In an attributional LCA we can determine some of the inputs whether they are from recycled or use the material and minimise their impact upfront. How would that be different if we use consequential LCA and assign displacement credit? Which method is more robust and more reliable for decision makers who lacks the knowledge for such details. I would appreciate hearing different views.
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Consequential LCA models the activities that change as a consequence of the demand for the input.
So, if your demand for recycled input leads to an increase in recycling, and a reduction in the amount of material going to final waste disposal, then your consequential inventory will include the increased recycling and the decreased final waste treatment.
If your demand for recycled input does not increase recycling (very often the case in well-developed recycling markets where all the material that can be recycled is already recycled and substituting virgin material) then your increased input of recycled material simply means that someone else can no longer purchase this recycled material and will have to use virgin material instead. So, in this situation, the net effect of your demand for recycled material is an increase in the equivalent amount of virgin production. So your consequential inventory will include this increase in virgin production and no change in recycling.
In attributional LCA you will typically include the recycling activity also in the second situation, even though there is no real world change in recycling. Similarly, attributional LCA will typically give too little credit for demanding recycled input in the first situation, even though the demand is fully determining the increase in real world recycling.
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