Process for the recovery of organic waste

Abstract

The present invention relates to a biomimetic process for the valorization of organic waste by methanization and purification of the liquid digestate and CO2 by algae cultivation. Figure for abstract: N / A

Description

Title of the invention: Process for the recovery of organic waste Technical field

[0001] The present invention relates to a biomimetic process for the recovery of organic waste by methanization and purification of liquid digestate and CO2 by micro-algae culture.

[0002] State of the art

[0003] Organic waste is an important resource that can be used in various ways, including biomethanization. Biomethanization is a process of transforming organic waste into biogas, a mixture of methane and carbon dioxide. Biogas can be used as a renewable energy source to produce electricity, heat, or fuel.

[0004] However, biogas produced by biomethanization is often contaminated by impurities, including sulfur compounds, heavy metals and volatile organic compounds. These impurities can impair the performance of gas turbines and engines running on biogas.

[0005] Furthermore, biomethanization is often limited to organic plant waste because processed products are more likely to cause contamination and generate impurities, such as sulfur compounds and heavy metals.

[0006] Finally, the liquid part of the digestate is spread on fields, which can cause problems of pollution of groundwater, bodies of water and watercourses by nitrates. However, liquid digestate contains nutrients, such as nitrogen and phosphorus, which can be recovered.

[0007] There is therefore a need for a method solving the above-mentioned problems.

[0008] Description of the invention

[0009] The present invention proposes a method which makes it possible to recover organic waste of all kinds (hereinafter referred to as “organic waste”), to generate purified biogas and to directly exploit the CO2 and the liquid part of the digestate to develop a culture medium for cultivating microalgae in photobioreactors.

[0010] The advantages of the method of the present invention are as follows: - Recovery of organic waste, particularly including meat products; - Production of purified biogas, which allows the injection of biomethane with a purity of at least 97.5% into gas networks and improves the efficiency of gas turbines and engines running on biogas; - Valorization of the liquid part of the digestate, which helps to reduce the environmental impact environmental aspects of biomethanization; - Production of microalgae, which can be used to produce biofuels, biostimulants, food products and biomaterials.

[0011] In addition to the advantages mentioned above, the method of the present invention can also make it possible to recover the solid part of the digestate by making compost.

[0012] Indeed, the solid part of the digestate is a nutrient-rich amendment that can be used to improve soil quality.

[0013] In other words, this invention makes it possible to recover organic waste without producing residues because it makes it possible to transform all the products resulting from the degradation of this organic waste. It is intended to increase the energy autonomy of territories by producing biomethane, to reduce the quantity of waste, to improve the quality, yield and resistance to water stress of crops while contributing to the regeneration of soils thanks to the use of biofertilizers and natural biostimulants produced at the end of the process.

[0014] The subject of the present invention is a method for recovering organic waste comprising the steps of: a. Pretreatment of organic waste; b. Introduction of organic waste into at least one methanizer and production of biogas and digestate by said at least one methanizer; c. Separation and purification of biogas to separate CH4 and CO2; d. Separation of the digestate produced in step b) into liquid and solid digestate; e. Cultivation of at least one strain of microalgae by introducing the purified CO2 in step c) and the liquid digestate produced in step d) into a photobioreactor comprising said at least one strain of microalgae.

[0015] By "organic waste" (also called "biowaste") is meant waste of plant or animal origin that can be decomposed by microorganisms. This includes food waste (fruit and vegetable peelings, leftover meals, stale bread, etc.), garden waste (dead leaves, grass cuttings, hedge trimmings, etc.), wood waste (branches, shavings, sawdust, etc.) and livestock waste (manure, slurry, etc.).

[0016] According to one embodiment, the organic waste used in the method according to the present invention is of category SPAN C3. SPAN C3 is a category of organic waste that does not present high health risks. It comes from the kitchen and the table, such as leftover meals, expired food products, fruit and vegetable peelings, coffee grounds and coffee filters, egg shells, bones, fats, etc.

