PROCESS FOR QUANTIFYING THE PYROGENIC CARBON PRESENT IN A SAMPLE OF AN ORGANOMINERAL OR MINERAL MATRIX CONTAINING COAL AND / OR BIOCHAR

Abstract

The present invention relates to a method for quantifying the pyrogenic carbon content of a sample comprising an organo-mineral or mineral matrix as well as charcoal and / or biochar. The method comprises heating the sample in an inert atmosphere and then heating the residue from the heating in an inert atmosphere in an oxidising atmosphere. A Gaussian deconvolution is then applied to the measurement curve of the amount of CO2 released as a function of the temperature during the heating in an oxidising atmosphere, and first and second Gaussian deconvolutions are determined which are centred respectively on a first temperature between 380°C and 540°C, preferably between 415°C and 425°C, and very preferably equal to 420°C, and a second temperature between 500°C and 600°C, preferably between 570°C and 580°C, and preferably equal to 576°C. The pyrogenic carbon content is determined from the surfaces of the first and second Gaussian deconvolutions.

Description

1 / 28 “PROCESS FOR QUANTIFYING THE PYROGENIC CARBON PRESENT IN A SAMPLE OF AN ORGANOMINERAL OR MINERAL MATRIX CONTAINING COAL AND / OR BIOCHAR” Technical field

[0001] The present invention relates particularly to the field of soil science, agronomy and the environment, and more generally to any field involving the quantification of biochar and / or charcoal present in a mineral or organomineral matrix.

[0002] The present invention may be related, for example, to the field of biochar production and marketing, especially when biochar is marketed in the form of a mixture with an organomineral or mineral matrix to, for example, be used as organic fertilizer (biochar-sediment) or as a building material for buildings, similar to hybrid green concrete (biochar-calcium carbonate) or simply by mixing biochar with concrete (mineral matrix).

[0003] In the environmental field, to overcome environmental challenges and particularly to limit global warming to 1.5°C relative to the pre-industrial period, the goal of "Net Zero Emissions" must be achieved by 2050. To this end, drastically reducing CO2 emissions is insufficient; negative emission technologies must be developed. Biochar, a product of biomass pyrolysis, is a negative emission technology because it is a carbon-rich and biologically stable material. Furthermore, in recent decades, pyrogenic organic matter has been recognized as an important component of the extremely fertile soils of the Amazon. Indeed, this material can have beneficial effects on soil fertility, particularly for water and nutrient retention and liming effects. The name given to pyrolyzed organic matter differs depending on its end use. The term "biochar" indicates that the organic matter has been Petition 870250083238, dated 09 / 16 / 2025, p. 7 / 48 2 / 28 pyrolyzed with the aim of correcting and improving soil properties. In the literature, carbon black describes the volatile components resulting from the incomplete combustion of biomass. In some studies, the term "black carbon" is also used to describe a wider range of material, forming a continuum that ranges from charcoal to soot. The term "char" indicates that the organic matter has been intentionally pyrolyzed, for example, for its use as fuel or filter. Note that charcoal differs from geological coal in its production method and its chemical and physical properties, which are very distinct.Unlike coal from biomass pyrolysis, geological coal (e.g., bituminous coal) is produced by geological processes at high pressure and high temperature, over a longer timescale (several thousand years). Geological coal specifically does not contain pyrogenic carbon. Thus, other forms of coal besides geological coal (i.e., charcoal, coal, or biochar) may be present in the soil due to numerous contexts, including vegetation fires and intentional fertilization to improve soil properties. Since coal is rich in biologically stable carbon (i.e., aromatic compounds), its quantification can be carried out through pyrogenic carbon, its main component. The interests in quantifying pyrogenic carbon in the soil are varied and depend on the context in which it is introduced. In the case of fires, the pyrogenic carbon content is a marker of the frequency of fires.This marker is particularly useful for archaeological studies, as a high frequency of fires in the same location may indicate previous human occupation, while lower intensities are due to natural fires. When fertilization is done with biochar, carbon quantification is crucial. Petition 870250083238, dated 09 / 16 / 2025, page 8 / 48 Quantifying pyrogenic carbon in a corrected plot allows monitoring of the remaining biochar content in the soil. In fact, biochar could easily be subject to physical degradation. Furthermore, quantifying pyrogenic carbon outside the corrected plot allows monitoring of the future biochar in the environment, especially in its storage areas. State of the art

[0004] The following documents will be mentioned throughout the description:

[0005] Arroyo-Kalin, M. A. (2008). Steps towards an ecology of landscape: A geoarchaeological approach to the study of anthropogenic dark earths in the central Amazon region, Brazil (Dissertação de doutorado, Universidade de Cambridge).

[0006] Aubertin, M. L. (2022). Biochar-compost mixtures: interactions and impact on carbon sequestration and soil fertility (Dissertação de doutorado, Universidade de Sorbonne).

[0007] Behar, F., Beaumont, V., & Penteado, H. D. B. (2001). RockEval 6 technology: performances and developments. Oil & Gas Science and Technology, 56(2), 111-134.

[0008] Chalk, P., & Smith, C. J. (2022). 13C methodologies for quantifying biochar stability in soil: A critique. European Journal of Soil Science, 73(3), e13245.

[0009] Cuypers, C., Grotenhuis, T., Nierop, K. G., Franco, E. M., de Jager, A., & Rulkens, W. (2002). Amorphous and condensed organic matter domains: the effect of persulfate oxidation on the composition of soil / sediment organic matter. Chemosphere, 48(9), 919-931.

[0010] Glaser, B., Haumaier, L., Guggenberger, G., & Zech, W. (1998). Black carbon in soils: the use of benzenocarboxilic acids as specific markers. Organic geochemistry, 29(4), 811-819.

[0011] Llorente, M., Turrión, M. B., & Glaser, B. (2018). Rapid and economical quantification of black carbon in soils using a modified Petição 870250083238, de 16 / 09 / 2025, pág. 9 / 48 4 / 28 benzene polycarboxylic acids (BPCA) method. Organic Geochemistry, 115, 197-204.

[0012] Paterson, G. A., & Heslop, D. (2015). New methods for unmixing sediment grain size data. Geochemistry, Geophysics, Geosystems, 16(12), 4494-4506.

