Method for preparing a lignocellulosic biomass derived from paper waste, in particular in order to enzymatically hydrolyse same

Abstract

The invention relates to a method for preparing pulp from a lignocellulosic biomass comprising paper waste, which comprises the following steps: a) a step of impregnating the lignocellulosic biomass with an acid liquor, during which all of the acid liquor added is absorbed by the lignocellulosic biomass and the impregnated lignocellulosic biomass resulting from the impregnation has a total solids content lower than the content of the lignocellulosic biomass before carrying out step a); b) a pulping step during which the impregnated lignocellulosic biomass of step a) is suspended in water and a pulp having a total solids content of 5% to 40% by weight is obtained, the impregnated lignocellulosic biomass of step a) being sent directly to the pulping step b) with no further intermediate step; and c) a step of stabilising the pH of the pulp of step b) at a target value.

Description

Description Title of the invention: PROCESS FOR PREPARING A LIGNOCELLULOSIC BIOMASS FROM PAPER WASTE, PARTICULARLY FOR ITS ENZYMATIC HYDROLYSIS Field of invention

[0001] The invention relates to the field of the production of fermentable sugars and concerns the use of residual lignocellulosic resources such as paper / cardboard waste as a substrate for a process for preparing said sugars. The invention describes in particular the process used for the preparation of the raw material and its treatment allowing the production of a sugar syrup, in particular a syrup mainly composed of glucose which can be used as a raw material, in particular in the biofuel or biotechnology industry.

[0002] In particular, the invention relates to a method for producing a sugar syrup comprising fermentable sugars, in particular a syrup comprising glucose, from lignocellulosic biomass comprising papermaking waste, in particular printable paper, printed paper, graphic paper, packaging paper or cardboard.

[0003] The use of the process for producing a sugar syrup to produce bio-sourced molecules or a process for producing biofuels, in particular ethanol, are also objects of the present invention. State of the prior art

[0004] The lignocellulosic biomass mainly used today on a pilot and industrial scale is the so-called 2G (second generation) biomass, i.e. a plant-type biomass, such as residues from the forestry and agricultural industries (wheat straw, corn cobs and sugarcane bagasse) (Nizami et al., 2017). While this raw material has the advantage of not competing with food resources, it suffers from several limitations, including a low development of the collection and massification sector of deposits, exposure to seasonal variations in volumes, quality and availability, competition with soil fertilization and plant cover of fields, a high hemicellulose and lignin content making access to cellulose more complex and the glucose yield lower.

[0005] The use of waste paper and cardboard makes it possible to overcome a large part of these limits and to access products richer in cellulose, via less intensive and less complex processes due to an initial pre-treatment undergone by the virgin material upstream of its production chain (in paper mills during its production).

[0006] The state of the art in terms of valorization of lignocellulosic biomass includes several types of treatment processes. These processes all aim to hydrolyze the cellulose and / or hemicellulose constituting the biomass into monomers.

[0007] Hydrolysis can be done (Nizami et al., 2017): By biological or biochemical means, using enzymes and / or microorganisms; By thermochemical and / or mechanical means.

[0008] Non-biological processes include: concentrated acid processes, gasification, hydropyrolysis and pyrolysis

[0009] For biological processes, the first step is to pretreat the biomass, in order to increase the digestibility of cellulose and the release of monomeric sugars (mainly glucose). There are different pretreatment techniques (Baruah, L, et al. (2018). Recent trends in the pretreatment of lignocellulosic biomass for value-added products. Frontiers in Energy Research, 6, 141), including: physical processes (grinding, etc.), physicochemical processes, including steam explosion, AFEX - Ammonia Fiber Explosion process, acid pretreatments, alkaline pretreatments, oxidative techniques, biological processes.

[0010] Combinations of these pretreatments are also commonly used. In particular, many processes involve impregnating the lignocellulosic biomass with an acid solution, also known as acid liquor, before pretreatment by steam explosion. These pretreatments help to de-separate the fibers making up the biomass and thus improve the accessibility of the cellulose to the enzymes that hydrolyze it. However, the acid is often used diluted and in large quantities.

[0011] Thus, these pretreatments are generally expensive and can have a harmful impact on the environment because they use significant quantities of energy and / or chemicals.

[0012] In order to limit acid consumption, processes have been implemented to recover part of the acid liquor by draining or pressing the impregnated biomass. This is the case of the processes described in documents FR3053969, FR3075202, FR3075203 and FR3069248.

[0013] It is also known to adjust the composition of the acid liquor depending on the variability of the substrate or the amount of substrate. Another method to reduce the amount of acid liquor used is to separate the fine particles rich in minerals (calcium, magnesium, etc.) from the biomass to be impregnated in order to prevent these minerals from reacting with the acid to create salts, as described for example in document WO2011028554.

[0014] Although the processes described above are effective for treating lignocellulosic biomass from agricultural or forestry residues, they are little or not at all suitable for treating biomass such as paper and cardboard waste or derived streams such as newspapers, magazines or paper mill sludge, due to the differences in properties of these biomasses. Indeed, this biomass has already been pretreated by the paper industry during the production of paper and cardboard. As a result, its lignin content is much lower and cellulose polymers are more reactive to enzymatic hydrolysis than those of agricultural and forestry residues. Furthermore, the biomass considered has a rheological behavior and a basicity that requires the implementation of specific operations. Finally, enzymatic hydrolysis requires pH regulation to a value close to 5.This regulation proves complex to implement for the aforementioned paper / cardboard type biomasses due to a significant quantity of ash (close to 20% by mass of the dry matter), and in particular the quantity of minerals (mainly calcium) which will react with the acid used to form salts (mainly CaSO4 if the acid used is sulfuric acid). Thus, the pH takes a very long time to stabilize, and it is necessary to add very large quantities of acids to obtain a stable pH close to 5. Finally, these biomasses have a significant absorption capacity, causing swelling and making homogeneous acid impregnation and uniform mixing in the reactor difficult.

[0015] The invention aims to overcome all or part of the disadvantages mentioned, by proposing a method for preparing a pulp from a residual lignocellulosic biomass from papermaking waste, in particular without implementing thermal or chemical pretreatment, in particular without implementing pretreatment requiring a temperature above 100°C. The invention aims in particular to reduce the pH stabilization time and / or the quantity of acid to be added for enzymatic hydrolysis. This preparation method can in particular be integrated into a method for producing a sugar syrup from such biomass. Summary

[0016] The present invention relates to a method for preparing a lignocellulosic biomass pulp comprising papermaking waste, in particular cardboard packaging, printable paper, printed paper or cardboard, said method comprising the following steps: a) a step of impregnating said lignocellulosic biomass with an acid liquor, during which all of the added acid liquor is absorbed by said lignocellulosic biomass, and the impregnated lignocellulosic biomass resulting from the impregnation has a total dry matter content lower than the content of the lignocellulosic biomass before carrying out step a), b) a pulping step during which said impregnated lignocellulosic biomass from step a) is suspended in water, in particular with stirring, and a pulp having a total dry matter content of 5% to 40% by mass is obtained,said impregnated lignocellulosic biomass from step a) being sent directly to step b) of pulping without any other intermediate step, c) a step of stabilizing the pH of the pulp from step b) to a target value.,

[0017] The implementation of the process according to the invention makes it possible in particular to reduce the overall quantity of acid to be added and to significantly reduce the duration of step c) and consequently the overall duration of the process.

[0018] It also makes it possible to limit the number of steps, since all of the acid liquor is impregnated in the biomass, there is no need for draining or separation. Furthermore, the impregnated biomass induces less corrosion due to the absorption of the acid. In particular, the method according to the invention does not include any additional thermal or chemical treatment before the impregnation step and / or between the impregnation step and the pulping step, and in particular no thermal treatment step requiring heating to a temperature above 100°C.

