Online retail giant Amazon generated almost 500 million pounds of plastic packaging last year, more than 22 million pounds of which ended up in rivers and oceans, a new report has claimed, potentially threatening efforts by CEO Jeff Bezos to burnish his firm’s sustainability credentials.

According to research from ocean conservation charity Oceana, plastic air pillows and bubble wrap accounted for most of the waste from Amazon deliveries, the use of which has risen rapidly in recent years. The report, which surmised that Amazon sent some 7 billion deliveries last year alone, calculated that the combined length of the air pillows used by Amazon in one year would circle the Earth 500 times. Furthermore, the charity said, the size of the company’s plastic footprint is set to grow as its global operation expands.

The report also found that most Amazon customers want the company to change its ways, with 86% of those surveyed saying they were concerned about plastic pollution. Noting that the company has already made moves to eliminate single-use plastic waste in its India operation, Oceana included in the report a series of steps Amazon could take to shrink its plastic impact.

Announcing the release of the report, Oceana’s senior vice president Matt Littlejohn emphasized the scale of the problem. “The amount of plastic waste generated by the company is staggering and growing at a frightening rate,” Littlejohn said. “Our study found that the plastic packaging and waste generated by Amazon’s packages is mostly destined not for recycling, but for the landfill, the incinerator or the environment including, unfortunately, our waterways and sea, where plastic can harm marine life.”

“It’s time for Amazon to listen to its customers, who, according to recent surveys want plastic-free alternatives, and make real commitments to reduce its plastic footprint,” he said.

Plastic waste causes immense harm to marine environments, poisoning and choking marine life and getting into the food cycle. At least 8.8 million tons of plastic enters the oceans each year. That rate is likely to grow as plastic production increases, and as oil companies invest more in plastics.

The report raises awkward questions for Amazon’s founder Jeff Bezos, the world’s richest man, who last month named the first recipients of his $10 billion “Earth Fund,” intended to support climate action. For its part, the company claims that since 2015, it has reduced the weight of its outbound packaging by more than 33% and cut out 900,000 tons of packaging material. The company also says it has taken steps to make its packaging products easier to recycle, and that it will recycle as much as 7,000 tons of plastic film at 55 of its fulfillment centres annually.

But Oceana noted that despite these claims, Amazon provides little detail in its sustainability reports about its plastic packaging. Most of the plastics that Amazon uses in its packaging are either not recyclable or have little value in the recycling market, according to a Greenpeace report published this year. And even when plastics are recyclable, they are simply adding to another problem: as reported previously by Forbes.com, a lack of recycling facilities and a low rate of return means only around 9% of plastic waste worldwide is recycled; the rest either ends up in landfill, is burned, or ends up in the natural environment.

In a survey of more than 5,000 Amazon customers in the U.K. and North America, Oceana found that 92% “were upset that plastic recycling does not work” and 87% wanted Amazon to offer plastic-free packaging choices at checkout. At the time of writing, more than 665,000 Amazon customers had signed a change.org petition asking the company to offer plastic-free packaging options.

Among the other recommendations Oceana had for Amazon, the charity suggested “aggressively” scaling up existing in-company programs to reduce plastic packaging, as well as broadening the use of reusable containers. The charity also called on Amazon to improve sustainability transparency around reporting on plastic usage, and to take into account the environmental impact of plastics in its high-level business decisions.