METHOD FOR TREATING LIGNOCELLULOSIC BIOMASS

Description

1 / 40 METHOD FOR TREATING LIGNOCELLULOSIC BIOMASS Technical field

[0001] The present invention relates to a method for treating lignocellulosic biomass to produce so-called second-generation (2G) sugar juices. These sugar juices can be used to produce other products via biochemical means, in particular via fermentation (e.g., alcohols such as ethanol, butanol), or other molecules, e.g., solvents such as acetone, etc.). State of the art

[0002] Lignocellulosic biomass represents one of the most abundant renewable resources on Earth. The substrates considered are very varied, including both woody substrates, such as different types of wood (deciduous and coniferous species), by-products derived from agriculture (wheat straw, corn stalks, etc.) or other agri-food industries, paper industries, lignocellulosic waste, etc.

[0003] The method for treating lignocellulosic biomass generally comprises - a pre-treatment of biomass by cooking, possibly associated with steam explosion and generally preceded by impregnation of the biomass with an acidic, basic, neutral or oxidizing liquor, - an enzymatic hydrolysis, leading to the production of sugar juices, generally based on C5 and C6 sugars (i.e., sugars with 5 or 6 carbon atoms), - and eventually the fermentation of these sugars with yeast to convert them into ethanol-type alcohol.

[0004] The method also includes steps for separating and / or purifying the desired final product (sugar, alcohol, solvent, etc.).

[0005] Lignocellulosic biomass is composed of three polymers Petition 870250089691, dated 02 / 10 / 2025, page 8 / 61 2 / 40 main components: cellulose (35 to 50% by weight), which is a polysaccharide essentially composed of hexoses; Hemicellulose (20 to 40% by weight), which is a polysaccharide essentially composed of pentoses; and lignin (10 to 30% by weight), which is a polymer with a complex structure and high molecular weight, composed of aromatic alcohols linked by ether bonds. These different molecules are responsible for intrinsic properties of the plant cell wall and are organized in a complex imbrication.

[0006] Among the three basic polymers that make up lignocellulosic biomass, cellulose and hemicellulose are the ones that make it possible to produce 2G sugar juices.

[0007] Most of the time, hemicellulose is mostly broken down into sugar during pretreatment, and cellulose is converted into sugar (glucose) by enzymatic hydrolysis. However, access to crude cellulose remains difficult for enzymes, resulting in the need for pretreatment. This pretreatment allows modifying the physicochemical properties of lignocellulosic biomass to improve the accessibility of cellulose to enzymes and its reactivity to enzymatic hydrolysis.

[0008] Several technologies are of interest to the invention for carrying out this pretreatment, which will be grouped below under the generic name of "cooking": acid cooking, alkaline cooking, autohydrolysis cooking, steam explosion, the so-called "organosolv pulping" methods according to the known English term (or organic solvent treatment in French). This last method involves a pretreatment in the presence of one or more organic solvents and usually water. The solvent can be an alcohol (ethanol), an acid such as acetic acid, formic acid or even acetone. The "organosolv pulping" methods lead to at least partial solubilization of lignin, a partial solubilization of hemicelluloses. In the end, there are Petition 870250089691, dated 02 / 10 / 2025, page 9 / 61 3 / 40 then two streams: the substrate pre-treated with residual cellulose, hemicellulose and lignin, and the solvent phase, which contains solubilized lignin and some of the hemicellulose. In general, there is a solvent regeneration step that allows the extraction of a lignin stream. Some "organosolv pulping" treatments (mainly with ethanol) are associated with the addition of a strong acid (such as H2SO4). One can also consider contacting the biomass with the solvent in an impregnation reactor before the cooking phase or contacting the biomass with the acid catalyst before performing an "organosolv pulping" cooking process.

[0009] Different configurations are reported, for example, in the document “Production of bioethanol from lignocellulosic materials via the biochemical pathway: A review, M. Balat, Energy Conversion and Management 52 (2011) 858-875, or also in the document “Bioethanol production from agricultural wastes: an overview ”, N. Sarkar, S. Kumar Ghosh, S. Bannerjee, K. Aikat, Energia Renovável 37 (2012) 19-27.

[0010] One of the most effective pretreatments is steam explosion, especially under acidic conditions, which promotes almost complete hydrolysis of hemicellulose and a significant improvement in the accessibility and reactivity of cellulose to enzymes. This pretreatment may be preceded by other treatment(s).

[0011] From the moment the treatment requires a pressure step (impregnation, pre-treatment of the cooking type or other), it is necessary to resort to means of introducing the solid biomass that are compatible with these pressure steps. This is the case, for example, of compression screws, the embodiment of which is described in US patent 4,599,138.

[0012] Patent FR 3 075 203 describes a method of impregnating biomass with an acid liquor, followed by cooking and steam explosion of the impregnated biomass, with an adjustment of the acid liquor acidity and recycling thereof. Patent FR 3 075 201 also describes Petition 870250089691, dated 02 / 10 / 2025, page 10 / 61 4 / 40 sees a method for pretreating biomass by acid impregnation, followed by steam explosion, and also washing the reactor feed media and recycling the wash water for the method.

[0013] These different methods, starting from lignocellulosic biomass, generate lignin-based solid residues, especially after enzymatic hydrolysis and / or after fermentation, particularly if the intention is to convert sugars into alcohol. These solid residues, here called "unconverted solid residue" or "lignin cake," are rich in lignin that has not reacted or has reacted little to the action of the enzymes used for biomass hydrolysis, generally cellulases and hemicellulases. These woody residues can be used, especially as fuel, or incorporated as filler in resinous or bituminous products, for example. However, these unconverted residues consist (in addition to a certain amount of water) only of lignin: they may also contain hemicellulose and / or cellulose that did not react in the hydrolysis.Discarding the waste from the biomass conversion method means losing the unreacted polymeric sugar fractions, which interferes with the yield of biomass conversion into sugar (or alcohol).

[0014] The reuse of this type of solid waste in biomass treatment methods has already been proposed: patent EP 2 516 661 proposes a method for biomass treatment with a pretreatment of the biomass in an alkaline medium, enzymatic hydrolysis, fermentation of the resulting hydrolysate to obtain a fermentation must containing an alcohol, separation / purification of the alcohol, and separation of the waste cake. This waste cake is sent to a separate reactor for cellulose regeneration, where the cake is mixed with an alkaline solution and heated before being recycled downstream of the pretreatment. This solution is interesting because it opts to recover the Petition 870250089691, dated 02 / 10 / 2025, page 11 / 61 5 / 40 of the remaining cellulose present in the wood cake is reintegrated into the process to increase the overall biomass conversion yield. On the other hand, it establishes a separate treatment of this cake with a dedicated additional reactor that will perform an alkaline cooking of the cake before recycling it. This increases the installation and operating costs of the method as a whole, increasing the complexity of its implementation.

[0015] Another solution was proposed by patent EP 2 430 171, quite similar to the previous one, but providing for a cooking of the woody residue that is no longer alkaline, but acidic, with the same disadvantages.

[0016] Solutions involving the reuse of waste are interesting, but they are still difficult to implement.

[0017] Furthermore, pretreatment reactors using cooking methods, especially those with steam explosion, face problems of progressive fouling, with deposits of solid residues on the walls accumulating and which can gradually lead to operational problems (clogging of reactor inlets / outlets, greater difficulty in circulating biomass, decreased efficiency of the reactor as a whole). Solutions have been suggested, particularly carrying out cleanings with production interruption, emptying the reactor and scraping the fouled walls.

[0018] Thus, patent WO2020 / 126916 proposed a cleaning technique using a basic aqueous solution and steam injection.

[0019] Other solutions have been proposed that perform cleaning without halting production, which is industrially more attractive. These consist mainly of the technique described in patents WO 2020 / 126918 and WO 2020 / 126917, which propose cleaning the pretreatment reactor with a basic aqueous solution in the presence of biomass, effectively producing an impregnated biomass that is then pre-treated. Petition 870250089691, dated 02 / 10 / 2025, page 12 / 61 6 / 40 treated biomass is basic, which can then continue with enzymatic hydrolysis conversion treatment. This basic pre-treated biomass, however, is less reactive to enzymatic hydrolysis than the impregnated and pre-treated biomass in an acidic or neutral medium, which is produced outside the cleaning phase. This will tend to mix the two types of pre-treated biomass before proceeding with the conversion. Therefore, this technique is interesting, but it can still be improved in order to clean the pre-treatment reactor and minimize the impact on the efficiency of the pre-treatment performed on the biomass during cleaning.

