LCA (Life Cycle Assessment) environmental impact assessment method.

Abstract

To provide a simple and rapid environment assessment method for LCA.SOLUTION: The present invention is directed to a LCA environment assessment method having means for generating a process flow chart in a system boundary formed of a plurality of processes, means (inventory amount calculating means) for calculating an inventory amount in each process, means (process-unit operation degree environment stress factor amount calculating means) for an environment stress factor amount per unit operation degree of each process by using the inventory amount calculated by the inventory amount calculating means, means (process operation degree calculating means) for calculating a process operation degree based on an input and an output in each process, and means (system boundary internal environment stress factor amount calculating means) for calculating an environment stress factor amount in the system boundary by using the process unit operation degree stress factor amount calculated by the process unit operation degree environment stress factor amount calculating means and the process operation degree calculated by the operation degree calculating means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for quantifying the environmental impact assessment of LCA. [Background technology]

[0002] Life Cycle Assessment (LCA) is a method for quantitatively evaluating the environmental impact of a product or service throughout its entire lifecycle (resource extraction - raw material production - product production - distribution / consumption - disposal / recycling) or at specific stages thereof. By clarifying the environmental impact of a product or service throughout its entire lifecycle, LCA provides useful data for considering more environmentally friendly products and services. In recent years, global warming has become an urgent issue, and reducing carbon dioxide (CO2) emissions from human activities, which are a major cause of warming, has become a pressing issue. Attempts to reduce CO2 emissions from products and services using LCA are being actively pursued.

[0003] For example, FIG. 11 is a process flow diagram representing a life cycle (LC) system for a FAX (machine). A step that performs some processing is referred to as a process and represented by Ti (i = 1, 2, ...). There are 14 processes (T1 to T14) in the FAX life cycle. Each of these processes has input and output of an inventory (Ii: materials, parts, electric power, etc.). FIG. 11 shows 16 representative inventories (I1 to I16), but many other inventories also have input and output. A part of the process flow will be described below. In the printed wiring board process of process T3, an IC fabricated in the preceding process T1 is mounted on a printed board fabricated in the preceding process T2. In the FAX assembly process of next step T8, the printed wiring board, wire material, and molded housing resin product fabricated in preceding processes are assembled to produce a FAX machine (product). The FAX product is distributed and sold in the distribution process of T9. A user who has purchased the FAX product uses it in the use process of T10. The used FAX product is disposed of in the disposal process of T11; here, instead of being discarded, it is recycled in the recycling process of T12, a part enters the iron scrap process of T13, and the remainder enters the PS (plastic) recycling process of T14, and is completely recycled in the housing resin molding process, which is a preceding process of the FAX assembly process (T8). [Prior Art Documents] [Non-Patent Literature]

[0004] [Non-Patent Literature 1] (Non-Patent Literature 1) Simple calculation method for (LC-CO2) emissions by the Japan Electrical Manufacturers' Association. URL: www.jema-net.or.jp / Japanese / env / 02_LCA_tools / index.html [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Conventional LCA quantification, for example, in calculating CO2 emissions during the product manufacturing stage, involves examining the inventory used and emitted throughout the entire system, converting it to CO2 emissions, and dividing it by the number of units produced to calculate the CO2 emissions per unit of the target product. (Non-Patent Literature 1) However, in the case of manufacturing a product consisting of numerous processes, as shown in Figure 11, this method does not allow for effective reduction of CO2 emissions because it is not obvious how much CO2 each individual manufacturing process emits. Therefore, conventional LCA proceeds to the next step of examining the inventory of each individual process in the manufacturing stage and calculating the CO2 emissions for each process. However, this method calculates the CO2 emissions of each process by considering only the sequence of processes, making the calculation complicated, and often resulting in a large discrepancy between the sum of these emissions and the total CO2 emissions of the system, leading to a lack of overall consistency. As a result, it requires a great deal of time to recalculate many times, and in the end, data is often manipulated to suit the situation. The present invention provides a method that transforms the idea that LCA environmental impact assessments are complex and inaccurate by using foreground data within the target system. [Means for solving the problem]

[0006] This invention provides a simple and rapid means of performing an LCA (Life Cycle Assessment) by considering the inter-process and overall material flow within a system boundary (system boundary, the scope of the LCA). Specifically, this invention clarifies the flow of all processes within the target system boundary, solves a system of equations using a matrix with individual process utilization as variables to obtain all process utilizations at once, and quantifies the environmental load from the obtained process utilizations. Specifically, it has the following features. (1) The present invention is an LCA environmental impact assessment method comprising means for creating a process flow diagram in a system boundary composed of multiple processes, means for determining the inventory amount in each process (referred to as inventory amount calculation means), means for determining the amount of environmental stress factors per unit operating rate of each process using the inventory amount determined by the inventory amount calculation means (referred to as process unit operating rate environmental stress factor amount calculation means), means for determining the process operating rate based on the input and output of each process (referred to as process operating rate calculation means), and means for determining the amount of environmental stress factors in the system boundary using the amount of environmental stress factors in the process unit operating rate determined by the process unit operating rate environmental stress factor amount calculation means and the process operating rate determined by the operating rate calculation means (referred to as system boundary environmental stress factor amount calculation means).

[0007] (2) In addition to (1), the present invention is characterized in that the process flowchart is created by clarifying the sequence of all processes within a system boundary, the inventory amount in the inventory amount calculation means is the inventory amount per unit utilization in each process (referred to as the process unit utilization inventory amount), and the process unit utilization environmental stress factor amount calculation means is the sum of the function values ​​of the unit utilization inventory amount in each process, wherein the function is a conversion function used when converting the inventory amount to the environmental stress factor amount.

[0008] (3) In addition to (1) and / or (2), the present invention is characterized in that the process utilization calculation means includes means for creating a square matrix, means for creating a system of linear equations in which the product of a column vector with process utilization as a variable and the square matrix is ​​a constant vector including a system reference quantity, and means for finding the inverse matrix of the square matrix when the square matrix is ​​invertible, and the process utilization is obtained from the product of the inverse matrix and the constant vector, and the means for creating the square matrix includes means (referred to as means A) for creating an m × n matrix in the system boundary in which the number of rows is the number of input / output flows in each process (m) and the number of columns is the number of processes (n), and means for searching for loops from the process flow diagram and performing loop processing if a loop is found. The system is characterized by including a means (referred to as means B) for searching for nodes from a process flow diagram and performing node processing if a node is found, and the matrix prepared by means A is a coefficient matrix with the input / output unit activity of each process as coefficients, where the input / output unit activity of the process is the input / output of the process in terms of the process unit activity, the loops in means B are translational and / or cyclic, and the loop processing in means B is characterized by increasing the number of columns in the matrix prepared by means A by G if there are G loops, and furthermore, the nodes in means C are branching and / or merging, and the node processing in means C is characterized by increasing the number of rows in the matrix prepared by means A by H if there are H processes involved in the node.

