Paying a metro ticket in exchange for plastic bottles
At the entrance of the Beijing metro, a machine allows to insert your bottle. The machine compresses it in twenty seconds and credits 1 mao on the ticket, 10 cents of Yuan. A metro ticket in Beijing costing 2 yuan (about 0.25 euros), you have to repeat the operation twenty times to travel for free. To understand the waste challenge in this city, you have to realize that some 20 million people in Beijing produce nearly 18,000 tons of household waste per day (compared with only 3,000 tons in Paris).
Recovering sick trees to make them boats that create social bonds