IWTO Says Carbon Accounting Is Failing Wool. Scientists Question Its Fix

The wool industry wants a recount.

The International Wool Textile Organisation (IWTO) argues that fashion’s environmental scoring tools are built for factories, not farms. That mismatch, it says, makes wool look worse than synthetic fibers because the accounting misses carbon moving through pasture, sheep and soil.

IWTO’s 36-page “Green Book,” launched in June and promoted more widely this month, pulls together the trade group’s case for wool as a renewable, recyclable and biodegradable material. Its more consequential proposal, however, is a new approach to calculating wool’s carbon footprint that produces dramatically lower results than conventional life-cycle assessments. The underlying research has already drawn pushback.

“Wool’s story should not be dictated by others, nor without respect for natural or terrestrial systems which are fundamentally different to linear industrial processes,” lead author Paul Swan said in announcing the report.

At issue is the treatment of biogenic carbon, or carbon circulating among the atmosphere, plants, animals and soil. Traditional wool LCAs tally greenhouse gases, including methane from sheep digestion and nitrous oxide from manure and urine. IWTO argues that they do not adequately recognize the carbon drawn from the atmosphere by pasture, consumed by sheep, returned to the land or temporarily stored in wool.

To address what it calls a broken accounting system, IWTO and Cape Wools SA funded research applying the ISO 14067 product carbon-footprint standard to six Australian wool enterprises previously examined in a 2016 LCA.

The resulting study, published in the peer-reviewed academic journal “Agricultural Systems,” found that an average 54.1 percent of the carbon sheep consumed was returned as manure, while 22.7 percent left through respiration, 7.5 percent through urine and 5.2 percent through enteric emissions. The model then tested how wool’s calculated emissions changed when different portions of manure carbon were treated as remaining within the grazing system.

The difference was substantial. An earlier conventional model put average farm-gate emissions at 21.3 kilograms of carbon dioxide equivalent per kilogram of greasy wool. The new study produced an emissions-only baseline of 22.5 kilograms, which fell to 13.7 kilograms when biogenic flows, excluding manure retention, were included.

Crediting one-third of manure carbon reduced the average to 6.6 kilograms. Crediting two-thirds produced a slightly negative result of minus 0.4 kilograms, effectively making the six enterprises carbon sinks under that scenario.

IWTO describes the findings as “game-changing” and says conventional LCAs substantially overstate wool’s emissions intensity. It also says the methodology received an ISO 14067 conformity assessment from TÜV SÜD in October.

The study’s interpretation of those carbon flows is contested.

In a formal comment published by “Agricultural Systems” in March, 11 researchers said the model presumes manure-derived carbon increases soil stocks without explicitly modeling what happens to it over time. Carbon returned to pasture can be decomposed and released again, they noted, meaning its presence in manure does not by itself demonstrate a lasting removal from the atmosphere.

That creates an imbalance, the researchers said. The model credits pasture for taking up carbon but does not count the carbon carried away in wool and livestock as leaving the system. Unless soil carbon stocks increase and stay higher, they argued, the calculation is tracking carbon as it circulates rather than showing climate mitigation.

They also challenged the authors’ interpretation of ISO 14067. In their view, the standard does not allow temporary carbon storage to be booked as a net removal without evidence that the increase will persist. The result is an underestimate of wool’s climate impact, they said.

Study authors James Blignaut and Swan replied to the criticism in a subsequent letter published in June. The Green Book does not mention either the comment or reply.

The question is not whether biogenic and fossil carbon are identical. Carbon in wool was recently drawn from the atmosphere by plants. Polyester, by contrast, is made with carbon extracted from geological reserves. The dispute is how to represent those distinctions without crediting routine carbon circulation as additional sequestration.

The Green Book also has an internal measurement question to resolve. Its executive summary states that one kilogram of clean wool contains approximately 1.7 kilograms of biogenic carbon dioxide equivalent. Its discussion of the underlying study applies roughly the same figure to one kilogram of greasy wool, including carbon in wool wax, suint compounds and vegetable matter.

The stakes extend beyond an academic disagreement. IWTO explicitly positions the model as a response to the European Union’s Product Environmental Footprint method, Cascale’s Higg Materials Sustainability Index and France’s Ecobalyse environmental-cost tool. The organization says its treatment of land use and biological production can make polyester and other fossil-based fibers appear environmentally preferable to wool.

Its comparison of the three tools consistently places wool among the highest-impact fibers. But the Green Book plots Ecobalyse points, PEF micropoints and Higg scores together despite their different units and methodologies.

Beyond the disputed carbon model, the Green Book cites research findings that wool garments are generally washed less frequently and at lower temperatures than cotton clothing, reducing energy and water use during use. It also points to wool’s established reuse and recycling infrastructure, biodegradability under suitable conditions and disproportionate presence in donated clothing relative to its share of virgin fiber production.

IWTO is simultaneously developing a harmonized definition of regenerative wool and a licensing framework for existing sustainability standards. Under the proposed system, qualifying schemes could issue IWTO Sustainability Certificates bearing unique license numbers. Eligibility would require some form of IWTO membership, though the organization has not yet published the essential criteria, participating schemes or oversight process.

IWTO says the Green Book will remain a living resource and that additional farm case studies and whole-farm modeling are underway. The organization also intends to make its biogenic methodology freely available.

Whether the approach ultimately changes the environmental scores attached to wool will depend on more than proving that existing systems are imperfect. It will require demonstrating that the carbon credited to wool production represents a measurable climate benefit—and not simply another stop in a cycle already underway.