Interpreting Costing Results¶
After creating an Excel file for the route, as described in the previous section, the web application interface can be used to run the route costing algorithm to create a new dynamic Excel output file. The instructions for that process are provided on the main web application page, so they will not be repeated here. A lightly formatted output for our demo route (see previous section) is shown below. (Two columns are not being shown at the end of the file. Those simply contain the Materials and Reactions Notes, which were transferred unchanged from the input file.)
Calculated RMCs¶
Columns A-H (and J, if OPEX was used) are translated directly from the input tables with one important exception; the $/kg values for the two reaction products (cells E5, E7, and E10) are now the total raw material costs (RMCs) for those two compounds. The RMC for the route is $54.41/kg, which is the value for the overall product of the route (cell E10). All three of these cells are fully dynamic because they are stored in the cell as equations rather than hard-coded values. So changes in other parts of the worksheet should cause these values to be recalculated. (Keep in mind, though, that the original input file and this new output file are not connected in any way, so changes here will not be reflected in the input file.)
New Column Descriptions¶
Cost Step Column¶
A new column named “Cost step” has been added to this output. This column simply defines the reaction connectivity matrix. The values here are “Step” column values where the costs of particular materials are calculated. This is used by the costcalc algorithm to determine which reactions need to be used for calculating RMCs. Use this column to troubleshoot any unusual behavior in the costing output; otherwise, this column can be removed for clarity. A common error here may be if a reaction product is not the final compound in any particular reaction. The “Cost step” matrix is determined assuming that the final reaction compound is the product.
Per kg Rxn Columns¶
The values in Excel columns K-M are per 1 kg of reaction product, in that they should be interpreted on a per reaction basis and not for the entire route. Brief descriptions of these columns are below.
kg/kg rxn: These values are the number of kgs that are needed for each reagent/solvent in order to make 1 kg of reaction product. Notice that the reaction product does not have a number here because of the assumed value of 1 kg.
RM cost/kg rxn: These are the costs ($/kg) for each reagent/solvent that would be needed to make 1 kg of reaction product. This is simply the kg/kg rxn column multiplied by the $/kg column. The sum of these values would be the RMC for each reaction product and is the value in the product cell for this column.
% RM cost/kg rxn: These are the RM cost/kg rxn expressed as percentages of the RMC for the reaction product. In other words, this is the RM cost/kg rxn column values divided by the reaction product RMC. For each individual reaction, these values should add up to 100%.
Per kg Prod Columns¶
The values in Excel columns N-P are per 1 kg of route product, so these values should be interpreted for the entire route. Brief descriptions of these columns are below.
kg/kg prod: The number of kgs needed for each reagent/solvent in order to synthesize 1 kg of the final product of the route. The 1 kg of final product is not included in this column.
RM cost/kg prod: The RM cost contribution ($/kg) of each reagent/solvent to the RMC of the route product. This is simply kg/kg prod multiplied by the $/kg column. The sum of these values across the entire route should equal the RMC of the route product, unless OPEX is being added to one or more reaction steps. See the OPEX section below.
% RM cost/kg prod: Again, this is simply the RM cost/kg prod expressed as a percentage of the RMC for the overall route product. The sum of these values across the entire route should be 100%, unless OPEX is being added to one or more reaction steps. See the OPEX section below.
PMI Values¶
Three rows have been added to the output table to reflect the process mass intensity (PMI) for each reaction (rows 6 and 11) and the overall route (row 12). PMI can be defined as the number of kgs of materials needed to make 1 kg of product. This is a common metric for process waste, as larger PMI values can be interpreted as more materials being used, and potentially wasted, to create 1 kg of product. A “perfect” PMI is 1, which means that 1 kg of material was used to make 1 kg of product, for example a gas-phase polymerization may be expected to have a PMI close to 1. These values are shown in different columns because the per reaction PMI is calculated from the kg/kg rxn data, whereas the per route PMI is calculated from the kg/kg prod data.
Note
The PMI calculations as implemented by costcalc may not be strictly correct, because compound recycling is factored into the calculation. The final PMI here only considers compound masses that go to waste (are not recycled), whereas a true PMI may not always consider recycling. To get these PMI values, you can simply set the recycling parameters (“Recycle” column) to zero for all compounds, and the Excel file will recalculate the PMI parameters. Without recycling solvents, the PMI will likely be dominated by these materials, though.
OPEX Additions¶
The costing output for our demo model with a $10/kg OPEX added to each step is shown below. Some cells have been color coded for the coming discussion. In order to re-create this model, the OPEX value needs to be set for the reaction products in the input Route tables, as described in the OPEX input section. As a reminder, these values are only valid for reaction product rows.
The way the OPEX is handled for intermediate reactions is shown by the values highlighted in green. The initial RMC for Intermediate A in Step 1 is $28.95 (cell E5), which is simply the sum of the raw material costs as per usual. However, in Step 2, the OPEX value is added to this number, i.e. $38.95 (cell E7). Because the OPEX values are added in this manner, they will be modulated based on intermediate utilization and reaction yield in subsequent steps. This will be demonstrated below.
The OPEX is handled a little differently for the final product of the route, as highlighted in red. In that case, the OPEX is added directly to the final product RMC in the $/kg column (cell E10). This can be see by comparing the RM cost/kg rxn for the final product (cell L10), which is the raw materials-only value and the $/kg value (cell E10).
Separating the contribution of the OPEX costs from the raw materials is relatively straightforward. The sum of the RM cost/kg prod column (highlighted in blue) is the RMC for the final product, in this case $54.41/kg. The difference with the value in the $/kg column is $23.71/kg, which is the cumulative contribution of the OPEX values. Notice that the OPEX contribution for the first step is more than the original $10/kg, which is due to the yield losses and material utilization as described above.
The percentage columns for this new model deserve some explanation. The % RM cost/kg rxn values are relative to the RMC-only values (i.e. without factoring in the OPEX), so you’ll see that these numbers still sum to 100% for each reaction. However, the % RM cost/kg prod column is now relative to the final OPEX-included $/kg value, so the sum of the % values is less than 100%. However, the relative contributions from each component will remain the same, regardless of whether the OPEX is added or not.