Analytical method of biochar

Abstract

To provide an analytical method of biochar suitable for efficiently analyzing a quality of carbon.SOLUTION: A method for analyzing biochar by thermogravimetry, includes the steps of: heating a sample composed of biochar to a first temperature zone of 900°C or higher in an oxygen-free gas atmosphere; lowering the temperature of the sample to a second temperature zone of 300°C or lower; heating the sample to a third temperature zone of 900°C or higher in an oxygen-containing gas atmosphere and burning the sample; estimating a carbonization temperature of the sample on the basis of a weight change of the sample in the step of heating the sample to the first temperature zone; and estimating the carbon dioxide storage amount of the sample on the basis of the weight change of the sample in the step of heating to the third temperature zone and burning.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for analyzing biochar. [Background technology]

[0002] In recent years, carbon capture and storage (CCS) through the application of biochar to soil and other materials has attracted global attention as a simple method for reducing atmospheric carbon dioxide. The Intergovernmental Panel on Climate Change (IPCC) report provides an example formula for calculating the carbon dioxide storage amount through biochar application, which can be calculated using values ​​categorized by biochar type and carbonization method. However, this method cannot calculate the carbon dioxide storage amount unless the carbon quality of the applied biochar is clearly known. Therefore, to calculate this carbon dioxide storage amount, carbon quality analysis is currently performed based on JIS M8812 (Coals and Cokes - Proximate Analysis Methods). However, JIS M8812 coal quality analysis has problems such as time-consuming analysis and large error due to manual analysis by analyst. In the analysis of coals and cokes, a method is known in which moisture, volatile matter, fixed carbon, and ash content are measured using a thermobalance under a temperature profile similar to that specified in JIS 8812, without relying on manual analysis (see, for example, Patent Document 1). In the analysis of biochar, it is important to understand the carbonization temperature and other aspects of the coal quality, but it has been difficult to obtain information about the quality of biochar using conventional methods. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 61-191950 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention was conceived under the above circumstances, and its main objective is to provide a method for analyzing biochar that is suitable for efficiently analyzing carbonaceous properties. [Means for solving the problem]

[0005] As a result of intensive research by the inventors into the above-mentioned problems, they discovered that when measuring and analyzing the weight of biochar using thermogravimetry, it is possible to estimate the charcoal quality (carbonization temperature and carbon dioxide storage amount) by heating the sample under specified conditions, then cooling it, and then heating it again and burning it, which led to the completion of the present invention.

[0006] A first aspect of the present invention provides a method for analyzing biochar by thermogravimetry, comprising the steps of: heating a sample of biochar to a first temperature range of 900°C or higher in an oxygen-free gas atmosphere; cooling the sample to a second temperature range of 300°C or lower; heating the sample to a third temperature range of 900°C or higher in an oxygen-containing gas atmosphere and combusting it; estimating the carbonization temperature of the sample based on the change in weight of the sample during the heating to the first temperature range; and estimating the carbon dioxide storage capacity of the sample based on the change in weight of the sample during the heating to the third temperature range and combusting it.

[0007] In a preferred embodiment of the first aspect of the present invention, in the step of estimating the carbonization temperature of the sample, data analyzing the relationship between the carbonization temperature and the pyrolysis temperature in the oxygen-free gas atmosphere for each type of biochar raw material is accumulated in advance, and the pyrolysis temperature of the sample in the oxygen-free gas atmosphere is compared with the data to estimate the carbonization temperature of the sample.

[0008] A second aspect of the present invention provides a method for analyzing biochar by thermogravimetry, comprising the steps of: heating a sample of biochar to a first temperature range of 900°C or higher in an oxygen-free gas atmosphere; cooling the sample to a second temperature range of 300°C or lower; heating the sample to a third temperature range of 900°C or higher in an oxygen-containing gas atmosphere and combusting it; estimating the raw material type and carbonization temperature of the sample based on the weight changes of the sample during the heating to the first temperature range, the cooling to the second temperature range, and the heating to the third temperature range and combustion steps; and estimating the carbon dioxide storage capacity of the sample based on the weight changes of the sample during the heating to the third temperature range and combustion step.

