Determination method for low co2 steel material

Abstract

To provide a determination method for a low CO2 steel material that takes into account diverse manufacturing processes and diverse energy sources.SOLUTION: This low CO2 steel material determination method includes a step of obtaining the total amount of emissions U of carbon dioxide and the total amount of reductions R of carbon dioxide at the manufacturing line 4 based on information on the type and amount of energy source used in the steel material manufacturing line 4 when manufacturing the standard steel material, and information on the amount of reductions of carbon dioxide and a step of determining the type and amount of low CO2 steel material for the shipped steel material based on the total amount of emissions U of carbon dioxide and total amount of reductions R of carbon dioxide.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a method for determining low CO2 steel. [Background technology]

[0002] In recent years, efforts toward a carbon-neutral society have become important. Accordingly, even Scope 3 businesses that do not directly emit greenhouse gases are increasingly demanding to understand information related to carbon dioxide emissions during manufacturing for parts purchased for their own products. In particular, for steel products, which use a lot of energy during manufacturing, in order to meet this demand, it is a challenge to develop a system that determines which steel products are low-CO2 steel and discloses that information to purchasers. For example, Patent No. 7075530 discloses an information system related to low CO2 emissions that links certification information that proves that the electricity used in the manufacture of steel products is derived from renewable energy sources to mill sheet information. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7075530 Summary of the Invention [Problem to be solved by the invention]

[0004] The manufacturing of steel involves many processes, such as steelmaking and rolling. In addition, energy sources used include not only electricity, but also gas and oil. Taking these factors into consideration, it is necessary to determine the type and amount of low-CO2 steel.

[0005] It is an object of the present invention to provide a method for determining low CO2 steel, taking into account the various steps in the production of steel and the various energy sources used in the production of steel. [Means for solving the problem]

[0006] A method for determining low CO2 steel according to one embodiment uses a computer including a controller, a storage device, and a communication interface, and determines low CO2 steel by operating the controller with a program stored in the storage device. This method includes the steps of: acquiring information on the type and amount of energy source used in a steel production line when a reference steel is produced via the communication interface and storing the information in the storage device; acquiring information on the amount of carbon dioxide reduction via the communication interface and storing the information in the storage device; reading the information on the type and amount of energy source used and the information on the amount of carbon dioxide reduction from the storage device, and calculating the total amount of carbon dioxide emission U and the total amount of reduction R of carbon dioxide in the production line when the reference steel is produced based on the information; and determining the type and amount of low CO2 steel for shipped steel based on the total amount of emission U and the total amount of reduction R. Effect of the Invention

[0007] In this method for determining low-CO2 steel, the type and amount of low-CO2 steel for shipped steel are determined based on the total amount of carbon dioxide emissions U and the total reduction amount R emitted on the steel production line when manufacturing the standard steel. This method makes it possible to determine low-CO2 steel taking into account the various processes in steel manufacturing and the various energy sources used in steel manufacturing. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a steel manufacturing facility according to one embodiment. [Diagram 2] FIG. 2 is a block diagram of the facility's administrative computer of FIG. 1, along with the devices connected to the administrative computer. [Diagram 3] FIG. 3 is a flowchart showing a method for determining low CO2 steel and creating an inspection certificate according to one embodiment, which is performed in the facility of FIG. [Figure 4]FIG. 4 is an example of an inspection certificate prepared by the method shown in the flow chart of FIG. [Diagram 5] FIG. 5 is an example of an inspection certificate prepared by a method for preparing an inspection certificate for steel materials according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0010] 1 is a schematic diagram showing a steel manufacturing facility 2 according to one embodiment. The facility 2 includes a manufacturing line 4 and a management computer 6. The management computer 6 determines whether a steel product is low CO2 and creates an inspection certificate 7.

[0011] The facility 2 includes multiple production lines 4 for producing various steel products. In Fig. 1, production lines 4 for steel bars 10, metal powder 11, and hot extrusion products 13 are shown as examples. For example, in the steel bar 10 production line 4, scrap is used as a raw material to produce the steel bars 10. Each production line includes various processes. Although each production line 4 is shown as being separate in Fig. 1, there may be processes common to each production line 4.