[0020] The invention aims to improve the treatment of lignocellulosic biomass with a view to its conversion into sugar(s) or alcohol. More specifically, the objective is to increase the biomass conversion yield or decrease the energy consumption of the treatment or to make better use of the possible by-products of the treatment. Summary of the invention

[0021] The invention has as its first object a method for the treatment of lignocellulosic biomass comprising: b) an acid or neutral pretreatment step of the biomass previously carried out under acidic or neutral pH conditions in a pretreatment reactor to produce an acid or neutral pretreated biomass, wherein said step b) is operated alternately with b') a basic pretreatment step of the biomass previously carried out under acidic, neutral or basic conditions, with a possible addition of base, to produce a basic pretreated biomass, and then c) an enzymatic hydrolysis step in a hydrolysis reactor (16) of the acid or neutral pretreated biomass resulting from step b) and / or the basic pretreated biomass resulting from step b'), to obtain a hydrolyzed biomass, Petition 870250089691, dated 02 / 10 / 2025, page 13 / 61 7 / 40 d) a solid / liquid separation step of the hydrolyzed biomass resulting from step c) in the form of sugar(s) or a solid / liquid separation step of the hydrolyzed biomass in the form of sugar(s) resulting from step c) and then treated in one or more additional steps subsequent to step c) of enzymatic hydrolysis, to obtain a separated juice and an unconverted solid residue, (e) a recycling step for at least part of the aforementioned unconverted solid waste obtained in step (d) towards the basic pre-treatment step (b').

[0022] In the sense of the present invention, unconverted “solid” residue means a residue containing at least 20% by weight of solids, in particular at least 30 or 35% by weight of solids. This proportion of solids and soluble compounds can be evaluated in a sample of the product by measuring its Dry Matter content (acronym DM), which is measured in accordance with ASTM E1756 08(2015) “Standard Test Method for Determination of Total Solids in Biomass”.

[0023] The invention therefore combines two features: - On one hand, it proposes a pretreatment that alternates between acidic and neutral pretreatments for the biomass, which allows obtaining pretreated biomasses that are quite reactive to enzymatic hydrolysis following the pretreatment, and basic pretreatments, which aim to clean the pretreatment reactor, but continue to produce a basic pretreated biomass, which is somewhat less reactive (in this way, the cleaning of the reactor is continuous, without the need to interrupt the pretreatment). On the other hand, it proposes recycling towards the basic biomass pretreatment stage of all or part of the unconverted solid waste obtained by solid / liquid separation, either after enzymatic hydrolysis (sugar juice separation) or after fermentation (alcoholic juice separation), specifically introducing it... Petition 870250089691, dated 02 / 10 / 2025, page 14 / 61 8 / 40 mind in the basic biomass pre-treatment stage.

[0024] In fact, it is surprising to realize that this unconverted solid residue had very interesting abrasive properties, and that the use of this residue during basic pretreatment allowed the walls of the pretreatment reactor to be cleaned at least as efficiently, and even more efficiently, than simply with biomass.

[0025] What is also surprising is that the addition of this residue to the rest of the biomass under treatment did not in fact cause any problems in the operation of the pre-treatment tools: it did not interfere with the proper operation of the devices used, although there was concern that the addition of this residue, with a texture quite different from that of the biomass, could cause problems of fouling of the devices, problems of residue being carried from one device to another or within a device, etc. None of this occurred.

[0026] And this combination is very advantageous and synergistic between the two characteristics. In effect, the use of this residue to “replace” all or part of the biomass during basic pretreatment allows saving biomass during basic pretreatment, having more biomass available for acid pretreatment, with the same total mass of biomass to be converted. The efficiency of periodic cleaning in basic medium of the pretreatment reactor is maintained, producing less basic, less reactive pretreated biomass, and it is even possible to consider the complete replacement of biomass by this residue during basic cleanings, but ultimately increasing the conversion yield of the biomass to be converted.

[0027] In addition, this unconverted solid residue is reused in the production line, which allows, if necessary, the extraction of any reactive compounds still attached to the lignin, for the following stages. Petition 870250089691, dated 02 / 10 / 2025, page 15 / 61 9 / 40 following the biomass conversion method, which also contributes to increasing the biomass conversion yield.

[0028] The unconverted solid residue thus recycled is gradually enriched with lignin: in effect, the final unconverted residue obtained at the end of production is poor in cellulose / hemicellulose that was bound to the lignin, and rich in lignin when compared to a residue that was not recycled according to the invention: this final residue therefore has a higher calorific value, which makes it more efficient as fuel to generate heat through a combustion step of this final residue. The heat produced can be used in the biomass conversion method, in one or more steps where heating fluids is necessary (e.g., the impregnation liquor), a reactor (e.g., cooking outside of pretreatment) or a reboiler of a distillation column (e.g., to purify an alcohol obtained by fermentation). Furthermore, the final unconverted residue can be valorized outside the biomass conversion line for external use.

[0029] It was thus surprisingly found that the reintroduction of this residue into the impregnation or cooking device, with the biomass undergoing treatment, allowed: - to extract at least part of the cellulose and / or hemicellulose retained in the residue, the enzymatic hydrolysis reaction did not allow for the complete conversion of these compounds, - and convert at least part of them, making them follow the path of "fresh" biomass again in its pre-treatment stages and then enzymatic hydrolysis, which, in fact, results in an increase in the production of sugars (or alcohol) from the method.

[0030] As indicated above, step b') which produces the basic pretreated biomass may, in fact, be a cleaning step for the impregnation reactor. From time to time, pretreatment in medium Petition 870250089691, dated 02 / 10 / 2025, page 16 / 61 10 / 40 neutral or acidic will be interrupted, in particular, and the biomass will be brought into contact with an alkaline medium to allow the detachment and purging of encrusted residues on the walls of the pretreatment reactor, both by the effect of the alkaline medium capable of dissolving / detaching the residues and by the mechanical effect of friction of the biomass and, according to the invention, of the solid residue not converted in the stages subsequent to pretreatment.

[0031] Preferably, pretreatment steps b) and b') include cooking the biomass, particularly accompanied by steam explosion of said biomass.

[0032] Advantageously, in step e) towards step b') of basic pretreatment, a quantity of unconverted solid waste corresponding to at least 10%, particularly at least 20%, preferably at least 30% or 40% by weight of the total waste and biomass supply to said pretreatment reactor during said step b') can be recycled. Still more waste can be used to “replace” biomass, or even to completely replace biomass in this step b').

[0033] Preferably, the acid or neutral pretreatment step b) and / or the basic pretreatment step b') includes a prior impregnation step a) and / or a'), particularly in an impregnation reactor, of the biomass with an acidic, neutral or basic aqueous solution.

[0034] In this case, in a first embodiment, the basic pretreatment step b') includes a prior impregnation step a') of the biomass with an acidic, neutral or basic aqueous solution, particularly in an impregnation reactor, and in step e) at least part of the unconverted solid residue is recycled towards the pretreatment step b') by introducing said residue into the impregnation reactor during the impregnation step a'). This embodiment is interesting because it facilitates the extraction of minor reactive compounds present. Petition 870250089691, dated 02 / 10 / 2025, page 17 / 61 11 / 40 in the unconverted solid residue that would be trapped. However, the presence of this residue in the impregnation reactor can lead to additional consumption of the impregnation liquor.

[0035] In a second embodiment of the invention, (with or without prior impregnation in an impregnation device) in step e) at least part of the unconverted solid waste can be recycled towards step b') of pretreatment, by introducing said waste into the pretreatment reactor, particularly of the cooking type, especially with steam explosion. This embodiment is interesting since the solid waste is loaded into the pretreatment reactor by the biomass, generally previously impregnated with the impregnation liquor, and because it does not involve additional consumption of the impregnation liquor.