[0009] (4) In addition to (1) to (3), the present invention relates to the means for calculating the amount of environmental stress factors within the system boundary, The amount of environmental stress factors within the system boundary is the sum of the amounts of environmental stress factors in each process across all processes, and the amount of environmental stress factors in each process is characterized by being obtained by multiplying the process unit operating rate environmental stress factor amount of each process by the process operating rate of each process. (5) The present invention relates to an LCA environmental impact assessment method by allocation in a system boundary producing multiple products, characterized in that the amount of environmental stress factors within the system boundary for each product is obtained by multiplying the amount of environmental stress factors within the system boundary described in (4) when each product is produced individually by a weighting coefficient, and the amount of environmental stress factors within the system boundary in a system boundary producing multiple products is the sum of the amounts of environmental stress factors within the system boundary for each product, characterized in that the weighting coefficient can be determined such that the equation holds, since the amount of environmental stress factors within the system boundary in a system boundary producing multiple products is also the amount of environmental stress factors within the system boundary described in (4) when multiple products are produced. [Effects of the Invention]

[0010] This invention is a method that quantifies environmental load as an amount of environmental stress factors by creating a system of linear equations using matrices and obtaining the solution as the operating rate of each process within the system boundary. Therefore, it is simple and allows for a quick estimation of environmental load. Consequently, environmental impacts can be rapidly evaluated using LCA. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a flowchart illustrating the means and method for determining the amount of environmental stress factors in the life cycle assessment (LCA) according to the present invention. [Figure 2] Figure 2 shows a simple process flowchart of two processes connected in serial order, and the matrix created based on it. [Figure 3] Figure 3 is a process flowchart showing an example of a node. [Figure 4] Figure 4 shows a method for searching for and processing nodes (branching, merging) when they are present. [Figure 5] Figure 5 shows a process flowchart illustrating an example of a loop, as well as a diagram showing the loop search and processing steps. [Figure 6]Figure 6 shows another example of a loop (cycle, translation). [Figure 7] Figure 7 shows another example of a process flow diagram that includes nodes and loops. [Figure 8] Figure 8 shows an example of a product manufacturing process (process flow diagram). [Figure 9] Figure 9 schematically shows the input and output states of the inventory quantity xij in process Ti. [Figure 10] Figure 10 shows a system of equations using the coefficient matrix in the process flow diagram shown in Figure 8. [Figure 11] Figure 11 is a process flow diagram representing the lifecycle (LC) of a fax machine. [Figure 12] Figure 12 shows the data sheet (1) for calculating the amount of environmental stress factors. [Figure 13] Figure 13 shows the data sheet (2) for calculating the amount of environmental stress factors. [Figure 14] Figure 14 shows the results for the amount of environmental stressors. [Figure 15] Figure 15 shows the application of the present invention when allocating environmental burden during the production of two products. [Modes for carrying out the invention]

[0012] Life Cycle Assessment (LCA) is a method for quantitatively evaluating the environmental impact of a product or service throughout its entire lifecycle (resource extraction - raw material production - product production - distribution / consumption - disposal / recycling) or at specific stages thereof. Environmental impact refers to anything that affects the environment, and these can include various substances (e.g., CO2, NOx, SOx) and energy, which are also referred to as environmental stressors or environmental load factors in this invention. This invention provides a means to easily and simultaneously determine the amount of environmental stressors (referred to as the amount of environmental stressors) that affect the environment within a target system boundary. The amount of environmental stressors is, for example, the amount of CO2 or NOx generated within the system boundary, and can also be considered as the degree of environmental impact (amount of environmental impact).

[0013] Figure 8 shows an example of a product manufacturing process (process flow diagram). The process shown in Figure 8 consists of five steps (called processes). Products manufactured in process T3 (flow item input / output (quantity) d), products manufactured in process T4 (flow item input / output (quantity) e), and products manufactured in process T5 (flow item input / output (quantity) f) are received, and a portion of them is processed in process T1 (flow item input / output (quantity) b) to produce an item (flow item input / output (quantity) a), which is then sent out of the system (or to the next process) as product M (item quantity Q: system standard quantity). The system standard quantity is the item quantity corresponding to the functional unit of the system. The rest is processed in process T2 (flow item input / output (quantity) c). Products manufactured in processes T3, T4, and T5 are the same item, and the items input to processes T1 and T2 are also the same, so this is called flow (item) m1. Also, what is output from process T1 is called flow (item) m0. In other words, m0 and m1 represent goods exchanged between processes. Here, goods include not only ordinary products but also energy and services, and are the subject of economic activity whether paid or free. In addition to goods exchanged between processes as shown in Figure 8, there are also goods exchanged within each process as shown in the inventory in Figure 9. Let p1 to p5 be the process utilization levels (a quantity representing how much the system is operational relative to a unit of utilization) in processes T1 to T5, respectively. Let α, δ, ε, and φ be the flow item input / output (quantity) per unit of output utilization (for example, equivalent to utilization level 1) in processes T1, T3, T4, and T5, respectively. Let β and γ be the flow item input / output (quantity) per unit of input utilization (process unit of utilization input / output) in processes T1 and T2, respectively. Then a = α × p1, b = β × p1, c = γ × p2, d = δ × p3, e = ε × p4, f = φ × p5, and b + c = d + e + f. Also, a = Q.

[0014] Figure 9 schematically shows the input and output states of inventory quantity xij in individual process Ti. Figure 9 shows the flow of manufacturing intermediate product 2 by processing intermediate product 1 in process Ti, and in this process processing, the input inventory quantity xij related to the environmental burden on the process is input and output. Here, j represents the inventory (type). For example, j is all inputs or outputs such as resources, parts, energy (electricity, heat, etc.), and materials. In this application, inventory quantity xij is the amount of inventory j required (or generated) per unit of operation of process Ti (also called the unit operation inventory quantity xij). For example, it is the amount of inventory required (or generated) to manufacture one unit (unit, weight, etc.) of product 2. Alternatively, it can be viewed from the input side. For example, it is the amount of inventory required (or generated) to process product 1. If process Ti is an intermediate process, it may also be the amount of inventory required (or generated) to manufacture one unit (unit, weight, etc.) of the final product. Alternatively, this unit capacity inventory (quantity) can be calculated by dividing the total amount of inventory used or discharged by the factory, etc., by the total production volume, assuming that the entire factory is considered as a single process.