[0012] FIG. 1 shows a melting process 12, a casting process 14, a rolling process 16, and an inspection process 18 as typical processes for manufacturing a steel bar 10. In the melting process 12, scrap is charged into an electric furnace 20, and the scrap is melted in the electric furnace 20. The scrap becomes molten steel 8. After impurities are removed from the molten steel 8 and the composition is adjusted, the molten steel 8 is charged into a continuous casting machine 22 in the casting process 14. This forms a bloom 24. The process from the scrap to forming the bloom 24 is also called a steelmaking process. In the rolling process 16, the bloom 24 is rolled and shaped in several stages. Depending on the product, further treatments such as heat treatment, shot blasting, and straightening are performed. In the inspection process 18, the product is inspected, and the steel bar 10, which is a steel product, is completed.

[0013] 2 shows a block diagram of the management computer 6 together with devices connected to the management computer 6. The management computer 6 is connected to the production line 4 via a network 26. The network 26 may be composed of only an intranet, or may be connected via the Internet. An input device 28 and an output device 30 are connected to the management computer 6. The output device 30 is typically a display and a printer. The management computer 6 may be connected to an external system via the network 26.

[0014] 2, the management computer 6 includes a controller 32, a storage device 34, and a communication interface 36. The typical controller 32 is a CPU. The management computer 6 may include a plurality of CPUs as the controller 32. The storage device 34 is typically a semiconductor memory or a hard disk. A plurality of semiconductor memories or hard disks may exist as the storage device 34. A storage device 34 that combines a plurality of semiconductor memories and a hard disk may also be used. The communication interface 36 transmits and receives data via the network 26.

[0015] Fig. 3 is a flow chart showing a method for determining whether a steel product is low CO2 or not, which is carried out in the steel manufacturing facility 2 in Fig. 1, and a method for creating an inspection certificate 7 for the steel product using the results of the determination. These methods are specifically executed by operating the controller 32 using a program stored in the memory 34. As shown in Fig. 3, this method includes six steps from step S1 to S6. Steps S1 to S4 constitute the method for determining whether a steel product is low CO2 or not, and steps S1 to S6 constitute the method for creating an inspection certificate 7 for the steel product.

[0016] In step S1, the management computer 6 acquires the types and amounts of energy sources used in all the production lines 4 when the reference steel material is produced from the production line 4 via the communication interface 36. The reference steel material is a steel material that serves as a reference for calculating the CO2 emission amount and the CO2 reduction amount described later. In this embodiment, the reference steel material is a steel material produced in a predetermined period. The energy sources include the energy sources used in all the production processes of the steel material, such as the steelmaking process, the rolling process 16, and the inspection process 18. The amount of energy is summed up for each type of energy source over this predetermined period and stored in the memory 34 together with the type of energy source. In this embodiment, the amount of energy is summed up for one year. This sum is the type and amount of energy source used in the production line 4 when the reference steel material is produced. This summation may be performed by the management computer 6, or may be summed up by the production line 4 and sent to the management computer 6. The predetermined period may be one month, six months, or any other period.

[0017] Table 1 shows an example of calculation of the total carbon dioxide emission and the total reduction in the production line 4, as will be described later in detail. The "energy source" column in Table 1 shows the type of energy source used in the production line 4 in this embodiment, and the "annual usage" column shows the amount used for each energy source in a given period (one year in this embodiment). In this table, the energy sources are listed separately as energy sources related to greenhouse gas emissions corresponding to Scope 1, such as city gas and gasoline, and energy sources related to greenhouse gas emissions corresponding to Scope 2, such as electricity and steam. Electricity is listed separately for each power company that supplies it. Furthermore, electricity that is certified by a non-fossil certificate as being generated from a non-fossil fuel source is listed as a different type of electricity. Data corresponding to the "energy source" and "annual usage" in Table 1 is stored in the memory 34.

[0018] In step S2, the management computer 6 acquires information on the amount of carbon dioxide reduction for each energy source via the communication interface 36, and stores this information in the memory 34. In the embodiment of Table 1, the amount of carbon dioxide reduction (CO2 reduction) in mass units is stored. For example, with city gas, the adoption of the Eco Process has reduced carbon dioxide by 5,369 tons. The validity of this amount of carbon dioxide reduction is guaranteed by being certified by a third-party verification organization. For electricity that is certified by a Non-Fossil Certificate as being generated from a non-fossil fuel source, the amount of carbon dioxide corresponding to that amount is read as the amount of carbon dioxide reduction.