[0036] Preferably, step a') of biomass impregnation and step b') of basic pre-treatment of the impregnated biomass are carried out in reactors, each equipped with a biomass feeding device, and step e) of recycling the unconverted solid residue, introducing at least part of said residue with the biomass undergoing treatment, is carried out in at least one of said feeding devices. "Undergoing treatment" means that the residue is introduced before the biomass or with the biomass during at least part of the time it feeds the reactor in question, or after the reactor is fed with biomass during its operation.

[0037] At least one of the feeding devices may therefore be a feeding screw, particularly at least partly conical, with a casing fitted with a cage with openings that allow the extraction of the solid-liquid residue from the biomass and possibly the circulation of a washing fluid. This compression screw, as is known, gives rise to a hermetic biomass plug in the downstream portion of the screw, creating compression on the Petition 870250089691, dated 02 / 10 / 2025, page 18 / 61 12 / 40 biomass, which translates to a pressure difference between the biomass inlet and the biomass outlet of the screw. However, any other known device can be used. For the impregnation stage, it is possible to use a continuous or batch reactor, or other means besides a dedicated reactor, in particular a conveyor belt, which is sprayed with liquor, etc.

[0038] Advantageously, the basic pretreatment step b') comprises the addition of base to the pretreatment reactor: in this case, the biomass is brought into contact with a basic medium not during the pre-impregnation, for example, but during the cooking pretreatment itself. The addition of base to the pretreatment reactor is compatible with the pre-impregnation of the biomass with an acidic, neutral or basic impregnation liquor: the addition of base is adjusted according to the acidity / basicity of the biomass feeding the pretreatment reactor.

[0039] According to one embodiment, the method according to the invention aims at the production of sugar juice only, and the separation step d) is operated on the sugar juice at the outlet of the enzymatic hydrolysis.

[0040] According to another embodiment, the method aims to transform all or part of the sugar juice obtained by enzymatic hydrolysis. Therefore, it may also include: - a step f) of fermentation of the hydrolyzed biomass in the form of sugar(s) to obtain a fermented biomass containing at least one alcohol, wherein the step d) of solid / liquid separation is operated on said fermented biomass.

[0041] In this last embodiment, according to the invention, the recycling of the unconverted residue can be carried out at the end of enzymatic hydrolysis and / or at the end of fermentation:

[0042] The enzymatic hydrolysis (c) and fermentation (f) steps can be carried out simultaneously in the pretreated biomass; this is therefore a case of SSF, an acronym for the English term "Simultaneous". Petition 870250089691, dated 02 / 10 / 2025, page 19 / 61 13 / 40 Saccharification and Fermentation” or SSCF is the acronym for the English term “Simultaneous Saccharification and Co-Fermentation”. They can also be carried out sequentially, particularly in separate reactors.

[0043] The method according to the invention may further comprise:

[0044] - a separation or purification step (g), in particular distillation, of fermented biomass, wherein the solid / liquid separation step (d) is carried out before or after the said separation or purification step (g).

[0045] Performing separation d) before step g), when step g) is a distillation, is advantageous because it avoids introducing a liquid phase containing this residue, which could cause fouling in the column or at least disrupt the operation.

[0046] But it may also be interesting to operate separation d) according to the invention after or during the concentration / purification step of the hydrolysate or fermentation wine, since the solid residue may contain a fraction of sugars or alcohol, and passing it to the concentration / purification step would make it possible to extract at least part of that sugar or alcohol fraction attached to the solid residue.

[0047] As indicated above, the method according to the invention may also include: - a step h) of combustion of the final unconverted solid residue obtained at the end of the biomass treatment, the heat produced from which is used in a step of said method that requires heating, particularly the heating of a fluid, especially in the cooking step b) or b') or a distillation separation step g).

[0048] The final residue obtained with the invention has greater power Petition 870250089691, dated 02 / 10 / 2025, page 20 / 61 14 / 40 calorific value due to the lower content of cellulose / hemicellulose, which are polymeric sugars with low calorific value, unlike lignin.

[0049] Optionally, step h) of combustion may be preceded by step i) of drying the residue, in particular so that the residue reaches a water content below a certain limit, for example less than or equal to 40% by weight, in particular less than or equal to 30% by weight.

[0050] Step d) of solid / liquid separation can be carried out by filtration, mainly using a pressing or draining device, such as a filter press or a vacuum filter, a belt filter, a belt press or a centrifugal, decanting, centrifugal dryer or a combination of different devices.

[0051] The unconverted solid residue obtained in step d) of solid / liquid separation generally contains, in addition to water, a main compound in the form of lignin, and minor compounds including cellulose and / or hemicellulose and possibly one or more ethanol-type alcohols when solid / liquid separation d) is carried out after a fermentation step f).

[0052] The unconverted solid residue obtained in step d) of solid / liquid separation may contain, for example, between 40 and 70% by weight of water, in particular between 50 and 60% by weight of water, between 2 and 35% of cellulose DM, in particular between 5 and 20% of cellulose DM, and between 0 and 15% of hemicellulose DM, in particular between 1 and 10% of hemicellulose DM. In addition, it may contain other minor compounds, such as mineral compounds (the measurement of which can be done by analyzing the post-combustion ash).

[0053] The different levels of lignin, cellulose and hemicellulose can in fact vary, mainly depending on the type of biomass used and its reactivity during enzymatic hydrolysis.

[0054] Stage e) of recycling non-converted solid waste Petition 870250089691, dated 02 / 10 / 2025, page 21 / 61 15 / 40 reduces the content of at least one of the minor compounds cellulose and hemicellulose in the final solid residue obtained after biomass treatment, and increases its calorific value, which is beneficial both for biomass conversion yield and for the thermal integration of the method.

[0055] The dry basis composition of the final solid residue obtained at the end of biomass treatment generally contains lignin as the main compound and less than 20% cellulose DM and less than 8% hemicellulose DM.

[0056] The treatment method targeted by the invention can convert lignocellulosic biomass into sugar juice, especially C5 and C6 juices, after enzymatic hydrolysis, or into alcohol(s), mainly ethanol, after fermentation of said sugar juice.

[0057] The invention also relates to the installation for implementing the method described above.

[0058] Furthermore, the invention relates to an installation for implementing the method described above, comprising: a) an impregnation device, particularly an impregnation reactor, for biomass with an aqueous solution, in particular an acidic or neutral solution. b) a pretreatment reactor for cooking the impregnated biomass from the impregnation device, wherein said cooking is possibly accompanied by steam explosion to obtain a pretreated biomass, and said reactor is equipped with means for injecting a basic aqueous solution, c) an enzymatic hydrolysis reactor for pre-treated biomass to obtain hydrolyzed biomass, such that the said installation also includes d) a solid / liquid separation device for hydrolyzed biomass or for biomass that has been hydrolyzed and then treated in one or more Petition 870250089691, dated 02 / 10 / 2025, page 22 / 61 16 / 40 reactors or additional devices arranged downstream of the reactor c) enzymatic hydrolysis to obtain an unconverted solid residue, (e) means for recycling at least part of the said solid waste not converted in the reactor (a) impregnation towards the impregnation reactor and / or towards the pretreatment reactor when the pretreatment reactor is operated under basic conditions.

[0059] The means for recycling the unconverted solid waste are conventional and include any appropriate transport system (e.g. conveyor belt, screw, hopper or belt).

[0060] Preferably, the installation according to the invention is such that the impregnation device a) and the pretreatment reactor b) are equipped with feeding devices, and such that the recycling means e) comprise fluid connection means between the solid / liquid separation device d) and at least one of said feeding devices to direct the unconverted solid residue from the separation device towards at least one or more of said feeding devices.

[0061] Another object of the invention consists in the use of the method or installation described above for the treatment of lignocellulosic biomass such as wood, straw, agricultural residues, waste from the paper industry and any dedicated energy crops, in particular annual or perennial plants such as miscanthus, with a view to producing sugars, alcohol-type biofuels or organic molecules.

[0062] The invention will be described in detail below, using non-exhaustive figures and examples. Brief Description of the Figures

[0063] Figure 1 is a schematic representation of a first variant of the lignocellulosic biomass conversion plant in which the method according to the invention can be applied.

[0064] Figure 2 is a schematic representation of a Petition 870250089691, dated 02 / 10 / 2025, page 23 / 61 17 / 40 second variant of the lignocellulosic biomass conversion plant in which the method according to the invention can be applied.

