Method for treating complex waste

Abstract

The invention relates to a method for treating a mixture M1 comprising at least organic matter, the method comprising: a. a step of pressurising the mixture M1 to a pressure ranging from 1 to 100 bar, in order to obtain a mixture stream M1p; b. a step of hydrolysing at least one fraction of the mixture M1p in the presence of supercritical carbon dioxide, in order to obtain a hydrolysed mixture stream M1h; c. a step of treating at least one fraction of the hydrolysed mixture stream M1h, the treatment step allowing a stream of liquid carbon dioxide CO2liq1 to be obtained; d. a step of pressurising and / or heating at least one fraction of the liquid carbon dioxide CO2liq1 downstream of the treatment step c), in order to obtain all or part of the supercritical carbon dioxide used in step b).

Description

Complex waste treatment process Technical field of the invention

[0001] The invention relates to the field of treatment of complex waste, comprising organic matter and inorganic matter, such as aqueous waste, sludge and sewage sludge. State of the art

[0002] In a context of climate change and scarcity of resources, the search for treatment processes that make it possible to best recover the energy from the various waste products produced by human activity is in full development.

[0003] Biomass and waste containing organic matter can be recovered for energy by decomposing the organic fraction to produce biogas, a fuel with high energy value, which is mainly composed of methane (50 – 60%) and CO2 (40 – 50%).

[0004] This energy conversion of the organic fraction of waste is carried out by biochemical technologies, in particular anaerobic digestion, or by thermochemical technologies such as thermal processes (combustion, pyrolysis, etc.) or hydrothermal processes (hydrothermal liquefaction / gasification, etc.).

[0005] These processes do not always provide optimum performance.

[0006] Pretreatments have been proposed to improve the processes.

[0007] The most widely applied pretreatments can be classified into three general categories: - thermal methods (e.g. thermal hydrolysis), - physical or mechanical methods (e.g. ultrasonication, high pressure homogenization, etc.), - and chemical techniques (alkaline or acid pretreatment, oxidation by ozonation, etc.).

[0008] The object of the present invention proposes to facilitate the conversion and improve the production yield of biogas, thanks to a method of pretreatment of biomass and complex waste making it possible both to optimize the treatment itself and the energy expenditure while using the co-product of these energy conversions, which is CO2.

[0009] The invention relates to a method for treating a mixture M1 comprising at least organic matter, said method comprising:a. pressurizing the mixture M1 to a pressure ranging from 1 to 100 bars, in order to obtain a mixture stream M1p,b. a step of hydrolysis of at least a fraction of the mixture M1p in the presence of supercritical carbon dioxide, in order to obtain a hydrolyzed mixture stream M1h,c. a treatment step allowing biogas production and carried out on at least a fraction of the hydrolyzed mixture stream M1h, said treatment step making it possible to obtain a liquid carbon dioxide stream CO2liq1,d. a pressurizing and / or heating step carried out on at least a fraction of the liquid carbon dioxide CO2liq1 downstream of treatment step c) in order to obtain all or part of the supercritical carbon dioxide used in step b).

[0010] According to one embodiment, the method comprises one or more of the following features: - at least a fraction of the liquid carbon dioxide from step c) is introduced into one or more storage devices, the pressurizing and / or heating step d) then being carried out downstream of the storage device(s); and / or - at least a fraction of the carbon dioxide used during the hydrolysis is recovered downstream of the hydrolysis to be reused during the pressurizing and / or heating step d), where appropriate after storage in one or more storage devices; and / or - at least a fraction of the carbon dioxide used during the hydrolysis is recovered downstream of the hydrolysis to be reintroduced directly at the hydrolysis inlet; and / or - the mixture M1 comprises from 5 to 50% by weight of solid matter, preferably from 15 to 35% by weight of solid matter, relative to the total weight of the mixture M1.

[0011] According to one embodiment, the treatment of step c) is a hydrothermal gasification, preferably carried out at a temperature ranging from 350°C to 700°C, preferably from 400°C to 600°C, more preferably from 450°C to 550°C, and / or at a pressure ranging from 200 to 450 bars, preferably from 250 to 300 bars.

[0012] According to a first embodiment, the hydrothermal gasification makes it possible to obtain a flow M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- a hydrothermal gasification carried out on at least a fraction of the mixture flow M1h, making it possible to obtain a flow M4 and optionally a flow M3 comprising mineral matter,- a step of cooling and expansion of at least a fraction of the flow M4 to a temperature ranging from 30 to 150°C, preferably from 50 to 100°C, and to a pressure ranging from 1 bar to 100 bars, making it possible to obtain on the one hand a gas flow M5 and on the other hand a liquid flow M7,- a step of separation of at least a fraction of the gas flow M5 making it possible to obtain on the one hand a flow enriched in carbon dioxide M6 and on the other hand a flow depleted in carbon dioxide 71,- a liquefaction step of at least a fraction of the M6 ​​flow,making it possible to obtain the flow of liquid carbon dioxide CO2liq1 on the one hand and a gaseous flow 81 on the other hand, at least a fraction of said flow of liquid carbon dioxide CO2liq1 is implemented during step d) of pressurization and / or heating, where appropriate after storage in one or more storage devices.,

[0013] According to a second embodiment, the hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- a hydrothermal gasification carried out on at least a fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter,- a step of cooling at least a fraction of the stream M4 to a temperature ranging from 0 to 90°C, preferably from 10 to 70°C, preferably from 25 to 50°C, making it possible to obtain on the one hand a gas stream M8 and on the other hand a liquid stream M9, the liquid stream M9 being at a pressure ranging from 150 to 350 bars,- a step of expanding at least a fraction of the liquid stream M9 to a pressure ranging from 35 bars to 100 bars making it possible to obtain on the one hand a stream enriched in liquid carbon dioxide CO2liq1 and on the other hand a liquid flow M10 depleted in carbon dioxide,at least a fraction of said liquid carbon dioxide stream CO2liq1 is implemented during step d) of pressurizing and / or heating, where appropriate after storage in one or more storage devices, preferably, according to this second embodiment, said method further comprises: - a separation step implemented on at least a fraction of the gas stream M8, making it possible to obtain on the one hand a stream enriched in carbon dioxide M12 and on the other hand a stream depleted in carbon dioxide M11, - an expansion step implemented on at least a fraction of the stream M12 up to a pressure ranging from 35 to 100 bars, making it possible to obtain on the one hand a stream enriched in liquid carbon dioxide CO2liq1' and on the other hand a liquid stream M13 depleted in liquid carbon dioxide, at least a fraction of said liquid carbon dioxide stream CO2liq1' is implemented during step d) of pressurizing and / or heating,where applicable after storage in one or more storage devices.,

[0014] According to one embodiment, step d) comprises at least one heat exchange step between at least a fraction of the M4 stream from the hydrothermal gasification step and the liquid carbon dioxide stream upstream of the hydrolysis and where appropriate downstream of the storage device, said heat exchange thus making it possible to at least partially heat the liquid carbon dioxide and making it possible to at least partially cool the M4 stream.

