The energy giant Shell has quietly backed away from a pledge to rapidly increase its use of “advanced recycling”, a practice oil and petrochemical producers have promoted as a solution to the plastics pollution crisis.

“Advanced” or “chemical” recycling involves breaking down plastic polymers into tiny molecules that can be made into synthetic fuels or new plastics. The most common form, pyrolysis, does so using heat.

Shell has invested in pyrolysis since 2019, touting it as a way to slash waste. That year, the company used oil made via pyrolysis in one of its Louisiana chemical plants for the first time. And it began publicizing a new goal for the technology: “Our ambition is to use 1m tonnes of plastic waste a year in our global chemicals plants by 2025.”

But recently, the company rolled back that promise with little fanfare: “[I]n 2023 we concluded that the scale of our ambition to turn 1m tonnes of plastic waste a year into pyrolysis oil by 2025 is unfeasible,” it said in its 2023 sustainability report, published in March.

Reached for comment, a Shell spokesperson, Curtis Smith, said: “Our ambition, regardless of regulation, is to increase circularity and move away from a linear economy to one where products and materials are reused, repurposed and recycled.”

The company has not called attention to this retraction, but it is a “significant” change, said Davis Allen, investigative researcher at the Center for Climate Integrity, which shared the finding with the Guardian.

“It’s an acknowledgment that advanced recycling is not developing in the way that companies have promised it will, and are counting on it to,” he said. “That’s pretty meaningful.”

Researchers and environmental advocates have long raised concerns about advanced recycling, warning it can create even more toxic and planet-heating pollution than virgin plastic production and is even more energy intensive than traditional plastic recycling. Studies show the facilities are most likely to harm communities that are already vulnerable to contamination and climate threats.

But that is not why Shell struck its pledge. In the report, the company said the walk-back was necessary due to changes in the market.

“While Shell sees customer demand for circular chemicals, the pace of growth globally is less than expected due to lack of available feedstock, slow technology development and regulatory uncertainty,” the document says.

Complaints of insufficient feedstock may seem a surprising when hundreds of millions of tons of plastic are produced each year. But despite what is suggested in marketing materials, post-consumer items such as food packaging and empty soap bottles cannot easily be recycled via pyrolysis. The process works best with clean, homogeneous inputs, but sorting and cleaning plastic is expensive. As a result, most chemical recycling facilities working at scale rely mostly on processed industrial scrap – or “plastic left on the cutting room floor during production”, said Allen.

Slow technology development has indeed been a factor in the advanced recycling market said Allen, but one that Shell “maybe should have seen coming”.

The industry has claimed pyrolysis will be a groundbreaking solution to plastic waste for many years; Allen recently found a lobby group document making such claims in the 1970s. But experts have also told the the sector for decades that there are practical issues with advanced recycling, the Center for Climate Integrity has found.

Today, there is mounting evidence that advanced recycling “often just does not work”, said Judith Enck, president of advocacy group Beyond Plastics and a former EPA regional administrator. Many of the United States’ 11 advanced recycling facilities operate only partially, and two have been shut down altogether.

Shell’s third reason for walking back their pledge – regulatory uncertainty – probably refers to a rapidly changing advanced recycling policy landscape. Many states have recently passed pro-advanced recycling legislation, due largely to lobbying by the powerful industry group the American Chemistry Council, said Enck.

But some regulators are moving in the other direction. The Environmental Protection Agency last year withdrew a plan to ease some regulations on pyrolysis, while New Jersey recently decided chemically recycled material should not be considered recycled plastic.

Other plastic producers, such as Exxon and Dow, have also pledged to rapidly expand their advanced recycling capacities. The technology can bring forth a “circular” plastics economy that reduces the need to use virgin fossil fuels, the industry often claims.

“The commitments have tied into a broader strategy to push advanced recycling as an answer to all of the public’s concerns about plastic waste,” said Allen. “It lets them say, ‘it won’t matter that we’re producing [several times] the amount of plastic that we’re producing now in several decades, because it will all be circular.”

Though it has reversed this advanced recycling pledge, Shell does not appear to be backing away from its plans to expand plastic production. It recently opened a chemical complex as large as 300 football fields near Pittsburgh, with the capacity to produce 1.6m tons of plastic a year.

It is also still a member of the American Chemistry Council and its subgroup America’s Plastic Makers, which has recently been running an ad promoting advanced recycling which asks audiences to “imagine a future where plastic is not wasted, but instead remade over and over”.

Still, the retraction is a tacit acknowledgment of the longstanding issues with the technology, said Enck.

“I have never said this before, but Shell has made a wise decision here,” she said. “Chemical recycling is a polluting and an unreliable way to address the growing problem of plastics.”