PROCEDURE OF PREPARATION OF A BIOGAS

Abstract

The invention relates to a process for preparing biogas from a substrate comprising a step of anaerobic digestion of said substrate in the presence of fermented molasses, the content of fermented molasses being between 0.01% and 15% by weight of substrate, to a composition for improving the production of biogas, and to the use of fermented molasses or a composition for improving the production of biogas as an additive in a process for preparing biogas from a substrate.

Description

Title of the invention: PROCESS FOR PREPARING A BIOGAS Technical field

[0001] The invention relates to a method for preparing biogas from substrate. State of the art

[0002] Methanization corresponds to the degradation of organic substrates under anaerobic conditions by microorganisms, which leads to the production of biogas, a mixture mainly composed of carbon dioxide (CO2), methane (CH4), and water vapor (H2O). Biogas can be used directly to produce heat and electricity. It can also be injected into the natural gas network in order to promote the consumption of renewable gas on a territorial and national scale. In this case, the biogas must be purified so that its characteristics are similar to those of natural gas. This is called biomethane. Digestate is the portion of waste remaining at the end of the methanization process. It can be used as a natural fertilizer, as a substitute for chemical fertilizers.

[0003] Methanization has many advantages. It allows the recovery of waste, particularly livestock effluent, and the capture and recovery of methane produced naturally during the decomposition of organic matter, particularly livestock effluent. Biogas and biomethane can replace fossil energy sources such as oil, coal and natural gas.

[0004] Biogas production will grow significantly in the coming years. There is a continual need to improve biogas preparation processes. Summary

[0005] An aim of the present invention is to propose a process for producing biogas, said process being efficient, easy to implement, and making it possible to accelerate the production of biogas and / or to increase the methanogenic power of the substrates used.

[0006] Another object of the present invention is to provide a composition which can be mixed with a substrate as an additive, and which makes it possible to improve the production of biogas from this substrate.

[0007] Thus, according to a first aspect, the invention relates to a process for preparing biogas from a substrate characterized in that it comprises a step of anaerobic digestion of said substrate in the presence of fermented molasses, the content of fermented molasses being between 0.01% and 15% by weight of substrate.

[0008] In one or more embodiments, the fermented molasses is fermented beet molasses, fermented cane molasses, or a mixture thereof.

[0009] In one or more embodiments, the fermented molasses comprises at least 60% by weight of fermented beet molasses.

[0010] In one or more embodiments, the fermented molasses content is between 0.01% and 5%, preferably between 0.05% and 2%, by weight of substrate.

[0011] In one or more embodiments, the anaerobic digestion step is carried out in the presence of a yeast extract, the total content of fermented molasses and yeast extract being in particular between 0.01% and 15% by weight of substrate.

[0012] In one or more embodiments, the dry weight ratio of fermented molasses: yeast extract is between 80:20 and 99:1, preferably between 85:15 and 99:1.

[0013] In one or more embodiments, the fermented molasses and the yeast extract are added simultaneously or separately to the substrate.

[0014] According to the second aspect, the composition for improving biogas production comprising, in % by dry weight: - between 80% and 99% fermented molasses, - between 1% and 20% yeast extract.

[0015] In one or more embodiments, the fermented molasses is fermented beet molasses, fermented cane molasses, or a mixture thereof.

[0016] In one or more embodiments, the fermented molasses comprises at least 60% by weight of fermented beet molasses.

[0017] According to a third aspect, the invention relates to a process for preparing the composition as defined above comprising a step of mixing fermented molasses and yeast extract.

[0018] According to a fourth aspect, the invention relates to the use of fermented molasses or a composition as defined in the first aspect of the invention as an additive in a process for preparing biogas from a substrate.

[0019] In one or more embodiments, the use is for increasing the rate of biogas production.

[0020] In one or more embodiments, the use is for increasing the yield of the biogas substrate. Detailed description 1. Biogas preparation process

[0021] According to a first aspect, the present invention relates to a process for preparing biogas from a substrate characterized in that it comprises a digestion step anaerobic treatment of said substrate in the presence of fermented molasses, the content of fermented molasses being between 0.01% and 15% by weight of substrate.

[0022] For the purposes of the present invention, a process for preparing biogas, or methanization process, is a process which makes it possible to obtain biogas by anaerobic digestion (in the absence of oxygen) of a fermentable substrate (having the capacity to ferment).

[0023] For the purposes of the present invention, the term “biogas” designates a gaseous mixture composed of approximately 50% to 70% methane (CH4), 20% to 50% carbon dioxide (CO2) and some trace gases (NH3, N2, H2S).

[0024] In the present invention, methanization involves the degradation of the organic matter of the substrate by microorganisms in the absence of oxygen, therefore in an anaerobic environment, unlike composting which is an aerobic reaction.

[0025] For the purposes of the present invention, the term “anaerobic digestion” means a reaction of digestion (i.e. fermentation) of a substrate by microorganisms, in the absence of oxygen.

[0026] The conditions for implementing anaerobic digestion are well known to those skilled in the art. It is typically carried out in a digester or methanizer, by bringing the substrate into contact with microorganisms.

[0027] Anaerobic digestion is preferably carried out in the presence of microorganisms brought into contact with the substrate. The microorganisms are preferably in the form of an inoculum.

[0028] In the present invention, the term "inoculum" designates a population of microorganisms comprising at least one or more methanogenic microorganisms as detailed below. This inoculum may in particular be in the form of a powder or a liquid.

[0029] The conditions for implementing the process of the invention and in particular the anaerobic digestion step are detailed below in this description. Improvement of biogas production

[0030] In the course of its research, the Applicant Company discovered that the digestion of a manure-type substrate in the presence of small quantities of fermented molasses could improve or positively influence the production of biogas. In particular, it has been shown that such additions of fermented molasses to a manure-type substrate allows (i) an improvement in the kinetics of biogas production, or in other words an increase in the speed of biogas production, and / or (ii) an improvement in the yield of the substrate in biogas, or in other words an increase in the methanogenic potential of the substrate, i.e. an increase in the quantity of biogas produced for a given quantity of substrate entering the biogas production process.

[0031] Noting a certain disparity in the results and therefore a reproducibility that could be improved, the Applicant Company continued its research and showed that, surprisingly, the use of fermented molasses in combination with a yeast extract allows for better reproducibility of the results, which is very advantageous in the context of an industrial application.

[0032] The inventors have therefore shown on the one hand that it is possible to accelerate and / or increase the production of biogas from a given quantity of substrate by the addition of fermented molasses, and on the other hand that it is possible to optimize the reproducibility of this acceleration and / or increase in production by the addition of fermented molasses in combination with a yeast extract. It has further been shown that this improvement in biogas production occurs for additions as low as 0.1% by weight of substrate.

[0033] Thus, in the biogas production process of the invention, fermented molasses, used alone or in combination with a yeast extract, makes it possible to produce one or more of the following effects, which are not mutually exclusive and can be combined: (i) an increase in the rate of biogas production; and / or (ii) an increase in the yield of the substrate in biogas.

[0034] In other words, in the process of the invention, the fermented molasses, used alone or in combination with a yeast extract, has the effect of potentiating the methanogenic power of the substrate and / or of catalyzing the anaerobic digestion of the substrate.

[0035] Biogas production is improved by the addition of fermented molasses alone or in combination with a yeast extract. However, it may be difficult to determine whether this improvement is due to the fact that the fermented molasses alone or in combination with a yeast extract has exerted a potentiating effect on the methanogenic power of the substrate, a catalytic effect on anaerobic digestion, or whether the observed improvement is due to a mixture of these two effects.

[0036] In one or more embodiments, the use of fermented molasses, alone or in combination with a yeast extract, makes it possible to increase the rate of biogas production.

