WO2022263630A1

WO2022263630A1 - Enzymatic treatment method and system for fibrous cellulosic material and rigid cellulosic product

Info

Publication number: WO2022263630A1
Application number: PCT/EP2022/066561
Authority: WO
Inventors: Sebel LEE YUN
Original assignee: Honext Material, Sl
Priority date: 2021-06-18
Filing date: 2022-06-17
Publication date: 2022-12-22
Also published as: CN117795156A; EP4355946A1

Abstract

Enzymatic treatment method and system for fibrous cellulosic material and rigid cellulosic product, wherein the method comprises introduction of raw fibrous cellulosic material (1) in a stirrer (20); enzymatic treatment of the raw fibrous cellulosic material (1) for a specific period of time to obtain a treated cellulosic material, said enzymatic treatment including the addition of enzymes (11, 12, 13, 14) to the raw fibrous cellulosic material and the uniform distribution of said enzymes in the raw fibrous cellulosic material by stirring; drying the treated cellulosic material; wherein at least a proportion of the raw fibrous cellulosic material is derived from industrial waste.

Description

DESCRIPTION

ENZYMATIC TREATMENT METHOD AND SYSTEM FOR FIBROUS CELLULOSIC

MATERIALAND RIGID CELLULOSIC PRODUCT

Technical field

The present invention is directed to an enzymatic treatment method for fibrous cellulosic material, to a rigid cellulosic product and also to a method of forming a rigid cellulosic product. Specifically, the proposed method allows the performance of an enzymatic treatment on raw fibrous cellulosic material, at least a proportion of which is derived from industrial waste, without requiring the addition of significant quantities of water, with the economic and environment benefit of reducing overall water consumption and therefore the amount of sewage water produced.

In addition, the present invention enables the production of rigid cellulosic products comprising at least a proportion of raw fibrous cellulosic material derived from industrial waste. Industrial waste is typically defined as waste that is non-reusable and cannot therefore be re-used or recycled, and which otherwise would be deposited in landfill sites with the associated negative environmental impact.

The present invention is focused on upcycling the cellulosic fibres of the aforementioned industrial waste to obtain rigid cellulosic products with suitable mechanical properties. Cellulosic fibres are considered non-reusable when at least one of the following applies: the fibres have an average length of less than 5mm, the fibres have an average thickness below 0.1 mm, the percentage of fines inside the cellulosic waste is above 10% in mass, where fines are defined as the smallest components in cellulosic fibres fraction that can pass through holes of 76 micrometres of diameter [SCAN. Mechanical and chemical pulps - Fines content. Standard CM 66:052005], or the cellulosic fibres are mixed with other compounds provoking complexity in recycling. These other compounds include inorganic charges, synthehic compounds, material impurities, etc.

State of the Art

Waste paper and waste cardboard can be effectively recycled when it contains low levels of glues, inks, water resistant resins and other additives. Examples of these water resistant resins and additives are alkyl keten dimers, alkenyl succinic anhydrides, epichlorhydrin, melamine, urea-formaldehyde, polymines, styrienes, dextrin or other polymers that enhance specific material properties (i.e. polyurethane, vinyls, acrylic adhesives improve mechanical properties). However, the recycling cost and the quality of the cellulosic products obtained can be significantly affected if the waste paper and cardboard contained large amounts of those additives, requiring additional treatment steps and/or increasing the consumption of additives or energy during the treatment of said cellulosic material.

Furthermore, the commonly used recycling methods for wastepaper and waste cardboard require the use of large amounts of water which is later discarded, producing sewage water which has to be treated, so reducing the environmental benefits of recycling.

The paper and cellulose manufacturing industry also generates significant quantities of industrialwaste, including a liquid or primary sludge which contains cellulosic material considered non-reusable as defined by the above mentioned characteristics. This is considered to be an effluent with serious environmental liability for the manufacturer, but which can be mitigated by a proper enzymatic treatment to produce a raw fibrous cellulosic material.

Another source of industrial waste is the cellulosic fibre residue streams from the textile industry where, for example, the presence of different types of cellulose fibres and plastic mixtures provokes difficulty in re-using or recycling these residues.

A further source of industrial waste is construction waste cellulose fibre, for example, the cardboard recovered when recycling gypsum boards. The gypsum-based recovery process, through a mechanical crushing action and a subsequent dry double compression, is able to separate the gypsum from the paper, obtaining a finished product with the same characteristics as natural gypsum. The recovered gypsum powder is 97.6% pure and practically free from paper. While the gypsum by-product is reusable, the cellulosic fibres are typically combusted without being used to form a useful product. Typically the cellulosic fibres have a length in the order of 1mm.

The Applicant has discovered that with suitable processing, including enzymatic treatment, the previously non-reusable cellulosic fibres derived from industrial waste can ultimately be used to produce useful cellulosic products, not only with the environmental benefits associated with re-using material that would otherwise end up in landfill, in conjunction with the reduced water consumption and consequential reduced wastage, but importantly, offering cellulosic products which can perform at least as well as products derived from other cellulosic fibres and using alternative processes, which have a greater negative environmental impact. Document EP2569480B1 describes an enzymatic treatment method for cellulosic material, mainly waste paper and waste cardboard, such waste paper and cardboard not considered to be industrial waste, in which said cellulosic material is diluted in water in a pulper, obtaining a liquid mixture with of between 5% and 10% pulp, and therefore containing 90% or 95% of water. Later, enzymes are added to the liquid mixture to perform the enzymatic treatment on the cellulosic material, obtaining a treated cellulosic material suitable for the production of new cellulosic products. The liquid mixture is introduced into a former where it is filtered, and the solid fraction obtained therefrom is compressed or molded and dried producing a rigid cellulosic material product.

The filtering and drying process is time and energy consuming and produces a large amount of sewage water, which contains enzymes and other valuable components, and which requires expensive treatments to reduce its environmental impact and to permit its reuse in the process.

The rigid cellulosic product obtained from said process can be used for construction and packaging or as a decorative material.

The method described in EP2569480B1 presents several problems of which the most prominent are described below:

One problem is that the cellulosic material contained in the liquid mixture is composed of different elements with different densities, producing a greater accumulation of the higher density elements where the liquid mixture is introduced into the former, producing an uncontrolled non-homogeneous rigid cellulosic product, directly affecting other parameters such as: density, thickness, and mechanical resistance.

A second problem is that the process is limited to the production of a single layered rigid cellulosic product made entirely of the cellulosic material filtered from one single liquid mixture because the formation of the rigid cellulosic product and the filtering of the liquid mixture is produced simultaneously. A liquid mixture containing only between 5% and 10% of cellulosic material will get mixed with any other different liquid mixture supplied simultaneously on the same former before having time to be filtered and settled to produce an initial layer of a laminated product, and if the second liquid mixture is supplied once the first liquid mixture has been already filtered, then the 95% of water contained on the second liquid mixture will dissolve said initial layer preventing the formation of a laminated product.

