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Greetings fellow LCA practitioners,

I am in the middle of the verification dialogue of an EPD, stuck in the process of modelling the module D benefits for flat glass that is being recycled and used in foam glass production. 

This means that, foam glass production is the avoided product. However, for the recycling impacts I have entered glass cullet production. But the verifier told me that waste glass is not enough to turn it into foam glass, which is understandable. The problem is that I do not understand what other processes must be included here. 

Do all of the processes which are included in producing foam glass have to be included? This does not seem sensible, since that would mean having to add emissions from electricity and heating use, oxidation of SiO2 that is used to expand the glass, etc... 

I hope I have been clear and you can provide some guidance with this question.



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in openLCA by (120 points)
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by (115k points)

Hi Chri,

good question, the point is that you need to model your recyclate (waste glass) until the final waste stage and until a stage where the product made from it is equivalent to the product you use as substitution. And while glass cullets are probably not waste any more, they are not equivalent to foam glass. You could maybe model foam glass production from glass cullets, but easier and more efficient would be to find "virgin" glass cullets and use these as subsitute, i.e. as avoided product. What do you think?

Best wishes,


by (120 points)
Okay - a possible alternative would be to model the substituted material as aggregates, not specifically foam glass gravel. This means that the only recycling process would be rock crushing. I think this would work, however the module D benefits will be lower as a result.