[0019] Furthermore, step a) of impregnation is carried out under conditions in which no release of sugars occurs.

[0020] Finally, depending on the conditions of implementation of the impregnation stage, and in particular the duration of the impregnation, the pH, the temperature, and depending on the nature of the bacteria present in the biomass, we may observe a more or less significant hygienization of the biomass.

[0021] The impregnation step a) may comprise at least one of the following features: the acid liquor comprises an acid in an amount of 10 to 100% by mass, preferably 10 to 45% by mass, more preferably 20 to 37% by mass, the acid liquor comprises an acid selected from sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid and citric acid, an impregnation ratio of 30 to 177% of pure acid per kg of dry matter, an impregnation time of 1 to 60 minutes and preferably 3 to 30 minutes, an implementation at a temperature of 10 to 80°C, preferably 10 to 60°C, more preferably 15 to 55°C, more preferably at room temperature, implementation at a pressure of 0 to 2 bar, preferably 0 to 1 bar, the impregnated lignocellulosic biomass obtained at the end of this step a) has a total dry matter content of 40 to 95% by mass, preferably 60 to 95% by mass, more preferably between 70 and 95%, even more preferably 75 to 95% by mass, even more preferably 75 to 85% by mass.

[0022] Advantageously, when the acid is chosen from sulfuric acid and nitric acid, the impregnation ratio is 80 to 170 g of pure acid per kg of dry matter and preferably 115 to 140 g of pure acid per kg of dry matter.

[0023] Advantageously, when the acid is phosphoric acid, the impregnation ratio is 30 to 177 of pure acid per kg of dry matter, advantageously 30 to 80 g of pure acid per kg of dry matter and preferably 30 to 60 g of pure acid per kg of dry matter.

[0024] Step b) of pulping may comprise at least one of the following characteristics: an implementation for a duration of 5 to 180 minutes, preferably 20 to 60 minutes, implementation at a temperature of 10 to 80°C, preferably 37 to 55°C, implementation at a pressure of 0 to 2 bar, preferably 0 to 1 bar, implementation with stirring, the pulp obtained has a pH of 2 to 5, preferably 3 to 5, more preferably 3.5 to 4.5.

[0025] Stabilization step c) may comprise at least one of the following features: the target pH value is a pH range of 4 to 6, preferably 4.5 to 5.5, or is within this range, operation at a temperature of 10 to 80°C, preferably 37 to 55°C, operation at a pressure of 0 to 2 bar, preferably 0 to 1 bar, operation with stirring, a stabilization time of 15 minutes to 24 hours, preferably 30 minutes to 6 hours, more preferably 30 minutes to 3 hours. a sub-step of adjusting the pH of the pulp of step c) to a target value, in which the pH is adjusted to said target value by adding to the pulp (i) an acid or (ii) said non-impregnated lignocellulosic biomass or (iii) a base, preferably by adding only (i) an acid or (ii) said non-impregnated lignocellulosic biomass.

[0026] Advantageously, the treatment method according to the invention may comprise, upstream of step a) of impregnation, a preliminary step of preparation of said lignocellulosic biomass by grinding, stone removal, iron removal, refining and / or thermal hygienization.

[0027] The invention also relates to a process for producing a sugar syrup from lignocellulosic biomass comprising paper waste, in particular printable paper, printed paper, packaging cardboard or cardboard, said process comprising the following steps:

[0028] the implementation of the process for preparing a pulp of said biomass according to the invention, followed by:

[0029] d) a step of enzymatic hydrolysis of the stabilized pulp obtained at the end of step c) of the preparation process, in which the cellulose and the hemicellulose which it contains are converted into a sugar syrup comprising fermentable sugars, and e) a step of recovery of the sugar syrup comprising fermentable sugars obtained at the end of step d).

[0030] By implementing steps a) to c) of the preparation process according to the invention, the implementation of steps d) and / or e) does not require the addition of an alkaline compound, which makes it possible to reduce the overall consumption of reagents used.

[0031] Furthermore, advantageously, the method according to the invention does not include heat treatment, in particular at a temperature above 100°C, before step a) of the process and / or between step a) and b) and / or between step c) of the preparation process and the hydrolysis step.

[0032] In a preferred embodiment, the enzymatic hydrolysis step d) can be carried out by sequentially adding impregnated biomass obtained at the end of step a) of the preparation process. This embodiment makes it possible to obtain a rapid increase in load without observing any swelling of the biomass.

[0033] In particular, during step d), it is then possible to proceed as follows: (i) a determined quantity of impregnated lignocellulosic biomass obtained at the end of step a) of the preparation process is added, then, (ii) optionally the pH is adjusted to a value of 4 to 6, preferably 4.5 to 5.5, and, after stabilization of the pH, (iii) a determined quantity of enzymes is added.

[0034] All the steps of the preparation process according to the invention can be implemented in a single piece of equipment. Advantageously, all the steps of the process for producing a sugar syrup can be implemented in a single piece of equipment.

[0035] In certain embodiments, the steps of the preparation method and / or the production method of a sugar syrup according to the invention can be implemented without adding base, only by adding acid, impregnated biomass and / or non-impregnated biomass, thus making it possible to limit the overall quantity of additives added.

[0036] The invention also relates to the use of the method for producing a sugar syrup to produce bio-sourced molecules, in particular bio-sourced molecules chosen from surfactants, in particular alkyl polyglucosides, pigments, phenylpropanoids, organic acids, such as lactic acid, 3-hydroxypropionic acid, acetic acid, butyric acid, capric acid, citric acid, fumaric acid, malic acid, propionic acid, pyruvic acid, succinic acid, levulinic acid, 2,5-furandicarboxylic acid, alcohols, in particular C2-C4 alcohols, such as ethanol, 1,3-propanediol, 2,3-butanediol), isobutene and polyols, such as sorbitol, xylitol.

[0037] In particular, the bio-sourced molecules can be chosen from alkyl polyglucosides, pigments, phenylpropanoids, lactic acid, acetic acid, butyric acid, propionic acid, succinic acid, isopropanol and isobutene.

[0038] The invention also relates to a process for producing biofuels, in particular ethanol, comprising steps a) to e) of the process for producing sugars according to the invention and a subsequent fermentation step in order to convert the sugar syrup comprising fermentable sugars recovered at the end of step e) into biofuels, in particular ethanol. Definitions

[0039] The terminology used herein is for the sole purpose of describing particular embodiments and is not intended to limit the subject matter disclosed. Although the The following terms are intended to be well understood by a person of ordinary skill in the art, the following definitions are set forth to facilitate the explanation of the subject matter herein disclosed.

[0040] All technical and scientific terms used herein, unless otherwise defined below, have the same meaning as commonly understood by a person of ordinary skill in the art. References to techniques employed herein are intended to refer to the techniques as commonly understood in the art, including variations of such techniques or substitutions for equivalent techniques that would be apparent to a person skilled in the art. In describing the subject matter now disclosed, it will be understood that a number of techniques and steps are disclosed. Each of these has an individual advantage and each may also be used in conjunction with one or more, or in some cases all, of the other techniques disclosed.

[0041] In the context of the invention, the term "sugar syrup" refers to a viscous and thick liquid comprising sugars in solution. The term "sugar syrup" may be interchanged with the term "sweet juice".

[0042] In the context of the invention, the term "fermentable sugars" refers to simple sugars or mixtures thereof, for example glucose, fructose, arabinose, mannose, galactose, xylose. These "simple sugars" are capable of fermenting under the action of yeasts or bacteria or fungi to produce various molecules with high added value. These are in particular monosaccharides (i.e. sugars comprising 5 or 6 carbon atoms), in particular a hexose, such as glucose. Preferably, "fermentable sugars" refer to fermentable monomeric sugars, i.e. comprising a single unit. Even more preferably, the "fermentable sugars" comprise or consist essentially of glucose.

