PROCESS FOR THE TREATMENT OF LIGNOCELLULOSE BIOMASS

Description

Technical field

[0001] The invention relates to a method for treating lignocellulosic biomass to produce so-called second generation (“2G”) sweet juices. These sweet juices can be used to produce other products biochemically (for example alcohols such as ethanol, butanol or other molecules, or solvents such as acetone etc.).

[0002] This process involves different stages, generally three stages which are the preparation of liquor, the impregnation of the biomass with this liquor, and the pretreatment of the impregnated biomass by cooking, in particular with steam explosion. Prior art

[0003] 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, etc.

[0004] The process for the biochemical transformation of lignocellulosic into 2G sugary juices includes a pretreatment step and an enzymatic hydrolysis step using an enzyme cocktail. These processes also most often include an impregnation step before the pretreatment. The sugary juices resulting from the hydrolysis are then treated, for example by fermentation, and the process may also include separation steps and / or a purification step for the final product.

[0005] These processes also most often include an impregnation step before pretreatment. The sugary juices resulting from hydrolysis are then treated, for example by fermentation, and the process may also include separation steps and / or a purification step for the final product.

[0006] An example of this sequence of steps for converting biomass into ethanol is described in patent WO 2014 / 135755.

[0007] Lignocellulosic biomass is composed of three main polymers: cellulose (35 to 50%), which is a polysaccharide consisting mainly of hexoses; hemicellulose (20 to 30%), which is a polysaccharide consisting mainly of pentoses; and lignin (15 to 25%), 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.

[0008] Among the three basic polymers that integrate lignocellulosic biomass, cellulose and hemicellulose are those that allow the production of 2G sweet juices.

[0009] Most often, hemicellulose is mainly broken down into monomeric and oligomeric sugars during pretreatment, and the cellulose is converted into glucose by enzymatic hydrolysis. However, access to raw cellulose in the native substrate remains difficult for enzymes, hence the need for pretreatment. This pretreatment makes it possible to modify the physicochemical properties of lignocellulosic in order to improve the accessibility of cellulose to enzymes and its reactivity to enzymatic hydrolysis.

[0010] Many technologies of interest to the invention for carrying out this pretreatment exist, which will be grouped hereinafter under the generic term of "cooking", consisting of heating the biomass at high temperature for a defined duration. In particular, acid cooking is known, where the biomass is brought into contact with an acid solution before / during cooking, alkaline cooking, where the biomass is brought into contact with a basic solution before / during cooking. Also known is cooking (acid, alkaline or without impregnation) called steam explosion, where the biomass is subjected to pressurized water vapor.

[0011] There are also pretreatment processes called "organosolv pulping" according to the known English term (or treatment with organo-solvent in French). This last process involves pretreatment in the presence of one or more organic solvents and generally water. The solvent can be an alcohol (ethanol), an acid such as acetic acid, formic acid, or acetone, or a mixture of these compounds. The "organosolv pulping" processes lead to at least partial solubilization of the lignin, a partial solubilization of the hemicelluloses. There are then two output streams: the pretreated substrate with residual cellulose, hemicellulose and lignin and the solvent phase which contains the solubilized line and part of the hemicelluloses. There is generally a solvent regeneration step which allows the extraction of a lignin stream.Some "organosolv pulping" treatments (particularly with ethanol) can be coupled with the addition of a strong acid (such as H 2 SO 4 ). It is also possible to consider bringing the biomass into contact with the solvent via an impregnation reactor before the cooking phase or to bring the biomass into contact with the acid catalyst before carrying out "organosolv pulping" cooking.

[0012] 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, Renwable Energy 37 (2012) 19-27.

[0013] WO 2016 / 066752 A1 discloses an ignocellulosic treatment process for producing sugars and their fermentation products. It addresses the problem of fouling and blockage of the elements of the installation used for the lignocellulosic treatment process. The process comprises the following steps: a biomass pretreatment step comprising two steps corresponding to the pretreatment steps according to the present application; a fermentation step of the pretreated product, which may include an enzymatic hydrolysis step. The process is characterized in that the product from the pretreatment step is mixed with a portion of the product obtained in the fermentation step before being introduced into the fermentation tank.

[0014] One of the most effective pretreatments is the steam explosion cooking mentioned above, as it allows for 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 / followed by other treatment(s), and it is this which will be of particular interest to the invention, without being limited to it in its application, however.

[0015] It has been shown that lignocellulosic biomass treatment reactors, particularly those involving cooking-type biomass pretreatment, are prone to fouling: heating the reaction medium in the reactor to high temperatures leads to the production of various solid residues that adhere to the internal walls of the reactor. These residues accumulate gradually, over a period longer than the average residence time of the biomass in the reactor. They can gradually cause operational problems, such as a risk of clogging of the reactor outlet, greater difficulty in transporting the biomass within the reactor, and, in general, their presence negatively impacts the reactor's performance.A first solution to eliminate these residues consisted of emptying the reactor, thus shutting it down, and opening it to clean the internal walls of the reactor by mechanical and / or hydraulic action, i.e. by scraping the walls and / or by sending water under pressure of several hundred bars. This procedure is certainly effective, but it consumes time and energy: it requires not only shutting down the reactor, but also waiting for it to cool (cooking is done at a temperature above 100°C and under pressure), then opening it, cleaning it, closing the reactor and bringing it back up to temperature before restarting production.

[0016] The invention then aims to overcome these drawbacks. More specifically, the invention aims to develop an improved biomass treatment process which eliminates, in whole or in part, these residues, or which prevents, in whole or in part, their formation, while limiting any loss of yield / any immobilization of the equipment implementing the process in question as a whole. Summary of the invention

[0017] The invention firstly relates to a method for treating lignocellulosic biomass comprising, successively, b) a pretreatment step by cooking, with or without steam explosion of the biomass previously placed in acidic conditions or at neutral pH in a pretreatment reactor (3), to produce an acidic (MA) or neutral pretreated marc, alternating with b') a pretreatment step by cooking, with or without steam explosion of the biomass previously placed in acidic, neutral or basic conditions, with sufficient introduction into the pretreatment reactor (3) of a basic aqueous solution (EB) at least for the biomass previously placed in acidic or neutral conditions, to produce a basic pretreated marc (MB), then c) a step of enzymatic hydrolysis in a hydrolysis reactor (16) of a mixture of the acidic (MA) or neutral pretreated marc from step b) with the basic pretreated marc (MB) from step b').

[0018] Advantageously, during step c) of enzymatic hydrolysis of the mixture of acidic (MA) or neutral pretreated marc with the basic pretreated marc, said mixture can be replaced by only acidic or neutral pretreated marc for only part of the duration of said step c).

[0019] By "successively" is meant the fact that the stages are stated in the order in which the biomass is treated and moves through the installation, without prejudice to the fact that there may be intermediate, preliminary or subsequent stages in the process to those stated.

[0020] The invention has thus discovered that it is possible to clean and / or prevent fouling of the pretreatment reactor according to the invention by bringing the biomass into contact with a basic aqueous solution (which may also be referred to subsequently as basic "liquor"), for example a solution containing KOH, during the pretreatment of the biomass itself: cleaning is thus carried out while maintaining the supply of biomass to the reactor.

[0021] The cleaning of the reactor is therefore carried out with a reactor at least partially filled with biomass, which may have been pre-impregnated with an acidic, neutral or oxidizing aqueous solution prior to its pretreatment in the reactor in question.

[0022] The basic solution may already be present in the biomass when it has been previously impregnated with a basic solution before its introduction into the pretreatment reactor. Only then, at the level of this reactor, can the necessary base be added, if necessary. If the biomass which feeds the pretreatment reactor is not basic, then the addition of basic solution in the pretreatment reactor will be essential.

[0023] The cleaning according to the invention is carried out by two combined actions: it is firstly chemical, with the action of the basic solution which has proven capable of detaching and / or dissolving the solid residues sticking to the internal walls of the reactor, but it is also mechanical, the biomass particles exerting an abrasive effect, in addition, on said residues.

[0024] This is a process that is much simpler to implement than mechanical or hydraulic cleaning: in fact, it can be carried out without having to open the reactor, since it is sufficient to provide the basic aqueous solution inlets / outlets (or to reuse existing fluid inlets / outlets).

[0025] It is carried out without even having to stop production in pre-treated biomass: surprisingly, it turned out that the presence of biomass had an abrasive effect, therefore positive with regard to cleaning the reactor as mentioned above, but above all it also turned out that the biomass which is in the reactor with the basic solution was exploitable / recoverable: the pre-treatment is also carried out correctly during the cleaning phase, the biomass can be used for the rest of the process, even if it has undergone impregnation in an acidic or neutral or oxidizing solution before its pre-treatment.

[0026] Furthermore, unlike mechanical / hydraulic cleaning with reactor opening, it is not necessary to wait for the reactor to cool down before cleaning. On the contrary, it has even been shown that carrying out cleaning during hot pretreatment, such as cooking (with or without steam explosion) is very favorable for residue detachment. Since the reactor can remain hot during cleaning, there is no need to reheat it, since there is no production shutdown, and therefore no restart to be expected from a thermal point of view.

[0027] On the other hand, it turned out that the basic pretreated marc, that obtained in step b'), reacted significantly less well to the following enzymatic hydrolysis than the conventional acidic or neutral pretreated marc obtained in step b) when used alone. The hydrolysis yield, or the conversion rate to alcohol when the hydrolysis is concomitant with fermentation, are lower. Considering, moreover, that this "basic" pretreated marc had to be eliminated and could not be recovered would also have led to an overall loss of yield of the biomass treatment process.

