pretreatment reactor system for dilute acid impregnation at room temperature or at a temperature ranging from 50-100°C for a period 5- 60 minutes to render it acid-soaked; b) removing 40% - 70% acid from said acid-soaked biomass by pressing in a hydraulic press; c) feeding said pressed biomass to a plug mill using feed hopper with feed rate of 8-12 kg/hour for conversion of biomass material into solid plug(s); d) treating said solid plug(s) with dilute acid in an amount of 0.02 to 3% w/w of the biomass having pH 1-3 at 120-200°C for a residence time in the range of 8-12 minutes for conversion into biomass slurry; e) centrifuging said biomass slurry for separating solids and liquids, followed by washing solid mass to a pH of 7.0; and f) hydrolyzing said acid pretreated solid biomass with an additive and enzyme for 40-50 hours in an incubator shaker at 45-55°C having speed of 180-220 rpm to obtain fermentable sugars. The document however is purely directed towards increasing the production fermentable sugars (which will be used for production of ethanol) and is not directed towards production of three or more valuable products from biomass.

Indian Patent Application No. 201821008982 discloses a process for production of ethanol from a lignocellulosic biomass comprising; (i) adding slurry of a pre-treated lignocellulosic biomass comprising C5 and C6 sugars in a fermenter system; (ii) selectively fermenting mainly C5 sugars by incubating the pre-treated lignocellulosic biomass with a cellulase enzyme, cofermenting microorganism and nutrient to obtain ethanol; (iii) hydrolysing by heating the fermenter system to 48-55°C for a period of 18 to 24 hours; (iv) allowing the fermenter system to cool to a temperature of 35-37°C; and (v) selectively fermenting C6 sugars by inoculating the system with a second dose of co-fermenting microorganism to obtain ethanol. The document however is purely directed towards increasing the production of ethanol and is not directed towards production of three or more valuable products from biomass.

Indian Patent Application No. 201921025442 discloses a two stage process for production of ethanol from a lignocellulosic biomass, the process comprising: i. introducing a slurry of pre-treated lignocellulosic biomass comprising C5 and C6 sugars into a fermentor; ii. fermenting mainly C5 sugars by incubating the pretreated lignocellulosic biomass of step (i) with first cellulase enzyme, co-fermenting microorganism, nutrient in the fermentor at 30- 37°C for a period of 16 to 24 hours; iii. adding second cellulase enzyme to the fermentation broth of step (ii) and increasing the temperature to 45-55°C for hydrolysis; iv. allowing the fermentation broth of step (iii) to cool to a temperature of 35-38°C; and v. fermenting C6 sugars by incubating the broth of step (iv) with a second dose of cofermenting microorganism for a period of 6-8 hours to obtain ethanol, wherein the first cellulase enzyme is obtained from Pencillium funiculosum MRJ16; wherein the second cellulase enzyme is Ctec 3 that is a cellulase hydrolyzing enzyme including lytic polysaccharide monooxygenases; wherein the co-fermenting microorganism is Saccharomyces cerevisiae. The document however is purely directed towards increasing the production of ethanol and is not directed towards production of three or more valuable products from biomass.

Thus, there exists a need to provide a process and a system for producing three or more valuable products from biomass.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in a simplified format that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention, and nor is it intended for determining the scope of the invention.

The present invention provides a process for recovering three or more valuable products from biomass, wherein the valuable products are selected from a group comprising cellulose, silica, lignin, ethanol and cattle feed. In particular, the present invention provides a process for recovering four or more valuable products from biomass, wherein the valuable products are selected from a group comprising cellulose, silica, lignin, ethanol and cattle feed. In a more preferred aspect, the invention provides a process for recovering all of valuable products selected from cellulose, silica, lignin, ethanol and cattle feed.

The present invention provides a system for recovering three or more valuable products from biomass, wherein the valuable products are selected from a group comprising cellulose, silica, lignin, ethanol and cattle feed. In particular, the present invention provides a system for recovering four or more valuable products from biomass, wherein the valuable products are selected from a group comprising cellulose, silica, lignin, ethanol and cattle feed. In a more preferred aspect, the invention provides a system for recovering all of valuable products selected from cellulose, silica, lignin, ethanol and cattle feed.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

In order that the invention may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying drawings. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present invention where:

Figure 1 demonstrates the process for recovering cellulose, silica, lignin, bio-ethanol and bio plastics from bio mass in accordance with an embodiment of the invention;

Figure 2 demonstrates a more detailed process for obtaining the first stage slurry (SL-1) in accordance with an embodiment of the invention; and Figure 3 demonstrates a more detailed process for recovering cellulose from the first stage residue in accordance with an embodiment of the invention; and

Figure 4 demonstrates a block diagram of a system for recovery of cellulose, silica, lignin, bio-ethanol and cattle feed from bio mass in accordance with an embodiment of the invention.

