The interface of the Inputs/Outputs of my process doesn't let me specify other units beside n. of items

Question

Hi!

I am trying to calculate the LCA of a natural wall, built with hearth and bamboo, and compare it with a wall of concrete; i am now inserting the different elements inside a section of the natural wall (bamboo, earth, metal net, plaster ecc..), however I wonder why i can't specify the area or kg of the material instead of just the number of items....

Thanks for your help!

Arianna

Answer 1

Hi Arianna, if I understand the question correctly, you are trying to change the units of the inputs/outputs that are not the quantitative reference (so the ones, you did not create yourself)

In openLCA the flows you use in inputs/outputs have a list of flow properties. Usually only one flow property is specified in the reference data. Each flow property has a reference to a unit group, which respectively has a list of units, that can be converted within this group (e.g. 1 kg = 1000 g).

You can only select those units referenced via the "Flow -> Flow property - Unit group" chain. 

If you want to select a different unit, you would need to add the correct flow property (e.g. Mass) to the flow's flow properties list and specify a conversion factor to the other flow property. 

An example: You have the flow 'Methanol' an its set flow property is Volume. You want to specify Methanol in kg. The density of Methanol is 0.79 g/cm³. So to convert 1 l of Methanol to kg, you will need to use a conversion factor 0.79 for conversion. Now you could use all Mass and Volume units to specify your inputs/outputs.

I hope this helps. Below you can see how this would be done in openLCA (Just as an example, this is not part of the reference data)

Comments

In your case the only flow property is "Number of Items", you would need to add the Mass flow property with a correct conversion factor from piece to kg

Answer 2

Hi Arianna, your issue sounds like you want to change the 'Reference flow property' of your process from 'number of items' into e.g. 'area' or 'mass'.

If you create a new process you can simply choose an appropriate 'Reference flow property' (select 'create a new flow for the process').

For existing processes open the Input/Outputs tab at the botom of a process and change the unit. The units may be limited by the reference unit in the flow properties.

Comments

I don't know why i don' see the possibilities you are referring to, i'll try sending you the screenshots of what i see:

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When you create the new process select "Create a new flow for the process" and you will be able to chose another reference flow property. Hope that works.

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is there a way to change the reference flow property after creating the process, and inputting all the data? I accidentally put number of items when I want the unit to be mass.