[0019] The amount of reduction in the use of energy such as city gas may be stored as information on the amount of carbon dioxide reduction. For example, if the amount of city gas reduction by adopting the eco-process for city gas is 2500 km, 3 Furthermore, information on the reduction amount due to electricity that is certified by a non-fossil fuel certificate as being generated from a non-fossil fuel power source may be expressed in the same "electricity amount" as the usage amount.

[0020] It should be noted that steps S1 and S2 do not have to be executed in this order. Step S2 may be executed before S1. Steps S1 and S2 may be executed simultaneously.

[0021] In step S3, the total carbon dioxide emission amount U and the total reduction amount R from all the energy sources used in the production line 4 within a predetermined period are calculated. In this embodiment, the "annual usage amount" and the "CO2 reduction amount" for each "energy source" in Table 1 are read from the memory 34. In the embodiment of Table 1, the "CO2 emission coefficient" for each "energy source" is further used in this calculation. This "CO2 emission coefficient" is a value obtained, for example, from the "Ministerial Ordinance on Calculation of Greenhouse Gas Emissions Associated with the Business Activities of Specified Emitters" (Ministry of Economy, Trade and Industry, Ministry of the Environment), and is input in advance to the management computer 6 from an input device, for example, and stored in the memory 34. The carbon dioxide emission amount for each energy source is obtained by multiplying the "annual usage amount" for each energy source expressed in appropriate units by the "CO2 emission coefficient". By adding these together, the total carbon dioxide emission amount U from all the energy sources used in the production line 4 is calculated.

[0022] Furthermore, the "CO2 reduction amount" of each energy source is added up to calculate the total carbon dioxide reduction amount R. When information on the carbon dioxide reduction amount is stored other than the reduction amount in mass units, such as the amount of city gas reduction or the amount of electricity reduction, it is converted to the "CO2 reduction amount" in mass units using the aforementioned "CO2 emission coefficient," and then the total carbon dioxide reduction amount R is calculated.

[0023] Table 1 also calculates the total carbon dioxide emissions T and ratio R / T from all energy sources used in production line 4 when no carbon dioxide reduction is performed. The total emissions T when no carbon dioxide reduction is performed is the sum of the total emissions U and the total reduction R. The ratio R / T is called the "carbon dioxide reduction rate." In the example of Table 1, the ratio R / T is expressed in %, and the value is 8.7%.

[0024] [Table 1]

[0025] In step S4, the type and amount of low-CO2 steel in the shipped steel are determined based on the total amount of carbon dioxide emissions U and the total reduction amount R. In this embodiment, the shipped steel is the same as the reference steel. In other words, the steel manufactured during the aforementioned specified period is the shipped steel. The steel manufactured during the aforementioned specified period is classified into "one or more types Ki with a reduction ratio of carbon dioxide emissions during manufacturing of ni," and the mass mi of each type Ki is determined. In this case, the ratio ni and the mass mi are calculated by the sum of (ni x mi / M) for all types Ki when the total mass of steel manufactured during the specified period is M. Σ(ni×mi / M) is determined so as to be the reduction rate R / T. For example, when the total mass M is 1000kt and the ratio R / T is 8.7%, in the first example, the steel material is Type K1: Proportion n1=0%, Mass m1=913kt Type K2: proportion n2=100%, mass m2=87kt They are classified into two types: In the second example, the steel Type K1: Proportion n1=0%, Mass m1=826kt Type K2: proportion n2=50%, mass m2=174kt may be classified into two types. Furthermore, in the third example, the steel Type K1: Proportion n1 = 8.7%, Mass m1 = 1000kt The classification rules may be input in advance, for example, from an input device, and stored in the memory 34. The classification rules may be input in advance, for example, from an input device, and stored in the memory 34.

[0026] In step S5, the management computer 6 acquires quality information on the manufactured steel material from the production line 4 via the communication interface 36. The quality information may include, for example, the composition of the steel material, mechanical test results, and visual inspection results. Note that step S5 may be performed before any of steps S1 to S4, or may be performed simultaneously with any of steps S1 to 4. Step S5 may be performed before step S6.