[0037] In the present invention, the expressions "increasing the rate of biogas production" and "catalyzing the production of biogas" are considered interchangeable and denote an increase in the amount of biogas produced from a given amount of substrate in a given period of time. This increase in the rate of biogas production can be obtained with or without an increase in the methanogenic power of the substrate.

[0038] The reaction rate can be increased over all or part of the process implementation, in particular over all or part of the anaerobic digestion step.

[0039] In one or more embodiments, the rate of biogas production is increased throughout the anaerobic digestion step.

[0040] In one or more embodiments, the rate of biogas production is increased upon initiation of the anaerobic digestion step.

[0041] The term "initiation of the anaerobic digestion step" refers to the beginning of the process by which anaerobic microorganisms begin to degrade the substrate to produce biogas. This step is crucial in the anaerobic digestion process because it is at this point that the appropriate conditions are established to allow the growth and activity of methanogenic microorganisms.

[0042] In one or more embodiments, the fermented molasses used alone or in combination with a yeast extract makes it possible to increase the yield of the biogas substrate.

[0043] In the present invention, the expressions "increase in the yield of the substrate in biogas" and "increase in the methanogenic potential of the substrate" are considered interchangeable, and designate an increase in the total quantity of biogas which can be produced from a given quantity of substrate entering the biogas production process, following its total degradation under anaerobic conditions.

[0044] In the present invention, the expression "methanogenic power" or "methanogenic potential", often called BMP (acronym for "biochemical methane potential"), corresponds to the quantity of methane produced by a substrate during its total or in other words complete degradation in anaerobic conditions during the methanization process. This volume of methane, relative to the quantity of fresh, dry (DM) or volatile (MV) substrate, is generally expressed under normal temperature and pressure conditions (0°C, 1013 hPa). This indicator is well known to those skilled in the art and is used in particular to size methanization units, measure inputs and control their quality, but also to evaluate possible carbon losses during storage time.

[0045] The methanogenic potential can be measured according to a method comprising the following steps: 1. Sample preparation: Substrate samples are collected and prepared for analysis. They are usually ground or homogenized to achieve a uniform particle size; 2. Inoculation: A known amount of inoculum, e.g., anaerobic sludge or methanogenic microorganism culture, is added to the reaction flasks to seed the substrate samples and initiate the anaerobic digestion process; 3. Vial Conditioning: Substrate samples are placed in sealed reaction vials, with anaerobic conditions maintained inside to simulate the environment in an anaerobic digester; 4. Gas Volume Measurement: The bottles are placed in a gas production measuring device, where the volumes of gas produced are regularly measured over time. 5. Calculation of BMP: Cumulative methane production is measured over a given period of time, usually several weeks, typically 3 weeks. BMP is then calculated by dividing the amount of methane produced by the amount of substrate used, and usually expressed in units of volume (e.g., mL of methane per gram of substrate dry matter).

[0046] A method for measuring BMP is detailed in the Examples section.

[0047] In one or more embodiments, the fermented molasses used alone or in combination with a yeast extract in the process according to the invention makes it possible to increase both the rate of biogas production and the yield of the biogas substrate. Fermented molasses

[0048] In the present invention, the term "fermented molasses" designates a co-product of molasses obtained after fermentation of the latter by bacteria, yeasts or fungi, said fermentation making it possible to obtain so-called "noble" products such as baker's yeast, ethyl alcohol or even citric and glutamic acid.

[0049] Preferably, the fermented molasses is obtained via the fermentation of molasses by yeasts.

[0050] The fermented molasses used for implementing the method according to the invention can be obtained from beet molasses, cane molasses, or a mixture of beet molasses and cane molasses.

[0051] Preferably, the fermented molasses is obtained from a mixture of fermented molasses comprising fermented beet molasses and fermented cane molasses.

[0052] The fermented molasses preferably comprises fermented beet molasses, fermented cane molasses, or a mixture thereof.

[0053] When the fermented molasses is a mixture of fermented beet molasses and fermented cane molasses, it preferably comprises predominantly fermented beet molasses.

[0054] For example, the mixture may contain at least 60% fermented beet molasses, at least 70% fermented beet molasses, at least 80% fermented beet molasses, at least 90% fermented beet molasses, or at least 95% fermented beet molasses, % by dry weight of mixture. Advantageously, when the fermented molasses is a mixture of fermented beet molasses and fermented cane molasses, said mixture contains at least 90% fermented beet molasses, % by weight of mixture.

[0055] Preferably, the mixture contains between 60% and 95% fermented beet molasses, preferably between 70% and 90% fermented beet molasses, preferably between 80% and 90% fermented beet molasses, % by weight of mixture, the remainder preferably being fermented cane molasses. Preferably, the mixture is such that the total of the percentages of fermented beet molasses and fermented beet molasses is 100%.

[0056] Fermented molasses generally contains more than 90% water but the latter can advantageously be concentrated in order to reduce the quantity of water and obtain higher dry matter levels.

[0057] Thus, the dry matter content of the fermented molasses, or of the mixture of beet molasses and cane molasses according to the invention may be from 50% to 80%. Preferably, the dry matter content of the fermented molasses is from 55% to 75%, and very particularly from 55% to 65%, such as for example approximately 60%.

[0058] Conventionally, since it is intended or was used as fertilizer or in animal feed, fermented molasses is also defined by its distribution of nitrogenous materials and by its aminogram. The fermented molasses according to the invention can thus have a distribution of nitrogenous materials as follows: - nitrogen of total amino acids: 25% to 50% of total nitrogen; - betaine nitrogen: 0% to 40% of total nitrogen - ammoniacal nitrogen: 2% to 3% of total nitrogen.

[0059] Concerning the aminogram of the proteins of the fermented molasses according to the invention, the average amino acid contents can be as presented below, the content ranges being given in g / kg of dry matter: Aspartic acid: 6 - 8 Threonine: 0.5 - 3 Serine: 1 - 4 Glutamic acid: 10-50 Proline: 3 - 4 Glycine: 4 - 5 Alanine: 2.5 - 3.5 Valine: 2.5 - 3.5 Methionine and cysteine: 0.5 - 3 Isoleucine: 1.5 - 2.5 Tyrosine: 2 - 3.5 Leucine: 3 - 4.5 Phenylalanine: 1-2 Lysine: 0.5 - 2.5 Histidine: 0.5 - 2 Arginine: 0.2 - 1.

[0060] As a co-product of fermentation, fermented molasses has a low sugar content. The term "low sugar content" means fermented molasses comprising less than 5%, less than 4%, less than 3%, less than 2%, and most particularly, less than 1% by weight of sugars relative to the total mass of the dry extract. Preferably, the fermented molasses is free of fermentable sugars.

[0061] The fermented molasses used in the present invention may be a raw fermented molasses or a molasses that has undergone one or more chemical or physicochemical treatments. For example, the fermented molasses may undergo depotassification or demineralization. Such treatments may modify the nitrogenous matter composition of the fermented molasses. A depotassification treatment consists, for example, of acidification of the raw fermented molasses with a solution of H2 SO4, followed by neutralization with ammonia.

[0062] The treatments that can be applied to fermented molasses vary the mineral content qualitatively and quantitatively. Thus, a raw fermented molasses may have a crude ash content of 14% to 22% by weight relative to the raw product and a potassium content of 5% to 18% by weight relative to the raw product. On the other hand, in the case of depotassium-depleted or demineralized fermented molasses, the crude ash content varies from 5% to 14% by weight relative to the raw product and the potassium content is generally less than 4% by weight relative to the raw product.

[0063] Due to a high ash content, the raw fermented molasses has a density which can vary from 1.10 to 1.50. Preferably, the density of the fermented molasses is from 1.20 to 1.40, and most preferably from 1.25 to 1.35.

[0064] The fermented molasses according to the invention preferably has a viscosity of 70 mPa.s to 5000 mPa.s, preferably of 70 mPa.s to 900 mPa.s.