[0013] Poot, A., Quik, J. T., Veld, H., & Koelmans, A. A. (2009). Quantification methods of Black Carbon: Comparison of Rock-Eval analysis with traditional methods. Journal of Chromatography A, 1216(3), 613-622.

[0014] Sebag, D., Disnar, J. R., Guillet, B., Di Giovanni, C., Verrecchia, E. P., & Durand, A. (2006). Monitoring organic matter dynamics in soil profiles by Rock-Eval pyrolysis’: bulk characterization and quantification of degradation. European journal of soil science, 57(3), 344-355.

[0015] Sebag, D., Garcin, Y., Adatte, T., Deschamps, P., Ménot, G., & Verrecchia, E. P. (2018). Correction for the siderite effect on RockEval parameters: application to the sediments of Lake Barombi (southwest Cameroon). Organic Geochemistry, 123, 126-135.

[0016] Simpson, M. J., & Hatcher, P. G. (2004). Overestimates of black carbon in soils and sediments. Naturwissenschaften, 91(9), 436440.

[0017] The various known techniques make it possible to quantify pyrogenic carbon in soil or in a sedimentary material based on chemical, magnetic, optical or thermal differences between the soil and the coal or by the presence of molecular markers.

[0018] A common technique involves quantification by extraction of polycarboxylic acids from benzene (BPCA) followed by chemical oxidation of aromatic structures, by gas chromatography analysis, as described, for example, in the document (Glaser et al., 1998), or by elemental analysis, as described, for example, in the document (Llorente et al. 2018). However, extraction is time-consuming and can Petition 870250083238, dated 09 / 16 / 2025, page 10 / 48 5 / 28 adding a bias to the quantification of BPCA.

[0019] The use of natural carbon isotope is a direct, accurate, and reproducible quantification process that allows distinguishing the source of carbon from a mixture of two carbon-based components with significantly different isotopic signatures (δ13C), as described, for example, in the document (Aubertin et al., 2022). However, isotopic analysis can only be applied in the case of a coal-soil mixture, where the two components have significantly different isotopic signatures. Isotopic enrichment processes can also be applied to quantify pyrogenic carbon, but this involves (time-consuming) incubation, and the results may be biased by the non-uniform distribution of the labeled carbon added to the plant, as described, for example, in the document (Chalk and Smith, 2022).

[0020] Other processes for quantifying coal are based on observing differences in the color or density of coal particles from a microscopic photograph, as described, for example, in the document (Arroyo-Kalin, 2008). However, these processes are time-consuming (slip preparation time and sample handling), only take into account particles above a certain diameter, are not very reproducible because they depend on the handler, and only arrive at an approximate coal mass from counting a surface.

[0021] Among thermal processes, the thermochemical oxidation process involves a chemical oxidation pretreatment with acid to remove inorganic carbon followed by the separation of pyrogenic and non-pyrogenic carbon through combustion at temperatures around 350°C for at least 2 hours, followed by analysis of the residual carbon by 13C NMR or elemental analysis, as described, for example, in the document (Poot et al. 2009). Add to this the slowness Petition 870250083238, dated 09 / 16 / 2025, page 11 / 48 6 / 28 of this process, the possibility of inducing overestimations of pyrogenic carbon due to the formation of pyrogenic carbon during the combustion phase, as described, for example, in the document (Simpson and Hatcher, 2004). Thermogravimetric analysis measures several emission peaks during heating, but with this process it is difficult to differentiate the peaks of emissions linked to pyrogenic carbon and to soil components, as described, for example, in the document (Cuypers et al., 2002). One process for quantifying pyrogenic carbon in soil is the differential scanning calorimetry technique, known by the acronym DSC (“Differential Scanning Calorimetry”), in which the sample causes changes in heat flux as a function of the temperature gradient. It is possible to establish a close correlation between variations in heat flux and carbon content.To quantify pyrogenic carbon, it is sufficient to calculate the difference between the carbon content above the limit temperature, around 400°C, of ​​a sample of the same soil / sediment with and without carbon. However, DSC is an indirect measurement of stable carbon in a sample, which can make carbon quantification inaccurate.

[0022] Thus, despite its obvious interest, the quantification of pyrogenic carbon in soil is often difficult to perform, and the different existing techniques have disadvantages due, for example, to their cost, analysis time, precision or inconsistency of reproducibility.

[0023] There are also known processes for thermal analysis of soil organic matter based on measuring the amount of hydrocarbon compounds (HC), carbon monoxide (CO), and / or carbon dioxide (CO2) released over time by a sample subjected to a sequence of temperatures in an inert atmosphere (pyrolysis phase) followed by / or a sequence of temperatures in an oxidizing atmosphere (oxidation phase). These processes were developed Petition 870250083238, dated 09 / 16 / 2025, page 12 / 48 7 / 28 initially in the petroleum industry for the purpose of characterizing the organic fraction of sedimentary rocks. The process known as ROCK-EVAL® BULK ROCK, for example, was initially developed for conventional matrix rock samples and differentiates pyrolyzed organic carbon from refractory organic carbon (Behar et al., 2001). The document (Poot et al., 2009) describes that the refractory carbon content measured during this thermal analysis can be used to approximately quantify the pyrogenic carbon in a soil or sediment sample. More precisely, the document describes that the ROCK-EVAL® BULK ROCK process allows for the easy and rapid separation of pyrolyzable carbon (PC) from residual carbon (RC). RC corresponds to refractory organic carbon, originating from organic matter that is thermally resistant to the pyrolysis phase and is oxidized during the oxidation phase.This document then proposes the idea of ​​approximating RC as a measure of pyrogenic carbon, which it calls "black carbon," and which it defines as a continuum ranging from pyrolyzed biomass charcoal to soot. However, this latter variant remains imprecise, as RC can also be partially produced during the pyrolysis phase. Thus, the pyrogenic carbon analyzed by this process may be slightly overestimated.