[0015] According to one embodiment, the hydrothermal gasification step comprises a preliminary step of heating the mixture flow M1h, said preliminary heating step comprising at least one sub-step of heat exchange between at least a fraction of the flow M4 from the hydrothermal gasification step and the flow M1h, said heat exchange thus making it possible to at least partially heat the mixture M1h and to at least partially cool the flow M4, in order to obtain a flow M4'.

[0016] According to this embodiment, the method preferably further comprises a heat exchange between the M4' stream and the liquid carbon dioxide stream upstream of the hydrolysis and where appropriate downstream of the storage device, said heat exchange thus making it possible to at least partially heat the liquid carbon dioxide and making it possible to at least partially cool the M4' stream in order to obtain a M4' stream.

[0017] According to one embodiment, the treatment of step c) is a digestion, said treatment comprising:- a digestion carried out on at least a fraction of the mixture flow M1h, making it possible to obtain a gas flow M14,- a separation step carried out on at least a fraction of the gas flow M14 making it possible to obtain a carbon dioxide-enriched flow M16 and a carbon dioxide-depleted flow M15,- a liquefaction step carried out on at least a fraction of the carbon dioxide-enriched flow M16, making it possible to obtain a liquid carbon dioxide flow.

[0018] The invention also relates to an installation for implementing a treatment method according to the invention, said installation comprising:- at least one pressurizing pump 1, comprising a flow outlet line M1p,- at least one hydrolysis reactor 2 configured to be supplied by at least one flow fraction M1p and comprising at least one flow outlet line M1h,- a treatment device 3 configured for biogas production, configured to be supplied by at least one flow fraction M1h and comprising at least two outlets, a liquid carbon dioxide CO2liq outlet line,a pressurizing and / or heating device 5 supplied by a liquid carbon dioxide CO2liq outlet line downstream of the treatment device 3 and comprising at least one supercritical carbon dioxide CO2sc outlet line,said supercritical carbon dioxide CO2s outlet line being configured to feed the hydrolysis reactor 2.,

[0019] According to one embodiment, the installation further comprises at least one storage device 4 comprising at least one inlet supplied by the liquid carbon dioxide CO2liq outlet line downstream of the treatment device 3 and comprising at least one liquid carbon dioxide CO2liq2 outlet supplying the pressurization and / or heating device 5, preferably, said installation further comprises at least one recirculation loop making it possible to recirculate at least a fraction of the carbon dioxide recovered downstream of the hydrolysis reactor 2 to the storage device 4.

[0020] According to one embodiment of the installation, the treatment device 3 comprises a hydrothermal gasification reactor 31 comprising at least one flow outlet line M4, installation in which the pressurization and / or heating device 5 comprises at least one heat exchanger making it possible to recover heat from the flow M4 to transfer it to the liquid carbon dioxide upstream of the hydrolysis reactor 2, said heat exchanger comprising at least one flow outlet line M4'' and one supercritical carbon dioxide outlet line.

[0021] According to a first embodiment of the installation, the treatment device 3 comprises: - a hydrothermal gasification reactor (31) comprising at least one flow outlet line M4, - a cooling and expansion device 6 supplied with at least a fraction of the flow M4, where appropriate of the flow M4'', and comprising a gas flow outlet M5 and a liquid flow outlet M7, - a separation device 7 supplied with at least a fraction of the flow M5 and comprising a carbon dioxide-enriched flow outlet line M6 and a carbon dioxide-depleted flow outlet line 71, said separation device 7 preferably being a membrane separation device or a solvent extraction device, - a liquefaction device 8 supplied with at least a fraction of the carbon dioxide-enriched flow M6 and comprising an aqueous flow outlet line 81 and a liquid carbon dioxide flow outlet line,said liquid carbon dioxide flow outlet line supplying the pressurizing and / or heating device 5 or where appropriate supplying the storage device 4.,

[0022] According to a second embodiment of the installation, the treatment device 3 comprises: - a hydrothermal gasification reactor 31 comprising at least one flow outlet line M4, - a cooling device 9 supplied by at least a fraction of the flow M4, where appropriate of the flow M4'', and comprising a gas flow outlet M8 and a liquid flow outlet M9, - an expansion device 10 supplied by at least a fraction of the flow M9 and comprising a liquid flow outlet line M10 and a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line supplying the storage device 4, said hydrothermal treatment device 3 preferably further comprising: - a separation device 11 supplied by at least a fraction of the flow M8 and comprising a carbon dioxide-enriched flow outlet line M12 and a carbon dioxide-depleted flow outlet line M11,- an expansion device 12 supplied by at least a fraction of the flow M12 and comprising a liquid carbon dioxide flow outlet line and a liquid flow outlet line M13, said liquid carbon dioxide flow outlet line supplying the storage device 4.,

[0023] According to another embodiment of the installation, the treatment device 3 comprises: - a digester 32 supplied by the flow line M1h and comprising a gas flow outlet M14, - a separation device 13 supplied by at least one fraction of flow M14 and comprising a carbon dioxide-enriched flow outlet line M16 and a carbon dioxide-depleted flow outlet line M15, - a liquefaction device 14 supplied by at least one fraction of flow M16 and comprising a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line supplying the pressurizing and / or heating device 5 or, where appropriate, supplying the storage device 4.

[0024] The invention makes it possible to facilitate the conversion and improve the yield of biogas production and digestion of organic matter.

[0025] The invention thus proposes a method for pre-treating biomass and complex waste that makes it possible to optimize both the treatment itself and energy expenditure while using the co-product of these energy conversions, which is CO2. Brief description of the figures

[0026] illustrates an installation for implementing the method according to one embodiment of the invention.

[0027] illustrates an installation for implementing the method according to one embodiment of the invention.

[0028] illustrates an installation for implementing the method according to one embodiment of the invention.

[0029] illustrates an installation for implementing the method according to one embodiment of the invention.

[0030] illustrates an installation for implementing the method according to one embodiment of the invention.

[0031] illustrates an installation for implementing the method according to one embodiment of the invention.

[0032] illustrates an installation for implementing the method according to one embodiment of the invention.

[0033] illustrates an installation for implementing the method according to one embodiment of the invention.

[0034] illustrates an installation for implementing the method according to one embodiment of the invention.

[0035] illustrates an installation for implementing the method according to one embodiment of the invention.

[0036] illustrates an installation for implementing the method according to one embodiment of the invention. Detailed description of the invention

[0037] The invention relates to a method for treating a mixture M1 comprising at least organic matter, said method comprising:a. pressurizing the mixture M1 to a pressure ranging from 1 to 300 bars, preferably from 20 to 100 bars, in order to obtain a mixture stream M1p,b. a step of hydrolysis of at least a fraction of the mixture M1p in the presence of supercritical carbon dioxide, in order to obtain a hydrolyzed mixture stream M1h,c. a treatment step allowing biogas production and carried out on at least a fraction of the hydrolyzed mixture stream M1h, said treatment step making it possible to obtain a liquid carbon dioxide CO2liq stream,d. a pressurizing and / or heating step carried out on at least a fraction of liquid carbon dioxide CO2liq downstream of treatment step c) in order to obtain all or part of the supercritical carbon dioxide used in step b).