[0017] SPAN C3s are classified according to the health risk they represent, from Cl to C3, Cl being the highest risk and C3 the lowest risk. SPAN C3s are therefore those who present the lowest health risk.

[0018] To be classified as SPAN C3, organic waste must meet the following criteria: - It must not contain animal carcasses, blood or blood products, fecal matter, unprocessed material of animal origin, or decomposing products of animal origin. - It must not have been in contact with decomposing animal products. - It must be collected and transported in such a way as to avoid health risks.

[0019] Organic waste of category SPAN C3 can be selected from the group comprising leftover meals, expired food products, fruit and vegetable peelings, coffee grounds and coffee filters, egg shells, bones, fats, bread, pasta, rice, vegetables, fruits, dairy products, animal products, and mixtures thereof.

[0020] Although the method according to the invention makes it possible to treat all types of waste, the use of organic waste of category SPAN C3 further reduces the risk of contamination and / or the risk of generating impurities, such as sulphur compounds and heavy metals.

[0021] Step a) of the process according to the invention consists of pretreating the organic waste before introducing it into the methanizer. The inventors have discovered that this step is essential for improving the quality of the biogas produced and for facilitating the recovery of all types of organic waste, including those containing cam products or having a high or moderate health risk (Cl or C2).

[0022] The objectives of pre-processing are as follows: - Reduce particle size: This increases the contact surface between organic waste and methanogenic bacteria, which improves the rate of biogas production. - Eliminate contaminants: This helps reduce the production of impurities in the biogas, which can harm its use. - Homogenize the material: This allows for a uniform distribution of organic waste in the methanizer, which is important for homogeneous fermentation.

[0023] According to one embodiment, step a) of pretreatment of the organic waste comprises a step of grinding and / or homogenization and / or heating and / or cooling of the organic waste, preferably a grinding step, followed by a homogenization step, followed by a heating step, followed by a cooling step.

[0024] According to one embodiment, said step of grinding said organic waste makes it possible to obtain a material having an average particle size of between 2.5 and 10 mm, preferably between 3 and 7 mm, more preferably between 4 and 6 mm, even more preferably 5 mm.

[0025] Preferably, said grinding step is carried out in a jaw crusher, preferably with steel jaws.

[0026] According to one embodiment, said grinding step is followed by a homogenization step where the ground material is mixed in order to obtain a homogenized material.

[0027] According to one embodiment, said step of heating the organic waste comprises heating the organic waste to a temperature of between 50 and 90°C, preferably between 60°C and 80°C, more preferably between 65 and 75°C, even more preferably 70°C, for a duration of between 30 min and 2 h, preferably 45 min and 1 h 30, more preferably for 1 h.

[0028] According to one embodiment, said heating step is carried out in at least two tanks in series, heated one after the other by a coil filled with heated water, thus saving energy.

[0029] According to one embodiment, said step of cooling the organic waste comprises cooling the organic waste to a temperature suitable for methanization and / or between 30 and 45°C, preferably between 35 and 40°C, more preferably between 37°C and 37.5°C, even more preferably 38°C.

[0030] When the temperature of the organic waste reaches the required temperature, it is transferred to the methanizer(s), preferably by pumping.

[0031] According to one embodiment, said cooling step is carried out passively (e.g. using the ambient temperature of the room) or actively (e.g. using a cooling unit).

[0032] According to one embodiment, the homogenization step followed by a heating step is carried out in a first tank then the cooling step is carried out in a second tank.

[0033] Step b) consists of introducing the pre-treated organic waste into a methanizer and producing biogas and digestate. The methanizer is a sealed biological reactor in which the organic waste is fermented by methanogenic bacteria. These anaerobic bacteria transform the organic matter into biogas, a mixture of methane and carbon dioxide, and into digestate.

