A just painted scrap cart or Carroca in Soa Paulo, Brazil. Credit: conexao cultural 

Sanitation workers have long been among the least respected members of society.

In his 1968 "I've Been to the Mountaintop" speech to Memphis Tennessee's striking sanitation workers, Martin Luther King said "the issue is injustice. The issue is the refusal of Memphis to be fair and honest in its dealings with its public servants, who happen to be sanitation workers. Now, we've got to keep attention on that."

But without sanitation workers, where would a city be?

That's the situation for São Paulo's scrap hunters or catadores, who comprise the informal workforce that makes the city's 98 percent aluminum can recycling rate possible. The recycling rate is achieved entirely through an infomral economy, without the assistance of government.

Often marginalized by society, these workers, 20,000 strong, face harassment by municipal officials and citizens as they scavenge for recyclables. Yet their work provides an invaluable public service, while allowing them to support their families.

Enter PIMP MY CARROÇA. Created by Brazilian artists Mundano and Joao Paulo Possos, the crowdfunded project combined art with social action to raise awareness about the value of these workers while decorating their carts, known as carroca's, in buoyant colors and graffiti.

"I came here to become visible," says one catodore in the video below. "Today, I took the day off to come here, but if I hadn't, I certainly would be working to support my family with dignity."