[0038] For the purposes of the present invention, the expression "at least a fraction of a mixture or stream" has the same meaning as the expression "all or part of said mixture or stream". When referring to a part of said mixture or stream, this expression refers to a certain proportion of said mixture or stream. For example, for the purposes of this expression "each fraction of the mixture" or "each fraction of the stream" will have the same composition.

[0039] As used herein, the term "where appropriate" means "if applicable."

[0040] • M1 Mix

[0041] Mixture M1 is typically a biomass. The biomass can be pasty or liquid, and can be, in particular, sewage treatment plant sludge, food and agri-food waste. Preferably, it is sewage treatment plant sludge.

[0042] According to one embodiment, the mixture M1 comprises from 5 to 50% by weight of solid matter, preferably from 15 to 35% by weight of solid matter, relative to the total weight of the mixture M1.

[0043] According to one embodiment, the method of the invention comprises a grinding step and / or a thermal or biological hydrolysis step of the mixture M1, said hydrolysis step then preferably being carried out at a pressure ranging from 1 to 8 bars and at a temperature ranging from 70 to 165°C, in order to obtain a hydrolyzed mixture M1', at least a fraction of said hydrolyzed mixture M1' then being put under pressure in step a) to obtain the mixture stream M1p which will then be carried out in step b) of the method of the invention.

[0044] Grinding will then improve the specific surface area and thus allow better hydrolysis.

[0045] • Step a) of pressurization

[0046] The method according to the invention comprises a step of pressurizing the mixture M1 preferably to a pressure ranging from 1 to 300 bars, preferably from 20 to 100 bars, said mixture M1 possibly already being under pressure before step a).

[0047] A M1p mixing flow is then obtained.

[0048] • Step b) hydrolysis

[0049] The process according to the invention comprises a step of hydrolysis of at least a fraction of the mixture M1p in the presence of supercritical carbon dioxide.

[0050] Supercritical carbon dioxide is carbon dioxide at a temperature of at least 31.25°C and a pressure of at least 74 bar.

[0051] Supercritical carbon dioxide is a fluid state of carbon dioxide (CO2) obtained when it is maintained above its critical temperature and pressure, respectively 31.25°C and 74 bars. At these pressures and temperatures, the state of CO2 means that it still has a significant density: 0.47 g / cm 3 .

[0052] Supercritical CO2 has properties that are between those of a gaseous fluid and those of a liquid. Its properties can be adjusted by changing external parameters (temperature and / or pressure).

[0053] Thanks to its viscosity, its density and a high level of diffusion, supercritical CO2 will therefore be able to enter and dissolve in biological matrices and act on the bonds between organic matter and the water present in the matrix during the hydrolysis stage of the organic matter.

[0054] In particular, supercritical CO2 exhibits a significant quadrupole moment and, related to its microscopic solvent behavior, this molecule can participate in hydrogen bonding interactions and act as both a weak Lewis acid and base during the hydrolysis step of organic matter.

[0055] Typically, the hydrolysis step is carried out in one or more hydrolysis reactors.

[0056] In the hydrolysis step, preferably, supercritical carbon dioxide is continuously introduced into the hydrolysis device(s), preferably through an inlet separate from the mixing inlet M1p.

[0057] At the end of the hydrolysis, a stream of hydrolyzed mixture M1h is obtained. The mixture M1h will typically be at a temperature above the supercritical temperature of CO2 and at a pressure above the supercritical pressure of CO2.

[0058] Hydrolysis can be carried out with a residence time ranging from 5 minutes to 90 minutes.

[0059] The hydrolysis is preferably carried out at a temperature ranging from 40°C to 300°C and / or at a pressure ranging from 80 bars to 250 bars.

[0060] The ratio between the viscosity of the mixture M1 and the viscosity of the mixture M1h being preferably at least 5, preferably at least 10, more preferably at least 100.

[0061] The viscosity defined in the context of the present invention is a kinematic viscosity measured at the same temperature (20°C for example) using rheometers adapted to the viscosity to be measured (cylinder - cylinder, plane - plane) and measuring at the same shear (in s-1) the two viscosities, typically taking care to eliminate turbulence problems and to respect the rheological rules (for example spacing between cylinders depending on the granulometry).

[0062] According to one embodiment, a fraction of the carbon dioxide used during the hydrolysis is recovered downstream of the hydrolysis to be reintroduced directly at the hydrolysis inlet.

[0063] • Processing step c)

[0064] The method of the invention comprises a treatment step allowing the production of biogas and carried out on at least a fraction of the hydrolyzed mixture flow M1h.

[0065] This treatment step makes it possible to obtain at least one stream of liquid carbon dioxide CO2liq. This stream of carbon dioxide can be obtained by liquefying at least a fraction of a stream obtained during the treatment method according to the invention. Examples of liquefaction given for information purposes are described below. • Storage

[0066] According to one embodiment, the method of the invention further comprises a storage step. According to this embodiment, at least a fraction of the liquid carbon dioxide CO2liq resulting from treatment step c) is introduced into one or more storage devices, where the carbon dioxide will be stored. The storage device(s) may optionally comprise one or more cooling devices. These cooling devices can thus make it possible to liquefy the carbon dioxide.

[0067] Preferably, according to this embodiment, the carbon dioxide is stored in the storage device in a liquid form, typically at a temperature ranging from -56°C to 31°C and at a pressure ranging from 5 bar to 73 bar. For example, the carbon dioxide may be stored at -20°C and 20 bar.

[0068] The storage device(s) may also be supplied with at least a fraction of the carbon dioxide, preferably in liquid form, recovered downstream of the hydrolysis.

[0069] Within the scope of the present invention, one or more storage devices may be provided.

[0070] • Pressurization and / or heating step d)

[0071] The method of the invention comprises a pressurization and / or heating step implemented on at least a fraction of the liquid carbon dioxide downstream of treatment step c) in order to obtain all or part of the supercritical carbon dioxide used in step b).

[0072] Thus, this step d) allows the carbon dioxide to be brought into supercritical conditions.

[0073] According to one embodiment, at least a fraction of the liquid carbon dioxide from step c) is introduced into one or more storage devices, step d) of pressurizing and / or heating then being implemented downstream of the storage device(s).

[0074] Depending on the storage temperature and pressure, the carbon dioxide will then typically be heated and / or pressurized downstream of said storage device, in order to bring the carbon dioxide to supercritical conditions, before its use in the hydrolysis step b).

[0075] Step d) is typically implemented in a pressurizing and / or heating device 5.

[0076] Step d) may comprise one or more sub-steps. Thus, according to one embodiment, step d) comprises at least one heat exchange sub-step in which heat from the mixture stream treated in step c) is recovered and transferred to the liquid carbon dioxide upstream of the hydrolysis step and, where appropriate (i.e., when the method comprises a storage step in a storage device), downstream of the storage device. This heat exchange sub-step thus makes it possible to at least partially heat the carbon dioxide during step d) to bring it to supercritical conditions.

[0077] According to one embodiment of the invention, the method comprises at least one heat exchange making it possible to transfer heat from the flow of material treated during treatment step c) to the flow of liquid carbon dioxide upstream of hydrolysis step b) and, where appropriate, downstream of the storage step.