[0034] The important parameters to be controlled in step b) are as follows: - Temperature: Temperature is an important parameter to control because it affects the fermentation rate and biogas production. The optimal fermentation temperature is 37°C. However, fermentation can occur at lower temperatures, but the biogas production rate will be slower. - pH: pH is an important parameter to control because it affects the activity of methanogenic bacteria. The optimal pH for fermentation is 6.5 to 7.5. However, fermentation can occur at higher or lower pHs, but biogas production will be less efficient. - C / N ratio: The C / N ratio is the ratio between the amount of carbon and the amount of nitrogen in organic waste. The optimal C / N ratio is 25 to 30. If the C / N ratio is too high, biogas production will be reduced. - Water availability: Water availability is an important parameter to control because it affects nutrient solubility and fermentation rate. Organic waste must be sufficiently moist to allow fermentation. However, excessive moisture can inhibit fermentation. - Absence of oxygen: The absence of oxygen is an important parameter to control because anaerobic fermentation is necessary to produce biogas. Anaerobic fermentation occurs in the absence of oxygen.

[0035] The biomethanization according to the invention can be carried out in any known type of methanizer, for example a fixed-bed methanizer, a fluidized-bed methanizer or a heap digester methanizer.

[0036] According to one embodiment, step b) is carried out in at least two methanizers, preferably installed in parallel. The parallel installation makes it possible to facilitate maintenance as well as to compensate for seasonal variations in the quantity of waste.

[0037] The main effect of methanization is to produce biogas consisting of approximately 60% CH4 methane and 40% carbon dioxide CO2.

[0038] Step c) consists of purifying the biogas produced by the methanizer. This step is necessary to remove impurities, such as water, sulfur compounds and heavy metals.

[0039] Impurities can impair the use of biogas. Water can corrode equipment and reduce the lifespan of biogas storage systems. Sulfur compounds can corrode equipment and produce unpleasant odors. Heavy metals can be toxic to the environment.

[0040] There are many techniques for purifying biogas, the main ones being:

[0041] Desulfurization: This technique allows the removal of sulfur compounds from biogas.

[0042] Water removal: This technique allows the removal of water from biogas.

[0043] Dehydration: This technique allows water and volatile impurities to be eliminated from biogas.

[0044] CO2 separation: This technique allows carbon dioxide to be separated from biogas.

[0045] According to one embodiment of the invention, step c) is carried out by vacuum pressure swing adsorption (VPSA), preferably with an adsorbent being a molecular sieve.

[0046] Vacuum pressure swing adsorption (VPSA) separation is a biogas purification technique that uses an adsorbent, such as activated carbon, to absorb carbon dioxide from the biogas. The biogas is first compressed to a high pressure and then introduced into an adsorber filled with activated carbon. The carbon dioxide is adsorbed by the activated carbon, while methane and other gases are released. The purified biogas is then collected and the activated carbon is reactivated by subjecting it to a vacuum.

[0047] VPSA is an effective technique for biogas purification, as it can remove a large amount of carbon dioxide at a low cost. It is also a flexible technique, as it can be adapted to different types of biogas.

[0048] According to one embodiment, the VPSA comprises the following steps: - Biogas is compressed to a high pressure, generally 10 to 20 bar; - The compressed biogas is introduced into an adsorber filled with activated carbon; - Carbon dioxide is adsorbed by activated carbon, while methane and other gases are released; - Purified biogas is collected; - Activated carbon is reactivated by subjecting it to a vacuum.

[0049] According to one embodiment, the biogas is desulfurized and dried before being separated into CH4 and CO2. An analyzer monitors all the gas purity parameters in real time. According to one embodiment of the invention, the purified CH4 consists of at least 97.5% CH4 and the purified CO2 of at least 99% CO2.

[0050] Step d) of the process according to the invention consists of separating the digestate produced in step b) into liquid and solid digestate.

[0051] Digestate is the residue of the methanization process, which is the transformation of organic waste into biogas.