[0065] Viscosity is determined using a cone-plate rheometer at a temperature of 20°C, at a shear rate of 20 s1.

[0066] For example, viscosity can be determined according to the protocol detailed below: The measurements are carried out: - in a Kinexus Pro+ rheometer from Netzsch, featuring a cylindrical cassette (integrated tank), with a C34 spindle featuring a smooth surface geometry, made of stainless steel, with a diameter of 33.64mm, standard DIN standard, - by placing approximately 30 ml of sample in the tank, - by choosing the following parameters: Temperature (Pelletier effect) = 20°C, Start shear rate = 0.1 s'1, End shear rate = 500 s'1, Number of points per decade of shear rate = 10 points. The viscosity retained is the viscosity recorded for a shear rate of 20 s1.

[0067] The fermented molasses according to the invention preferably has a pH of between 2 and 12, preferably between 4.5 and 8. Yeast extract

[0068] The yeast extract used in the biogas preparation process according to the present invention is preferably a yeast fraction, preferably a soluble yeast fraction.

[0069] Generally, a distinction is made between yeast cell walls (insoluble fraction) and yeast extracts (soluble fraction). Conventionally, yeast cell walls or yeast extracts are obtained by a process comprising an autolysis or enzymatic hydrolysis step, essentially by proteases, followed by a step of separating the soluble fraction from the insoluble fraction, the isolated insoluble fraction corresponding to the yeast cell walls and the soluble fraction corresponding to the yeast extract. The insoluble fraction and / or the soluble fraction can then be dried. Methods for obtaining yeast cell walls and yeast extracts are known in the art (see, for example, the reference work “Yeast Technology”, 2nd edition, 1991, G. Reed and T.W. Nogodawithana, published by Van Nostrand Reinhold, New York, ISBN 0-442-31892-8).

[0070] A yeast extract may be in dry form, preferably in the form of a fine water-soluble powder, in liquid form, in the form of a paste or in the form of a granule. The yeast extract is considered to be in dry form when its dry matter content is at least 85%. If its dry matter content is less than 70% by mass, it is considered to be in liquid form. From 70% and below 85% by mass of dry matter, the yeast extract is considered to be in the form of a paste. The yeast extract used is preferably in dry form, more preferably in the form of a fine water-soluble powder. A yeast extract comprises mainly protein materials, preferably at least 55% protein materials.

[0071] In one or more embodiments, the yeast extract is a downgraded yeast extract, i.e., a yeast extract that cannot be marketed for its original use due to non-compliance related to parameters for the initially intended application such as non-compliant particle size, contamination, non-compliant quantity of salts, or exceeding the recommended use-by date.

[0072] This is particularly advantageous, insofar as it makes it possible to industrially and commercially recover downgraded yeast extracts intended for destruction.

[0073] In one or more embodiments, the yeast extract is a yeast extract downgraded for reasons of microbiological contamination, typically by bacteria such as E. Coli, Salmonella, Staphylococcus, or Clostridium, by yeasts, or fungi (molds).

[0074] In one or more embodiments, the yeast extract is a yeast extract unsuitable for use in food preparation.

[0075] The dry weight of the yeast extract preferably represents at least 90% of the total weight of the extract, more preferably at least 95% of the weight of the extract. In other words, the majority of the mass of the extract preferably consists of non-liquid matter once the water has been removed.

[0076] The yeast extract advantageously has a total nitrogen content of between 1% and 20%, between 1% and 15%, % by dry weight of yeast extract. The total nitrogen content of the yeast extract may in particular be between 5% and 20%, between 5% and 15%, % by dry weight of yeast extract. Substrate

[0077] For the purposes of the present invention, the terms “substrate”, “organic substrate”, “methanogenic substrate” or “methanization substrate” may be used interchangeably and designate any substrate conventionally used in a biogas preparation process.

[0078] The quantity of biogas produced by the process according to the invention may depend in particular on the nature of the substrate used.

[0079] Some organic materials are much more methanogenic than others. Fats, and especially greases, generally have the highest yield potential, other carbohydrate biopolymer type organic materials, such as cellulose or hemicellulose, have a slower degradation rate with a much lower biogas yield.

[0080] In practice, for so-called on-farm methanization units, the raw materials most used in methanization processes are animal waste (particularly cattle and pig manure and slurry)

[0081] Industrial-type methanization units preferentially use as substrate mixtures of food waste, sludge, wastewater treatment plant, flotation grease, grease and waste from the food industry, and green waste. The disadvantage of mixing these different raw materials is that it often provides a substrate with a low methanization speed and yield because this mixture is low in fermentable carbon elements.

[0082] Preferably, the substrate consists of organic products or by-products of animal or plant origin, and more particularly animal and plant waste, in particular chosen from animal excrement, in particular chosen from manure and slurry, agri-food waste, sewage treatment plant sludge, flotation fats and green waste.

[0083] Contents of fermented molasses alone or in combination with a yeast extract

[0084] The process of the invention comprises a step of anaerobic digestion of a substrate in the presence of fermented molasses, the content of fermented molasses being between 0.01% and 15% by weight of substrate.

[0085] Without wishing to be bound by a particular theory, the Applicant company considers that: - the addition of fermented molasses, alone or in combination with yeast extract, to a substrate such as manure makes it possible to increase the rate of biogas production up to contents of 15% by weight of substrate; - the addition of fermented molasses, alone or in combination with yeast extract, to a substrate makes it possible to increase the yield of said substrate in biogas up to contents of approximately 10% by weight of substrate. It has in fact been shown that contents between 0.1% and 10% make it possible to obtain higher BMP values, but that for contents above 10%, for example for an addition of 15% by weight of substrate, an inhibition phenomenon takes place and the final BMP is equivalent to that of manure alone. Fermented molasses content

[0086] In one or more embodiments, the fermented molasses content by weight of substrate is between 0.01% and 15%, between 0.01% and 12%, between 0.01% and 10%, between 0.01% and 9%, between 0.01% and 8%, between 0.01% and 7%, between 0.01% and 6%, or between 0.01% and 5%.

[0087] In one or more embodiments, the fermented molasses content by weight of substrate is between 0.05% and 15%, between 0.05% and 12%, between 0.05% and 10%, between 0.05% and 9%, between 0.05% and 8%, between 0.05% and 7%, between 0.05% and 6%, or between 0.05% and 5%.

[0088] Contents between 0.05% and 15% or between 0.05% and 10% are preferred.

[0089] Remarkably, additions of fermented molasses, alone or in combination with yeast extract, at levels of 0.1%, 0.5%, 1% and 2% by weight of substrate result in similar improvements.

[0090] In one or more embodiments, the fermented molasses content is greater than or equal to 0.01%, greater than or equal to 0.02%, greater than or equal to 0.03%, greater than or equal to 0.04%, greater than or equal to 0.05%, greater than or equal to 0.06%, greater than or equal to 0.07%, greater than or equal to 0.08%, or greater than or equal to 0.09%, by weight of substrate.

[0091] It may in particular be at least 0.075% by weight of substrate.

[0092] In one or more embodiments, the fermented molasses content by weight of substrate is less than or equal to 10%, less than or equal to 9%, less than or equal to 9%, less than or equal to 8%, less than or equal to 7%, less than or equal to 6%, less than or equal to 5%, less than or equal to 4%, or less than or equal to 3%, less than or equal to 2%.

[0093] In one or more embodiments, the content of fermented molasses by weight of substrate is between 0.01% and 5%, between 0.01% and 4%, between 0.01% and 3%, between 0.01% and 2%, between 0.01% and 1%.

[0094] In one or more embodiments, the content of fermented molasses by weight of substrate is between 0.05% and 5%, between 0.05% and 4%, between 0.05% and 3%, between 0.05% and 2%, between 0.05% and 1%.

[0095] Contents between 0.01% and 5% or between 0.05% and 5% are preferred.

