12. There have been many varied reasons to begin a recycling program in Curitiba. One of these was that old worn-out equipment was frequently being replaced with new technology. Another was that like every other city, old yet usable materials were being dumped around the city. This gave engineers and architects an opportunity to work together to use them creatively. Old wooden telephone poles are now reused in office buildings, bridges, and public squares. Retired buses have become mobile classrooms for adult education. A third but foremost was the recycling of house- hold garbage. A seven-year-old boy traded eight pounds of recyclable garbage for a packet of new notebooks. Mayor Rafael Greca said, "It's just a matter of figuring out how to reuse things and then teaching people how to do it."​