[0009] In a preferred embodiment of the second aspect of the present invention, in the step of estimating the carbonization temperature and raw material type of the sample, data analyzing the relationship between the carbonization temperature and five parameters, namely, the pyrolysis temperature in the oxygen-free gas atmosphere, the weight loss rate in the oxygen-free gas atmosphere, the pyrolysis temperature in the oxygen-containing gas atmosphere, the weight loss rate in the oxygen-containing gas atmosphere, and the residue ratio, for each type of biochar raw material is accumulated in advance, and the raw material type and carbonization temperature of the sample are estimated by comparing the five parameters of the sample with the data. [Effects of the Invention]

[0010] The biochar analysis method of the present invention makes it possible to estimate the carbon quality (carbonization temperature and carbon dioxide storage capacity) of biochar. In carbon sequestration through the use of biochar, the carbonization temperature of the biochar is an important factor in evaluating the carbon quality, and the present invention makes it possible to appropriately estimate the carbonization temperature of biochar.

[0011] Other features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing the relationship between temperature change and sample weight by thermogravimetry in the first embodiment of the biochar analysis method according to the present invention. [Figure 2] 1 is a graph showing an example of the change in sample weight for each carbonization temperature in the step of increasing the temperature to the first temperature zone. [Figure 3] 1 is a graph showing the relationship between the carbonization temperature and the pyrolysis temperature in an oxygen-free gas atmosphere depending on the type of biochar raw material in the step of raising the temperature to the first temperature zone. [Figure 4] 1 is a graph showing the relationship between fixed carbon in proximate analysis and weight loss rate in air in thermogravimetry. [Figure 5] 10 is a graph showing the relationship between temperature change and sample weight by thermogravimetry in the second embodiment of the biochar analysis method according to the present invention. [Figure 6] This is a graph showing the relationship between temperature change and sample weight when the type of biochar raw material is different. [Figure 7] This is a graph showing the relationship between temperature change and sample weight when the carbonization temperature of biochar is different. [Figure 8] This is a graph showing the relationship between temperature change and sample weight when the carbonization temperature of biochar is different. [Figure 9] FIG. 10 is a diagram showing an example of various parameters derived from the relationship between temperature change and sample weight. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will now be described in detail with reference to the drawings.

[0014] First Embodiment A first embodiment of the biochar analysis method according to the present invention is described below. In this embodiment, a biochar sample was prepared, and the weight of the sample was measured using thermogravimetry while changing the temperature of the sample. The measurement results were then analyzed. Furthermore, the components of the sample were analyzed using conventional industrial analysis and compared with the present analytical method (thermogravimetry). Here, "biochar" refers to any carbonized material obtained by carbonizing organic matter (biomass) derived from living organisms. Biochar can be made from a wide variety of raw materials, including wood, herbs, rice husks and rice straw, wheat husks, wheat straw, buckwheat husks, bean husks, bagasse, nuts, sludge, and livestock manure, as well as bamboo charcoal.

[0015] <Sample preparation> Biomass, the raw material for biochar, was carbonized at a predetermined temperature to produce biochar samples. Specifically, the biomass raw material was heat-treated at a predetermined temperature of 300-800°C in a semi-sealed iron container placed in an electric furnace to obtain biochar samples. Biochar samples were prepared for each type of biochar raw material at carbonization temperatures of 300°C, 350°C, 400°C, 500°C, 600°C, 700°C, and 800°C.

[0016] <Measurement of samples by thermogravimetry> Measurement or analysis of samples using thermogravimetry is performed using, for example, a thermobalance. In this embodiment, the thermobalance was used in conjunction with an autosampler to analyze the samples. First, a biochar sample was heated to 900°C or higher (a step of heating to the first temperature range). The sample was then cooled to 300°C or lower and cooled (a step of cooling to the second temperature range). The sample was then heated again to 900°C or higher and combusted (a step of heating to the third temperature range and combusting). The steps of heating the sample to 900°C or higher (a step of heating to the first temperature range) and then cooling to 300°C or lower (a step of cooling to the second temperature range) are performed in an oxygen-free gas (e.g., nitrogen gas) atmosphere. The subsequent step of heating the sample to 900°C or higher and combusting it (a step of heating to the third temperature range and combusting it) is performed in an oxygen-containing gas (e.g., air) atmosphere. The sample weight (TG) was then continuously measured during the sample temperature change process as described above.

[0017] <Industrial analysis> The proximate analysis for the comparative study was carried out in accordance with JIS M8812 (coals and cokes - proximate analysis method), and the weight ratios of volatile matter, fixed carbon, and ash were determined.

