Negative values (amounts) of inputs and outputs flows

Question

Hi users and Moderator of openLCA,
I post again the questions on the negative values (amounts) of inputs and outputs flows given in the ready-made processes of databases (ELCD, ecoinvent, etc.).
There are elementary, product and waste flows with negative values for some process data sets of the above databases. When calculating the impacts of a product system which comprises flows with negative amounts, the LCIA results will be affected.
I can’t understand what the meaning of “negative amount (value)” of an inputs or outputs flow is .
So, my question are:
When and why a flow (nevertheless its type) has a negative amount in the process data set?
Can someone give me a link to resources where I would be able to find more information, as my question does not concern the openLCA, but the databases with which application works.
Thanks in advance.
Chris P

Answer 1

When and why a flow (nevertheless its type) has a negative amount in the process data set?

sure, I will try: because of system expansion, and / or because of ecoinvent moving a waste to the input side.
There should be plenty of resources for both available on the net.
Hth,
Andreas

Comments

Thanks Andreas,
I found info on http://www.ecoinvent.org/support/faqs/methodology-of-ecoinvent-3/why-is-the-reference-product-of-the-treatment-activities-negative.htm

Chris P

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Hi there Andreas,  
Greetings.
In the new Ecoinvent 3.11 database, using the material flow logic method (waste taken into as input), there are no negative sign. I am giving the example of "treatment of biowaste, municipal incineration | biowaste | Cutoff, U".  Is it ok, if i do not put negative sign for the other model (waste battery recycling) using the database?
Can the similar approach be used in version 3.10?
Many thanks.

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Personally I think the waste flow modeling is better but you can use negative signs, then on both sides of the link of course, the process that is delivering and the process that is receiving

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I also do not put negative sign in either side. I want to follow "material flow logic" approach (as per the OpenLCA handbook) to model waste treatment. It was said before in one of the OpenLCA handbook that negative sign should be placed due to the convention used in the ecoinvent database. but i can see that in the new database following the "material flow logic" approach, in the ecoinvent database, there is no negative sign.

I think, OpenLCA's professional training might be giving advance demonstration on waste modelling. But i think it is the right time for OpenLCA to create a comprehensive demonstration video on waste treatment, like you develop on forward product manufacturing. To a very limited extent, except the "Webinar: Detailed Introduction to openLCA & Case Study - by ERG" case study on the OpenLCA youtube channel, no tutorials are available on waste treatment using OpenLCA.

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I see your point - of course you do not need to put negative signs at all, only in case you use them, you must use them on both sides of the process connection. Waste modeling is indeed part of our training. We have planned a series of new videos, let's see. Waste modeling is not in the planned list as it is now quite straightforward, but we can rethink that. Thank you!