[0027] In step S6, the inspection certificate 7, which includes information on the reduction in CO2 emissions of the steel product and quality information on the steel product, is output to the output device 30. The inspection certificate 7 may be sent as electronic data to another system via the network 26. An example of the inspection certificate 7 is shown in FIG. 4. This is a mill sheet for steel product type K2 in the second example described above. For this steel product, the proportion n2=50%, so the information on reduction in CO2 emissions reads, "This steel product has reduced CO2 emissions by 50%."

[0028] As described above, in this low-CO2 steel selection method, the type and amount of low-CO2 steel are selected for shipped steel based on the total amount of carbon dioxide emissions U and the total reduction amount R emitted in a steel production line 4 during a specified period. This method makes it possible to select low-CO2 steel taking into consideration the energy sources used in various processes in the production of steel, such as the steelmaking process and rolling process 16.

[0029] This method for determining low-CO2 steel products takes into account energy sources other than electricity, such as gas and oil, used in the production of steel products, and calculates the total carbon dioxide emissions U and total reduction R. This method makes it possible to determine low-CO2 steel products that take into account the various energy sources used in the production of steel products.

[0030] This method for creating the inspection certificate 7 for steel products makes it possible to easily create the inspection certificate 7 that includes information on the quality of the steel product and information on low CO2 emissions.

[0031] In another embodiment of the method for determining low-CO2 steel, in step S4, the ratio (T / M) of the total amount of carbon dioxide emissions T in the case where carbon dioxide reduction is not performed to the total mass M of the produced steel is calculated. This is the amount of carbon dioxide emissions per unit mass of steel, and is called the "CO2 intensity G." The type Ki, which has the proportion ni and mass mi, is calculated by the sum of (ni x mi x G) for all types Ki. Σ(ni×mi×G) is determined so that it is the total carbon dioxide reduction amount R. In this method as well, the type and amount of low-CO2 steel are determined based on the total carbon dioxide emission amount U and the total reduction amount R.

[0032] FIG. 5 shows an example of the creation of an inspection certificate 7 according to another embodiment. In this embodiment, the amount of carbon dioxide emitted per unit mass in the production of the steel product is recorded. This can be calculated from ni and mi above. For example, in the case of steel product type K2 in the second example above, (n2×m2 / M) / (R / T)=100%, which shows that the entire reduction rate R / T is attributable to the contribution of steel product type K2. In other words, the total carbon dioxide reduction amount R is entirely attributable to steel product type K2. The carbon dioxide emission amount of this steel product is calculated from the emission amount calculated from the mass ratio. T×(m2 / M) R subtracted from T×(m2 / M)-R Dividing this by the mass m2 gives the carbon dioxide emission per unit mass of type K2.

[0033] The information on low CO2 emissions to be recorded on the inspection certificate 7 is not limited to the carbon dioxide reduction rate and the amount of carbon dioxide emissions per unit mass. For example, the amount of carbon dioxide reduction may be recorded.

[0034] In the above-mentioned embodiment, the reference steel and the shipped steel are the same. In further other embodiments, the reference steel and the shipped steel may be different. For example, low-CO2 steel may be determined by using steel manufactured in the current year as the shipped steel based on the total carbon dioxide emission U and the total reduction amount R of the reference steel manufactured in the previous year. Low-CO2 steel may be determined by using a part of the steel manufactured in the previous year and steel manufactured in the current year as the shipped steel based on the total carbon dioxide emission U and the total reduction amount R of the reference steel manufactured in the previous year. Of course, a steel used as a reference steel to determine the low-CO2 steel of a shipped steel cannot be used as a reference steel for another shipped steel.

[0035] Even if the reference steel and the shipped steel are not the same, steps S1-S4 are executed in determining the low CO2 steel. In step S1, the management computer 6 acquires from the production line 4 via the communication interface 36 the types and amounts of energy sources used in all production lines 4 when producing the reference steel. In step S2, the management computer 6 acquires information on the amount of carbon dioxide reduction via the communication interface 36 and stores this information in the memory 34. In step S3, the total amount of carbon dioxide emissions U and the total reduction amount R from all energy sources used in the production line 4 in the production of the reference steel are calculated.

