Powdered substrate obtained by steam cracking of biomass without chemical auxiliaries and its use

Abstract

The present invention relates to energy substrates obtained by steam cracking of biomass. More specifically, the invention relates to steam cracked biomass in the form of a dry powder and free of any chemical additives, to a method for its production, and to its use as a substrate for green chemistry and biotechnological processes, such as enzymatic hydrolysis and fermentation.

Description

Detailed Description of the Invention

[0001] The present invention relates to an energy substrate obtained by steam cracking of biomass. More specifically, the present invention relates to steam cracked biomass in the form of a dry powder and free of any chemical additives, its production process and its use as a substrate for green chemistry and biotechnological processes, such as enzymatic hydrolysis and fermentation.

[0002] [Technical field] Biotechnological or green chemistry methods use carbon substrates derived from intensively and cost-effectively produced plant food materials. LCA (life cycle analysis) of the substrates, food competition, and feedstock prices generally hinder the development of these biosourced products and bioeconomy. The use of "second generation" (2G) lignocellulosic biomass (wood, agricultural waste, agricultural and agro-industrial by-products) could reduce the environmental impact (fossil CO2 emissions, fertilizer, plant health) as well as the use and price competition in the food sector.

[0003] Numerous projects on this subject have been undertaken since 2006 (120 worldwide). The principle is the steam explosion of biomass. In most of them, chemical auxiliaries such as sulfuric acid or alkaline ammonia are added. All use the "wet" method, moistening the biomass to a moisture content of 40-70%. Once exploded, the material is either detoxified or used directly, adding enzymes that hydrolyze the sugar polymers and then, simultaneously or subsequently, microorganisms to convert the released sugars into the desired molecules.

[0004] Steam cracking differs from hydrothermal pretreatment (also called steam cracking, solvolysis, hydropyrolysis, or hydrothermal treatment) in that it involves the use of water under high temperature and pressure to promote the breakdown and separation of the lignocellulosic matrix.

[0005] Thus, industrial-scale methods for converting lignocellulosic biomass that are technically feasible and economically viable in addition to having a favorable risk-free environmental history are scarce. Today, ethanol is emerging as one of the few biotechnology commodities based on lignocellulose.

[0006] [Prior Art] Document WO2013 / 018034A1 relates to a method for producing a substrate for growing mushrooms. The production of the substrate can be carried out using various processing methods, in particular the processing method of steam explosion. The process of using the steam explosion method is as follows: First, the lignocellulosic material is crushed and then placed in a reactor where the biomass is heated by steam to a temperature of 160 ° C to 230 ° C. After a pressure of 12 to 28 atmospheres is reached in the reactor, the pressure in the reactor is reduced to atmospheric pressure and a steam explosion is carried out.

[0007] Document WO2013 / 105034 describes a method for treating lignocellulosic biomass to obtain a liquid composition. The treatment of the biomass is characterized by a soaking step to obtain a solid fraction and a liquid fraction. Then, a part of the liquid fraction is separated, while the other fraction (a part of the solid fraction and the liquid fraction) undergoes a steam explosion step on the solid fraction to obtain again the solid fraction and the liquid fraction. Finally, the newly obtained liquid fraction is mixed with the solid fraction obtained in the initial (first) step.

[0008] Document WO2013 / 152771 relates to a method for the treatment of lignocellulosic biomass to produce biofuels such as ethanol, butanol, hydrogen, methanol and biogas, which is carried out under pressure by mechanical non-adiabatic decomposition using a technique based on the properties of mechanical steam explosion.

[0009] Documents FR2997094A1 and WO2014 / 060673A1 respectively describe processes for the production of so-called "second generation" ethanol from lignocellulosic biomass and for the production of so-called "second generation" alcohol from lignocellulosic biomass, which comprise different steps: (i) pretreatment in a reactor by steam explosion, (ii) a subsequent enzymatic hydrolysis step of the pretreated substrate, (iii) then an ethyl fermentation step of the solubilized sugars, (iv) then extraction of ethanol or alcohol from the fermentation effluent, and (v) recycling of the internal aqueous stream containing ethanol or alcohol in an upstream or pretreatment reactor.

[0010] Documents WO2014 / 204519A1 and WO2013 / 191897A1 describe the treatment of biomass using steam explosion prior to gasification or as a pretreatment prior to combustion.

[0011] Finally, document EP 3054050A describes a method for the continuous treatment of lignocellulosic feedstock to produce a dehydrated lignocellulosic feedstock having a moisture content in a first target range (65% to 85%). The method may include a step of steam explosion at a severity factor of 2.8 to 5.3.