[0078] According to one embodiment of the invention, the method comprises two heat exchanges: - a heat exchange making it possible to transfer heat from the flow of material treated during treatment step c) to the flow of material M1h upstream of treatment step c), - a heat exchange making it possible to transfer heat from the flow of material treated during treatment step c) to the flow of liquid carbon dioxide upstream of hydrolysis step b) and where appropriate downstream of the storage step.

[0079] • Treatment step c): hydrothermal gasification (GH)

[0080] According to one embodiment, treatment step c) is a hydrothermal gasification step, preferably carried out at a temperature ranging from 350°C to 700°C, preferably from 400°C to 600°C, more preferably from 450°C to 550°C, and / or at a pressure ranging from 200 to 450 bars, preferably from 250 to 300 bars.

[0081] Hydrothermal gasification (GH) is a thermal depolymerization process used to convert organic matter present in a humid environment into a mixture comprising only small molecules under high to moderate temperature and pressure.

[0082] During GH, carbon and hydrogen in an organic material are converted thermochemically under near-critical or supercritical conditions. Some of it is converted into low-molar-mass compounds that are soluble in water.

[0083] Another part is converted into gas products such as carbon dioxide (CO2), methane (CH4), dihydrogen (H2), carbon monoxide (CO), light hydrocarbons such as ethane (C2H6) and propane (C3H8).

[0084] During the stay in the hydrothermal gasification reactor at temperatures below 400°C, the organic matter undergoes, among other reactions, a decomposition based on a very rapid homogeneous hydrolysis (a few seconds). In fact, an implementation in quasi-critical or supercritical conditions allows the use of the unique properties of supercritical water as a solvent, which allow solvation conditions and homogeneous reactions, leading to very high reaction kinetic rates. As a result, a much shorter residence time and a much higher heating rate than those of conventional hydrolysis are used, limiting or even avoiding the secondary condensation and polymerization reactions responsible for the formation of bio-oil and biochar.

[0085] When GH is operated at a temperature above 400°C, free radical decomposition of polymers (involving in particular decarboxylation, deamination by breaking CN bonds, and CC or CO cleavage reactions) is predominant, while endothermic steam reforming is the main reaction pathway to convert small molecules with 1 to 3 carbon atoms into carbon oxides and dihydrogen and nitrogen into ammonia.

[0086] Methane is also produced by methanation of CO and CO2, using dihydrogen.

[0087] Consequently, GH can be considered as a decomposition process transforming the organic residues present in the M1h stream into more easily biodegradable material and into dissolved ammonia in the liquid phase.

[0088] The treatment conditions (in particular temperature, pressure, and to a lesser extent residence time) of the GH can be adjusted to not only produce a gaseous fraction containing CH4, CO, CO2 and H2 (synthesis gas), but also to produce an aqueous effluent, containing mainly on one side easily digestible compounds, in particular carboxylic acids and on the other side ammonia in the form of ammonium salt of the carbonic acids produced.

[0089] Typically, in the context of the present invention, this GH step makes it possible to obtain a flow of mineral material M3 and a flow M4 comprising a mixture containing gas and liquid.

[0090] In the context of the present invention, the M3 flow will be referred to indifferently as the flow of inorganic matter or the flow of mineral matter.

[0091] The M3 mineral matter stream will typically include a proportion of mineral matter greater than the proportion of mineral matter in the M1h stream.

[0092] The material stream M4 will typically include a mass proportion of organic matter greater than the mass proportion of organic matter in the stream M1h.

[0093] Typically also, the M3 mineral matter stream will include a greater proportion of mineral matter than the proportion of mineral matter in the M4 stream.

[0094] Typically also, the M4 material stream will include a higher proportion of organic matter than the proportion of organic matter in the M3 stream.

[0095] The M4 stream will include a mixture of gas and liquid, this gas more specifically includes CO2.

[0096] Hydrothermal gasification is the name given to the entire treatment chain resulting on the one hand in the production of a gas by the transformation of organic matter and on the other hand in several liquid fractions containing more or less inorganic matter.

[0097] Typically, this hydrothermal gasification includes at least the pressurization and heating of the biomass, in particular at temperatures above 350°C and at pressures allowing vaporization of the medium to be avoided.

[0098] According to one embodiment, the hydrothermal gasification is carried out in a gasification reactor:- at a temperature ranging from 400°C to 600°C, preferably from 450°C to 550°C; and / or- at a pressure ranging from 200 to 450 bars, preferably from 250 to 300 bars.

[0099] Hydrothermal gasification can also include separation of the mineral fraction (salts) M3 and can use catalysts.

[0100] Among the mineral matter, we can cite salts including anions such as phosphates, sulfates, chlorides, carbonates and hydrocarbonates with counter ions for example sodium, magnesium, calcium, ammonium and metals.

[0101] Preferably, the (overall) residence time of the M1h stream in step c) of GH typically ranges from 1 min to 20 min, preferably from 2 min to 10 min, more preferably from 3 to 5 min.

[0102] According to one embodiment, the hydrothermal gasification step is carried out in a gasification reactor in the presence of at least one catalyst. Preferably, the catalyst is chosen from metals on activated carbon, for example of the ruthenium, nickel, palladium or platinum type.

[0103] The catalyst may be in the form of a bed of solid particles within the gasification reactor.

[0104] The hydrothermal gasification step will thus generally lead to a mixture comprising inorganic matter (salts) and organic matter.

[0105] In the context of the invention, typically, the GH step comprises a separation step making it possible to obtain on the one hand a flow M3 enriched in inorganic matter and on the other hand a flow M4 depleted in inorganic matter. The flow M4 will then generally be a flow of gas dissolved in a liquid effluent.

[0106] For the purposes of the present invention, in the context of a separation of a given flow X, the term "a flow enriched in inorganic matter" means a flow comprising a mass proportion of inorganic matter greater than the mass proportion of inorganic matter in the given flow X, these mass proportions being defined in proportion to the dry matter.

[0107] For the purposes of the present invention, in the context of a separation of a given flow X, the term "flow depleted in inorganic matter" means a flow comprising a mass proportion of inorganic matter lower than the mass proportion of inorganic matter in the given flow X, these mass proportions being defined in proportion to the dry matter.

[0108] According to one embodiment, at the outlet of the hydrothermal gasification, a carbon dioxide stream is obtained by a so-called "high pressure" separation or by a so-called "low pressure" separation implemented from at least a fraction of the M4 stream from the hydrothermal gasification reactor, where appropriate from the M4' or M4'' stream obtained after one or more heat exchanges of the M4 stream.