[0028] The invention then overcame this obstacle, by providing for feeding the hydrolysis reactor not alternately with basic marc and acid / neutral marc, depending on whether the pretreatment is carried out according to step b) or b'), (nor by "removing" the basic marc), but by feeding it with a mixture of "conventional" acid or neutral marc with this basic marc.

[0029] This mixture can be achieved in several ways, either by providing a single buffer zone of basic marc, which is then taken to add it to the conventional acid / neutral marc, or by providing two buffer zones, one for the basic marc, the other for the acid / neutral marc, zones from which given quantities are taken to have the mixture in the desired proportions in the enzymatic hydrolysis reactor.

[0030] It should be noted that enzymatic hydrolysis can be carried out either continuously, by feeding the hydrolysis reactor from the pretreatment reactor, or in "batch", therefore not continuously, and the choice of the way in which the mixing is carried out and the number of buffer zones will also depend on this mode of operation.

[0031] In the case of two buffer zones, one for conventional acid / neutral marc and one for basic marc, different retention times are preferably chosen for the acid / neutral marc and for the basic marc. These buffer zones thus make it possible to decouple the production of pretreated marc during the pretreatment step of the marc feed from the downstream enzymatic hydrolysis step. It thus becomes possible to feed the enzymatic hydrolysis only with a mixture of acid / neutral marc with basic marc, possibly interrupted by feeding only conventional acid / neutral marc when the basic marc has been entirely consumed. Surprisingly, this mode of operation made it possible to preserve the yield of the enzymatic hydrolysis compared to a hydrolysis made 100% from acid / neutral marc, by adjusting the ratios of the two types of biomass in the mixture.The pH of the mixture is thus adjusted, in particular to a level closer to the level most suited to the enzymatic cocktail used, generally to a pH slightly higher than the pH of conventional acidic pre-treated marc (although remaining acidic).

[0032] The invention therefore makes it possible to guarantee a longer operating time of the pretreatment reactor by slowing down its fouling, without however negatively impacting the yield of the stages following the pretreatment, in particular the enzymatic hydrolysis, whereas one might have thought that the “basic” pretreated marc would not be recoverable or would disrupt these following stages, and this by combining two characteristics: a pretreatment which periodically switches to basic pH rather than to acid or neutral pH, associated with a specific management of the supply of pretreated marc (acid / neutral or basic) of the enzymatic hydrolysis adapting to this basic marc.

[0033] It should be noted, of course, that, at the outlet of the pretreatment reactor, when switching from step b) in acid / neutral conditions to step b') in basic conditions in the pretreatment reactor, the pretreated marc at the outlet of the reactor does not switch abruptly from an acid / neutral marc to a basic or less acidic marc: for a certain period of time, a so-called "transition" marc is drawn from the pretreatment reactor, the pH of which increases progressively. Similarly, when switching back from a pretreatment in basic conditions of type b') to a pretreatment in acid / neutral conditions of type b), there is again, for a certain period of time, at the outlet of the reactor another so-called "transition" marc, the pH of which, this time, decreases progressively.We can therefore arbitrarily choose, in each case, a threshold value, in particular pH or representative of the pH, of the pretreated biomass at the outlet of the pretreatment reactor to consider whether we are dealing with an acid / neutral type marc or a basic type marc.

[0034] Advantageously, the mixing of the acidic or neutral pretreated marc from step b) with the basic pretreated marc from step b') in step c) is carried out upstream of the hydrolysis reactor, or directly in the hydrolysis reactor.

[0035] In the first case, it is thus possible to mix, in step c), the acidic or neutral pre-treated marc from step b) with the basic pre-treated marc from step b') by taking samples from one or more buffer zones, as mentioned above. These buffer zones are temporary storage areas, which can take the form of storage tanks or other storage means, such as a hopper.

[0036] As explained above, step b') of pretreatment of the biomass with sufficient introduction, if necessary, into the pretreatment reactor of a basic aqueous solution (EB), to produce basic pretreated marc is a step of cleaning the pretreatment reactor, while continuing to produce marc, with characteristics, in particular pH, which are different however.

[0037] Preferably, a step is provided for adjusting the pH of the pretreated biomass or the mixture of pretreated biomasses before or during step c) of enzymatic hydrolysis, in particular an adjustment of the pH between 4 and 6. When dealing with acid / neutral marc, it is generally sufficient to adjust the pH upwards to this pH range by adding base. When dealing with a mixture of marc including basic marc, the pH can be adjusted solely by adjusting the relative quantity of the two types of marc in the mixture, or by additionally providing an addition of base / acid if necessary to reach the desired pH range. This pH adjustment towards acidic pHs but lower than the pHs encountered in pretreatments under acidic conditions (where the biomass can "drop" to pH values of 2 to 3.5) is in fact generally favorable to the activity of cellulase-type enzymes used in enzymatic hydrolysis.

[0038] Advantageously, over a given production time, the sum of the durations of the pretreatment steps b) of the biomass previously placed in acidic or neutral pH conditions in a pretreatment reactor, to produce an acidic or neutral pretreated marc, is greater, in particular at least 2 to 5 times, and preferably between 5 and 20 times greater, than the sum of the durations of the pretreatment steps b') of the biomass previously placed in acidic, neutral or basic conditions, with possible sufficient introduction into the pretreatment reactor of a basic aqueous solution, to produce a basic pretreated marc.

[0039] According to one variant, the biomass feed rate of the pretreatment reactor of pretreatment step b) is the same as the feed rate of step b'). According to another variant of the invention, the biomass feed rate of pretreatment step b) is greater than the biomass feed rate of step b'). Thus, over a given duration, the ratio of the sum of the quantities of biomass treated according to step b) to the quantities of biomass treated according to step b') is preferably greater than the ratio of their respective production times.

[0040] According to the invention, it is therefore preferable to have pretreatments in basic conditions that are shorter than those in acid / neutral conditions, both operation by operation and over the entire production duration (which is understood as the duration between the start-up of the installation and its shutdown, in particular for maintenance reasons): the pretreatment in acid / neutral conditions preferably remains largely in the majority in duration, that in basic conditions being carried out essentially only for reasons of cleaning the pretreatment reactor and is limited to the time just necessary for this.

[0041] Advantageously, a separation between biomass and aqueous phase in liquid or vapor form can be carried out at the outlet of the pretreatment reactor by a separation device or several separation devices in parallel, in particular two separation devices, operating alternately.

[0042] According to the invention, optionally, each step b') of pretreatment of the biomass previously placed in acidic, neutral or basic conditions, with sufficient introduction, where appropriate, into the pretreatment reactor of a basic aqueous solution, to produce a basic pretreated marc, is followed by at least one rinsing of the separation device or one of the separation devices with an aqueous solution (E), in particular between 1 and 10 successive rinsings.

[0043] According to a particular embodiment, several separation devices can be used in parallel operating alternately, at the outlet of the pretreatment reactor, and, in this case, one of the separation devices can be rinsed discontinuously while the other separation device(s) continue to operate.

[0044] Advantageously according to the invention, during step c) of enzymatic hydrolysis in the hydrolysis reactor, the mixing of the acidic or neutral pretreated marc MA from step b) with the basic pretreated marc MB from step b') is done in a ratio MA / MB by weight of at least 80 / 20 expressed in gross weight, in particular a marc MA content greater than 85% by weight, and preferably 90% by weight or 95% by weight, expressed in gross weight of the mixture of marcs and / or a basic marc content of at least 3%, in particular at least 5% or 8% or 10%, in particular between 5 and 15%.

[0045] Enzymatic hydrolysis can be carried out in different ways: this step can be carried out in batch mode (discontinuous), in fed-batch mode (or "fed-batch" according to English terminology) or continuously. For example, enzymatic hydrolysis can be carried out with an initial batch phase in which the basic pomace MB is introduced in a mixture with acidic / neutral pomace MA into the hydrolysis reactor, this introduction being followed by adjustment to the appropriate pH with a neutralization solution, followed by the introduction of the enzymes. This initial batch phase can be continued by a fed-batch phase of pomace, which can be carried out by feeding with acidic / neutral pomace MA only, or by a mixture of acidic / neutral pomace MA with basic pomace MB. At the end of the fed-batch feeding, hydrolysis can be continued in batch mode for a determined period, before emptying the entire reactor at the end of the reaction.

[0046] Preferably, the pretreatment step b) is preceded by a step a) of impregnation in a biomass impregnation reactor with an acidic or neutral aqueous solution.

[0047] The invention also relates to a lignocellulosic biomass treatment plant (in particular for implementing the method described above), and which comprises, from upstream to downstream: a biomass impregnation reactor in fluid connection with a tank for preparing an acidic aqueous solution, a reactor for pre-treatment of the impregnated biomass in fluid connection with a tank for preparing a basic aqueous solution, a device for separating the pre-treated biomass downstream of the pre-treatment reactor, which is optionally associated with means for rinsing with an aqueous solution and which is in fluid connection with optionally an intermediate storage zone for biomass impregnated with an acidic aqueous solution, and another intermediate storage zone for biomass impregnated with a basic solution, and an enzymatic hydrolysis reactor supplied with pre-treated biomass from at least one of said storage zones.

[0048] The terms "upstream" and "downstream" are understood in terms of the general direction of the biomass flow through the facility.

