openLCA archived user forum

hello! I am a new user of openLCA, and have been doing the tutorials that which are available on the page.
In these tutorials don't come any uncertainty calculation and watching the beginners manual I have some doubts:
-to calculate uncertainty you can only use the sequential method of calculation of LCI not? My problem is that when I click on settings / preferences / settings for calculation methods and select secuential method, I do not see any preset value or anything, then I can not change anything, because nothing appears directly at first.
-Another question that I have is: what is the matrix pedigree function ?
-And the last one: To use the sequential method, or for montecarlo analysis do I have to use the ecoinvent database? Does it matter which database is being used?
Thank you so much
Best regards

I also have no options in the Settings for Calculation Methods boxes.

The SimaPro 7 tutorial gives a pretty good description of matrix pedigree. The instructions aren't useful at all, but the concept is there.
http://www.pre-sustainability.com/downl ... torial.pdf this should work.

http://greendeltatc.com/files/0/91/publ ... 16_226.pdf

I found this article to be very helpful. It doesn't resolve any of the issues with things not showing up, but it does give some tools that you can use if you export your system to a database, read it into MatLab or R, and feel like doing some mathematical pilates. :)

(It's also a link to Dr.s Ciroth, Fleischer, and Steinbach proving that anything can be modeled mathematically, except for the magnitude and variance of Awesome contained in their own brains.)

hello! I am a new user of openLCA, and have been doing the tutorials that which are available on the page.
In these tutorials don't come any uncertainty calculation and watching the beginners manual I have some doubts:
-to calculate uncertainty you can only use the sequential method of calculation of LCI not? My problem is that when I click on settings / preferences / settings for calculation methods and select secuential method, I do not see any preset value or anything, then I can not change anything, because nothing appears directly at first.
-Another question that I have is: what is the matrix pedigree function ?
-And the last one: To use the sequential method, or for montecarlo analysis do I have to use the ecoinvent database? Does it matter which database is being used?
Thank you so much

Dear Maliha,
I realise that the uncertainty tutorials are not any more fitting to the most recent versions, we will need to update them (or at least write for which versions they apply) - the sequential calculation is not directly available any more since version 1.2.7 since it has problems with large databases such as ecoinvent, we are now using always a (modified) matrix inversion approach (at least for the 1.3.x versions).
The pedigree matrix is explained in a special text for version 1.2.8 where we also introduced it, which you find on the openLCA download page, the direct link is http://www.openlca.org/c/document_libra ... upId=15473.
you last question: Not at all, you can use any database or also only your own data; ecoinvent is just convenient because it contains already uncertainty values for the unit process elementary flows.
Hope this helps, best wishes,
Andreas

- I moved your post to another section where it probably suits better

Hi Andreas,

You mentioned that Ecoinvent's flows already contain the uncertainty scores. Does this concern its pedigree matrix information or is that another issue? If it is connected with the pedigree, why does it seem that all Ecoinvent flows have the default worse-case uncertainty?

Best,

Michael

Hi, I am not sure I understand, the ecoinvent flows (in the ecoinvent database from nexus) contain the uncertainty information; we do not provide the pedigree assessment of ecoinvent though. Would this be useful?
Best
Andreas

Hi Andreas,

Thank you for the reply. When I am viewing Ecoinvent processes, I do not see specific values for uncertainty like the ones in your image. Under uncertainty it says Log Normal Distribution, but it does not give a value for the standard deviation. Is it because I am using openLCA 1.3?

Best

Michael

(accidental repost)

Hello,

I'm trying to understand how openLCA assesses uncertainty and what the software is capable of. I have reviewed the forum posts, openLCA wiki and some literature, and it is still unclear to me. I have a few questions:

1) On the openLCA wiki, it states that Gaussian approximations are used to calculate uncertainty. So, if I'm in the LCIA stage, and I click the button that says "Monte Carlo Simulation," what's actually being applied are the Gaussian approximation formulas? I understand they are comparable under a 20% relative error threshold, but I just want to be sure this is what is occurring under the hood.

2) I'm using v1.4 on a Mac and I see no option to edit "Settings for calculation methods" on the "preferences" menu at all. Was this completely removed from previous versions?

3) Andreas mentioned that "the sequential calculation is not directly available any more since version 1.2.7 since it has problems with large databases such as ecoinvent, we are now using always a (modified) matrix inversion approach (at least for the 1.3.x versions)." What is this modified matrix inversion approach, and is there a citation for it? The 2004 paper by Andreas and colleagues seems to refer to the sequential approach.

Thanks for your help!

Best,

Nicole