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Why is the calculated impact different from the database eco-profil?

For example, I want to assess on openLCA, the emissions of 1 kg of methyl metacrylate production.  When I compute, I have an emission of 7.0 kg CO2 eq using the IPCC 100a method and if I compare it to the database source which is the eco-profil of the product, it says that for 1 kg of MMA produced, we have 3.47 kg CO2 eq.
in openLCA by (350 points)

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by (126k points)

What do you mean by 

the database source which is the eco-profil of the product

(and which database are you referring to?)

Thank you!

by (350 points)
edited by
Hi !

Thank you for your answer-back,

I meant that I have found one study, which is the "Eco-profil" from CEFIC for the methly methacrylate production, and it says that it emits 3.47 kg CO2 eq for 1 kg of methyl methacrylate production.  Knowing that even EcoInvent has based its database on that particular paper, so we have the same system boundaries, goal and scope.

However, when I plot on OpenLCA, I have the double. I am trying to understand what the problem is from, knowing that I simply have modeled one input "methyl methacrylate production" for 1 kg and I obtain at the end almost the double of the value, which is the equivalent of 7.0 kg CO2 eq.

My problem is : how is it possible to have different values knowing that the EcoInvent database has based its calculation on that paper citing that for 1 kg of methyl methacrylate we obtain 3.47 kg of CO2 eq and when I model with the same database, I obtain 7.0 kg CO2 eq, just with one input which is "methyl methacrylate production" for 1 kg (so the same functional unit).

What possible factors can influence my calculation ?
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