Process for treating lignocellulosic biomass

Abstract

The invention relates to a method for treating a lignocellulosic biomass, witha) an optional step of impregnating the biomass (1) b) a step of cooking (3) the biomass (1) in the presence of water vapor (2) to obtain a mixture comprising the biomass (5) and water vapor (4a),c) a separation step to obtain the pretreated biomass (5) and the water vapor (4a),d) a step of condensing (17) the water vapor (4a) from the cooking step b) into liquid effluent (4b),e) a step of enzymatic hydrolysis (6) to obtain a hydrolyzed biomass (7) f) a step of fermentation (8) of the hydrolyzed biomass (7) to obtain a mixture comprising a fermented biomass (9) and a solid residue,then at least one step of washing said mixture or said solid residue obtained in step f), using the liquid effluent from condensation step d). Figure for abstract: Fig. 2

Description

Title of the invention: Method for treating lignocellulosic biomass Technical field

[0001] The invention relates to a method for treating lignocellulosic biomass to produce so-called second generation (2G) sugar juices, which can then be converted to produce other products by biochemical means, in particular by fermentation (for example alcohols such as ethanol, butanol), or other molecules, for example solvents such as acetone etc. Prior art

[0002] Lignocellulosic biomass represents one of the most abundant renewable resources on Earth. The substrates considered are very varied, they concern both woody substrates such as different woods (hardwoods and softwoods), co-products from agriculture (wheat straw, corn cobs, etc.) or other agri-food industries, paper, lignocellulosic waste, etc.

[0003] The process for treating lignocellulosic biomass generally comprises - pretreatment of the biomass by cooking, possibly coupled with a steam explosion and optionally preceded by impregnation of the biomass with an acidic, basic, neutral or oxidizing liquor, - enzymatic hydrolysis, leading to the production of sweet juices, generally based on C5 and C6 sugars (i.e. sugars with 5 or 6 carbons), - then, if we continue the conversion, a fermentation of these sugars by a yeast, to convert them into alcohol of the ethanol type. The process also includes steps of separation and / or purification of the targeted final product (sugar, alcohol, solvent, etc.).

[0004] Lignocellulosic biomass is composed of three main polymers: cellulose (35 to 50% by weight), which is a polysaccharide essentially made up of hexoses; hemicellulose (20 to 40% by weight), which is a polysaccharide essentially made up 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 the intrinsic properties of the plant wall and are organized into a complex tangle. Among the three basic polymers that integrate lignocellulosic biomass, cellulose and hemicellulose are those that allow the production of 2G sugar juices.

[0005] Most often, hemicellulose is mostly broken down into sugar during pretreatment, and cellulose is converted into sugar (glucose) by hydrolysis in enzyme. However, access to raw cellulose remains difficult for enzymes, hence the need for pretreatment. This pretreatment makes it possible to modify the physicochemical properties of lignocellulosic biomass in order to improve the accessibility of cellulose to enzymes and its reactivity to enzymatic hydrolysis.

[0006] Numerous technologies of interest to the invention for carrying out this pretreatment exist, which will hereinafter be grouped under the generic term of "cooking": acid cooking, alkaline cooking, cooking by auto-hydrolysis, steam explosion, processes known as "organosolv pulping" according to the known English term (or treatment with organo-solvent in French).

[0007] 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 in the document “Bioethanol production from agricultural wastes: an overview”, N. Sarkar, S. Kumar Ghosh, S. Bannerjee, K. Aikat, Renewable Energy 37 (2012) 19-27.

[0008] One of the most effective pretreatments is steam explosion, especially under acidic conditions, which allows almost complete hydrolysis of the hemicellulose and a significant improvement in the accessibility and reactivity of the cellulose to enzymes. This pretreatment may be preceded by other treatment(s).

[0009] By way of example, patent FR 3 075 203 describes a process with impregnation of the biomass with an acid liquor, then cooking and steam explosion of the impregnated biomass, with adjustment of the acidity of the acid liquor and recycling thereof.

[0010] These different types of process, starting from lignocellulosic biomass, generate solid residues based on lignin, in particular after enzymatic hydrolysis, and / or after fermentation if the conversion of sugars into alcohol is continued in particular. These solid residues, which will be called in this text "unconverted solid residue" or "solid residue washed from lignin", are rich in lignin, which does not react or reacts little to the action of the enzymes used for the hydrolysis of the biomass and which are generally cellulases and hemicellulases. These woody residues can be used, in particular as fuels, or be integrated as a filler in products based on resin or bitumen for example. However, these unconverted residues are not made up (apart from a certain quantity of water) only of lignin: they can also contain hemicellulose and / or cellulose which have not reacted to hydrolysis.And removing these residues from the biomass conversion process means losing these unreacted polymeric sugar fractions, which impacts the conversion efficiency of biomass into sugar (or alcohol). This is why a solution has been proposed, for example, in patent EP 3 587 583 to separate the juice (liquid) from fermentation from the lignin-based residue (solid), which consists of . a very efficient separation comprising a contacting step followed by extraction / separation and washing of the solid residue to extract the maximum amount of liquid juice it contains. However, these solid / liquid separation steps involve the use of a significant quantity of wash water.

[0011] Furthermore, patent application EP 3 177 672 discloses a method for producing chemical compounds, which consists of recovering the steam used in steam cooking biomass, condensing it and then extracting these chemical compounds with which the water is charged and which are by-products of cooking the biomass. It is only after this extraction that the water is then recycled into the biomass cooking reactor. However, this extraction of chemical compounds is an additional step, costly in terms of time and tools.

[0012] The invention then aims to remedy these various drawbacks. The invention aims to improve the treatment of lignocellulosic biomass. Its more particular aim is to maintain or increase biomass conversion yields, while reducing the consumables or tools required for this conversion. Summary of the invention

[0013] The invention firstly relates to a method for treating a lignocellulosic biomass, said method comprising (a) an optional step of impregnating the biomass with a liquor, in particular acidic, to obtain an impregnated biomass, b) a step of cooking the biomass, optionally impregnated in step a), in the presence of water vapour, for example of the steam explosion type, to obtain a mixture comprising the pretreated biomass and water vapour, c) a step of separating the mixture of pretreated biomass and water vapour, to obtain on the one hand the pretreated biomass and on the other hand water vapour, d) a step of condensation of the water vapor from the cooking step b) into liquid effluent comprising mainly liquid water, e) a step of enzymatic hydrolysis of the pretreated biomass, to obtain a hydrolyzed biomass in the form of sugar(s), in particular monomeric sugars, f) a step of fermentation of the hydrolyzed biomass in the form of sugar(s), in order to obtain a mixture comprising a fermented biomass comprising at least one alcohol in the form of a juice and a solid residue, then at least one treatment step aimed at treating this mixture or one of its components in order to extract, isolate and / or purify the fermented biomass, said treatment step, or at least one of them, comprising at least one step of washing said mixture or said solid residue obtained in step f), said washing step using at least in part the liquid effluent from condensation step d).

