What Module D means in steel EPDs

Open a steel environmental product declaration and you will see a cradle-to-gate figure (say HRC at 2.31 kg CO₂e/kg) and, listed separately, a negative Module D number (about −1.25). It is tempting to add them and quote "net ~1.06." Don't.

What Module D is

In EN 15804, Module D captures "benefits and loads beyond the system boundary" — most importantly the credit for steel recovered and recycled at end of life, modelled by system expansion. worldsteel reports it separately from the production modules A1–A3 precisely because it sits in a different life-cycle stage and depends on assumptions about future recycling that the production step does not.

Why not net it into production

The A1–A3 figure already includes the benefit of scrap used as an input today. The Module D credit is for scrap recovered as an output tomorrow. Fold D into production and you count the recycling loop twice, understating cradle-to-gate emissions and flattering the material. A legitimate cradle-to-grave study models the whole boundary explicitly; it does not just subtract D from A1–A3.

How MatQuo handles it

Every MatQuo steel record stores the A1–A3 value and the Module D credit as separate fields. The environmental impact calculator shows Module D in its own panel and never subtracts it; the comparison tools compare production figures only. See the steel sustainability page for all seven products with their D credits.