[0043] In the context of the invention, the dry matter content (denoted MS) represents all the dry matter present in the product, measured for example according to the protocol described in standard NF EN 15934 - September 2012. The free glucose content represents the quantity of glucose (in dry mass) in relation to the total quantity of matter (also in dry mass) present in the product, this parameter being conventionally measured in the liquid phase by HPLC or by an equivalent analytical method then estimated by calculation.

[0044] In the present application, the pH is considered to be stabilized (stable) when the pH variation per hour is less than a threshold value. This threshold value of pH variation is typically 0 to 0.5 pH points / hour, preferably 0 to 0.2 pH points per hour. Detailed description

[0045] In the following description, the different embodiments described, and in particular the preferred embodiments of each step can be combined depending on the desired objective.

[0046] Description of lignocellulosic biomass

[0047] In the context of the invention, the term "lignocellulosic biomass" refers to a substrate essentially consisting of cellulose (30 to 70%), hemicellulose (5 to 35%) and lignin (5 to 25%). Cellulose is a polymer of glucose, i.e. hexose, hemicellulose is a polysaccharide essentially consisting of pentoses (e.g. xylose and arabinose) and glucose, and lignin is a macromolecule rich in phenolic units. Cellulose is the main source of fermentable sugars.

[0048] The “lignocellulosic biomass” used in the invention comprises, in particular consists of, papermaking waste.

[0049] Paper waste may have been recycled several times, for example up to 7 times, and the average size of the fibers contained in this paper waste is generally between 0 mm and 2 mm, preferably between 0.1 mm and 1.5 mm.

[0050] In the context of the invention, paper waste comprises or consists essentially of paper and cardboard waste. In general, paper and cardboard waste corresponds to a mixture of paper and cardboard waste chosen from gray cardboard, newspapers and magazines, printed papers of the office paper type, corrugated cardboard, alone or in mixtures.

[0051] This mixture of paper and cardboard waste may include from 5 to 80% by mass of grey cardboard, from 5% to 80% by mass of newspapers and magazines, from 5% to 80% by mass of printed papers such as office papers and from 5% to 100% by mass of corrugated cardboard.

[0052] In a particular embodiment of the invention, the paper waste is chosen from the group consisting of paper (in particular printed or printable paper), cardboard, packaging cardboard, in particular newspapers, magazines and paper sludge. This waste may contain undesirable impurities such as plastics and metals, as well as ink constituents, said impurities being present in small quantities.

[0053] In a preferred embodiment of the invention, the paper waste is a mixture of low-quality lignocellulosic waste (of the paper and cardboard type) in the following average proportions (+ / - 15%, the total dry matter percentage not exceeding 100%):

[0054] Grey cardboard: 35% by mass

[0055] Newspapers: 11% by mass

[0056] Magazines: 27% by mass

[0057] Office papers: 13% by mass

[0058] Corrugated cardboard: 5% by mass

[0059] Other fibrous materials: 2.5% by mass

[0060] Impurities: 6.5% by mass

[0061] The lignocellulosic biomass comprising papermaking waste used in the present invention, before any step of grinding, stone removal, de-ironing, refining and / or sanitization, and / or before impregnation, i.e. the “raw” lignocellulosic biomass, may have one or more of the following characteristics:

[0062] - a total dry matter content of between 70% and 100%, in particular between 85% and 96% (for example measured according to standard NF EN 12880-November 2000),

[0063] - a calcium content expressed as CaO per kg of dry matter of biomass of 60 to 200 g CaO per kg of dry matter of biomass, most often 80 to 180 g / kg of dry matter, (for example measured according to standard NF EN13-346 & ISO 11-885),

[0064] - an ash content of 15 to 25% by mass, most often 18 to 24% by dry mass (for example measured according to standard NF EN 15935 of November 2000 by drying at 105°C then calcination at 550°C),

[0065] Due to this high ash content, particularly calcium, the lignocellulosic biomass used in the present invention has a high buffering capacity which makes it difficult to adjust the pH necessary for carrying out enzymatic hydrolysis. By way of comparison, biomass from an agricultural or forestry residue has a much lower calcium content expressed as CaO, generally less than 10 g CaO / kg of dry matter of biomass.

[0066] The lignocellulosic biomass used in the present invention is thus very rich in ash, and in particular in calcium carbonate, which differentiates it from other biomasses, and in particular forestry and agri-food residues, usually used for the production of 2G sugars (see Table 1). This high level of ash and calcium carbonate explains the importance of developing a process adapted to this particular biomass.

[0067] However, the invention is not exclusively intended for lignocellulosic biomasses having a high calcium content. It can also be applied, in other embodiments not described here, to lignocellulosic biomasses containing a reduced amount of calcium.

[0068]

[0069] [Table 1] Table 1

[0070] %MS: % mass relative to dry matter

[0071] Furthermore, the calcium content of paper / cardboard waste is highly variable. As an illustration, the following table shows the calcium content and ash content of 5 different samples of paper and cardboard waste:

[0072] Detailed description of the treatment process

[0073] The preparation process according to the invention makes it possible in particular to optimally regulate the pH of a pulp composed of paper and cardboard waste in aqueous solution, in particular to guarantee a stable pH close to 5 for the enzymatic hydrolysis of this pulp. It is therefore possible to produce 2G sugars from lignocellulosic waste in an economically viable manner, using a reduced quantity of reagents.

[0074] Optional preparation step

[0075] The process may include a preliminary step of preparing the lignocellulosic biomass.

[0076] This preparation may include crushing, stone removal, iron removal, refining and / or thermal hygienization.

[0077] When used, grinding can, for example, produce biomass particles with a size of less than 100 mm and in particular a size of 10 to 50 mm.

[0078] Stone removal and / or iron removal, optionally supplemented by refining (for example <10mm), can produce a biomass containing at most 0.5% by mass of stone and / or metallic material.

[0079] This preparation step can optionally be completed by thermal hygienization of the biomass, for example by drying. This drying is typically carried out at a temperature of 70°C to 100°C, preferably 80°C to 95°C.

[0080] Step a) impregnation

[0081] Impregnation is carried out by adding an acid liquor which is completely absorbed by the lignocellulosic biomass.

[0082] Thus, the impregnated lignocellulosic biomass obtained at the end of this step a) has a total dry matter content that is reduced compared to the content of the lignocellulosic biomass before implementing step a), but which nevertheless remains high. This step is thus implemented in such a way as to obtain a total dry matter content that is lower than the content of the lignocellulosic biomass before implementing step a).

[0083] Advantageously, the impregnated lignocellulosic biomass obtained at the end of this step a) may have a total dry matter content of 40 to 95% by mass, preferably 60 to 95% by mass, more preferably between 70 and 95%, even more preferably 75 to 95% by mass, even more preferably 75 to 85% by mass.

[0084] The acid liquor used in step a) may have one or more of the following characteristics: an acid content of 10 to 100% by mass, preferably 10 to 45% by mass, more preferably 20 to 37% by mass, more preferably 25 to 35% by mass, for example 26% by mass, the acid liquor comprises an acid such as sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid or citric acid, an impregnation ratio of 30 to 177 g of pure acid per kg of dry matter.

[0085] The impregnation ratio is more particularly 80 to 170 g of pure acid per kg of dry matter and preferably 115 to 140 g of pure acid per kg of dry matter when the acid is chosen from sulfuric acid and nitric acid.