[0065] Figure 3 is a schematic representation of a third variant of the lignocellulosic biomass conversion plant in which the method according to the invention can be applied.

[0066] Figure 4 is a schematic representation of a lignocellulosic biomass conversion plant that applies the invention.

[0067] Note that identical references refer to the same flow and the same device in all Figures.

[0068] The description of the references is presented below:

[0069] 1: Water entering the liquor preparation vat

[0070] 2: Acid entering the liquor preparation vat

[0071] 3: Liquor preparation tool (vat)

[0072] 4: Acid liquor towards the impregnation tool (reactor)

[0073] 5: Shredded biomass

[0074] 6: Impregnation tool feeding device

[0075] 7: Washing water for the impregnation tool feed device

[0076] 8: Outlet of the washing liquid from the impregnation tool feeding device

[0077] 9: Impregnation tool (reactor)

[0078] 10: Impregnated and drained biomass

[0079] 11: Pretreatment tool feeding device

[0080] 12: Wash water from the “plug screw feeder” of the pre-treatment tool

[0081] 13: Pressed feed device of the pre-treatment tool Petition 870250089691, dated 02 / 10 / 2025, page 24 / 61 18 / 40

[0082] 14: Pretreatment cooking tool (explosion reactor)

[0083] 15: Steam injection for pretreatment

[0084] 16: Pretreated biomass and steam

[0085] 17: Steam and pretreated biomass separation tool (cyclone)

[0086] 18: Steam

[0087] 19: Pretreated biomass

[0088] 20: Enzymatic hydrolysis reactor

[0089] 21: Hydrolyzed containing sugars

[0090] 22: Alcoholic (ethanolic) fermentation reactor

[0091] 23: Fermented wine containing ethanol (alcohol)

[0092] 24: Ethanol recovery device, for example a distillation column(s)

[0093] 25: Concentrated alcohol

[0094] 26: Liquid residue: raw vinasse

[0095] 27: Solid (lignin) / liquid separation, for example a filter press

[0096] 28: Liquid residue (vinasse)

[0097] 29: Unconverted solid residue (lignin cake)

[0098] 30: Clarified fermentation wine (without solids)

[0099] 31: Clarified hydrolysate (without solids) Description of the modalities

[0100] The invention proposes to recycle the unconverted solid residue from the method of converting lignocellulosic biomass into sugars or alcohols. This residue is mostly composed of lignin, a compound that is not converted during the method. Generally, the residue is separated to be burned in conventional biorefineries, and the lignin can also be used as a compound of interest for special products (resins, bitumen, etc.). The invention proposes to recycle this compound. Petition 870250089691, dated 02 / 10 / 2025, page 25 / 61 19 / 40 for the upstream yield of the method, since the extracted lignin is not pure: it has a fraction of unconverted polymeric sugars (cellulose and / or hemicellulose). Recycling the sugar polymers therefore allows for an increase in the yield of the method.

[0101] The invention relates to the recycling of at least part of a solid residue, referred to as "lignin cake" or "unconverted solid residue" in this text. This solid is advantageously recycled in the pretreatment stage under basic conditions of lignocellulosic biomass, which here also serves for the cleaning stage of the pretreatment reactor, which is a steam explosion cooking reactor for biomass.

[0102] Here we will describe the preferred embodiment of the invention, in which the pretreatment by explosive cooking is preceded by impregnation of the biomass with an acidic liquor: periodically, the biomass passes through an alkaline medium in the cooking reactor to clean the reactor.

[0103] Lignin is one of the main compounds of lignocellulosic biomass (up to 30% of DM). In a method of converting lignocellulosic biomass by valorizing sugars (cellulose and hemicellulose), the lignin cake is a co-product of the method that is formed by water (water represents 50% to 60% by weight of the cake) and solids from the biomass that were not converted during the method, namely, mainly lignin, but also cellulose and hemicellulose.

[0104] Thus, Table 1 below, by way of example, indicates the flow rate entering the method and the composition of an example of biomass (wheat straw) to be treated and of a lignin cake obtained after separation at the end of the alcohol production line: Petition 870250089691, dated 02 / 10 / 2025, page 26 / 61 20 / 40 Table 1 Biomass Unconverted Solid Flow Rate kg / h 100 67 Water % by weight 10 60 Cellulose % by weight 34 8 Hemicellulose % by weight 27 3 Lignin % by weight 15 22 Other % by weight 14 7

[0105] Table 2 below indicates, for the same biomass and the same lignin cake, the flow rates and the composition of the solid compounds, expressed here in dry matter content DM: Table 2 Biomass Unconverted Solids Flow Rate kg / h 100 67 DM % by weight 90 40 Cellulose % DM 38 20 Hemicellulose % DM 30 8 Lignin % DM 17 55 Other % DM 16 17

[0106] Based on these diagrams, it can be observed that two unconverted sugar polymers (cellulose and hemicellulose) are present in the lignin cake, for a total of 11% by weight (or 28% DM). The invention recycles at least part of the lignin cake (unconverted solid) to convert these polymers and consequently increase the yield of the method, since 11% of the polymeric sugars from the biomass are found in the unconverted solid, without adding a dedicated treatment step for this lignin cake.

[0107] Furthermore, the calorific value of the lignin cake (measured by the Higher Heating Value (HHV) of the unconverted solid residue) increases if the sugar polymers contained in it are converted. Indeed, sugar polymers contain oxygen molecules that decrease the average HHV of the solid.

[0108] Some examples of the operating conditions of the main Petition 870250089691, dated 02 / 10 / 2025, page 27 / 61 21 / 40 steps of biomass treatment will be briefly summarized below: The method

[0109] A more detailed description follows of the different key steps of a biomass conversion method that uses such an installation and to which the invention can be advantageously applied: (this is a non-exhaustive example of the invention). Conditioning stage of lignocellulosic biomass

[0110] The treatment method may conventionally include, in its first stage, a conditioning step of the lignocellulosic biomass with at least one shredding to obtain biomass particles with a maximum size of 300 mm. Obviously, it is possible to carry out several successive shredding steps until the desired particle size is reached. In general, the shredded biomass has a particle size (the largest size) of at most 300 mm, more frequently at least 1 mm and often between 2 and 200 mm. Any method known to the person skilled in the art may be applied at this stage. Most often, straw shredding is done with 5 to 100 mm grids. On the other hand, wood is normally chipped into parallelepiped-shaped boards with a length between 20 and 160 mm, a width between 10 and 100 mm and a thickness between 2 and 20 mm.The shredded lignocellulosic biomass is transferred to the next stage by any device known to those skilled in the art, in particular a screw conveyor. Acid liquor impregnation stage

[0111] The treatment method according to the invention includes a step a) impregnating the lignocellulosic substrate with an acid liquor to obtain an impregnated lignocellulosic substrate whose pH is between 0.1 and 3. The purpose of this step is to prepare the lignocellulosic substrate for the pretreatment step. Petition 870250089691, dated 02 / 10 / 2025, page 28 / 61 22 / 40

[0112] Impregnation is carried out in an impregnation reactor at a temperature between 10 and 90°C and preferably at atmospheric pressure. The residence time of the lignocellulosic substrate in the impregnation reactor is usually from 10 seconds to 180 minutes, preferably between 30 seconds and 60 minutes, and even more preferably between 30 seconds and 15 minutes. Preferably, impregnation is carried out in a single step.

[0113] The impregnation reactor or impregnator has one or more screws that transfer the lignocellulosic substrate from the inlet towards the outlet opening. In addition, the impregnator is equipped with one or more tubes to transport the acid liquor and, if necessary, one or more tubes to purge the acid liquor. The aforementioned acid liquor inlet and outlet tubes are normally installed in such a way as to operate in concurrent or countercurrent flow recycling.

[0114] Acid liquor is an aqueous solution of a strong acid, chosen, for example, from sulfuric acid, hydrochloric acid, nitric acid, for example, with an acid content between 0.5 and 4% by weight. Solid / liquid separation step on lignocellulosic substrate impregnated with acid liquor.

[0115] The lignocellulosic substrate impregnated with acid liquor is subjected to a solid / liquid separation step in order to obtain a lignocellulosic substrate with a dry matter content between 15% and 70% by weight and a used acid liquor. Preferably, the lignocellulosic substrate impregnated with acid liquor is first drained to extract at least part of the free acid liquor before being treated by solid / liquid separation.

