Chapter 2: Build the model

« Go Back



There are two ways to model a process on the Platform; through the Canvas and through the Processes page. These two modelling ways can be used in parallel, however they both have certain advantages and disadvantages. These two ways of modelling are described in more details in the next sections

Modelling in Canvas versus in the process list
The Canvas is a visual display of the created model. The benefits of the canvas are that canvas can:
  • Be used to create a visual schematic of the model.
  • Easily keep the overview of what has been modelled and the relationship between processes.
  • Connect processes, edit reference flows and delete processes from the model.
  • See more in section 3.1.

More advanced editing should be done in the list of Processes of the project. When modelling in the process list it is possible to:
  • Add and remove library processes.
  • Add and remove direct emissions (substances) in a process.
  • Connect processes, edit reference flows and delete process from the model.
  • See more in section 3.2.


Using the Canvas

As mentioned above, the canvas is a visual display of your model. It shows the processes and flows, and their relations. To start a model on the canvas:

  1. Go to Canvas in the left-side menu.
  2. Double-click on the white space to create a new node.
  3. Rename the node. This node is actually now a new process – with a reference product bearing the same name.
  4. To create a sub-process connected to the new node, double-click on the new node to create a new sub-process.
  5. Rename the sub-process.
  6. Add as many sub-processes as needed.

What you see now is the schematic of the model, and you might have noticed that there are no library processes, these need to be added from the process list (see the section on Processes).


Canvas Tips!

Tip 1: By default, the reference flow of the process has a value of 1 and a unit in ‘p’ or pieces. You can edit the value and the unit by clicking the label on the arrow and typing the amount and unit you want to use.

Tip 2:  If the node was created without a link to the top process you can always drag an arrow from the top of the sub-node to the top node to link them.

Furthermore, there are other functionalities on the canvas, such as:

  • Expand and collapse sub-processes - When there are sub-processes for a process, there will be an option to display or not display the processes below. This is shown with a little plus sign at the bottom of the process node.

Expand and collapse

  • Node colors - Different colors represent different types of processes:

    1. Blue nodes are processes which are connected to a grid question in a Collect data collection form.
    2. White nodes are processes created from answers from a Collect data collection form.
    3. Pink/orange nodes are library processes used in the current project.
    4. Green nodes are project processes, which are created in the current project.
  • See the example below:

Types of nodes

  • Descriptive numbers - Each node and its links display two numbers. These numbers represent the reference flow (amount and unit), which can be seen inside the node, and the input flow, which can be seen in the arrow of the reference.

Input and reference flows

  • Handy features - On the top of the canvas, there are several useful buttons. You can find:

Canvas top bar settings

  1. Show Sankey: This option allows you to see the calculation network of your model. Keep in mind that this function is only available after you have selected a default calculation set up (see the section on Calculations).
  2. Turn entire canvas 90 degrees: This will be remembered for the specific projects, so next time you come back it has the same layout as before.
  3. Zoom in and out: You can zoom in and out more smoothly by holding CTRL and using the mouse wheel.
  4. The question mark will start a short introduction to the basic features of the canvas.


The process page shows all the different processes which are being used in the project. It has two overarching tabs Processes and Library processes used.

Filtering Tip !

In many places on the platform there are filtering options. If you use these smartly the modeling will
be a lot easier. In the processes page these filtering options are available:

To filter for any of these options:

  • Click on the funnel for the category you want to filter on.
  • Write a part of the name, and click filter.

Processes shows the processes created in this specific project.

My processes page

To create a new process:

  1. On the process page, click Create new process.
  2. Give it a Name, and select the Geography.
  3. Then, go to the Outputs tab.
Edit process
  1. Click on + Add output. You can choose to create a new product or use one from a library. When creating a new product you can, for simplicity, you can use the process name.
  2. Then, go to the Inputs tab.
  3. Click on + Add input.
  • Start typing the name for the product input you want to connect to.
  • If the product already exists it will be listed, choose the correct product or press enter to create a new product.
  • Fill in the amount, quantity and unit (quantity and unit, only if it is a new product).
  • In the drop-down below Unit, scroll to find the process you look for and select by clicking on the process or type a new process name and press enter.
  • Select the geography, click Save.

Process Tip !

In all the Amount, Allocation percentage and Unit fields, a Parameter can be created or used. See the section on Parameters for more information.

  1. Substances, or elementary flows, can be added in a similar way as the inputs and outputs.
  2. Finally, it is possible to connect the process to Collect. This is a powerful feature that enables you to collect primary data via a Collect survey and feed the results directly into your Flow model. You can find out more about this feature and how to use it here or in the Getting started with Collect manual.

In Library processes used you can see which library processes are connected to processes from the current project, and from which library they are from. They might be from Generic libraries, such as ecoinvent and Agri-footprint, or Company libraries which are created specifically in your company.

These processes cannot be edited from the current project.

Library processes


Parameters can be very useful in large, as well as, smaller projects. They can be used to either easily change the calculation, or as a switch to change between processes. As you go, you will learn more about this.