[0024] The present invention makes it possible to correct these disadvantages. Specifically, the present invention allows for the rapid and precise quantification of pyrogenic carbon in a sample of an organomineral or mineral matrix, such as soil, through thermal analysis, which particularly includes the analysis of carbon emissions during an oxidation phase of the sample. Summary of the invention

[0025] The present invention relates to a process for quantifying the pyrogenic carbon content present in a sample containing Petition 870250083238, dated 09 / 16 / 2025, page 13 / 48 8 / 28 an organomineral or mineral matrix, as well as coal and / or biochar. The process according to the invention comprises at least the following steps:

[0026] A) heat the sample in an inert atmosphere following a first sequence of temperatures, where the initial temperature (T0) is between 100 and 300°C, preferably 200°C, and the final temperature (TF) is between 500 and 800°C, preferably 650°C;

[0027] B) heating in an oxidizing atmosphere a residue of said sample resulting from said heating in an inert atmosphere following a second sequence of temperatures, whose initial temperature (T0') is between 100 and 300°C, preferably 200°C, and a final temperature (TF') is between 700 and 1000°C, preferably 850°C, said second sequence of temperatures comprising at least a thermal gradient between 1°C and 50°C / min, preferably between 15°C / min and 35°C / min, even more preferably 25°C / min, and at least a quantity of CO2 (QCO2) released during said second sequence of temperatures;

[0028] C) from a representative curve of the evolution as a function of temperature of the said quantity of CO2 released during the said heating in an oxidizing atmosphere, apply a Gaussian deconvolution to the said curve, in order to determine a first and a second Gaussian curve centered, respectively, at a first and a second temperature, wherein the said first temperature is between 380°C and 540°C, preferably between 415°C and 425°C, more preferably 420°C, and the said second temperature is between 500 and 600°C, preferably between 570 and 580°C, and more preferably 576°C;

[0029] D) From the surfaces of the aforementioned first and second Gaussians, determine the aforementioned pyrogenic carbon content. Petition 870250083238, dated 09 / 16 / 2025, p. 14 / 48 9 / 28 X3 present in the aforementioned sample using a formula of the type: _ X2-A.X131+AB

[0030] where X± and X2 are the carbon contents determined, respectively, from the surfaces of the aforementioned first and second Gaussian surfaces, A is a coefficient representing the proportion of the aforementioned matrix in the aforementioned second Gaussian surface in relation to the aforementioned first Gaussian surface, and B is a coefficient representing the proportion of the aforementioned coal and / or the aforementioned biochar in the aforementioned first Gaussian surface in relation to the aforementioned second Gaussian surface.

[0031] According to one embodiment of the invention, said first temperature sequence may include an isothermal stage of predetermined duration at said initial temperature (T0) of said first temperature sequence, followed by a thermal gradient to reach said final temperature (TF) of said first temperature sequence, said predetermined duration of said isothermal stage of said first temperature sequence may be between 1 and 5 minutes, and preferably may be 3 minutes, and said thermal gradient of said first temperature sequence may be between 1 and 50°C / min, preferably between 15°C / min and 35°C / min, and more preferably may be 25°C / min.

[0032] According to one embodiment of the invention, said second temperature sequence may additionally include an isothermal stage of predetermined duration at a temperature between 500 and 600°C, preferably between 570 and 580°C, and preferably 576°C, said predetermined duration of said isothermal stage of said second temperature sequence may be between 1 and 5 minutes, and preferably may be 3 minutes.

[0033] According to one embodiment of the invention, a sample of said organomineral or pure mineral matrix may also be available, and the said coefficient A of the step may be determined in advance. Petition 870250083238, dated 09 / 16 / 2025, p. 15 / 48 10 / 28 D) as follows: steps A) to C) are applied to the aforementioned sample of the aforementioned organomineral or pure mineral matrix, and the coefficient A is determined by calculating the ratio between the surface of a second Gaussian and the surface of a first Gaussian determined from the aforementioned sample of the aforementioned organomineral or pure mineral matrix.

[0034] According to one embodiment of the invention, a sample of said biochar and / or pure coal can also be used, and the said coefficient B of step D) can be determined in advance as follows: steps A) to C) are applied to said sample of said biochar and / or coal, and the coefficient B is determined by calculating the ratio between the surface of said first Gaussian and the surface of said second Gaussian determined from said sample of biochar and / or pure coal.

[0035] According to one embodiment of the invention, step D) can be applied by means of a coefficient A between a value of 0.17 and a value of 0.73, preferably 0.19, and / or by means of a coefficient B between a value of 0.10 and a value of 4.98, preferably 0.32.

[0036] According to one embodiment of the invention, a total mass of pyrogenic carbon Qc,bc_mix present in said sample can be determined using a formula of the type: Qc, bcjnix = X3 / C * K, where C is a ratio between the carbon content determined from a second Gaussian surface determined for a sample of biochar and / or pure coal, and a total mass of carbon in said sample of biochar and / or pure coal, where is a multiplying coefficient between 12.0 and 12.5, preferably 12.2.

[0037] Alternatively, a total mass of pyrogenic carbon Qc, bcjnix present in the sample can be determined using a formula of the type: Qc, bcjnix = X3 / C * K, where C is a ratio Petition 870250083238, dated 09 / 16 / 2025, page 16 / 48 11 / 28 is between a value of 0.51 and a value of 1.76, preferably 1.06, and K is a multiplier coefficient between 12.0 and 12.5, preferably 12.2.

[0038] Other features and advantages of the process according to the invention will be perceived after reading the description below, which provides non-limiting examples of embodiment and refers to the attached Figures described below. List of Figures

[0039] Figure 1A schematically illustrates the evolution of temperature as a function of time of the temperature sequence of the first stage of the process according to the invention.

[0040] Figure 1B schematically illustrates the evolution of temperature as a function of time for a variant of the temperature sequence of the first stage of the process according to the invention.

[0041] Figure 2 shows, in an application example, the curve of CO2 measured during step 2) of the process according to the invention, as well as the first and second Gaussians resulting from the Gaussian deconvolution according to step 3) of the process according to the invention.

