A bag left at a charity shop enters a supply chain most donors never see. Only a small share is sold in the shop it was left in, and the rest is graded and traded onward.
Shop floors have limited capacity
A charity shop has a fixed rail length and a fast turnover target. Items are selected on condition, season and how quickly they are likely to sell.
Anything not selected, and anything unsold after a few weeks, is bagged and sold by weight to a textile merchant. The price per kilogram is low but the volume is enormous.
That weight-based income is a meaningful part of what charity retail earns, which means the merchant trade is a feature of the model rather than a failure of it.
Grading is where value is separated
Merchants sort incoming bales into grades by hand. The highest grades are wearable garments in current styles, which command the best prices.
Below that sit garments destined for wiping cloths, and below that material for shredding into insulation, padding and industrial felt.
Sorting is labour-intensive and the margins are thin, which is why the trade concentrates in places where labour is cheaper than in the countries producing the donations.
Export markets do most of the reselling
Graded wearable clothing is baled and shipped to importers, largely in parts of Africa, South Asia and Eastern Europe, where it is sold through established second-hand markets.
These markets support substantial local trade, employing sorters, traders, tailors and repairers, and they supply clothing at prices new garments cannot match.
They also face a real problem with unsellable volume, since a bale bought unseen contains a share of items that cannot be sold anywhere and become a local waste cost.
Fast fashion changed the input
The trade was built when donated clothing was mostly durable and made from natural fibres, and when a used garment had years of life left in it.
Lightweight synthetic garments with short lifespans arrive already worn out, and they are difficult to recycle because blended fibres cannot be easily separated.
The consequence is a falling average value per bale, which squeezes graders and pushes more material toward the lowest-value uses.
Donation is not the same as recycling
Donating shifts the decision about a garment onto someone else rather than resolving it. The garment still has to find a wearer or a use somewhere.
Items in genuinely good condition and current in style have the best chance of being resold, and they are the ones the whole chain depends on.
The most useful thing a donor controls is what enters the system, since a worn synthetic top will consume sorting labour and end up as waste regardless of intention.