It may be noted that to the extent possible, like reference numerals have been used to represent like steps in the drawings. Further, skilled artisans will appreciate that the steps are illustrated for simplicity in the form of blocks, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION OF THE INVENTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

As used herein, and unless the context dictates otherwise, the terms "coupled to", “connected to”, “operably connected to”, “operatively connected to” are intended to include both direct connection / coupling (in which two elements that are coupled / connected to each other contact each other) and indirect coupling / connection (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Similarly, the terms “connected to” and “connected with” are used synonymously.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The methods, devices, and examples provided herein are illustrative only and not intended to be limiting.

The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims. Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Referring to Figure 1, there is illustrated a block diagram of a process (100) for recovering three or more valuable products from biomass, wherein the valuable products are selected from a group comprising cellulose, silica, lignin, ethanol and cattle feed, said process comprising: subjecting (102) the bio mass to heat treatment under alkaline conditions to obtain a first stage slurry (SL-1); separating (104) a first stage residue (R-l) from the first stage slurry (SL-1) to obtain a first stage mother liquor (ML-1); recovering (106) cellulose from the first stage residue (R-l); concentrating (108) the first stage mother liquor (ML-1) by about 20 to 40% to obtain a concentrated mother liquor (CML); adjusting (110) pH of the concentrated mother liquor (CML) to a value in the range of 7.5 to 9.0 to obtain a second stage slurry (SL-2); separating (112) silica from the second stage slurry (SL-2) to obtain a second stage mother liquor (ML-2); subjecting (114) the second stage mother liquor (ML-2) to acid hydrolysis at elevated temperature followed by cooling to obtain a third stage slurry (SL-3); separating (116) lignin from the third stage slurry (SL-3) to obtain a third stage mother liquor (ML-3); subjecting (118) the third stage mother liquor (ML-3) to fermentation to obtain bio-ethanol and a fourth stage residue (R-4); and processing (120) the fourth stage residue (R-4) to obtain cattle feed.

Referring to Figure 2, in an embodiment of the invention, subjecting (102) the biomass to heat treatment under alkaline conditions to obtain the first stage slurry (SL-1) comprises: mixing (122) finely divided biomass with water and a source of alkali to obtain a first reaction mass; subjecting (124) the first reaction mass thus obtained to heat treatment at a temperature in the range of 130°C to 160°C, a pressure in the range of 4 to 12 bars for a time period in the range of 30 minutes to 120 minutes followed by release of pressure to one atmosphere to obtain the first stage slurry (SL-1).

In an embodiment of the invention, the amount of water added to the dry solid mass is in the range of 3 to 8 times the weight of the dry solid mass.

In another embodiment of the invention, an amount of the source of alkali added is such that a pH of the reaction mass is in the range of 8.0 to 12.5.

Referring to Figure 3, in an embodiment of the invention, recovering (106) cellulose from the first stage residue (R-l) comprises: neutralizing (126) the first stage residue (R-l) to obtain a neutralized mass; washing (128) the neutralized mass with water followed by removing water to obtain a wet cellulosic mass; and drying (130) the wet cellulosic mass to obtain cellulose.

In an embodiment of the invention, the first stage mother liquor (ML-1) is subjected to evaporation to obtain the concentrated mother liquor (CML).

In another embodiment of the invention, the concentrated mother liquor (CML) is maintained at a temperature in the range of 50°C to 70°C prior to adjusting its pH.

In still another embodiment of the invention, the pH of the concentrated mother liquor (CML) is adjusted to a value in the range of 7.5 to 9.0 to obtain the second stage slurry (SL- 2).

In yet another embodiment of the invention, the third stage slurry (SL-3) is obtained by subjecting the second stage mother liquor (ML-2) to acid hydrolysis at a temperature in the range of 80°C to 98°C for a time period in the range of 2 to 4 hours followed by cooling the reaction mass to a temperature in the range of 10°C to 25°C.

