Wastewater treatment doesn't result in contribution to LCI

Question

I am creating a process for management of waste whey, and sewage is one of my options. I am struggling to get an effect from including the wastewater (treatment) flow as an input.

First of all, I can choose the flow 'wastewater, average' but I cannot select a provider - why is this? There are  processes available that have the reference flow of 'wastewater'.

Secondly, when I add the flow as an input with a specified, positive quantity, there is no effect. This complexes me, since I can see that many of the inputs to the wastewater treatment processes are expected to have impact.

If I add the flow as an output, I do get a response, but it is odd: In spite of the many inputs to the treatment process, the only one appearing in the contribution tree (related to wastewater) is clinker production, although, it has a contribution of 0.

If I do a quick calculation of ONLY the wastewater treatment, I get a result with many NaN's and an error mistake, something about a matrix that probably singular. I don't understand this - I would expect that it is possible to test the LCI of a given amount of wastewater treatment without any further.

What am I doing wrong?

Answer 1

Hello Andreas,

Few questions:

What database are you using?

What is the full name of the flow you are trying to model? Is it a waste flow, product flow, or elementary flow?

Which LCIA method are you using to analyse?

It will be much easier to answer your question, once I know these things.

Comments

Hi Matthias and Andreas, thank you for your replies, and sorry for not replying quicker - got caught up in the World.

It is indeed a waste flow, I call it AK240913: Waste whey. It is based on having waste whey as a burden- or production-free input as starting point, and I model different management methods.

I estimate impacts with ecoinvent - ReCiPe 2016 v1.03, midpoint (H).

I'll remember to include this info if I ask again.

I am now modelling the wastewater treatment downstream, and it does give me useful results - thanks a lot for that advice, it makes perfect sense.

Looking at my model, I actually wonder what changed from the problem I reported - I do not seem to find anything about clinker production, and even if the impacts from ww treatment are minor, they appear credible.

Perhaps it is good to sometimes give modeling a break and see what happens :-)

I will upgrade my version, thank you.

Answer 2

In addition to Matthias' points:

a) waste water is typically a waste treatment, you should model it downstream your main process to have it contributing to results (check some other posts here or also the handbook)

b) NaN etc. indicates that your model is not ok; the later openLCA versions (> 2.2) deal with incorrect models better, so use the latest version, and then check your model for redundant 0 values e.g.