[0049] The installation may also include a zone for adjusting the pH of the biomass between at least one of the storage zones and the enzymatic hydrolysis reactor, in particular a common pH adjustment zone for the biomasses from the storage zones.

[0050] Advantageously, according to one variant, this pH adjustment zone can be a tank ensuring the mixing of biomass from each of the storage zones.

[0051] According to another variant, the pH adjustment is done in the hydrolysis reactor before or during the enzymatic hydrolysis step.

[0052] The mixing of the marcs can be done directly in the enzymatic hydrolysis reactor or before their introduction into the reactor.

[0053] According to a variant, the acid / neutral marc and the basic marc are introduced by the same introduction system into the enzymatic hydrolysis reactor, this system also being able to be used for the introduction of the mixture of acid / neutral and basic marc.

[0054] According to another variant, two different marc feeding systems are provided depending on whether the feeding is carried out with acid / neutral marc or with basic marc or marc mixture).

[0055] Details are given below on how to carry out the possible impregnation, the pretreatment and the separation after pretreatment according to the invention: (step b') of pretreatment under basic conditions may also be designated by the expression step of cleaning the pretreatment reactor: they correspond to the same step).

[0056] Advantageously, it is possible to heat the basic aqueous solution before its introduction into the pretreatment reactor, in particular to a temperature of at least 40°C, in particular at least 80°C. It has been found that the basic solution is effective more quickly if it is thus preheated outside the reactor.

[0057] Advantageously, the introduction of the basic solution into the pretreatment reactor can be carried out in the pretreatment reactor whose internal volume is at a temperature of at least 120°C, in particular at least 140°C. This internal temperature of the reactor can be that at which the pretreatment is carried out conventionally, in particular by cooking. The effect of the basic solution on the solid residues stuck to the walls of the reactor is in fact amplified when the solution / reactor are hot.

[0058] According to one embodiment of the invention, the biomass is introduced into the pretreatment reactor by a pressurized feed means, such as a conical screw conveyor, which is washed with an aqueous solution, and this washing solution is recycled to prepare the basic aqueous solution used during the cleaning of said reactor. This reduces the increased water consumption of the pretreatment process due to the use of a basic aqueous cleaning solution.

[0059] Preferably, the cleaning phase of the pretreatment reactor with the basic solution has a duration of between 15 minutes and 8 hours, in particular between 1 and 3 hours. This duration is therefore not very long, and can be modulated according to the frequency with which the reactor is cleaned.

[0060] During the cleaning phase of the pretreatment reactor, the flow rate of the basic aqueous solution entering said reactor is preferably adjusted so that the dry matter (DM) content of the biomass decreases significantly during its passage through the reactor, for example from a value of 30 to 60% DM, in particular 50% DM, to a value of 15 to 25% DM, in particular 25% DM. Indeed, the basic aqueous solution will have a first role, which is to impregnate the biomass entering the reactor with water until the biomass is saturated with liquid.

[0061] Throughout this text, the acronym "MS" refers to the dry matter content which is measured according to ASTM E1756 - 08(2015) "Standard Test Method for Determination of Total Solids in Biomass".

[0062] Then, and this is its second role, the base concentration (KOH for example) of the basic aqueous solution is preferably adjusted so as to increase the pH of the biomass entering the reactor from an acid pH range of between 0.5 and 3, preferably in the vicinity of 3, to a basic pH range of between 8 and 14, preferably in the vicinity of 13. (This is then the case of pre-treatment of a biomass pre-impregnated with an acid liquor, and which must therefore be switched to a basic pH to carry out the cleaning according to the invention.)

[0063] By adjusting the flow rate and the base concentration of the solution, it is possible to saturate with water and raise the pH of the biomass, the precise quantities of basic solution consumed during cleaning naturally depending on the size of the reactor and the characteristics of the biomass entering the reactor.

[0064] Preferably, the filling rate of the reactor with biomass during the treatment is between 20 and 80% or 90%. During the cleaning phase, this filling rate can be maintained within this range, and even, preferably, (slightly) increased (for example by reducing the rotation speed of the screw or at least one of the internal conveying screws of the reactor when it has them), which tends to improve the quality of the cleaning. The continuous cleaning phase of the pretreatment reactor is carried out according to a given frequency and / or when a threshold value of a physicochemical or rheological characteristic of the reaction medium in said reactor is exceeded. This characteristic can be measured or evaluated directly or indirectly.This may be, for example, a power threshold of the motor used to turn a conveyor screw in the reactor, to turn stirring means in the reactor or any other moving part in it.

[0065] According to one embodiment, one of the physical, chemical or rheological characteristics or the nature of the biomass feeding the pretreatment reactor can be changed during at least part of its cleaning phase. Indeed, it may be advantageous, during cleaning, to feed the pretreatment reactor with a biomass with a higher abrasive power than the biomass used during the rest of the production time. For example, it is possible to replace straw-type biomass during production with poplar-type biomass during cleaning.

[0066] Advantageously, the pretreatment is, according to the invention, cooking with steam explosion. The heat of the recovered steam can then be thermally exhausted, in particular in a cyclone-type separation device at the outlet of the pretreatment reactor, to heat the or one of the aqueous solutions used in said process.

[0067] Pretreatment can be carried out by cooking, with or without steam explosion.

[0068] According to a preferred embodiment, the biomass is impregnated with an acidic aqueous solution in an impregnation reactor, before its introduction into the pretreatment reactor. The two reactors can be connected in series and operated continuously. The fact that, temporarily, the acidified biomass is brought into contact with a basic solution in the pretreatment reactor did not significantly affect the quality or yield of the pretreated biomass production: even if the biomass pretreated during cleaning may present differences with the biomass pretreated outside cleaning, in particular pH values which increase then gradually decrease again, it remains exploitable, insofar as, as explained above, it is combined in appropriate proportions with biomass pretreated under acid / neutral conditions before enzymatic hydrolysis.

[0069] According to one embodiment, during at least part of the continuous cleaning phase of the pretreatment reactor, the acid content of the acidic aqueous solution brought into contact with the biomass during its prior impregnation in the impregnation reactor is reduced or eliminated. It is thus possible to reduce the quantity of base necessary for the preparation of the basic cleaning solution, since the quantity of acid contained in the biomass to be neutralized will thus be lower.

[0070] According to another embodiment, during at least part of the continuous cleaning phase of the pretreatment reactor, the acidic aqueous solution brought into contact with the biomass, during its prior impregnation in the impregnation reactor, is replaced by a basic aqueous solution, in particular the same as that which is injected during said phase into the pretreatment reactor: it is thus possible to further reduce the base consumption necessary for cleaning compared to the previous embodiment. It can also be replaced by an aqueous solution of neutral pH, always for the same reason.

[0071] According to one variant, several, in particular two, impregnation reactors are used in parallel to impregnate the biomass with an aqueous solution before its introduction into the pretreatment reactor: a first impregnation reactor is supplied with an acidic aqueous solution, and a second impregnation reactor is supplied with a basic aqueous solution or an aqueous solution of neutral pH, the two reactors operating alternately, the second reactor being operational during at least part of the cleaning phase of the pretreatment reactor. This variant makes it possible to implement the previous embodiments, by modifying the type of impregnation of the biomass before its pretreatment when the pretreatment reactor switches to cleaning mode, by switching the arrival of biomass to be impregnated from one impregnation reactor to the other.

[0072] Preferably, a separation between biomass and aqueous phase in liquid or vapor form can be carried out at the outlet of the pretreatment reactor, by a separation device or several separation devices in parallel, in particular two separation devices, operating alternately. This may be cyclone-type equipment.As previously for the two impregnation reactors in parallel, using several separation devices in parallel makes it possible to reduce the transition period between production mode and production mode + cleaning of the pretreatment reactor: with two devices in parallel, one of the two devices can be dedicated to the separation of the “basic” pretreated biomass (that pretreated during cleaning), by separating only the biomass pretreated during cleaning, and the other device is then dedicated to the conventional separation of the biomass pretreated with acid or neutral impregnation (that pretreated outside the cleaning period).

[0073] The installation according to the invention may comprise two impregnation reactors and / or two separation devices and / or two pretreatment reactors operating alternately depending on whether the pretreatment is carried out on biomass previously placed in acidic conditions or at neutral pH to produce an acidic or neutral pretreated marc, according to step b), or on biomass previously placed in acidic, neutral or basic conditions, with sufficient introduction into the pretreatment reactor of a basic aqueous solution (EB), to produce a basic pretreated marc according to step b').

[0074] The implementation of the proposed invention therefore simply adds to an existing installation, in its simplest embodiment: possibly a tank for preparing the basic solution, which can be supplied with water, and concentrated base (KOH, NaOH for example, or any other mineral or organic base), and possibly recycled water / basic solution. This tank is equipped with known means for, in particular, maintaining the pH of the solution constant, by adding base (KOH) and / or water. The tank can also be equipped with heating means to bring / maintain the basic solution to the desired temperature before introduction into the reactor.The heating means may, alternatively or cumulatively, be provided on the fluid connection means, such as pipes, bringing the basic solution from the tank to the reactor, means for mixing the marc pretreated under acid / neutral conditions and the marc pretreated under basic conditions (a “buffer” zone for intermediate storage of basic marc, possibly another for storing acid / neutral marc; or even a third for mixing and pH adjustment before sending to the hydrolysis reactor). The buffer zone(s) may be in the form of tanks or in the form of any other known means of intermediate storage, such as a hopper for example.

