Product system listed as an impact contributor

[gnicki]

Hello,

I have run a calculation and am confused with the results. Looking at human toxicity for example, it lists the main contributors of the impacts in the pie chart. However, along with several impacting chemicals, my product system "crop production" is also included as an impact contributor, and is in fact the main contributor. So this means that the biggest human toxicity impact to producing crop x is the production of crop x -- this makes no sense!

I am assuming I have gone wrong somewhere -- anyone have any ideas? Any thoughts would be greatly appreciated.

(I am running ecoinvent 3.2 cutoff DB with openLCA 1.4.2.)

Thanks,

Geoff

[aciroth]

Geoff,
the pie charts does not list products systems but processes? Therefore it cannot list your product system as contributor (but probably you have a process with the same name).
Best
Andreas

[gnicki]

Ok, yes I see what you mean. Both my process and my product system are labelled "Crop X production". I did it like this to follow the tutorial video for "Bottle production", where she had named things in the same way.

That clears up the naming issue, but still leaves me a bit puzzled how openLCA works.

I've created the process of "Crop X production", simply adding in all of the inputs needed to produce 1 kg of crop X. So I have added in all of the elementary flows involved on the farm (i.e. pesticides, fertilizers, etc.) and their respective quantities, as well as all of the associated upstream inputs for manufacturing these agrochemicals, and their respective quantities. So it's a pretty simple calculation.

So when I calculate, I will get some impact categories showing (like you said) the process "Crop X production" causing a large or the greatest impact. So what does this mean? Does this mean that this stage of crop x production, i.e. the stage on the farm, causes the greatest impact of that category? And why is this process evaluated as a whole rather than for each of its individual parts? I mean, let's say that I want to know what are the relative impacts of pesticide x vs. pesticide y use on the farm, as elementary flows. Can openLCA not show this? If it does, how do I find it?

Any help you could provide would help greatly. I am admittedly stumbling around in the dark with this LCA analysis, as it is my first time (and unfortunately no colleagues having experience with openLCA).

Thanks,

Geoff