Carlos Quintero picked up a huge bag full of plastic bottles and moved a few feet forward before setting it down again in the long snaking queue to get into Mexico City's Mercado de Trueque, or barter market. In return for donating the bottles for recycling, Carlos would receive well-needed tomatoes, onions and a cabbage.

"It is a really good way of getting something out of things we normally throw away and helping the environment," he said. "And it helps the family economy, too."

The monthly market started in March last year, aimed at raising awareness about recycling through modest vegetable incentives. But the project is now straining under the weight of its own success.

"The objective is that people learn to separate, store and value the waste they produce," said Liliana Balcazar of the city's environment ministry, which runs the market, usually in a central park, although it moves to different locations around the capital every other month. She said the market received about 12 tonnes of rubbish each time. "It was always popular," she said, "but now it is overflowing."

Recyclers hand their rubbish over to government employees, who weigh the material and give vouchers to exchange for vegetables grown by farmers on the outskirts of the city.

Recent participants – who ranged from an architect with a trolley full of wine bottles to a poor woman with a neatly tied-up bundle of cardboard – recognised that the market would never solve the problem of how to manage the 12,000 tonnes of rubbish the city produces every day.

Since the closure of an enormous landfill early last year, shortly before the market opened, rubbish has been trucked out to smaller tips in surrounding states at considerable cost. There has been little sign of the environmentally friendly hi-tech waste management facilities that have been promised for many years.

Even so, the market's most dedicated fans return month after month, oftenwith friends or family in tow. "It is really worth the effort," said Erika Rodriguez, a regular, accompanied by her mother. "Once you start, it is difficult to stop."

"It's great for us," said smallholder Axel Castañeda as he cleared away piles of beetroot stalks, his entire stock gone."The price is good, and the volume is great."

But some of those handing over their recycling are inevitably disappointed, because the range and availability of vegetables quickly dwindles by late morning. Late arrivals are more likely to end up with a bunch of vouchers and almost nothing left to swap them for.

A harried official, surrounded by one such group, unhappy about going home with only radishes and tomatoes, pleaded for understanding. The market, he said, is "an educational project not a substitute for normal rubbish collection".