[0075] The invention also relates to the use of the method or installation described above for the treatment of biomasses such as wood, straw, agricultural residues, and all dedicated energy crops, in particular annual or multi-annual plants such as miscanthus, with a view to producing sugars, biofuels or bio-sourced molecules.

[0076] The invention also relates to a method for treating lignocellulosic biomass comprising the following steps: the preparation of an impregnation liquor containing a catalyst, in particular an acid, the introduction of the biomass into an impregnation reactor to be impregnated by the impregnation liquor, the transfer of the impregnated biomass into a pretreatment reactor to undergo pretreatment by cooking, the enzymatic hydrolysis of the pretreated biomass, the alcoholic fermentation of the enzymatic hydrolysis must obtained, such that the process is carried out continuously over all or part of said steps, and such that the impregnation reactor is cleaned without interrupting its production of pretreated biomass.

[0077] The installation in question may use two impregnation reactors and / or two separation devices and / or two pretreatment reactors, operating alternately depending on whether the pretreatment reactor is in the cleaning phase or not.

[0078] The invention also relates to any installation for implementing the biomass treatment method mentioned above, such that this installation comprises, successively: an impregnation reactor supplied with impregnation solution by a tank for preparing said solution, and with biomass, a reactor for pre-treatment of the impregnated biomass which can be supplied with basic aqueous solution by a tank for preparing said solution, an enzymatic hydrolysis reactor, and an alcoholic fermentation reactor which can be the same as the hydrolysis reactor, all of the reactors being connected in series, or at least two of them.

[0079] Note that hydrolysis and fermentation can also be carried out at the same time in the same reactor. List of figures

[0080] There figure 1represents the block diagram of an embodiment of a method for treating lignocellulosic biomass according to the invention. The figure 2 represents a portion of the installation capable of implementing the process according to the figure 1 . There figure 3 represents the installation implementing a first variant of the first sequence T1 of the method according to the invention represented in figure 1 . There figure 4 represents the installation implementing a second variant of the first sequence T1' of the method according to the invention represented in figure 1 . There Figure 5 represents the installation implementing a first variant of the second sequence T2 of the method according to the invention represented in figure 1 . There figure 6 represents the installation implementing a second variant of the second sequence T2' of the method according to the invention represented in figure 1 . There figure 7represents a graph tracking ethanol production according to an example not in accordance with the invention. The figure 8 represents an ethanol production monitoring graph according to an example in accordance with the invention. The figure 9 represents an ethanol production monitoring graph according to an example in accordance with the invention. The figure 10 represents an ethanol production monitoring graph according to an example in accordance with the invention. The figure 11 represents a graph for monitoring ethanol production according to an example in accordance with the invention. Description of the embodiments

[0081] THE figures 1 to 5 are very schematic, the same references correspond to the same components from one figure to another. The figure 1is a block diagram. In the following figures, the reactors and other equipment are shown in the spatial position they substantially occupy in the operational position, without details or equipment of lesser importance in view of the invention.

[0082] The process for treating lignocellulosic biomass, including the continuous cleaning of a biomass pretreatment reactor under basic conditions alternating with conventional pretreatment under acidic or neutral conditions, is illustrated here in the context of a biomass treatment process intended to produce alcohols, in particular biofuel of the bioethanol type. The main stages of this process are described in figure 1 , briefly described below. An embodiment of this method is described in more detail, for example, in patent WO 2018 / 015227 to which reference will be made as needed.

[0083] It should be noted that the method of the invention can be applied in the same way to any pretreatment followed by enzymatic hydrolysis of biomass, and to any reactor which is intended to treat lignocellulosic biomass.

[0084] The biomass treatment process taken here as an example and represented in the figure 1 schematically comprises the following main stages: a first stage of impregnation of the biomass in a vertical reactor, followed by a stage of pretreatment of the biomass once impregnated in a horizontal steam explosion reactor 4, then a stage of enzymatic hydrolysis then alcoholic fermentation (hydrolysis and fermentation can be carried out simultaneously in the same reactor or one after the other), then fractionation by distillation. It is in this succession of stages that the invention fits, as shown in figure 1 described below.

[0085] The references of the figure 1correspond to the following equipment and components, from upstream to downstream, in the biomass processing facility: 1: native biomass (i.e. before any treatment) 2: conditioning of the native biomass (crushing, destoning, possible dust removal, etc.) 3: contact zone of the conditioned biomass with an acidic liquor (aqueous phase) (impregnation) 4: acid liquor (H 2 SO 4 in aqueous phase) 5: pretreatment reactor by cooking - continuous operation 6: steam injection - continuous operation 7: injection of basic aqueous solution - operates during sequence T2 only (detailed later) 8: cyclone-type separation equipment - operates continuously 9: vapors separated from the pretreated biomass substrate - continuously evacuated 10: outlet of the marc produced under acidic conditions - operates during sequence T1 only (detailed later) 11: acid marc buffer zone,fed only during sequence T1 and drawn off during T1 and during T2 12: outlet of the marc produced under basic conditions - operates during sequence T2 only 13: buffer zone of basic marc, fed only during sequence T2 and drawn off at least in part during T1 14: zone of neutralization of the marc to reach a pH between 4 and 6 15: neutralization solution 16: enzymatic hydrolysis reactor 17: cocktail of enzymes and other necessary nutrients + pH readjustment 18: ethanolic fermentation zone (separate or concomitant with hydrolysis) - CO 2 outlet not shown 19: yeasts for fermentation and other necessary nutrients + pH readjustment 20: ethanol recovery device, for example a distillation 21: ethanol product 22: residues (solid and liquid, in mixtures or separated according to the arrangement of 20),

[0086] Let's take it back figure 1by first describing the conventional steps of the process: The native biomass 1 is first conditioned in step 2, in particular to give it a given particle size (crushing), to remove stones and other components which are not part of the biomass itself. Then it is impregnated with an acidic aqueous solution 4 in an impregnation reactor 3. The acid-impregnated biomass is then brought into a high-temperature pretreatment reactor 5 with steam injection 6 to undergo steam explosion cooking. A vapor phase 9 is then separated from the pretreated biomass also called marc, here an acid marc MA therefore, in a cyclone-type separation equipment 8.Then, this acid marc is brought into a neutralization zone 14 to adjust the pH to a slightly higher value, to go from a pH of the order of 2 to 3.5 to a pH of the order of 4 to 6 by adding a neutralizing agent 15, then this neutralized marc MN undergoes enzymatic hydrolysis in an ad hoc reactor 16 supplied with an appropriate enzymatic cocktail 17, then an ethanolic fermentation 18 (which can be concomitant with the hydrolysis), in the same reactor or in a separate reactor, with the addition of appropriate fermentation yeasts 19. Finally, it is planned to recover the alcohol 21 by separating it from the solid and liquid residues 22 in a device 20, which can be a distillation column.

[0087] Let us now describe what the invention brings to this succession of conventional steps: The invention proposes operation in two sequences T1 and T2 which alternate. The T1 sequence is the conventional sequence, also illustrated by the figure 2, with, at the outlet of the pretreatment reactor 4, an acid marc 10, but here this marc MA, instead of being sent directly to the neutralization zone 14 after separation in the separation device 8, passes through a buffer zone 11 of acid marc 10, a hopper for example, which is only supplied with marc during the sequence T1. Sequence T2 is the sequence where the pretreatment reactor is supplied with basic aqueous solution 7, in particular by a preparation tank connected to the pretreatment reactor 5, from which a basic marc 12 is then drawn, which supplies a buffer zone 13 of basic marc 12 (or MB). The neutralization zone 14 is supplied independently of the sequences T1 and T2. During a sequence T3, it is supplied only with acid marc 10 coming from the buffer zone 11 and / or directly with the marc at the outlet of the reactor 10 when the latter is operating according to the sequence T1.During a T4 sequence, it is fed with a mixture of acid marc 10 (or MA) from zone 11 and basic marc 12 (or MB) from zone 13, according to a defined proportion. The neutralization to be carried out in zone 14 is then less important than during the T3 sequence, since the marc mixture is at a higher pH than that of the acid marc alone, it may even be necessary to no longer carry out neutralization by adding base at this stage. The following steps remain unchanged. Alternatively, if the ratio between the two types of marc in the mixture is chosen accordingly, it is possible to "bypass" the neutralization zone 14 during the T4 sequence and directly inject the marc mixture or each of the marcs separately from their respective buffer zones into the enzymatic hydrolysis reactor 16.

[0088] In an alternative implementation, the neutralization zone 14 can be located in the enzymatic hydrolysis reactor 16. The latter then receives the grounds and the neutralization solution 15 in addition to the enzymatic solution 17.