[0042] Figure 3 schematically shows the portion of the organomineral or mineral matrix and the portion of biochar and / or charcoal in the first Gaussian resulting from Gaussian deconvolution according to step 3) of the process according to the invention, as well as the portion of biochar and / or charcoal and the portion of the organomineral or mineral matrix in the second Gaussian resulting from Gaussian deconvolution according to step 3) of the process according to the invention. Description of the modalities

[0043] The invention relates to a process for quantifying the pyrogenic carbon present in a sample containing an organomineral or mineral matrix, as well as coal and / or biochar. Petition 870250083238, dated 09 / 16 / 2025, page 17 / 48 12 / 28

[0044] Pyrogenic carbon is understood to be the organic fraction that has undergone pyrolysis, that is, it has been affected by fire and / or heat (temperature > 200°C) in the absence or low concentration of oxygen.

[0045] By organomineral or mineral matrix, we mean an unconsolidated, porous material formed by a mixture of organic and / or mineral particles, of varying size and chemical and / or mineralogical composition.

[0046] Charcoal is understood to be the solid residue of a chemical transformation under the effect of an increase in temperature, resulting from the pyrolysis or incomplete combustion of plant or animal biomass.

[0047] Biochar is understood to be charcoal produced for use as an organic fertilizer, in particular to improve the physical-chemical properties of the soil or its carbon storage.

[0048] The process according to the invention requires having at least one sample containing an organomineral or mineral matrix, as well as charcoal and / or biochar.

[0049] According to one embodiment of the invention, the sample containing an organomineral or mineral matrix, as well as coal and / or biochar, may be a soil sample containing coal and / or biochar. By soil, it is understood the set of outer layers of the earth's surface formations. A soil sample may be collected manually from a trench or by digging the soil with an auger.

[0050] According to one embodiment of the invention, the sample containing an organomineral or mineral matrix, as well as charcoal and / or biochar, can be a fertilizer sample containing an organomineral or mineral matrix, as well as charcoal and / or biochar.

[0051] According to one embodiment of the invention, the sample containing an organomineral or mineral matrix, as well as coal and / or biochar, may be a soil sample, a sediment sample Petition 870250083238, dated 09 / 16 / 2025, p. 18 / 48 13 / 28 natural or polluted by burning residues, or a sample of mineral materials (concrete, excavated earth, sediments) mixed with coal / biochar. The soil may be agricultural soil or an anthrosol voluntarily enriched with biochar.

[0052] Advantageously, the sample can be sieved with a sieve with 2 mm diameter holes, dried at a temperature below 40°C, and ground until fragments smaller than 200 µm are obtained.

[0053] Preferably, a sample of the aforementioned organomineral or pure mineral matrix may also be available, i.e., free of biochar and coal.

[0054] Advantageously, a sample of biochar and / or charcoal present in the sample under consideration can also be used.

[0055] The process according to the invention can be implemented, advantageously and not limited to, by means of the ROCK-EVAL® device (IFP Energies nouvelles, France), as described in patents FR 2227797 (US 3953171) and FR 2472754 (US 4352673). In fact, the ROCK-EVAL® device comprises at least:

[0056] - a pyrolysis furnace in a non-oxidizing atmosphere,

[0057] - means for transferring pyrolysis waste to an oxidation furnace,

[0058] - an oxidation furnace in an oxidizing atmosphere,

[0059] - means for measuring the amount of hydrocarbon compounds (HC) released during pyrolysis,

[0060] - means for measuring carbon monoxide (CO) and carbon dioxide (CO2).

[0061] The process can also be implemented with a single pyrolysis furnace, which can operate in a non-oxidizing atmosphere and in an oxidizing atmosphere, in cooperation with a device for measuring the amount of hydrocarbon compounds released during pyrolysis, and a device for measuring carbon monoxide and carbon dioxide. Petition 870250083238, dated 09 / 16 / 2025, page 19 / 48 14 / 28 of carbon.

[0062] The process according to the invention comprises at least the following steps:

[0063] 1) Heating sequence in an inert atmosphere (pyrolysis)

[0064] 2) Heating sequence in an oxidizing atmosphere (oxidation)

[0065] 3) Gaussian deconvolution

[0066] 4) Determination of pyrogenic carbon content

[0067] The process steps according to the invention are detailed below.

[0068] 1. Heating sequence in an inert atmosphere (pyrolysis)

[0069] Throughout this stage, the sample containing an organomineral or mineral matrix, as well as biochar and / or charcoal, is heated in an inert atmosphere (for example, under a flow of nitrogen or helium) following a sequence of temperatures where the initial temperature (indicated below as T0) is between 100 and 300°C, preferably 200°C, and the final temperature (indicated below as TF) is between 500 and 800°C, preferably 650°C.

[0070] Preferably, the temperature sequence in an inert atmosphere may include at least one isothermal stage at the initial temperature T0, followed by a predetermined thermal gradient in order to raise the sample temperature to the final temperature TF. Figure 1A schematically illustrates the evolution of temperature T as a function of time t in this temperature sequence, showing an isothermal stage at temperature T0, followed by a thermal gradient until reaching temperature TF.

[0071] Advantageously, the temperature sequence in an inert atmosphere of this mode may additionally include a second Petition 870250083238, dated 09 / 16 / 2025, p. 20 / 48 15 / 28 isothermal stage, at the final temperature TF. In other words, a second isothermal stage at the final temperature TF follows the phase of the temperature sequence that is presented in the form of a thermal gradient. This allows, if necessary, the cracking of the compounds to continue with a cracking temperature close to the final temperature TF of the temperature sequence in an inert atmosphere according to the invention. Figure 1B schematically illustrates the evolution of temperature T as a function of time t of this temperature sequence, showing two isothermal stages, at temperatures T0 and TF as defined above, and linked together by a thermal gradient.

[0072] According to one embodiment of the invention, the initial temperature T0 is preferably 200°C. In fact, this temperature is sufficient to release the most labile organic compounds present in most soil, organic fertilizer or sediment samples.

[0073] According to one embodiment of the invention, the final temperature TF is preferably 650°C, to avoid obtaining CO and CO2 curves with incomplete peaks at the end of pyrolysis measured particularly in natural samples (fresh and dry plant tissues, waste, peat and plant compost, organomineral and mineral soils, surface formations).