[0018] Figure 1 is a graph showing an example of the relationship between temperature change and weight of a sample measured by thermogravimetry. In the example shown in Figure 1, a biochar sample was first heated from room temperature to approximately 950°C in a nitrogen gas atmosphere (the step of heating to the first temperature zone). The heating rate was 10°C / min. After heating, the sample was maintained at a high temperature of approximately 950°C for approximately 10 minutes. Next, the sample was cooled to approximately 260°C (the step of cooling to the second temperature zone). The heating rate was 10°C / min. After cooling, the sample was maintained at a low temperature of approximately 260°C for approximately 10 minutes. The sample was then heated to approximately 950°C in an air atmosphere and combusted (the step of heating to the third temperature zone and combusting). The heating rate was 10°C / min. The thin line in Figure 1 represents the sample temperature.

[0019] In the example shown in Figure 1, the sample is biochar from red pine (wood-derived), and the carbonization temperature of the sample is 500°C. The thick line in Figure 1 represents the sample weight (TG). The sample weight is expressed as a percentage, which is the ratio of the weight of the sample at the time of measurement to the weight of the sample before the start of measurement. Note that the temperature change of the sample shown in Figure 1 is an example, and this analysis method is not limited to this. The temperature increase and decrease rates of the sample are also not limited to the example shown in the figure.

[0020] <Estimation of sample carbonization temperature> The thermogravimetric analysis was performed on the measurement results obtained by heating, cooling, and burning the sample as described above. In the process of heating the sample in a nitrogen gas atmosphere (heating up to the first temperature range), the sample undergoes thermal decomposition and loses weight as the temperature is increased. The thermal decomposition temperature of the sample in a nitrogen gas atmosphere is considered to be the same as or higher than the carbonization temperature of the sample. In this case, the change in sample weight at each carbonization temperature during the process of heating the sample in a nitrogen gas atmosphere was analyzed.

[0021] Figure 2 is a graph showing an example of the change in sample weight for each carbonization temperature during the process of heating the sample under a nitrogen gas atmosphere. Figure 2 shows the weight change of a sample made from red pine (wood-derived) biochar. Specifically, it shows the relationship between sample temperature and sample weight (TG) for each carbonization temperature. As the sample temperature exceeds approximately 200°C, weight loss due to thermal decomposition of volatile matter gradually begins. The temperature of the inflection point on the sample weight curve at the start of this weight loss (this inflection point is plotted in Figure 2) was determined to be the thermal decomposition temperature of the sample under a nitrogen gas atmosphere. From the graph shown in Figure 2, the following findings (1) and (2) were obtained: (1) As the carbonization temperature of the sample increases, the thermal decomposition temperature also shifts toward a higher temperature. (2) As the carbonization temperature of the sample increases, the amount of thermal decomposition decreases.

[0022] FIG. 3 is a graph showing the relationship between the carbonization temperature of biochar and the pyrolysis temperature in a nitrogen gas atmosphere depending on the type of raw material of the biochar in the process of heating the sample in a nitrogen gas atmosphere.

[0023] The relationship between the carbonization temperature and pyrolysis temperature under a nitrogen gas atmosphere for each type of biochar raw material thus obtained is stored as known sample data. Then, a new biochar sample to be analyzed is similarly measured using the thermogravimetric method of this embodiment. The pyrolysis temperature under a nitrogen gas atmosphere, determined from the weight change during the process of heating the biochar sample under a nitrogen gas atmosphere (the process of heating the sample to the first temperature zone), is compared with the known sample data, allowing the carbonization temperature of the biochar sample to be analyzed to be estimated.

[0024] <Estimation of carbon dioxide storage in samples> The weight loss rate of biochar under air was determined based on the thermogravimetric measurement results described above with reference to Figure 1. In the example shown in Figure 1, the arrow "A" corresponds to the weight loss rate under a nitrogen gas atmosphere (hereinafter referred to as "weight loss rate under nitrogen"), and the arrow "B" corresponds to the weight loss rate under an air atmosphere (hereinafter referred to as "weight loss rate under air"). For the biochar shown in Figure 1 (made from red pine and carbonized at 500°C), the weight loss rate under nitrogen is approximately 20%, and the weight loss rate under air is approximately 79%. Note that weight loss is observed in the early stages of the process of heating the biochar sample under a nitrogen gas atmosphere (the process of heating to the first temperature range), but this weight loss corresponds to moisture remaining in the biochar sample. The weight loss rate under nitrogen and the weight loss rate under air are expressed as percentages based on the sample weight after moisture removal. This also applies to the second embodiment described below.