[0089] The installation capable of implementing the invention according to the method of the figure 1 , up to the separation step with the device 8, is shown in figure 2 : These steps of the process are carried out continuously and are detailed below using the description of the equipment used to implement it: A preparation tank 31 for an impregnation liquor containing a chemical catalyst is provided, which is made up of water E and catalyst A which feed it, the catalyst being in this case a strong acid of the concentrated sulfuric acid type in aqueous phase, this tank making it possible to feed the impregnation reactor 3 with a mixture of water E and chemical catalyst A, A conical screw 2a (also called in English terminology "plug screw" or "sealing screw") for feeding fresh biomass 1 (here wheat straw) into the impregnation reactor 3, A supply of impregnation liquor to the reactor connecting the liquor preparation tank 31 and the impregnation reactor 3, An impregnation reactor 3 equipped with two ascending transport screws (not shown) allowing the biomass to pass from the impregnation zone in the lower part of the reactor to the drainage zone in the upper part of the reactor,and to bring the impregnated and drained biomass to the reactor outlet located at the top of the reactor. This impregnated and drained biomass is then sent to pretreatment by a feed opening into a second conical screw 2b. This second conical screw 2b feeds impregnated biomass to the pretreatment reactor 5, The pretreatment reactor 5 treats the impregnated biomass by steam explosion, A water circuit for washing the conical screws 2a, 2b of the impregnation reactor 3 and the pretreatment reactor 5, symbolically represented in the , figure 1 by water inlets E at the level of said screws, a means of separation of the steam 8 is provided is supplied by the reactor 5 with biomass having undergone cooking by steam explosion, of the cyclone type for example, with steam V at the top outlet and pretreated / exploded biomass at the bottom outlet, also called acid must (or acid marc) MA.

[0090] This MA marc at this stage has sufficient cellulose accessibility to enzymes to be treated by enzymatic hydrolysis for the production of 2G sugars. The conditions of enzymatic hydrolysis and subsequent or simultaneous fermentation which follow this separation (not shown in the figure 1 ) are adapted to the desired products and are known to those skilled in the art.

[0091] The use of the pretreatment technique described above leads to the deposition of different types of biomass (wheat straw here, but also miscanthus, poplar, etc.), which accumulate / adher to the surface of the screw 2b and the pretreatment reactor 5. These deposits undergo cooking for longer times than the normal residence time of the biomass in the reactor, and are transformed into a residue, which can be called here "coke". This "coke" can create various operating problems, such as blockages of the outlet orifice of the reactor 4, an increase in the friction of the screw 2b on the wall of the enclosure in which it is housed, and this can result in a reduction in the performance of the pretreatment unit as a whole as shown in figure 1 .

[0092] Defining the composition of "coke" has proven to be tricky, as it is a residue whose appearance and composition change over time: at the beginning of a production cycle, the material that is deposited is biomass, so it has essentially the same characteristics as the biomass that continues its journey through reactor 4 and towards the downstream stages. The deposit that forms by adhering to the internal wall of reactor 4 will remain under the cooking conditions (temperature in particular) for a much longer time than desired. The effect of temperature affects the composition and morphology of the residue, which will evolve into an increasingly "cooked" residue. The more the residue is "cooked", the more compact it is and the more it adheres to the walls of the reactor.

[0093] These "coke" deposits are cumulative: the longer the continuous operation time of the tool, the greater the quantity of coke deposited, and the more the "layers" of coke close to the wall will evolve into a very hard solid. These deposits therefore cause a fouling phenomenon, increasing the thickness of the walls and reducing the useful volume of the reactor. Depending on the configuration of the cooking reactor, and in particular the type of internals in place, there may be a hindrance to the rotation of certain elements such as the biomass conveyor screw during cooking. This hindrance is observed in particular by an increase in the power of the motor rotating the screw.

[0094] Throughout production, it may also happen that part of this residue, more or less hardened, detaches from the reactor wall, for example due to the rotation of the screw or the passage of the biomass through the reactor: thus, particles with a density much higher than the biomass bed being cooked may be caused to detach and be carried towards the reactor outlet, which can cause blockages or operational problems downstream. Despite these detachments, it is observed that the deposits continue to increase over time during a given production cycle.

[0095] After stopping, cooling and opening the cooking reactor 4, it was found that the coke is in two forms: a hard form in direct contact with the internal walls of the reactor and a more friable form which covers the hard coke. The difference between these two cokes is found in their elemental compositions, as shown in Table 1 below. Crumbly Coke Hard Coke Carbon content (%) 44,57 65,07 Hydrogen content (%) 5,85 4,67 Oxygen content (%) 34,63 24,58

[0096] It is found that the percentage of carbon contained in hard coke is higher than that in friable coke, while an inverse trend is noted for the oxygen content, and similar values for the hydrogen content. It appears that friable coke is in some way the precursor of dense coke.

[0097] The invention consists of continuing the operation of the two impregnation reactors 3 and pretreatment 5, while carrying out chemical cleaning of the reactor 5 in order to extract this coke C and / or to slow down its formation, without “losing” the must produced during this cleaning under basic conditions.

[0098] This cleaning does not require opening the reactor and mechanically cleaning the inside of the reactor as was previously the case. This cleaning according to the invention, detailed below, is therefore faster, more economical and safer, since it limits the operational risks linked to the assembly and disassembly of the unit, and, above all, since it allows production to continue.

[0099] An example of implementation of the method according to the invention requires the following additional equipment, compared to that already described, in view of the figure 1 : A preparation tank 51 for a cleaning liquor / basic liquor EB containing a base. This tank 51 is used to supply the pretreatment reactor 5 with a basic solution at a certain concentration. It is supplied with water E and base B (for example, a base B in the form of a concentrated aqueous solution of KOH), the addition of which is adjusted to obtain a liquor at the desired base concentration and pH.A cleaning liquor supply for reactor 5 connecting the cleaning liquor / basic liquor preparation tank 51 and the pretreatment reactor 5 to be cleaned, preheating it if necessary by ad hoc equipment (heating resistors surrounding the pipes for example), with equipment suitable for injecting the cleaning liquor into the reactor 5 under pressure, An optional rinsing water inlet ER for the cyclone 8 Also provided, but not shown, are one or more temporary storage tanks or hoppers or other temporary storage means, the “buffer zones” mentioned above capable of recovering, in one of the tanks, the conventional acid marc MA, and in the other tank, the basic marc MB obtained during the cleaning under basic conditions of the pretreatment reactor 5.

[0100] The sequence of an exemplary embodiment of the cleaning method / sequence T1 according to the invention comprises two consecutive sub-sequences: Sub-sequence 1: Injection of the preheated basic liquor EB into reactor 5 during the feeding of the reactor with the acid biomass.

[0101] The conditions for injection are as follows: the basic solution EB is an aqueous solution of KOH, with a KOH concentration of 1 to 50% by weight of KOH, preferably 5 to 12% by weight of KOH, relative to water the flow rate of the EB solution in the reactor is between 100 and 500 kg / h, in particular approximately 300 kg / h the filling rate of the reactor 4 with the EB solution is 20 to 50%, in particular approximately 30% the temperature at which the EB solution is injected into the reactor 4 is between 80°C and 200°C, in particular approximately 130°C the temperature of the reactor 4 is between 150 and 220°C, in particular approximately 200°C the duration of this sequence is between 15 minutes and 8 hours, in particular 2 hours the residence time of the EB solution in the reactor 4 is between 5 and 15 minutes, and in particular approximately 10 minutes. Sub-sequence 2 (optional): Cleaning of cyclone 8 by carrying out a rinse with ER water to complete the cleaning.We can talk about "water flushing", insofar as the rinsing consists, in this example of realization, of projecting water under pressure into the cyclone, water which is then quickly evacuated.

[0102] The operating conditions of this sequence, if carried out, are as follows: number of rinses: from 1 to 10, for example equal to 2 temperature of the rinse water: 20°C to 80°C, for example 20°C (therefore either a temperature at or close to ambient, or a higher temperature requiring preheating of the rinse water ER)

[0103] In the cleaning phase = sequence T2, we obtain at the outlet of cyclone 8 a must which is no longer the conventional acid MA must, but a basic MB must.

[0104] The frequency of the cleaning procedure / sequence 2 can vary widely depending on the type and size of the pretreatment reactor 5, the type of biomass processed, etc. For example, cleaning can be triggered when the torque of one of the conveyor screws internal to the reactor increases by more than 15% compared to the torque observed at the start of production. It can also be triggered after a given period, which can range from 2 hours to 4 months of production.

[0105] There figure 3 describes a method of operation of the process according to sequence T1, from the pretreatment reactor to ethanolic fermentation: after separation by cyclone 8 (or any other liquid / gas separation device), the acid marc obtained MA is conducted to enzymatic hydrolysis, with adjustment of the pH by adding base B directly into the hydrolysis reactor, so as to obtain after fermentation a fermentation wine VF.

[0106] There figure 4 is a variant of the process of the figure 3 : the difference is that here the pH of the acid marc MA is adjusted before introduction into the hydrolysis reactor, in particular by passing it through a neutralization zone / tank with base addition, or by introducing base addition into the transfer line from the cyclone to the hydrolysis reactor.

[0107] There Figure 5 describes a method of operation of the process according to sequence T2, from the pretreatment reactor to ethanolic fermentation: after separation by cyclone 8 (or any other liquid / gas separation device), the obtained acid marc MB is added to temporarily stored acid marc MA to make a mixture MA + MB which is carried out enzymatic hydrolysis, with pH adjustment by adding base B directly into the hydrolysis reactor, so as to obtain after fermentation a fermentation wine VF. Alternatively, as shown in figure 6 , the base addition can be done upstream of the hydrolysis reactor. In both cases, the base addition will be less than the base addition required during sequence T1, since the mixture of MA + MB marc is generally less acidic than the acid MA marc, depending on the proportion of basic marc in the mixture.