[0052] Digestate is composed of two phases: a liquid phase, called liquid digestate, and a solid phase, called solid digestate. Liquid digestate is a brownish or blackish liquid that contains nutrients, such as nitrogen, phosphorus, and potassium. Solid digestate is a solid material that contains fiber, minerals, and microorganisms.

[0053] The composition of the digestate depends on the nature of the organic waste used for methanization. Plant organic waste generally produces a digestate rich in nitrogen, while animal organic waste generally produces a digestate rich in phosphorus.

[0054] The separation of the digestate can be carried out in different ways, the main ones being the following:

[0055] Centrifugation: Centrifugation is a technique that uses centrifugal force to separate the two phases of digestate. Centrifugation is an effective technique for separating the two phases of digestate, including digestates containing fine particles.

[0056] Microfiltration: Microfiltration is a technique that uses a filter to separate the two phases of the digestate. Microfiltration is an effective technique for separating the two phases of the digestate, including digestates containing coarse particles.

[0057] Flotation: Flotation is a technique that uses a fluid to separate the two phases of digestate. Flotation is an effective technique for separating the two phases of digestate, including digestates containing fatty particles.

[0058] The choice of the most appropriate digestate separation technique depends on the nature of the digestate and the treatment requirements, preferably the technique used is micro-filtration.

[0059] Step e) of the method according to the invention consists of introducing the CO2 purified in step c) and the liquid digestate produced in step d) into at least one photobioreactor comprising at least one strain of microalgae for cultivating said strain. This step makes it possible to provide the microalgae with the nutrients and CO2 it needs to grow and then be used to produce algal biostimulant or biofuel, preferably algal biostimulant.

[0060] The term microalgae, sometimes called microphyte, refers to microscopic algae.

[0061] The liquid fraction of the digestate, rich in dissolved nutrients, is used as a culture medium for microalgae strains that are grown in a photobioreactor. To grow by photosynthesis, these microalgae consume the CO2 from methanization and feed on the nutrients suspended in the liquid digestate. They then produce algal biomass that is harvested when sufficiently concentrated and processed to create biofuel or a fertilizer material that can be used to stimulate plant growth and increase the quality, yield of crops and their resistance to water stress. Preferably, the microalgae produce biomass that is harvested and transformed into biostimulants.

[0062] Preferably, all of the liquid digestate produced in step d) is introduced into the photobioreactor(s).

[0063] According to one embodiment, the CO2 purified in step c) is directly introduced into at least one photobioreactor by a distribution system and / or the liquid digestate produced in step d) is directly introduced into the photobioreactor by a distribution system. Said distribution system may be, for example, a diffuser, hose, pump, nozzle, coil, or a mixture of these.

[0064] Advantageously, the fact that the CO2 purified in step c) is directly introduced into at least one photobioreactor by a distribution system avoids transport and logistics and therefore presents numerous advantages, in particular:

[0065] Cost reduction: Transport and logistics of purified CO2 are expensive. By avoiding these, the production costs of biofuels or algae-based biostimulants can be reduced.

[0066] Improved efficiency: Purified CO2 is a gas that diffuses easily. By introducing it directly into the photobioreactor, it can be ensured that it is used more efficiently by the microalgae.

[0067] Risk reduction: The transport and logistics of purified CO2 can present risks, such as leaks or accidents. By avoiding these, the risks associated with the production of biofuels or biostimulants from algae can be reduced.

[0068] According to one embodiment, at least one photobioreactor is present in a greenhouse.

[0069] According to one embodiment of the invention, the microalgae are chosen from: Spirulina (Arthrospira), Haematococcus pluvialis, Nannochloropsis, Dunaliella salina, Ascophyllum nodosum, Laminaria sp, Ulva sp, Chlorella vulgaris, Spirulina sp, and their mixtures, preferably Chlorella Vulgaris.

[0070] According to one embodiment of the invention, the photobioreactor comprises at least one strain of cyanobacteria. The cyanobacteria are capable of carrying out photosynthesis and absorbing CO2.