[0074] According to one embodiment of the invention, the isothermal stage(s) of the temperature sequence in an inert atmosphere may have a predetermined duration other than zero (e.g., greater than half a minute), preferably between 1 and 5 minutes, more preferably 3 minutes. These durations allow the cracking of compounds with a cracking temperature close to the temperature of the isothermal stage to be considered complete. According to the embodiment of the invention in which the temperature sequence in an inert atmosphere according to the invention includes Petition 870250083238, dated 09 / 16 / 2025, page 21 / 48 16 / 28 various isothermal stages, in particular two isothermal stages at temperatures T0 and TF, the duration of one isothermal stage may differ from the duration of the other isothermal stage(s).

[0075] According to one embodiment of the invention, the thermal gradient(s) of the temperature sequence in an inert atmosphere may be between 1 and 50°C / min, preferably between 15° and 35°C / min, and most likely 25°C / min. These values ​​are balanced to allow thermal cracking of the compounds and to limit the process running time.

[0076] According to one embodiment of the invention, it is possible to continuously measure (i.e., continuously over time) the amount of hydrocarbon compounds released during heating in an inert atmosphere, and / or the amount of CO2 and / or the amount of CO contained in an effluent resulting from said heating. In other words, throughout this sequence, it is possible to continuously measure the amount of HC, CO, and CO2 released by the sample through the thermal cracking of organic matter and the thermal decomposition of carbonate minerals. The amount of hydrocarbon compounds can be measured with a flame ionization detector (FID). The amount of CO and CO2 released can be measured with an infrared (IR) detector. As a variant, other devices that measure the amount of HC, CO, and / or CO2 can be used.According to this implementation, at the end of this step applied to a given sample, a first representative curve of the amount of hydrocarbon compounds released over time during the pyrolysis phase can be obtained, in addition to two other representative curves of the amount of CO and CO2 released over time during the pyrolysis phase. These measurements can contribute to determining the conventional parameters of this thermal analysis, in particular the parameter indicated as TOC (for Total Organic Carbon), which... Petition 870250083238, dated 09 / 16 / 2025, page 22 / 48 17 / 28 corresponds to the carbon content of the sample, determined from the amount of hydrocarbons released by the sample and the amount of CO and CO2 released below the limit temperatures during the pyrolysis and oxidation phases; and the parameter indicated as MinC (for Mineral Carbon) corresponds to the mineral carbon content of the sample, determined from the amounts of CO and CO2 released by the sample above the limit temperatures during the pyrolysis and oxidation phases. The description of these general parameters can be found in the document (Behar et al., 2001).

[0077] In general, this particular heating sequence in an inert atmosphere is sufficient to allow the thermal cracking of classes of compounds containing mineral carbon and organic carbon, in particular:

[0078] - thermally very labile compounds, which are particularly abundant in fresh biological tissues, and which are generally released at temperatures between about 80 and 360°C;

[0079] - thermally labile compounds, which are the majority in organic samples such as garbage or peat, and which are generally released at temperatures between about 360 and 420°C;

[0080] - thermally resistant compounds, which are the majority in organomineral (soils) or mineral (alluvium, colluvium) samples, and which are generally released at temperatures between approximately 420°C and 470°C;

[0081] - thermally refractory compounds, which are generally released at temperatures between about 470 and 520°C;

[0082] - and thermally very refractory compounds, which are present in larger proportions in decomposition residues or exogenous fractions, such as pyrogenic or petrogenic organic matter, and which are generally released at temperatures between Petition 870250083238, dated 09 / 16 / 2025, page 23 / 48 18 / 28 approximately 520 and 650°C.

[0083] According to one embodiment of the invention, the temperature sequence in an inert atmosphere according to the invention may be preceded by a temperature increase phase of the pyrolysis furnace, which may be in the form of a thermal gradient, for example, between 1 and 50°C / min, preferably between 20 and 25°C / min, or any other form of temperature increase curve of the pyrolysis furnace. This preliminary temperature increase phase of the pyrolysis furnace allows the pyrolysis furnace to be set to the initial temperature of the temperature sequence in an inert atmosphere according to the invention. This preliminary phase may contribute to initiating the thermal cracking of compounds with a cracking temperature lower than the initial temperature of the temperature sequence in an inert atmosphere according to the invention, especially in the case of fresh biological tissues.

[0084] According to one embodiment of the invention, this sequence of temperatures in an inert atmosphere according to the invention may be followed by a temperature reduction phase of the pyrolysis furnace, which may be in the form of a thermal gradient, for example, between -1 and -50°C / min, preferably between -20 and -25°C / min, or any other form of pyrolysis furnace temperature reduction curve. This terminal phase of pyrolysis furnace temperature reduction allows, if necessary, the completion of the thermal cracking of the compounds associated with the final temperature of the sequence of temperatures in an inert atmosphere according to the invention. 2) Heating sequence in an oxidizing atmosphere (oxidation)

[0085] Throughout this second stage, the solid residue of the sample obtained at the end of the heating sequence in an inert atmosphere, as described in stage 1 above, is subjected to oxidation following a predefined temperature sequence, whose initial temperature (indicated as T0' below) is between 100 and 300°C, Petition 870250083238, dated 09 / 16 / 2025, page 24 / 48 19 / 28 preferably at 200°C, and the final temperature (indicated as TF' below) is between 700 and 1000°C, preferably 850°C (in order to deplete the mineral carbon). Furthermore, according to the invention, the temperature sequence of such heating in an oxidizing atmosphere includes at least a thermal gradient between 1 and 50°C / min, preferably between 15° and 35°C / min, preferably 25°C / min.

[0086] In general, the preferred temperature range for the initial temperature T0' of the temperature sequence in an oxidizing atmosphere allows avoiding episodes of instantaneous combustion of the sample residue at the beginning of the oxidation cycle.

[0087] According to one embodiment of the invention, the temperature sequence in an oxidizing atmosphere may also include an isothermal stage at the initial temperature T0' with a predetermined duration other than zero (e.g., greater than half a minute), preferably between 1 and 5 minutes, and more preferably 3 minutes.

