elementary flow classified as "emission" cold be inserted as input in the model?

Question

Good morning,

I have a doubt about a model I am working on. I am using the Ecoinvent 3.5 Database. In the model I have to insert as input "3´,5´-dimethoxy-4´-hydroxyacetophenone" used as chemical in a industrial process. I found this substance only in the elementary flow as "emission". Is it correct to insert it as input in the model? Thank you in advance.

Answer 1

Hi, you can of course insert it, but it will remain an elementary flow and as such cannot be exchanged from one process to another. If you need it as a product, you can simply create a new flow, as product.

Hth, Andreas

- and afterthought: Since the existing elementary flow is an emission, it does not make much sense to enter it as input, unless you have a process that aggregates a system exansion calculation for example.

Answer 2

In addition to the answer of Andreas: it is highly recommended to never put emissions of elementary flows on the input side or resource consumptions of elementary flows on the output side but to use negative values then. openLCA infers the impact direction of an elementary flow from where this flow occurs in the processes. When these sides are mixed for a flow it can lead to strange results regarding the impact assessment (because openLCA then does not know if the characterization factor should be negative for the input or output side).

Comments

Dear msrocka and Andreas,

Thank you so much for your information provided and sorry for my delayed anser, I read only now your answers. My question was related to the fact that often, when I am building my model and I am searchng the data, It happens that I don't find any data of the substance I am looking for as input flow (for example a  flow from technosphere or flow from ecosphere) but instead I find the substance or a proxy data as emission flow. I bring you another example. I need to insert as input for a chemical process the gallic acid (3,4,5-trihydroxybenzoic acid). There are no data that represent this chemical as input flow but instead there is this chemical as emission flow named as "3,4,5-Trihydroxybenzoic acid".

So if I understood well, the best procedure is to don't insert in the input side  because it is an emission flow and  could lead to strange results, right? In this case if don't find anything usually how should I proceed to consider it?

Another question also: I checked the impact factors of the flow "3,4,5-Trihydroxybenzoic acid" and it is only considered in the Usetox 2 Impact Assessment method (with impact factor=0). Does it means that if I use CML for example as Impact assessment method, this flow has no impacts in my calculation also if I put it in the outputs as emission flow?

thank you very much for your support.