[0096] Total content of fermented molasses and yeast extract

[0097] The Applicant company has shown that, surprisingly, the addition, in addition to fermented molasses, of small quantities of yeast extract makes it possible to improve the reproducibility of the results.

[0098] In one or more embodiments, the anaerobic digestion step is carried out in the presence of fermented molasses and a yeast extract, the total content of fermented molasses and yeast extract being in particular between 0.01% and 15% by weight of substrate.

[0099] The fermented molasses and the yeast extract are added to the substrate in a dry weight ratio of fermented molasses: yeast extract which is preferably between 80:20 and 99:1.

[0100] In one or more embodiments, the dry weight ratio of fermented molasses: yeast extract is between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5.

[0101] In one or more embodiments, the total content of fermented molasses and yeast extract, by weight of substrate, is between 0.01% and 15%, between 0.01% to 12%, between 0.01% and 10%, between 0.01% and 9%, between 0.01% and 8%, between 0.01% and 7%, between 0.01% and 6%, or between 0.01% and 5%.

[0102] In one or more embodiments, the total content of fermented molasses and yeast extract, by weight of substrate, is between 0.05% and 15%, between 0.05% and 12%, between 0.05% and 10%, between 0.05% and 9%, between 0.05% and 8%, between 0.05% and 7%, between 0.05% and 6%, or between 0.05% and 5%.

[0103] Contents between 0.05% and 15% or between 0.05% and 10% are preferred.

[0104] Remarkably, additions of fermented molasses in combination with yeast extract, at levels of 0.1%, 0.5%, 1% and 2% by weight of substrate, result in similar improvements.

[0105] In one or more embodiments, the total content of fermented molasses and yeast extract, by weight of substrate, is greater than or equal to 0.01%, greater than or equal to 0.02%, greater than or equal to 0.03%, greater than or equal to 0.04%, greater than or equal to 0.05%, greater than or equal to 0.06%, greater than or equal to 0.07%, greater than or equal to 0.08%, or greater than or equal to 0.09%.

[0106] It may in particular be at least 0.075% by weight of substrate.

[0107] In one or more embodiments, the total content of fermented molasses and yeast extract, by weight of substrate, is less than or equal to 20%, is less than or equal to 19%, is less than or equal to 18%, is less than or equal to 17%, is less than or equal to 16%, is less than or equal to 15%, is less than or equal to 10%, less than or equal to 9%, less than or equal to 9%, less than or equal to 8%, less than or equal to 7%, less than or equal to 6%, less than or equal to 5%, less than or equal to 4%, or less than or equal to 3%, less than or equal to 2%.

[0108] In one or more embodiments, the total content of fermented molasses and yeast extract, by weight of substrate, is between 0.01% and 5%, between 0.01% and 4%, between 0.01% and 3%, between 0.01% and 2%, between 0.01% and 1%.

[0109] In one or more embodiments, the total content of fermented molasses and yeast extract, by weight of substrate, is between 0.05% and 5%, between 0.05% and 4%, between 0.05% and 3%, between 0.05% and 2%, between 0.05% and 1%.

[0110] Contents between 0.01% and 5% or between 0.05% and 5% are preferred.

[0111] Thus, in one or more embodiments, the anaerobic digestion step of the substrate is produced in the presence of: - from 0.01% to 15%, preferably from 0.05% to 15% of fermented molasses, by weight of substrate, and - a yeast extract present in a ratio by dry weight of fermented molasses: yeast extract in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, the total content of fermented molasses and yeast extract being in particular between 0.05% and 20%, preferably between 0.05% and 18%, more preferably between 0.05% and 5%, by weight of substrate.

[0112] In one or more embodiments, the step of anaerobic digestion of the substrate is carried out in the presence of: - from 0.01% to 10%, preferably from 0.05% to 10% of fermented molasses, by weight of substrate, - a yeast extract present in a ratio by dry weight of fermented molasses: yeast extract in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, the total content of fermented molasses and yeast extract being in particular between 0.05% and 15%, preferably between 0.05% and 10%, more preferably between 0.05% and 5%, by weight of substrate.

[0113] In one or more embodiments, the step of anaerobic digestion of the substrate is carried out in the presence of: - from 0.01% to 5%, preferably from 0.05% to 5% of fermented molasses, by weight of substrate, - a yeast extract present in a ratio by dry weight of fermented molasses: yeast extract in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, the total content of fermented molasses and yeast extract being in particular between 0.05% and 10%, more preferably between 0.05% and 5%, by weight of substrate.

[0114] In one or more embodiments, the step of anaerobic digestion of the substrate is carried out in the presence of: - from 0.01% to 2%, preferably from 0.05% to 2% of fermented molasses, by weight of substrate - a yeast extract present in a ratio by dry weight of fermented molasses: yeast extract in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, the total content of fermented molasses and yeast extract by weight of substrate being in particular between 0.05% and 5%, by weight of substrate

[0115] In one embodiment, the step of anaerobic digestion of the substrate is carried out with, by weight of substrate: - from 0.01% to 15%, preferably from 0.05% to 15% of fermented molasses, - from 0.01% to 4%, preferably from 0.01% to 3% of yeast extract, the dry weight ratio of fermented molasses: yeast extract being in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, and / or the total content of fermented molasses and yeast extract being in particular between 0.05% and 18%, preferably between 0.05% and 17%, more preferably between 0.05% and 16%, more preferably between 0.05% and 15%, by weight of substrate.

[0116] In one embodiment, the step of anaerobic digestion of the substrate is carried out with, by weight of substrate: - from 0.01% to 10%, preferably from 0.05% to 10% of fermented molasses - from 0.001% to 3%, preferably from 0.001% to 2% of yeast extract, the dry weight ratio of fermented molasses: yeast extract being in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, and / or the total content of fermented molasses and yeast extract being in particular between 0.05% and 12%, preferably between 0.05% and 11%, more preferably between 0.05% and 10%, by weight of substrate.

[0117] In one embodiment, the step of anaerobic digestion of the substrate is carried out with, by weight of substrate: - from 0.01% to 5%, preferably from 0.05% to 5% of fermented molasses, - from 0.001% to 2%, preferably from 0.001% to 1% of yeast extract, the dry weight ratio of fermented molasses: yeast extract being in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, and / or the total content of fermented molasses and yeast extract being in particular between 0.05% and 7%, preferably between 0.05% and 6%, more preferably between 0.05% and 5%, by weight of substrate.

[0118] In one embodiment, the step of anaerobic digestion of the substrate is carried out with, by weight of substrate: - from 0.01% to 2%, preferably from 0.05% to 1% of fermented molasses, - from 0.001% to 1%, preferably from 0.001% to 0.4% of yeast extract, the dry weight ratio of fermented molasses: yeast extract being in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, and / or the total content of fermented molasses and yeast extract being in particular between 0.05% and 3%, preferably between 0.05% and 2%, more preferably between 0.05% and 1%, by weight of substrate.

[0119] In one embodiment, the step of anaerobic digestion of the substrate is carried out with, by weight of substrate: - from 0.01 to 14% fermented molasses, - from 0.001 to 5% yeast extract, the dry weight ratio of fermented molasses: yeast extract being in particular between 80:20 and 99:1, between 80:20 and 99:5, or between 85:15 and 95:5, and / or the total content of fermented molasses and yeast extract being in particular between 0.05% and 15%, preferably between 0.05% and 10%, more preferably between 0.05% and 5%, by weight of substrate. Additions

[0120] Advantageously, the biogas production process according to the invention comprises the following steps: a) providing a substrate, b) adding microorganisms to the substrate, c) adding fermented molasses to the substrate, d) anaerobic digestion of the substrate by the microorganisms, e) optionally, collecting the biogas produced.

[0121] As detailed in the present description, according to the method of the present invention, the anaerobic digestion can be carried out in the presence of fermented molasses alone or in combination with a yeast extract.