[0088] According to the invention, at least one quantity of CO2 (and optionally a quantity of CO) released during this second temperature sequence is continuously measured. According to one embodiment of the invention, the measurement can be performed by an infrared (IR) detector. Note that such a sensor provides measured values ​​in millivolts (mV). Classically, the quantity of CO2 released during this second temperature sequence, indicated as Xtot below, is specified by determining the area under the curve measured (possibly between predefined temperatures) by the sensor, using a formula of the type: .. 12 SurfC X tot = —.—— (1) 44. mass

[0089] where SurfC corresponds to the area under the curve (also called thermogram) representing the amount of CO2 released during this second temperature sequence, maese corresponds to the sample mass, and Xtot is expressed in mg / g of sample. Petition 870250083238, dated 09 / 16 / 2025, p. 25 / 48 20 / 28 Alternatively, it is possible to use other devices that measure the amount of CO2.

[0090] Advantageously, the temperature sequence in an oxidizing atmosphere may also include an isothermal stage at a temperature between 500 and 600°C, preferably between 570 and 580°C, and ideally 576°C. This isothermal stage allows for better separation, in a curve representing the evolution as a function of temperature of the amount of CO2 released during heating in an oxidizing atmosphere, of a component attributed to biochar or charcoal from a component attributed to the mineral or organomineral matrix present in the sample considered. This contributes especially to improving the result of step 3) of the process according to the invention described below. This isothermal stage may have a predetermined duration other than zero (for example, greater than half a minute), preferably between 1 and 5 minutes, more preferably 3 minutes.According to this embodiment, the temperature sequence in an oxidizing atmosphere may also include an additional thermal gradient (i.e., in addition to at least one thermal gradient of the temperature sequence in step 2 of the process according to the invention), between 1°C and 50°C / min, preferably between 15 and 35°C / min, more preferably 25°C / min. Thus, according to this embodiment, the isothermal stage at a temperature between 500 and 600°C, preferably between 570 and 580°C, preferably 576°C, may be preceded and followed by at least two thermal gradients of this embodiment. 3) Gaussian deconvolution

[0091] Throughout this step, starting from a representative curve of the evolution as a function of temperature of the aforementioned quantity of CO2 released during heating in an oxidizing atmosphere, a Gaussian deconvolution is applied to said curve, in order to determine (at least) a first and a second centered Gaussian curve, Petition 870250083238, dated 09 / 16 / 2025, p. 26 / 48 21 / 28 respectively, at a first and a second temperature, wherein the said first temperature is between 380°C and 540°C, preferably between 415°C and 425°C, more preferably 420°C, and the said second temperature is between 500 and 600°C, preferably between 570 and 580°C, preferably 576°C.

[0092] By Gaussian deconvolution, we understand the decomposition of a curve (in this case, the curve representing the evolution as a function of temperature of the amount of CO2 released during the second temperature sequence) into elementary components, each corresponding to a Gaussian distribution.

[0093] Thus, this step aims to approximate the representative curve of the evolution as a function of temperature of the amount of CO2 released during the second temperature sequence by two Gaussians, more precisely, a first Gaussian centered at a temperature between 380°C and 540°C, preferably between 415°C and 425°C, more preferably 420°C, and a second Gaussian centered at a temperature between 500 and 600°C, preferably between 570 and 580°C, preferably 576°C. Indeed, the temperature range of the first Gaussian, between 380°C and 540°C, is characteristic of the temperature range of the main peak of a curve representing the amount of CO2 released by a sample of pure mineral or organomineral matrix, and for any type of mineral or organomineral matrix as described, for example, in the document (Sebag et al. 2018).In fact, it has been shown that, for samples of this type (mineral or organomineral matrix), the highest CO2 peak is emitted at such temperatures during the oxidation phase. These temperatures are lower than the temperatures at which the maximum CO2 is emitted for biochars or coals, due to the lower thermal stability of the mineral or organomineral matrix. Furthermore, the temperature range of the second Gaussian, between 500 and 600°C, is characteristic of... Petition 870250083238, dated 09 / 16 / 2025, page 27 / 48 22 / 28 peak temperature range of a representative curve of the amount of CO2 released by a sample of pure coal and / or biochar, and for any type of coal and / or biochar, as described, for example, in the document (Aubertin et al., 2022). In effect, it has been demonstrated that biochar or coal samples emit most of the CO2 in this temperature range. In other words, the peak temperatures of the two Gaussians according to the invention are, in a way, the “signatures” of the mineral or organomineral matrices and of the coal and / or biochar, regardless of their origin and composition.

[0094] According to a non-limiting embodiment of the invention, one process that can be used is the residual Gaussian deconvolution process described in the document (Sebag et al., 2006). More precisely, this process consists of progressively subtracting the Gaussians centered on the main peaks of the signal.

[0095] According to one embodiment, it is possible to use the Gaussian deconvolution process by means of an end-member mixing analysis, described in particular in the document (Paterson and Heslop, 2015), which consists of determining, by means of an algorithm, the Gaussian components that allow the signal to be best described, with a given number of Gaussians.

[0096] Figure 2 illustrates the result of decomposing a curve C for measuring the amount of CO2QCO2 released during step 2) of the process according to the invention in two Gaussians G1, G2. 4) Determination of pyrogenic carbon content

[0097] Throughout this step, from the surfaces of the first and second Gaussian surfaces determined in step 3), the pyrogenic carbon content present in the sample is determined. More precisely, according to the invention, the carbon content is determined. Petition 870250083238, dated 09 / 16 / 2025, p. 28 / 48 23 / 28 pyrogenic substance present in the sample considered, indicated below as X, using a formula of the type: X 2-A.X1 1+AB (2)

[0098] where X± and X2 are the carbon contents determined, respectively, from the surfaces of the aforementioned first and second Gaussian surfaces, A is a coefficient representing the proportion of the aforementioned matrix in the aforementioned second Gaussian surface in relation to the aforementioned first Gaussian surface, and B is a coefficient representing the proportion of the aforementioned coal and / or biochar in the aforementioned first Gaussian surface in relation to the aforementioned second Gaussian surface.

[0099] According to one embodiment of the invention, I1 can be determined by the formula: X1 = SurfGl (3)

[0100] and X2 by the formula: X2= SurfG2 (4)

[0101] where SurfG1 and SurfG2 are, respectively, the surfaces of the first and second Gaussians determined at the end of step 3 of the process according to the invention.