[0108] Different variations can be made to the example cleaning method / sequence T2 described above, while remaining within the scope of the invention, some of which are detailed below (at least some of these variations can be alternative or cumulative): A-During cleaning, the acid concentration A in the impregnation liquor preparation tank 31 can be reduced to a zero concentration, which ultimately means that the impregnation is carried out only with water. B- The wash water E from the screw 2b bringing the impregnated biomass into the reactor 4 can be recycled into the basic solution EB preparation tank 51 during cleaning, thereby reducing the additional water consumption due to cleaning. C- The biomass can be impregnated with a basic liquor during the cleaning sequence, either with the same basic liquor EB as that prepared in the tank 6, or with a different basic liquor, particularly in terms of base concentration B. This variant makes it possible to reduce the quantity of pure basic solution to be introduced into the pretreatment reactor 4, since there will be no more, or less, acid to neutralize to reach the targeted basic pH.However, a certain amount of basic liquor will be eliminated in the press (which corresponds to the water extracted from screw 2').

[0109] Thus, it may still be necessary to top up basic liquor EB directly in reactor 4 (via tank 51): the basic liquor EB preparation tank 51 still has two inlets, one for concentrated base B (concentrated KOH), the other for water, but here it also has two outlets: one outlet to the pretreatment reactor as before and one outlet to the impregnation reactor 3. With this configuration, the impregnation reactor 3 can be fed either with the acid solution EA from tank 31 during sequence T1, or with the basic solution EB from tank 6 during sequence T2. Tank 6 can thus feed both reactors 3 and 4 simultaneously, or at least during a common period during the cleaning of reactor 4.It is also possible to anticipate and start feeding basic EB solution to one of the reactors before the other, in particular impregnation reactor 3 before the start of cleaning with EB solution of pretreatment reactor 4.

[0110] D- It is also possible to combine the two previous variants, with, at the same time, the recycling of the pressate at the outlet of the screw 2b in the tank 61 for preparing basic liquor EB, and the feeding by this same tank 51 of the two reactors 3 and 4 during at least part of the sequence T2.

[0111] E- Two impregnation reactors 3, 3' can also be used, operating alternately. As in variant C, the biomass is impregnated not with an acid liquor EA but with a basic liquor EB during at least part of the cleaning / sequence T2 of the reactor, or even a little before, as follows: in production mode, the biomass is brought into the pretreatment reactor 3 supplied with acid liquor by tank 2, and in production + cleaning mode (during all or part of the cleaning), the biomass is re-routed to the impregnator 3', which is supplied with basic liquor EB from tank 51. A second impregnation reactor 3' is therefore used dedicated to cleaning. This embodiment has the advantage, compared to variant C, of reducing the transition times between acid impregnations and basic impregnations.

[0112] F- We can combine variants E and B, that is to say use the two impregnation reactors 3;3' and recycle the water extracted from the screw 2' in the tank 6 for preparing basic liquor EB.

[0113] G- The must (also called marc) can be recycled, particularly in the context of variant E with two impregnation reactors: the basic pretreated biomass M1 which leaves the separation device 8 during the cleaning of the pretreatment reactor 4. Indeed, during this period, it is basic. This must MB can then be washed at the outlet of the separation device 8 with water, it becomes a washed basic must MB', and a basic aqueous phase E1 extracted from it which is recycled into the tank 51 for preparing the basic liquor.

[0114] H- Another variant consists of using two 5.5' separation devices (cyclone) operating alternately: a cyclone is added which is dedicated to the treatment of basic marc MB. In production mode / sequence T1, the first cyclone is operational, it treats acid marc MA, in production + cleaning mode / sequence T2, the output of reactor 4 is switched to the second cyclone' which will therefore only separate basic marc MB. The advantage of this variant is to reduce the transition time between the two modes. This variant can also be combined with variant G: the basic marc MB is also washed once separated in one of the cyclones to recycle the basic wash water E1 to the basic liquor preparation tank 51.

[0115] J- This variant is derived from the previous variant E with two 3.3' impregnation reactors, with the following difference: In production mode, the conventional impregnation reactor 3 is used, supplied with acid solution EA by tank 1. In production + cleaning mode, the switch is made to the second 3' impregnation reactor, which is only supplied with water: during cleaning / sequence T2, the biomass is therefore only impregnated with an aqueous solution at neutral pH (and not a basic solution EB).

[0116] K- The invention also applies to biomass pretreatment processes without prior pre-impregnation with a liquor (this is called auto-hydrolysis): in this case, the biomass P, after possibly having undergone mechanical (crushing, etc.), thermal (drying), or humidification treatment, is directly introduced into the pretreatment reactor 4.

[0117] L- This variant combines the recycling of the press E1 from variant E with that of the washing water from the screw 2b of variant B to the tank 6 for preparing the basic liquor EB. This significantly reduces both the consumption of water and base required for cleaning according to the invention.

[0118] M- This variant recommends thermal integration of the process, by condensation of the steam V at the outlet of the cyclone 8. This steam V is used to heat the basic liquor EB circulating in pipes between the tank 51 and the pretreatment reactor 4 via a heat exchanger (not shown). It is also used to reduce the quantity of water used in the tank 6 by recovering the condensate resulting from the cooling of the steam leaving the cyclone, via a condenser (not shown).

[0119] N- According to another variant, it is possible to choose to inject biomass impregnated with acid liquor EA into the pretreatment reactor 4 from the impregnation reactor 3 in production mode, and to inject the non-impregnated biomass P directly into the pretreatment reactor 4 in sequence T2 (production mode + cleaning), then stopping the supply of biomass impregnated with acid liquor.

[0120] O- According to yet another variant, which can be combined with all the others, one can choose to inject into the pretreatment reactor a given impregnated biomass in production mode (sequence T1), and to inject another biomass, impregnated or not with a liquor, in production + cleaning mode (sequence T2). For example, in production, one chooses a straw-type biomass, and in production + cleaning mode, one chooses a more abrasive biomass, based on poplar: one thus temporarily increases, during the cleaning time, the abrasive nature of the biomass, to help to more easily detach the solid coke residues from the walls. Examples Example 1 not compliant with the invention: use of basic MB marc alone in SSCF

[0121] ("Simultaneous saccharification and co-fermentation" in English, i.e. concomitant enzymatic hydrolysis and alcoholic fermentation)

[0122] A batch of wheat straw is pretreated by steam explosion under acidic conditions. To do this, the straw is crushed to 50 mm and then introduced into a first impregnation reactor 3. The characteristics and composition of the wheat straw are as follows: Dry matter : 91,07 % Biomass flow rate : 65 kg MS / h

[0123] The straw is introduced into a first impregnator reactor 3 in order to be contacted with an acid liquor before being sent to a pretreatment reactor 4 by steam explosion. The operating conditions during production (sequence T1) are as follows: Impregnation: Concentrated acid solution flow rate: 1.29 kg / h, i.e. a pH of approximately 1 Acidity of the acid liquor: 1.1 g H 2 SO 4 / 100g Impregnation time: 1 min Steam explosion (cooking reactor 4): Residence time: 5 min Production time: 20 hours

[0124] After a period of 20 hours of operation under these conditions, a T2 sequence for cleaning the pretreatment reactor 5 by steam explosion is initiated: Impregnation: Concentrated acid solution flow rate: 1.29 kg / h, i.e. a pH of approximately 1 Acidity of the acid liquor: 1.1 g H 2 SO 4 / 100g Impregnation time: 1 min Steam explosion Sequence T2 / Cleaning: Residence time: 10 min

[0125] Basic liquor flow rate: sufficient to reduce the MS to the biomass saturation value Pressate recycling (mixture of washing water from the cooking reactor feed medium 5 (“plug screw” 2b) and spent acid liquor): 100% Duration of cleaning / T2 sequence: 2 h KOH concentration in the basic liquor: sufficient to change the biomass from a pH of 3 to a pH of 13

[0126] After the T2 cleaning sequence, a 20-hour cycle of T1 production and 2 hours of T2 cleaning was carried out. The total number of cycles carried out was 3 production / cleaning cycles (T1 sequence / T2 sequence).

[0127] In total, 54 kgMS / h (running time = 66 h; m (straw) = 3540 kg) of wheat straw were consumed to produce: 50 kgMS / h of substrate pretreated under acidic conditions (operating time = 60 h, m(acid substrate) = 3029 kg) 78 kgMS / h of substrate pretreated under alkaline conditions (operating time = 4.5 h, m(basic substrate) = 353 kg) 70 kgMS / h of “transition” grounds treated under variable pH conditions during cooking (operating time = 1.5 h; m(transition substrate) = 106 kg)

[0128] The marcs treated under acidic conditions MA and alkaline conditions MB are sampled. SSCF tests are conducted in the laboratory with: An SSCF test fed only with MA marc produced under acidic conditions, with a final DM (dry matter) of 24% marc. An SSCF test fed only with MB marc produced under alkaline conditions, final DM 19% marc.

[0129] The SSCF conditions are conventional, and will not be detailed further, they include neutralization to reach the desired pH to maximize the activity of the enzymes. The test is carried out in fed batch, a first part of the marc is put in contact with the biocatalysts, then the rest of the marc is added step by step over a period of 6 hours in order to control the viscosity of the medium in the first hours

[0130] There figure 7represents a graph, with, on the abscissa, the duration of the SSCF stage in hours, and, on the ordinate, the quantity of ethanol produced in g / kg. The production of ethanol from the acid marc MA corresponds to the curve whose points are diamonds, the production of ethanol from the alkaline marc MB corresponds to the curve whose points are squares: Expressing these results in ethanol concentration, we obtain: - final titer of the acid marc MA: 56 g / kg of ethanol, - final titer of the alkaline marc MB: 6 g / kg of ethanol.

