Evidence that withstands scrutiny
Evidence that withstands scrutiny
A product carbon footprint is only meaningful inside a stated boundary. Two competent studies of the same product can produce very different numbers, both defensible, because one stopped at the factory gate and the other followed the product to disposal. This note covers the four decisions that determine whether the result answers the question that was asked.
One tonne of product, one square metre installed, one packaged unit — and the function it performs. A footprint per tonne and a footprint per unit of function can rank two products in opposite orders, and only one of them answers the customer's question.
Decision 1Which inputs are excluded because they fall below a stated threshold of mass, energy or environmental relevance. The threshold is stated; it is not "things we could not find data for".
Decision 2How impacts are divided where one process makes several products or co-products. Mass, energy content, economic value, or physical causality — each gives a different answer, and the choice must be justified against ISO 14044.
Decision 3Primary data for the foreground system; for the background, the database, its version and the geography it represents. A European average dataset applied to a Gulf grid is a finding, not a simplification.
Decision 4Comparison between products is only valid where the declared unit, boundary, cut-off criteria, allocation rules and data vintage are equivalent. That is why Type III declarations are comparable only inside the same programme and the same product category rule — the PCR exists precisely to fix those parameters.
Outside a shared PCR, comparing two published footprints is usually invalid, and presenting such a comparison in marketing material is a claim that will not survive examination. Where a comparison is needed, the honest route is a single study covering both products on identical assumptions.
A separate point worth stating plainly: a product carbon footprint is not a CBAM figure. CBAM embedded emissions are calculated under EU rules with their own system boundary and their own treatment of precursors, and cannot be substituted with a CFP or an EPD.
Editorial note. Author and technical review above are editorial functions. They are separate from the independent technical review and the decision functions required under ISO/IEC 17029:2019, which apply to validation and verification engagements and not to published articles. Nothing on this page is advice on a specific engagement, and nothing here extends or replaces the accreditation records.
Tell us what must be relied on, who will rely on it and by what date. We will confirm the correct programme, evidence requirement and responsible entity — or tell you it is outside our scope.