[0102] Equation (2) arises because deconvolution is imperfect in separating the contribution of the organomineral or mineral matrix from the contribution of biochar and / or charcoal in a curve measuring the amount of CO2 released during an oxidation phase. In other words, the first Gaussian resulting from the deconvolution according to the invention comprises mainly, of course, a contribution linked to the organomineral or mineral matrix (indicated below as X1,mat), and also a contribution from biochar and / or charcoal (indicated below as X1,bc). Similarly, the second Gaussian resulting from the deconvolution according to the invention comprises mainly, of course, a contribution from biochar and / or charcoal (indicated below as X2,bc), and also a contribution linked to the organomineral or mineral matrix. Petition 870250083238, dated 09 / 16 / 2025, p. 29 / 48 24 / 28 mineral (shown below as X1.bc). This is specifically illustrated in Figure 3, which schematically represents the portion of the organomineral or mineral matrix X1,mat and the portion of biochar and / or coal X1,bc in the first Gaussian G1, as well as the portion of biochar and / or coal X2,bc and the portion of the organomineral or mineral matrix X2,mat in the second Gaussian G2. With these notations, the coefficients A and B according to the invention can be described by the following formulas: X2,mat X 1,mat (5)

[0103] and B = 1^ (6) 2,bc

[0104] According to a first variant of the invention, coefficient A and / or coefficient B can be determined, respectively, from a sample of the pure organomineral or mineral matrix and from a sample of pure biochar and / or coal, representative of the organomineral or mineral matrix and the biochar and / or coal present in the sample considered, to which steps 1), 2) and 3) described above are applied. Coefficient A can then be determined by the ratio between the surface of the second Gaussian and the surface of the first Gaussian determined from the sample of pure organomineral or mineral matrix. Coefficient B can be determined by the ratio between the surface of the first Gaussian and the surface of the second Gaussian determined from the sample of pure biochar and / or coal.

[0105] According to a second variant of the invention, and particularly if samples of the pure organomineral or mineral matrix and / or pure biochar and / or coal, representative of the organomineral or mineral matrix and the biochar and / or coal present in the sample under consideration, are not available, equation (2) above may be performed by means of a coefficient A between a value of 0.17 and a value of 0.73, preferably 0.19, and / or a coefficient B between Petition 870250083238, dated 09 / 16 / 2025, pp. 30 / 48 25 / 28 a value of 0.10 and a value of 4.98, preferably 0.32. These ranges and preferred values ​​of coefficients A and B were determined from a plurality of samples of pure organomineral or mineral matrix and a plurality of samples of pure biochar and / or charcoal, of different types, to which the process described above was applied. In particular, samples of pure organomineral or mineral matrix of the soil and sediment type from varied climatic conditions and with varying total organic carbon contents, and samples of pure biochar and / or charcoal from varied plant biomass and varying pyrolysis temperatures, ranging from 450°C to 650°C, were used. The preferred value of coefficients A and B corresponds to the median of the values ​​determined in this way for the plurality of samples.

[0106] Thus, at the end of this stage, the pyrogenic carbon content present in the sample considered is obtained, which contains a mineral or organomineral matrix, in addition to coal and / or biochar.

[0107] According to one embodiment of the invention, the total mass of pyrogenic carbon present in the sample considered, indicated below as Qc, bcjníx, can be determined using a formula of the type: Qc, bcjníx = X3 / C * K (7)

[0108] Where

[0109] - C is the ratio between the carbon content determined from the surface of the second Gaussian surface determined in the case of a sample of biochar and / or pure coal, indicated as X2, bc, and the total mass of carbon in the sample of biochar and / or pure coal; in other words, the ratio C can be written as follows C = Ύ2, bc / (TOC,bc * Qty,bc) (8)

[0110] where TOC.bc and Qty, bc correspond, respectively, to the total organic carbon and the total mass of a sample of pure biochar / charcoal. According to one embodiment of the invention, and Petition 870250083238, dated 09 / 16 / 2025, p. 31 / 48 26 / 28 particularly if a sample of biochar and / or pure charcoal, representative of the biochar and / or charcoal present in the sample under consideration, is not available, equation (2) above can be performed using the ratio C between a value of 0.51 and a value of 1.76, preferably 1.06. This range and this preferred value were determined from a plurality of samples of biochar and / or pure charcoal of different types. The preferred value corresponds to the median of the values ​​thus determined for the plurality of samples.

[0111] - is a multiplier coefficient. According to one embodiment of the invention, the coefficient K can be between 12.0 and 12.5, preferably 12.2. These values ​​were determined from a plurality of samples of biochar and / or pure charcoal of different types. Examples

[0112] The characteristics and advantages of the process according to the invention will become clearer after reading the application example below.

[0113] The present invention is applied to determine the mass of pyrogenic carbon present in a sample corresponding to a soil-biochar mixture,

[0114] Several samples are generated, for different weight ratios between biochar and soil, by homogeneously mixing an agricultural soil and an industrial biochar from herbaceous plants. The total organic carbon (TOC) of the biochar and soil rises to 82.60% and 5.55%, respectively. Each sample formed in this way is dried at a temperature of less than or equal to 40°C until its weight stabilizes, and then ground to less than 200 µm.

[0115] Each sample is subjected to heating in an inert atmosphere according to the invention, after which the residue is subjected to heating in an oxidizing atmosphere according to the invention. A Petition 870250083238, dated 09 / 16 / 2025, pp. 32 / 48 27 / 28 Figure 2 presents the C curve of the amount of CO2 QCO2 measured during step 2) of the process according to the invention, as well as the result of step 3) of the process according to the invention, in the form of two Gaussians G1, G2, in the case of a sample up to 1% by mass of biochar.

[0116] Table 1 presents the mass of pyrogenic carbon (provided in mg of carbon, mgC) present in the samples considered, determined at the end of step 4 of the process according to the invention applied according to the first variant described above (determination of coefficients A and B of equation (2) from samples of soil and pure biochar; column Qc,bc_mix_V1) and according to the second variant described above (determination of coefficients A and B of equation (2) from their preferred values ​​defined above; column Qc,bc_mix_V2), as well as the actual mass of pyrogenic carbon present in the samples considered (column Qc,bc_mix_REAL), as a function of its mass ratio between biochar and soil (column Ratio).It can be observed that the mass of pyrogenic carbon determined by the present invention, applied according to its first variant or its second variant, is very close to the real values ​​(average error of 2.31% and maximum of 76.45% (sample with the lowest biochar / char content) for the first variant; average error of -3.54% and maximum of 29.63% for the second variant).