[0014] For the purposes of the present invention, the term “solid” (unconverted) residue means a residue which comprises at least 20% by weight of solid, in particular at least 30 or 35% by weight of solid. The solid content can be measured by its Dry Matter (acronym “DM”) rate, which is measured according to the ASTM E1756 - 08(2015) “Standard Test Method for Determination of Total Solids in Biomass” standard. The DM of the unconverted “solid” residue according to the invention is preferably at least 20, 30 or 35%.

[0015] For the purposes of the present invention, the term "liquid effluent comprising mainly liquid water" means water resulting from the condensation of the water vapor recovered after cooking which may contain volatile organic compounds. This liquid effluent generally comprises at least 90% water by volume, for example at least 95% and at most 97 or 98% or 99% water by volume.

[0016] For the purposes of the present invention, when step a) of impregnation is carried out, the impregnation liquor may comprise a chemical compound such as an acid, a base or an oxidizing agent or by a water-based liquor, with autohydrolysis of the biomass naturally releasing an acid, in particular acetic acid.

[0017] The invention has thus identified a source of water for carrying out washing after enzymatic hydrolysis and fermentation, in particular that of the solid residue, namely the condensed water resulting from the cooking of the biomass. And this recycling from upstream to downstream of the process (considering the succession of stages of treatment of the biomass) has proven to be very advantageous in several respects: - it makes it possible to significantly reduce the water consumption of the process, in particular that of the aforementioned washing step, while the quantity of washing water can represent a significant part of the water required for the entire conversion process (at least 10 or even 20%, for example around 25% of the total water consumed), - it limits the dilution of the conversion product, of the alcohol type ethanol before its separation / purification stages, in particular before distillation, since there is no, or less, additional water input - this aqueous effluent from cooking has no impact on the quality of the unconverted solid residue obtained after solid / liquid separation of the fermented biomass then washing, the solid residue retains the same calorific properties when it is then used in combustion (no addition of organometallic compounds such as silica, nor additional trace elements generating ash). The temperature of the liquid effluent (mainly condensed water) for washing can be between 30 and 90°C, preferably between 30 and 60°C. Carrying out washing with a liquid phase above ambient temperature promotes washing by tending to reduce its duration.

[0018] The pH of the liquid effluent from condensation (mostly condensed water) can be between 2 and 4. This water is in fact acidic when the biomass has been impregnated with an acidic liquor prior to cooking. This acidity can prove advantageous because it promotes the decomposition of solid deposits which may have accumulated in the supply pipes of the filtration / washing device.

[0019] However, this choice could have proved problematic. Indeed, the liquid effluent resulting from the condensation of the steam during the cooking step is water which can be loaded with traces of various compounds carried along with it, in particular furfural, 5-HMF, or organic acids, such as acetic acid. However, more particularly furfural or its derivatives prove harmful, because they can be toxic, in particular, to the yeasts used during the fermentation step, which can result in the appearance of a latency period during fermentation, a slowdown in alcohol production, and ultimately a loss of ethanol at the end of fermentation. It is therefore not possible to recycle this condensation water to the reaction steps following cooking, unless one considers extracting these compounds from the condensed water beforehand, which requires a dedicated separation / purification step, and additional ad hoc tools.And it has proven to be no more relevant to recycle this condensation water to an upstream stage (a stage of impregnation or washing of the biomass before cooking for example or to produce the steam necessary for cooking the biomass), because these compounds risk accumulating from stage to stage, which again would require purifying the condensed water.

[0020] Now what the invention has discovered is that it is entirely possible to use / recycle this condensed water, without treatment or purification, downstream of the cooking step generating the steam, but after the fermentation step: thus, the traces of compounds contained in the condensed water do not have any potentially problematic effect on the fermentation, and, surprisingly, using this condensed water after the fermentation did not cause any inconvenience, and absolutely did not affect the yield or the quality of the intended product. This recycling is therefore very effective, and occurs in the conversion process just at the appropriate step / time to avoid prior treatment of the condensed water.

[0021] Advantageously, the process according to the invention can comprise, after fermentation step f), at least two treatment steps: (g) a step of solid / liquid separation of the fermented biomass, in order to obtain a separate juice comprising at least this alcohol and a solid residue, h) a step of washing the solid residue with, as washing water, at least in part, the liquid effluent from condensation step d).

[0022] Use the condensed water from the steam used when cooking the biomass for washing the solid phase recovered after solid / liquid separation from fermentation did not cause any disadvantages, neither on its efficiency in extracting juice trapped in the solid phase, nor on the final quality of the alcohol, nor on the heat capacity of the ultimate solid residue. And, as mentioned previously, the washing water after solid / liquid separation of the fermented biomass can constitute a significant item of water consumption for the process as a whole, and reducing or even eliminating a water supply for this step is extremely economically advantageous.

[0023] The water vapor separated in separation step c) may be loaded with by-products from cooking the biomass from step b), in particular comprising at least one of the following by-products: furfural, sugar degradation compounds such as 5-hydroxymethylfurfural 5-HMF, one or more organic acids such as acetic acid, methanol. The contents of these different by-products (expressed in liters of this vapor once condensed, called “liquid effluent”) may be, for example, the following: Furfural: between 10 and 50 g / l Acetic acid: between 1 and 15 g / l 5-HMF: between 0 and 2 g / l Other component(s): less than 1 g / l

[0024] According to one embodiment of the invention, all of the liquid effluent from condensation step d) is used as wash water in washing step h). In this case, all of the condensed effluent is therefore recycled in washing step h). Alternatively, a certain portion may be kept for another use, or, if it is in too large a quantity compared to the needs, be stored or sent to a final water treatment unit of the process.

[0025] According to one embodiment of the invention, the washing step h) uses as washing water only the liquid effluent from the condensation step d). In this case, the quantity of condensed water is sufficient to completely replace any external water supply; this is the most advantageous configuration because it eliminates any consumption of external water for the washing step.

[0026] According to one embodiment of the invention, the washing step h) uses as washing water partly the liquid effluent from the condensation step d) and partly a supply of other water, in particular in a volume proportion of 10 / 90 to 90 / 10. In this case, it may be, in particular, that the quantity of available liquid effluent is insufficient (or for other reasons) and, in this case, it is supplemented with an external supply of water.