[0086] The impregnation ratio is more particularly 30 to 80 g of pure acid per kg of dry matter and preferably 30 to 60 g of pure acid per kg of dry matter when the acid is phosphoric acid.

[0087] The acid is usually sulfuric acid or phosphoric acid, but any other acid, such as hydrochloric acid, nitric acid, or citric acid, can be suitable.

[0088] The acid liquor used includes, in particular, at least one acid, and optionally water.

[0089] According to a preferred embodiment, the liquor comprises, in particular consists of, at least one acid and water. The acid content of the liquor may then comprise from 10 to 45% by mass of acid relative to the total mass of the liquor, more preferably from 20 to 37% by mass, more preferably from 25 to 35% by mass, for example 26% by mass.

[0090] Preferably, the acid liquor is an aqueous solution of strong acid, for example chosen from sulfuric acid, hydrochloric acid, nitric acid.

[0091] The impregnation is carried out so that the lignocellulosic biomass absorbs all of the acid liquor and the total dry matter content of the biomass remains high, in particular greater than or equal to 40% by mass, but generally less than 95% by mass, preferably 60 to 95%, more preferably 70 to 95% by mass, preferably 75 to 95% by mass, even more preferably 75 to 85% by mass. The quantity of acid liquor added is thus chosen according to the quantity of lignocellulosic biomass treated and the absorption capacity of the latter. The duration of the impregnation step is sufficient to ensure the diffusion and absorption of all of the acid liquor.

[0092] The soaking time may be 1 to 60 minutes, preferably 3 to 30 minutes after addition of all the acid liquor.

[0093] The impregnation can be carried out at a temperature of 10 to 80°C, preferably 10 to 60°C, more preferably 15 to 55°C, even more preferably at room temperature, for example 15 to 25°C. In particular, temperatures below 60°C can limit thermal degradation of the biomass.

[0094] The impregnation can be carried out at a pressure of 0 to 2 bar, preferably 0 to 1 bar, for example at atmospheric pressure.

[0095] The acid liquor can be added by several methods depending on the preferred configuration and without impact on the biomass (by spraying, complete, fractional or dropwise pouring of the acid liquor onto the biomass). The impregnation can be carried out by any equipment known to those skilled in the art allowing contact between the lignocellulosic biomass and the acid liquor. This contact can be carried out by soaking, for example in a reactor stirred by horizontal or vertical crossing of the biomass in a bed of liquor, or by spraying, for example on a conveyor belt in the biomass or in a conveyor screw.

[0096] The acid liquor can be prepared in advance in any suitable apparatus, for example in a mixing tank equipped with a stirring system or in a mixer (e.g. a static mixer). The apparatus used for preparing the liquor can in particular be connected to an impregnator by one or more lines transporting the liquor. A liquor of a determined concentration can thus be prepared with an adequate flow rate allowing total absorption of the liquor by the biomass.

[0097] After adding the acid liquor, the biomass can be mixed so that the acid liquor is distributed as evenly as possible within the biomass.

[0098] During this impregnation step, the cellulose, hemicellulose and lignin present in the biomass are not degraded: there is therefore no formation of hexoses and / or pentoses. In particular, the hexose and / or pentose content of the impregnated lignocellulosic biomass is zero or at most 1% of the sugar potential of the biomass.

[0099] The biomass thus impregnated is then subjected directly, without an intermediate step, to step b) of pulping. In other words, there is no draining or step of separation of the acid liquor and the biomass, nor heat treatment, nor heat treatment at a temperature above 100 °C, at the end of step a) of impregnation or between step a) of impregnation and step b) of pulping.

[0100] Step b) pulping

[0101] Pulping step b) is a suspension step carried out by adding water to the impregnated lignocellulosic biomass from step a) and which makes it possible to obtain a pulp having a total dry matter content of 5% to 40% by mass, preferably 8 to 20% by mass.

[0102] Pulping step b) is typically carried out by adding water to the impregnated biomass, and preferably by using stirring to obtain a relatively homogeneous suspension without floating agglomerates. Indeed, the agglomerates are generally less well, or not at all, hydrolyzed in a subsequent enzymatic hydrolysis step. Pulping step b) may include stirring, in particular with “pitch blade” type blades.

[0103] This pulping step b) can be carried out at a temperature of 10 to 80°C, preferably 37 to 55°C, at a pressure of 0 to 2 bar, preferably 0 to 1 bar.

[0104] In a particular embodiment of the invention, the pulping step b) is carried out, in particular with stirring, for a period of between 5 and 180 minutes, preferably 20 to 60 minutes, for example for 30 minutes.

[0105] During the pulping stage, the pH increases significantly as the acid present is compensated by the buffering capacity of the biomass. A pH variation of 0.05 to 1 pH point / minute is typically observed, most often a pH variation of 0.05 to 0.2 pH points / minute.

[0106] The pulp obtained at the end of the pulping step has a pH between 2 and 5 (inclusive), preferably between 3 and 5 (inclusive), more preferably between 3.5 and 4.5 (inclusive).

[0107] The pulping stage can be considered complete when the pulp has the desired degree of homogeneity, typically when the majority of the individual pieces of paper have been incorporated into the pulp.

[0108] The pulping step can be carried out in the same equipment as the impregnation step or in different equipment, for example of the same type as the equipment used for pH stabilization and enzymatic hydrolysis.

[0109] Stage c) stabilization

[0110] A pH stabilization step at a target value is then implemented. This step allows the diffusion of the acid and the buffering capacity of the biomass. It is thus typically carried out with stirring of the suspension.

[0111] The target value may be a point value or be defined by a range of values, including a pH range of 4-6, preferably 4.5-5.5.

[0112] The impregnation step according to the invention makes it possible to shorten the duration of the stabilization step around the target pH value compared to the stabilization of a biomass that has not been impregnated.

[0113] The duration of the stabilization step can be from 15 minutes to 24 hours, preferably from 30 minutes to 6 hours, more preferably from 30 minutes to 3 hours.

[0114] This step can be carried out under the same temperature and pressure conditions as the pulping step.

[0115] During the stabilization step, a pH variation of less than 0.05 pH points / minute is typically observed, most often less than 0.02 pH points / minute.

[0116] The stabilization step can be considered complete when the pH variation is at most 0.5 pH points / hour, preferably at most 0.2 pH points / hour.

[0117] The impregnated lignocellulosic biomass suspended in step b) typically has a pH greater than 3, most often greater than 4. It may happen that after a stabilization period, the pH is lower or higher than the target value. A pH adjustment is then necessary when the pH has a value different from a desired target pH value, in particular to allow subsequent treatment of the suspension by enzymatic hydrolysis.

[0118] In this case, the stabilization step includes a pH adjustment sub-step, which can be implemented after an initial stabilization time, for example 30 minutes to 2 hours.

[0119] The pH can be adjusted by adding to the pulp (i) an acid or (ii) the unimpregnated lignocellulosic biomass or (iii) a base, preferably (i) an acid or (ii) the unimpregnated lignocellulosic biomass. The added unimpregnated lignocellulosic biomass thus corresponds to the lignocellulosic biomass used in the present invention before carrying out the optional preliminary preparation step and / or the impregnation step.

[0120] The pH can then be adjusted without adding a base or other chemical aid.

[0121] Preferably, the additions of acid or biomass are carried out with stirring.

[0122] The equipment used may include pH and flow rate measuring probes, and acid or unimpregnated lignocellulosic biomass may be added if necessary in amounts sufficient to lower or raise the pH to a target pH value, advantageously in a range of 4 to 6, and preferably in a range of 4.5 to 5.5.