[0116] The solid / liquid separation step can make use of any technique known to the person skilled in the art, and can be, for example, decantation, centrifugation or pressing.

[0117] Preferably, the substrate is pressed. Petition 870250089691, dated 02 / 10 / 2025, page 29 / 61 23 / 40 lignocellulosic concomitant with its transfer to the pretreatment stage when the latter uses the steam explosion method described below. This method of conducting the stage is ensured, for example, by a compression screw called a “plug screw feeder”, whose operation was described above. The formation of a plug of pressed lignocellulosic substrate ensures tightness to the pressure of the steam explosion reactor, thus preventing dangerous steam releases. The conveyor screw is also equipped with one or more tubes for purging the used liquor (called press) separated during pressing. The press can be recycled to the impregnation stage and / or to the washing stage by the washing liquid 12 that flows through the feed screw 11.

[0118] The wet biomass obtained at the end of the solid / liquid separation stage, which may be referred to as washed and acidified lignocellulosic substrate, preferably has a dry matter content between 15% and 70% by weight, and more preferably between 40% and 65% by weight. Pre-treatment stage of washed and acidified lignocellulosic substrate

[0119] The washed and acidified lignocellulosic substrate undergoes a pretreatment step.

[0120] Cellulose (and possibly hemicelluloses), which are the targets of enzymatic hydrolysis, are not directly accessible to enzymes. This is why a pretreatment of the biomass is carried out before the enzymatic hydrolysis step. The pretreatment essentially aims to modify the physical and physicochemical properties of the cellulosic fraction, such as the degree of polymerization and state of crystallinity.

[0121] Several types of pre-treatment are known to those skilled in the art, which combine a chemical treatment and a treatment Petition 870250089691, dated 02 / 10 / 2025, page 30 / 61 24 / 40 thermal treatment. Specifically mentioned are acid or basic cooking, the Organosolv method, treatments with ionic liquids, and the steam explosion method.

[0122] The preferred pretreatment method is steam explosion (SteamEx or Steam Explosion in English terminology) carried out in an acidic medium. In this method, the lignocellulosic substrate is rapidly brought to a high temperature by injecting pressurized steam. Treatment is stopped by drastic decompression.

[0123] The operating conditions for the steam explosion method are as follows: - Steam is injected directly into the reactor; - The reactor temperature is generally between 150 and 220°C, preferably between 170°C and 210°C. - the pressure is between 5 and 25 bar absolute (0.5 and 2.5 MPa), more preferably between 8 and 19 bar absolute (0.8 to 1.9 MPa), - The residence time before the expansion phase varies from 10 seconds to 90 minutes, and preferably between 3 minutes and 30 or 40 minutes.

[0124] Steam explosion can be carried out in batches or continuously, and the depressurization step, which allows the biomass to be broken down, can be developed over one or more stages.

[0125] At the end of the steam explosion pretreatment stage, a pretreated lignocellulosic substrate is obtained with a high dry matter content, generally between 20 and 70% by weight, and a vapor phase that can be condensed.

[0126] After steam explosion under acidic conditions, the pretreated lignocellulosic substrate typically has a pH lower than that compatible with the enzymatic hydrolysis medium. Therefore, the substrate Petition 870250089691, dated 02 / 10 / 2025, page 31 / 61 25 / 40 lignocellulosic material undergoes a neutralization step to adjust the pH to a value between 4 and 6.

[0127] For the neutralization step, an aqueous solution with a neutralizing agent is used, which may be chosen from all weak or strong bases known to those skilled in the art. By the term base is meant any chemical species which, when added to water, produces an aqueous solution with a pH above 7. Preferably, the neutralizing agent is chosen from potassium hydroxide, sodium hydroxide, ammonia, or lime. Even more preferably, the neutralizing agent is chosen from potassium hydroxide and ammonia, separately or combined. Preferably, the neutralizing agent is used in aqueous solution, with a mass concentration between 2% and 75%, and even more preferably between 20% and 70%.

[0128] Neutralization occurs at a temperature between 15°C and 95°C, and preferably between 20°C and 70°C. In general, the temperature of the neutralization step is not precisely controlled, being regulated simply by the heat released by the acid-base neutralization reaction.

[0129] The neutralization step can be carried out continuously, discontinuously, or in a fed-batch manner.

[0130] It is worth noting that a washing step may be carried out before or after the neutralization step, on all or part of the pretreated lignocellulosic substrate.

[0131] If washing is applied, a liquid stream is brought into contact with the pre-treated lignocellulosic substrate, then the liquid is separated from the solid. The washing step can be carried out by percolation, through successive mixing and liquid / solid separation operations, by washing in a belt filter, or by any other technique known to those skilled in the art. The washing liquid can be the Petition 870250089691, dated 02 / 10 / 2025, pp. 32 / 61 26 / 40 water or a flow of the method. The weight ratio between the added washing liquid and the liquid contained in the substrate to be washed is generally between 0.5 and 4. The washing step generates a washing sugar juice that contains some of the hemicelluloses solubilized during the pretreatment. This washing juice can be used, for example, as a carbon source for the production of biocatalysts (enzymes and / or microorganisms). The washing step generally occurs at temperatures between 10°C and 95°C. Enzymatic hydrolysis step

[0132] The pre-treated lignocellulosic substrate, possibly neutralized and washed, is sent to the enzymatic hydrolysis step of the method.

[0133] The pre-treated lignocellulosic substrate that is sent to the enzymatic hydrolysis step has a dry matter content generally between 15% and 70% by weight.

[0134] The objective of enzymatic hydrolysis is to hydrolyze (depolymerize), using biocatalysts, hemicelluloses and cellulose into fermentable sugars, preferably xylose and glucose.

[0135] The enzymatic hydrolysis step takes place under moderate conditions, at a temperature of 40°C and 55°C, preferably between 45°C and 50°C, and a pH of 4.0 to 5.5, and even more preferably between 4.5 and 5.2. The dry matter content of the enzymatic hydrolysis medium is between 2 and 45% by weight, preferably between 10 and 30% by weight. It is carried out by enzymes produced by a microorganism. Natural or genetically modified microorganisms, such as fungi of the genera Trichoderma, Aspergillus, Penicillium or Schizophyllum, or anaerobic bacteria, for example, of the genus Clostridium, produce an enzymatic cocktail containing mainly cellulases and hemicellulases, suitable for the potent hydrolysis of cellulose and hemicelluloses.

[0136] Enzymatic hydrolysis can be carried out in continuous or batch mode, or continuous fed mode, in one or more reactors. The Petition 870250089691, dated 02 / 10 / 2025, pp. 33 / 61 27 / 40 residency time is between 5 hours and 200 hours, preferably between 24 hours and 120 hours, and even more preferably between 48 hours and 120 hours.

[0137] At the end of the stage, a hydrolysate containing fermentable sugars is recovered from the bioreactor and then treated in the fermentation stage.

[0138] Note that the hydrolysate obtained may eventually undergo one or more treatment steps before the fermentation step. For example, it may be returning to pH, a partial purification to limit the content of the inhibitory compound for the fermentative microorganism, a separation at least partially of the solid residues contained in the hydrolysate (and thus obtain the unconverted solid residue to be treated according to the invention). Fermentation stage of the hydrolysate when the goal is to continue converting the obtained sugars into alcohol(s).

[0139] According to the stage of the solvent and / or alcohol production method, the hydrolysate, if treated, is sent to the fermentation stage, enabling the conversion, using one or more microorganisms of different genera, of fermentable sugars into solvents and / or alcohols of interest. The fermentation methods are known to those skilled in the art and are described particularly in US patent 8,456,633.

[0140] The term solvent designates organic compounds other than alcohols, for example, organic compounds bearing a ketone functional group, such as acetone.

[0141] The term alcohol mainly refers to ethanol, propanol, isopropanol and butanol.

[0142] Natural or genetically modified microorganisms can be chosen, for example, from Saccharomyces cerevisiae, Schizosaccharomyces pombe, Saccharomyces uvarum, Saccharomyces Petition 870250089691, dated 02 / 10 / 2025, pp. 34 / 61 28 / 40 diastaticus, Kluyveromyces fragilis, Candida shehatae, Pichia stipitis, Pachysolen tannophilis or the bacteria Zymomonas mobilis, Clostridium acetobutylicum, Escherichia coli.