[0027] The enzymatic hydrolysis steps e) and fermentation f) can be carried out simultaneously on the pretreated biomass. We then speak of SSF for the acronym of Anglo-Saxon term "Simultaneous Saccharification and Fermentation" or SSCF for the acronym of the Anglo-Saxon term "Simultaneous Saccharification and Co-Fermentation". They can also be carried out one after the other, in separate reactors in particular.

[0028] The method according to the invention may also comprise: (i) a step of separation or purification, in particular distillation, of the fermented biomass, step g) of solid / liquid separation and step h) of washing being carried out before or after said step i) of separation or purification.

[0029] Condensation step d) can be carried out by heat exchange of the water vapor with a fluid used in the process, in order to raise the temperature of said fluid.

[0030] Step g) of solid / liquid separation can be 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, a centrifugation, decantation or spin-drying device or the combination of at least two of these devices.

[0031] Step g) of solid / liquid separation can be carried out discontinuously or continuously

[0032] Step h) of washing the solid residue can be carried out continuously, in co-current or counter-current.

[0033] In the context of the present invention, when a solid / liquid separation is carried out, the separated "solid phase" is to be understood as containing the solid phase itself and the liquid phase trapped in said solid phase.

[0034] The invention also relates to any installation implementing the method described above.

[0035] The invention also relates to an installation, in particular for implementing the method described above and which comprises: (a) an optional impregnation device, in particular an impregnation reactor, of the biomass with a liquor, in particular acid, to obtain an impregnated biomass (b) a device for cooking the biomass, optionally impregnated with the impregnation device (a), in the presence of water vapour, for example of the steam explosion type, to obtain a mixture comprising the pretreated biomass and water vapour, (c) a device for separating the mixture of pretreated biomass and water vapour, to obtain on the one hand the pretreated biomass and on the other hand water vapour, d) a device for condensing the water vapour from the cooking step b) into liquid effluent, in particular a heat exchanger device, (e) a device for enzymatic hydrolysis, in particular an enzymatic hydrolysis reactor, of the pretreated biomass, to obtain hydrolyzed biomass in the form of sugar(s), (f) a device for fermenting the hydrolyzed biomass in the form of sugar(s), in particular a fermentation reactor, in order to obtain a mixture comprising a fermented biomass comprising at least one alcohol in the form of a juice and a solid residue, said device being separate from the enzymatic hydrolysis device or being common with it, then at least one treatment device intended to treat this mixture or one of its components with a view to extracting, isolating and / or purifying the fermented biomass, including at least one washing device using at least part of the liquid effluent from the condensation device d).

[0036] This installation can also include, downstream of the fermentation device f), two treatment devices: (g) a device for solid / liquid separation of the fermented biomass, in order to obtain a separate juice comprising at least this alcohol, and a solid residue, in particular a pressing or draining device, such as a filter press or a vacuum filter, a belt filter, a belt press, a centrifuging, decanting or dewatering device or the combination of at least two of these devices (h) a device for washing the solid residue, possibly common with the solid / liquid separation device or separate from it, with, as washing water, at least in part, the liquid effluent from condensation step (d).

[0037] The invention also relates to the use of the method or installation described above, for the treatment of lignocellulosic biomasses, such as wood, straw, agricultural residues, paper residues, and all dedicated energy crops, in particular annual or multi-annual plants such as miscanthus, with a view to producing alcohol-type biofuels or bio-sourced molecules.

[0038] The treatment method targeted by the invention can convert the lignocellulosic biomass into sweet juice, in particular C5 and C6 juices, after enzymatic hydrolysis, then into alcohol(s), in particular ethanol, after fermentation of said sweet juice.

[0039] The invention will be described in detail below, using figures and non-limiting examples.

[0040] List of figures [Fig.l] [Fig.l] is a block diagram of a process for converting lignocellulosic biomass without implementing the invention. [Fig.2] [Fig.2] is a block diagram of a biomass conversion process implementing the invention in a first embodiment. [Fig.3] [Fig.3] is a block diagram of a biomass conversion process involving implements the invention in a second embodiment.

[0041] Note that the same references relate to the same flow, the same device, the same step from one figure to another.

[0042] The description of the references is presented below: 1: Biomass 2: Water vapor 3: Pre-treatment 4a: Vapor phase 4b: Pretreatment condensate 5: Pretreated biomass 6: Enzymatic hydrolysis 7: Hydrolyzate 8: Fermentation (possibly simultaneous with 6) 9: Fermentation must, containing alcohol 10a: Solid / liquid filtration 10b: Washing of the solid fraction trapped in the solid / liquid separation tool. 10c: Compaction of washed solid residue 11: Washing water 12a: Filtration filtrate 12b: Wash filtrate 12c: Compaction filtrate 13: Washed solid residue 14: Purification of alcohol 15: Purified alcohol (ethanol over 96% by weight) 16: Vinasses 17: Condensation and cooling of steam 18: Water treatment 19: Water treated for recycling Description of the embodiments

[0043] The process Below is a detailed description of the various key stages of a biomass conversion process to which the invention can advantageously be applied: (this is an example to which the invention is not limited).

[0044] Stage of conditioning of lignocellulosic biomass The treatment process comprises in its first stage, a stage of conditioning the lignocellulosic biomass with at least one grinding so as to obtain biomass particles having a size of at most 300mm. It is well It is understood that it is possible to carry out several successive grinding stages in order to achieve the target particle size. Generally, the ground biomass has a particle size (the largest size) of at most 300 mm, most often at least 1 mm, and often between 2 and 200 mm. Any method known to those skilled in the art can be implemented to carry out this stage. Most often, the grinding of straw is done with grids of 5 to 100 mm. As for the wood, it is generally shredded into parallelepiped plates with a length of between 20 and 160 mm, a width of between 10 and 100 mm and a thickness of between 2 and 20 mm. The ground lignocellulosic biomass is brought to the next stage by any means known to those skilled in the art, in particular a transfer screw. Impregnation step with an acid liquor

[0045] The treatment method according to the invention comprises a step a) of impregnating the lignocellulosic substrate with an acid liquor so as to obtain an impregnated lignocellulosic substrate whose pH is between 0.1 and 3. This step aims to prepare the lignocellulosic substrate for the pretreatment step.

[0046] The 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, the impregnation step is carried out in a single step.

[0047] The acid liquor is an aqueous solution of a strong acid, which is for example chosen from sulfuric acid, hydrochloric acid, nitric acid, for example with an acid content of between 0.5 and 4% by weight.