[0071] According to one embodiment of the invention, between 20% and 50% by weight of the culture included in each photobioreactor is extracted each day. This collected culture is then allowed to settle for 24 to 48 hours. The microalgae that rest at the bottom of the settling tank are then recovered to produce algal biostimulant or biofuel, preferably algal biostimulant; and the culture medium is then recycled into the photobioreactors.

[0072] The method according to the present invention may further comprise an additional step of producing surface compost and / or repotting from the solid digestate produced in step d). This step makes it possible to recover the solid digestate, which is often considered as waste.

[0073] Solid digestate is composed of fiber, minerals, and microorganisms. It is rich in nutrients, such as nitrogen, phosphorus, and potassium. These nutrients are essential for plant growth.

[0074] The potting soil produced from solid digestate can be used for repotting plants and / or as a top layer in pots. It is an alternative to potting soils traditional, which are often made from non-renewable resources.

[0075] According to one embodiment of the invention, the additional step of producing surface compost or potting soil from the solid digestate produced in step d) comprises a step of mixing said solid digestate with plant material selected from the group comprising at least one perennial plant, and / or at least one annual plant and / or agricultural waste, such as straw, crop residues, etc. and / or forestry waste, such as branches, leaves, etc. and / or urban green waste.

[0076] According to one embodiment of the invention, the solid digestate is mixed with said plant material according to a digestate / plant material volume or weight ratio of between 1:0.25 and 1:1.5, preferably between 1:0.75 and 1:1.25, more preferably according to a 1:1 ratio.

[0077] According to one embodiment of the invention, the solid digestate is mixed with said plant material to form a mixture comprising between 25% and 75% by weight of solid digestate and 25% and 75% by weight of plant material, preferably between 30% and 60% by weight of solid digestate and 30% and 60% by weight of plant material, more preferably between 40% and 55% by weight of solid digestate and 40% and 55% by weight of plant material, even more preferably 50% by weight of solid digestate and 50% by weight of plant material.

[0078] The perennial plant(s) may be selected from the group comprising miscanthus, hemp, sorghum, reed, sugar cane, phragmites australis, licorice, asclepias tuberosa, solidago canadensis, comfrey, and mixtures thereof, preferably miscanthus.

[0079] The annual plant(s) may be selected from the group comprising Burdock, Mustard, Alfalfa, Timothy, Fennel, Wheat, Barley, Oats, Buckwheat and mixtures thereof.

[0080] According to one embodiment of the invention, the plant material is previously ground to an average particle size of between 2.5 and 10 mm, preferably between 3 and 7 mm, more preferably between 4 and 6 mm, even more preferably 5 mm.

[0081] According to one embodiment of the invention, the solid digestate / plant matter mixture is then composted, preferably in an electric composter, more preferably an electric composter with forced ventilation.

[0082] According to one embodiment of the invention, the compost is then mixed with peat and / or at least one mineral according to a compost / peat volume or weight ratio of between 1:0.10 and 1:0.5, preferably between 1:0.15 and 1:0.30, preferably between 1:0.20 and 1:0.25, even more preferably according to a ratio of 1:0.2 and according to a compost / mineral volume or weight ratio of between 1:0.01 and 1:0.05, preferably between 1:0.02 and 1:0.03, preferably in a ratio of 1:0.03.

[0083] According to another embodiment of the invention, the compost is mixed with peat and / or at least one mineral to form a mixture comprising: - between 50% and 95%, preferably between 65% and 90%, more preferably between 75% and 85%, even more preferably between 80% and 85% by weight of compost; and - between 3% and 45%, preferably between 5% and 30%, more preferably between 10% and 25%, even more preferably between 15% and 20% by weight of peat; and - between 0.5% and 5%, preferably between 1% and 4%, preferably between 1.5% and 3.5%, even more preferably between 2% and 3% by weight of at least one mineral.