[0117] These results were obtained in less than 90 minutes for each sample, a time that essentially corresponds to the heating time in an inert atmosphere and the heating time in an oxidizing atmosphere for each sample.

[0118] Therefore, the present invention allows for the rapid and precise quantification of pyrogenic carbon in a sample of an organomineral or mineral matrix that also contains biochar or coal, by means of a simple thermal analysis to implement. Petition 870250083238, dated 09 / 16 / 2025, pp. 33 / 48 28 / 28 Reason Qc,bc_mix_REAL (mgC) Qc,bc_mix_V1 (mgC) Qc,bc_mix_V2 (mgC) 0.05 4.4 7.7 5.6 0.11 9.0 7.2 7.4 0.21 17.3 15.5 15.9 0.51 43.2 34.7 35.6 0.56 47.3 44.6 43.4 1.02 84.9 79.4 79.1 1.11 93.0 94.7 97.0 Petition 870250083238, dated 09 / 16 / 2025, pp. 34 / 48

Claims

1 / 4 CLAIMS 1. Process for quantifying the pyrogenic carbon content present in a sample containing an organomineral or mineral matrix, as well as coal and / or biochar, characterized in that it comprises: A) heating said sample in an inert atmosphere according to a first sequence of temperatures, whose initial temperature (T0) is between 100 and 300°C, and preferably 200°C, and whose final temperature (TF) is between 500 and 800°C, preferably 650°C;B) heating a residue from said sample resulting from said heating in an inert atmosphere according to a second temperature sequence, whose initial temperature (T0') is between 100 and 300°C, preferably 200°C, and whose final temperature (TF') is between 700 and 1000°C, preferably 850°C, said second temperature sequence including at least a thermal gradient between 1°C / min and 50°C / min, preferably between 15°C / min and 35°C / min, but preferably 25°C / min, and measuring at least one quantity of CO2 (QCO2) released during said second temperature sequence;C) Apply, from a representative curve of the evolution as a function of temperature of the aforementioned quantity of CO2 released during the aforementioned heating in an oxidizing atmosphere, a Gaussian deconvolution to the aforementioned curve, in order to determine a first and a second Gaussian curve centered, respectively, at a first and a second temperature, wherein the aforementioned first temperature is between 380°C and 540°C, preferably between 415°C and 425°C, more preferably 420°C, and the aforementioned second temperature is between 500 and 600°C, preferably between 570 and 580°C, preferably 576°C;D) determine, from the surfaces of the aforementioned first and second Gaussian surfaces, the aforementioned pyrogenic carbon content X3 present in the aforementioned sample using a formula of the type: _ X2-A.X1 3 1+AB where X1 and X2 are carbon contents determined, respectively, from the surfaces of the aforementioned first and second Gaussian surfaces, A is a coefficient representing the proportion of the aforementioned matrix in the aforementioned second Gaussian surface in relation to the aforementioned first Gaussian surface, and B is a coefficient representing the proportion of the aforementioned charcoal and / or biochar in the aforementioned first Gaussian surface in relation to the aforementioned second Gaussian surface.

2. Process, according to claim 1, characterized in that said first temperature sequence includes an isothermal stage of predetermined duration at said initial temperature (T0) of said first temperature sequence, followed by a thermal gradient to reach said final temperature (TF) of said first temperature sequence, wherein said predetermined duration of said isothermal stage of said first temperature sequence is between 1 and 5 minutes, preferably 3 minutes, and said thermal gradient of said first temperature sequence is between 1 and 50°C / min, preferably between 15°C / min and 35°C / min, more preferably 25°C / min.

3. A process, according to any of the preceding claims, characterized in that said second temperature sequence additionally includes an isothermal stage of predetermined duration at a temperature between 500 and 600°C, preferably between 570 and 580°C, preferably 576°C, wherein said predetermined duration of said isothermal stage of said second temperature sequence is between 1 and 5 minutes, preferably 3 minutes. Petition 870250083238, dated 09 / 16 / 2025, p. 36 / 48 3 / 4 4. A process, according to any of the preceding claims, characterized in that a sample of said organomineral or mineral matrix is ​​available, and wherein said coefficient A of step D) is determined in advance as follows: steps A) to C) are applied to said sample of said organomineral or mineral matrix, and said coefficient A is determined by calculating the ratio between the surface of a second Gaussian and the surface of a first Gaussian determined from said sample of said pure organomineral or mineral matrix.

5. A process, according to any of the preceding claims, characterized in that a sample of said biochar and / or said pure coal is additionally available, and said coefficient B of step D) is determined in advance as follows: steps A) to C) are applied to said sample of said biochar and / or said coal, and coefficient B is determined by calculating the ratio between the surface of said first Gaussian and the surface of said second Gaussian determined from said sample of biochar and / or pure coal.

6. A process, according to any of the preceding claims, characterized in that step D) is applied by means of a coefficient A between a value of 0.17 and a value of 0.73, preferably 0.19, and / or by means of a coefficient B between a value of 0.10 and a value of 4.98, preferably 0.

32.

7. Process, according to any of the preceding claims, characterized in that a total mass of pyrogenic carbon Qc,bc_mix present in said sample is determined using a formula of the type: Qc,Cc_mix = X3 / C * K, where C is a ratio between the carbon content determined from a second Gaussian surface determined for a sample of biochar and / or pure coal, and a total mass of carbon in said sample of biochar and / or pure coal, and where K is a multiplying coefficient between 12.0 and 12.5, preferably 12.

2.

8. Process according to any one of claims 1 to 6, characterized in that a total mass of pyrogenic carbon Qc,bc_mix present in said sample is determined using a formula of the type: Qc,bc_mix = X3 / C * K, where C is a ratio between a value of 0.51 and a value of 1.76, preferably 1.06, and K is a multiplier coefficient between 12.0 and 12.5, preferably 12.

2. Petition 870250083238, dated 09 / 16 / 2025, pp. 38 / 48

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