[0048] Solid / liquid separation step on the lignocellulosic substrate impregnated with acid liquor The lignocellulosic substrate impregnated with acid liquor is subjected to a solid / liquid separation step in order to obtain a lignocellulosic substrate having a dry matter content of between 15% and 70% by weight and a spent acid liquor. Preferably, the lignocellulosic substrate impregnated with acid liquor is first drained in order to extract at least a portion of the free acid liquor before being treated by solid / liquid separation.

[0049] The solid / liquid separation step can implement any technique known to those skilled in the art, which can be, for example, decantation, centrifugation or pressing.

[0050] Preferably, pressing of the lignocellulosic substrate is carried out concomitantly with its transfer to the pretreatment step when the latter implements the steam explosion process which is described below.

[0051] The wet biomass obtained at the end of the solid / liquid separation step, which can be designated by the term "acidified lignocellulosic substrate", has a dry matter content preferably between 15% and 70% by weight, and more preferably between 40 and 65% by weight.

[0052] Pretreatment step of the acidified lignocellulosic substrate

[0053] The acidified lignocellulosic substrate undergoes a pretreatment step.

[0054] Cellulose (and possibly hemicelluloses) which are the targets of enzymatic hydrolysis are not directly accessible to the enzymes. This is why a pretreatment of the biomass is implemented before the enzymatic hydrolysis step. The pretreatment aims in particular to modify the physical and physicochemical properties of the cellulose fraction, such as its degree of polymerization and its state of crystallinity.

[0055] Various types of pretreatment are known to those skilled in the art; they combine chemical treatment and heat treatment. Examples include acid or basic cooking, the Organosolv process and the steam explosion process.

[0056] The preferred pretreatment process is steam explosion ("SteamEx" or "Steam Explosion" according to English terminology) carried out in an acidic medium. This is a process in which the lignocellulosic substrate is rapidly brought to a high temperature by injecting pressurized steam. The treatment is stopped by sudden decompression.

[0057] The operating conditions of the steam explosion process are as follows: the steam is injected directly into the reactor; the temperature of the reactor is generally between 150 and 220°C, preferably between 170°C and 210°C, the pressure is between 5 and 25 bars absolute (0.5 and 2.5 MPa), more preferably between 8 and 19 bars absolute (0.8 to 1.9 MPa), the residence time before the expansion phase varies from 10 seconds to 50 minutes, and preferably between 3 minutes and 30 or 40 minutes

[0058] The steam explosion can be carried out in batch or continuous mode, and the depressurization step which allows the biomass to be destructured can take place in one or more steps.

[0059] At the end of the steam explosion pretreatment step, a pretreated lignocellulosic substrate with a high dry matter content, generally between 20 and 70% by weight, and a vapor phase which can be condensed is obtained.

[0060] Following the steam explosion under acidic conditions, the pretreated lignocellulosic substrate generally has a pH lower than that which is compatible with the medium for enzymatic hydrolysis. Thus the lignocellulosic substrate is subjected to a neutralization step to bring its pH to a value between 4 and 6.

[0061] For the neutralization step, an aqueous solution containing a neutralizing agent is used. neutralization which can be chosen from any weak or strong base known to those skilled in the art. By the term base, we mean any chemical species which, when added to water, gives an aqueous solution with a pH greater than 7. Preferably, the neutralization agent is chosen from potassium hydroxide, sodium hydroxide, ammonia, lime. Even more preferably, the neutralization agent is chosen from potassium hydroxide and ammonia, alone or in combination with each other. Preferably, the neutralization agent is used in aqueous solution, with a mass concentration of between 2% and 75%, and even more preferably between 20% and 70%.

[0062] The neutralization is carried out 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 and is simply governed by the heat released by the acid-base neutralization reaction.

[0063] The neutralization step can be carried out continuously, batchwise or fed-batch.

[0064] It should be noted that an optional washing step can be carried out before or after the neutralization step, on all or part of the pretreated lignocellulosic substrate.

[0065] If washing is applied, a liquid stream is brought into contact with the pretreated lignocellulosic substrate, then the liquid is separated from the solid. The washing step can be carried out by percolation, by successive liquid / solid mixing and separation operations, by washing on a belt filter or by any other technique known to those skilled in the art. The washing liquid used can be water or a process stream. The mass 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 sugary washing juice containing a portion of the hemicelluloses solubilized during the pretreatment. This washing juice can, for example, be used as a carbon source for the production of biocatalysts (enzymes and / or microorganisms). The washing step is generally carried out at a temperature between 10°C and 95°C. Enzymatic hydrolysis step

[0066] The pretreated lignocellulosic substrate, optionally neutralized and washed, is sent to the enzymatic hydrolysis stage of the process.

[0067] The pretreated lignocellulosic substrate which is sent to the enzymatic hydrolysis stage has a dry matter content generally between 20% and 70% by weight.

[0068] The objective of enzymatic hydrolysis is to hydrolyze (depolymerize), by means of biocatalysts, hemicelluloses and cellulose into fermentable sugars, preferably glucose.

[0069] The enzymatic hydrolysis step is carried out under mild conditions, at a temperature temperature of the order of 40°C and 55°C, preferably between 45°C and 50°C and at 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 using enzymes produced by a microorganism. Natural or genetically modified microorganisms, such as fungi belonging to the genera Trichoderma, Aspergillus, Penicillium or Schizophyllum, or anaerobic bacteria belonging for example to the genus Clostridium, produce a cocktail of enzymes containing in particular cellulases and hemicellulases, suitable for extensive hydrolysis of cellulose and hemicelluloses.

[0070] The enzymatic hydrolysis can be carried out in continuous or batch mode, or in fed continuous mode, in one or more reactors. The residence time is between 5 hours and 200 hours and preferably between 24 hours and 120 hours and even more preferably between 48 hours and 120 hours.

[0071] At the end of the step, a hydrolysate containing fermentable sugars is recovered from the bioreactor and is then treated in the fermentation step.

[0072] It should be noted that the hydrolyzate obtained may optionally undergo one or more treatment steps before the fermentation step. For example, this may involve a pH adjustment, a partial purification in order to limit the content of inhibitory compound for the fermentative microorganism, or at least partial separation of the solid residues contained in the hydrolyzate (and thus obtain the unconverted solid residue to be treated according to the invention).