[0143] Within the scope of the invention, the fermentation step allows, for example, the production of ethanol separately or in a mixture with butanol, propanol, isopropanol and / or acetone. For example, the fermentative microorganism may be able to produce a mixture called ABE (acetone-butanol-ethanol) or IBE (isopropanol-butanol-ethanol).

[0144] Preferably, the microorganism chosen is a natural or genetically modified yeast of the genus Saccharomyces capable of producing ethanol.

[0145] At the end of the stage, a diluted fermentation must is recovered containing products of interest.

[0146] According to one embodiment of the method, the hydrolysis and fermentation steps can be carried out simultaneously in at least one bioreactor. In this way, enzymatic hydrolysis and fermentation are conducted simultaneously by a method designated by the term Saccharification et Fermentation Simultanées (SFS - Simultaneous Saccharification and Fermentation) or Simultaneous Saccharification and Fermentation (SSF) in English terminology. When the hydrolysis step coincides with the fermentation step, the operating conditions, especially temperature, can be adapted to suit the tolerances of the fermenting microorganism. For example, the temperature can be lowered to between 28°C and 45°C, and preferably between 30°C and 35°C when fermentation is carried out by a yeast of the genus Saccharomyces. The pH is preferably adjusted between 5 and 5.5 to favor the efficiency of the yeasts.

[0147] The production unit for implementing the method according to the invention may include, in addition to the facilities already described, Petition 870250089691, dated 02 / 10 / 2025, pp. 35 / 61 29 / 40 in situ production units of enzymes and / or yeasts. Concentration and purification stage of solvents and / or alcohols from the fermentation must.

[0148] The method according to the invention finally comprises a step of concentration and purification of the product(s) of interest from the fermentation must, which is preceded or followed by a solid / liquid separation step to eliminate at least a fraction of the solid matter present in the fermentation must, and to produce the unconverted solid residue that will be treated according to the invention.

[0149] Preferably, the step of concentration and purification of the product(s) of interest, for example ethanol, performs one or more distillations, which is a technology quite familiar to those skilled in the art. The cargo: lignocellulosic biomass

[0150] According to the invention, the feedstock of the method can be just biomass or biomass in a mixture. The water content contained in the raw feedstock is generally at least 10%, in particular between 10 and 70% by mass.

[0151] Raw biomass is chosen from any type of biomass, preferably a solid biomass, and in particular a lignocellulosic biomass. Non-limiting examples of biomass types include, for example, residues from agricultural activity (in particular straw, corn stalks), residues from forestry activity, products of forestry activity, sawmill residues, crops dedicated, for example, to short-rotation coppices.

[0152] Preferably, the raw biomass, also called native biomass, is lignocellulosic biomass. Basically, its three natural components, present in varying quantities depending on its origin, are: cellulose, hemicellulose, and lignin. The lignocellulosic biomass load is preferably used in its raw form, or Petition 870250089691, dated 02 / 10 / 2025, pp. 36 / 61 30 / 40, that is, with the integrity of the three components: cellulose, hemicellulose, and lignin.

[0153] In a preferred embodiment of the invention, lignocellulosic biomass is chosen from herbaceous biomass, agricultural waste such as straw remains, corn stalks, sugarcane bagasse, forestry or sawmill waste such as wood chips or any other type of woody residue. The impregnation fluid:

[0154] The optional fluid, injected for impregnation, is an aqueous liquid solution with or without acid, at a temperature between 10 and 95°C and at atmospheric pressure. The pH of this chemical solution is between 0.1 and 12.0, preferably between 0.1 and 7, preferably between 0.3 and 2. According to a preferred embodiment, the liquor used is an acid-catalyzed liquor, and the pH of the liquor is adjusted to be between 0.1 and 4, in particular between 0.3 and 2. As examples of acids, at least one acid chosen from sulfuric acid, hydrochloric acid, nitric acid, oxalic acid may be used. Preferably, the percentage of these acids in the aqueous phase is between 0.2 and 8% by weight.

[0155] The invention applies analogously to different methods and installations, in particular to: - facilities intended solely for the production of sugars, and which therefore do not include alcoholic fermentation, - installations that provide for pre-treatment by cooking without prior impregnation with liquor (auto-hydrolysis for example), - Installations that involve pre-treatment by cooking with prior impregnation with a neutral liquor (in particular with autohydrolysis of the biomass in contact with water, naturally releasing an acid, especially acetic acid).

[0156] Figure 1 schematically represents a non-limiting variant of a biomass conversion plant. Petition 870250089691, dated 02 / 10 / 2025, pp. 37 / 61 31 / 40 lignocellulosic material in which the invention can be applied, the installation provides for a pre-treatment of the biomass including impregnation with acid liquor after cooking / steam explosion, then enzymatic hydrolysis followed by alcoholic fermentation, to transform the biomass into ethanol.

[0157] Figure 1 therefore represents a conversion of the processed biomass as follows: the shredded biomass 5 (impregnated or not with a catalytic liquor) is introduced into an impregnation reactor 9 by a feeding device 6. This can be a pressurized feeding medium, for example a compression feed screw, whose terminal portion is conical, equipped with a casing with a drainage grid, an inlet for the washing water 7 and an outlet for the washing water 8. A hermetic biomass plug forms in the downstream portion of the screw, generating compression on the biomass, which causes a pressure differential between the biomass inlet and the biomass outlet of the screw of at least 0.05 MPa. The compression applied to the biomass can consequently expel some of the liquid contained in the biomass, especially when the biomass DM is less than 80% before entering the pressurized feeding medium 6.The extracted liquid is mixed with the wash water and removed with the wash water used 8.

[0158] The impregnation reactor 9 is also fed with acid liquor 4 (water with added sulfuric acid) from a liquor preparation tank 3, which is itself fed with sulfuric acid 2 and water 1.

[0159] The impregnated and drained biomass 10 exits the reactor 9 to feed a steam explosion cooking reactor 14 through another feeding device 11, for example, of the compression type, such as feeding device 6. In device 11, due to the compression exerted on the biomass, the resulting liquid 13 is recovered. Petition 870250089691, dated 02 / 10 / 2025, pp. 38 / 61 32 / 40 part of this pressing, also called the pressed material, composed of water and acid. The device 11 is washed, using a dedicated inlet, with a washing liquid 12 (water and / or a recycled liquid, as shown below), and then purged through the outlet through which the pressed material 13 is also purged.

[0160] Reactor 14 is also fed with steam 15. At the outlet of reactor 14, the biomass-steam mixture passes through a tool 17 to separate the biomass 19 and the steam 18. The biomass 19 is then treated in an enzymatic hydrolysis reactor 20, after which, once hydrolyzed into sugars, the hydrolyzed biomass 21 (also called hydrolysis must) passes to an alcoholic fermentation reactor 22. The biomass fermented into alcohol 23 (also called fermentation must) is then taken to one or more distillation columns 24 to produce concentrated alcohol 25 and raw vinasse 26, which are solid / liquid residues, mixed or separated depending on the arrangement of the columns 24.

[0161] A filter-press type device (not shown) performs a solid / liquid separation, obtaining as output an unshown liquid residue (vinasse) and an unshown residue, which is the lignin cake of interest to the invention.

[0162] This is just one example of an installation and many other variations are possible. Thus, enzymatic hydrolysis and fermentation can be carried out together in the same reactor, as is the case with SSCF for “Simultaneous Saccharification and Co-Fermentation”.

[0163] Figure 2 is a variant of the method according to Figure 1, in which, all factors being equal, solid / liquid separation by a filter press 27 is performed on the fermentation wine 23 before the distillation column(s) 24: a lignin cake 29 is extracted, and the liquid residue, i.e., the fermented wine without solid residue, 30 is then Petition 870250089691, dated 02 / 10 / 2025, pp. 39 / 61 33 / 40 taken to distillation column(s) 24.