[0015] In LCA, each inventory needs to be converted into an amount of something that affects the environment (environmental stressor k). If we denote this conversion function (or transformation function) as fk(x), then the amount of environmental stressor per unit utilization (e.g., utilization level 1) in process Ti for inventory j is fk(xij). For example, this means that the amount of environmental stressor (e.g., k is CO2) related to inventory j (coal) per unit utilization in process Ti is fk(xij). Note that the conversion function naturally changes depending on the type of environmental stressor, and generally fk and fk+i (where k and k+i are different environmental factors) are different functions.

[0016] In this process Ti, the flow item input (quantity) per unit of operation on the input side of intermediate product 1 (this is called the process unit operation quantity (input)) is π i, the flow article output (quantity) per unit operation degree on the output side <this is referred to as process unit operation quantity (output)> is σ i is represented by , and the process operation degree (a degree indicating how much the process Ti has operated relative to the unit operation quantity) in process Ti is p i . Let the inventory amount per unit operation degree of inventory J in this process Ti (i=1~5) be x ij , then the environmental stress factor amount per unit operation degree from inventory j is a function of the unit operation degree inventory amount x ij . For example, let f be the function for converting material A, which is inventory j used in the process, into an environmental stress factor amount (e.g., CO2 amount) kj (a function related to inventory j), then the inventory amount per unit operation degree of material A, which is inventory j, is x ij {=x i (material A)}, and the environmental stress factor amount (e.g., CO2 amount) per unit operation degree of material A, which is inventory j, is f kj (x ij ). The same applies to other inventories j in process Ti.

[0017] Let the k-th environmental stress factor amount per unit operation degree be b ki (i=1~5) (where k indicates (the type of) environmental stress factor, e.g., CO2, SOx, NOx), then b ki is the sum of function values of the inventory amount per unit operation degree (referred to as process unit operation degree inventory amount) x ij in process Ti, and is given by Equation 1. (Here, j is the type of inventory, and the sum of function values of all unit operation degree inventory amounts in process Ti is taken.) Furthermore, since different inventories have different conversion functions, functions such as f kj and f k(j+1) are generally not the same. That is, Equation 1 is b ki =f k1 (x i1 )+f k2 (x i2 )+····+f kn (x in ), and fk1 ,f k2 , , , f kn These are not the same function. (Formula 1)

number

[0018] At this time, the amount of environmental stress factors in process Ti (i=1~5) is b ki ×p i Therefore, the total amount of environmental stress factors Z for the entire system boundary shown in Figure 8 is... k This is given by Equation 2. For a system boundary with n processes, it becomes a sum over n processes. (Formula 2)

number

[0019] In the above equation, the unknown variable is the process utilization pi. The other values ​​(α, β, ..., xij) are obtained in advance as basic data for each process, and Q is obtained as the output (output quantity) of the entire system. Q is a system reference quantity and a physical quantity corresponding to the functional unit of the system (boundary). Also, bki can be calculated in advance. If the input / output (quantities) (a, b, ...) of a certain process are known, the utilization rate can be calculated individually from the above equation (for example, a = αpi, ...), but this needs to be done for each process, which is time-consuming and complicated. This invention makes it possible to obtain the utilization pi of all processes within the system boundary in one go using a computer and a system of linear equations using a coefficient matrix.

[0020] Figure 1 is a flowchart illustrating the means and method of the Life Cycle Assessment (LCA) of the present invention (for determining the amount of environmental stress factors). In the present invention, the scope (system boundary) of the LCA is first defined. It is decided whether to cover the entire process from raw material extraction to disposal and recycling of the product, or to cover a specific scope, such as from procurement of parts and materials to product shipment. All processes within that system boundary are listed, and all inventory is clearly defined for each process. Then, a process flowchart (process diagram) is created as shown in Figure 11. If the cause-and-effect relationships of individual processes are clearly defined, the relationship between the process flowchart and the input / output of the inventory can be automatically represented. It is possible to create it manually, but if there are many processes, it becomes complex and cumbersome, so it is better to use coded automated calculations.

[0021] The inventory for each process (inputs and emissions related to the environmental burden of each process: raw materials, materials, energy, parts, products, etc.) is quantitatively acquired, the inventory items are entered, and the amount of environmental stress factors per unit of process operation for each process (environmental stress factor k: CO2, NO) is calculated. X , SO XThe amount of (TMR, various emissions, various wastes, etc.) is determined. For example, with respect to the environmental stress factor k, in process Ti, the amount of environmental stress factor (bki) per unit of process operating capacity of various (j) inventories (process unit operating capacity inventory amount xij) is the sum of functions of xij {bki = Σfkj(xij) (summary over j)}, as shown in (Equation 1).

[0022] Next, for items (called flows) exchanged between processes, data is acquired on the input / output (quantity) of the flows for each process unit utilization level of each process. Based on the number of processes (Ti) (Timax), the number of flow items (mL) (mLmax), and the output (item quantity or service quantity) corresponding to the functional unit of the system in the system boundary (system reference quantity: Q), a system of linear equations is created for the entire system boundary, with the process utilization level (pi) in each process (Ti) as the variable. For example, if a system of linear equations is created showing the relationship between the process utilization level pi and the input / output (α, β, γ, ...) per process unit utilization level of process Ti for each inter-process flow item (mL: L=1, 2, 3...), the coefficient matrix is ​​denoted by [A], and the relationship between the variable column vector (p) composed of each process utilization level pi and the constant vector (Q) composed of the system reference quantity Q is expressed as [A](p)=(Q). The coefficients of this system of linear equations become a coefficient matrix of (mLmax rows × Timax columns). L If the (corresponding to) and columns (corresponding to pi) are equal, and the rank of the matrix is ​​equal to the number i, then [A] is a square matrix and is invertible if <[A]'s determinant |A|≠0>, and pi can be obtained by matrix calculation. That is, the inverse matrix of [A] is [A -1 If we set ] then (p) = [A -1 ](Q). If data is given to the computer, the matrix [A] is automatically created, so the computer can easily represent and determine whether the matrix [A] is a square matrix and whether the matrix [A] is invertible, and if the matrix [A] is invertible, then the inverse matrix [A -1 ] can be easily found, and (p) can also be easily found.