Because this process only permits the obtention of single layered rigid cellulosic products, the properties of the surface layer cannot be differentiated from the rest of the product, preventing for example the creation of a superficial layer with a reduced porosity to reduce paint or sealant absorption.

A third problem is that, according to this method, any additive included shall be soluble in water to obtain an even distribution, but most of said additives will be wasted with the sewage water, producing contamination and financial wastage.

A fourth problem relates to the requirement to heat the liquid mixture to reduce its surface tension, improving the filtration wasting energy to heat the water that becomes sewage water once filtered.

A fifth problem is that, for the filtration process during formation, a vacuum system is required, which is very expensive in terms of energy and maintenance.

Finally, high energy is consumed during the drying process, and it gradually increases with the density and thickness of the rigid cellulosic product to be obtained.

WO 03/047826 A1 discloses a method of manufacturing a fiberboard or a similar wood-based product. The method comprises providing a lignocellulosic material, contacting the lignocellulosic material with an activating agent to produce a modified lignocellulosic material containing free radicals, forming the modified material into a layered structure, and pressing the layered structure into a compressed product.

WO 2008/026932 A1 discloses a method for thermal enzymatic hydrolysis of lignocellulose.

WO 2014/160262 A1 provides processes for converting cellulosic waste, such as municipal solid waste, to bioproducts such as monosaccharides and fermentation products.

US 2016/0060667 A1 provides a continuous process for enzymatic hydrolysis of pretreated biomass.

WO 2015/150620 A1 provides a method for producing fibrillated cellulose, the method comprising providing pulp, treating said pulp at a consistency of at least 10% with a cellulase, and fibrillating said pretreated pulp to obtain fibrillated cellulose.

The proposed method solves, or at least mitigates the problems associated with the prior art.

Brief description of the invention

According to a first aspect, the present invention is directed to an enzymatic treatment method for fibrous cellulosic material, that is to say a method for applying an enzymatic treatment to a fibrous cellulosic material. It will be understood that a fibrous cellulosic material is a material mainly composed from fibers of any length made of cellulose and other vegetal compounds able to generate bonds with other cellulose fibers.

The present method allows the use of a proportion of fibrous cellulosic material derived from industrial paper, cardboard, textile, construction waste, or some other waste source where the residue cellulosic material would otherwise be un-reusable as has been described above, typically low quality fibrous cellulosic material mainly comprising fibers shorter than 5mm and/or fragile fibers and/or recycled fibers which are typically partially bonded with impurities and therefore have a reduced bonding capacity with other cellulosic fibers. By recycled fibres, it is meant fibres which are not virgin fibres, coming from industrial process waste streams and/or having been part of a product used in the market for at least one lifecycle. The enzymatic process enables the industrial waste fibres to bond with other non-industrial fibres and/or each other providing the fibres are natural fibres and can generate hydrogen bonds.

The raw fibrous cellulosic material introduced in the stirrer can include some impurities, other than the cellulosic fibers with the ability to bond with other cellulosic fibers.

Preferably, the raw fibrous cellulosic material form industrial waste or another source will be free of large particles or clusters, bigger than 5mm, because such particles or clusters will have a reduced or no capacity to generate bonds with other cellulose fibers. A particle size reducer, such as a crusher, a shredder or a pulper, can be used prior to the stirrer to reduce the size or eliminate particles or clusters.

Alternatively, the raw fibrous cellulosic material can include large particles or clusters bigger than 5mm if such particles or clusters are soluble or breakable in small particles or clusters smaller than 5mm or fibers of any length by the stirrer. An example of large soluble or breakable particles or clusters can be for example cardboards, or sludge lumps.

The Applicant has discovered that the enzymatic treatment process can be used in a raw fibrous cellulosic material comprising at least a proportion of industrial waste with a low water content and a specific flowability.

Preferably, at least 20% of the raw fibrous cellulosic material in the formed product is industrial waste generated from the paper or cellulosic manufacturing industry, in particular from primary sludge from a physicochemical treatment plant.

In the present invention, the terms primary sludge and sewage sludge may be used indistinctly. In a preferred embodiment, at least 40% of the raw fibrous cellulosic material is primary sludge from paper manufacturing industry, more preferably, at least 50% of the raw fibrous cellulosic material is primary sludge from paper manufacturing industry, even more preferably at least 60% of the raw fibrous cellulosic material is primary sludge from paper manufacturing industry, and even more preferably, at least 70% of the raw fibrous cellulosic material is primary sludge from paper manufacturing industry.

Primary sludge is composed of ca. 40-90% by weight of cellulose fibers and ca. 10-60% by weight of inorganic fillers. These inorganic fillers are added during the paper manufacturing process to improve the properties of the paper. The raw cellulosic material derived from primary sludge described in this invention stands out for comprising a large amount of fines, more than 15% of cellulose fibers. Fines are small particles composed of cellulose, but which do not have the shape of a fiber due to their size. This particularity means that the raw cellulosic material used in the method of the present invention cannot be used for the manufacture of paper or other products that require good mechanical properties, as the ends do not confer mechanical bonds. The above-mentioned particularities of this raw cellulosic material make it very difficult to obtain products requiring processes of low humidity, pressure and temperature, and therefore it is very important to improve the properties of the raw cellulosic material to reduce the amount of adhesives used in the resulting product.. if not a high amount of adhesives is present. Note that the fact that it is considered a waste of the paper industry is due to the short overall length of the cellulose fibers that compose said material.

Moreover, the raw cellulosic material according to the present invention is preferably substantially lignin free, or the presence of lignin accounts to a trace amount.

To complement the amount of raw fibrous cellulosic material to 100%, other source of cellulose fibers are available not derived from industrial waste, such as waste paper originated from high quality printed paper, or any kind of cellulose fiber from vegetal origin, preferably from post consumer waste, that is material which has already been used.

The raw cellulosic material can be previously characterized by microscopy, Heizberg assessments, leakage tests, enzymatic reaction tests, or determination of inorganic content, without limiting to other complementary techniques. The characterization allows to determine the mixture of raw cellulosic material in order to obtain a product that meets the standard specifications of the product (reduction tolerance quality control parameters).

The standardization of the product by means of the modulation of the % w / w (dry) of the different types of raw cellulosic material that conform the material may preferably be automated by means of algorithms of calculation based in statistics arising from databases linking raw cellulosic material and results in quality control. Preferably, the water content of the raw fibrous cellulosic material is comprised of between 20% and 80%, preferably between 20% and 60%, more preferably between 20% and 50% and most preferably between 20% and 40%, and is adjusted to produce a raw fibrous cellulosic material with a specific flowability which is a fluent viscous sludge-like granulous texture and not a liquid-like flowability.