[0122] The fermented molasses and yeast extract can be added simultaneously or separately to the substrate.

[0123] In one or more embodiments, the fermented molasses and the yeast extract are added simultaneously, optionally in the form of a composition as defined in the second aspect of the invention.

[0124] In one or more embodiments, the fermented molasses and the yeast extract are added simultaneously, optionally in the form of a composition as defined in the second aspect of the invention. Advantageously, the method for producing biogas comprises the following steps: a) providing a substrate, b) adding microorganisms to the substrate, c) concomitantly adding to the substrate fermented molasses and yeast extract, optionally in the form of a composition as defined in the second aspect of the invention, d) anaerobic digestion of the substrate by the microorganisms, e) optionally, collecting the biogas produced.

[0125] In one or more embodiments, steps b) and c) are carried out together, which means that the microorganisms, the fermented molasses and the yeast extract are added concomitantly to the substrate, the fermented molasses and the yeast extract optionally being added in the form of a composition as defined in the second aspect of the invention.

[0126] In one or more embodiments, step c) is carried out before step d), which means that the fermented molasses and the yeast extract are added concomitantly to the substrate, before the anaerobic digestion, the fermented molasses and the yeast extract being optionally added in the form of a composition as defined in the second aspect of the invention. The fermented molasses and the yeast extract make it possible to initiate anaerobic digestion.

[0127] In one or more embodiments, step c) is carried out during step d), which means that the fermented molasses and the yeast extract are added during the anaerobic digestion, concomitantly with the substrate, the fermented molasses and the yeast extract being optionally added in the form of a composition as defined in the second aspect of the invention.

[0128] In one or more embodiments, the fermented molasses and the yeast extract are added separately to the substrate, a step of adding another constituent possibly being interposed between the step of adding the fermented molasses and the step of adding the yeast extract. Advantageously, the biogas production method comprises the following steps: a) providing a substrate; b) adding microorganisms to the substrate; c) adding fermented molasses and yeast extract separately to the substrate, a step of adding another constituent such as adding microorganisms optionally being interposed between these two additions, the fermented molasses being preferably added first; (d) anaerobic digestion of the substrate by microorganisms; e) optionally, collect the biogas produced.

[0129] Advantageously, the substrate can be treated solely using microorganisms, fermented molasses, yeast extract, and optionally water.

[0130] In other words, in one or more embodiments, the implementation of the method of the invention advantageously does not require other additives, treatment products, whether liquid or solid, organic or mineral. Implementation of the method of the invention

[0131] The conditions for implementing a methanization process are well known to those skilled in the art. The implementation of certain of the steps of the process, of the invention, in particular that of adding microorganisms to the substrate and anaerobic digestion are detailed below.

[0132] The method according to the invention is preferably implemented in a digester or methanizer.

[0133] The substrate, the microorganisms, the fermented molasses and, where appropriate, the yeast extract are therefore preferably added to the methanizer by the usual means known to those skilled in the art. Adding the substrate

[0134] The substrate subjected to digestion can be in any form, for example in the form of liquid, paste, solid.

[0135] The viscosity of the substrate can be adjusted in particular by mixing it with water. Addition of microorganisms

[0136] In one embodiment, the microorganisms are added in the form of an inoculum, concomitantly or after the addition of the substrate in the methanizer.

[0137] Preferably, the microorganisms are added to the methanizer after the addition of the substrate.

[0138] In one or more embodiments, the microorganisms and the substrate are added concomitantly to the methanizer.

[0139] Anaerobic digestion

[0140] The anaerobic digestion step usually takes place under controlled temperature and / or pressure conditions known to those skilled in the art.

[0141] The anaerobic digestion step can for example last from 15 minutes to 30 days, depending on the volume of substrate subjected to digestion and the type of substrate.

[0142] Anaerobic digestion is typically carried out in a digester or methanizer.

[0143] Anaerobic digestion is preferably carried out in the presence of microorganisms well known to those skilled in the art, which are brought into contact with the substrate in the form of an inoculum.

[0144] This inoculum can be in the form of a powder or a liquid.

[0145] The microorganisms used generally comprise at least one methanogenic microorganism.

[0146] In the present invention, the term methanogenic microorganism means a microorganism capable of forming methane. The two main groups of methanogenic microorganisms are methylotrophs and hydrogenotrophs. These two groups are notably involved in the final phase of the biogas production process, where methane and carbon dioxide are formed as end products. Dihydrogen and carbon dioxide are the main substrates used by hydrogenotrophs for the formation of methane, but some can use dihydrogen in combination with methanol. The main groups that use dihydrogen belong to one of the genera chosen from Methanoculleus, Methanobacteriales, Methanobacterium, Methanococcus, Methanogenium and Methanobrevibacter.

[0147] Methylotrophs use acetate, methanol, and other methyl compounds as substrates. A subset of these microorganisms are acetotrophs (also called acetate-eliminating microorganisms) that thrive using acetate as a substrate. Hydrogenotrophic methanogenic microorganisms use hydrogen and carbon dioxide as substrates. They play an important role in keeping hydrogen pressure low so that anaerobic oxidation can continue.

[0148] Methanogenic microorganisms are notably characterized by the presence of a coenzyme F420 responsible for blue-green autofluorescence when the cells are exposed to ultraviolet light at a wavelength of approximately 350-420 nm. Thus, cells or colonies of methanogenic microorganisms can be quickly identified under an epifluorescence microscope.

[0149] To date, all microorganisms known to produce methane via their energy metabolism are classified within the Archaea. In one embodiment, the methanogenic microorganism is a methanogenic Archaea. In one embodiment, the methanogenic archaea is selected from the following archaea: Methanobrevibacter smithii, Methanobrevibacter oralis, Methanosphaera stadtmanae, Methanomassiliicoccus luminyensis, Methanobacterium beijingense and Methanosaeta concilii.

[0150] A typical inoculum comprises methanogenic microorganisms mixed with non-methanogenic microorganisms. In other words, the methanogenic microorganisms represent only a part of the inoculum population, and most often a minority part.

[0151] Thus, the inoculum may comprise non-methanogenic bacteria belonging to the Firmicutes and Bacteroidetes group. Result of the process

[0152] In one or more embodiments, at the end of the biogas preparation process according to the invention, an improvement is obtained consisting of obtaining 10 to 20% more volume of biogas per kg of substrate treated.

[0153] In one or more embodiments, the use of fermented molasses and yeast extract makes it possible to reduce the anaerobic digestion time by 30%, preferably by 50%.

[0154] Thus, for example, when methanization, in particular anaerobic digestion of a substrate such as manure, requires on average 15 to 20 days, the implementation of the method according to the invention makes it possible to reduce the anaerobic digestion time to less than 10 days. 2. Composition for the preparation of biogas

[0155] According to a second aspect, the invention relates to a composition for improving biogas production comprising, in % by dry weight: - between 80% and 99% of fermented molasses, preferably of a fermented molasses as defined in the first aspect of the invention, - between 1% and 20% of a yeast extract, preferably a yeast extract as defined in the first aspect of the invention.

[0156] The composition may advantageously comprise between 80% and 90% of fermented molasses and / or between 10% and 20% of yeast extract.

[0157] The composition may advantageously comprise between 80 and 85% of fermented molasses and / or between 15% and 20% of yeast extract.

[0158] The composition may also advantageously comprise between 85 and 90% of fermented molasses and / or between 10% and 15% of yeast extract.

[0159] A preferred composition comprises 85% fermented molasses and 15% yeast extract.

[0160] In one or more embodiments, the composition comprises: - between 80% and 90% of fermented molasses, the fermented molasses being a mixture of fermented beet molasses and fermented cane molasses, preferably a mixture comprising between 60% and 80% of beet molasses and between 20% and 40% of fermented cane molasses, by dry weight of the mixture; - between 10% and 20% yeast extract.