[0164] Figure 3 is a variant of the method according to Figure 2, where, all factors being equal, the filter-press type solid / liquid separation device 27 is placed between the enzymatic hydrolysis reactor 20 and the fermentation reactor 22: here the separation is carried out on the still unfermented hydrolysate 21, and the liquid part of the hydrolysate (sugar juice) 31 then goes to the fermentation reactor 22.

[0165] In a variant not shown of the method according to Figure 3, only the production of sugar juice 31 is desired, therefore, conversion by fermentation on the same production line is not continued.

[0166] In all these variants, the object of the invention is to treat the lignin cake 29, whose final destination is to be burned to produce energy.

[0167] Figure 4 represents two alternative or cumulative implementations of the invention, starting from the variant in Figure 2.

[0168] The invention will recycle this solid residue, the lignin cake, during the cleaning phase of the cooking reactor 14 by adding base (KOH) to the cooking reactor 14.

[0169] Cooking biomass in a basic medium, alternating with cooking acid-impregnated biomass, aims to periodically clean the cooking reactor, following the technique described in the aforementioned patents WO 2020 / 126918 and WO 2020 / 126917.

[0170] To give an example of this alternation of pretreatment under acidic and basic conditions, the cooking reactor 14, for example, can be operated in two alternating modes. - in acidic conditions, with impregnation using an acidic liquor in the impregnation reactor for 100 hours, and then transfer towards the cooking reactor 14 Petition 870250089691, dated 02 / 10 / 2025, pages 40 / 61 34 / 40 - Under basic conditions, with direct injection of a base into the cooking reactor 14, particularly through a dedicated inlet. Alternatively, the base can also be injected, at least partially, into the cooking reactor before feeding the reactor with the unconverted wood residue (lignin). One possibility is to feed the cooking reactor only with this unconverted wood residue, through the impregnation device upstream of the cooking reactor. In this case, it may not be necessary to inject a base into the cooking reactor, and the feeding of the acid impregnation device upstream of the cooking reactor can be cut off, or a base impregnation can be operated.Implementation of the invention by recycling the lignin cake 29 towards the feeding device 6 of the impregnation reactor 9

[0171] Recycling prior to impregnation is advantageous because the lignin cake 29 (flow 29' of Figure 4) will again be brought into contact with the impregnation liquor (acid) in the reactor 9, which helps to extract the residual polymeric sugars contained in the cake and then make them react more easily during enzymatic hydrolysis. The concern would be that the lignin cake would disintegrate and be deposited at the bottom of the reactor 9, without being carried along with the biomass. But surprisingly this did not occur, even when the biomass is loaded into the reactor from its injection point to its exit point by the internal screws of the reactor, Implementation of the invention by recycling the lignin cake 29 towards the feeding device 11 of the cooking reactor 14.

[0172] The lignin cake is recycled at least in part (flow 29'' in Figure 4) to feed device 11 of the steam cooking / explosion reactor 14. In this case, the lignin cake, instead of undergoing further impregnation with liquor, is carried by biomass that is already impregnated. Petition 870250089691, dated 02 / 10 / 2025, pages 41 / 61 35 / 40

[0173] In either embodiment, eventually part of the lignin cake (flow 29''' in Figure 4) is not recycled: Only part of the lignin cake could be recycled.

[0174] At the end of production, the non-recycled 29''' cake (called final residue) is stored to serve as fuel, either in the production line or for other uses beyond the production line, such as fuel or to be incorporated into various products.

[0175] The same types of recycling apply, by analogy, to the lignin cakes of the methods in Figures 1 and 3. Examples of achievement Example 1 (comparative)

[0176] This example, not in accordance with the invention, separates the unconverted solid 29 without recycling it. The biomass 5 is a lignocellulosic biomass: wheat straw. The characteristics and composition of the wheat straw-shaped feedstock are as follows: Dry matter: 91.07% Potential sugar: 67.5 g / 100g Biomass flow rate: 65 kg DM / h Particle size: 50 mm

[0177] Biomass is treated according to the method represented in Figure 2. After hydrolysis, cellulose is converted into glucose or glucose oligomers, and hemicellulose is converted into xylose or xylose oligomers. For this, the flow rates of cellulose or hemicellulose are expressed in terms of potential glucose or potential xylose.

[0178] The term “potential sugar” (xylose, glucose for example) used in this document defines the addition of different sugars, regardless of their form: monomeric or polymeric sugar, and corresponds to the theoretical amount of sugar that can be produced from the composition of the raw material, in this case biomass. With Petition 870250089691, dated 02 / 10 / 2025, pp. 42 / 61 36 / 40 effect, after pretreatment by cooking, a portion of the sugars remains in the form of sugar polymers (cellulose or hemicellulose, for example), and a portion of the sugars is in the form of sugar monomers (glucose or xylose, for example). This measurement can be made using the ASTM E1758-01(2020) standard “Standard Test Method for Determination of Carbohydrates in Biomass by High Performance Liquid Chromatography”. As defined by the standard, to express this amount of sugars in polymer form (cellulose, for example), the water of hydrolysis must be removed to this extent.

[0179] The operating mode is as follows:

[0180] The operating conditions are detailed below: Mode 1 = production:

[0181] - Impregnation for production in impregnation reactor 9: Acid solution flow rate: 1.5 kg / h (H2SO4) Impregnation temperature: 80°C

[0182] - Steam explosion of impregnated biomass in pretreatment reactor 14: Residence time: 5 min Steam temperature: 190°C Production duration: 20 hours

[0183] After 20 hours of production, the cleaning sequence is performed under the following conditions: Mode 2 = production + cleaning:

[0184] - Impregnation in impregnation reactor 9: Acid solution flow rate: 1.5 kg / h (H2SO4) Impregnation temperature: 80°C

[0185] - Steam explosion of impregnated biomass in pretreatment reactor 14: Residency time: 10 min Petition 870250089691, dated 02 / 10 / 2025, pp. 43 / 61 37 / 40 Temperature in the reactor: 200°C KOH temperature: 130°C KOH flow rate: ~300 kg / h Cleaning duration: 2 hours Concentration of KOH used in the liquor: 7.7% by weight Number of cycles: 3 cycles of mode 1 (production) and 1 cycle of mode (production + cleaning)

[0186] - Cleaning of cyclone 17 (separation device) Number of water rinses: 2, after each cleaning.

[0187] After 3 cycles of mode 1 + mode 2, for a total production duration of 66 h (60 hours of production and 6 hours of cleaning), the cleaning proves to be effective.

[0188] The mass of clean material from the reactor at the end of the procedure (after these 3 cycles) is a maximum of 3 kg. To perform one cycle, the following were required:

[0189] - 1,300 kg of biomass for production (20 hours)

[0190] - 130 kg of biomass for production and cleaning (2 hours)

[0191] to produce 325 kg of ethanol with a DM yield of 22.7% Example 2 (according to the invention)

[0192] This example according to the invention proposes recycling the unconverted solid 29 at the inlet of the cooking reactor 14 by means of the feed screw 11 in the cleaning phase. The biomass used in this example is the same biomass as in example 1.

[0193] Biomass is treated according to the method represented in Figure 2. After hydrolysis, cellulose is converted into glucose or glucose oligomers, and hemicellulose is converted into xylose or xylose oligomers.

[0194] The operating conditions are detailed below: Petition 870250089691, dated 02 / 10 / 2025, pp. 44 / 61 38 / 40 Mode 1 = production:

[0195] - Impregnation for production in impregnation reactor 9: Load: wheat straw at a flow rate of 65 kg DM / h Acid solution flow rate: 1.5 kg / h (H2SO4) Impregnation temperature: 80°C

[0196] - Steam explosion of impregnated biomass in pretreatment reactor 14: Residence time: 5 min Steam temperature: 190°C Production duration: 20 hours

[0197] After 20 hours of production, the cleaning sequence is performed under the following conditions: Mode 2 = production + cleaning: (100% recycling of lignin residue 29) - Impregnation in impregnation reactor 9:

[0198] Load: 65 kg DM / h of recycled lignins (= unconverted wood residue 29)

[0199] The acid feed to the impregnation reactor is suspended. Impregnation temperature: 80°C

[0200] - Steam explosion of impregnated biomass in pretreatment reactor 14: Residence time: 10 min Temperature in the reactor: 200°C KOH temperature: 130°C KOH flow rate: ~300 kg / h Cleaning duration: 2 hours KOH concentration in the liquor: 7.7% by weight Number of cycles: 3 cycles of mode 1 (production) and 1 cycle of mode (production + cleaning)

[0201] - Cleaning of cyclone 17 (separation device) Petition 870250089691, dated 02 / 10 / 2025, pages 45 / 61 39 / 40 Number of “rinses” with water: 2, after each cleaning after 3 cycles of mode 1 + mode 2, for a total production time of 66 h (60 hours of production and 6 hours of cleaning).