Said specific flowability is adjusted to be the minimal water content necessary to allow the uniform and efficient stirring of the raw fibrous cellulosic material to produce an even distribution of the enzymes and to allow the transference of the raw fibrous cellulosic material and of the treated cellulosic material through the production plant.

Said transference can be produced, for example, by conveyor belts, conveyor screws and other paste or granular material conveyors because specific flowability is usually too dense to allow an efficient use of liquid conveyors such as pumps, which could be possible but not the preferred method.

According to the proposed method, no filtering step is required for initial separation of the solid fraction and liquid fractions because the water content is sufficiently low that conventional filtering, without additional measures such as pressure, will not significantly reduce the water content.

The low water content of the present invention can be easily achieved using little energy, for example by heating, to obtain a dried treated cellulosic material. This method requires much less energy than prior art wet methods where, after the initial filtering, the water content is still elevated and much more drying energy is required than with the proposed method, saving energy, time and reducing its cost and environmental impact.

Preferably, once the enzymes have been added to the raw fibrous cellulosic material no further water or diluent is added, maintaining the water content unchanged during said enzymatic treatment.

It is also proposed that operational parameters of the stirrer could be configured to produce, on the raw fibrous cellulosic material with the specific flowability, dynamic currents affecting all the volume of raw fibrous cellulosic material contained in the stirrer to ensure an even distribution of the enzymes and a maximal contact of the enzymes with all the raw fibrous cellulosic material to be treated in the stirrer.

Said dynamic stirring can also, optionally, produce high turbulent currents on the raw fibrous cellulosic material during the enzymatic treatment. Because the mixture has a lower water content compared to a wet enzyme process, the even distribution of the enzymes affecting all the fibers of the raw fibrous cellulosic material is not easily achievable because, due to the viscosity of the proposed raw fibrous cellulosic material with low water content, the required stirring cannot be obtained by a mere agitation, as is the case with liquid textures, but requires a precise and dynamic stirring which is designed and provided to ensure that the enzymes affect all the raw fibrous cellulosic material to be treated contained in the stirrer.

For example, the operational parameters can include the temperature of the raw fibrous cellulosic material and/or a movement velocity of multiple active stirring elements which are contained in the stirrer for the stirring of the raw fibrous cellulosic material.

Increasing the temperature of the raw fibrous cellulosic material results in an increase in flowability requiring additional water and the associated higher additional energy consumption during heating ro remove the additional water.

The movement of each active stirring element produces a stirred volume of raw fibrous cellulosic material there around whose size depends on the movement velocity and on the specific flowability of the raw fibrous cellulosic material. The movement velocity of all the active stirring elements of the stirrer is configured to produce stirred volumes which sizes, aggregated, cover the entire volume of the raw fibrous cellulosic material contained in the stirrer. To obtain this effect it is also preferred to include said active stirring elements equi distant to each other within the stirrer.

For example, the stirrer can include multiple stirring elements such parallel blades with the same or different rotation velocity or direction and/or rotative and non-rotative blades to generate dynamic currents and also to increase the turbulences generated. The stirring elements can also include blades attached to the walls of the stirrer which can be static or rotative.

More in detail, the movement of each active stirring element produces, on the stirred material, a pushing force forwards and a suction force backwards the active stirring element, generating a bulk current loop on the surrounding stirred material affecting a certain stirred volume. Depending on the movement velocity of the active stirring element and on the flowability of the stirred material, the size of said bulk current loops will change, modifying the stirred volume. For example, an increase in the flowability of the raw fibrous cellulosic material due to an increase in the water content will produce an increase of stirred volume and besides, an increase in the movement velocity of the active stirring elements will also produce an increase in the stirred volume.

Preferably the movement velocity of the active stirring elements remains below a cavitation limit of the raw fibrous cellulosic material having certain flowability to prevent undesired effects and inefficiencies.

Preferably, the multiple active stirring elements are distributed inside the stirrer, preferably evenly distributed separated by a known distance from each other.

The flowability of the material to be stirred and the movement velocity of the active stirring elements can be configured to ensure that the aggregation of all the stirred volumes covers the entire volume of the material contained in the stirrer.

The treatment method can be adapted to treat batches of raw fibrous cellulosic material or can alternatively be adapted to treat continuous flow of raw fibrous cellulosic material, in which case the stirrer will be a stirrer tunnel or column with an inlet end and an outlet end opposite each other, producing a continuous flow of raw fibrous cellulosic material in between which takes a specific period of time from the inlet to the outlet.

The water content of the raw fibrous cellulosic material can be adjusted, within the range between 20% and 80%, to obtain the specific flowability which is predefined, for example within a range of acceptable fluidities in which the stirrer can operate properly to obtain said dynamic current affecting all the raw fibrous cellulosic material contained in the stirrer.

Said adjustment in the water content can be achieved by spraying additional water during the addition of the enzymes or by increasing or reducing the dilution of the enzymes previous to the addition thereof to the raw fibrous cellulosic material. The flowability of the raw fibrous cellulosic material can be measured based on viscosimetry tests to determine any additional adjustment in the water content or can be deduced from the water content measured on the raw fibrous cellulosic material. Said measurements can be obtained previous to the introduction of the material into the stirrer.

Alternatively, the flowability of the raw fibrous cellulosic material to be stirred can be deduced from the energy required to produce the required stirring. For example, the active stirring elements can be activated by an electric motor in which electric consumption will be indicative of the flowability of the raw fibrous cellulosic material. Depending on the results of those measurements additional water can be added to the stirred material to increase its flowability.

Alternatively, it is proposed that the flowability of the raw fibrous cellulosic material is measured, and then the operational parameters of the stirrer are adjusted in response to the measured specific flowability to obtain the dynamic current affecting all the raw fibrous cellulosic material contained in the stirrer.

In this case, depending on the measured flowability of the raw fibrous cellulosic material, the movement velocity of the active stirring elements can be increased or reduced to ensure that the stirring affect the entire volume of the raw fibrous cellulosic material, or the temperature thereof can also be adjusted to obtain the dynamic currents without requiring unnecessary energy consumption. The stirrer will include a heater for heating its content to an objective temperature considered optimal.

The temperature also affects the enzymatic treatment. The gas pressure and/or the gas composition into the stirrer can optionally also be adjustable to regulate the enzymatic treatment.

One of the main current issues in the enzymatic processing under high consistency conditions (i.e., wherein the water content of the raw cellulosic material has a water content of 40% or less) is the difficulty in which the enzymes fit with the substrate of the cellulose fibers. This is due to the poor dispersion of enzymes in a low humidity environment.