[0023] A necessary condition for a regular matrix is ​​that it must be a square matrix. If matrix [A] is not a square matrix, the next step is to check if there are loops or nodes in the process flow diagram. That is, the entire process flow diagram of the system boundary is surveyed to search for loops, and if there are loops, the loop processing is performed. For example, if there is one loop, one column is added to the coefficient matrix; if there are n loops, n columns are added to the coefficient matrix (column expansion). Next, the entire process flow diagram of the system boundary is surveyed to search for nodes, and if there are nodes, the node processing is performed. For example, if there is one node, and the number of processes involved in that node is n, the number of rows in the coefficient matrix is ​​increased by n-1 (row expansion). If there are multiple nodes, the number of processes involved in each node is checked, and row expansion is performed similarly. These loop search and loop processing and node search and node processing can be performed in a short time using a computer.

[0024] These searches and processes allow us to obtain a square matrix ([A]) as the coefficient matrix. In general, the determinant of [A] is |A|≠0, so the inverse of the determinant of [A] is ([A -1 Since there exists a ([A] is an invertible matrix), the system of equations <[A](p)=(Q)> can be solved as <(p)=[A -1 ](Q)>, in this way, the operating rate (p) of each process can be determined all at once. With respect to the environmental stress factor k, the sum of the amount of environmental stress factor per unit operating rate of each process (bki) based on the inventory of each process (Zk) for all processes within the system boundary (total amount of environmental stress factor for all processes) can be calculated as Zk = Σbki × pi (summary with respect to i), as shown in Equation 2.

[0025] Next, let's look at a concrete example. Figure 2 shows a simple process flowchart of two processes connected in seriality, and the matrix created based on it. As can be seen from Figure 2(a), the flow item m1 output from process T1 is input to process T2, processed in process T2, and output as flow item m0, obtaining the system reference quantity Q. Conversely, we can also consider m0 and m1 as the system reference quantity Q. p1 and p2 are the process utilization levels of processes T1 and T2, and α, β, and γ are the flow item input / output (quantity) per unit of process utilization. Following the flowchart shown in Figure 1, the number of processes Ti (Timax) is 2, and the number of flow items mL (mLmax) is 2, so a 2x2 square matrix is ​​obtained as the coefficient matrix [A] as shown in Figure 2(b). In general, the determinant |A|≠0, so the process utilization levels (p1, p2) can be determined. This completes the procedure shown in the flowchart in Figure 1. Furthermore, since there are no loops or nodes in this system boundary, proceeding with the steps ahead would yield the same result. From this, the total amount of environmental stressors (environmental load) Zk within the system boundary shown in Figure 2 can be obtained for each environmental load (environmental stressor) k.

[0026] Figure 3 is a process flowchart showing an example of a node. Nodes include merges and branches. Figure 3(a) is a simple flowchart where processes (Ti) are connected serially and there are no nodes. This is the case when many processes are followed in the same order as shown in Figure 2. That is, there is only one input and one output from one process to the next, m L Since the number of x and the number of pi are equal, a square (invertible) matrix can be constructed, and therefore it can always be solved.

[0027] Figure 3(b) shows an example with one node (branch), where the flow from one process branches into two processes. For example, this is the case when a part manufactured in process T1 is divided (branched) and used (processed) in the next two processes (T2 and T3). LThe number of θ is 2 (mLmax=2) and the number of processes is 3 (Timax=3). Since they are different (mLmax≠Timax), [A] is a 2x3 matrix, and therefore we cannot obtain the solution to (p) at this stage.

[0028] Figure 3(c) shows an example with two nodes (branching points), where two branches leading to two processes are connected. L The number of θ is 3 (mLmax=3) and the number of processes is 5 (Timax=5). Since they are different (mLmax≠Timax), [A] is a 3x5 matrix, and therefore we cannot obtain the solution to (p) at this stage.

[0029] Figure 3(d) shows an example where there is one node (branch), but it branches into three processes. L The number of θ is 2 (mLmax=2) and the number of processes is 4 (Timax=4). Since they are different (mLmax≠Timax), [A] is a 2x4 matrix, and therefore we cannot obtain the solution to (p) at this stage.

[0030] Figure 3(e) shows an example with one node (merging point), where the outputs from two processes merge. For example, this is the case when a part manufactured in process T1 is also manufactured in process T3, and then combined and used in process T2. L The number of θ is 2 (mLmax=2) and the number of processes is 3 (Timax=3). Since they are different (mLmax≠Timax), [A] is a 2x3 matrix, and therefore we cannot obtain the solution to (p) at this stage.

[0031] As shown in the examples above, nodes have both branching and merging. Figure 3(f) looks like a node, but is actually an example of something that is not a node. For example, consider a case where part A is manufactured in process T1 and by-product B is produced at the same time, and part A is used in the next process T2, and by-product B is used in the next process T3. LThe number of θ is 3 (mLmax=3), and the number of processes is 3 (Timax=3). Since they are equal (mLmax=Timax), [A] is a 3x3 square matrix (assuming the determinant of [A] |A|≠0), and thus we can obtain the solution to (p) at this stage.

[0032] Figure 4 shows a method for searching for and processing nodes (branching, merging) when nodes are present. The operating rates of processes T1, T2, and T3 (how many times the unit operating rate they are) are shown as p1, p2, and p3, respectively. The Greek letters (α, β, γ, δ, ε) represent the input / output (quantity) of flow items per process operating standard (unit operating rate) (referred to as (process) unit (input / output) operating rate). The English letters (a, b, c, d, e) represent the input / output for each flow item between processes. For example, a=α×p1, b=β×p2, c=γ×p1, d=δ×p2, and e=ε×p3.

[0033] Figure 4(a) is the same process flowchart as Figure 3(e), but in the case of merging. The matrix before node search is a 2x3 matrix, as shown in the system of equations on the left side of Figure 4(a). When node search and processing are performed, there is one node and two processes merging to it, so the matrix [A] gains a third row, as shown in the system of equations on the right side of Figure 4(a). That is, one row is added. Here, from the balance of flow item input and output, δe=δ×e and εd=ε×d are obtained. By performing node search and processing using the balance relationship of process item input and output in this way, the matrix [A] becomes a 3x3 square (invertible) matrix, so the system of equations [A](p)=(Q) can be solved and the solution to (p) can be obtained.

[0034] Figure 4(b) is the same process flowchart as Figure 3(b), but with branching. The matrix before node search is a 2x3 matrix, as shown by the system of equations on the left side of Figure 4(b). When node search and processing are performed, there is one node and two processes branching from it, so the matrix [A] gains a third row, as shown by the system of equations on the right side of Figure 4(b). That is, it gains one row. Here, γd = γ × d and δc = δ × c. In this way, by performing node search and processing, the matrix [A] becomes a 3x3 square (invertible) matrix, so the system of equations [A](p) = (Q) can be solved and the solution to (p) can be obtained.

