Why the inventory results (inputs, outputs and total requirements) are negative?

Question

Hello! My name is Berenice, I am a  Ph.D. student from Mexico and  I am currently learning how to use Open LCA.

I am trying to replicate the study of Demichelis et al. (2020), published in the Journal of cleaner production, in order to practice how to do a life cycle assessment of a bioprocess.

The problem is that I have obtained negative results in all impact categories (they should be positive according to Demichelis).  I have seen in my project that the inventory results appear negative even when I put them positive. That's why I have a doubt about why they appear like that.

On the other hand, I am wondering if the negative inventory results can be influenced by the mass balance and by the selected type of flow (product, waste, elementary flow).  In other words, if the mass balance is wrong, can it affect the inventory results? and can the type of flow affect the results?

Thank you very much.

I wish you all, in advance, Merry Christmas, and a happy healthy new year!

Berenice

Answer 1

Hi Berenice,

welcome! Waste flows are "reversed" in the calculation when they connect to another process, other flows not, so it makes a difference if you define a flow as waste flow or product (for example). The mass balance normally has no influence since you typically do not substract one part from another. If you want you can also post a screenshot from your model, edit your question to do so. Also, for learning openLCA, you could check the case studies we have now in Nexus, here: https://nexus.openlca.org/casestudies (and you and everybody can also consider submitting your own case study there, if you have something where you think this is worth showing).

Good luck!

Andreas

Comments

Thank you, Dr. Andreas. I am going to check and to replicate the case studies you have suggested in order to learn more about how to do the LCA. I will let you know if I have questions.

Best regards!!!.

Berenice