The presence of a dense gas improves the enzymes-substrate contact, increasing the yield of the enzymatic processing, enabling an efficient process with a low water content (or high consistency conditions) and greatly improving the processing yield with respect to turbulent agitation with countercurrent flow of gases. This is because, with countercurrent flow, the enzyme-substrate contact time is much lower than with dense gas turbulent agitation. Dense gases inside a hermetic reactor can improve the dynamics of the stirring process as they increase the relative pressure during enzymatic treatment.

A dense gas is herein defined as a gas having a density double that of air at normal atmospheric conditions (25°C, 1 atm). Air has a density of 1,2 kg/m³ at normal conditions.

Therefore, according to an additional embodiment, the enzymatic treatment of the raw fibrous cellulosic material is carried out in the presence of a dense gas. Such gases include preferably sulfur hexafluoride and/or sulfur dioxide. Said dense gases may be in a concentration equal to or lower than 5% by weight with respect to the total volume of the reactor in which the enzyme treatment is taking place. The density of sulfur hexafluoride is 6,2 kg/m³ at normal conditions, while the density of sulfur dioxide is 2,9 kg/m³ at normal conditions.

Preferably, the raw fibrous cellulosic material during the enzymatic treatment is maintained with a pH of between 5 and 9 and/or with a temperature of between 40°C and 70°C, to improve the enzymatic treatment. It is also proposed to produce the enzymatic treatment within the stirrer, preferably stirring the raw fibrous cellulosic material during the entire or almost the entire duration of the specific period of time; proposed to be between 15 to 60 minutes.

Once the enzymatic treatment is concluded, the treated cellulosic material is transferred from the stirrer to a dryer, optionally being stored in an intermediate container.

The enzymes are preferably liquid or dissolved in liquid and are added to the raw fibrous cellulosic material by spraying, this method assures the maximal distribution of the enzymes and requires minimal addition of water to the raw fibrous cellulosic material. Said spraying can be produced for example on the top surface of the raw fibrous cellulosic material contained in the stirrer while the stirrer is in operation, assuring the constant renewal of the material exposed on the top surface receiving the enzymes.

The concentration of the enzymes on the sprayed liquid is optimized to ensure that once all the required enzymes have been added to the raw fibrous cellulosic material, the water content of the final mixture remains within the stipulated parameters.

The added enzymes are preferably selected to smooth the fibers, remove radicals from the outside of the fibers and increase the specific surface area of the fibers. Those effects can be obtained for example by different combinations of the following enzymes: xylanase, laccase, cellulase and/or combinations thereof.

Depending on the specific composition of the raw cellulosic material and the properties of the cellulose fibers therein, variability in the added enzymes can be expected. Therefore, the composition of the enzymes is adapted.

The optimization of the enzymatic mixture (or cocktail) may be automated, for instance, by means of calculation algorithms based on statistics resulting from a database linking raw cellulosic material, enzymes used and quality control results obtained.

In the event that variations of the raw cellulosic material according to the present invention require different enzymatic cocktails, each of those types of raw cellulosic material may be treated specifically, i.e., adapting the best combination of enzymes to the specific raw cellulosic material to be treated by the method according to the present invention.

It is believed the cellulases defibrillate the cellulose fibres to increase the specific surface of the fibres, the hemicellulases attack various components of hemicellulose, cutting the cellulose fibre bundles loose and increasing the access of cellulases to the fibres, the surface of the fibres is cleaned from impurities with xylanase, degrading the xylan groups, and the lacasses bleach and soften the fibres. Whilst specific enzymes have been mentioned, a person skilled in the art will be able to identify other enzymes which perform the same function on the cellulosic fibres.

According to an additional embodiment, the composition of the raw fibrous cellulosic material introduced in the stirrer is analyzed, and the proportions of the different enzymes added are adjusted in response to the result of said analysis. The raw fibrous cellulosic material, depending on its origin, will have a different composition and will require different amount of the different enzymes to obtain the desired result.

Preferably, after the drying process, the dried treated cellulosic material will have a water content below 20%. This low content of water allows the storage of the dried treated cellulosic material without requiring any special measures beyond keeping it clean and dry, until its use is required.

The treated cellulosic material can be screened and separated into different fractions by fiber sizes. This step can be performed during the drying step, which can be performed in a trommel screen, or after the drying step, in which case the drying and the screening are performed on different successive devices, a dryer and a screener.

The screening step enables the separation of the inorganic fraction from the rest of the material, and further using said inorganic fraction in the preparation of the product, for instance, in a external layer (or the surface) of a panel. Increasing the inorganic content in the surface of the panel faces improves dimensional stability and resistance to deformation - i.e. the product obtained may show features solving the bending problem associated with panels, specifically with fiber-based panels, in conditions of humidity and temperature change.

The dried treated cellulosic material can be compressed and heated in a product former such as in a mould, in a press or between drums, to produce rigid cellulosic products.

It is also proposed to deposit in overlapped layers different cellulosic material fractions, with different fiber lengths, in the mould, the press or in a conveyor passing between the drums, producing a rigid stratified cellulosic product.

The method of the present invention also proposes the mixing of additives which could include adhesives or, alternatively, the mixing of adhesive-free additives with at least one of the cellulosic material sections constitutive of the rigid stratified cellulosic product, previous to the overlapping of said different cellulosic material fractions.

Said additives or adhesive-free additives will not be present in other cellulosic material fractions constitutive of the same rigid stratified cellulosic product and/or will be different from the additives or the adhesive-free additives mixed with other cellulosic material fractions constitutive of the same rigid stratified cellulosic product.

The presence of adhesives on the additives is not required because the treated cellulosic material produces a sufficient bounding effect by itself when dried and compressed, but the use of adhesives could improve the resistance or other characteristics of the resulting cellulosic product.

Said additives or adhesive-free additives can be in solid or powder format and can be mixed with the cellulosic material fractions in that dry format, avoiding its dissolution and therefore being more effective.

Said additives or adhesive-free additives can also be in a liquid format, for example dissolved in water or in an organic solvent, which will be later added to the cellulosic material fractions for example by spraying.

One of the most common problems encountered by panel-shaped products made of cellulose fibers, which have been obtained with a dry forming process, is resistance to moisture. It is known in the state of the art that additivation processes of the products described in this application are carried out on dry matter, spraying the additive on the surface. This means that a large proportion of the fibers are not impregnated with the additive that provide, for instance, flexural strength among other properties. In the present invention, the raw cellulosic material is treated by reducing the consistency of the additives (i.e., by increasing their concentration) at the time of spraying the raw cellulosic material. The additive might be in a solvent such as water or a non-flammable solvent having a vapor pressure lower than 700 mmHg. The aim is not to increase the proportion of volatile solvents with high vapor pressure that may interfere with the shaping stage of the panel with pressure and temperature, but to improve the dispersion capacity of the active component of the additive on the raw cellulosic material.

