Dear Monica

I first saw this question now so not sure if you still need an answer. But I would say that it really depends on the goal and scope of your study. If this process consists of a large share of the overall impact for your overall system, I would not use the default processes in Ecoinvent for landfill or AD either. For a pyrolysis process it is key that you try to model the process so it fits the feedstock you add to the process, and not just a default composition.

I am not an OpenLCA user, but my guess is that the best is to calculate an inventory in Excel (or some programming language) for your specific modelling and feedstock, and then add this to your model. We did something like this for a case some years ago (attached), where we had absolutely no data, and therefore used uncertainty intervals to accept the lack of data. This gives some quite uncertain results, but in my eyes it is still much better than just using a default data.

I will monitor the thread if you need more suggestions on how to go around it for your specific case.

Best,

Anders