[0161] In one or more embodiments, the total of the weight percentages of fermented molasses and yeast extract is greater than 90%, preferably 95%, more preferably 98%, more preferably equal to 100%.

[0162] The composition may be in the form of a liquid or a powder.

[0163] In one or more embodiments, the composition has one or more of the characteristics A to F described in Table 1 below: [Tables 1] A MS (%) determined after passage in an oven at 105°C for 15 hours greater than 50%, preferably between 50% and 70%; preferably between 55% and 65%. B pH at 20°C greater than 6, preferably between 6 and 7. C Total nitrogen, % by weight on crude between 1% and 5%, preferably between 3% and 5% D Viscosity 50 mPas.s 1 at 1000 mPas.s 1 at 20°C (20s1) E Ash, % by weight on crude between 15% and 25%, preferably between 18% and 22%. F Organic matter, % by weight on crude between 30% and 50%, preferably between 35 and 45%.

[0164] In some embodiments, the composition has one of the combinations of the features described in Table 1 above: A, B, C, D, E, F, A+B, A+C, A+D, A+E, A+F, B+C, B+D, B+E, B+F, C+D, A+B+C, A+B+D, A+B+E, A+B+F, A +C+D, A+C+E, A+C+F, A+D+E, A+D+F, A+E+F, A+B+C+D, A+B+C+E, A+B+C +F, A+B+D+E, A+B+D+F, A+B+E+F, A+C+D+E, A+C+D+F, A+C+E+F, A+D+E +F, A+B+C+D+E, A+B+C+D+F, A+B+C+E+F, A+B+D+E+F, A+C+D+E+F, B+C +D+E+F, A+B+C+D+E+F.

[0165] 3. Process for preparing a composition for the preparation of biogas

[0166] According to a third aspect, the invention relates to a process for preparing the composition as defined in the second aspect of the invention, said process comprising a step of mixing the fermented molasses with the yeast extract. 4. Uses

[0167] According to a fourth aspect, the invention relates to the use of fermented molasses as defined in the first aspect of the invention or of a composition as defined in the second aspect of the invention or obtained according to the third aspect of the invention, as an additive for the preparation of biogas from a substrate.

[0168] In one or more embodiments, the fermented molasses as defined in the first aspect of the invention or the composition as defined in the second aspect of the invention or obtained according to the third aspect of the invention is used to increase the rate of biogas production.

[0169] In one or more embodiments, the fermented molasses as defined in the first aspect of the invention or the composition as defined in the second aspect of the invention or obtained according to the fourth aspect of the invention is used to increase the yield of the substrate in biogas. Brief description of the figures

[0170] [Fig. 1] represents the isolated cumulative production kinetics of methane per tonne of MB for Product 1 and Product 2.

[0171] [Fig.2] represents the cumulative production of methane as a function of time for the inoculum alone (T) and the inoculum in contact with Product 2 (P2).

[0172] [Fig.3A] represents the results of 5 tests of isolated cumulative production of methane per tonne of MB of the mixture Product 1 + inoculum.

[0173] [Fig.3B] represents the results of 5 tests of isolated cumulative production of methane per tonne of MB of the mixture Product 2 + inoculum.

[0174] [Fig.4A] represents the cumulative production of isolated methane [i.e. gross less that associated with the inoculum alone] per tonne of Raw Material of the Manure + 5% PI (+ inoculum) mixture.

[0175] [Fig.4B] represents the isolated cumulative production [i.e. gross less that associated with the inoculum alone] of methane per tonne of MB of the Manure + 5% P2 + inoculum mixture.

[0176] [Fig.5] represents the cumulative production of methane by the inoculum.

[0177] [Fig.6] represents the production of methane per gram of raw material of the Product 2 with exhausted inoculum.

[0178] [Fig.7] represents the isolated cumulative production [i.e. gross less that associated with [the inoculum alone] of methane from the manure alone modalities, manure with the addition of product P2 at 2%, 5%, 10% and 15% by weight.

[0179] [Fig.8] represents the isolated cumulative production [i.e. gross less that associated with the inoculum alone] of manure with the addition of product P2 at 2%, 5%, 10% and 15% by weight, from which the production share associated with P2 alone has been removed.

[0180] [Fig.9] represents the isolated cumulative production [i.e. gross less that associated with [inoculum alone] of the manure alone modalities, manure with the addition of product P2 at 0.1%, 0.5%, 1% and 2% by weight.

[0181] [Fig.10] represents the isolated cumulative production [i.e. gross less that associated with the inoculum alone] of the modalities manure alone, manure with the addition of product P2 at 0.1%, 0.5%, 1% and 2% by weight, from which the share of production associated with P2 alone has been removed. EXAMPLES Analytical methods

[0182] Measurement of methanogenic potential (BMP for “Biochemical Methane Potential”):

[0183] Definition of parameters

[0184] MB = Raw Material, the product has not undergone any treatment

[0185] MS = Dry Matter, the product was dried to determine the proportion of dry elements here

[0186] MO = Organic Matter, the product has undergone heat treatment in order to define the proportion of organic matter

[0187] M0 / MB= represents the share of Organic Matter in the raw product (MB)

[0188] Description of the BMP test

[0189] The evaluation of the methanogenic potential is carried out in IL bottles and uses the so-called "batch" method (controlled incubation in a bottle). An identical and exact quantity between each sample to be evaluated is introduced into each bottle. The manipulation ends when all of the incorporated product is degraded. Each sample is tested in 5 repetitions in order to increase the representativeness of the values ​​obtained.

[0190] For each test, two types of witnesses are used:

[0191] - The controls, called negative, are the “blanks”, they contain only the inoculum (solution containing the bacteria carrying out the methanization process). Negative controls are used to determine the proportion of biogas production resulting from the residual activity of the inoculum. These values ​​are subtracted from those obtained for the samples tested.

[0192] - The controls, called positive, contain the inoculum and raw glucose powder. Glucose will be completely degraded by the families of microorganisms involved in the methanization process. Positive controls are used to evaluate the biological activity of the inoculum and thus validate the test. In the following examples, a positive control was systematically carried out to verify the activity of the inoculum, validating the test for each example.

[0193] Prior to this test, the sample to be analyzed is characterized in terms of its dry matter (DM) and Organic Matter (OM) in order to be able to adapt the inputs for each sample to the protocol. The objective is to add, whatever the sample, 3 g of OM in each bottle coming from the substrate to be tested.

[0194] The samples tested can be in 3 forms: fresh crude, dry crude, ground freeze-dried. The choice of one of these 3 forms will depend on the requirements of the applicants for the analysis. Each form has advantages and disadvantages in terms of ease of preparation or representativeness. In the examples below, the samples tested are in the fresh crude form.

[0195] Method of preparing the BMP test: - Weigh the mass of sample required for an addition of 3 g of OM from the latter. To do this, it is necessary to take into account the characteristics of the test sample (MS, OM) and also the form of the latter (fresh raw, dry raw, ground freeze-dried); - Complete with water so that the mass of raw sample + water represents 50 g; - Add 700 g of inoculum, previously homogenized in the storage container and stir with a magnetic stirrer; - Carry out the initial pH measurement; - Close the bottle with the septum and the screw cap; - Place in an oven at 37.5°C; - Note the start time of the manipulation when all the bottles in a series of manipulations are launched.

[0196] Measurements of biogas production, methane, are carried out regularly.

[0197] Method for measuring biogas production: - Remove the bottles from the oven in batches of 10 maximum; - Shake the bottle before measuring for 30 seconds, making a gesture describing a zero; - Using the needle, prick the septum, taking care to keep the prick hole as far away from the previous ones as possible; - Record the volume of biogas produced on the Ritter drum meter as well as the percentage of methane and CO2 displayed on the infrared sensors; - Repeat the operation for each bottle; - When the series of 10 bottles is measured, place them back in their oven at 37.5°C.

