By Amanda Symm, Communications, LHCA
There's a lot leather can learn from how wool just made its case. Its trade body's new Green Book is worth studying as a model.
IWTO (the International Wool Textile Organisation) published a Green Book in June 2026 that takes direct aim at the carbon-accounting tools brands use to score fiber sustainability. Its case: wool rates consistently high, and synthetics consistently low, across three separate tools, Higg MSI, the EU's PEF-CR (Product Environmental Footprint Category Rules), and Ecobalyse, in ways IWTO argues don't reflect wool's own biogenic carbon cycle. The comparison behind that claim is a single case study, a 150-gram knit T-shirt modeled across six fibers as processed in China, so it's a meaningful data point rather than a verdict on every wool product everywhere.
IWTO's argument is specific: these tools count the emissions from producing petrochemical monomers, the building blocks of synthetic fiber, but skip the equivalent accounting step for bio-based fibers like wool. That inconsistency, IWTO says, “significantly affects” wool's reported footprint. None of the three tools currently credit the carbon a grazing system captures and returns to the soil through manure, either, even though that return flow is measurable.
IWTO didn't stop at the argument. Working with Cape Wools SA, it built its own biogenic life cycle model, published the methodology in Elsevier's peer-reviewed journal Agricultural Systems, and had it independently assessed for conformity with ISO 14067:2018, the international carbon footprint standard, by TÜV SÜD in October 2025. Credit two-thirds of a wool system's manure carbon as a return flow rather than an emission, and the model shows wool's calculated emissions intensity dropping close to 100%.
IWTO's Green Book doesn't mention leather at all; the parallel below is LHCA's own reading, not a claim IWTO makes. But the playbook is the one leather has been building with IDI (the Institute for Data Integrity): commission independent science, get it peer-reviewed and third-party assessed, publish it, then challenge the tools directly rather than simply objecting to the scores they produce. Wool's trade body got there first. For LHCA members watching brands cite Higg MSI scores in sourcing decisions, and for brand teams relying on those scores to make procurement calls, it's a working example of how a material earns the right to contest a number it thinks is wrong.