I’m confused about my results - some of the GWP total values are showing as negative and I don’t understand why. I’m using materials that I’ve used before which have never given negative numbers. Also, when I drill deeper into the report, some of the percentage values come up as negative, but are positive when converting to decimal. Is this expected and if so what is it telling me? As far as I can see the materials giving me a negative value (in my case, use of softwood timber for packaging) aren’t contributing in a positive way to the total GWP.
Bio-based materials will contain biogenic carbon in the A1-A3 modules, therefore likely resulting in a negative GWP-total overall for A1-A3.
If you are comparing a design to another in the Results page, this will likely throw off the percentages due to the negative. I would recommend just comparing GWP total and fossil, for example, to keep things more interpretable.
Thanks Thomas. Yes, it’s the biogenic content in the wood packaging - I’m slightly more than other projects which I guess is why the total GWP is showing up as negative, rather than just the GWP biogenic. The EPD’s we generate quote the A1-A3 GWP total and fossil in the summary page, so if the total is negative, for example, my product has GWP total A1-A3 of -73kg and GWP fossil A1-A3 of 172kg, would you interpret that it has an overall positive global warming potential, since the total is negative?
Hi Camilla! Yes! Exactly, the GWP-biogenic can compensate the GWP-fossil in some cases leading to an overall negative GWP-total for A1-A3. So overall your cradle-to-gate is “good” for the environment in terms of CO2 emissions.
Please remember the biogenic balancing as well. So while the packaging enters in A3, it will leave the system in A5 upon arriving on site and being disposed of. The biogenic will leave with this wood packaging, giving us a positive GWP-biogenic. Overall GWP-biogenic will always sum close to zero over the life-cycle (A-C). Balancing is further explained in our Help Centre here.