[0131] Expressing these results in conversion efficiency, we obtain: on acid marc, MA, we have a yield of 30.4% weight of ethanol / sugars present at the input on alkaline marc MB, this yield is 7.5%.

[0132] It is clear from reading this graph and this data that the alkaline marc used alone MB does not allow satisfactory ethanol production to be obtained. Example 2: in accordance with the invention

[0133] The acidic marc MA and alkaline marc MB produced in Example 1 are used as a mixture in the SSCF test according to the same protocol as for Example 1. The test is fed with an MA + MB mixture of acidic and alkaline marc made in a mass proportion of 80% acidic marc MA and 20% alkaline marc MB (gross weight). This mixture is made before the introduction into the SSCF reactor 16 / 18. The final DM introduced is 24% DM from the marc mixture. The marc(s) are fed partly in an initial batch phase, and partly in fed-batch during the first 6 hours of reaction.

[0134] The kinetics of ethanol production is represented in the graph of the figure 8 , which represents the same data on the abscissa and ordinate as in the graph of the figure 7 , the curve this time corresponding to the production of ethanol from the mixture of marcs MA + MB.

[0135] We obtain: a final titer of 55.3 g / kg of ethanol, which is similar to the results obtained with the MA acid marc alone, a difference of less than 1 g / kg of ethanol is considered non-significant because in the precision of the test). a yield of 32.7% by weight of ethanol / sugars present at the input

[0136] Note that it was necessary to readjust the pH of this mixture with sulfuric acid during the initial batch phase and the fed-batch phase.

[0137] This example therefore demonstrates that with a significant proportion (20%) of alkaline marc in the marc mixture, it is possible to continue to obtain ethanol production that is substantially identical to that obtained with 100% acid marc: it is therefore possible to continuously clean the impregnation reactor without impacting the ethanol yield of the entire production of the installation, by using all the marc obtained after pretreatment, whether acid or alkaline, by means of a prior mixing of the two types of marc. Example 3 in accordance with the invention : use of acid marc MA, alkaline marc MB and washed marc M1 from a TCR (Fast Growth Coppice) poplar wood substrate

[0138] A batch of TCR poplar wood is pretreated by steam explosion under acidic conditions. To do this, the TCR poplar wood is ground to 50 mm and then introduced into a first impregnation reactor 3.

[0139] The characteristics and composition of the wood are as follows: Dry matter DM: 55.50% by weight Operating flow rate: 64 kg DM / h

[0140] The wood is introduced into a first impregnator reactor 3 in order to be contacted with an acid liquor before being sent to a steam explosion pretreatment reactor 5. The operating conditions during production are as follows: Impregnation for production and cleaning (sequences T1 and T2): Concentrated acid solution flow rate: 2.6 kg / h Acid liquor conductivity at 80°C: 103 mS / cm Impregnation time: 1 min Steam explosion (sequence T1 / Production): Residence time: 7.5 min Steam feed: 100% at the top Pressate recycling: 100% Production time: 58.5 hours

[0141] After a period of 60 hours of operation under these conditions, a cleaning sequence / T2 sequence of the steam explosion reactor 5 is initiated: Impregnation for production and cleaning / sequence T2: Concentrated acid solution flow rate: 2.6 kg / h Acid liquor conductivity at 80°C: 103 mS / cm Steam explosion Cleaning / sequence T2: Residence time: 10 min Basic liquor flow rate: sufficient to lower the MS to the biomass saturation value Pressate recycling: 100% Cleaning time: 1.5 h KOH concentration in the liquor: sufficient to change the biomass from pH 3 to pH 13 Number of cycles: 3 production and cleaning cycles (3 x sequence T1 + sequence T2)

[0142] In total, 116 kg / h (running time = 60 h; m(straw) = 6960 kg) of TCR poplar were consumed to produce: 119 kg / h of substrate pretreated in acidic conditions (operating time = 58.5 h, m(acid substrate) = 6962 kg) 361 kg / h of substrate pretreated in alkaline conditions (operating time = 1 h, m(basic substrate) = 361 kg) 178 kg / h of transition grounds treated in variable pH conditions during cooking (operating time = 30 min; m(transition substrate) = 89 kg)

[0143] Part of the marc treated in acidic conditions is filtered on a belt filter, by countercurrent washing, to separate a sweet juice (used for the propagation of yeasts), from a partially washed marc called M1 which will be reintroduced in liquefaction.

[0144] SSCF tests were conducted on marcs pretreated under acidic conditions, under alkaline conditions, and on partially washed marcs (transition marcs were not differentiated here): An SSCF test using MA marc produced under acidic conditions, marc produced under alkaline conditions MB, partially washed pretreated M1 marc, 20 mg of enzymes / g DM, for a final DM of 22.2% by weight. This test required 23.7 kg of neutralization solution (at 2.5% by weight in NH 3 ).

[0145] The SSCF protocol begins with a so-called liquefaction step carried out in fed-batch

[0146] The initial reaction mixture is composed of water, basic marc, partially washed marc and part of the marc produced under acidic conditions (up to 12.5% DM at the bottom of the tank) and supplemented with nutrients for the yeasts. The pH is adjusted to 5.3 with an alkaline solution (containing 23.5% by weight of NH3). When the pH is at 5.3, the enzyme and yeast biocatalysts are added. This addition corresponds to the start of the enzymatic hydrolysis reaction, and the concomitant fermentation reaction. After a short time, the fed-batch addition of the rest of the marc produced under acidic conditions is carried out over a period of 2 hours.

[0147] When the rheology of the mixture allows it, the mixture is transferred to a SSCF tank where the hydrolysis and fermentation reactions continue. The total duration of the SSCF is 144 h (total in both reactors)

[0148] The graph of the figure 9, with the same conventions of the graphs in the previous figures, corresponds to the production of ethanol produced from this marc. This implementation allows: For the SSCF, a final titer of 59.2 g / kg of ethanol For the SSCF, a yield of 41.3% by weight of ethanol / sugars present at the input Example 4 in accordance with the invention : acid marc MA and alkaline marc MB from a straw substrate.

[0149] A batch of wheat straw is pretreated by steam explosion under acidic conditions. To do this, the straw is crushed to 50 mm, dusted, then introduced into a first impregnation reactor.

[0150] The characteristics and composition of wheat straw are as follows: Dry matter: 88.30% by weight Operating flow rate: 65 kg DM / h

[0151] The straw is introduced into a first impregnator reactor 3 in order to be contacted with an acid liquor before being sent to a pretreatment reactor 5 by steam explosion. The operating conditions during production are as follows: Impregnation for production and cleaning (sequences T1 and T2): Concentrated acid solution flow rate: 2.5 kg / h Acid liquor conductivity at 80°C: 103 mS / cm Impregnation time: 1 min Steam Explosion Production (sequence T1). Residence time: 5 min Steam feed: 100% at the top Pressate recycling: 100% Production time: 78 hours

[0152] After a period of 80 hours of operation under these conditions, a cleaning sequence / T2 of the steam explosion reactor 5 is initiated: Impregnation for production and cleaning (sequence T2): Acid solution flow rate: 2.5 kg / h Acid liquor conductivity at 80°C: 103 mS / cm Steam explosion Cleaning / sequence T2: Residence time: 10 min Basic liquor flow rate: sufficient to lower the MS to the biomass saturation value Pressate recycling: 100% Cleaning duration: 2 h KOH concentration in the liquor: sufficient to change the biomass from pH 3 to pH 13 Number of cycles: 4 production and cleaning cycles: 4 cycles T1 + T2

[0153] In total, during the 4 production / cleaning cycles, 73 kg / h (operating time = 320 h; m(straw) = 23360 kg) of wheat straw were consumed to produce: 138 kg / h of substrate pretreated in acidic conditions (operating time = 312 h, m(acidic substrate) = 43056 kg) 342 kg / h of substrate pretreated in alkaline conditions (operating time = 8 h, m(basic substrate) = 2732 kg)

[0154] SSCF tests are conducted on MA marcs pretreated under acidic conditions and MB alkaline conditions, without differentiating between transition marcs: An SSCF test was carried out with MA marc produced under acidic conditions and MB marc produced under alkaline conditions, for a final MS of 22.5% by weight. This test required 42.7 kg of neutralization solution (at 23.5% by weight in NH3).

[0155] The SSCF protocol begins with a so-called liquefaction step to arrive at a mixture of 92% by weight of pomace produced under acidic conditions / 8% by weight of pomace produced under basic conditions. The liquefaction is carried out in fed-batch. The initial reaction mixture is composed of water, basic pomace, and a portion of the pomace produced under acidic conditions (up to 12.5% DM at the starter) and supplemented with nutrients for the yeasts. The pH is adjusted to 5.3 with an alkaline solution (containing 23.5% by weight of NH 3 ). When the pH is at 5.3, the biocatalysts, enzymes and yeasts are added. This addition corresponds to the start of the enzymatic hydrolysis reaction, and the concomitant fermentation reaction. After a short time, the addition in fed-batch of the remainder of the pomace produced under acidic conditions is carried out over a period of 6 hours.

[0156] When the rheology of the mixture allows it, the mixture is transferred to a SSCF tank where the hydrolysis and fermentation reactions continue. The total duration of the SSCF is 144 h (total in both reactors).

[0157] The kinetics of ethanol production is described in the graph of the figure 10 , with the same conventions as for the previous graphs.

