THE 21m residents of Mexico City have far too much rubbish and not enough healthy food. Now they can swap one for the other. A new monthly market run by the city government takes paper, glass, plastic and aluminium in return for tokens that can be swapped for locally grown food and plants. Since it began in March the “Barter Market” in Chapultepec park has exchanged 140 tonnes of rubbish for 60 tonnes of produce.

The market is a small step towards tackling a big waste problem. In January piles of rubbish built up after a landfill closed. It had received up to 12,600 tonnes of trash a day, and was the size of 450 football pitches. The muck-up will not be the last unless households get better at recycling. “We want people to learn that rubbish is not rubbish,” says Paola de María y Campos, a city official who helped set up the market.

The project provides welcome jobs for the city’s farmers, many of whom work in the watery southern district of Xochimilco. Canals there are the last reminder of what Mexico City looked like before the Spanish drained the lake on which it sat. The city’s undeveloped south is prone to illegal slum-building. The government hopes to deter this by promoting farming on the land.

The market is proving popular. Queues start to form at 6am, and food nearly sells out by noon. “Now everyone in our family is separating their waste,” says Eugenia Trueba, showing off a bag of lettuce, sesame seeds and cactus leaves which she got for newspapers and plastic bottles. However, over half of visitors come by car, somewhat undermining the market’s green credentials.

The project does not break even. Each month the market sells 20 or so tonnes of rubbish to glassmakers, paper manufacturers and other firms for about 40,000 pesos ($3,100). The food, which the government buys from Xochimilco’s farmers at above-market prices, costs 90,000 pesos. Taxpayers pick up the difference.

The point, however, is to get people recycling, not to make money. Plans for new branches are under way, and the market may go fortnightly. The real test will be whether more households can be persuaded to recycle even without the carrot of free food in return.