Furthermore, it is known in the art the use of additives based on resins such as urea- formaldehyde (UF) or phenol-formaldehyde (PF). Resins are mostly used to provide good mechanical properties to the material. In the present invention, such resins are not used. Preferably, the additives according to the present invention do not comprise any kind of resin. At least 20% of the mechanical resistance showed by the cellulosic material obtained is provided by the bonds formed between the cellulosic fibers.

In any case, because the cellulosic material fractions are dry, no filtering step is required and therefore no water is disposed containing additives which will be lost. Therefore, all the additives mixed with the cellulosic material fractions are integrated in the stratified rigid cellulosic product, with no loss of additives and preventing the effluent sewage water containing additives.

A second aspect of the present invention is directed to an enzymatic treatment system adapted to perform the method described hereinabove. The proposed system comprises:

• an enzyme applicator configured to add enzymes to a raw fibrous cellulosic material;

• a stirrer including active stirring elements, which are configured to mix said raw fibrous cellulosic material and the enzymes, and a stirrer outlet;

• a dryer including a heater and a dryer outlet, said dryer being feed from the stirrer outlet.

The enzyme applicator is a device which distributes a controlled quantity of enzymes on a defined volume of raw fibrous cellulosic material, for example a batch of raw fibrous cellulosic material.

According to an optional embodiment, the enzyme applicator is a spray feed from one or several enzymes deposits.

The stirrer is a receptacle where the raw fibrous cellulosic material is stirred producing its uniform mixing with the enzymes. This is produced by active stirring elements contained in the stirrer, for example rotative blades which are movable at a velocity controlled by a control unit.

The dryer is a receptacle where the material is introduced and heated by a heater to produce its drying. Preferably the dryer includes a blower which blows heated air into the receptacle and agitation means which moves the material to be dried.

In a preferred embodiment the dryer is a hollow drum rotative around a horizontal axis, producing the tumbling of the material to be dried, and where the blower produces a circulation of heated air through said receptacle.

The system further comprises the following features:

• a screener connected to or integrated into the dryer outlet configured to screening different fiber sizes producing different fractions of a dried treated fibrous cellulosic material;

• a product former comprising a mold, a press or a conveyor passing between compression drums;

• a dosing device configured to deposit several overlapped layers of different fractions of dried treated cellulosic material on the product former. The screener separates the material dried on the dryer into different fractions depending on the size of its fibers. The screener can be for example, a trommel screen.

The screener can be integrated with a dryer outlet, for example, using different mesh sizes integrated into the walls of the dryer or it can be an independent screener device fed from the dryer outlet.

Preferably, the dryer and the screener are a single trommel screener, but it is also contemplated to use a successive dryer and screener, the dryer including an agitation device to avoid the agglomeration of the treated fibrous cellulosic material during the drying operation.

The product former is where the stratified rigid cellulosic product is shaped, using compression applied for example, by the press, mold or compression drums and heat from a heater.

The overlapped layers of different fractions of the dried treated cellulosic material are deposited on the product former, prior to the application of the pression and the heat, using a dosing device which provides layers of a controlled thickness of each fraction of the material laid one on top of another, according to a predefined design of the product.

The dosing device can include, for example, multiple application heads, one for each fraction to be applied. Each application head being feed fed from one deposit containing one fraction of the dried treated cellulosic material.

According to an alternative embodiment, multiple deposits, each containing a different fraction of the dried treated cellulosic material, are connected to the same application head.

Once molded, the rigid cellulosic product can be cooled to the ambient temperature within the mold using a cooling device to control the cooling process. Thus, avoiding possible deformations of the rigid cellulosic product produced during the cooling process.

According to a third aspect, the present invention is directed to a rigid cellulosic product, at least a proportion, preferably at least 20%, of the cellulosic fibres being derived from industrial waste.

Preferably, the rigid cellulosic product comprise multiple compressed overlapped layers. Each layer being made of cellulosic material with different fiber lengths that of the adjacent layers, defining a stratified rigid cellulosic product.

The resulting stratified rigid cellulosic product is made of cellulose material, which can be obtained from recycled cellulose material, and can easily be recycled. It will be as hard as some types of wood but also moldable. For example obtaining a flexural strength higher than 30 MP. The stratified rigid cellulosic product has a density equal to or higher than 0,5 g/cm3, but lower than 1, and presents other characteristics such as thermal and acoustic insulation, water-proof characteristics, dimensional stability, low density and high mechanical resistance.

The stratified rigid cellulosic product offers a fire behavior corresponding to a material from As1d0 to Cs1d0 according to EN 13501 standard.

The differential fiber lengths of the different overlapped layers, also provides other advantages, for example producing a front layer and an optional back layer with a differentiated fiber length than that of the other intermediate layers, provides different features to said front and back layer. For example less paint absorption, higher resistance, specific texture provided by the fibers if visible or by their absence if invisible by their size.

It should be understood that the front and the back layers are those layers exposed on the front and the back of the stratified rigid cellulosic product.

It is also proposed that at least one of the layers can include additives or adhesive-free additives different than the other layers of the stratified rigid cellulosic product. Moreover, the layers may include inorganic fillers.

This permits the functional or aesthetical differentiation of the different overlapped layers.

For example, one layer can be colored differently from the other layers. If the colored layer is the front layer and optionally also the back layer, then the stratified rigid cellulosic product can obtain a colored appearance using a small quantity of additive, because only the front and back layers are to be colored, then the thickness of those colored layers can be reduced.

The front and back layers and/or also the intermediate layers can include specific additives for improving, for example, the vapor barrier characteristics, the impact or scratch resistance, fire- retardant characteristics and others.

The additives can provide improved characteristics to the individual layers of the product. Because only one or some layers includes the additives, the concentration of additive can be higher on those layers with a reduced cost, the rest of the stratified rigid cellulosic product will not include such additives.

The cellulosic material contained in said rigid cellulosic product can be the dry treated cellulosic material obtained from the method described above.

It will also be understood that any range of values given may not be optimal in extreme values and may require adaptations to the invention where these extreme values are applicable, such adaptations being within the knowledge of a skilled person. The terms "residue" and "waste" are used interchangeably in the present invention when referred to a useless or profitless material.

The term "consistency” in the present invention refers to the percentage of dry raw cellulosic material (usually a residue) in a solvent (usually water).

Unless otherwise stated, the term "waste paper" is always referred to waste paper originated from high quality printed paper. The "waste paper" is structurally understood herein as natural polymers with cellulose base, such as paper cellulose, cotton, straw, etc. In a more preferred embodiment, this waste paper has ashes (between 15% and 40%) and cellulosic fibers (between 60% and 85%) which comprise short-fiber hardwood (between 70% and 80%) with long-fiber conifer (between 20% and 30%).