[0035] As described above, when there are nodes (branching, merging), n-1 rows are added for each n node in the process Ti. This can also be described as increasing the number of equations in the system of linear equations by n-1. If there are multiple nodes, the same operation of adding rows is performed. Through this node search and processing, the matrix [A] becomes a square (invertible) matrix, so the system of linear equations [A](p)=(Q) can be solved, and the solution to (p) can be obtained. Note that in the case of Figure 4, there is no loop, so only the node search and processing needs to be performed.

[0036] Figure 5 shows a process flow diagram illustrating an example of a loop, and a diagram illustrating loop search and processing. Loops can be circular or parallel. All process flows shown in Figure 5 consist of four processes (T1, T2, T3, T4). Figure 5(a) is an example of a parallel loop. There are two possible flows from process T1: one enters process T2, and the flow from T2 enters T3. The other enters process T4, and the flow from T4 enters T3. However, the flows from T2 and T4 do not merge and enter T3. In other words, a parallel loop is a route in which multiple processes (T2 and T3 in Figure 5(a)) exit a preceding process (T1 in Figure 5(a)) and enter a subsequent process (T3 in Figure 5(a)), and one or more other processes may intervene between processes (between T2 and T3, and between T4 and T3 in Figure 5(a)).

[0037] m LThe number of items is 5 (mLmax=5) and the number of processes is 4 (Timax=4). Since they are different (mLmax≠Timax), [A] is a 5x4 matrix (without the 5th column indicated by the arrow in Figure 5(c)), so the solution to (p) cannot be obtained at this stage. Assigning the input / output of items per process operating standard (operating level 1) (called process unit operating quantity) α, β, γ, δ, ε, μ, φ, η, λ and the system standard quantity Q to each process Ti (i=1~4) as shown in Figure 5(b), then as described above, [A] becomes a 5x4 matrix (without the 5th column indicated by the arrow in Figure 5(c)). Now, assuming there is a stock S (stock quantity s) between the material flows of the translational loop, we add one column to matrix [A]. In this case, s comes in the last row of the column vector (p), and we set the last column of the corresponding row to 1. (In Figure 4(c), it is the 5th row and 5th column) As a result, [A] becomes a 5x5 square (invertible) matrix as shown in Figure 5(c), so the system of equations [A](p)=(Q) can be solved to obtain the solution for (p).

[0038] Figure 5(d) shows an example of a loop (cycle). There are two ways for flows to enter process T2: from processes T1 and T4. There are two ways for flows to exit process T2: one enters process T3 and the other enters process T4. The routes from process T4 to process T2 and from process T2 to process T4 form a loop. In this case, the loop (cycle) flows do not branch or merge with other flows. Note that one or more other processes may be intervened between processes T2 and T4, or between processes T4 and T2.

[0039] m L The number of processes is 5 (mLmax=5) and the number of operations is 4 (Timax=4). Since they are different (mLmax≠Timax), [A] is a 5x4 matrix (the matrix shown in Figure 5(f) without the 5th column indicated by the arrow), so we cannot obtain the solution to (p) at this stage.

[0040] If we assign the input / output of items per process operating standard (operating level 1) (called process unit operating quantity) α, β, γ, δ, ε, μ, φ, η, λ and the system standard quantity Q to each process Ti (i=1~4) as shown in Figure 5(e), then as described above, [A] becomes a 5x4 matrix (the matrix shown in Figure 5(c) without the 5th column indicated by the arrow). Now, assuming there is a stock S (stock quantity s) between the material flows of the cyclic loop (here, between T4 and T2), we add one column to matrix [A]. In this case, s comes in the last row of the column vector (p), and we set the last column of the corresponding row to 1. (5th row, 5th column in Figure 5(f)). As a result, [A] becomes a 5x5 square (invertible) matrix as shown in Figure 5(f), so the system of equations [A](p)=(Q) can be solved to obtain the solution for (p).

[0041] Figure 6 shows another example of a loop (circular, translational). Figure 6(a) shows a loop (translational), similar to Figure 5(a), but the flow from process T1 branches off and enters process T4, and the flow from process T4 and the flow from process T2 merge and input to process T3. In other words, the loop (translational) contains nodes (branching, merging). L The number of θ is 3 (mLmax=3) and the number of processes is 4 (Timax=4). Since they are different (mLmax≠Timax), [A] is a 3x4 matrix, and therefore we cannot obtain the solution to (p) at this stage.

[0042] Compared to the matrix shown in Figure 5(c), there are nodes (branching, merging), so m L The number of elements is two less (the matrix has two fewer rows). Here, by following the procedure shown in Figure 1, loop search and processing (increasing the number of columns by one because there is one loop) and node search and processing (increasing the number of rows by two because there are two nodes, each involving two processes), [A] becomes a 5x5 square (invertible) matrix, and thus the solution to (p) can be obtained.

[0043] Figure 6(b) shows a loop (cycle), similar to Figure 5(b), but the flow from process T2 branches off and enters process T4, and the flow from process T4 merges with the flow from T1 and enters process T2. L The number of θ is 3 (mLmax=3) and the number of processes is 4 (Timax=4). Since they are different (mLmax≠Timax), [A] is a 3x4 matrix, so we cannot obtain the solution to (p) at this stage. Compared to the matrix shown in Figure 5(f), there are nodes (branching, merging), so m L The number of elements is two less (the matrix has two fewer rows). Here, by following the procedure shown in Figure 1, loop search and processing (increasing the number of columns by one because there is one loop) and node search and processing (increasing the number of rows by two because there are two nodes and each involves two processes), [A] becomes a 5x5 square (invertible) matrix, and thus the solution to (p) can be obtained.

[0044] Figure 6(c) shows a loop (translation), similar to Figure 5(a), but the flow from process T4 merges with the flow from process T2 and inputs to process T3. In this case, m L The number of θ is 4 (mLmax=4), and the number of processes is 4 (Timax=4). Since they are equal (mLmax=Timax), [A] is a 4x4 square (invertible) matrix, and at this stage we can obtain the solution to (p). Compared to the matrix shown in Figure 5(c), there are nodes (confluences), so m L The number of elements is one less (the matrix has one fewer row). At this stage, matrix [A] is a square (invertible) matrix, so it is not necessary to perform loop search and processing or node search and processing. However, by deliberately following the procedure shown in Figure 1, loop search and processing (increasing the number of columns by one because there is one loop) and node search and processing (increasing the number of rows by one because there is one node and two processes are involved), [A] becomes a 5x5 square (invertible) matrix, and similarly, the solution to (p) can be obtained. In other words, the procedure shown in Figure 1 also holds in this case.