[0109] • So-called “low pressure” separation

[0110] According to one embodiment of the method of the invention, the hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- hydrothermal gasification carried out on at least a fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter,- a step of cooling and expanding at least a fraction of the stream M4 to a temperature ranging from 20 to 150°C, preferably from 50 to 100°C, and to a pressure ranging from 1 bar to 100 bars, making it possible to obtain on the one hand a gas stream M5 and on the other hand a liquid stream M7,- a step of separating at least a fraction of the gas stream M5 making it possible to obtain on the one hand a stream enriched in carbon dioxide M6 and on the other hand a stream depleted in carbon dioxide 71,- a step of liquefaction of at least a fraction of the M6 ​​flow,typically up to a temperature ranging from -56°C to 31°C and at a pressure ranging from 5 to 73 bars, making it possible to obtain a flow of liquid carbon dioxide on the one hand (flow called “flow enriched in CO2”) and a gaseous flow 81 (flow called “flow depleted in CO2”) on the other hand.,

[0111] According to the embodiment involving one or more storage devices, at least a fraction of said liquid carbon dioxide stream is introduced into at least one storage device.

[0112] Preferably, the liquefaction step comprises a cooling step and / or a compression step. It makes it possible to liquefy carbon dioxide.

[0113] • So-called “high pressure” separation

[0114] According to one embodiment of the method of the invention, the hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- a hydrothermal gasification carried out on at least a fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter,- a step of cooling at least a fraction of the stream M4 to a temperature ranging from 0 to 90°C, preferably from 10 to 70°C, preferably from 25 to 50°C, making it possible to obtain on the one hand a gas stream M8 and on the other hand a liquid stream M9 (stream comprising dissolved CO2), the liquid stream M9 being at a pressure ranging from 150 to 350 bars;- a step of expanding at least a fraction of the liquid flow M9, typically up to a pressure ranging from 35 bars to 100 bars, making it possible to obtain on the one hand a flow of liquid carbon dioxide (“flow enriched in CO2”) and on the other hand a liquid flow M10 (“flow depleted in CO2”);

[0115] According to the embodiment involving one or more storage devices, at least a fraction of said CO2-enriched stream is introduced into at least one storage device.

[0116] According to this so-called “high pressure” embodiment, carbon dioxide can also preferably be recovered in all or part of the M8 stream.

[0117] Thus, according to one embodiment, the method further comprises:- a separation step implemented on at least a fraction of the gas stream M8, making it possible to obtain on the one hand a stream enriched in carbon dioxide M12 and on the other hand a stream depleted in carbon dioxide M11,- an expansion step implemented on at least a fraction of the stream M12 up to a pressure ranging from 35 to 100 bars, making it possible to obtain on the one hand a stream of liquid carbon dioxide (“stream enriched in CO2”) and on the other hand a liquid stream M13 (“stream depleted in CO2”).

[0118] According to the embodiment involving one or more storage devices, at least a fraction of said CO2-enriched stream is introduced into at least one storage device.

[0119] • Heat exchanges

[0120] According to one embodiment, the treatment step c) is a hydrothermal gasification making it possible to obtain at least one stream M4 comprising gas and liquid and the method of the invention comprises a heat exchange X1 between at least a fraction of the stream M4 resulting from the hydrothermal gasification step and the stream of liquid carbon dioxide upstream of the hydrolysis and where appropriate downstream of the storage device, said heat exchange thus making it possible to at least partially heat the liquid carbon dioxide and making it possible to at least partially cool the stream M4. The stream thus cooled will be called stream M4''. This heat exchange X1 may correspond to step d) of the invention or to a sub-step of step d) of the invention.

[0121] According to this embodiment, at least a fraction of the M4'' stream can be separated according to a so-called "low pressure" separation or according to a so-called "high pressure" separation as defined in the present invention in order to obtain a stream of liquid carbon dioxide CO2liq.

[0122] According to one embodiment, the treatment step c) is a hydrothermal gasification comprising a preliminary step of heating the mixture flow M1h, said preliminary heating step comprising at least one sub-step of heat exchange X2 between the flow M4 resulting from the hydrothermal gasification step and the flow M1h, said heat exchange X2 thus making it possible to at least partially heat the mixture M1h and to at least partially cool the flow M4, in order to obtain a flow M4'.

[0123] According to this embodiment, at least a fraction of the M4' stream can be separated according to a so-called "low pressure" separation or according to a so-called "high pressure" separation as defined in the present invention in order to obtain a stream of liquid carbon dioxide CO2liq.

[0124] According to this embodiment, the method preferably further comprises a heat exchange between the flow M4' and the flow of liquid carbon dioxide upstream of the hydrolysis and where appropriate downstream of the storage device, said heat exchange X1' thus making it possible to at least partially heat the liquid carbon dioxide and making it possible to at least partially cool the flow M4' in order to obtain a flow M4''. This heat exchange X1' may correspond to step d) of the invention or to a sub-step of step d) of the invention.

[0125] According to this embodiment, at least a fraction of the M4'' stream can be separated according to a so-called "low pressure" separation or according to a so-called "high pressure" separation as defined in the present invention in order to obtain a stream of liquid carbon dioxide CO2liq.

[0126] According to one embodiment of the invention, the method comprises two heat exchanges: - a heat exchange X2 making it possible to transfer heat from the flow of material treated during treatment step c) to the flow of material M1h upstream of treatment step c), - a heat exchange X1, X1' making it possible to transfer heat from the flow of material treated during treatment step c) to the flow of liquid carbon dioxide upstream of hydrolysis step b) and where appropriate downstream of the storage step.

[0127] • Processing step c): digestion

[0128] According to one embodiment, the treatment step c) is a digestion. Preferably, according to this embodiment, the treatment step c) comprises:- a digestion carried out on at least a fraction of the mixture flow M1h, making it possible to obtain a gas flow M14,- a separation step carried out on at least a fraction of the gas flow M14 making it possible to obtain a carbon dioxide-enriched flow M16 and a carbon dioxide-depleted flow M15,- a liquefaction step carried out on at least a fraction of the carbon dioxide-enriched flow M16 typically up to a temperature ranging from -56°C to +31°C, making it possible to obtain a liquid carbon dioxide flow, said liquefaction step preferably being carried out by cooling and / or by compression.

[0129] A flow of digested material M17 is obtained downstream of digestion.

[0130] According to the embodiment involving one or more storage devices, at least a fraction of said liquid carbon dioxide stream is introduced into at least one storage device.

[0131] The present invention also relates to an installation as such and an installation for implementing the method of the invention.

[0132] The installation according to the invention comprises:- at least one pressurizing pump 1, comprising a flow outlet line M1p,- at least one hydrolysis reactor 2 supplied by at least one fraction of flow M1p and comprising a supercritical carbon dioxide CO2sc supply line, and comprising at least one flow outlet line M1h,- a treatment device 3 supplied by at least one fraction of flow M1h and comprising at least one liquid carbon dioxide CO2liq1 outlet line,- a pressurizing and / or heating device 5 supplied by a liquid carbon dioxide CO2liq outlet line downstream of the treatment device 3 and comprising at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc outlet line supplying the hydrolysis reactor 2.

[0133] According to one embodiment, the installation according to the invention comprises at least one storage device 4 comprising at least one inlet supplied by the liquid carbon dioxide CO2liq outlet line downstream of the treatment device 3 and comprising at least one liquid carbon dioxide CO2liq outlet making it possible to supply the pressurization and / or heating device 5.

[0134] According to an embodiment not shown in the Figures, the installation according to the invention does not include a storage device.

