I am currently modeling a reuse scenario for a timber frame. Based on guidance from One Click LCA (post “Balancing Energy and Biogenic Carbon in One Click LCA”) and the EN 16485 standard, I understand that biogenic carbon uptake should be accounted for in Module A1, while its release is modeled in Module C3. However, I am uncertain about the correct approach for biogenic carbon in Module D. One Click LCA (post “Balancing Energy and Biogenic Carbon in One Click LCA”) notes that any biogenic carbon or energy transfer to Module D must be added manually, even if automatic calculations were used for Modules A to C.
In the context of timber reuse or recycling, is it appropriate to manually include in Module D the biogenic carbon transfer to the subsequent product system, thereby crediting the current system? I assume this transfer would correspond to the same amount of biogenic carbon modeled in Module C3, but entered as a negative value.
Option 2 would be that, if the next product system accounts for the biogenic carbon transfer in its own Module A1–A3, then no additional credit needs to be added in Module D of the first life cycle to avoid double counting.
Hi Claudia, apologies for the delayed response and welcome to the One Click LCA Community!
No, you should not manually add a biogenic carbon credit in Module D for the reused timber. Your second option is the correct approach to avoid double-counting.
It does depend on the tool used. In the Net Zero Carbon tool you can control its attribution to D, and under some specific tools like the older DGNB tools and French tools, the benefits of biogenic carbon are included to Module D.
The benefit in Module D is calculated based on substitution, the environmental credit comes from avoiding the production of a new, virgin product.
The next product system that uses the reclaimed timber will account for its stored carbon in its own Module A1-A3. If you also claimed a credit in your Module D, the same stored carbon would be counted as a benefit twice.
The calculation is: Module D = (Impacts to prepare timber for reuse) - (Full A1-A3 impacts of an equivalent virgin timber product)
The A1-A3 impacts of the virgin timber you are replacing already include its biogenic carbon uptake. By subtracting this entire profile, you correctly account for the biogenic carbon benefit without manually adding it.