[0045] Figure 6(d) shows a loop (cycle), similar to Figure 5(b), but the flow from process T4 merges with the flow from process T1 and inputs into process T2. In this case, m L The number of is 4 (mLmax=4), and the number of processes is 4 (Timax=4). Since they are equal (mLmax=Timax), [A] is a 4x4 square (invertible) matrix, and at this stage we can obtain the solution to (p). Compared to the matrix shown in Figure 5(f), there are nodes (confluences), so m L The number of elements is one less (the matrix has one fewer row). At this stage, matrix [A] is a square (invertible) matrix, so it is not necessary to perform loop search and processing or node search and processing. However, by deliberately following the procedure shown in Figure 1, loop search and processing (increasing the number of columns by one because there is one loop) and node search and processing (increasing the number of rows by one because there is one node and two processes are involved), [A] becomes a 5x5 square (invertible) matrix, and similarly, the solution to (p) can be obtained. In other words, the procedure shown in Figure 1 also holds in this case.

[0046] Figure 6(e) shows a loop (translation), similar to Figure 5(a), but the flow from process T1 branches and inputs to processes T2 and T4. In this case, m L The number of is 4 (mLmax=4), and the number of processes is 4 (Timax=4). Since they are equal (mLmax=Timax), [A] is a 4x4 square (invertible) matrix, and at this stage we can obtain the solution to (p). Compared to the matrix shown in Figure 5(c), there are nodes (branching), so m L The number of elements is one less (the matrix has one fewer row). At this stage, matrix [A] is a square (invertible) matrix, so it is not necessary to perform loop search and processing or node search and processing. However, by deliberately following the procedure shown in Figure 1, loop search and processing (increasing the number of columns by one because there is one loop) and node search and processing (increasing the number of rows by one because there is one node and two processes are involved), [A] becomes a 5x5 square (invertible) matrix, and similarly, the solution to (p) can be obtained. In other words, the procedure shown in Figure 1 also holds in this case.

[0047] Figure 6(f) shows a loop (cycle), similar to Figure 5(b), but the flow from process T2 branches and inputs to processes T3 and T4. In this case, m L The number of is 4 (mLmax=4), and the number of processes is 4 (Timax=4). Since they are equal (mLmax=Timax), [A] is a 4x4 square (invertible) matrix, and at this stage we can obtain the solution to (p). Compared to the matrix shown in Figure 5(f), there are nodes (branching), so m L The number of elements is one less (the matrix has one fewer row). At this stage, matrix [A] is a square (invertible) matrix, so there is no need to perform loop search / processing or node search / processing. However, by deliberately following the procedure shown in Figure 1, and performing loop search / processing (adding one column because there is one loop) and node search / processing (adding one row because there is one node and two processes are involved), [A] becomes a square (invertible) 5x5 matrix, and similarly, the solution to (p) can be obtained. In other words, the procedure shown in Figure 1 also holds in this case.

[0048] As shown in Figures 6(c), (d), (e), and (f), when a node (branching, merging) is included in a loop (circulation, translation), m L There are cases where the number of steps (corresponding to the rank) and the number of processes (corresponding to variables) are the same, resulting in a regularity. In this case, the solution to (p) can be obtained at this stage. Of course, as described above, loop search and loop processing, and node search and node processing can also be performed according to the procedure shown in Figure 1.

[0049] Figure 7 shows another example of a process flow diagram that includes nodes and loops. There are five processes Ti (i=1~5). Some of the flow from processes T3, T4, and T5 is input to T1, and the rest is input to T2, and the flow output from process T1 becomes the system reference quantity (Q). Also, the output from process T2 is input to process T5. In the process flow diagram shown in Figure 7(a), m LThe number of (m0, m1, m2) is 3 (mLmax=3), and the number of processes is 4 (Timax=5). Since they are different (mLmax≠Timax), [A] is a 3x5 matrix, and therefore the solution to (p) cannot be obtained at this stage. Assigning the input / output of items per process operating standard (operating level 1) (called process unit operating quantity) α, β, γ, δ, ε, μ, φ, η, and the system standard quantity Q to each process Ti (i=1~5) as shown in Figure 7(a) or Figure 7(c), this 3x5 matrix becomes the one shown in Figure 7(b).

[0050] The process flow diagram in Figure 7(a) has one node, as shown in the process flow diagram in Figure 7(c). However, since this node includes a merge (flows from T3, T4, and T5) and a branch (flows to T1 and T2), it can be counted as two nodes. This merge is the confluence of flows from three processes, so it is necessary to consider the relationship (ratio) of the flows from each. If two relationships are known, the remaining relationship can be determined automatically (there are three processes related to the node), so two rows related to mL are added. Similarly, for the branch, since it is a branch to two processes, if one flow is known, the other flow can be determined (there are two processes related to the node), so one row related to mL is added. In general, when flows from n processes merge, n-1 rows are added, and when a flow branches to n processes, n-1 rows are also added. This is node processing. In the case of Figure 7, three rows are added to the matrix in Figure 7(b). That is, the number of rows within the frame indicated by V is increased, as shown in Figure 7(d).

[0051] In the process flow diagram shown in Figure 7, the loop is a cyclic route where the flow from process T2 inputs process T5, and there is one loop. Therefore, we add one column. That is, we add one column to matrix [A] assuming there is stock (stock amount s2) between the material flows of the cyclic loop. In other words, we increase the column within the frame indicated by U, as shown in Figure 7(d). At this time, s2 comes in the last row of the column vector (p), and we set the last column of the corresponding row to 1. (3rd row, 6th column in Figure 7(d)) ​​As a result, [A] becomes a 6x6 square (invertible) matrix, so the system of equations [A](p)=(Q) can be solved to obtain the solution to (p). In general, if there are n loops, we perform the operation of adding n columns. This is loop processing. Note that δe=δ×d, εe=ε×e, фf=ф×f, βb=β×b, and γc=γ×c.

[0052] Figure 10 shows a system of linear equations using the coefficient matrix in the process flow diagram shown in Figure 8. In the case where there are no loops in the process flow diagram of Figure 7, that is, in the process flow diagram shown in Figure 8, the coefficient matrix before loop search / processing and node search / processing is as shown in Figure 10(a), m L The number of θ is 2 (mLmax=2), and the number of processes is 5 (Timax=5). Since they are different (mLmax≠Timax), matrix [A] is a 2x5 matrix, so we cannot obtain the solution to (p) at this stage. Here, by following the procedure shown in Figure 1, we perform loop search and processing (there are no loops, so the number of columns does not increase) and node search and processing (there are two nodes, and since three processes are involved in one node (confluence), we increase the number of rows by two, and since two processes are involved in one node (branch), we increase the number of rows by one), so [A] becomes a 5x5 square (invertible) matrix as shown in Figure 10(b), and we can obtain the solution to (p).