[0012] [Disadvantages of the prior art] Most of these methods are hampered by technical and economic problems, namely the use of chemical auxiliaries (acidic or alkaline) at a certain cost of use. These chemical auxiliaries are used, for example, for pretreatment by increasing the severity and for neutralizing the pH for the use of biological auxiliaries (enzymes, microorganisms). Moreover, said auxiliaries enhance the chemical degradation of sugars, resulting in losses of yield as well as the production of inhibitors of microorganisms and enzymes used in biotechnological methods or green chemistry, leading to an overconsumption of said auxiliaries or the need to separate contaminants from the final product. Moreover, even without auxiliaries, the dilution of the biomass by impregnation causes an increase in the energy costs of the thermal treatment and a decrease in the substrate titer, which dilution increases the expenses (costs) during the purification process (extraction or distillation, etc.). Finally, these methods are expensive in terms of (tangible and intangible) capital expenditure (CAPEX) and operational expenses (OPEX) spent on the purchase of dedicated equipment.

[0013] Moreover, the solutions proposed by the prior art include those in which the severity factor is not an established parameter. However, the severity factor is important because, depending on its intensity, it makes it possible to obtain different compounds. Furthermore, the prior art solutions propose methods that have high moisture levels for the initial biomass and that are not run continuously. To date, there is no biomass preparation method for high added value applications that is viable from an industrial and economic point of view.

[0014] [Disclosure of the Invention] The present invention provides a carbon substrate that does not contain added acidic or alkaline compounds and is "ready-to-use" for implementation in biotechnological, chemical, or green chemistry processes. The substrate is prepared by continuous steam cracking of dry lignocellulosic biomass without the addition of chemical supplements.

[0015] The invention also aims to reduce production costs, for example by removing intermediate products from the final product (powder or "granules", i.e. pellets of average compaction density) in parallel with the primary use (black pellets) and by using the intermediate products as substrates for hydrolysis (sugars for green chemistry) or substrates for hydrolysis and fermentation (sugars for biotechnology).

[0016] The present invention therefore relates to a chemically reactive powdered carbon substrate obtained by continuous steam cracking of lignocellulosic biomass without the use of any auxiliary agents, to compositions containing such substrates, and to their uses.

[0017] [Advantages of the present invention] The method is economically viable for commodities such as energy, and therefore even more so for higher value-added products. The resulting carbon substrate is stable.

[0018] The economic aspect is essential. Continuous and dry operation allows to reduce the size of the equipment parts (continuous flow) and the volumes to be treated (dry flow), thus reducing CAPEX. The absence of technical chemical auxiliaries limits losses due to degradation, reduces costs (OPEX) in terms of purchase costs and the effort required for neutralization, as well as in terms of contamination to be treated, and also protects the equipment from corrosion (CAPEX). The input biomass is only subjected to thermal and mechanical deformations and is therefore not adjuvanted. It therefore maintains its "natural" primary quality and, moreover, is less expensive to produce than when using wet chemical methods (40% to 70% humidity) in the thermal treatment. Finally, it comes from an established industrial method, viable and robust, that allows access to volumes of biomass prepared by steam cracking that allow economies of scale, i.e. a reduction in OPEX and CAPEX.

[0019] Another advantage of the method for producing the powdered substrate according to the invention is that it does not involve any chemical treatment (especially acidic) and therefore does not produce effluents. The substrate is stable and can be stored and transported. It can be enzymatically hydrolyzed to 50% to 70% despite the absence of acidic or alkaline pretreatment. Finally, the product is inexpensive, does not require the use of water or effluents, is derived from inexpensive commodity products and can be used to produce high value-added products.

[0020] The powdered carbon substrate according to the present invention is advantageously used for the production of by-products such as sugars and lignin.

[0021] The steam-cracked biomass in powder form can be utilized for sugars such as xylose by chemical release and for pre-treated cellulose fractions that can be hydrolyzed by cellulolytic enzymes to form simple sugars that can then be converted chemically or by bioconversion / fermentation into higher value-added molecules in the fields of biotechnology and green chemistry.

[0022] Detailed Description of the Invention The first object of the present invention relates to a powdered carbon substrate for chemical or biochemical reactions obtained by continuous steam cracking of lignocellulosic biomass at moisture levels between 5% and 27% without the use of any chemical auxiliary agents.

[0023] In a preferred embodiment, steam cracking is carried out by applying a severity factor in the range of 3-5.

[0024] As defined herein, a "chemical reaction" refers to any reaction, including traditional chemical conversions as well as biochemical reactions such as fermentation, enzymatic hydrolysis, biotechnological processes, etc. The concept of a chemical reaction does not include combustion reactions.

[0025] In the present definition, "pulverulent substrate" means a substrate in the form of a powder or in the form of pellets, or pellets with a low degree of compaction, also called "granulettes". Said granules correspond to the form of compressed powders, giving said powders the form of pellets, but releasing them quickly upon immersion (less pelleting). This form can be adopted in the packaging of the product to facilitate its handling, but from the moment the substrate is impregnated by a solution (enzyme, acid, etc.), it has the properties of a powder.