[0036] In step S4, the type and amount of low-CO2 steel in the shipped steel are determined based on the total amount of carbon dioxide emissions U and the total reduction amount R. In this step, the shipped steel is classified into "one or more types Ki with a reduction ratio of carbon dioxide emissions during manufacturing of ni," and the mass mi of each type Ki is determined. When the total mass of the reference steel is Mb and the total mass of the shipped steel is Mo, the ratio ni and mass mi are determined to satisfy the following formula: Σ(ni×mi / Mo)=(R / T)×(Mb / Mo) For example, if the total mass Mb of the reference steel is 1000kt, the ratio R / T is 8.7%, and the total mass Mo of the shipped steel is 2000kt, in the first example, the steel is Type K1: Proportion n1=0%, Mass m1=1913kt Type K2: Proportion n2=100%, mass m2=87kt They are classified into two types: In the second example, the steel Type K1: Proportion n1=0%, Mass m1=1826kt Type K2: proportion n2=50%, mass m2=174kt may be classified into two types. Furthermore, in the third example, the steel Type K1: Proportion n1 = 4.35%, Mass m1 = 2000kt may be classified into one type.

[0037] In the above-described embodiment, the reference steel is a steel product manufactured in a predetermined continuous period. The reference steel does not have to be a steel product manufactured in a predetermined continuous period. For example, the reference steel may be a steel product manufactured in January and a steel product manufactured in March. The reference steel may be a steel product manufactured in the first week of January and a steel product manufactured in the fourth week of January. The reference steel may be selected so that the CO2 emissions and the CO2 reductions due to its manufacture can be calculated.

[0038] As mentioned above, the amount of CO2 reduced by purchasing non-fossil certificates is used to calculate the "CO2 emissions" and "CO2 reductions" when manufacturing the reference steel. The purchase period of non-fossil certificates used to calculate the "CO2 emissions" and "CO2 reductions" when manufacturing the reference steel does not have to match the actual manufacturing period of the reference steel. For example, the "CO2 emissions" and "CO2 reductions" from non-fossil certificates purchased this year may be allocated to the calculation of the "CO2 emissions" and "CO2 reductions" of the reference steel manufactured in the previous year. The "CO2 emissions" and "CO2 reductions" from non-fossil certificates purchased in the previous year and this year may be allocated to the calculation of the "CO2 emissions" and "CO2 reductions" of the reference steel manufactured in the previous year. Naturally, once the CO2 reduction amount from a non-fossil certificate has been allocated to the calculation of the "CO2 emissions" and "CO2 reduction amount" of a benchmark steel product, it cannot be used to calculate the "CO2 emissions" and "CO2 reduction amount" of other benchmark steel products.

[0039] As described above, in this embodiment, a low CO2 steel product can be determined by taking into consideration various processes in the manufacture of the steel product and various energy sources used in the manufacture of the steel product. From this, the superiority of this embodiment is clear.

[0040] [Disclosure items] The following section discloses preferred embodiments.

[0041] [Item 1] A method for determining a low CO2 steel material by using a computer including a controller, a storage device, and a communication interface, and operating the controller with a program stored in the storage device, comprising: acquiring information on the type and amount of energy source used in the steel production line when producing the reference steel product via the communication interface and storing the information in the storage device; acquiring information on the amount of carbon dioxide reduction via the communication interface and storing the information in the storage device; A step of reading out the information on the type and amount of energy source used and the information on the carbon dioxide reduction amount from the storage device, and calculating the total carbon dioxide emission amount U and the total reduction amount R in the production line when the reference steel material is produced based on the information; and A step of determining the type and amount of low-CO2 steel for shipped steel based on the total emission amount U and the total reduction amount R. A method for determining low CO2 steel, including:

[0042] [Item 2] 2. The method for determining low CO2 steel according to item 1, wherein the energy source includes electricity, gas and oil.

[0043] [Item 3] 3. The method for determining a low CO2 steel product according to item 1 or 2, wherein the total carbon dioxide emission amount U includes the amount of carbon dioxide emitted in a steelmaking process and a rolling process.

[0044] [Item 4] When the amount of the reference steel is Mb, the amount of the shipped steel is Mo, and the sum (U+R) of the total emission amount U and the total reduction amount R is T, the step of determining the type and amount of the low CO2 steel is as follows: A method for determining low CO2 steel according to any one of items 1 to 3, wherein the shipped steel is classified into one or more types Ki having a carbon dioxide reduction ratio ni, and the reduction ratio ni and the mass mi of each type Ki are determined so as to satisfy the following formula. Σ(ni×mi / Mo)=(R / T)×(Mb / Mo)

[0045] [Item 5] 5. The method for determining a low CO2 steel material according to any one of items 1 to 4, wherein the reference steel material and the shipped steel material are the same.