[0198] The test ends approximately 30 days after its launch when the cumulative production of biogas linked to the degradation of the tested substrate is almost zero.

[0199] The final pH is measured for each bottle to ensure that the medium has not undergone acidosis.

[0200] EXAMPLE 1: Comparison of methane production with products P 1 (fermented molasses alone) and P 2 (fermented molasses mixed with yeast extract) alone or with manure

[0201] 1.1.: Study of methane production with PI and P2 alone

[0202] MATERIALS AND METHODS

[0203] Two products tested: product 1 (PI) and product 2 (P2), identical in all examples.

[0204] Product (PI): 100% fermented beet and cane molasses in a 90 / 10 ratio

[0205] Product 2 (P2): mixture of fermented beet and cane molasses in a 90 / 10 ratio with downgraded yeast extracts in a 85 / 15 w / w dry ratio (fermented molasses / yeast extract).

[0206] The inoculum used comes from sewage treatment plant sludge. The same inoculum origin is used in the other examples.

[0207] Table 2 shows the MS and MO / MB contents for the 2 products tested. The MS content differs slightly with a higher proportion of water contained in product 1 compared to product 2. On the other hand, the proportion of Organic Matter in the Raw Matter is close for the 2 samples. [Tables 2] Product 1 100% Fermented Molasses Product 2 85% Fermented Molasses +15% EXL (dry weight) MS (%) 59.6 64.4 MO / MB (%) 34.0 36.9 Sample mass for 3 g of MO 8.8 g 8.1 g Table 2: Composition of products 1 and 2

[0208] The BMP method described above is applied for this study on the catalytic effect of the products PI and P2.

[0209] RESULTS

[0210] [Fig.l] presents the isolated cumulative methane (CH4) production kinetics [i.e. gross minus that associated with Tinoculum alone; abbreviated Cumulative methane production in [Fig.l]] per tonne of MB for the 2 products tested: Product 1 and Product 2.

[0211] Line T corresponds to the measurements of the negative control T.

[0212] This kinetics is particular since a production peak is observed on the 10th day of the experiment. This extremum is in reality linked to very different degradation kinetics between the inoculum alone (T) and the inoculum in contact with the tested product (PI or P2).

[0213] To understand this artifact, we must return to the method of estimating cumulative volume.

[0214] In [Fig.2] is presented the gross cumulative production of CH4 as a function of time for the inoculum alone (T) and the inoculum in contact with Product 2.

[0215] The inoculum, which contains the bacteria necessary for the anaerobic digestion of the substrate to be tested, always has a residual production of biogas linked to the presence of residual organic matter. In order to isolate the actual methane production of the substrate, the residual methane production of the inoculum alone is subtracted from the methane production of the inoculum + substrate.

[0216] This mathematical operation can be visually represented by the difference between the two curves ([Fig.2]). We then note that the maximum obtained on the 10th day (i.e. 240 h), actually corresponds to the stagnation of biogas production (plateau) due to the consumption of all the organic matter available in the inoculum and Product 2. At this precise moment, the difference between the two curves is maximum. For the rest of the experiment, the difference will be reduced due to the residual biogas production of the inoculum alone.

[0217] For most of the BMP analyses carried out by the Methanization platform, we observe identical degradation kinetics between the residual organic matter of the inoculum and that of the added substrate. The subtraction method is in these cases entirely suitable for quantifying the BMP of the analyzed substrate.

[0218] In view of the above, it is clear that product 1 and product 2 have, in addition to their respective own methanogenic power, a very marked “catalyst” effect.

[0219] Indeed, the cessation of methane production with the product P2 is achieved in only 10 days instead of a duration of more than 30 days in the case of the control with regard to the curve ([Fig.2]).

[0220] The final BMP values ​​of the PI and P2 products are 56 and 76 m3 CH4 / T MB respectively.

[0221] 1.2. Study of the reproducibility of methane production with PI and P2

[0222] 1.2.1. Effectiveness of PI and P2 products in contact with the inoculum alone

[0223] MATERIALS AND METHODS

[0224] The methane production of Product 1 (3g of MO) or Product 2 (3g of MO) with the inoculum alone is tested.

[0225] The BMP method described above is applied for this reproducibility study.

[0226] RESULTS

[0227] The results are presented in [Fig.3A] and [Fig.3B].

[0228] A greater disparity in the results obtained with the product PI is observed compared to the product P2.

[0229] Thus, the additivation of PI with a yeast extract (= P2) allows for better homogeneity of results and optimized biogas production.

[0230] 1.2.2 . Effectiveness of PI or P2 products in contact with inoculum and manure

[0231] MATERIALS AND METHODS

[0232] The reproducibility of methane production with F + 5%P1 and F + 5%P2 is tested.

[0233] The BMP method described above is applied for this study on the reproducibility.

[0234] RESULTS

[0235] The results are presented in [Fig.4A] and [Fig.4B].

[0236] The results show that the PI product and the P2 product allow satisfactory reproducibility of biogas production. However, it is noted that the results obtained with the P2 product show fewer disparities than those obtained with the PL product. The P2 product allows better predictability of biogas production on manure.

[0237] EXAMPLE 2: Manure with P2 additive at percentages of 2%, 5%, 10%, 15%.

[0238] Products tested: product 2 (P2), manure (F), manure with P2 additive at percentages 2 %, 5%, 10%, 15%.

[0239] Product 2 (P2): mixture of fermented beet and cane molasses / declassified yeast extracts 85 / 15% w / w dry.

[0240] Objective of Example 2: To overcome the effect of the tested products (PI and P2) on the residual organic matter of the inoculum used in the BMP tests. To do this, the inoculum is first exhausted for a period of 30 days. 2.1. Depletion of the inoculum

[0241] The main purpose of depleting the inoculum is to reduce its residual fermentable organic matter. This reduction can be achieved by leaving the inoculum in an open container in a ventilated area and shaking it from time to time to facilitate the release of the biogas produced.

[0242] From an experimental point of view, the inoculum was depleted over a month under the same conditions as the negative controls: 700 g of inoculum placed in a hermetic bottle and degassed regularly. This depleted inoculum will be used in all the modalities tested. The result of this depletion is presented in [Fig.5].

[0243] The fresh inoculum has a production of 950 mL of methane per 700 g, i.e. a methanogenic potential of 1.36 m3 CH4 / T MB. 2.2. BMP of product 2 with exhausted inoculum

[0244] The BMP of product 2 was reestimated based on a depleted inoculum by applying the BMP method described above.

[0245] The associated biogas production is presented in [Fig.6].

[0246] The BMP of product P2 is reached in 11 days.

[0247] The final value of the BMP of the product P2 is estimated at 125 m3 CH4 / T MB.

[0248] 2.3. BMP of manures supplemented with P 2 with exhausted inoculum.

[0249] MATERIALS AND METHODS

[0250] The BMPs of manure alone compared to manure with the addition of product P2 at 2%, 5%, 10% and 15% by mass were observed.

[0251] RESULTS

[0252] The results are presented in [Fig.7].

[0253] The final BMP values ​​are between 40 and 60 m3 CH4 / T MB. Generally speaking, the addition of P2 to manure increases its methanogenic power. However, a negative effect is noted in the case of the 15% method where the BMP is lower than the other methods.

[0254] From a kinetic point of view, as the inoculum is previously exhausted, its activity is reduced throughout the exhaustion due to lack of substrate. For manure in particular, a period of 4 or 5 days is observed for the inoculum to resume normal activity. On the other hand, for manure with additives, the higher the P2 incorporation rate, the faster the resumption of activity.