There are many ways in which you can create a parameter throughout Flow - for example, from the Canvas or directly in a process. No matter where the parameter is created, it will be listed in the Parameters page and you can always edit them there.

To create a parameter from the Parameters page:

  1. Go to the Parameters page.
  2. Click + Create parameter.
  3. Then the parameter will be added to the list and you can change the name, add an expression and/ or a comment.

Parameter Tips !

Tip 1: The comment field is good to use for keeping track of the unit of the parameter

Tip 2: You can create a parameter in the label on the arrow in Canvas. Then the default value will stay 1 until it is edited in the parameters page.

Tip 3: When editing a process you can also fill in the name of a new parameter and the default value will again be 1 until it is edited in the parameter page.

The overview of list of parameters also offers a number of handy features:

Parameter features

  • Expression defines how the parameter is calculated. If you enter a number, then it will be the parameter’s default value (see below), but you can also enter a calculation formula.

Allowed expressions
When creating a parameter or writing a value in any of the quantified fields such as ‘Amount’,
’Allocation percentage’ etc. there are some expressions which are allowed. These expressions
  • Plus (+), minus (-), division (/), modulo (%), multiplication (*), power (^).
  • Equal (=), unequal (<>).
  • Smaller than (<), smaller than or equal to (<=), larger than (>), larger than or equal to  (>=).
  • Scientific notation (2.3E-7).
  • IF statements (2 IF Parameter1 == 4 ELSE 1).
  • AND statements (2 IF(Parameter1 == 4 AND parameter2 == 2) ELSE 5).
  • OR statements (2 IF(Parameter1 == 4 OR parameter2 == 2) ELSE 5).
  • MAX and MIN functions (MAX(2;5)), (MIN(2;5)). Note! For more than 2 arguments, please adapt the function to (MAX(1;MAX(2;5))), (MIN(1;MIN(2;5)))
  • Parentheses for resolving sub-expressions (2*(4-3)).

Tip ! If you change the name of the parameter in the parameter page, the name of the parameter will be changed in all the fields in which it is used throughout the platform.




  • Default value shows the value which will be used for further calculations, this is especially interesting when you create a large expression with using other parameters or complex formulas.
  • Collect data switch is used to connect a parameter to a Collect question. See how to do it here.
  • Parameter tree shows which parameters and values are used to calculate the value of the current parameter.
  • Used by-button, shows if and where the parameter has been used in your model.
  • Finally, if you would like to delete a parameter, click on the  Trash can.

A parameter can be used in any value field throughout the platform. To call a parameter in a value field:

  1. Type the exact parameter name in value field.
  2. When you click out of the field, the default value with a Label is displayed.


On the Products page it is possible to edit products. This page is not important for a Flow beginner user, however it is important to understand what a product is and how it is different from a process. 

Every process is producing one or more products, and each product can have one or more producing processes. For example, dairy farming produces mainly milk, however meat is also a product of this process. On the other side, a plastic bottle can be produced from injection molding as well as extrusion molding. For more on this have a look at this article: What is the difference

The only thing that is interesting to know about products when modeling is that it is usual to give the product the same name as the producing process.


When the model is ready, calculating the results is the next step. On the Calculations page, there are a lot of options, some more advanced than others. The tabs on the calculation page are described below:

Calculation tabs

A. Calculation set up is used to set up the calculation. The top process must be selected, as well as, how much of the top process should be calculated and which LCIA method to use when calculating. There are also other advanced options which can be explored.
To run a calculation:

  1. Go to the Calculations page
  2. Select the top process of the model, see below.                                              

Calculation setup 

  1. Fill in the amount and unit of the top process which will be calculated.
  2. Select the appropriate LCIA method.
  3. Click Calculate.
Calculation tip !

Saving a ‘Default calculation setup’ will allow you return to the same set up easily and use the Sankey diagram on the Canvas. 

If you want to adjust the results to a certain group of processes or geography, you can use analysis groups to make sets of processes from which the results are calculated. Find out how to use them here.

B. Impact assessment will open after calculating the results. It shows the characterized LCA results in several level of details, depending on the choices you made in the calculation setup. For more details see below.

Calculation results

The first graph, Most Contributing Processes seen above, shows the impact of each process in your model, however this is not a cumulative impact. It is the impact created directly from each process in the lowest level of your model, including library processes. Therefore, normally the top tier processes are not shown since they are usually not creating direct impacts.

The table Process contribution per impact category corresponds to this graph. It shows the numerical values of the direct impacts and the contribution to each LCIA indicator of each process.

Finally, the middle table called Cumulative process contribution shows the cumulative process contribution at different levels of your model and the contribution to each LCIA indicator of each process. By default it shows 2 tiers, but this can edited in the Calculation setup.

Additional resources
For more information on damage assessment, normalization, single score, inventory and substance contribution see the Introduction to LCA.
Be sure to visit for a wealth of information to help you get started or better understand the applications of LCA.


<< Go back to Chapter 1 Set up your model

Learn more about Flow >>