In short:
Only about 10 per cent of donations to op shops actually make it to the store floor.
The rest is taken by recycling firms, but one of Australia's largest has stopped taking excess stock.
What's next?
Experts say people need to make more considered decisions when buying new clothes.
Op-shop operators are worried they will need to spend more money sending donated clothes to landfill as fabric recycling firms abroad hit capacity.
In Australia, only about 10 per cent of items donated to op shops make it to store floors, with those rejected in too poor a condition to sell.
It means stores need to find a way to dispose of unsellable clothing, with many sending it to recycling firms where the fabric is given a second life.
The Anglican Belltower Op Shop in Mount Gambier in regional South Australia uses a firm called Statewide Cleaning Cloths, which takes fabric and turns it into cleaning cloths sent across the world.
But volunteer Trudy-Anne Doyle recently received a letter saying the company would no longer be taking stock from Australian stores.
"If you can't send it to Statewide it's not good enough to sell and we're not selling everything we put out to sale anyway. Then it's going to go to landfill," she said.
"Our immediate response has been to unpack what we were going to send to Statewide and put it on a free rack and see if the public might take it.
"But our prices are [already] pretty low and the public may not want it."
Ms Doyle said she wanted to avoid sending clothes to landfill, but op shops receive so many donations they may have no choice.
Warehouses at capacity
Statewide Cleaning Cloths takes clothes and sells them to Malaysia where the higher-quality items are sent to other countries and the rest converted into items like cleaning rags.
It operates across Australia and said it exported about 20 million kilograms of clothes from Australia to Malaysia in the past two years.
The CEO of Asian Operations, Dale Warren, the operator of Statewide Cleaning Cloths, said the amount of second-hand textiles in the market was putting pressure on the recycling system.
"Some countries like France subsidise their collection system so their material is a lot cheaper than from Australia," he said.
"On top of that, the shipping costs for the Asian corridor have increased dramatically, and those increases have an impact on the price.
"But people's habits in Australia haven't changed, and people are still discarding and donating clothing which is building up a lot more of a reserve."
Mr Warren said global markets for these materials were changing and the company's warehouses are currently at capacity.
He said with the difficulties finding customers to take the fabric and the industry's current pricing meant the company would operate at a loss.
Fun with what you have
University of Technology Sydney Associate Professor Timo Rissanen has studied global clothing systems and is a self-described "op-shopper".
He said the global second-hand clothing system was complex and getting larger as the globe produces more clothes.
"We are producing more clothes than ever before in history," he said.
"The growth in total production of new clothing for the past 25 years or so has been much faster than the growth of humans.
"This ranges from 80 billion items to 150 billion items, and the estimates speak to how difficult it is to paint a global picture."
Dr Rissanen said the joy of fashion should come from experimenting with what you have, not from buying new items.
"We have some individual questions to ask around what is enough and what does sufficiency look like?" he said.
"It's about looking at the things you already have and having some fun with it too.
"Fashion should be fun ultimately. I still believe fashion should be life-enhancing and should bring joy to all of us."
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