[0255] The product P2 has an interesting methanogenic power, three times higher than that of manure. The addition of P2 to the manure makes it possible to increase the average BMP of the mixture. In order to characterize the effect of P2 on the BMP of the manure, it is necessary to remove from the BMP of [Fig.7] the share of the BMP of P2 alone. The following formula is applied to characterize the overall BMP when adding P2 at different dosages:

[0256] [Math.l] ver \ {bmp^-x^bmpp^ BMrFunder{aaditive a X%) =------------

[0257] The corresponding curves are presented in [Fig.8].

[0258] The resulting kinetics show that the differences in kinetics observed in [Fig.7] are only due to the rapid degradation of P2. The more P2 there is, the faster and greater the initial production of biogas. However, there is no effect on the degradation kinetics of the manure itself. At 40 days, the production of biogas is residual for manure alone, unlike for manure with additives where the production of biogas is on a moderate dynamic.

[0259] The addition of P2 to manure makes it possible to obtain higher BMP values ​​up to 25%. This effect is visible and similar for contents between 2% and 10%. Beyond that, from 15% by mass, an inhibition effect is visible and the final BMP is equivalent to that of manure alone. 2.4. Conclusion

[0260] The remarkable feature of the P2 product is the rapid degradation of organic matter in 11 days, in particular a notable effect on the starting kinetics of the BMP of the manure with an additive of 2 to 15% demonstrating a kinetics accelerating effect.

[0261] Its addition to manure makes it possible to increase the methanogenic potential of the manure by up to 25% from an addition of 2% by mass and up to 10% by mass.

[0262] The use of product P2 as an additive in this mass content range (2 - 10%) does not show any sign of notable inhibition.

[0263] Product P2 is therefore a promising additive that can increase biogas production by 25%.

[0264] EXAMPLE 3: Manure with P2 additive at percentages of 0.1%, 0.5%, 1%, and 2%.

[0265] Products tested: product 2 (P2), manure (F), manure with P2 additive at percentages of 0.1%, 0.5%, 1%, 2%.

[0266] Objective of Example 3: Test the effect of product 2 (P2) as an additive to manure in low proportions: 0.1%, 0.5%, 1% and 2% by mass.

[0267] MATERIALS AND METHODS

[0268] The BMPs of manure alone compared to manure with the addition of product P2 at 0.1%, 0.5%, 1% and 2% by mass were compared.

[0269] The BMP method described above is applied.

[0270] RESULTS

[0271] The results are presented in [Fig.9],

[0272] The BMPs are between 9.8 and 21.9 m3 CH4 / TMB. These values ​​are relatively low since cattle manure generally has a BMP between 25 and 40 m3 CH4 / TMB. The manure used, although harvested fresh on the day the experiment was launched, does not exhibit normal behavior. From a kinetic point of view, there is a gap in the start of production between the manure alone and the manures with additives.

[0273] The addition of P2 to manure increases its methanogenic power, even from 0.1% addition. On the other hand, few differences are visible between the 4 additive methods.

[0274] The measured BMP of the P2 product in this test is 65.3 m3 / T MB. This potential is much higher than that of the manure. Thus, the addition of P2 to the manure will increase the average BMP of the mixture. In order to characterize the effect of P2 on the BMP of the manure, it is necessary to remove from the BMP of [Fig.9] the part of the BMP due to the addition of P2. Since the modalities were launched at the same time, it is possible to apply the following formula:

[0275] [Math.l] ( ..... vcfX (BMP^^BMP^ BMI*Funüer(additive to X%) =------------

[0276] The corresponding curves are presented in [Fig. 10].

[0277] [Fig. 10] shows a notable difference between the production of manure alone and manure with additives.

[0278] Unlike [Fig.9] where this difference could be linked to the methanogenic potential of product 2, this graph demonstrates the positive effect of P2 on the degradation of manure throughout the kinetics and this with low quantities of P2.

[0279] The various proportions tested (0.1%, 0.5%, 1% and 2%) have a similar effect on methane production, with close values ​​between 18.7 and 21.7 m3 / T MB.

[0280] The faster start-up speed seen in [Fig.9] is still visible in this graph. Additive manures produce methane more quickly than manure alone.

[0281] EXAMPLE 4: Study of combinations of fermented molasses + EXL as an additive on manure for the production of biogas.

[0282] Objective of the study

[0283] The objective of this test is to evaluate the methanogenic potential of different products comprising a fermented SIL molasses (90 / 10 beet / cane) and a yeast extract in the form of granules, paste or powder.

[0284] MATERIALS AND METHODS

[0285] Molasses: fermented molasses SIL (90 / 10 beet / cane).

[0286] Yeast extracts: yeast extract granules (EXL MG-L), yeast extract paste (EXL paste), or yeast extract powder (EL powder).

[0287] RESULTS

[0288] Table

[0289] The results are presented in Table 3. [Tables 3] Product Methanogenic potential (m3 / T MB) Additives (at 2% on dry w / w manure) M3 CH4 / T MB Manure + VO2_1 (2%) V02_l: 95% SIL + 5% EXL granules MG-L 45.63 Manure + VO2_2 (2%) VO2_2: 90% SIL + 10% EXL granules MG-L 44.90 Manure + VO2_3 (2%) VO2_3: 85% SIL +15% EXL granules MG-L 44.41 Manure + VO2_D (2%) VO2_D: 90% SIL + 10% EXL powder PW 43.19 Manure + VO2_P (2%) VO2_P: 90% SIL + 10% EXL paste 40.81 Manure alone 34.87

[0290] Conclusion

[0291] In conclusion, the form of TEXL incorporated into fermented molasses (Granule, powder or paste) does not lead to a significant variation in the quantity of biomethane produced. The paste, less rich in EXT, may possibly limit the production of biogas.

[0292] A quantity of 5%, 10% or 15% of yeast extract on dry weight of fermented molasses does not lead to a significant variation in the production of biomethane.

[0293] Thus, the increase in methane production is ensured by the supply of fermented molasses, and the stability of production can be improved by the supply of EXL.

Claims

Claims

1. Process for preparing biogas from a substrate characterized in that it comprises a step of anaerobic digestion of said substrate in the presence of fermented molasses, the content of fermented molasses being between 0.01% and 15% by weight of substrate.

2. The method of claim 1, wherein the fermented molasses is fermented beet molasses, fermented cane molasses, or a mixture thereof.

3. A method according to any one of claims 1 or 2, wherein the fermented molasses comprises at least 60% by weight of fermented beet molasses.

4. A method according to any one of claims 1 to 3, wherein the fermented molasses content is between 0.01% and 5%, preferably between 0.05% and 2%, by weight of substrate.

5. A method according to any one of claims 1 to 4, wherein the anaerobic digestion step is carried out in the presence of yeast extract, the total content of fermented molasses and yeast extract being in particular between 0.01% and 15% by weight of substrate.

6. Method according to claim 5 in which the dry weight ratio of fermented molasses: yeast extract is between 80:20 and 99:1, preferably between 85:15 and 99:

1.

7. A method according to any one of claims 5 or 6, wherein the fermented molasses and the yeast extract are added simultaneously or separately to the substrate.

8. Composition for improving biogas production comprising, in % by dry weight: - between 80% and 99% of fermented molasses, - between 1% and 20% of yeast extract.

9. A composition according to the preceding claim, wherein the fermented molasses is fermented beet molasses, fermented cane molasses, or a mixture thereof.

10. A composition according to any one of claims 8 or 9, wherein the fermented molasses comprises at least 60% by weight of fermented beet molasses.

11. A process for preparing the composition as defined in claims 8 or 9 comprising a step of mixing fermented molasses and yeast extract.

12. Use of fermented molasses or a composition as defined in claims 8 to 10 as an additive in a process for preparing biogas from a substrate, characterized in that it comprises a step of anaerobic digestion of said substrate in the presence of fermented molasses, the content of fermented molasses being between 0.01% and 15% by weight of substrate.

13. Use according to claim 12, for increasing the rate of biogas production.

14. Use according to any one of claims 12 or 13, for increasing the yield of the biogas substrate.

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