[0123] The pH adjustment sub-step, when present, may include measuring the pH value of the pulp, comparing the measured value with the target value, and, when the measured value is different from the target value, adding a determined amount of an acid or unimpregnated lignocellulosic biomass or a base. When the measured value is identical to the target value, no addition is made. These steps can be repeated at regular time intervals until the pH value has reached the target value and is stable.

[0124] The predetermined quantities of acid or biomass or base can be previously determined by tests and / or estimations, depending on the pH of the pulp, the nature of the acid added and the nature of the biomass.

[0125] Typically, acid will be added to lower the pH and unimpregnated biomass or base, preferably unimpregnated biomass, will be added to raise the pH.

[0126] The acid used may be chosen from sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid. It may be added alone or dissolved in water. The acid may be the same acid as that present in the acid liquor or another acid, preferably the same.

[0127] It has surprisingly been found that the impregnation step a) according to the invention carried out prior to the pulping step b) allowed, during the stabilization step c), the use of a lower dose of acid than if the acid were added only after the pulping step b). In addition, the pH stabilization time, in particular around 5, during the adjustment step is shortened by the prior impregnation of the biomass with an acid liquor. A time saving of around 1 hour to 6 hours can be observed compared to a process not comprising an impregnation step according to the invention.

[0128] Process for producing sugar syrup

[0129] The preparation process according to the invention can be implemented in a sugar production process, which then comprises, following the aforementioned steps a) to c), a step d) of enzymatic hydrolysis followed by a step e) of recovery of the sugar syrup.

[0130] Step d) of enzymatic hydrolysis

[0131] The enzymatic hydrolysis step is carried out on the pulp obtained from step c) in order to convert the cellulose and hemicellulose it contains into a sugar syrup comprising fermentable sugars, in particular into a syrup comprising glucose.

[0132] In particular, the enzymatic hydrolysis step can be carried out directly on the pulp obtained in step c), without an intermediate step, in particular without heat treatment such as a steam explosion treatment.

[0133] The enzymatic hydrolysis step d) is typically carried out at a pH of 4 to 6, more precisely 4.5 to 5.5, a temperature of 45 to 60°C, and more precisely 50 to 55°C. The residence time can be from 12h to 72h and preferably from 24 to 48h.

[0134] In a particular embodiment of the invention, the enzymatic hydrolysis step d) may be carried out using an enzymatic cocktail such as a mixture of cellulolytic and / or hemicellulolytic enzymes, in particular a mixture of cellulases and hemicellulases. The cellulases may be chosen from the group consisting of endocellulases, exocellulases, β-glucosidases and mixtures thereof. The hemicellulases may be chosen from the group consisting of xylanases, xylosidases, endoglucanases, endoxylanases, endoxylanases and β-xylosidases, as well as certain arabinofuranosidases and esterases, and mixtures thereof.

[0135] Preferably, the mixture of cellulolytic and / or hemicellulolytic enzymes may be chosen from Ctech3® (Novozymes), Deltazym® (WeissBioTech), Isobake CX® or any other cellulolytic and / or hemicellulolytic cocktail, more preferably Ctech3®.

[0136] Typically, the hydrolysis step d) can be carried out using from 10 to 60 mg of enzymes per g of biomass, preferably from 10 to 60 mg of enzymes per g of cellulose, more preferably from 15 to 25 mg of enzymes per g of cellulose.

[0137] In a particular embodiment of the invention, the yield of the enzymatic hydrolysis may be 40% to 80%, typically 50% to 70%. The yield is calculated as the ratio of the amount of monomeric sugar released to the total amount initially available.

[0138] This enzymatic hydrolysis step d) allows the hydrolysis of sugars from both the cellulose and hemicellulose fractions.

[0139] In particular, it may be possible to adjust the pH of the pulp during hydrolysis step d), in particular by adding an acid, for example of the type described with reference to step d) or by adding non-impregnated biomass.

[0140] In one embodiment, during the enzymatic hydrolysis step, impregnated lignocellulosic biomass obtained in step a) can also be added to the pulp in a sequenced manner in order to increase the dry matter content of the hydrolyzed suspension and consequently the hydrolysis yield.

[0141] To this end, the following steps can be implemented:

[0142] (i) adding a determined quantity of impregnated lignocellulosic biomass obtained in step a), then,

[0143] (ii) stabilizing the pH at a value of 4 to 6, preferably 4.5 to 5.5, optionally comprising a pH adjustment,

[0144] (iii) addition of a determined quantity of enzymes.

[0145] The amount of impregnated lignocellulosic biomass added in step (i) may be determined based on the total dry matter content of the pulp so as to obtain in one or more times a reaction medium having a total dry matter content of at least 15% by mass, preferably at least 20% by mass. Advantageously, the additions are determined so that the pH does not vary outside the range of 4 to 6, preferably 4.5 to 5.5, and in particular based on the rheological characteristics of the pulp and the measurement of the torque of the agitation motor. The additions of impregnated biomass are preferably carried out in such a way as to guarantee efficient implementation of the agitation and homogeneity of the pulp

[0146] Following the addition of impregnated lignocellulosic biomass, the pH may vary slightly. It is then waited for to stabilize during step (ii), for example by mixing the reaction medium until the pH no longer varies (stabilizes). This stabilization is relatively short, for example 20 to 60 minutes and facilitated by the addition of acid-impregnated biomass. If the stabilized pH is not at a value of 4 to 6, preferably 4.5 to 5.5, then an adjustment of the pH can be provided, typically by adding acid or non-impregnated biomass.

[0147] Once the pH is stabilized, (iii) a determined quantity of enzymes is then added. The quantity of enzymes added can be determined according to the quantity of biomass added and its cellulose content. Typically, 10 to 60 mg of enzymes per g of biomass, preferably 10 to 60 mg of enzymes per g of cellulose, more preferably 15 to 25 mg of enzymes per g of cellulose, can be added.

[0148] Steps (i) to (iii) may be repeated the desired number of times, at determined time intervals, for example every two hours, in order to increase the total dry matter content of the reaction medium, for example to obtain a total dry matter content of 15 to 45% by mass, preferably 20 to 40% by mass, more preferably 20 to 30% by mass, which makes it possible to increase the final sugar concentration of the hydrolysate and to reduce the number and volume of tanks dedicated to enzymatic hydrolysis as well as the energy consumption for concentrating the sugars. The pulp impregnated at each addition may comprise at least 40% by mass of dry matter, preferably 60 to 95% by mass, more preferably 70 to 95% by mass, preferably 75 to 95% by mass, even more preferably 75 to 85% by mass.

[0149] Steps (i) to (iii) may advantageously be carried out after the start of the hydrolysis step, for example after a sufficient time for the enzymes present to liquefy the dry matter initially present. This time may be determined by a person skilled in the art depending on the enzymes, the hydrolysis conditions and the quantity of dry matter present at the start of the hydrolysis step. This implementation makes it possible to improve the rheological conditions during hydrolysis.

[0150] Alternatively, the pulp to be hydrolyzed can be hydrolyzed in one go (a single addition of pulp). The dry matter content of the reaction medium can then advantageously be 15 to 40%.

[0151] It is possible to carry out the first liquefaction stage and the ramp-up by adding material to a first reactor containing a suitable stirring system before transferring the pre-liquefied pulp to a new reactor with stirring adapted to these rheological conditions.

[0152] Step e) recovery of sugar syrup

[0153] This step allows the recovery of the sugar syrup formed during step d) of enzymatic hydrolysis.

[0154] Advantageously, the recovery step may comprise a clarification step, optionally followed by a purification step. The latter may optionally be followed by a concentration step.

[0155] The recovery step may comprise one or more clarification steps (solid / liquid separation), purification or concentration, in particular as described below. It may be carried out on the sugar syrup comprising fermentable sugars obtained at the end of step d), in particular on the syrup comprising glucose obtained at the end of step d).