[0135] According to an embodiment not shown in the Figures, the installation further comprises at least one recirculation loop making it possible to recirculate at least a fraction of the carbon dioxide recovered downstream of the hydrolysis reactor 2 to the storage device 4 or to the pressurization and / or heating device 5 when the installation does not comprise a storage device.

[0136] Said recirculation loop may optionally comprise a cooling and expansion device and / or the storage device 4 may optionally comprise a cooling and expansion device not shown in the Figures. This makes it possible to liquefy the carbon dioxide, possibly still in gaseous form, for storage or use during hydrolysis.

[0137] According to one embodiment, the pressurizing and / or heating device 5 comprises at least one heat exchanger, said heat exchanger making it possible to recover heat from the flow of material treated in the treatment device and to transfer it to the carbon dioxide upstream of the hydrolysis step. This embodiment of the installation makes it possible to implement the heat exchange X1 (or the heat exchange X1' when the installation comprises a heat exchanger for implementing the heat exchange X2).

[0138] According to one embodiment, the treatment device 3 further comprises a heat exchanger for transferring heat from the flow of material treated during the treatment step c) to the flow of material M1h upstream of the treatment step c). This embodiment of the installation makes it possible to implement the heat exchange X2.

[0139] Illustrates an embodiment of the invention, where the installation comprises: - a mixture supply line M1, - a pressurization pump 1, supplied by the mixture supply line M1 comprising a flow outlet line M1p, - a hydrolysis reactor 2 supplied by at least a fraction of flow M1p and by a supercritical carbon dioxide CO2sc supply line, and comprising at least one flow outlet line M1h and one carbon dioxide CO2 outlet line, - a treatment device 3 supplied by at least a fraction of flow M1h and comprising at least one liquid carbon dioxide CO2liq1 outlet line, a storage device 4 supplied by at least a fraction of the liquid carbon dioxide CO2liq1 outlet line downstream of the treatment device 3 and comprising at least one liquid carbon dioxide CO2liq2 outlet,- a pressurizing and / or heating device 5 supplied by the liquid carbon dioxide CO2liq2 outlet line downstream of the storage device 4 and comprising at least one supercritical carbon dioxide CO2sc outlet line, said supercritical carbon dioxide CO2sc outlet line supplying the hydrolysis reactor 2,- a carbon dioxide recirculation loop between the carbon dioxide CO2 outlet line downstream of the hydrolysis reactor and the storage device 4.,

[0140] According to one embodiment, the treatment device 3 comprises a hydrothermal gasification reactor 31.

[0141] The installation according to the invention comprising a hydrothermal gasification reactor 31 can be adapted to implement a so-called low pressure separation.

[0142] According to this embodiment, preferably, the treatment device 3 comprises: - a hydrothermal gasification reactor 31 comprising at least one flow outlet line M4 and at least one outlet line M3, - a cooling and expansion device 6 supplied with at least a fraction of the flow M4, if applicable of the flow M4', and comprising a gas flow outlet M5 and a liquid flow outlet M7, - a separation device 7 supplied with at least a fraction of the flow M5 and comprising a carbon dioxide-enriched flow outlet line M6 and a carbon dioxide-depleted flow outlet line 71, said separation device 7 preferably being a membrane separation device or a solvent extraction device, - a liquefaction device 8 supplied with at least a fraction of the carbon dioxide-enriched flow M6 and comprising an aqueous flow outlet line 81 and a liquid carbon dioxide flow outlet line,said liquid carbon dioxide flow outlet line supplying the storage device 4.,

[0143] The liquefaction device 8 may be a cooling device and / or a compression device.

[0144] Illustrates an embodiment where the treatment step c) is a hydrothermal gasification step where the carbon dioxide is recovered by a “low pressure” separation. As illustrated in , the treatment device 3 comprises: - a hydrothermal gasification reactor 31 comprising at least one flow outlet line M4, - a cooling and expansion device 6 supplied with at least a fraction of the flow M4, and comprising a gas flow outlet M5 and a liquid flow outlet M7, - a separation device 7 supplied with at least a fraction of the flow M5 and comprising a carbon dioxide-enriched flow outlet line M6 and a carbon dioxide-depleted flow outlet line 71, said separation device 7 preferably being a membrane separation device or a solvent extraction device,- a liquefaction device 8 supplied with at least a fraction of the carbon dioxide-enriched flow M6 and comprising an aqueous flow outlet line 81 and a liquid carbon dioxide flow outlet line CO2liq1, said liquid carbon dioxide flow outlet line supplying the storage device 4.,

[0145] This illustrates an embodiment where the method comprises a heat exchange between the flow M4 leaving the hydrothermal gasification reactor and the pressurizing and / or heating device 5, which makes it possible on the one hand to cool the flow M4 (in order to obtain a flow M4'') and on the other hand to heat the liquid carbon dioxide CO2liq2 (making it possible to obtain supercritical carbon dioxide CO2sc). This illustrates an embodiment of the installation for implementing the heat exchange X1 defined in the invention.

[0146] The installation according to the invention comprising a hydrothermal gasification reactor 31 can be adapted to implement a so-called high pressure separation.

[0147] According to this embodiment, preferably, the treatment device 3 comprises: - a hydrothermal gasification reactor 31 comprising at least one flow outlet line M4, - a cooling device 9 supplied by at least a fraction of the flow M4, where appropriate of the flow M4'', and comprising a gas flow outlet M8 and a liquid flow outlet M9, - an expansion device 10 supplied by at least a fraction of the flow M9 and comprising a gas flow outlet line M10 and a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line supplying the storage device 4.

[0148] Said expansion device 10 may optionally further comprise a cooling device in order to obtain carbon dioxide in liquid form.

[0149] Preferably, according to this embodiment, the treatment device 3 further comprises: - a separation device 11 supplied with at least a fraction of the flow M8 and comprising a carbon dioxide-enriched flow outlet line M12 and a carbon dioxide-depleted flow outlet line M11, - an expansion device 12 supplied with at least a fraction of the flow M12 and comprising a liquid carbon dioxide flow outlet line and an aqueous flow outlet line M13, said liquid carbon dioxide flow outlet line CO2liq1' supplying the storage device 4.

[0150] Said expansion device 12 may optionally further comprise a cooling device in order to obtain carbon dioxide in liquid form.

[0151] Illustrates an embodiment where the treatment step c) is a hydrothermal gasification step where the carbon dioxide is recovered by a “high pressure” separation. As illustrated in , the treatment device 3 comprises: - a hydrothermal gasification reactor 31 comprising at least one flow outlet line M4, - a cooling device 9 supplied by at least a fraction of the flow M4, and comprising a gas flow outlet M8 and a liquid flow outlet M9, - an expansion device 10 supplied by at least a fraction of the flow M9 and comprising a gas flow outlet line M10 and a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line supplying the storage device 4.

[0152] The differs from the in that the method comprises a heat exchange between the flow M4 leaving the hydrothermal gasification reactor and the liquid carbon dioxide CO2liq2 for example in the pressurizing and / or heating device 5, which makes it possible on the one hand to cool the flow M4 (in order to obtain a flow called M4'') and on the other hand to heat the liquid carbon dioxide CO2liq2 (making it possible to obtain supercritical carbon dioxide CO2sc). This illustrates an embodiment of the installation for implementing the heat exchange X1 defined in the invention.