[0073] Fermentation stage of the hydrolyzate. when the conversion of sugars is continued obtained in alcohol(s)

[0074] Depending on the step of the process for producing solvents and / or alcohols, the optionally treated hydrolyzate is sent to the fermentation step allowing the conversion by means of one or more microorganisms of different genera of the fermentable sugars into solvent and / or alcohols of interest. The fermentation methods are known to those skilled in the art and are notably described in document US 8,456,633.

[0075] The term "solvent" is intended to denote organic compounds other than alcohols, for example organic compounds having a ketone function such as acetone.

[0076] The term "alcohol" refers in particular to ethanol, propanol, isopropanol and butanol.

[0077] The natural or genetically modified microorganisms may be chosen, for example, from Saccharomyces cerevisiae, Schizosaccharomyces pombe, Saccharomyces uvarum, Saccharomyces diastaticus, Kluyveromyces fragilis, Candida shehatae, Pichia stipitis, Pachysolen tannophilis or the bacteria Zymomonas mobilis, Clostridium acetobutylicum, Escherichia coli.

[0078] In the context of the invention, the fermentation step makes it possible, for example, to produce ethanol alone or in a mixture with butanol, propanol, isopropanol and / or acetone. For example, the fermentative microorganism may be capable of producing a mixture called "ABE (acetone-butanol-ethanol)" or "IBE (isopropanol-butanol-ethanol)".

[0079] Preferably, the chosen microorganism is a natural or genetically modified yeast of the genus Saccharomyces capable of producing ethanol.

[0080] At the end of the step, a fermentation must diluted in products of interest is recovered.

[0081] According to one embodiment of the method, the hydrolysis and fermentation steps can be carried out at the same time in at least one bioreactor so that the enzymatic hydrolysis and the fermentation are carried out simultaneously according to a method designated by the term "Simultaneous Saccharification and Fermentation (SSF)" or "Simultaneous Saccharification and Fermentation (SFS)" according to English terminology. When the hydrolysis step is combined with the fermentation step, the operating conditions, in particular temperature, can be adapted to adapt to the tolerances of the fermentation microorganism. For example, the temperature can be lowered to between 28°C and 45°C, and preferably between 30°C and 35°C when the fermentation is carried out with a yeast of the genus Saccharomyces.The pH is preferably adjusted between 5 and 5.5 to promote yeast performance.

[0082] The production unit implementing the method according to the invention may comprise, in addition to the installations already described, in situ production units for enzymes and / or yeasts.

[0083] Step of separating the solvents and / or alcohols from the fermentation must

[0084] The process according to the invention finally comprises a step of separating the product(s) of interest from the fermentation must, which is preceded or followed by a step of solid / liquid separation in order to eliminate at least a fraction of the solid matter contained in the fermentation must, and to produce the unconverted solid residue which will be treated (washed) according to the invention.

[0085] Preferably, the step of separating the product(s) of interest, for example ethanol, uses one or more distillations which is a technology well known to those skilled in the art.

[0086] The load: lignocellulosic biomass According to the invention, the feedstock of the process may be a biomass alone or in a mixture. The quantity of water contained in the raw feedstock may be at least 10%, in particular between 10 and 40% by mass. Alternatively, the biomass may be dry, and contain less than 10% by weight of water. The raw biomass is chosen from any type of biomass, preferably from solid biomass, and in particular lignocellulosic biomass. Non-limiting examples of types of biomass include, for example, agricultural residues (in particular straw, corn cobs), forestry residues, forestry products, sawmill residues, dedicated crops, for example short-rotation coppices. Preferably, the raw biomass, also called native biomass, is lignocellulosic biomass. It essentially comprises three natural constituents present in varying quantities depending on its origin: cellulose, hemicellulose and lignin. The lignocellulosic biomass feedstock is preferably used in its raw form, i.e. in the entirety of its three constituents cellulose, hemicellulose and lignin.

[0087] In a preferred embodiment of the invention, the lignocellulosic biomass is chosen from grass biomass, agricultural residues such as straw waste, corn cobs, sugar cane bagasse, forestry or sawmill residues such as wood chips or any other type of woody residue.

[0088] The impregnation fluid: The optional fluid, injected for impregnation, is an aqueous liquid solution containing or not containing 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 between 0.1 and 4, in particular between 0.3 and 2. As acid, it is possible, for example, to use at least one acid chosen from sulfuric acid, hydrochloric acid, nitric acid, oxalic acid. Their content, in the aqueous phase, is preferably between 0.2 and 8% by weight.

[0089] The invention applies in a similar manner to different methods and installations, in particular to: - installations / processes which provide pre-treatment by cooking without prior impregnation with a liquor (autohydrolysis for example), - installations / processes which provide for pre-treatment by cooking with prior impregnation with a non-acidic liquor.

[0090] [Fig.l] represents in a synthetic manner the block diagram of an example of a conversion process of this type not in accordance with the invention, a process which provides for a pretreatment of the biomass including an impregnation with an acid liquor then a cooking / explosion with steam, then an enzymatic hydrolysis followed by an alcoholic fermentation, to transform the biomass into ethanol.

[0091] [Fig.l] therefore represents a biomass conversion carried out in the following way: biomass 1 has been previously conditioned (optional step) then possibly pre-impregnated with a liquor, for example acid (optional step). It is introduced into a cooking reactor for a cooking and steam explosion step 3, the reactor also being supplied with water vapor 2. Note that this can be cooking with steam explosion, or cooking without steam explosion but which generates steam. At the end of cooking step 3, the pretreated biomass 5 is separated from the vapor phase 4a. This vapor phase is mainly made up of water but may contain traces of furfural, 5-HMF and acetic acid. The pretreated biomass 5 proceeds to the enzymatic hydrolysis step 6 in a suitable reactor which is also fed with a suitable enzyme cocktail to convert the cellulose and hemicelluloses into sugars, especially monomeric sugars. The hydrolyzed biomass 7 is then fermented in step 8 by adding yeasts to convert the monomeric sugars into alcohol, especially ethanol. Steps 6 and 8 may or may not be carried out simultaneously, in one or more reactors in series. At the end of the fermentation, the fermentation wort containing the alcohol is treated in a solid / liquid filtration step 10a, by a belt filter or a plate filter for example, and the solid fraction trapped in the solid / liquid separation means of step 10a is then washed in step 10b with a liquid water feed 11. The washing filtrate is denoted 12b. The filtration filtrate is denoted 12a.This step 10b may include repulping or contacting the solid fraction trapped in the solid / liquid separation tool with liquid water 11 followed by solid / liquid separation by filtration for example. “Repulping” or “contacting” means the operation consisting of bringing the fermented biomass or the solid fraction obtained after step 10a) into contact with a washing fluid by suspending the biomass in water.