[0025] The weight loss rate under nitrogen measured by thermogravimetry is the weight loss due to thermal decomposition and corresponds to the volatile matter in proximate analysis (JIS M8812). The weight loss rate under air measured by thermogravimetry is the weight loss due to combustion and corresponds to the fixed carbon in proximate analysis.

[0026] According to the methodology (AG-004) of the government-certified J-Credit Scheme, the calculation of carbon dioxide storage in the crediting of biochar application requires an estimation of the carbonization temperature of the charred material, and a carbonization temperature of 350°C or higher is required. Furthermore, it is possible to calculate the carbon dioxide storage amount based on the amount of fixed carbon using a predetermined calculation formula for each raw material and carbonization method. In this embodiment, for each of several types of biochar raw material, samples with different carbonization temperatures were measured for fixed carbon using proximate analysis (JIS M8812) and weight loss under air using thermogravimetry, and then compared.

[0027] Figure 4 is a graph showing the relationship between fixed carbon in proximate analysis (JIS M8812) and the rate of weight loss in air in thermogravimetry. As shown in Figure 4, the types of biochar measured were diverse, including bamboo charcoal, red pine charcoal, oak charcoal, rice husk charcoal, sludge charcoal, and manure charcoal. The measurement results shown in Figure 4 show that for each of these various types of biochar, the fixed carbon (%) and the rate of weight loss in air (%) were close to each other, demonstrating a high correlation between the two.

[0028] This allows us to estimate the amount of carbon dioxide stored by applying the weight loss rate in air, calculated from the change in weight of a biochar sample during the process of heating and burning the sample in an air atmosphere in the thermogravimetric method (the process of heating to the third temperature zone and burning), to the formula for calculating carbon dioxide storage based on the amount of fixed carbon in proximate analysis (JIS M8812).

[0029] Next, the operation of this embodiment will be described.

[0030] As described above, this embodiment makes it possible to estimate the carbon quality (carbonization temperature and carbon dioxide storage capacity) of biochar. In carbon sequestration through biochar application, the carbonization temperature of the biochar is an important factor in evaluating the carbon quality. This embodiment makes it possible to appropriately estimate the carbonization temperature of biochar. This allows for the determination of whether the carbonization temperature of the biochar falls in the low-temperature range (350°C or higher but less than 450°C), the mid-temperature range (450°C or higher but less than 600°C), or the high-temperature range (600°C or higher). Furthermore, conventional industrial analysis (JIS M8812) requires approximately 10 hours for measurement, which can lead to errors due to manual analysis. In contrast, the thermogravimetric method of this embodiment requires approximately 4 hours for measurement, which is expected to shorten the measurement time and increase accuracy. Furthermore, the thermogravimetric method of this embodiment can be used in conjunction with an autosampler to enable more efficient sample analysis.

[0031] Second Embodiment A second embodiment of the biochar analysis method according to the present invention will be described. In this embodiment, the preparation of biochar samples, the measurement of the samples by thermogravimetry, and the proximate analysis for comparative analysis are the same as those in the first embodiment.

[0032] FIG. 5 is a graph showing an example of the relationship between temperature change and weight of a sample measured by thermogravimetry. In the example shown in FIG. 5, the sample is rice husk biochar, and the carbonization temperature of the sample is 300°C. The temperature change conditions of the sample shown in FIG. 5 were the same as those of the embodiment shown in FIG. 1. Specifically, first, the biochar sample was heated from room temperature to approximately 950°C in a nitrogen gas atmosphere (a step of heating to the first temperature zone). The heating rate was 10°C / min. After heating, the high temperature of approximately 950°C was maintained for approximately 10 minutes. Next, the sample was cooled to approximately 260°C (a step of cooling to the second temperature zone). The heating rate was 10°C / min. After cooling, the low temperature of approximately 260°C was maintained for approximately 10 minutes. Thereafter, the sample was heated to approximately 950°C in an air atmosphere and combusted (a step of heating to the third temperature zone and combusting). The heating rate was 10°C / min. The thin line in Figure 5 represents the sample temperature. The thick line in Figure 5 represents the sample weight (TG). The sample weight is expressed as a percentage, which is the ratio of the sample weight at the time of measurement to the sample weight before the start of measurement. Note that the sample temperature change shown in Figure 5 is an example, and this analysis method is not limited to this. The sample temperature increase and decrease rates are also not limited to the example shown in the figure.