[0156] The sugar syrup clarification step makes it possible to separate the solid residues from the liquid residues. A clarification step comprises, for example, a screening and / or filter press and / or decantation and / or centrifugation step. In one embodiment, the clarification step may comprise a screening step, a decantation step and a centrifugation step. In another embodiment, the clarification step may comprise a screening step followed by a filter press step.

[0157] The optional purification step allows the removal of residual suspended matter, such as some of the ions and / or salts, and the capture of certain soluble contaminants such as metal salts and ink residues, etc. The purification step includes filtration through an adsorbent, typically activated carbon. Non-limiting examples of activated carbon that can be used are Colorsorb 620 powder (Jacobi), BGX granular (Chemviron), CPW powder (Chemviron), CXV (old carbon).

[0158] The sugar syrup concentration step helps ensure the stability of the product by reducing the risk of contamination developing (especially bacterial) and facilitating its storage and transport. This step is preferably carried out using a vacuum evaporator, more preferably using a forced recirculation thin-film evaporator.

[0159] Use of the method according to the invention

[0160] The invention also relates to the use of the method according to the invention for producing bio-sourced molecules.

[0161] Non-limiting examples of bio-sourced molecules according to the invention are: sugars (monosaccharides), surfactants (alkyl polyglucosides), pigments, phenylpropanoids, organic acids (lactic acid, 3-hydroxypropionic acid, acetic acid, butyric acid, capric acid, citric acid, fumaric acid, malic acid, propionic acid, pyruvic acid, succinic acid, levulinic acid, 2,5-furandicarboxylic acid), alcohols (ethanol, 1,3-propanediol, 2,3-butanediol), isobutene and polyols (sorbitol, xylitol).

[0162] For example, the following molecules can be produced by biological conversion of glucose and have been described in the prior art: lactic acid (Xu et al., 2014, Yadav et al., 2020), acetic acid (Kondo et al., 1996), butyric acid (Fu et al., 2017), propionic acid (Wang et al., 2013), succinic acid (Ong et al., 2019), isopropanol (Ferreira dos Santos Vieira et al., 2020), isobutene (US20180057843, US9249430, WO2014086781), butanol (Cheng et al., 2019; Birgen et al., 2019) and farnesane (W02007139924, W02008045555).

[0163] The biosourced molecules according to the invention are preferably chosen from the group consisting of lactic acid, acetic acid, butyric acid, propionic acid, succinic acid, isopropanol and isobutene, even more preferably from the group consisting of lactic acid, acetic acid, butyric acid, propionic acid and isopropanol.

[0164] The invention also relates to the use of the method for producing a sugar syrup according to the invention for producing biofuels, preferably ethanol.

[0165] The invention also relates to a process for producing biofuels, in particular ethanol, comprising steps a) to e) of the process for producing a sugar syrup according to the invention and a subsequent fermentation step in order to convert the sugar syrup comprising fermentable sugars, in particular the syrup comprising glucose, recovered at the end of step e) into biofuels, in particular ethanol.

[0166] In a particular embodiment of the invention, the fermentation step may be carried out using yeasts and / or bacteria. The yeasts may be selected from the group consisting of yeasts of the genus Saccharomyces, Yarrowia and Leuconostoc. The bacteria may be selected from the group consisting of bacteria of the genus Bacillus, Lactobacillus, Acetobacter, Escherichia, Clostridium and Zymomonas. Preferably, the fermentation step is carried out using yeasts of the genus Saccharomyces, preferably Saccharomyces cerevisiae. The bacteria may be selected from Clostridium acetobutylicum or Escherichia coli.

[0167] The fermentation step according to the invention can be carried out using yeasts and / or bacteria capable of fermenting both hexoses and pentoses.

[0168] This fermentation step allows the conversion of at least the sugars from the cellulosic fraction, and preferentially the sugars from both the cellulosic and hemicellulosic fractions into biofuels, in particular ethanol.

[0169] In a particular embodiment of the invention, the fermentation step can be carried out in a reactor separate from that of the enzymatic hydrolysis step (SHF process) or simultaneously in the same reactor (SSF, S SCF, CBP processes), preferably in a reactor separate from that of the enzymatic hydrolysis step (SHF process).

[0170] If the fermentation step is carried out simultaneously in the same reactor as the enzymatic hydrolysis step, the process according to the invention does not include step e.

[0171] According to one embodiment, the method may comprise, after the fermentation step, a step of purification of the biosourced molecule or biofuel, by for example by distillation, particularly in the case of ethanol, the distillation step being preceded or not by a clarification step. Description of the drawings

[0172] [Fig.1] Figure 1 represents the evolution of the pH of the reaction medium as a function of the duration of pulping and stabilization measured during the test of example 1;

[0173] [Fig. 2] Figure 2 represents the evolution of the pH of the reaction medium as a function of time measured during the comparative test of example 3;

[0174] [Fig. 3] Figure 3 represents the evolution of the pH of the reaction medium as a function of time measured during the comparative test of example 4;

[0175] [Fig. 4] Figure 4 represents the evolution of the pH of the reaction medium as a function of time measured during the test of example 6.

[0176] [Fig. 5] Figure 5 represents the evolution of the pH of the reaction medium as a function of time measured during the test of example 8.

[0177] In the figures, the arrows BAE symbolize the addition of raw biomass (before impregnation and pulping) followed by an addition of acid in order to lower the pH into an optimal range and then, after a pH stabilization time, an addition of enzymes proportional to the quantity of raw biomass added, the arrows BI-E symbolize the addition of impregnated biomass as described in step a) of the invention followed after a pH stabilization time by an addition of enzymes proportional to the quantity of impregnated biomass added, the arrows E symbolize the addition of enzymes, P means that we are in the pulping step and S in the pH stabilization step, the solid rectangles symbolize the moment when the pH is stabilized, the horizontal dotted lines represent the optimal pH range for hydrolysis. Examples

[0178] The following examples are given for illustrative purposes only, and should not be construed as limiting the invention in any way.

[0179] Example 1 according to the invention - Impregnation test of a biomass of paper waste

[0180] The treated raw paper mill waste biomass contains 94.2% DM, including 21.7% DM ash, 59.7% DM cellulose and 6.6% DM hemicellulose. The amount of calcium expressed as CaO is 85.7 g CaO / kg DM.

[0181] The impregnation was carried out with a 26.6% by mass sulfuric acid solution at room temperature and ambient pressure for 5 minutes. The impregnation ratio is 138.6 g acid / kg DM.

[0182] After impregnation, the biomass is suspended (pulping step) at 10% DM at ambient pressure and 53 °C. Agitation is carried out using pitch blades at 400 rpm in a 10 L BioFlo reactor for 30 minutes and then agitation is maintained during the pH stabilization step. Figure 1 represents the evolution of pH as a function of the pulping and stabilization time. The vertical lines represent a stable pH zone obtained at the end of the stabilization step.

[0183] At the beginning of the pulping stage (mixture still not homogeneous) the pulp has a pH close to 1.5. During pulping (creation of a homogeneous pulp), the pH increases rapidly from 1.5 to 4 before increasing more moderately during the stabilization stage and stabilizing after 30 minutes at a pH, here in the optimal range for enzymatic hydrolysis.

[0184] It is observed that the pH remains stable around 5 during the 20 hours of enzymatic hydrolysis. Table 2 lists the quantities of products formed during hydrolysis. It is observed that the acid impregnation does not aim to hydrolyze the material. Indeed, at t = 0, after the pulping and pH stabilization step and before the addition of enzymes, the quantity of monomeric sugars is 0 g / L. At the end of hydrolysis, the glucose content of the suspension is 31.35 g / L for a total sugar content of 36.51 g / L.