[0153] The difference from the in that the treatment device 3 further comprises: - a separation device 11 supplied with at least a fraction of the flow M8 and comprising a carbon dioxide-enriched flow outlet line M12 and a carbon dioxide-depleted flow outlet line M11, - an expansion device 12 supplied with at least a fraction of the flow M12 and comprising a liquid carbon dioxide flow outlet line and an aqueous flow outlet line M13, said liquid carbon dioxide flow outlet line CO2liq1' supplying the storage device 4.

[0154] Illustrates an embodiment where the storage device 4 comprises an inlet for the CO2liq1 flow and an inlet for the CO2liq1' flow. According to an embodiment not shown, the CO2liq1 and CO2liq1' flow lines can be combined upstream of the storage device 4.

[0155] This illustrates an embodiment of the process with low pressure separation where the process comprises a heat exchange in a heat exchanger 312 supplied by at least a fraction of the flow M4 leaving a gasification reactor 311, making it possible on the one hand to cool the flow M4 (obtaining a flow M4') and on the other hand to at least partially heat the mixture M1h upstream of the gasification reactor 311 (obtaining a flow M2). This illustrates an embodiment of the installation for implementing the heat exchange X2 defined in the invention.

[0156] This illustrates an embodiment of the method with high pressure separation where the method comprises a heat exchange in a heat exchanger 312 supplied with at least a fraction of the flow M4 leaving a gasification reactor 311, making it possible on the one hand to cool the flow M4 (in order to obtain a flow M4') and on the other hand to at least partially heat the mixture M1h upstream of the gasification reactor 311 (in order to obtain a flow M2). This illustrates an embodiment of the installation for implementing the heat exchange X1 defined in the invention.

[0157] Illustrates an embodiment of the method implementing a GH step with low pressure separation and illustrates an embodiment of the method implementing a GH step with high pressure separation.

[0158] According to an embodiment illustrated in the set, the method comprises two heat exchanges: - a first heat exchange X2 in a heat exchanger 312 supplied with at least a fraction of the flow M4 leaving a gasification reactor 311, making it possible on the one hand to cool the flow M4 (obtaining a flow M4') and on the other hand to at least partially heat the mixture M1h upstream of the gasification reactor 311 (obtaining a flow M2), - a second heat exchange X1' between the flow M4' downstream of the heat exchanger 312 and the liquid carbon dioxide CO2liq2 for example in the pressurizing and / or heating device 5, which makes it possible on the one hand to cool the flow M4' (in order to obtain a flow M4'') and on the other hand to heat the liquid carbon dioxide CO2liq2 (making it possible to obtain supercritical carbon dioxide CO2sc).

[0159] According to one embodiment, the treatment device 3 comprises a digester 32. According to this embodiment, preferably, the treatment device 3 comprises: - a digester 32 supplied by the flow line M1h and comprising a gas flow outlet M14, - a separation device 13 supplied by at least one fraction of flow M14 and comprising a carbon dioxide-enriched flow outlet line M16 and a carbon dioxide-depleted flow outlet line M15, - a liquefaction device 14 supplied by at least one fraction of flow M16 and comprising a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line, said carbon dioxide flow outlet line supplying a storage device 4 when such a storage device is present or supplying the pressurizing and / or heating device 5 when the installation does not comprise a storage device.

[0160] The liquefaction device 14 may be a cooling device and / or a compression device.

[0161] Illustrates an embodiment where the treatment step c) is a digestion step. According to an embodiment illustrated in 1, the treatment device 3 comprises: - a digester 32 supplied by the flow line M1h and comprising a gas flow outlet M14, - a separation device 13 supplied by at least one fraction of flow M14 and comprising a carbon dioxide-enriched flow outlet line M16 and a carbon dioxide-depleted flow outlet line M15, - a liquefaction device 14 supplied by at least one fraction of flow M16 and comprising a liquid carbon dioxide CO2liq1 flow outlet line, said carbon dioxide flow outlet line supplying a storage device 4 when such a storage device is present or supplying the pressurizing and / or heating device 5 when the installation does not include a storage device.

[0162] The flow of digested material is illustrated by flow M17 in the, at the outlet of digester 32.

