It’s soft. It’s vegan. It looks just like leather.
It’s also made from fossil fuels.
An explosion in the use of inexpensive, petroleum-based materials has transformed the fashion industry, aided by the successful rebranding of synthetic materials like plastic leather (once less flatteringly referred to as “pleather”) into hip alternatives like “vegan leather,” a marketing masterstroke meant to suggest environmental virtue.
Underlying that effort has been an influential rating system assessing the environmental impact of all sorts of fabrics and materials. Named the Higg Index, the ratings system was introduced in 2011 by some of the world’s largest fashion brands and retailers, led by Walmart and Patagonia, to measure and ultimately help shrink the brands’ environmental footprints by cutting down on the water used to produce the clothes and shoes they sell, for example, or by reining in their use of harmful chemicals.
But the Higg Index also strongly favors synthetic materials made from fossil fuels over natural ones like cotton, wool or leather. Now, those ratings are coming under fire from independent experts as well as representatives from natural-fiber industries who say the Higg Index is being used to portray the increasing use of synthetics use as environmentally desirable despite questions over synthetics’ environmental toll.
“The index is justifying the choices fashion companies are making by portraying these synthetics as the most sustainable choice,” said Veronica Bates Kassatly, a fashion industry analyst and critic of the industry’s sustainability claims. “They’re saying: You can still shop till you drop, because everything is now so sustainably sourced.”
The Sustainable Apparel Coalition, which runs the index and counts among its members almost 150 brands, including H&M and Nike, as well as retail giants like Amazon and Target, said the index uses data that is scientifically and externally reviewed.
“This is years of work to compile and put together the best available most up-to-date data,” said Jeremy Lardeau, vice president of the Higg Index at the apparel coalition. “We’re not actively pushing for the synthetic numbers to be low. We’re just collecting the data in one place.”
Critics counter that some of the data underpinning the index comes from research that was funded by the synthetics industry that hasn’t been fully opened up to independent examination. Other studies incorporated into the Higg Index are sometimes relatively narrow in scope, raising questions about their broad, industrywide applicability.
The index rates polyester as one of the world’s most sustainable fabrics, for example, using data on European polyester production provided by a plastics-industry group, although most of the world’s polyester is made in Asia, usually using a dirtier energy grid and under less stringent environmental rules. The Higg rating for elastane, also known as Lycra or spandex, draws on a study by the world’s largest elastane producer, Invista, a subsidiary of the conglomerate Koch Industries.
The Higg Index itself was born a decade or so ago amid a rising emphasis among consumers on sustainability, environmental and animal-welfare concerns. It coincided with advances in synthetic-based fabrics that were not only inexpensive but had new features that buyers craved, such as improved elasticity or improvements in the ability to wick away perspiration.
Many of the garment brands that sit on the board of the group that oversees the index profit from two fashion megatrends that directly benefited from advances in synthetics like these: fast fashion and athleisure. The fast fashion giant H&M, for instance, displays what it calls Higg-based sustainability profiles alongside some of its products.
“Higg’s members, a lot of them are fast fashion brands, and they all use mainly polyester. So it favors them to get polyester a better rating,” said Brett Mathews, chief editor of Apparel Insider, an industry-focused publication based in London. But the data used was “very poor,” he said, and “the net result is that the actual Higg score, which says this fiber is more sustainable than that one, is misleading to consumers.”
The Sustainable Apparel Coalition said company data was accurate and comprehensive, and had been collected in line with industry standards. Any gap between European and Chinese polyester production would be small compared to other differences in producing the textiles, like the knitting or weaving process, it said.
H&M, which sits on the coalition board, said the index was based on “standardized and verified third party information,” and that the tool was being “continuously developed and improved.” Walmart said the Higg was not the only tool it used to improve the sustainability of its apparel, and that it continued to assess the index’s capabilities. Invista did not respond to a request for comment.
The Higg Index is on its way to becoming a de facto global standard. In Europe, policymakers this year are set to lay out rules on how brands must back up their environmental claims, and in New York, a bill seeks to hold fashion brands accountable for their role in climate change. Fashion-industry officials have said the Higg Index could be used as a benchmark in both.
The fashion industry has long been under pressure to address the environmental effects of its products and practices. The industry is responsible for 8 to 10 percent of the world’s emissions of planet-warming carbon dioxide, the United Nations estimates, more than all international flights and maritime shipping combined.
Natural materials, like cotton, have their own environmental costs, of course. Cotton and silk cultivation is water-intensive and can involve heavy pesticide use. Leather can come from well-managed ranches, or it can be tied to activities that are extremely damaging to the environment. Last year, a New York Times investigation showed how leather from cattle linked to deforestation in the Amazon was making its way to the United States to be used in automobile seats.