[0092] Step 10c is a step of compacting the solid fraction trapped in the solid / liquid separation tool after steps 10a and 10b, at the outlet of which a compacting filtering 12c and a washed solid residue also called compact ligneous “washed solid residue” 13 are obtained which is rich in lignin and solids not converted during the enzymatic hydrolysis / fermentation. It may, ultimately, be used as fuel. The heat produced may be used in the process in one or more steps requiring heating a fluid (impregnation liquor), a reactor (cooking during pretreatment) or a reboiler of a distillation column (to purify the alcohol obtained by fermentation, etc.).

[0093] An example of carrying out steps 10a, 10b and 10c is as follows: The separation of the washed solid residue of lignin is preferably carried out by filtration under pressure, with a filter press, with a filtration step itself, under pressure (6-8 bars): filling of the filtration chambers then filtration. A first liquid fraction is recovered, called filtration filtrate, with a very low concentration of solid and rich into fermentation products (ethanol) or sugars. The solid fraction remains trapped between the filter press cloths. The filtration step is carried out at a temperature between 30 and 80°C, preferably between 35 and 50°C. It is followed by a step of washing the solid fraction to increase the recovery rate of fermentation products (ethanol) or enzymatic hydrolysis products (sugars). This washing step is carried out by percolating a washing fluid. This washing fluid, as seen further with figures 2 and 3, consists of water, including, according to the invention, at least 30% of the condensates obtained in the pretreatment step (cooking). A second liquid fraction, called washing filtrate, with a very low concentration of solids and rich in fermentation products (ethanol) or sugars is recovered. The solid fraction remains in the filter chambers and is more depleted in products of interest than the first solid fraction.The temperature of the washing fluid is between 30 and 90°C, preferably between 50 and 80°C.

[0094] This washing step can also be implemented by repulping the solid fraction after the filtration step with the washing fluid, followed by filtration.

[0095] This operation can be followed by a so-called compacting operation: draining the liquid contained in the solid fraction. A compacting filtrate with a very low concentration of solids and sufficiently rich in fermentation products (ethanol) or sugars is recovered. It is then followed by a so-called deconstructing operation to recover the solid fraction, called washed solid residue, depleted in ethanol or sugars, and enriched in unconverted lignin / cellulose / hemicellulose.

[0096] The different filtrates 12a, 12b and 12c are collected and sent to the alcohol purification step 14, which may include at least one of the following treatments: stripping, distillation, dehydration on molecular sieve. This produces a purified alcohol stream 15 (ethanol at least 96% by weight) and vinasses 16. These vinasses 16 are treated in the water treatment step 18, which may include one or more physicochemical treatments, such as evapoconcentration, ultrafiltration, reverse osmosis, and / or biological treatments such as anaerobic digestion to produce biogas. Treated water 19 is obtained which may be recycled in the process.

[0097] If we return to cooking step 3, we therefore have, at the end of cooking, in addition to the pretreated biomass 3, a vapor phase 4a. This is condensed in step 17, by cooling the vapor by heat exchange in liquid phase 4b to heat at least one fluid used in the biomass conversion process. This may involve heating a biomass impregnation liquor (before cooking) or the “wine” obtained after fermentation before distillation. This liquid phase 4b is then sent to water treatment step 18, with the vinasses 16, and therefore contribute to the flow of treated water 19 which leaves it. This steam 4a is therefore only used to exhaust it thermally and then it is directed in liquid form to the final water treatment unit.

[0098] Fig. 2 is a first embodiment of the invention, which modifies the process scheme of the invention as follows: (only what differs from the process shown in Fig. 1 will be described hereinafter for the sake of conciseness). Part of the washing water in step 10b is make-up water 11 as before in Fig. 1, and part is the liquid water 4b resulting from the condensation of the vapor 4a.

[0099] Fig. 3 is a second embodiment of the invention, which modifies the process scheme of the invention from Fig. 2 as follows: (only what differs from the process shown in Fig. 2 will be described hereinafter for the sake of conciseness). The washing water in step 10b here consists entirely of the liquid water 4b resulting from the condensation of the vapor 4a. Embodiments Example 1 (comparative)

[0100] The biomass considered is a lignocellulosic biomass: wheat straw. Its composition is indicated in Table 1 below.

[0101] [Tables 1] Cellulose 33.30% by weight Xylan 21.17% by weight Other hemicelluloses 3.55% by weight Extractives 6.90% by weight Lignin 13.53% by weight Ash 6.59% by weight Acetyls 2.81% by weight Water 12.14% by weight

[0102] The biomass is treated according to the process shown in [Fig.l] (process not in accordance with the invention): 52.2 t / h of crushed biomass 1 enters the process and undergoes pretreatment 3 which consists of: - impregnation with an aqueous solution of sulfuric acid: the impregnation is carried out in the presence of acid liquor heated to 80°C.

[0103] - the introduction of this impregnated biomass into a pressurized reactor ~10 bar heated to 180°C with steam injection 2. - a multi-stage expansion to atmospheric pressure releasing steam 4a and a pretreated biomass 5 having a dry matter content of 45% by weight.

[0104] This separation is carried out by one or more cyclones in order to limit the loss of solids.

[0105] The vapor phase 4a at the outlet of this cyclone is at a pressure of 2.1 bara and a temperature of 123°C. This hot flow is used initially to heat the acid liquor to a temperature of 80°C, (the vapor does not condense completely) and is then used to preheat the fermentation must before the solid / liquid separation step or the filtered wine at the inlet of the distillation step. The condensation and cooling step 17 is therefore carried out by means of an exchanger. The temperature at the outlet of the condensation step is 30°C.

[0106] At the output of the preprocessing step: - The flow rate of condensed vapor phase 4b is 21.4 t / h. - The flow rate of pretreated biomass 5 is 96.1 t / h

[0107] The vapor phase 4a contains in particular acetic acid and furfural which are produced during the pretreatment of the biomass and are due to the degradation of the hemicelluloses and the depolymerization of the acetyl groups.

[0108] The composition of condensates 4b is given in Table 2 below:

[0109] [Tables2] Acetic acid 1.13% by weight Furfural 3.84% by weight Water 95.0% by weight Others (methanol, 5-HMF, formic acid, etc.) 0.03% by weight

[0110] The condensates 4b feed the water treatment unit 18, mixed with other water leaving the process to be purified.

[0111] The pretreated biomass 5 feeds one or more fermentation reactors in order to convert the sugar polymers into monomeric sugars under the action of an enzymatic cocktail (preferably containing cellulases, betaglucosidases, xylanases), then these sugars into ethanol by fermentation with yeasts (Saccaromyces cerevisiae for the production of ethanol).