[0053] In the process flow diagram of the FAX (machine) in Figure 11, there are 14 processes (T1~T14) and 14 mLs (m1~m14). At this stage, [A] is a 14x14 square (invertible) matrix, so the system of equations [A](p)=(Q) can be solved to obtain the solution for (p). However, there is one loop (a loop at m14 is found through loop search), so one column is added (loop processing), and there is one node (two processes (T4, T5) merge at m5 through node search), so one row is added (node ​​processing). Therefore, [A] is a 15x15 square (invertible) matrix, so the system of equations [A](p)=(Q) can be solved, and the solution for (p) can be obtained by performing loop search and processing and node search and processing. Even with a high-order matrix of 15 rows and 15 columns, the inverse matrix can be calculated in a short time using a computer. Thus, the present invention makes it possible to easily determine (p) even in a system boundary consisting of many processes, and to obtain the amount of environmental load (total amount of environmental stress factors) Zk for an environmental load (environmental stress factor) k.

[0054] FIGS. 12, 13 and 14 are diagrams (tables) showing the results of determining the amount of environmental stress factors using the present invention, based on a process flow diagram representing the life cycle (LC) of the FAX (machine) shown in FIG. 11. FIGS. 12 and 13 are examples of description on a data sheet showing inventory amounts and the like in each process. For example, in a printed wiring board assembly step (<printed wiring board> step in FIG. 11), inputs are received from two processes (IC manufacturing step and printed board manufacturing step). The product name (article / service name) from each process and its quantity (per unit operation degree) are described on the data sheet. Further, all inventory names and their quantities (per unit operation degree) in this printed wiring board assembly step are described on the data sheet. Also, the output of this printed wiring board assembly step enters the product assembly step (<FAX assembly> step in FIG. 11), and this product name (article / service name) and quantity (per unit operation degree) are described on the data sheet. The same applies to other processes. When these data are described (input) and calculated by a computer, the amount of environmental stress factors as shown in FIG. 14 can be obtained for each process. Here, the amount of CO2 and the amount of TMR (Total Material Requirement: total amount of involved substances) are shown as the environmental stress factor amounts. As described above, if the basic data in each process and the relationship between processes are known, the amount of environmental stress factors can be easily obtained using the present invention.

[0055] The present invention can also be applied to allocation when a plurality of products are output within a target system boundary. FIG. 15 is a diagram showing an example of application of the present invention to allocation of environmental load when two products a and b are produced. FIG. 15(a) is the process flow diagram. Product a (input / output amount ma) is produced from final process T1 (flow article input / output (amount) α per process unit operation degree), product b (input / output amount mb) is produced from final process T2 (flow article input / output (amount) β per process unit operation degree), and the system reference amount that receives these products is m. Further, one or more preceding processes exist before the final processes T1 and T2, and these processes are collectively referred to as a process group That is what they say.

[0056] Figure 15(b) shows a system of linear equations using the system-wide matrix (denoted as matrix [A]). p1, p2, ... are the process utilization levels of each process T1, T2, ... and the process group The matrix is ​​denoted by [B]. If this matrix [A] is a square matrix and invertible, then, as mentioned above, an inverse matrix exists, and the solution for the column vector (pi) can be obtained. Even if this matrix is ​​not a square matrix, it can be converted to a square matrix by performing nodal or loop processing, and if that square matrix is ​​invertible, the solution for the column vector (pi) can still be obtained. That is, the process activity pi (i=1,2,...) for each process T1, T2,... can be determined. Therefore, the total environmental load (environmental stress factor) (amount) Zk within this system boundary is Zk = Σ(bki·pi). (See Equation 1)

[0057] When two products, a and b, are produced, the total environmental load Zk can be allocated to the environmental load Zka, which is related only to product a, and the environmental load Zkb, which is related only to product b. That is, Zk = Wa·Zka + Wb·Zkb, where Wa and Wb are weighting coefficients for product a and product b, respectively. By applying the present invention, Zka and Zkb can also be determined as shown below.

[0058] The system of equations using matrices when each process within the system boundary produces only product a is shown in Figure 15(c). Here, p a i is the process utilization when only product a is produced in process Ti. This system of equations can be solved to obtain the column vector (p a We can obtain the solution to i). Similarly, the system of equations using matrices when each process in the system boundary produces only product b is shown in Figure 15(d). Here, p b i is the process utilization when only product b is produced in process Ti. This system of equations can be solved to obtain the column vector (p b We can obtain solution i).

[0059] From these results, the total environmental load Zka when producing only product a is given by Zka = Σ(bki·p a i) The total environmental load Zkb when producing only product b is given by Zkb = Σ(bki·p a i) Therefore, the total environmental load Zk of the system boundary is Zk = Wa·Σ(bki·p a i )+Wb·Σ(bki·p b i It can be expressed as ). Note that these weighting coefficients Wa and Wb can be determined according to the evaluation purpose of LCA, for example, by physical parameters or based on economic value (for example, sales). Also, the weighting coefficients Wa and Wb are Zk = Σ(bki·pi) = Wa·Zka + Wb·Zkb = Wa·Σ(bki·p a i) + Wb · Σ(bki · p a i) can be determined such that it holds. That is, Wa = {Σ(bki·pi) - Wb·Σ(bki·p a i)} / {Σ(bki·p a i)}

[0060] In summary, when allocating LCA for the production of multiple products within a system boundary, a system of linear equations is created using a matrix with the utilization rate of each process as a column vector when each product is produced individually. The utilization rate of each process for each product is then calculated, and the environmental load (amount of environmental stress factor) for each process is calculated using the calculated utilization rate of each product. The sum of these environmental loads for each process is the environmental load when each product is produced individually (environmental load of each product individually). The total environmental load within the system boundary is the sum of the environmental loads of each product individually, weighted for each product. (Figure 15(c), (d)) On the other hand, the total environmental load within the system boundary can also be given as the sum of the environmental loads of each process, calculated by creating a system of linear equations using a matrix with the utilization rate of each process as a column vector when multiple products are produced, calculating the utilization rate of each process, and then using the calculated utilization rate to calculate the environmental load of each process. (Figure 15(b))

[0061] As described above, the environmental load of the entire system can be determined by allocating (weighting) the environmental load of each product within the system boundary. While the above and Figure 15 describe the LCA allocation for two products, it goes without saying that the present invention can also be applied to the LCA allocation for each product when three or more products are produced.