[0026] The biomass powder obtained by steam cracking contains at least 50% of powdered compounds having a cross section of less than 0.5 millimeters and at least 10% of fibrous compounds having a length of more than 1 millimeter.

[0027] The pellets are cylindrical in shape. Their length can be defined as 99.9% less than 5 cm, 99.0% less than 4 cm, and less than 10% less than 1 cm. Furthermore, at least 99.0% of the pellets have a selected diameter, i.e., a diameter of 6 mm, 8 mm, or 10 mm or greater. Finally, their bulk density (obtained by tapping a cylinder having a volume of 5 liters of pellets three times by dropping it from a height of 20 cm) is between 600 g / l and 700 g / l.

[0028] Granules have dimensions similar to pellets, but have a density less than 600 g / l, typically between 300 and 600 g / l.

[0029] Said powdered substrate is particularly suitable for carrying out biochemical reactions such as enzymatic hydrolysis, fermentation, or any other chemical or biochemical reaction.

[0030] The fact that the substrate is present in powder form means that it is in dry form, preferably with a moisture content of between 5% and 27%. This characteristic distinguishes it from other forms of biomass used in biochemical reactions, which are in liquid form. Indeed, prior art biomass is impregnated, in particular with chemical auxiliaries, before treatment and is treated in liquid after steam cracking to remove said auxiliaries. This necessarily leads to problems in preserving the biomass to be fermented, even if the properties it exhibits in liquid or wet form are suitable for biochemical applications.

[0031] The substrate according to the invention therefore has the advantage of being dry, consisting for example of a biomass with a moisture content of preferably 5-27% (directly or optionally after drying), prepared by steam cracking without prior impregnation, and furthermore, this method does not involve the addition of chemical auxiliaries (or additives) and produces a clean substrate.

[0032] In the present definition, "chemical auxiliary" means any compound or any solution that may remain in the steam cracking product or in the effluent. Said auxiliary generates impurities in terms of use in the steam cracking product and contaminants in the rejected effluent. Chemical auxiliary of this kind are, for example, acids, bases, organic solvents or molecules, salts, etc. Products such as lime, carbon dioxide and renewable separated forms of carbon dioxide are not considered as chemical auxiliary since they are inert to the intended use and to the environment.

[0033] The severity factor depends on the pressure, temperature and duration of treatment. In a preferred embodiment, the severity factor is between 3 and 5. In a particular embodiment of the invention, the severity factor corresponds to a treatment for several minutes, typically between 5 and 30 minutes.

[0034] A second object of the invention relates to a "ready-to-use" dry composition comprising a powdered substrate as defined above and at least one enzyme.

[0035] The dry composition can be stored and shipped and is stable.

[0036] Once the biomass is impregnated, the enzymes allow the user to hydrolyze the biomass: in fact, the enzymes in a dry environment (biomass in powder form) are inactive and their activation is initiated by wetting the composition, in fact by soaking.

[0037] The enzymes that can be associated with the biomass in this type of composition can be chosen, for example, from cellulases, β-glucosidases, hemicellulases, etc.

[0038] A third object of the invention relates to a "ready to use" dry composition comprising a powdered substrate as defined above and at least one microorganism.

[0039] The dry composition can be stored and shipped and is stable.

[0040] Once the biomass is impregnated, the microorganisms allow the user to hydrolyze the biomass: in fact, the microorganisms in a dry environment (the biomass in powder form) are inactive and their metabolism is activated by wetting the composition, in fact by soaking.

[0041] The microorganisms associated with the substrate may be of different types, in particular microbial biomass or microalgae. The microbial biomass may include bacteria, yeasts, fungi or any other type of cells.

[0042] In a particular embodiment, the present invention relates to a "ready to use" dry composition comprising a powdered substrate, at least one enzyme, and at least one microorganism.

[0043] A third object of the invention relates to the use of a substrate as defined above as a substrate for a chemical reaction.

[0044] In certain embodiments, the substrate is used as a production substrate for microbial culture.

[0045] A substrate may be used to provide the microorganisms that make up the biomass with the nutrients they need to grow. To grow the microorganisms, it is sufficient to mix a sample of the biomass with the substrate under suitable conditions (humidity, temperature, etc.).

[0046] A fourth object of the present invention relates to a method for obtaining sugars from lignocellulosic biomass, which method consists of (i) subjecting a powdered carbon substrate to enzymatic hydrolysis or (ii) culturing a "ready-to-use" dry composition comprising a powdered substrate and an enzyme.

[0047] Substrates derived from biomass may be subjected to enzymatic hydrolysis to provide high value sugars such as xylose, glucose, etc.