By waste paper originated from "high quality paper" is understood herein waste paper which cannot be repulped nor recycled in the paper and cardboard industry, such as offset-paper or high quality gravure, magazine paper with high concentrations of waterproofing resins and water-resistant inks.

Other features of the invention appear from the following detailed description of an embodiment.

Brief description of the Figures

The foregoing and other advantages and features will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, to be taken in an illustrative and non-limitative manner, in which:

Fig. 1 shows a schematic view of an embodiment of the enzymatic treatment system adapted to apply the proposed method for obtaining different fractions of the dried treated cellulosic material;

Fig. 2 shows the same enzymatic treatment system shown on Fig. 1 but also including a product former station for producing a stratified rigid cellulosic product.

Detailed description of an embodiment

The foregoing and other advantages and features will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, to be used in an illustrative and not limitative way. The enzymatic treatment system shown on Fig. 1 includes, in succession, the following working stations: a stirrer 20 which integrates an enzyme applicator 10, a dryer 30 and a screener 40 integrated in a trommel screener.

Fig. 2 shows a similar embodiment but further including a product former 50 feed by a dosing device 61 , 62, 63 after the screener 40.

Multiple paste or granular material conveyors, such as conveyor belts or screw conveyors, connecting working stations to transfer the cellulosic material through the proposed enzymatic treatment system.

A raw fibrous cellulosic material 1, at least a proportion of which is derived from industrial waste, for example sewage or primary sludge from the paper manufacturing industry and/or waste from the cellulosic manufacturing industry, is fed into the stirrer 20 where the enzymes 11 , 12, 13, 14 are added and mixed thereon by multiple active stirring elements 21, producing the enzymatic treatment within the stirrer 20 during a specific period of time.

In this embodiment the active stirrer elements 21 are parallel rotative blades contained in the stirrer 20.

According to this embodiment the enzyme applicator 10 comprises multiple spray nozzles contained in the stirrer 20, facing the upper surface of the raw fibrous cellulosic material 1 contained in the stirrer 20. The spray nozzles are fed, with liquid enzymes 11 , 12, 13, 14, or with liquid water solutions of enzymes 11 , 12, 13, 14 stored in separated deposits, it can also be fed with additional water.

A control unit 15 can regulate the amount of each enzyme 11, 12, 13, 14 added to the raw fibrous cellulosic material 1 , for example in response to a measurement of the specific composition of the raw fibrous cellulosic material 1 to be treated.

The water content of the raw fibrous cellulosic material 1 , once the enzymes 11 , 12, 13 and 14 have been added, shall be comprised of between 20% and 80% to obtain a sufficient flowability for stirring the minimal water content. The water contained in the added enzymes 11, 12, 13, 14 can be adjusted, or additional water can be added to the raw fibrous cellulosic material 1, for example through the spray nozzles. The flowability of the raw fibrous cellulosic material 1 and/or its water content is preferably measured or deduced from other measurements, for example from the energy consumption of the motor actuating the active stirring elements 21, or by an analysis of a sample.

The control unit 15 can automatically adjust the composition of the enzymes 11, 12, 13, 14 added to the raw fibrous cellulosic material 1, and/or the exact amount of water added to the raw fibrous cellulosic material 1 for example adding additional water, and/or operational parameters of the stirrer 20. Said operational parameters can be, for example, the movement velocity of the active stirring elements 21 and/or a heater 23 which heats the raw fibrous cellulosic material 1 contained in the stirrer 20.

According to this embodiment, the stirrer 20 includes a stirrer inlet on its top for the introduction of the raw fibrous cellulosic material 1 , and a stirrer outlet 22 on the bottom for the extraction of the treated cellulosic material, which is then transferred to the dryer 30 and screener 40.

Other alternative embodiments of the stirrer 20 are also contemplated. For example the stirrer 20 can be an horizontal rotative hollow drum with the stirrer inlet on one end and the stirrer outlet 22 on the opposite end, wherein the active stirring elements are blades attached to the inner side of the walls of the rotative drum and are configured not only for stirring but also for pushing the raw fibrous cellulosic material through the stirrer 20 from the stirrer inlet to the stirrer outlet 22 spending the specified period of time within the stirrer 20. This embodiment allows a continuous flow treatment process of the raw fibrous cellulosic material 1 in the stirrer 20.

The above mentioned trommel screener integrates the dryer 30 and the screener 40 and comprises of a rotative horizontal hollow drum including multiple successive meshes integrated into the walls of the rotative horizontal hollow drum.

The treated cellulosic material, with a water content comprised of between 20% and 80%, is introduced into the trommel screener through one end, and also air heated by a heater 31 is blown through the rotative horizontal hollow drum while the drum rotates, reducing the water content to produce treated cellulosic materials with water content below 20%.

The successive meshes have increasingly larger sized holes for screening different fractions 2, 3, 4 of the dried treated cellulosic material of increasingly longer fibers.

Those fractions 2, 3, 4, due to its water content is lower than 20% and can be stored for future use in a simple manner, or can be used immediately. One proposed use of the dried treated cellulosic material is the production of a rigid cellulosic product, or more preferably a stratified rigid cellulosic product 9 made of overlapped layers 5, 6, 7 of different fractions 2, 3, 4 in a product former 60.

According to the embodiment shown on Fig. 2, the product former 60 comprises a conveyor belt passing between two opposed compression drums.

Multiple successive application heads 61, 62, 62, constitutive of a dosing device 61 , 62, 63, are facing said conveyor belt. The first application head 61 deposits a front layer 5 of a controlled thickness of the stratified rigid cellulosic product 9 to be produced on the conveyor belt, the layer being made of a fraction 2 of the dried treated cellulosic material 2, 3, 4. Successive application heads 62, 63 deposit additional layers 6, 7 of controlled thicknesses of the stratified rigid cellulosic product 9 to be produced on top of the front layer 5.

When said overlapped layers 5, 6, 7 pass between the compression drums, they are compressed and heated by the compression drums, producing the stratified rigid cellulosic product 9, in this case as a flat panel.

More complex shapes can be obtained by using a mold or a press as a product former 50. In those cases the mold, the press, or the application heads 61 , 62, 63 can be moved in a controlled manner to produce a deposition of the overlapped layers covering the entire surface of the mold, previous to the closing of the mold and the application of the pressure and heat.

One or several of the fractions 2, 3, 4 can be mixed with an additive 8 or an adhesive-free additive 8 previous to its deposition onto the product former 50 to provide this specific layer with some improved features.

It will be understood that the present invention enables the use of fibres otherwise considered unusable to produce a new rigid cellulosic product. For fibres derived from primary sludge from the paper production industry, there is no possibility to reuse/recycle the fibres as the fibres contained by the sludge have short lengths, under 5mm or shorter still below 2mm. Moreover, primary sludge also includes high percentages of inorganic charges which reduces the mechanical properties. Prior to the screen aspect of the present invention, there was no way to efficiently separate inorganic charges from cellulosic fibers to enable subsequent use of those fibres.