[0185] [Table 2]

[0186] Example 2 - Use of different acid liquors

[0187] The raw biomass of paper waste used contains 94.2% DM, including 21.7% DM of ash, 59.7% DM of cellulose and 6.6% DM of hemicellulose. The amount of calcium expressed as CaO is 85.7 g CaO / kg DM.

[0188] Impregnation was carried out with different acid liquors followed by a pulping step. This test is implemented in a 10L BioFlo reactor. Impregnation and pulping are carried out at ambient pressure and temperature. The acid liquor is an aqueous solution of sulfuric acid.

[0189] The impregnation time is 5 minutes in manual mixing, then water is added and the mixture is mixed at 400 rpm for 20 minutes in the reactor.

[0190] The pulp has a dry matter content of 10% (taking into account only the DM of the paper). The stabilization stage is 1 to 2 hours depending on the tests.

[0191] The suspension thus stabilized is subjected to enzymatic hydrolysis at 20 mg enzymes / g of cellulose.

[0192] Table 3 lists the conditions and products obtained.

[0193] [Table 3] Table 3 ND: not determined

[0194] It can be noted that regardless of the mass percentage of the acid liquor used, this liquor does not act as a pretreatment (release of sugars) but as a preparation of the material to facilitate pH regulation, here in the optimal range for hydrolysis (4.5 < pH < 5.5) after 1 h of stabilization. The percentage of acid liquor varies according to the biomass and its buffering capacity but remains close to 130 g acid / kg DM.

[0195] Comparative example 3: pulping of biomass without prior impregnation followed by enzymatic hydrolysis with addition of non-impregnated biomass to increase the load

[0196] Raw paper mill waste biomass was pulped at 53°C, ambient pressure, for 30 minutes. The treated biomass was the same as that in Examples 1 and 2.

[0197] The initial pH of the pulp was above 8. In order to adjust the pH to a value of 4.5-5.5, sulfuric acid (26.6% by mass) was added after pulping and the pulp was left stirring for several hours to lower the pH to the optimal range.

[0198] After regulating the pH of the pulp, enzymatic hydrolysis is carried out by adding 20 mg of enzymes / g cellulose. In order to increase the material load in the reactor (initially 9.6% DM), raw biomass, not impregnated and before pulping, is added at regular intervals to obtain a final load in the reactor of 20% DM.

[0199] It should be noted in Figure 2 that with each addition of raw biomass (i.e. not acid-impregnated, and before pulping), the pH of the reactor increases due to the buffering capacity of the raw biomass and leaves the optimal pH range. This increase in pH degrades the efficiency of the enzymes present in the reactor and consequently an acid addition, homogenization and pH stabilization step must be implemented after each addition (symbolized by the arrow BAE).

[0200] In Figure 2, we see that the regulation time is very important upstream of the enzymatic hydrolysis to exhaust the buffering capacity of the biomass with large amounts of acid added (189.2 g pure acid / gMS). Figure 2 also shows that it is difficult to regulate the pH in the optimal range. In addition, with each addition of material the pH of the reaction medium increases again close to 6.

[0201] Table 4 shows the production of sugars during hydrolysis as a function of time and the amount of dry matter present. 0202] [Table 4]

[0203] Comparative example 4: pulping of biomass without prior impregnation followed by enzymatic hydrolysis with addition of non-impregnated biomass to increase the load

[0204] This example was carried out in a similar manner to Example 3, with the same biomass, but, during T hydrolysis, the raw biomass (e.g., unimpregnated and before pulping) is introduced in a sequenced manner until a DM content of 25% is obtained.

[0205] The results are summarized in Table 5 and Figure 3. The addition of raw, unimpregnated, pre-pulping biomass during hydrolysis is represented by arrows marked B in Figure 3. As in Comparative Example s, the pH is difficult to regulate during the pulping step, and varies significantly with each addition of raw, unimpregnated, pre-pulping biomass during hydrolysis. In addition, as in Comparative Example 3, with each addition of raw biomass, the pH increases and requires the addition of acid and homogenization and stabilization of the pH before the addition of enzymes (steps marked BAE on the graph).

[0206] [Table 5]

[0207] Example 5 according to the invention: pulping of biomass with prior impregnation followed by enzymatic hydrolysis with addition of impregnated biomass to increase the load

[0208] Example 3 is repeated by replacing the raw paper waste biomass with paper waste biomass impregnated according to step a) of the present invention. The impregnation was carried out with sulfuric acid with an impregnation ratio of 129 g of pure acid / kgws.

[0209] Pulping of the impregnated biomass is then carried out with a shortened pH stabilization period by using impregnated biomass that did not require additional addition of acid liquor. The impregnated and stabilized biomass pulp is then subjected to enzymatic hydrolysis. During hydrolysis, impregnated biomass at 129 g acid / kg DM is added sequentially to the reactor until a DM content of 20% by mass is obtained. It can be noted that the amount of acid used per kg DM is significantly lower than that used in the case of comparative examples 3 and 4 which used raw, unimpregnated biomass before pulping. Furthermore, following an addition of impregnated biomass, no additional dose of acid was added to the reactor between each addition of biomass, which reduces the pH stabilization time between additions and guarantees an optimal pH range for the operation of the enzymes.

[0210] The results are collected in Table 6.

[0211] [Table 6] 0212] Example 6 according to the invention: pulping of biomass with prior impregnation followed by enzymatic hydrolysis

[0213] This example was carried out in a similar manner to Example 5, but during hydrolysis, the previously impregnated biomass is introduced in a sequenced manner until a DM content of 30% is obtained. It is noted that the addition of impregnated biomass makes it possible to reduce the quantity of acid used but also to ensure that the pH remains in an optimal range with each addition of feedstock. The sugar yields obtained are therefore higher than those of Comparative Examples 3 and 4.

[0214] The results are summarized in Table 7 and Figure 4. In Figure 4, the letters P and S represent the pulping and stabilization steps. The arrow BI-E represents the additions of impregnated biomass followed by the addition of enzymes.

[0215] [Table 7]

[0216] Example 7 according to the invention: use of acid liquors comprising different types of acids

[0217] This example was carried out in a similar manner to Example 5 but with acids of different types, namely sulfuric acid, phosphoric acid, nitric acid and citric acid.

[0218]

[0219] The table below shows the amount of acid required during the impregnation step to achieve a target pH value of 5 during the stabilization step c).

[0220] [Table 8] 0221] Regardless of the type of acid used, it has been found that pulping biomass with prior impregnation followed by enzymatic hydrolysis makes it possible to reduce its quantity as well as the duration of pH stabilization.

[0222] Example 8 - Impregnation test of a biomass of paper waste for a period of 24 hours

[0223] The treated raw paper mill waste biomass contains 94.2% DM, including 21.7% DM ash, 59.7% DM cellulose and 6.6% DM hemicellulose. The amount of calcium expressed as CaO is 85.7 g CaO / kg DM.

[0224] The impregnation was carried out with a 37% by mass sulfuric acid solution at room temperature and ambient pressure without stirring for 24 hours. The impregnation ratio is 140.8 g pure acid / kg DM.

[0225] After impregnation, the biomass is suspended (pulping step) at 10% DM at ambient pressure and 53 °C. Agitation is carried out using pitch blades at 400 rpm in a 10 L BioFlo reactor for 20 minutes for the pulping step and is maintained for an additional 50 minutes for the pH stabilization step. Figure 5 represents the evolution of pH as a function of pulping and stabilization time. The horizontal lines represent a stable pH zone obtained at the end of the stabilization step.