[0112] This step can be carried out in two sub-steps: a first of liquefaction 6 with a sequential feeding of the biomass allowing to work at high dry matter content. Then a second of enzymatic hydrolysis and fermentation 8 in batch.

[0113] The enzymatic cocktail and the yeasts are preferably introduced into the liquefaction reactor 6. An adjustment of the pH of the medium can also be carried out by adding basic, for example sodium hydroxide or ammonia.

[0114] The fermentation must obtained 9, the composition of which is given in table 3 below, then feeds the solid / liquid separation step 10a.

[0115] The flow rate of fermentation must 9 is 178.4 t / h.

[0116] [Tables3] Ethanol 6.12% weight Glucose 0.12% weight Xylose 0.14% weight Acetic acid 0.52% weight Cellulose 0.66% weight Xylan 0.11% weight Lignin 4.26% weight Water 78.3% weight Others (ash, acetyls, other hemicelluloses) 9.77% weight

[0117] The solid / liquid separation tool used is for example a filter press.

[0118] This solid / liquid separation step comprises a first step 10a of filtration of the fermentation must, followed by a washing step 10b of the remaining solid. The mass ratio between the flow rate of water used for this washing step and the flow rate of solid to be washed (solid trapped in the solid / liquid separation tool after step 10a) is 1.08. This washing step makes it possible to recover the ethanol present in the solid.

[0119] The flow rate of wash water 11 is 50.5 t / h. The recovery rate of ethanol in the wash filtrate 12b is 80.5% by weight.

[0120] The compaction and deconstructing step 10c makes it possible to recover the washed solid residue called washed solid lignin residue 13. The compaction efficiency is 45%, it corresponds to the recovery rate of ethanol in the compaction filtrate 12c compared to the ethanol present in the solid residue after filtration and washing.

[0121] After solid / liquid separation, all of the filtrates 12a, washing filtrates 12b and compacting filtrates 12c are combined. The total flow rate of these filtrates is 196 t / h.

[0122] The flow rate of washed solid residue 13 recovered after this separation step is 32.8 t / h. Its composition is given in Table 4 below:

[0123] [Tables4] Ethanol 0.68% by weight Glucose 0.01% by weight Xylose 0.02% by weight Cellulose 3.66% by weight Xylan 0.58% by weight Lignin 23.2% by weight Water 50.5% by weight Others (ash, acetyls, other hemicelluloses) 21.4% by weight

[0124] All the filtrates, containing mainly water and ethanol, but also the compounds produced during the upstream stages (unconverted sugars, impurities produced by fermentation) feed the atmospheric distillation column 14 in order to separate the ethanol produced. Ethanol 15, whose composition is close to the azeotrope with water, is obtained at the top of the column before being sent to the dehydration section. The other liquid compounds of the process 16 (vinasses) are extracted at the bottom of the column and sent to the wastewater treatment section 18.

[0125] The composition of vinasses 16 is given in table 5 below:

[0126] [Tables5] Acetic acid 0.31% by weight Furfural 0.66% by weight Water 93.45% by weight Others (sugars, extractables, etc.) 5.58% by weight

[0127] The liquid discharges sent to the water treatment unit are therefore: - Condensates 4b at the outlet of the pretreatment section: flow rate of 21.4 t / h - Vinasse 16 from the water / alcohol distillation column: flow rate of 185.4 t / h

[0128] The total flow rate of effluent to be treated is therefore 206.8 t / h. The condensates at the pretreatment outlet therefore represent 10% of the water to be treated in the process. Example 2 (according to the invention)

[0129] In this example, the condensates 4b are directed directly to the washing step of the residual solid 10b) obtained after filtration of the fermentation must, mixed with a flow of washing water 11, as shown in [Fig.2]. In this example, the proportion of condensates 4b relative to the flow 11 of washing water is 74% (volume).

[0130] The temperature at the outlet of the condensation step 17 is 80°C.

[0131] The washing ratio to minimize the loss of ethanol in the washed solid residue of lignin 13 is identical to that of example 1. The flow rate of washing water 11 used in mixture with the condensates 4b for washing the washed solid residue is 29.1 t / h.

[0132] The soluble compounds present in the condensates 4b do not impact the recovery yield of ethanol in the filtrates during the washing step.

[0133] After solid / liquid separation, all of the filtrate 12a, washing filtrate 12b and compacting filtrate 12c are combined. The total flow rate is 196 t / h.

[0134] The operating conditions of step 14 of water / ethanol separation by distillation then by dehydration on molecular sieve are identical to example 1.

[0135] The flow of vinasses 16 extracted at the bottom of the column is sent to the wastewater treatment section 18.

[0136] The total flow rate of effluent to be treated is 185.4 t / h, which represents a 10% reduction in the capacity of the water treatment section compared to example 1. Example 3 (according to the invention)

[0137] In this example, the condensates 4b are directed directly to the washing step of the residual solid 10b) obtained after filtration of the fermentation must. The temperature at the outlet of the condensation step 17 is 80°C.

[0138] The washing of the washed solid residue 13 is carried out only with this condensate flow 4b from the pretreatment 3, as shown in [Fig.3].

[0139] The mass ratio between the flow rate of condensate used for this washing step and the flow rate of solid to be washed is 0.46, i.e. a reduction of 57% compared to examples 1 and 2.

[0140] This washing step allows a recovery rate of ethanol in the washing filtrate 12b of 65% by weight.

[0141] The compacting and deconstructing step 10c makes it possible to recover the washed solid residue of lignin 13. The compacting efficiency is identical to examples 1 and 2, i.e. an ethanol recovery rate of 45% by weight in the compacting filtrate 12c.

[0142] After solid / liquid separation, all of the filtrates 12a, washing filtrates 12b and compacting filtrates 12c are combined. The total flow rate of these filtrates is 167 t / h.

[0143] The flow rate of washed solid residue of lignin 13 recovered after this separation step is 32.8 t / h. Its composition is given in Table 6 below:

[0144] [Tableauxô] Ethanol 1.22% wt Glucose 0.02% wt Xylose 0.03% wt Cellulose 3.62% wt Xylan 0.58% wt Lignin 23.2% wt Water 49.3% wt Others (ash, acetyls, other hemicelluloses) 22.03% wt

[0145] The operating conditions of step 14 of water / ethanol separation by distillation then by dehydration on molecular sieve are identical to examples 1 and 2.

[0146] The flow of vinasse 16 extracted at the bottom of the column is sent to the wastewater treatment section 18.

