There's not a lot of green in the urban jungle of Sao Paulo, but thanks to Fernanda Danelon, restaurants in the Brazilian megacity are turning their waste back into food at innovative gardens tucked amid the skyscrapers.

Danelon, a 43-year-old journalist by training, quit her day job two years ago to launch the Guandu Institute, which recycles restaurants' food waste and helps them set up gardens to put all that compost to good use.

Cities in Brazil, the economic giant of Latin America, throw out more than 75 million tons of trash a year, according to the Brazilian Association of Public Sanitation Companies (ABRELPE).