[0226] At the beginning of the pulping stage (still inhomogeneous mixture), the pulp has a pH of 2.8 which is higher than the pH observed when a shorter impregnation time is implemented. During pulping (creation of a homogeneous pulp), the pH increases rapidly from 2.8 to 4.2 before increasing more moderately during the stabilization stage and stabilizing at a pH of 4.95, here in the optimal range for enzymatic hydrolysis.

[0227] It is observed that the pH remains stable around 5 during the enzymatic hydrolysis. It is also observed that the acid impregnation does not aim to hydrolyze the material. Indeed, at t = 0, after the pulping and pH stabilization step and before the addition of the enzymes, the quantity of monomeric sugars is 0.2 g / L. At the end of the hydrolysis, the glucose content of the suspension is 27.1 g / L for a total sugar content of 32.3 g / L. 0228] [Table 9] References

[0229] Nizami et al., Bioresource Technol. Rev. 2017, 241, 1101–1117; Xu et al. Bioresource Technol. 2014, 153, 23–29; Yadav et al. Bioresource Technol. 2020, 11, 100423; According to Kondo et al. J. Ferment. Technol. 1996, 81(1), 42-46; Fu et al. Bioresource Technol. Rev. 2017, 234, 389–396; Wang et al. Bioresource Technol. 2013, 137, 116–123; Ong et al., Biochem Eng. J. 2019, 148, 108–115; Ferreira dos Santos Vieira et al. Fuel 2020, 263, 116708; Cheng et al. Bioresource Technol. Rev. 2019, 284, 415–423; Birgen et al. Biochem Eng. J. 2019, 147, 110–117.

Claims

Claims

1. A process for preparing a lignocellulosic biomass pulp comprising papermaking waste, in particular printable paper, printed paper, packaging board or cardboard, said process comprising the following steps: a) a step of impregnating said lignocellulosic biomass with an acid liquor, during which all of the added acid liquor is absorbed by said lignocellulosic biomass and the impregnated lignocellulosic biomass resulting from the impregnation has a total dry matter content lower than the content of the lignocellulosic biomass before carrying out step a), b) a pulping step during which said impregnated lignocellulosic biomass from step a) is suspended in water and a pulp having a total dry matter content of 5% to 40% by mass, said impregnated lignocellulosic biomass from step a) being sent directly to step b) of pulping without any other intermediate step, c) a step of stabilizing the pH of the pulp from step b) to a target value, this target value being a pH range of 4 to 6 or being included in this range.

2. Preparation process according to claim 1, characterized in that said lignocellulosic biomass before impregnation has at least one of the following characteristics: a total dry matter content of 70 to 100% by mass, in particular 85 to 96%, a calcium content expressed as CaO of 60 to 200 g CaO per kg of dry matter of lignocellulosic biomass, an ash content of 15 to 25% by mass.

3. Preparation process according to claim 1 or 2, characterized in that the impregnation step a) comprises at least one of the following characteristics: the acid liquor comprises an acid in an amount of 10 to 100% by mass, preferably 10 to 45% by mass, more preferably 20 to 37% by mass, the acid liquor comprises an acid chosen from sulfuric acid, phosphoric acid, hydrochloric acid and nitric acid, an impregnation ratio of 30 to 177 g of pure acid per kg of dry matter, an impregnation time of 1 to 60 minutes, preferably 3 to 30 minutes, an implementation at a temperature of 10 to 80 °C, preferably from 10 to 60°C, more preferably from 15 to 55°C, more preferably at room temperature, an implementation at a pressure of 0 to 2 bar, preferably from 0 to 1 bar, the impregnated lignocellulosic biomass obtained at the end of this step a) a total dry matter content of 40 to 95% by mass, preferably from 60 to 95% by mass, more preferably between 70 and 95%, even more preferably from 75 to 95% by mass, even more preferably from 75 to 85% by mass.

4. Preparation process according to any one of claims 1 to 3, characterized in that the pulping step b) comprises at least one of the following characteristics: an implementation for a duration of 5 to 180 minutes, preferably 20 to 60 minutes, an implementation at a temperature of 10 to 80°C, preferably 37 to 55°C, an implementation at a pressure of 0 to 2 bar, preferably 0 to 1 bar, an implementation with stirring, the pulp obtained has a pH of 2 to 5, preferably 3 to 5, more preferably 3.5 to 4.

5.

5. Preparation process according to any one of claims 1 to 4, characterized in that step c) of stabilizing the pH comprises at least one of the following characteristics: the target pH value is a pH range of 4.5 to 5.5, or is included in this range, an implementation at a temperature of 10 to 80 °C, preferably 37 to 55 °C, an implementation at a pressure of 0 to 2 bar, preferably 0 to 1 bar, - an implementation with stirring, a stabilization time of 15 minutes to 24 hours, preferably 30 minutes to 6 hours, more preferably 30 minutes to 3 hours. a sub-step of adjusting the pH of the pulp of step c) to a target value, in which the pH is adjusted to said target value by adding to the pulp (i) an acid or (ii) said non-impregnated lignocellulosic biomass, or (iii) a base, preferably (i) an acid or (ii) said non-impregnated lignocellulosic biomass.

6. Preparation process according to any one of claims 1 to 5, characterized in that it further comprises, upstream of step a) impregnation, a preliminary stage of preparation of said lignocellulosic biomass by grinding, stone removal, iron removal, refining and / or thermal hygienization.

7. A method for producing a sugar syrup from lignocellulosic biomass comprising papermaking waste, in particular printable paper, printed paper, packaging cardboard or cardboard, said method comprising the following steps: implementing the method for preparing a pulp from said biomass according to any one of claims 1 to 6, followed by: d) a step of enzymatic hydrolysis of the stabilized pulp obtained at the end of step c) of the preparation method, in which the cellulose and hemicellulose it contains are converted into a sugar syrup comprising fermentable sugars, and e) a step of recovering the sugar syrup comprising fermentable sugars obtained at the end of step d).

8. Process for producing a sugar syrup according to claim 7, characterized in that the enzymatic hydrolysis step d) is carried out by sequentially adding impregnated biomass obtained at the end of step a) of the preparation process.

9. Process for producing a sugar syrup according to claim 7 or 8, characterized in that during step d), (i) a determined quantity of impregnated lignocellulosic biomass obtained at the end of step a) of the preparation process is added, then, (ii) optionally the pH is adjusted to a value of 4 to 6, preferably 4.5 to 5.5, and, after stabilization of the pH, (iii) a determined quantity of enzymes is added.

10. Process for producing a sugar syrup according to any one of claims 7 to 9, characterized in that the enzymatic hydrolysis step d) is carried out by means of a mixture of cellulolytic and / or hemicellulolytic enzymes, in particular a mixture of cellulases and hemicellulases.

11. Use of the method according to any one of claims 7 to 10 for producing bio-sourced molecules, in particular bio-sourced molecules chosen from surfactants, in particular alkyl polyglucosides, pigments, phenylpropanoids, organic acids, such as lactic acid, 3-hydroxypropionic acid, acetic acid, butyric acid, capric acid, citric acid, fumaric acid, malic acid, propionic acid, pyruvic acid, succinic acid, levulinic acid, 2,5-furandicarboxylic acid, alcohols, in particular C2-C4 alcohols, isobutene and polyols.

12. A process for producing biofuels, in particular ethanol, comprising the steps of the process according to any one of claims 7 to 10 and a subsequent fermentation step in order to convert the sugar syrup comprising fermentable sugars recovered at the end of step e) into biofuels, in particular ethanol.

13. Process for the production of biofuels according to claim 12, characterized in that the fermentation step is carried out using yeasts, in particular of the genus Saccharomyces, preferably Saccharomyces cerevisiae, and / or bacteria, in particular Clostridium acetobutylicum or Escherichia coli.

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