[0033] <Estimation of carbonization temperature and raw material type of sample> The thermogravimetric analysis was performed on the samples by heating, cooling, and burning them as described above. In this embodiment, the five parameters A to E shown in FIG. 5 were analyzed based on the changes in sample weight. The arrow "A" corresponds to the weight loss rate in a nitrogen gas atmosphere. The arrow "B" corresponds to the weight loss rate in an air atmosphere. The arrow "C" corresponds to the residue (ash) fraction. "D" in the figure indicates the pyrolysis temperature in a nitrogen gas atmosphere. As described in the first embodiment, the pyrolysis temperature in a nitrogen gas atmosphere is the inflection point temperature of the sample weight curve in a nitrogen gas atmosphere (the step of heating to the first temperature zone), and is the temperature at which weight loss begins. "E" in the figure indicates the pyrolysis temperature in an air atmosphere. The pyrolysis temperature in an air atmosphere is the inflection point temperature of the sample weight curve in an air atmosphere (the step of heating to the third temperature zone and burning), and is the temperature at which weight loss begins.

[0034] Figure 6 shows the relationship between temperature change and sample weight for different types of biochar samples. In the example shown in Figure 6, the biochar samples were made from chicken manure, red pine, oak, and rice husks, and the carbonization temperature for each sample was 500°C. As shown in Figure 6, the sample weight curves for different types of biochar samples were clearly different, even when the carbonization temperature was the same. For chicken manure, the weight loss rate under nitrogen (parameter A) was 38.8%, the weight loss rate under air (parameter B) was 9.9%, the residue (ash) fraction (parameter C) was 51.3%, the pyrolysis temperature under nitrogen gas (parameter D) was 681.1°C, and the pyrolysis temperature under air (parameter E) was 334.5°C. When the raw material was red pine, the weight loss rate under nitrogen (parameter A) was 20.1%, the weight loss rate under air (parameter B) was 79.1%, the residue (ash) fraction (parameter C) was 0.8%, the pyrolysis temperature under nitrogen gas (parameter D) was 541.7°C, and the pyrolysis temperature under air (parameter E) was 483.6°C.When the raw material was oak, the weight loss rate under nitrogen (parameter A) was 17.4%, the weight loss rate under air (parameter B) was 80.4%, the residue (ash) fraction (parameter C) was 2.3%, the pyrolysis temperature under nitrogen gas (parameter D) was 541.7°C, and the pyrolysis temperature under air (parameter E) was 477.8°C. When the raw material was rice husk, the weight loss rate under nitrogen (parameter A) was 10.4%, the weight loss rate under air (parameter B) was 45.4%, the residue (ash) ratio (parameter C) was 44.3%, the pyrolysis temperature under nitrogen gas atmosphere (parameter D) was 540.3°C, and the pyrolysis temperature under air atmosphere (parameter E) was 414.0°C. In particular, when the raw material was chicken manure, the residue (ash) ratio (parameter C) was significantly large. For rice husk, the residue (ash) ratio (parameter C) was also relatively large.

[0035] Figure 7 shows the relationship between temperature change and sample weight for biochar samples at different carbonization temperatures. In the example shown in Figure 7, the raw material for the biochar samples was oak, and the samples were carbonized at 300°C, 500°C, and 700°C. As shown in Figure 7, the sample weight curves were clearly different for different carbonization temperatures, even when the raw material was the same. For a carbonization temperature of 300°C, the weight loss rate under nitrogen (parameter A) was 45.0%, the weight loss rate under air (parameter B) was 54.1%, the residue (ash) fraction (parameter C) was 0.9%, the pyrolysis temperature under nitrogen gas (parameter D) was 352.8°C, and the pyrolysis temperature under air (parameter E) was 477.8°C. When the carbonization temperature was 500°C, the weight loss rate under nitrogen (parameter A) was 17.4%, the weight loss rate under air (parameter B) was 80.4%, the residue (ash) fraction (parameter C) was 2.3%, the pyrolysis temperature under nitrogen gas (parameter D) was 541.7°C, and the pyrolysis temperature under air (parameter E) was 477.8°C.When the carbonization temperature was 700°C, the weight loss rate under nitrogen gas (parameter A) was 6.1%, the weight loss rate under air (parameter B) was 88.6%, the residue (ash) fraction (parameter C) was 5.3%, the pyrolysis temperature under nitrogen gas (parameter D) was 750.0°C, and the pyrolysis temperature under air (parameter E) was 476.3°C. As can be seen from the above results, as the carbonization temperature of the biochar sample (oak charcoal) increased, the weight loss rate under nitrogen (parameter A) decreased and the weight loss rate under air (parameter B) increased.

