Another 41 per cent of the bloc's textile waste goes to Asia, it added, mostly "to dedicated economic zones where they are sorted and processed".
"The used textiles are mostly downcycled into industrial rags or filling, or re-exported for recycling in other Asian countries or for reuse in Africa," the agency said.
A new EU rule adopted in November aims to ensure waste exports are recycled rather than dumped.
But the EEA admitted that there was "a lack of consistent data on the quantities and fate of used textiles and textile waste in Europe".
Indeed, NGOs told AFP much of Europe's waste clothes sent to Asia go to "Export Processing Zones", which Paul Roeland of the Clean Clothes Campaign said were "notorious for providing 'lawless' exclaves, where even the low labour standards of Pakistan and India are not observed".
Exporting "clothes to countries with low labour costs for sorting is also a horror in terms of carbon footprint", said Marc Minassian of Pellenc ST, which makes optical sorting machines used in recycling.
RECYCLING "MYTH"
The terrible truth is that "recycling is a myth for clothing", Greenpeace's consumer expert Panhuber insisted.
Others, however, are turning towards new vegetable fibres, with German brand Hugo Boss using Pinatex made from pineapple leaves for some of its sneakers.
But some experts warn that we could be falling into another trap. Thomas Ebele of the SloWeAre label questioned the way these non-woven fibres are held together "in the majority of cases" with thermoplastic polyester or PLA.
It means that while the clothing can be "sometimes broken down" it is not recyclable, he said.
"Biodegradable does not mean compostable," he warned, saying that some of these fibres have to be broken down industrially.
But beyond all that, "the biggest problem is the amount of clothes being made", said Celeste Grillet of Carbone 4.
For Panhuber and Greenpeace, the solution is simple: buy fewer clothes.
"We have to decrease consumption," she said - repair, "reuse and upcycle".