[0202] To complete a cycle, the following were necessary: - 1,300 kg of biomass for production (20 hours) - 0 kg of biomass for production and cleaning (2 hours) replaced by recycled lignin to produce 325 kg of ethanol with a dry matter yield of 25.0%.

[0203] This example shows that when 100% of the biomass content is replaced by lignin (the unconverted residue), the cleaning is as effective as in example 1. Biomass consumption was also reduced to produce basic bagasse with a 100% reduction during the cleaning phase, which represents a 9% increase in ethanol yield during the cycle period.

[0204] In summary, when compared to the state of the art, the present invention shows the following advantages: - Cleaning the cooking reactor in an alkaline medium is at least as effective when all or part of the biomass is replaced by the unconverted solid residue (the lignin cake 29) - The total sugar / ethanol yield of the method can be further improved by recycling the unconverted polymeric sugars (cellulose and hemicellulose) contained in this woody residue. After recycling in the pretreatment, these polymeric sugars are partially converted into monomeric sugars or become more accessible to the enzymes used in the enzymatic hydrolysis step. In either case, even when the celluloses and hemicelluloses bound to the lignin are not extracted by recycling, particularly when recycling occurs towards the cooking reactor and not towards the impregnation reactor, the overall yield is improved because, at the same rate, the same amount of cellulose is extracted. Petition 870250089691, dated 02 / 10 / 2025, pp. 46 / 61 A 40 / 40 alcohol / sugar ratio is produced with less biomass, with the lignin cake replacing part of the biomass during cooking in a basic medium in reactor 14. - The quality of the lignin in the final residue is improved because the conversion of sugars has made it purer / richer in lignin; therefore, the PCS (polymer concentration) of the solid is increased, since polymer sugars have a lower PCS than lignin. Less biomass is "consumed" during the cleaning phase of the cooking reactor 14 in basic medium, as it is possible to replace all or part of this material with lignin cake, which allows, with the same amount of biomass, to produce more sugars / alcohol. Petition 870250089691, dated 02 / 10 / 2025, pp. 47 / 61

Claims

1 / 5 CLAIMS 1. Method for treating lignocellulosic biomass, characterized in that it comprises: b) an acid or neutral pretreatment step of the biomass previously carried out under acidic or neutral pH conditions in a pretreatment reactor, to produce an acid or neutral pretreated biomass, wherein said step b) is operated alternately with b') a basic pretreatment step of the biomass previously carried out under acidic, neutral or basic conditions in the pretreatment reactor, with possible addition of base, to produce a basic pretreated biomass, and then c) an enzymatic hydrolysis step in a hydrolysis reactor (16) of the acid or neutral pretreated biomass resulting from step b) and / or the basic pretreated biomass resulting from step b').to obtain hydrolyzed biomass d) a solid / liquid separation step of the hydrolyzed biomass resulting from step c) in the form of sugar(s) or a solid / liquid separation step of the hydrolyzed biomass in the form of sugar(s) resulting from step c), then treated in one or more additional steps subsequent to step c) of enzymatic hydrolysis, to obtain a separated juice and an unconverted solid residue, e) a recycling step of at least part of said unconverted solid residue obtained in step d) towards the basic pretreatment step b'.

2. Method, according to the preceding claim, characterized in that step b') which produces the basic pretreated biomass is a cleaning step of the impregnation reactor.

3. Method, according to any of the preceding claims Petition 870250089691, dated 10 / 02 / 2025, page 48 / 61 2 / 5, characterized in that pretreatment steps b) and b') include cooking the biomass, particularly accompanied by steam explosion of said biomass.

4. A method, according to any of the preceding claims, characterized in that a quantity of unconverted solid waste corresponding to at least 10%, particularly at least 20%, preferably at least 30 or 40% by weight of the total waste and biomass supply to said pretreatment reactor during said stage b') is recycled from step e) towards step b').

5. A method, according to any of the preceding claims, characterized in that in step e) at least part of the unconverted solid waste is recycled towards step b') of pretreatment by introducing said waste into the pretreatment reactor.

6. A method, according to any of the preceding claims, characterized in that the acid or neutral pretreatment step b) and / or the basic pretreatment step b') includes a prior impregnation step a) and / or a'), particularly in an impregnation reactor, of the biomass with an acidic, neutral or basic aqueous solution.

7. Method according to the preceding claim, characterized in that the basic pretreatment step b') includes a prior impregnation step a'), particularly in an impregnation reactor, of the biomass with an acidic, neutral or basic aqueous solution, and in that in step e) at least part of the unconverted solid residue is recycled towards the pretreatment step b'), introducing said residue into the impregnation reactor during the impregnation step a').

8. Method, according to claim 6 or 7, characterized by the fact that step a') of biomass impregnation and step b') of basic pre-treatment of the impregnated biomass is carried out in the impregnation and pre-treatment reactors, respectively, each of which is equipped with a biomass feeding device, and in which step e) of recycling the unconverted solid residue is carried out by introducing at least part of said residue with the biomass at the beginning or during the treatment into at least one of said feeding devices.

9. A method, according to any of the preceding claims, characterized in that the basic pretreatment step b') includes adding base to the pretreatment reactor.

10. Method, according to any of the preceding claims, characterized in that it further comprises: - a step f) of fermenting the hydrolyzed biomass in the form of sugar(s), to obtain a fermented biomass containing at least one alcohol, and the step d) of solid / liquid separation is operated on said fermented biomass.

11. Method, according to the preceding claim, characterized in that the enzymatic hydrolysis (c) and fermentation (f) steps are carried out simultaneously on the pretreated biomass.

12. Method according to claim 10 or 11, characterized in that it further comprises: - a step g) for separation or purification, particularly distillation, of the fermented biomass, wherein the solid / liquid separation step d) is operated before or after said separation or purification step g).

13. Method, according to any of the preceding claims, characterized in that it further comprises: - a step h) of combustion of the so-called final unconverted solid residue obtained at the end of the biomass treatment, the heat of which is used in a step of said method that requires heating, in particular the heating of a fluid, particularly in step b) and / or in step b') of pre-treatment by cooking or in a step g) of separation by distillation, - and which is optionally preceded by a step i) of drying said residue.

14. A method, according to any of the preceding claims, characterized in that the solid / liquid separation step (d) is carried out by filtration, in particular using a pressing or draining device, such as a filter press or a vacuum filter, a belt filter, a belt press or a centrifugal, decanting, centrifugal drying device or a combination of different devices.

15. A method, according to any of the preceding claims, characterized in that lignocellulosic biomass is converted into sugar juice, in particular into C5 and C6 juices, after enzymatic hydrolysis, or into alcohol after fermentation of said sugar juice.

16. Installation for implementing the method as defined in any of the preceding claims, characterized in that it comprises: a) an impregnation device, particularly an impregnation reactor, for biomass with an aqueous solution, in particular acidic or neutral; b) a pre-treatment reactor for cooking the impregnated biomass from the impregnation device, wherein said cooking is optionally accompanied by steam explosion to obtain a pre-treated biomass, and said reactor is equipped with means for injecting a basic aqueous solution. Petition 870250089691, dated 02 / 10 / 2025, p.51 / 61 5 / 5 c) an enzymatic hydrolysis reactor for pre-treated biomass, to obtain hydrolyzed biomass, and said installation further comprises d) a solid / liquid separation device for hydrolyzed biomass or for hydrolyzed biomass subsequently treated in one or more additional reactors or devices arranged downstream of the enzymatic hydrolysis reactor c), to obtain an unconverted solid residue, e) means for recycling at least part of said unconverted solid residue obtained in step d) towards the impregnation device and / or towards the pre-treatment reactor when the pre-treatment reactor is operated under basic conditions. Petition 870250089691, dated 02 / 10 / 2025, pp. 52 / 61.

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