ReCiPe Question: What`s the difference between Normalized & Single Score?

Question

Hi Folks,

I am using EcoInvent 3.3 in OpenLCA 1.5, reviewing LCIAs of different processes and product systems.

For the purposes of my project I`m using the ReCiPe impact method, w/ Normalization & Weighting set World ReCiPe H/A [person/year].

When I calculate a result, the "Normalization and Weighting" tab in OpenLCA has two sections with values for the ReCiPe impact factors, labeled "Normalization" and "Single Score".

It almost looks like the "Single Score" values are the weighted "Normalization" values -- many of them are times 400, 300, 200 as indicated in the ReCiPe111.xlsx Weighting tab downloaded from http://www.lcia-recipe.net/characterisation-and-normalisation-factors

However the multipliers are not consistent across the impact factors, nor are they consistent same for the same impact factors across the results from different product systems.

So what exactly is "Single Score"? And why the inconsistency?

(I`m pretty new to LCA, so I may easily be missing something obvious here! Thanks in advance for your help!)

Answer 1

Hi Ethan,
yes I agree this is somewhat confusing (maybe in ReCiPe especially) - in a nutshell, and somewhat simplified: single score is the aggregated impact score which is obtained after a weighting, which is performed with the 400, 400, 200 factors in ReciPie which are in principle percentages (40%, 40%, 20%) but in addition include a factor of 1000 with the idea to overcome too small numbers; normalized values are impact values devided by a reference value to set them in perspective and to get rid of the unit. It is a necessary step before calculating a single score, since the latter requires dimensionless (or: equal dimension) values.
Hth,
Andreas