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Product footprints differ from organisation footprints in one way that governs everything else: every figure has to be expressed per unit. A factory’s annual electricity is not useful until you know how many units that factory made. So settle the functional unit first. One bottle, one garment, one kilogram, one service use. Collecting before that is settled produces numbers you cannot combine. See What is an LCA? for how to define it.

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Materials

Weight is the number everything else depends on. If a bill of materials gives you dimensions rather than mass, weigh a unit and its components. An afternoon with a scale beats a month of supplier emails.

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Manufacturing

Scrap matters more than people expect. If a process wastes 20% of input material, every unit carries the footprint of 1.25 units of material. Ask for yields at each stage, not just the finished count.

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Packaging and distribution

Do not forget the packaging that never reaches the customer. Pallets, shrink wrap, and outer cartons are part of the product’s footprint even though the buyer never sees them.

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Use phase

For appliances, vehicles, and anything that draws power, this stage usually dwarfs everything upstream. For a product that just sits there, it may be zero. Knowing which case you are in determines where the rest of your effort should go.

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End of life

End of life is almost always modelled from regional averages rather than measured. That is accepted, as long as you state the assumption and the source.

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Two traps worth knowing

Averaging across variants. If one product line covers three sizes, a single averaged footprint is defensible for internal use and weak for a customer claim about a specific size. Decide early which you need. Supplier data that is not per unit. A supplier who sends annual totals has given you something you cannot use until you know how many units that total covers. Ask for the denominator in the same request as the numerator.

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