[0036] Figure 8 shows the relationship between temperature change and sample weight for biochar samples at different carbonization temperatures. In the example shown in Figure 7, the raw material for the biochar sample was chicken manure, and the carbonization temperatures for the samples were 300°C, 500°C, and 700°C. As shown in Figure 8, the sample weight curves were clearly different for different carbonization temperatures, even for the same raw material biochar sample. For a carbonization temperature of 300°C, the weight loss rate under nitrogen (parameter A) was 47.2%, the weight loss rate under air (parameter B) was 11.2%, the residue (ash) fraction (parameter C) was 41.6%, the pyrolysis temperature under nitrogen gas (parameter D) was 356.7°C, and the pyrolysis temperature under air (parameter E) was 349.1°C. At a carbonization temperature of 500°C, the weight loss rate under nitrogen (parameter A) was 38.8%, the weight loss rate under air (parameter B) was 9.9%, the residue (ash) fraction (parameter C) was 51.3%, the pyrolysis temperature under nitrogen gas (parameter D) was 681.1°C, and the pyrolysis temperature under air (parameter E) was 334.5°C. At a carbonization temperature of 700°C, the weight loss rate under nitrogen (parameter A) was 36.8%, the weight loss rate under air (parameter B) was 7.6%, the residue (ash) fraction (parameter C) was 55.6%, the pyrolysis temperature under nitrogen gas (parameter D) was 684.2°C, and the pyrolysis temperature under air (parameter E) was 331.6°C. As can be seen from the above results, as the carbonization temperature of the biochar sample (chicken manure charcoal) increased, the weight loss rate under nitrogen (parameter A) decreased and the weight loss rate under air (parameter B) increased. Furthermore, as can be seen by comparing with the case shown in Figure 7 above (where the raw material for the biochar sample was oak), even if the carbonization temperature of the biochar sample was the same, there were clear differences in the weight loss rate under nitrogen (parameter A), weight loss rate under air (parameter B), residue (ash) proportion (parameter C), and pyrolysis temperature under air atmosphere (parameter E), etc., depending on the type of raw material for the biochar.

[0037] Figure 9 shows examples of the parameters A to E derived from the sample weight curves in the process of raising the temperature of a sample in a nitrogen gas atmosphere (a process of raising the temperature to the first temperature range), the process of lowering the temperature of the sample (a process of lowering the temperature to the second temperature range), and the process of raising the temperature and burning the sample in an air atmosphere (a process of raising the temperature to the third temperature range and burning). Figure 9 shows data for multiple samples with different carbonization temperatures for each of several biochar raw material types. It can be seen that there are significant differences in the pyrolysis temperature (parameter E) in an air atmosphere between the raw material types of red pine and oak, rice husks, and chicken manure.

[0038] For each type of biochar obtained in this way, sample weight curves (parameters A to E) at multiple carbonization temperatures are stored as known sample data. Then, similar measurements are performed using the thermogravimetric method of this embodiment on new biochar samples to be analyzed. By comparing the sample weight curves (parameters A to E) of the biochar sample to be analyzed during the process of heating the sample in a nitrogen gas atmosphere (heating to a first temperature range), cooling the sample (cooling to a second temperature range), and heating and combusting the sample in an air atmosphere (heating to a third temperature range and combusting) with the known sample data, the raw material type and carbonization temperature of the biochar sample to be analyzed can be estimated.

[0039] <Estimation of carbon dioxide storage in samples>

[0040] The weight loss rate under nitrogen measured by thermogravimetry is the weight loss due to thermal decomposition and corresponds to the volatile matter in proximate analysis (JIS M8812). The weight loss rate under air measured by thermogravimetry is the weight loss due to combustion and corresponds to the fixed carbon in proximate analysis.

[0041] According to the methodology of the J-Credit Scheme (AG-004), the condition for crediting carbon dioxide storage through biochar application is that the carbonization temperature during biochar production must be 350°C or higher. In this embodiment, for each of several types of biochar raw materials, samples with different carbonization temperatures were measured for fixed carbon using proximate analysis (JIS M8812) and weight loss under air using thermogravimetry, and then compared.

