Question

The results of conducting environmental impact assessments individually for each system and conducting two environmental impact assessments as a project are different. In order to check the difference in transportation methods, I created a project for transport, freight, lorry, all sizes, EURO5 to generic market for transport, freight, lorry, unspecified | transport, freight, lorry, unspecified | Cutoff, U and transport, freight, sea, container ship | transport, freight, sea, container ship | Cutoff, U and compared them, but the environmental impact assessment came out as a negative number and the results were different from the values ​​when the environmental impact assessments were conducted separately. I am curious as to why that is.

Answer 1

The results should be really the same if you have the same settings; you can modify the amount, the allocation factors or parameter values in projects and in product systems, which have an influence on the result. Could you maybe share more details, also related to which version of openLCA, which database (ecoinvent, which version) and impact method you are using? Thank you!

Comments

Are you using the EF v3.1 from the ecoinvent methods implementations or from the openLCA methods package and are you mixing different ecoinvent databases or do you only work inside, for example, ecoinvent 3.10 Cutoff Unit-Processes? Negative numbers could be a results of the consequential system models. Different system models should not be mixed.

Please try the same again in one database, for example ecoinvent 3.10 Cutoff Unit-Processes, and use the same impact method, for example EF v3.1, and check your parameters or allocation in case you use them when calculating separately and in a project. As Andreas already wrote, the results should be the same when you have the same settings and a correct environment (database).