[0046] [Item 6] A method for creating an inspection certificate for a steel product by using a computer including a controller, a memory, and a communication interface, and operating the controller according to a program stored in the memory, comprising: acquiring information on the type and amount of energy source used in the steel production line when producing the reference steel product via the communication interface and storing the information in the storage device; acquiring information on the amount of carbon dioxide reduction via the communication interface and storing the information in the storage device; acquiring quality information of the steel material produced on the production line via the communication interface and storing the information in a pre-storage unit; A step of reading out the information on the type and amount of energy source used and the information on the carbon dioxide reduction amount from the storage device, and calculating the total carbon dioxide emission amount U and the total reduction amount R in the production line when producing a reference steel product based on the information; A step of determining the type and amount of low CO2 steel for the shipped steel based on the total emission amount U and the total reduction amount R; and A step of outputting an inspection certificate for the steel material based on the quality information of the steel material and the type and amount of the low CO2 steel material. How to prepare inspection certificates for steel products, including: [Industrial Applicability]

[0047] The above-described determination of low CO2 steel can be applied to various steels. [Explanation of symbols]

[0048] 2. Materials manufacturing facilities 4. Production line 6. Management Computer 7. Inspection certificate 8. Molten steel 10...steel bar 12...Dissolution process 14. Casting process 16. Rolling process 18. Inspection process 20. Electric furnace 22. Continuous Casting Machine 24. Bloom 26 Network 28 Input device 30 Output device 32...Controller 34...Memory 36 Communication Interface

Claims

1. A method for determining a low CO2 steel material by using a computer including a controller, a memory, and a communication interface, and operating the controller with a program stored in the memory, comprising: acquiring information on the type and amount of energy source used in the steel production line when producing the reference steel product via the communication interface and storing the information in the memory; acquiring information on the amount of carbon dioxide reduction via the communication interface and storing the information in the storage device; A step of reading out information on the type and amount of energy source used and information on the carbon dioxide reduction amount from the storage device, and calculating, based on the information, a total amount U of carbon dioxide emission and a total reduction amount R of carbon dioxide in the production line when the reference steel material is produced; and A step of determining the type and amount of low-CO2 steel for shipping steel based on the total emission amount U and the total reduction amount R. A method for determining low CO2 steel, comprising:

2. The method of claim 1 , wherein the energy sources include electricity, gas, and oil.

3. The method according to claim 1 or 2, wherein the total carbon dioxide reduction amount R includes the amount of carbon dioxide emitted in a steelmaking process and a rolling process.

4. When the amount of the reference steel is Mb, the amount of the shipped steel is Mo, and the sum (U+R) of the total emission amount U and the total reduction amount R is T, in the step of determining the type and amount of the low CO2 steel, 3. The method according to claim 1 or 2, wherein the shipped steel products are classified into one or more types Ki having a carbon dioxide reduction ratio ni, and the reduction ratio ni and the mass mi of each type Ki are determined to satisfy the following formula. Σ(ni×mi / Mo)=(R / T)×(Mb / Mo)

5. The method according to claim 1 or 2, wherein the reference steel material and the shipped steel material are the same.

6. A method for creating an inspection certificate for a steel product by using a computer including a controller, a storage device, and a communication interface, and operating the controller according to a program stored in the storage device, comprising: acquiring information on the type and amount of energy source used in the steel production line when producing the reference steel product via the communication interface and storing the information in the memory; acquiring information on the amount of carbon dioxide reduction via the communication interface and storing the information in the storage device; acquiring quality information of the steel material produced on the production line via the communication interface and storing the information in a pre-storage unit; A step of reading out the information on the type and amount of energy source used and the information on the carbon dioxide reduction amount from the storage device, and calculating the total carbon dioxide emission amount U and the total reduction amount R of carbon dioxide in the production line when manufacturing a reference steel product based on the information; A step of determining the type and amount of low CO2 steel for the shipped steel based on the total emission amount U and the total reduction amount R; and A step of outputting an inspection certificate for the steel material based on the quality information of the steel material and the type and amount of the low CO2 steel material. How to prepare inspection certificates for steel products, including:

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