[0042] As explained in the first embodiment with reference to Figure 4, the measurement results shown in Figure 4 show that for each of the various types of biochar, such as bamboo charcoal, red pine charcoal, oak charcoal, rice husk charcoal, sludge charcoal, and manure charcoal, the fixed carbon (%) and the weight loss rate in air (%) were close to each other, and a high correlation was observed between the two.

[0043] This allows us to estimate the amount of carbon dioxide stored by applying the weight loss rate in air, calculated from the change in weight of a biochar sample during the process of heating and burning the sample in an air atmosphere in the thermogravimetric method (the process of heating to the third temperature zone and burning), to the formula for calculating carbon dioxide storage based on the amount of fixed carbon in proximate analysis (JIS M8812).

[0044] Next, the operation of this embodiment will be described.

[0045] As described above, this embodiment makes it possible to estimate the quality of biochar (raw material type, carbonization temperature, and carbon dioxide storage capacity). In carbon sequestration through biochar application, the raw material type and carbonization temperature of the biochar are important factors in evaluating the quality of the biochar. This embodiment makes it possible to appropriately estimate the raw material type and carbonization temperature of the biochar. This allows for the determination of whether the carbonization temperature of the biochar falls in the low-temperature range (350°C or higher but less than 450°C), the mid-temperature range (450°C or higher but less than 600°C), or the high-temperature range (600°C or higher). Furthermore, conventional industrial analysis (JIS M8812) requires approximately 10 hours for measurement, which can lead to errors due to manual analysis. In contrast, the thermogravimetric method of this embodiment requires approximately 4 hours for measurement, which is expected to shorten the measurement time and increase accuracy. Furthermore, the thermogravimetric method of this embodiment can be used in conjunction with an autosampler to enable more efficient sample analysis.

[0046] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to the above-described embodiments, and all modifications within the scope of the matters described in each claim are all included in the scope of the present invention.

Claims

1. 1. A method for analyzing biochar by thermogravimetry, comprising: A step of heating a sample made of biochar to a first temperature zone of 900°C or more in an oxygen-free gas atmosphere; a step of lowering the temperature of the sample to a second temperature range of 300°C or less; a step of heating the sample to a third temperature zone of 900°C or higher in an oxygen-containing gas atmosphere and combusting the sample; a step of estimating a carbonization temperature of the sample based on a change in weight of the sample during the step of raising the temperature to the first temperature zone; and estimating the amount of carbon dioxide stored in the sample based on the change in weight of the sample during the step of heating the sample to the third temperature zone and burning it.

2. 2. The biochar analysis method of claim 1, wherein in the step of estimating the carbonization temperature of the sample, data analyzing the relationship between the carbonization temperature and the pyrolysis temperature in the oxygen-free gas atmosphere for each type of biochar raw material is accumulated in advance, and the pyrolysis temperature of the sample in the oxygen-free gas atmosphere is compared with the data to estimate the carbonization temperature of the sample.

3. 1. A method for analyzing biochar by thermogravimetry, comprising: A step of heating a sample made of biochar to a first temperature zone of 900°C or more in an oxygen-free gas atmosphere; a step of lowering the temperature of the sample to a second temperature range of 300°C or less; a step of heating the sample to a third temperature zone of 900°C or higher in an oxygen-containing gas atmosphere and combusting the sample; a step of estimating the raw material type and carbonization temperature of the sample based on changes in weight of the sample during the step of heating the sample to the first temperature zone, the step of cooling the sample to the second temperature zone, and the step of heating the sample to the third temperature zone and burning the sample; and estimating the amount of carbon dioxide stored in the sample based on the change in weight of the sample during the step of heating the sample to the third temperature zone and burning it.

4. 4. The biochar analysis method of claim 3, wherein in the step of estimating the carbonization temperature and raw material type of the sample, data analyzing the relationship between the carbonization temperature and five parameters, i.e., the pyrolysis temperature in the oxygen-free gas atmosphere, the weight loss rate in the oxygen-free gas atmosphere, the pyrolysis temperature in the oxygen-containing gas atmosphere, the weight loss rate in the oxygen-containing gas atmosphere, and the residue proportion, for each type of biochar raw material is accumulated in advance, and the raw material type and carbonization temperature of the sample are estimated by comparing the five parameters of the sample with the data.

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