In the case of textile industrial waste, the reason why previously there is no possibility to reuse them is different to fibres derived from primary sludge, and relates to the difficulty of disgregating or separating the mixed compositions of fibres found in textiles to subsequently re-use those fibres in new textile production.

Several examples of cellulosic products obtained with the proposed method are described below.

EXAMPLE 1

The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 75% (measured in dry weight) of industrial waste in the form of sewage sludge from the paper manufacturing industry and 25% (measured in dry weight) of waste cardboard.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is mixed with additives and used to produce a rigid cellulosic product with a density of 1,17 g/cm³ in the form of a 13,62mm thick panel.

The additive used is an acrylic binder which is a cross linkable, low formaldehyde binder (<100ppm free formaldehyde in the product) commercialized under the name of PRIMAL ECO- 15 R Acrylic binder.

The obtained panel has a flexural strength of 23,7MPa.

EXAMPLE 2

The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 75% (measured in dry weight) industrial waste in the form of sewage sludge from the paper manufacturing industry and 25% (measured in dry weight) from waste cardboard.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is mixed with additives and used to produce a rigid cellulosic product with a density of 1,14 g/cm³ in the form of a 6,6mm thick panel.

The obtained panel has a flexural strength of 16.5MPa.

EXAMPLE 3 The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 75% (measured in dry weight) industrial waste in the form of sewage sludge from paper manufacturing industry and 25% (measured in dry weight) of waste cardboard.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is mixed with additives and used to produce a rigid cellulosic product with a density of 1,23 g/cm³ in the form of a 13,62mm thick panel.

The obtained panel has a flexural strength of 26.7MPa.

It will be understood that the obtained panel of Example 3 has a higher forming pressure compared to the panel of Example 1 , resulting in a panel of higher density and mechanical properties such as flexural strength.

EXAMPLE 4

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is used, without additives, to produce a rigid cellulosic product with a density of 0,89 g/cm³ in the form of a 16,3mm thick panel.

EXAMPLE 5

The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 50% (measured in dry weight) of sewage sludge from the paper manufacturing industry and 50% (measured in dry weight) from waste cardboard.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is used, without additives, to produce a rigid cellulosic product with a density of 1 ,03 g/cm³ in the form of a 8,7mm thick panel.

The obtained panel has a flexural strength of 15.8MPa. EXAMPLE 6

The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises only industrial waste in the form of sewage sludge from the paper manufacturing industry.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is mixed with additives and used to produce a rigid cellulosic product with a density of 0,79g/cm³ in the form of a 13,79mm thick panel.

The additive used is an ecologic acrylic binder-based resin.

The obtained panel has a flexural strength of 27.4MPa.

EXAMPLE 7

The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 30% cellulosic residue (measured in dry weight) from the textile manufacturing industry and 70% (measured in dry weight) from waste cardboard.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is used without additives, to produce a rigid cellulosic product with a density of 0.79g/cm³ in the form of a 11mm thick panel.

The obtained panel has a flexural strength of 17.6MPa.

EXAMPLE 8

The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 90% (measured in dry weight) of sewage sludge from the paper manufacturing industry and 10% (measured in dry weight) from triturated (or ground or powdered) rigid cellulosic product of the present invention, that is, recycling cellulosic product to use as the cellulosic material in the enzyme treatment process to produce new cellulosic product.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is mixed with additives and used to produce a rigid cellulosic product with a density of 0.98 g/cm³ in the form of a 13mm thick panel.

The additive used is an ecologic acrylic binder-based resin.

The obtained panel has a flexural strength of 29.7MPa. EXAMPLE 9

The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 100% (measured in dry weight) from triturated (or ground or powdered) rigid cellulosic product of the present invention, that is, the new cellulosic product is fully derived from recycled cellulosic product. Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is used to produce a rigid cellulosic product with a density of 0.96 g/cm³ in the form of a 9.5mm thick panel.

The obtained panel has a flexural strength of 18.6MPa.

EXAMPLE 10 The raw fibrous cellulosic material 1 introduced in the stirrer 20 comprises 20% (measured in dry weight) industrial waste in the form of sewage sludge from the paper manufacturing industry and 80% (measured in dry weight) from waste cardboard.

Once the enzymatic treatment and the drying process have been completed, the resulting dried treated cellulosic material is used to produce a rigid cellulosic product with a density of 0.690 g/cm³ in the form of a 12mm thick panel.

The obtained panel has a flexural strength of 15.4MPa.

It will be understood that various parts of one embodiment of the invention can be freely combined with other parts described in other embodiments, even if this combination is not explicitly described, provided that such combination is within the scope of the claims and that there is no harm in such combination.

Claims

1. Enzymatic treatment method for fibrous cellulosic material comprising:

• introduction of raw fibrous cellulosic material (1) in a stirrer (20);

• enzymatic treatment of the raw fibrous cellulosic material (1) for a specific period of time to obtain a treated cellulosic material, said enzymatic treatment including the addition of enzymes (11, 12, 13, 14) to the raw fibrous cellulosic material and the uniform distribution of said enzymes in the raw fibrous cellulosic material by stirring;

• drying the treated cellulosic material; wherein at least a proportion of the raw fibrous cellulosic material (1) is derived from industrial waste.

2. The enzymatic treatment method of claim 1) wherein the raw fibrous cellulosic material derived from industrial waste has fibers having one or more of an average length of less than 5mm, preferably less than 2mm, and/or an average width of less than 0.1mm, and/or a mass percentage of fines greater than 10%.

3. The enzymatic treatment method of any claim 1 or 2 wherein the raw fibrous cellulosic material derived from industrial waste comprises other compounds.

4. The enzymatic treatment method of any preceding claim wherein the industrial waste is one or more of primary sludge obtained from the paper production industry, preferably with fibers having an average length of less than 5mm, most preferably less than 2mm, residues from the textile production industry, or cellulosic construction waste.

5. The enzymatic treatment method of any preceding claim, wherein the raw fibrous cellulosic material has a water content comprised between 20% and 80% by weight with respect to the total amount of raw fibrous cellulosic material after the addition of the enzymes (11 , 12, 13, 14) and the water content is maintained within said range during the enzymatic treatment.

6. The enzymatic treatment method according to any preceding claim, wherein operational parameters of the stirrer (20) are configured to produce, on the raw fibrous cellulosic material (1), dynamic currents affecting all of the raw fibrous cellulosic material (1) contained on the stirrer (20).