[0084] The inventors discovered that the use of peat is advantageous because peat is composed of plant fibers, which gives it a light and airy structure, allowing plant roots to develop easily and access the oxygen and nutrients they need. In addition, peat retains water because peat has a high absorption capacity, which helps keep the soil moist. This is important for plants that need moist soil to grow. Peat is generally neutral or acidic, making it suitable for growing many plants.

[0085] The mineral(s) may be selected from the group comprising dolomite, lime, chalk, marl, marine limestone, shell limestone, dolomitic limestone, or a mixture thereof, preferably dolomite.

[0086] The inventors discovered that the use of dolomite is particularly advantageous because it firstly helps correct the acidity of the soil. Dolomite is a limestone rock that contains calcium and magnesium. These elements help to neutralize the acidity of the soil, which is important for the growth of many plants. Dolomite also helps to aerate the soil and improve its drainage. This allows plant roots to develop more easily and access the oxygen and nutrients they need. Finally, dolomite helps to provide nutrients to plants. Dolomite contains calcium and magnesium, two nutrients essential for plant growth.

[0087] According to one embodiment of the invention, the surface or potting soil complies with standard NFU 44-551. Its pH is close to 6.8 and its moisture retention rate is close to 50%.

[0088] The invention also relates to an installation for treating and recycling organic waste, preferably according to the method of the invention comprising: - a unit for pre-treating organic waste, - a unit for methanizing pre-treated organic waste capable of producing and to treat the biogas obtained into purified CO2 and CH4, - a system for separating digestate from methanization capable of providing liquid digestate and solid digestate, - a microalgae culture unit in photo-bioreactors fed by part or preferably all of the liquid digestate and by part or preferably all of the purified CO2.

[0089] The organic waste pretreatment unit may comprise at least one grinding tank comprising a mechanical grinder, at least one mixing tank comprising a mixer, at least one conical-shaped hygienization tank for heating the organic waste, and a cooling tank for cooling the organic waste after heating.

[0090] The pre-treated organic waste methanization unit capable of producing and treating the biogas obtained into purified CO2 and CH4 may comprise at least one methanizer and a biogas treatment unit for desulfurizing, drying, and separating the biogas into CH4 and CO2 and may further comprise an analyzer monitoring in real time all the gas purity parameters.

[0091] The methanization unit may further comprise VPSA technology for the separation and purification of biogas,

[0092] The methanization unit can be connected to an injection system in a natural gas distribution network, preferably a national network such as GRDF in France.

[0093] The system for separating digestate from methanization capable of providing liquid digestate and solid digestate may comprise at least one micro-filter.

[0094] According to one embodiment of the invention, the installation further comprises a unit for producing surface or potting compost from the solid digestate comprising a mixing composter for transforming the solid digestate into potting compost, preferably an electric composter, more preferably an electric composter with forced ventilation.

[0095] Examples

[0096] Example 1: Example of recovery of organic waste according to the invention

[0097] Organic waste arrives by truck and is weighed and an operator ensures the absence of non-organic waste.

[0098] The organic waste is conveyed by a conveyor belt over a funnel-shaped tank. It is ground to 5mm before falling into the tank, then constantly mixed by blades located on a constantly rotating vertical axis.

[0099] The bins, which have rounded bottoms, are cleaned with hot water under high pressure above a pipe which carries this dirty water into the same tank.

[0100] The mixing tank communicates with two other hygienization tanks of the form conical. When one of these two tanks is full, it is closed and heated to 70°C by a coil full of heated water (by a mixed electricity / natural gas heat pump) which surrounds its entire surface. After one hour, the other sanitizing tank takes over from the first. The hot liquid is transferred to the coil of the other tank to avoid unnecessary energy consumption.

[0101] When the temperature of the contents of the hygienization tank reaches 38°C, it is transferred by pumping to the methanizers.

[0102] The biogas produced is transported to a treatment room where it is desulfurized and dried before being separated into CH4 and CO2. An analyzer monitors all the gas purity parameters in real time.