The production of polyester and other materials has tripled since 2000, to nearly 60 million tons a year, according to the Textile Exchange, an industry group. Silk and wool have declined over the same period, and cotton has risen more moderately.
Producers of natural fibers say the Higg Index has portrayed that shift as positive for the environment based on questionable data. Silk’s unfavorable rating in the index, for example, draws on a 2014 study by Oxford-based researchers of 100 silk farmers who rely on irrigation in a single state in India.
That study’s lead researcher, Miguel F. Astudillo, said he hadn’t known until recently that his work had been used by the Higg Index. He said his study of Indian silk, which is mostly used domestically, was not representative of global production. “If they read the article and the results, they’d know it’s a stretch to use it for assessing silk in general,” Dr. Astudillo said.
The International Sericulture Commission, which represents 21 silk-producing countries, last year filed a complaint with the Federal Trade Commission accusing the Higg ratings of “creating considerable damage to the natural fiber industry” and calling on the index to carry out a broader study of global production practices.
“They’re saying silk is 30 times worse than synthetic products. Can anyone really believe that?” said Dileep Kumar of the International Sericulture Commission.
In 2020, leather-industry groups from around the world also called on the Sustainable Apparel Coalition to suspend its poor score for leather, which the industry said was based on “out-of-date, unrepresentative, inaccurate and incomplete data.”
The rise of vegan leather, which is typically made from polyurethane, a type of plastic that has a more favorable Higg rating, has brought unintended consequences, industry officials say. Even as leather is replaced by synthetics, Americans are still eating lots of beef — which means the hides from those slaughtered cattle have nowhere to go. In 2020, a record 5 million hides, or about 15 percent of all available, went to landfills, according to the U.S. Hide, Skin and Leather Association, a Washington-based trade group.
“They’re throwing the hides in the offal barrels out back,” said Ron Meek, a former meat processor who has been helping smaller plants weather the downturn in leather demand
This year, the sole representative of an environment group on the Sustainable Apparel Coalition board of directors resigned, citing the organization’s lack of progress on environmental and climate policies, and hasn’t been replaced.
“Their approach has been shrouded in a lot of secrecy. It’s not a transparent system,” said the former board member, Linda Greer, who now advises China’s Institute for Public and Environmental Affairs. “This industry, maybe more so than any other sector, is very big on talk, very big on the next exciting thing — almost as if it’s a fashion show, the season’s latest.”
In response to the complaints, the apparel coalition has de-emphasized direct comparisons across fabrics and said it is helping companies to make more sustainable choices within fabrics, and to come up with specific product-based scores that take into account factory practices and other variables. It also said it would welcome the submission of additional data from natural fiber industries.
Still, some experts question whether the Higg accurately reflects other factors, like emissions of planet-warming methane from the fossil fuels that plastics are derived from, the amount of non-biodegradable plastic that ends up in landfills or incinerators, or the microplastics shed by fabrics that have now been detected by scientists in the world’s oceans.
The apparel coalition said this was an issue it was seeking to incorporate once better data was available.
In all, experts say, relying on studies with different parameters and assumptions is tricky. A 2019 report by the Research Institutes of Sweden concluded that differences between producers could be far larger than differences between fiber types.
“The devil’s in the details,” said Sangwon Suh, an expert in life-cycle assessments at the Bren School of Environmental Science and Management at the University of California. “It’s difficult to make generalizations. Is the cotton rain-fed, or does it use irrigation or ground water? Are the petroleum-based synthetic materials being produced in countries with strict regulations?”
For consumers, all these variables make it tough to generalize about whether natural or synthetic materials are the more environmentally friendly choice, or to assess claims made by clothing brands. Experts say one of the few sure ways to minimize environmental impact is simply to buy fewer, longer-lasting pieces.
The Sustainable Apparel Coalition makes the Higg scores available to the public, but full access to the underlying data is limited to companies that pay a fee.
Companies can also pay a fee to submit new data to the coalition and obtain company-specific scores.
Last year, for example, the Higg Index said it had updated the rating for leather from JBS, the world’s largest meatpacker and one of the companies that the Times investigation last year found was sourcing cows linked to Amazon deforestation. The new JBS-specific assessment rates leather produced by JBS as among the world’s most sustainable.
JBS said it had submitted a new study to correct the apparel coalition’s “misleading analyses” on leather. “JBS also intends to contribute to elevate the quality of technical information available on leather, benefiting the entire sector,” the company said.
Gregory Norris, who teaches life-cycle assessment at the Harvard School of Public Health and who carried out a review of the Higg Index methodology in 2016, said many of the critics’ concerns were valid. But the index still represented “a very valuable body of work,” he said. “They could have waited, but to their credit, they dug in and they built something with today’s data,” he said.
Still, there were improvements that could be made, he said. For example, industry data could be periodically verified with independent spot checks. “There’s data scarcity problem that really needs to be solved,” he said.