In still another embodiment of the invention, the third stage mother liquor (ML-3) is concentrated by about 15 to 30% prior to subjecting the same to fermentation.

In a further embodiment of the invention, the third stage mother liquor (ML-3) subjected to enzymatic fermentation using suitable enzyme. In a furthermore embodiment of the invention, the enzyme is selected from a group comprising of alfa amylase and cellulose.

In another embodiment of the invention, the bio mass is selected from a group comprising rice stubble, Rice straw, Wheat straw and Cotton stock.

Referring to Figure 4, the invention further provides a system (200) for recovery of cellulose, silica, lignin, bio-ethanol and cattle feed from bio mass, said system comprising: a heat treatment unit (202) adapted to subject the bio mass to heat treatment under alkaline medium to obtain a first stage slurry (SL-1); a first separation unit (204) operably connected to the heat treatment unit (202), the first separation unit (204) being adapted to separate a first stage residue (R-l) from the first stage slurry (SL-1) to obtain a first stage mother liquor (ML-1); a cellulose recovery unit (206) operably coupled to the first separation unit (204), the cellulose recovery unit being adapted to recover cellulose from the first stage residue (R- 1); a first concentrating unit (208) operably coupled to the first separation unit (204), the first concentrating unit (208) being adapted to concentrate the first stage mother liquor (ML- 1) by about 25 to 40% to obtain a concentrated mother liquor (CML); a pH adjusting unit (210) operably coupled to the first concentrating unit (208), the pH adjusting unit (210) being adapted to adjust a pH of the concentrated mother liquor (CML) to a value in the range of 7.5 to 9.0 to obtain a second stage slurry (SL-2); a second separation unit (212) operably connected to the pH adjusting unit (210), the second separation unit (212) being adapted to separate silica from the second stage slurry (SL-2) to obtain a second stage mother liquor (ML-2); a hydrolyzer unit (214) operably coupled to the second separation unit (212), the hydrolyser unit (214) being adapted to subject the second stage mother liquor (ML-2) to acid hydrolysis at elevated temperature followed by cooling to obtain a third stage slurry (SL-3); a third separation unit (216) operably coupled to the hydolyzer unit (214), the third separation unit (216) being adapted to separate a lignin from the third stage slurry (SL- 3) to obtain a third stage mother liquor (ML-3); a fermentation unit (218) operably coupled to the third separation unit (216), the fermentation unit (218) being adapted to subject the third stage mother liquor (ML-3) to enzymatic hydrolysis to obtain bio-ethanol and a fourth stage residue (R-4); and a cattle feed producing unit (220) operably connected to the fermentation unit (218), the cattle feed producing unit (220) being adapted to convert the fourth stage residue (R-4) to cattle feed by drying.

Reference is drawn to the following example to illustrate the process of invention.

Example 1: Rice Straw Grinding and Pre-treatment to obtain first stage slurry (SL-1) 50 kg of rice straw having 10% moisture was taken. The rice straw was ground to < 100p size. To the ground rice straw, 225 kg of water and 7.5 kg of NaOH was added to obtain a reaction mass. The pH of the reaction mass was in the range of 11.5 to 12 and the reaction mass weighed about 282.5 kg. The reaction mass was heated to about 110 °C to 140°C for a time period of about 1-2 hours. Steam was used for the purpose of heating the reaction mass. The reaction mass maintained under a pressure of about 8 bars for the period of 30 to 60 minutes. Thereafter, the pressure was suddenly released and the temperature was allowed to drop to obtain the first stage slurry (SL-1).

Example 2: Production of Cellulose from first stage slurry (SL-1)

282.5 kg of first stage slurry (SL-1) was decanted to obtain a first stage residue (R-l) and first stage mother liquor (ML-1). The first stage residue (R-l) weighed roughly 80 kg while the first stage mother liquor (ML-1) weighed roughly 20.25 kg. The first stage residue (R-l) had a moisture content of about 75%. The first stage residue (R-l) was neutralized using dilute acid (for example, dilute hydrochloric acid) to obtain a neutralized mass. The neutralized mass was washed with water followed by removing water to obtain wet cellulosic mass. The wet cellulosic mass was dried to obtain 21 kg of cellulose having a moisture content of roughly 5%. Comparative Example:

50 kg of rice straw having 10% moisture was taken. The rice straw was ground to <100p size. To the ground rice straw, 225 kg of water and 7.5 kg of concentrated HC1 was added to obtain a reaction mass. The pH of the reaction mass was in the range of 2 to 3 and the reaction mass weighed about 282.5 kg. The reaction mass was heated to about 110 to 140°C for a time period of about 1-2 hours. Steam was used for the purpose of heating the reaction mass. The reaction mass maintained under a pressure of about 8 bars for the period of 30-60 minutes. Thereafter, the pressure was released and the temperature was allowed to drop to obtain slurry. The slurry did not yield cellulose.