[0062] According to the present invention, by introducing the concept of process utilization for each process within a system boundary, the amount of environmental factors in each process can be determined, and the environmental load within the system boundary (total amount of environmental stress factors) can be obtained as the sum of the amounts of environmental factors in each process. The product of a coefficient matrix, where the input / output per unit utilization of each process is the coefficient, and a column vector where the utilization of each process is the variable, becomes a constant vector containing a system reference quantity, which is the quantity of goods corresponding to the functional unit of the system. Therefore, if the coefficient matrix is ​​a square invertible matrix, the utilization of each process is the product of the inverse of this coefficient matrix and the constant vector containing the system reference quantity. If the coefficient matrix is ​​not a square matrix, an operation can be performed to make it a square invertible matrix, so ultimately the utilization of each process can be determined. The input / output per unit utilization of each process can be obtained as data. By inputting this data and the system reference quantity, the coefficient matrix can be easily created using a computer, and square regularization of this coefficient matrix can also be easily performed, so the utilization of each process can be determined all at once. As a result, the amount of environmental impact can also be determined, making it possible to conduct the LCA environmental impact assessment quickly and accurately. Furthermore, it goes without saying that the content described and explained in certain parts of this specification can be applied in a consistent manner to other parts not described therein. Moreover, the above embodiments are merely examples and can be modified in various ways without departing from the spirit of the invention, and it goes without saying that the scope of the present invention is not limited to the above embodiments. [Industrial applicability]

[0063] The LCA environmental impact assessment method of the present invention can also be applied to the entire supply chain, including raw material procurement, manufacturing, logistics, sales, and disposal.

Claims

1. A computer-based LCA environmental impact assessment method, In a system boundary composed of multiple processes, A means by which a computer creates a process flow diagram. A means by which a computer determines the inventory amount in each process (referred to as an inventory amount calculation means), A computer uses the inventory amount obtained by the inventory amount calculation means to determine the amount of environmental stress factors per unit operating rate of each process (referred to as the process unit operating rate environmental stress factor calculation means). A means (referred to as a process utilization calculation means) by which a computer determines process utilization (a degree representing how much each process was utilized relative to its unit utilization (flow item input / output per unit utilization)) based on the inputs and outputs of each process, and A means for determining the amount of environmental stress factors in a system boundary (referred to as the means for calculating the amount of environmental stress factors within a system boundary) using the amount of environmental stress factors in a process unit operating rate determined by the means for calculating the amount of environmental stress factors in a process unit operating rate and the amount of process operating rate determined by the means for calculating the amount of environmental stress factors in a system boundary. Includes, Hereinafter, the process utilization calculation means includes means for creating a system of linear equations that show the relationship between the process utilization of each process and the input / output per unit of process utilization, means for creating a square matrix from a coefficient matrix based on the system of linear equations, means for creating a system of linear equations in which the product of a column vector with process utilization as a variable and the square matrix is ​​a constant vector composed of system reference quantities, and means for finding the inverse matrix of the square matrix when the square matrix is ​​invertible, and the process utilization is obtained from the product of the inverse matrix and the constant vector, characterized in that a computer-executed LCA environmental impact assessment method.

2. The process flowchart was created by clarifying the sequence of all processes within the system boundary, and the inventory amount in the inventory amount calculation means is the inventory amount per unit utilization in each process (referred to as the process unit utilization inventory amount). The LCA environmental impact assessment method executed by a computer according to claim 1, characterized in that, in the process unit operating capacity environmental stress factor amount calculation means, the amount of process unit operating capacity environmental stress factor amount in each process is the sum of the function values ​​of the process unit operating capacity inventory amount, and the function for calculating the function value is a conversion function used when the inventory amount is converted into an environmental stress factor amount.

3. The means for creating a square matrix from the coefficient matrix is ​​to use the number of input / output flows in each process (m) as the number of rows in the system boundary, and the number of processes (n) The system is characterized by including means for creating an m x n matrix with the number of columns (referred to as means A), means for searching for loops from a process flowchart and performing loop processing if a loop is found (referred to as means B), and means for searching for nodes from a process flowchart and performing node processing if a node is found (referred to as means C), wherein loops include translational loops and circular loops, where a translational loop is when a flow enters multiple processes from one process, and the flows from those multiple processes enter a later process, where a circular loop is when a flow enters multiple processes from one process, and the flows from one of those multiple processes enter the other processes, furthermore, nodes include branching and merging, where branching is when a flow from one process inputs multiple processes, and merging is when flows (outputs) from multiple processes merge, and loop processing and / or node processing are processes that convert the coefficient matrix into a square matrix. The matrix obtained by means A is a coefficient matrix whose coefficients are the input / output unit utilization amount of each process, where the input / output unit utilization amount of the process is the input / output of the process in terms of the process unit utilization rate. The loop processing in method B involves increasing the number of columns in the matrix created by method A by G, if there are G loops. The knotting process in means C is a process that adds H-1 rows to the matrix in means A if there are H processes involved in the knotting. A computer-based LCA environmental impact assessment method according to claim 1 or 2, characterized in that it is a computer-based LCA environmental impact assessment method.

4. The LCA environmental impact assessment method executed by a computer according to any one of claims 1 to 3, characterized in that the means for calculating the amount of environmental stress factors within the system boundary is the sum of the environmental stress factors in each process for all processes, and the amount of environmental stress factors in each process is obtained by multiplying the process unit operating rate environmental stress factor amount of each process by the process operating rate of each process.

5. A computer-based LCA environmental impact assessment method for allocation (weighted distribution) within a system boundary for producing multiple products, wherein the amount of environmental stress factors within the system boundary for each product is obtained by multiplying the amount of environmental stress factors within the system boundary described in claim 4 for the case where each product is produced individually by a weighting coefficient, and the amount of environmental stress factors within the system boundary for a system boundary for producing multiple products is the sum of the amount of environmental stress factors within the system boundary for each product (the amount of environmental stress factors within the system boundary for a single product multiplied by a weighting coefficient).

6. The LCA environmental impact assessment method executed by a computer according to claim 5, characterized in that the weighting coefficient can be determined such that the equation holds, since the amount of environmental stress factors within a system boundary in a system boundary that produces multiple products is also the amount of environmental stress factors within a system boundary as described in claim 4 when multiple products are produced.

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