[0158] This implementation in accordance with the invention makes it possible to obtain: A final titer of 54.8 g / kg of ethanol A yield of 36.2% by weight of ethanol / sugars present at the input

[0159] With an addition of 8% gross weight of MB marc in the MA acid marc, the double SSCF reaction therefore takes place satisfactorily. Example 5 in accordance with the invention : acid marc MA, alkaline marc MB and washed marc M1, from a straw substrate (pretreatment and washing conditions different from those of example 4, with a drop in the reactor temperature)

[0160] A batch of wheat straw is pretreated by steam explosion under acidic conditions. To do this, the straw is crushed to 50 mm, dusted, then introduced into a first impregnation reactor 3.

[0161] The characteristics and composition of wheat straw are as follows: Dry matter: 88.30% by weight Operating flow rate: 50 kg DM / h

[0162] The straw is introduced into a first impregnation reactor 3 in order to be contacted with an acid liquor before being sent to a pretreatment reactor 5 by steam explosion. The operating conditions during production are as follows: Impregnation for production and cleaning (sequence T1): Concentrated acid solution flow rate: 2.5 kg / h Acid liquor conductivity at 80°C: 103 mS / cm Impregnation time: 1 min Steam explosion in Production / sequence T1: Residence time: 5 min Steam feed: 100% at the top Pressate recycling: 100% Production time: 78 hours

[0163] After a period of 80 hours of operation under these conditions, a T2 cleaning sequence of the steam explosion reactor 5 is initiated: Impregnation for production and cleaning / sequence T2: Acid solution flow rate: 2.5 kg / h Acid liquor conductivity at 80°C: 103 mS / cm Steam explosion Cleaning / sequence T2: Residence time: 10 min Basic liquor flow rate: sufficient to lower the MS to the biomass saturation value Pressate recycling: 100% Cleaning duration: 2 h KOH concentration in the liquor: sufficient to change the biomass from pH 3 to pH 13 Number of cycles: 1 production and cleaning cycle (T1 + T2)

[0164] In total, during this production / cleaning cycle, 58 kg / h (operating time = 80 h; m(straw) = 4640 kg) of wheat straw were consumed to produce: 109 kg / h of pretreated substrate under acidic conditions (operating time = 78 h, m(acidic substrate) = 8502 kg) 372 kg / h of pretreated substrate under alkaline conditions (operating time = 2 h, m(basic substrate) = 744 kg)

[0165] A SSCF test was conducted at the pilot site on the marcs pretreated under acidic conditions MA and alkaline conditions MB, for a final MS of 22.5% by weight. This test required 33.8 kg of neutralization solution (at 23.5% by weight in NH 3 ).

[0166] The SSCF protocol begins with a so-called liquefaction step to arrive at a mixture of 90% by weight of marc produced under acidic conditions MA / 10% by weight of marc produced under basic conditions MB.

[0167] Liquefaction is carried out in fed-batch. The initial reaction mixture is composed of water, basic marc, and a portion of the marc produced in acidic conditions (up to 12.5% DM at the bottom of the tank) and supplemented with nutrients for the yeasts. The pH is adjusted to 5.3 with an alkaline solution (containing 23.5% by weight of NH 3 ). When the pH is at 5.3, the biocatalysts enzymes and yeasts are added. This addition corresponds to the start of the enzymatic hydrolysis reaction, and the concomitant fermentation reaction. After a short time, the addition in fed-batch of the remainder of the marc produced in acidic conditions is carried out over a period of 6 hours.

[0168] When the rheology of the mixture allows it, the mixture is transferred to a SSCF tank where the hydrolysis and fermentation reactions continue. The total duration of the SSCF is 118h (total in both reactors)

[0169] The kinetics of ethanol production is described in the graph of the figure 11 , which uses the same conventions as the previous graphs.

[0170] This implementation in accordance with the invention makes it possible, at 118 hours, to obtain: A final titer of 50.0 g / kg of ethanol A yield of 32.2% by weight of ethanol / sugars present at the input

[0171] Ethanol production remains, here again, at a satisfactory level even with the addition of basic marc in significant quantity (10%) to conventional MA acid marc.

Claims

1. Process for treating lignocellulosic biomass, successively comprising b) a step of pretreatment by cooking, with or without steam explosion, of the biomass placed beforehand under acidic or neutral pH conditions in a pretreatment reactor (3), to produce an acidic or neutral pretreated marc (AM), alternating with b') a step of pretreatment by cooking, with or without steam explosion, of the biomass placed beforehand under acidic, neutral or basic conditions, with sufficient introduction into the pretreatment reactor (3) of a basic aqueous solution (EB), at least for the biomass placed beforehand under acidic or neutral conditions, to produce a basic pretreated marc (BM), and then c) a step of enzymatic hydrolysis in a hydrolysis reactor (16) of a mixture of the acidic or neutral pretreated marc (AM) obtained from step b) with the basic pretreated marc (BM) obtained from step b').

2. Process according to the preceding claim, characterized in that, during step c) of enzymatic hydrolysis of the mixture of acidic or neutral pretreated marc (AM) with the basic pretreated marc (BM), said mixture is replaced with only acidic or neutral pretreated marc (AM) for a portion only of the duration of said step c).

3. Process according to either of the preceding claims, characterized in that the mixing of the acidic or neutral pretreated marc (AM) obtained from step b) with the basic pretreated marc (BM) obtained from step b') in step c) is performed upstream of the hydrolysis reactor (16), or directly in the hydrolysis reactor (16).

4. Process according to one of the preceding claims, characterized in that the mixing, in step c), of the acidic or neutral pretreated marc (AM) obtained from step b) with the basic pretreated marc (BM) obtained from step b') is performed by withdrawals from a zone for temporary storage (13) of the basic pretreated marc (BM) at the outlet of the pretreatment reactor (5).

5. Process according to the preceding claim, characterized in that step b') producing a basic pretreated marc (BM) is a step of cleaning the pretreatment reactor (5).

6. Process according to one of the preceding claims, characterized in that a step of adjusting the pH of the pretreated marc (AM, BM) or of the mixture of pretreated marcs before or during the enzymatic hydrolysis step c), notably an adjustment of the pH to between 4 and 6, is envisaged.

7. Process according to one of the preceding claims, characterized in that, over a given production time, the sum of the durations of the steps b) of pretreatment of the biomass placed beforehand under acidic or neutral pH conditions in a pretreatment reactor, to produce an acidic or neutral pretreated marc (AM), is greater, notably at least 2 to 5 times greater, than the sum of the durations of the steps b') of pretreatment of the biomass placed beforehand under acidic, neutral or basic conditions, with optional sufficient introduction into the pretreatment reactor of a basic aqueous solution (EB), to produce a basic pretreated marc (BM).

8. Process according to one of the preceding claims, characterized in that a separation is performed between pretreated marc (AM, BM) and aqueous phase in the liquid or vapour form at the outlet of the pretreatment reactor (5), by a separation device (8) or several separation devices in parallel, notably two separation devices, operating alternately.

9. Process according to one of the preceding claims, characterized in that, during the enzymatic hydrolysis step c) in the hydrolysis reactor (16), the mixing of the acidic or neutral pretreated marc (AM) obtained from step b) with the basic pretreated marc (BM) obtained from step b') is performed in an AM / BM weight ratio of at least 80 / 20.

10. Process according to one of the preceding claims, characterized in that the pretreatment step b) is preceded by a step a) of impregnating the biomass with an acidic or neutral aqueous solution, in an impregnation reactor (3).

11. Facility for treating lignocellulosic biomass, comprising, from upstream to downstream, a biomass impregnation reactor (3) in fluid connection with a vessel (31) for preparation of acidic aqueous solution, a reactor for pretreatment (5) of the impregnated biomass, in fluid connection with a vessel (51) for preparation of a basic aqueous solution, a pretreated marc separation device (8) downstream of the pretreatment reactor (5) and which is optionally combined with means for rinsing with an aqueous solution (E), and which is in fluid connection with a zone for intermediate storage (13) of basic marc (BM), and optionally a zone for intermediate storage (11) of acidic marc (AM), and an enzymatic hydrolysis reactor (16) fed with marcs from said / at least one of said storage zones (11, 13).

12. Facility according to the preceding claim, characterized in that it comprises a zone (14) for adjusting the pH of the pretreated marcs between the / at least one of the storage zones (11, 13) and the enzymatic hydrolysis reactor (16), notably a pH adjustment zone that is common for said marcs.

13. Facility according to the preceding claim, characterized in that the adjustment zone is a vessel or a hopper which ensures the mixing of the marcs obtained from at least the or one of the storage zones (11, 13).

14. Facility according to one of Claims 11 to 13, characterized in that it comprises two impregnation reactors (3) and / or two separation devices (8) and / or two pretreatment reactors (5) operating alternately depending on whether the pretreatment is performed on biomass placed beforehand under acidic or neutral pH conditions to produce an acidic or neutral pretreated marc (AM), according to step b), or on biomass placed beforehand under acidic, neutral or basic conditions, with sufficient introduction into the pretreatment reactor of a basic aqueous solution (EB) to produce a basic pretreated marc (BM) according to step b').

15. The use of the process or of the facility according to the preceding claims, for the treatment of biomasses such as wood, straw, agricultural residues, and all dedicated energy crops, notably annual or perennial plants such as miscanthus, for the purpose of producing sugars, biofuels or biobased molecules.