Poop is big business in Dakar, Senegal. That's because a lot of the homes have septic tanks, which need to be cleaned out regularly. The best way to clean your tank is by hiring a proper truck, which arrives with a vacuum.
The problem is that for years, the guys who drove the poop trucks operated as a cartel, and they squashed competition and kept prices high. So a lot of people turned to a cheaper alternative: Men who clear out septic tanks by hand, with shovels and buckets, and basically bury the poop in the street. It's terrible work and bad for the environment.