[0103] The 97.5% pure CH4 is odorized and conveyed at a pressure of 4.5 bars to the GRDF injection room.

[0104] The CO2 is conducted with a pressure of 3.5 bars towards the greenhouse which houses the photobioreactors.

[0105] The contents of the methanizers are transformed after 20 days of residence into a liquid material called digestate. 80% of the volume of incoming bio-waste is extracted in the form of digestate every day.

[0106] This digestate is transported by pipe to a room where it is separated into two phases with a micro-filter.

[0107] The most liquid part is conveyed to the photobioreactors, where it will be mixed with the injected CO2. The microalgae strains present in the photobioreactors will then be able to multiply under photosynthetic conditions.

[0108] 35% by weight of the total culture contained in each photobioreactor is extracted each day. This collected culture is then put into a decanting condition. After 36 hours, the microalgae rest at the bottom of the decantation tank. The culture medium is recycled into the photobioreactors.

[0109] The microalgae are extracted from the bottom of the tank and prepared using different methods, depending on their destination.

[0110] The least liquid part of the digestate is mixed with its equivalent in volume of miscanthus crushed to 5 mm. The mixture is introduced into an electric composter with forced ventilation. This is a rotating helical cylinder equipped with 15 "niches", the beginning of which is heated to 70°C. The cylinder rotates on itself for 15 days. The contents of a "niche" come out by gravity after 15 days, meeting in this treatment the standard of a NFU 44-051 compost.

[0111] This compost is then mixed at 20% of its volume with Brière earth, a variety of peat, and at 3% of its volume with dolomite, a carbonate sedimentary rock composed of at least 50% dolomite, a double carbonate of calcium and magnesium, of chemical composition CaMg(CO3)2, which crystallizes in lo- prisms blood-like (rhombohedrons).

[0112] The compost is thus transformed into potting soil meeting the NFU 44-551 standard. Its pH is close to 6.8 and its moisture retention rate is close to 50%.

Claims

Claims

1. A method for recovering organic waste comprising the steps of: a. Pretreatment of the organic waste; b. Introduction of the organic waste into at least one methanizer and production of biogas and digestate by said at least one methanizer; c. Separation and purification of the biogas allowing separation of CH4 and CO2; d. Separation of the digestate produced in step b) into liquid and solid digestate; e. Cultivation of at least one strain of microalgae by introduction of the CO2 purified in step c) and the liquid digestate produced in step d) into a photobioreactor comprising said at least one strain of microalgae.

2. The method of claim 1, wherein the pretreatment step comprises at least one of grinding, homogenizing, heating and / or cooling the organic waste.

3. The method according to any one of claims 1 or 2, comprising at least two methanizers, preferably installed in parallel.

4. The method according to any one of claims 1 to 3, wherein the separation and purification of the biogas to separate CH4 and CO2 is carried out by vacuum pressure swing adsorption (VPSA).

5. The method according to any one of claims 1 to 4, comprising an additional step of producing surface compost and / or potting from the solid digestate produced in step d).

6. The method according to any one of claims 1 to 5, where the microalgae are chosen from: Ascophyllum nodosum, Laminaria sp, Ulva sp, Chlorella vulgaris, Spirulina sp, and mixtures thereof, preferably Chlorella Vulgaris.

7. The process according to any one of claims 1 to 6, wherein the purified biogas consists of at least 97.5% CH4 and 99% CO2

8. The method of any one of claims 1 to 7, wherein the microalgae produce biomass which is harvested and processed into biostimulants.

9. An installation for the treatment and recycling of organic waste comprising: - a unit for pre-treatment of organic waste, - a unit for methanization of pre-treated organic waste capable of producing and treating the biogas obtained into purified CO2 and CH4, - a system for separating the digestate resulting from the methanization capable of providing a liquid digestate and a solid digestate, and - a unit for cultivating microalgae in photo-bioreactors supplied with part or preferably all of the liquid digestate and with part or preferably all of the purified CO2.