[0147] The total flow rate of effluent to be treated is 156.6 t / h, which represents a reduction of 15% in the capacity of the water treatment section compared to example 2, and a reduction of 24% in the capacity of the water treatment section compared to example 1.

[0148] The loss of ethanol in the washed solid residue of lignin is increased by 80% compared to examples 1 and 2 by a limited flow rate of washing fluid.

[0149] In conclusion, the invention makes it possible to reduce the water consumption of the washing operation carried out after fermentation, and to in fact reduce the quantity of water to be treated at the end of the conversion process, without affecting the quality of the product obtained, and even making it possible to increase the yield, by exploiting "as is" a condensed water vapor resulting from the cooking of the biomass, which is a solution that is both simple and effective.

Claims

Claims

1. A method of treating a lignocellulosic biomass, said method comprising a) an optional step of impregnating the biomass (1) with a liquor, in particular acidic, to obtain an impregnated biomass, b) a step of cooking (3) the biomass (1), optionally impregnated in step a), in the presence of water vapor (2), for example of the steam explosion cooking type, to obtain a mixture comprising the pretreated biomass (5) and water vapor (4a), c) a step of separating the mixture of pretreated biomass and water vapor to obtain on the one hand the pretreated biomass (5) and on the other hand water vapor (4a), d) a condensation step (17) of the water vapor (4a) from the cooking step b) into liquid effluent comprising mainly liquid water (4b), e) a step of enzymatic hydrolysis (6) of the pretreated biomass (5), to obtain a hydrolyzed biomass (7) in the form of sugar(s), in particular monomeric, f) a fermentation step (8) of the hydrolyzed biomass (7) in the form of sugar(s), in order to obtain a mixture comprising a fermented biomass (9) comprising at least one alcohol in the form of a juice and a solid residue, then at least one treatment step aimed at treating this mixture or one of its components with a view to extracting, isolating and / or purifying the fermented biomass, said treatment step, or at least one of them, comprising at least one step of washing said mixture or said solid residue obtained in step f), said washing step using at least in part the liquid effluent from step d) of condensation.

2. Method according to claim 1, characterized in that it comprises, after the fermentation step f) at least two treatment steps: g) a solid / liquid separation step (10a) of the fermented biomass, in order to obtain a separate juice (12a) comprising at least this alcohol and a solid residue, h) a washing step (10b) of the solid residue with, as washing water, at least in part, the liquid effluent (4b) from the condensation step d) (17).

3. Method according to one of the preceding claims, characterized in that the water vapor (4a) separated in separation step c) is loaded with by-products resulting from the cooking (3) of the biomass from step b), in particular comprising at least one of the following by-products: furfural, sugar degradation compounds such as 5-hydroxymethylfurfural 5-HMF, one or more organic acids such as acetic acid.

4. Method according to claim 2, characterized in that all the liquid effluent (4b) from the condensation step (17) d) is used as washing water in the washing step (10b) h).

5. Method according to one of the preceding claims, characterized in that the washing step (10b) h) uses as washing water only the liquid effluent (4b) from the condensation step d) (17).

6. Method according to one of claims 1 to 4, characterized in that the washing step (10b) h) uses as washing water partly the liquid effluent (4b) from the condensation step d) (17) and partly a supply of other water (11), in particular in a volume proportion of 10 / 90 to 90 / 10.

7. Method according to one of the preceding claims, characterized in that the washing step (10b) h) uses as washing water at least in part the liquid effluent (4b) from the condensation step d) (17), said liquid effluent then being at a temperature between 30 and 60°C and / or at a pH between 2 and 4.

8. Method according to one of the preceding claims, characterized in that the steps (6) of enzymatic hydrolysis e) and (8) of fermentation f) are carried out simultaneously on the pretreated biomass (5).

9. Method according to one of the preceding claims, characterized in that it also comprises: i) a step of separation or purification, in particular distillation, of the fermented biomass, and in that step g) of solid / liquid separation and step h) of washing are carried out before or after said step i) of separation or purification.

10. Method according to one of the preceding claims, characterized in that the condensation step d) (17) is carried out by heat exchange of the water vapor with a fluid used in the method, in order to raise the temperature of said fluid.

11. Method according to one of the preceding claims, characterized in that that step g) of solid / liquid separation (10a) 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, a centrifugation, decantation or wringer device or the combination of at least two of these devices.

12. Installation for implementing the method according to one of the preceding claims, characterized in that it comprises: (a) an optional impregnation device, in particular an impregnation reactor, of the biomass with a liquor, in particular acidic, to obtain an impregnated biomass (1) b) a device for cooking the biomass, optionally impregnated with the impregnation device a), in the presence of water vapour (2), for example of the steam explosion cooking type, to obtain a mixture comprising the pretreated biomass (5) and water vapour, c) a device for separating the mixture of pretreated biomass and water vapour, to obtain on the one hand the pretreated biomass (5) and on the other hand water vapour (4a), d) a device for condensing the water vapor from cooking step b) into liquid effluent (4b), in particular a heat exchanger device, (e) a device for enzymatic hydrolysis, in particular an enzymatic hydrolysis reactor, of the pretreated biomass, to obtain a hydrolyzed biomass (7) in the form of sugar(s), f) a device for fermenting the hydrolyzed biomass in the form of sugar(s), in particular a fermentation reactor, in order to obtain a mixture comprising a fermented biomass (9) comprising at least one alcohol in the form of a juice and a solid residue (13), said device being separate from the enzymatic hydrolysis device or being common with it, then at least one treatment device intended to treat this mixture or one of its components with a view to extracting, isolating and / or purifying the fermented biomass (12a), including at least one washing device using at least part of the liquid effluent (4b) from the condensation step d).

13. Installation according to the preceding claim, characterized in that, downstream of the fermentation device f), it comprises two treatment devices: (g) a device for solid / liquid separation of fermented biomass, in order to obtain a separate juice (12a) comprising at least this alcohol, and a solid residue, in particular a pressing or draining device, such as a filter press or a vacuum filter, a belt filter, a belt press, a centrifuging, decanting or wringing device or the combination of at least two of these devices h) a device for washing the solid residue (13), possibly common with the solid / liquid separation device or separate from it, with, as washing water, at least in part, the liquid effluent (4b) from the condensation device (17) d).

14. Use of the method according to one of claims 1 to 11 for the treatment of lignocellulosic biomasses, such as wood, straw, agricultural residues, paper residues, and all dedicated energy crops, in particular annual or multi-annual plants such as miscanthus, with a view to producing alcohol-type biofuels or bio-sourced molecules.

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