[0048] In addition, the enzymatic and fermentation reactions produce highly exploitable by-products such as hydrolysis or fermentation residues containing lignin and fiber with useful LCVs, resin or terpene derivatives, phenolic compounds (coumaric compounds, ferulic compounds), condensates rich in furaldehyde (polymerization monomers), acetic acid and formic acid, etc. Soluble or insoluble lignin by-products can be used as materials (resins, binders, feedstocks).

[0049] A fifth object of the present invention relates to a method for obtaining molecules of interest from lignocellulosic biomass, which consists of (i) subjecting a powdered carbon substrate to fermentation, (ii) culturing a "ready-to-use" dry composition comprising the powdered substrate and at least one microorganism, or (iii) subjecting the powdered substrate to (conventional) chemical conversion methods.

[0050] The resulting molecules of interest are intended for example in the fields of bioenergy (biofuel oils such as bioethanol, biomethanol, biomethane, biogas, etc.), bioplastics (biomaterials, biosynthetics) or bioproducts (proteins, solvents, any other chemical molecules, etc.).

[0051] The substrates according to the invention can be applied in a variety of applications, in particular to manufacturers who wish to produce bioethanol and isobutane as well as farnesene to produce liquid biofuels (in particular biofuel oils for light or heavy vehicles, such as those offered by BP, SHELL, and for the aviation industry, such as those offered by TOTAL), to produce basic synthons (building blocks) for industry, bioplastics or bioproducts (methane, methanol, formic acid, formaldehyde, ethanol, ethylene, acetic acid, oxalic acid, ethanal, propanedioic acid, acetone, popionic acid, lactic acid, etc.). It can be used by biotechnologists looking to ferment 2G-sugars (glucose and xylose from cellulose) to obtain 2G-saccharides (such as glycerol, ...

[0052] A sixth object relates to a process for the continuous preparation of a powdered substrate for a chemical reaction as defined above, by steam cracking of lignocellulosic biomass, carried out at a moisture level between 5 and 27% and without the use of chemical auxiliaries.

[0053] In a preferred embodiment, the method allows for the preparation of powdered substrates for chemical reactions other than combustion.

[0054] [Example] <Example 1: Implementation of steam decomposition method to obtain powdered carbon substrate> A powdered carbon substrate according to the invention can be produced starting from wood by carrying out the following steps.

[0055] (i) obtaining wood chips of size between 0.5 and 14 mm having a moisture level between 5 and 27%; (ii) continuously introducing the obtained wood chips at a predetermined volume per minute into a pressurized reactor supplied with nearly saturated water vapor; in this process, the pressure is 10-25 bar and the temperature is 180-220°C; (iii) exposing the wood chips introduced into the reactor to the steam for a period sufficient to achieve steam cracking of between 5 and 30 minutes; the value of the exposure period and the value of the temperature of the nearly saturated steam are selected such that the severity factor is between 3 and 5, preferably between 3.5 and 4; (iv) continuously extracting the same predetermined volume per minute of wood chips from the reactor through a plurality of openings leading to a channel at about atmospheric pressure, causing an explosive decompression in the channel on the wood chips extracted from the reactor; (v) separating the extracted steam cracked powder and residual steam from the reactor; the steam cracked wood powder obtained after separation forms the powdered substrate.

Claims

1. a powdered carbon substrate production step, comprising continuously steam cracking lignocellulosic biomass having a moisture level of 5% to 27% by applying a severity factor ranging from 3 to 5 without the use of any chemical adjuvant to obtain a powdered carbon substrate for chemical or biochemical reactions; a step of adding at least one microorganism to said powdered carbon substrate to obtain a "ready to use" dry composition; The present invention relates to a method for producing a "ready-to-use" dry composition, comprising:

2. 2. A method for producing a "ready-to-use" dry composition according to claim 1, comprising adding at least one enzyme.

3. A method for producing a "ready-to-use" dry composition according to any one of claims 1 to 2, wherein the microorganism is a microbial biomass.

4. The method for producing a "ready-to-use" dry composition according to any one of claims 1 to 2, wherein the microorganism is a microalgae.

5. A method for producing a "ready to use" dry composition according to claim 1, using said powdered carbon substrate as a substrate for a chemical reaction.

6. 2. A method for producing the "ready to use" dry composition of claim 1, which uses the powdered carbon substrate as a production substrate for the cultivation of a microorganism.

7. 1. A method for obtaining sugars from lignocellulosic biomass, comprising: Cultivating a dry composition according to any one of claims 2 to 4.

8. 1. A method for producing a molecule of interest, comprising: Cultivating a dry composition according to any one of claims 2 to 6.

9. 10. The method of claim 8, wherein the molecule of interest is directed to the fields of bioenergy, bioplastics, or bioproducts.