reporter: arian rayegani, a mechanical engineer, drew the plans up himself. of it is this metal mold, in which 500 lids are melted into a skateboard deck using this pizza oven. arian: skateboards are an ideal product, in my view, because they're relatively durable, and i can recycle quite a lot of bottle tops in one go. the first time i saw a plastic skateboard on the street i thought, man. i can produce that, sustainably. reporter: every day, he loads another tray of bottle caps in to be melted at 180 degrees celsius. eight years ago, arian rayegani traveled to brazil and fell in love with this area. the mounds of garbage generated by the favela's 100,000 inhabitants inspired him to come up with a sustainability project. now, a small army helps him collect the caps -- the trash recyclers of rocinha. one of them is maria do rosario. from collecting plastic bottles, cans and glass, she earns the equivalent of 650 euros a month. she puts the lids to one side for arian rayegani. maria: for us, waste is valuable and brings in money. my son and i collect things for