Example 3: Production of Silica from first stage mother liquor (ML-1)

202.5 kg of first stage mother liquor (ML-1) as obtained in Example 2 was concentrated in a multi-effect evaporator to obtain about 139 kg of concentrated mother liquor (CML). The pH of the concentrated mother liquor (CML) is adjusted to a value in the range of 7.5 to 9.0 by adding dilute acid (for example, dilute hydrochloric acid) and to obtain a second stage slurry (SL-2). Temperature of the concentrated mother liquor (CML) was maintained at about 60°C during this process. The second stage slurry (SL-2) was decanted to obtain 12.5 kg of wet silica in the form of a second stage residue (R-2) and 126.5 kg of second stage mother liquor (ML-1). The 12.5 kg of second stage residue (R-2) contained 60% moisture. Thus, the second stage residue was dried to obtain approximately 5.25 kg of silica powder containing about 5% moisture.

Comparative Example:

50 kg of rice straw having 10% moisture was taken. The rice straw was ground to < 100p size. To the ground rice straw, 225 kg of water and 7.5 kg of concentrated HC1 was added to obtain a reaction mass. The pH of the reaction mass was in the range of 2 to 3 and the reaction mass weighed about 282.5 kg. The reaction mass was heated to about 110 to 140°C for a time period of about 1-2 hours. Steam was used for the purpose of heating the reaction mass. The reaction mass maintained under a pressure of about 8 bars for the period of 30 to 60 minutes. Thereafter, the pressure was released and the temperature was allowed to drop to obtain slurry. The slurry did not yield cellulose. The slurry was concentrated and pH of the slurry was adjusted to a value in the range of 7.5 to 9.0. The slurry did not yield silica.

Example 4: Production of Lignin from Second stage mother liquor (ML-2)

126.5 kg of second stage mother liquor (ML-2) as obtained in Example 3 was subjected to acid hydrolysis at a temperature in the range of 85°C to 95°C for a time period of about 3 hours followed by cooling the reaction mass to a temperature of about 20°C to obtain a third stage slurry (SL-3). The third stage slurry (SL-3) is separated into a lignin containing part in the form of a third stage residue (R-3) and third stage mother liquor (ML-3). The third stage residue (R-3) weighed about 10 kg and contained about 75% moisture while the third stage mother liquor (ML-3) weighed about 116.5 kg and contained about 15% solids. Thereafter, the third stage residue (R-3) is dried to obtain about 2.6 kg of lignin having about 3% moisture.

Example 5: Production of Alcohols and Cattle feed from Third stage mother liquor (ML-3)

116.5 kg of third stage mother liquor (ML-3) containing about 15% solids as obtained in Example 4 was concentrated in a multi-effect evaporator to obtain about 70 kg of concentrated third stage mother liquor (CML-3). The concentrated third stage mother liquor (CML-3) was found to be rich in xylose. The concentrated third stage mother liquor (CML- 3) may also comprise substantial quantities of glucose. The concentrated third stage mother liquor (CML-3) is subjected to fermentation to obtain bio-ethanol and a fourth stage residue (R-4). In particular, the fermentation was carried out in a fermentation tank using alpha amylase and cellulase enzymes. After the fermentation, the material which has been subjected to fermentation is subjected to separation to give the fourth stage residue and fraction which is rich in bio-ethanol. The fraction which is rich in bio-ethanol may be subjected to distillation, rectification and other processes to improve the purity of bio- ethanol. The fourth stage residue (R-4) is subjected to washing and drying to obtain cattle feed.

Thus, it can be observed that the present invention produces a variety of value added products from the bio-mass. As each of the value added product has significant demand in market, the person implementing the process can earn more amount of money by selling these value added products. It can be seen that in the earlier processes, these value added products were not recovered separately. For instance, cellulose, lignin, and silica are not recovered separately but come out together in the form of a mixture. Because of the above, it is difficult to separate cellulose, lignin, and silica from such a mixture and hence, their economic value is not fully realized.

While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.