Claims

A method for treating a mixture M1 comprising at least organic matter, said method comprising:a. pressurizing the mixture M1 to a pressure ranging from 1 to 100 bars, in order to obtain a mixture stream M1p,b. a step of hydrolysis of at least a fraction of the mixture M1p in the presence of supercritical carbon dioxide, in order to obtain a hydrolyzed mixture stream M1h,c. a treatment step allowing biogas production and carried out on at least a fraction of the hydrolyzed mixture stream M1h, said treatment step making it possible to obtain a liquid carbon dioxide stream CO2liq1,d. a pressurizing and / or heating step carried out on at least a fraction of the liquid carbon dioxide CO2liq1 downstream of treatment step c) in order to obtain all or part of the supercritical carbon dioxide used in step b). Treatment method according to claim 1, in which at least a fraction of the liquid carbon dioxide from step c) is introduced into one or more storage devices, step d) of pressurizing and / or heating then being implemented downstream of the storage device(s). Treatment method according to claim 1 or 2, in which at least a fraction of the carbon dioxide used during the hydrolysis: is recovered downstream of the hydrolysis to be reused during step d) (i) of pressurization and / or heating, where appropriate after storage in one or more storage devices; and / or (ii) is recovered downstream of the hydrolysis to be reintroduced directly at the hydrolysis inlet. Treatment method according to any one of claims 1 to 3, wherein the treatment of step c) is a hydrothermal gasification, preferably carried out at a temperature ranging from 350°C to 700°C, preferably from 400°C to 600°C, more preferably from 450°C to 550°C, and / or at a pressure ranging from 200 to 450 bars, preferably from 250 to 300 bars. Treatment method according to claim 4, wherein the hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- hydrothermal gasification carried out on at least a fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter,- a step of cooling and expanding at least a fraction of the stream M4 to a temperature ranging from 30 to 150°C, preferably from 50 to 100°C, and to a pressure ranging from 1 bar to 100 bars, making it possible to obtain on the one hand a gas stream M5 and on the other hand a liquid stream M7,- a step of separating at least a fraction of the gas stream M5 making it possible to obtain on the one hand a stream enriched in carbon dioxide M6 and on the other hand a stream depleted in carbon dioxide (71),- a step of liquefaction of at least a fraction of the M6 flow,making it possible to obtain the flow of liquid carbon dioxide CO2liq1 on the one hand and a gaseous flow (81) on the other hand, at least a fraction of said flow of liquid carbon dioxide CO2liq1 is used during step d) of pressurization and / or heating, where appropriate after storage in one or more storage devices., Treatment method according to claim 4, wherein the hydrothermal gasification makes it possible to obtain a stream M4 comprising a mixture containing gas and liquid, said hydrothermal gasification step comprising:- hydrothermal gasification carried out on at least a fraction of the mixture stream M1h, making it possible to obtain a stream M4 and optionally a stream M3 comprising mineral matter,- a step of cooling at least a fraction of the stream M4 to a temperature ranging from 0 to 90°C, preferably from 10 to 70°C, preferably from 25 to 50°C, making it possible to obtain on the one hand a gas stream M8 and on the other hand a liquid stream M9, the liquid stream M9 being at a pressure ranging from 150 to 350 bars,- a step of expanding at least a fraction of the liquid flow M9 to a pressure ranging from 35 bars to 100 bars making it possible to obtain on the one hand a flow enriched in liquid carbon dioxide CO2liq1 and on the other hand a liquid flow M10 depleted in carbon dioxide, at least a fraction of said flow of liquid carbon dioxide CO2liq1 is implemented during step d) of pressurizing and / or heating, where appropriate after storage in one or more storage devices, preferably, said method further comprising: - a separation step implemented on at least a fraction of the gaseous flow M8, making it possible to obtain on the one hand a flow enriched in carbon dioxide M12 and on the other hand a flow depleted in carbon dioxide M11, - an expansion step implemented on at least a fraction of the flow M12 to a pressure ranging from 35 to 100 bars,making it possible to obtain on the one hand a flow enriched in liquid carbon dioxide CO2liq1' and on the other hand a liquid flow M13 depleted in liquid carbon dioxide, at least a fraction of said flow of liquid carbon dioxide CO2liq1' is used during step d) of pressurization and / or heating, where appropriate after storage in one or more storage devices., Treatment method according to any one of claims 4 to 6, in which step d) comprises at least one step of heat exchange between at least a fraction of the M4 flow from the hydrothermal gasification step and the liquid carbon dioxide flow upstream of the hydrolysis and where appropriate downstream of the storage device, said heat exchange thus making it possible to at least partially heat the liquid carbon dioxide and making it possible to at least partially cool the M4 flow. Treatment method according to any one of claims 4 to 6, wherein the hydrothermal gasification step comprises a preliminary step of heating the mixture stream M1h, said preliminary heating step comprising at least one sub-step of heat exchange between at least a fraction of the stream M4 from the hydrothermal gasification step and the stream M1h, said heat exchange thus making it possible to at least partially heat the mixture M1h and to at least partially cool the stream M4, in order to obtain a stream M4', method further preferably comprising a heat exchange between the stream M4' and the stream of liquid carbon dioxide upstream of the hydrolysis and where appropriate downstream of the storage device, said heat exchange thus making it possible to at least partially heat the liquid carbon dioxide and to at least partially cool the stream M4' in order to obtain a stream M4''. Treatment method according to any one of claims 1 to 3, in which the treatment step c) is a digestion, said treatment comprising:- a digestion carried out on at least a fraction of the mixture flow M1h, making it possible to obtain a gas flow M14,- a separation step carried out on at least a fraction of the gas flow M14 making it possible to obtain a carbon dioxide-enriched flow M16 and a carbon dioxide-depleted flow M15,- a liquefaction step carried out on at least a fraction of the carbon dioxide-enriched flow M16, making it possible to obtain a liquid carbon dioxide flow. Installation for implementing a treatment method according to any one of claims 1 to 9, said installation comprising:- at least one pressurizing pump (1), comprising a flow outlet line M1p,- at least one hydrolysis reactor (2) configured to be supplied by at least one flow fraction M1p and comprising at least one flow outlet line M1h,- a treatment device (3) configured for biogas production, configured to be supplied by at least one flow fraction M1h and comprising at least two outlets, a liquid carbon dioxide CO2liq outlet line,- a pressurizing and / or heating device (5) supplied by a liquid carbon dioxide CO2liq outlet line downstream of the treatment device (3) and comprising at least one supercritical carbon dioxide CO2sc outlet line,said supercritical carbon dioxide CO2s outlet line being configured to feed the hydrolysis reactor (2)., Installation according to the preceding claim, further comprising at least one storage device (4) comprising at least one inlet supplied by the liquid carbon dioxide CO2liq outlet line downstream of the treatment device (3) and comprising at least one liquid carbon dioxide CO2liq2 outlet supplying the pressurization and / or heating device (5), preferably, said installation further comprises at least one recirculation loop making it possible to recirculate at least a fraction of the carbon dioxide recovered downstream of the hydrolysis reactor (2) to the storage device (4). Installation according to claim 10 or 11, in which the treatment device (3) comprises a hydrothermal gasification reactor (31) comprising at least one flow outlet line M4, installation in which the pressurization and / or heating device (5) comprises at least one heat exchanger making it possible to recover heat from the flow M4 to transfer it to the liquid carbon dioxide upstream of the hydrolysis reactor (2), said heat exchanger comprising at least one flow outlet line M4'' and one supercritical carbon dioxide outlet line. Installation according to any one of claims 10 to 12, in which the treatment device (3) comprises: - a hydrothermal gasification reactor (31) comprising at least one flow outlet line M4, - a cooling and expansion device (6) supplied with at least a fraction of the flow M4, where appropriate of the flow M4'', and comprising a gas flow outlet M5 and a liquid flow outlet M7, - a separation device (7) supplied with at least a fraction of the flow M5 and comprising a carbon dioxide-enriched flow outlet line M6 and a carbon dioxide-depleted flow outlet line (71), said separation device (7) preferably being a membrane separation device or a solvent extraction device,- a liquefaction device (8) supplied with at least a fraction of the carbon dioxide-enriched flow M6 and comprising an aqueous flow outlet line (81) and a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line supplying the pressurizing and / or heating device (5) or, where appropriate, supplying the storage device (4)., Installation according to any one of claims 10 to 12, in which the treatment device (3) comprises: - a hydrothermal gasification reactor (31) comprising at least one flow outlet line M4, - a cooling device (9) supplied by at least a fraction of the flow M4, where appropriate of the flow M4'', and comprising a gas flow outlet M8 and a liquid flow outlet M9, - an expansion device (10) supplied by at least a fraction of the flow M9 and comprising a liquid flow outlet line M10 and a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line supplying the storage device (4),said hydrothermal treatment device (3) preferably further comprising:- a separation device (11) supplied with at least a fraction of the flow M8 and comprising a carbon dioxide-enriched flow outlet line M12 and a carbon dioxide-depleted flow outlet line M11,- an expansion device (12) supplied with at least a fraction of the flow M12 and comprising a liquid carbon dioxide flow outlet line and a liquid flow outlet line M13, said liquid carbon dioxide flow outlet line supplying the storage device (4)., Installation according to claim 10 or 11, in which the treatment device (3) comprises: - a digester (32) supplied by the flow line M1h and comprising a gas flow outlet M14, - a separation device (13) supplied by at least one fraction of flow M14 and comprising a carbon dioxide-enriched flow outlet line M16 and a carbon dioxide-depleted flow outlet line M15, - a liquefaction device (14) supplied by at least one fraction of flow M16 and comprising a liquid carbon dioxide flow outlet line, said liquid carbon dioxide flow outlet line supplying the pressurizing and / or heating device (5) or, where appropriate, supplying the storage device (4).

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