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How to normalize all the LCA impacts? For example, if I want to compare them in percentage, I would need all of them to be in the same unit. But I don't know how can I change all different units to kg CO2 eq.

Arbo94
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For normalization you always calculate relative to some reference value. Your reference value is in kg CO2e, so I take it you are calculating global warming potential (greenhouse gases). If a particular input doesn't produce any greenhouse gases, then the output is 0%. For all other values you look at greenhouse gas outputs which should be in some form of weight CO2e (for example gram CO2e or kg CO2e). If not all values have the same unit, make sure you first convert everything.

In your comment below you mention you need to convert kg CFC-11 to kg CO2e. This can be done by looking up the Global Warming Potential (GWP) factor for that gas. Wikipedia lists conversion factors for different gasses. Due to new scientific insights these numbers changed a bit over time, so that's why you see more than 1 number per cell. Typically the most recent 100 years GWP is used, so in your case that is 6226 (data from 2021). Many LCA software already have such conversion factors available or allow you to output directly in CO2e.

Fred
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THelper
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  • Thanks a lot for the explanation. What I have trouble with is that now I have calculated all lcai based on what I found in the Okobaudat and I would like to convert various impacts into a same unit. However, I don't know from where I can find a conversion table for EN15804+A2. My input is only material. – Arbo94 May 30 '22 at 10:49
  • @Arbo94 I'm afraid I am not following you. EN15804+A2 is a norm. I'm not very familiar with it, but my understanding is that it says what impacts should be included in your analysis and dictates that you have to do an end-of-life-analysis (among others). So what's this conversion table you are looking for? – THelper May 30 '22 at 14:16
  • Sorry, I meant that I like to convert different LCA impact units to kg CO2 eq. For example, from Kg CFC 11-eq to Kg Co2-eq...but I don't know the conversion value. – Arbo94 May 31 '22 at 11:34
  • @Arbo94 Ok, so the issue is converting different greenhouse gasses to CO2e. I'll add something to my answer how to do that. – THelper May 31 '22 at 12:34