7. The enzymatic treatment method according to claim 6, wherein the operational parameters include a movement velocity of multiple active stirring elements (21) which are contained in the stirrer (20) for stirring raw fibrous cellulosic material (1) and/or the temperature of the raw fibrous cellulosic material (1).

8. The enzymatic treatment method according to claim 6 or 7 wherein the enzymatic treatment of the raw fibrous cellulosic material (1) is carried out in the presence of a dense gas, preferably sulfur hexafluoride.

9. The enzymatic treatment method according to any preceding claim wherein:

• the added enzymes (11, 12, 13, 14) are selected to smooth the fibers, to remove radicals from the outside of the fibers and to increase the specific surface area of the fibers and/or comprise xylanase, laccase, cellulase and/or combinations thereof.

10. The enzymatic treatment method according to any preceding claim wherein:

• the raw fibrous cellulosic material (1), during the enzymatic treatment, is maintained with a pH comprised between 5 and 9 and/or with a temperature comprised between 40°C and 70°C; and/or

• the enzymatic treatment is produced within the stirrer (20) and wherein the specific period of time is comprised between 15 and 60 minutes; and/or

• the dried treated cellulosic material (2, 3, 4) has a water content below 50%, preferably below 20%.

11. The enzymatic treatment method according to any preceding claim wherein the enzymes (11, 12, 13, 14) are liquid or dissolved in liquid and are sprayed on to the raw fibrous cellulosic material (1).

12. The enzymatic treatment method according to any preceding claim wherein the composition of the raw fibrous cellulosic material (1) introduced in the stirrer (20) is analyzed, and the proportions of the different enzymes (11, 12, 13, 14) added are adjusted in response to the result of said analysis.

13. The enzymatic treatment method according to any preceding claim wherein the dried treated cellulosic material (2, 3, 4) is screened and separated in different fractions (2, 3, 4) by fiber sizes during the drying step, or during the drying step by a trommel screen or after the drying step.

14. The enzymatic treatment method according to any preceding claim wherein the dried treated cellulosic material is screened to produce an inorganic fraction separate from the remainder of the dried treated cellulosic material.

15. A method of forming a rigid cellulosic product comprising the steps of: applying the enzymatic treatment method of any preceding claim to fibrous cellulosic material, and compressing and heating the cellulosic material to form a rigid cellulosic product.

16. A method of forming a rigid cellulosic product according to claim 15, wherein the step of compressing the cellulosic material is one of moulding, preferably injection moulding, or pressing in a press or between drums.

17. A method of forming a rigid cellulosic product according to claims 15 or 16 wherein the method is a continuous method.

18. A method of forming a rigid cellulosic product according to any one of claims 15 to 17 wherein different cellulosic material fractions (2, 3, 4), with different fiber lengths, are deposited in overlapped layers (5, 6, 7), compressed and heated in a product former (50) including a mold, a press or a conveyor passing between compression drums, producing a rigid stratified cellulosic product (9).

19. A method of forming a rigid cellulosic product according to claim 18 wherein additives (8) or adhesive-free additives (8) are mixed with at least one of the cellulosic material fractions (2, 3, 4) constitutive of the rigid stratified cellulosic product (9); the additives (8) or adhesive-free additives (8) not being present in other cellulosic material fractions (2, 3, 4) constitutive of the same rigid stratified cellulosic product (9), or the additives (8) or adhesive-free additives (8) being present in other cellulosic material fractions (2, 3, 4) constitutive of the same rigid stratified cellulosic product (9) and being the same or different from the additives (8) or the adhesive-free additives (8) mixed with other cellulosic material fractions (2, 3, 4) constitutive of the same rigid stratified cellulosic product (9).

20. A method of forming a rigid cellulosic product according to any one of claims 15 to 19 when dependent on claim 14, wherein different cellulosic material fractions are deposited in overlapped layers, compressed and heated in a product former (50) including a mold, a press or a conveyor passing between compression drums, producing a rigid stratified cellulosic product (9), wherein at least one of the overlapped layers defining an external surface layer of the rigid cellulosic product comprises at least a proportion of the inorganic fraction.

21. Enzymatic treatment system adapted to perform the method according to any one of claims 1 to 20 comprising:

• an enzyme applicator (10) configured to add enzymes (11 , 12, 13, 14) to a raw fibrous cellulosic material (1);

• a stirrer (20) including active stirring elements (21), which are configured to mix the raw fibrous cellulosic material (1) and the enzymes (11, 12, 13, 14), and a stirrer outlet (22); • a dryer (30) including a heater (31) and a dryer outlet, said dryer (30) being feed from the stirrer outlet (22);

• a screener (40) connected to or integrated into the dryer outlet configured to screening different fiber sizes producing different fractions of a dried treated fibrous cellulosic material;

• a product former (50) comprising a mold, a press or a conveyor passing between compression drums; and

• a dosing device (61 , 62, 63) configured to deposit several overlapped layers of different fractions of dried treated cellulosic material on the product former (50).

22. The enzymatic treatment system according to claim 21 wherein enzyme applicator (10) is a spray feed from one or several enzymes deposits and/or wherein the dryer (30) and the screener (40) are a single trommel screener.

23. Rigid cellulosic product comprising compressed enzyme-treated fibrous cellulosic material derived from industrial waste.

24. Rigid cellulosic product according to claim 23 comprising multiple compressed overlapped layers (5, 6, 7), each layer (5, 6, 7) being made of cellulosic material with different fiber lenghs than the adjacent layers (5, 6, 7).

25. Rigid cellulosic product according to claim 24 wherein at least one of the layers (5, 6, 7) includes additives (8) or adhesive-free additives (8) that are different from the additives (8) or adhesive-free additives (8) included in the other layers (5, 6, 7).

26. Rigid cellulosic product according to any one of claims 23 to 24 wherein at least one of the layers (5, 6, 7) has a density that is different from the other layers (5, 6, 7).

27. Rigid cellulosic product according to one of claims 23 to 26 wherein the enzyme-treated fibrous cellulosic material is produced by the process of any one of claims 1 to 14.

28. Rigid cellulosic product according to any one of claims 23 to 26 wherein the enzyme-treated fibrous cellulosic material is substantially lignin free.

29. Rigid cellulosic product according to any one of claims 23 to 28 wherein at least 20% of the enzyme-treated fibrous cellulosic material is derived from industrial waste.

30. Enzymatic treatment method for fibrous cellulosic material wherein at least a proportion of the fibrous cellulosic material is derived from triturating the rigid cellulosic product of claims 23 to 29 or produced by the method of claims 15 to 20.

31. Rigid cellulosic product comprising at least the proportion of the cellulosic material derived from the enzymatic treatment method of claim 30.

32. Rigid cellulosic product according to claim 31 wherein the proportion of the cellulosic material derived from the enzymatic treatment method of claim 30 is greater than 10%, preferably 100%.