What does it mean to clean London?#nightsoil

About Night Soil, from BoardGameGeek:

Night Soil is a very mature game about sanitation in Tudor London. As the exemplar of cultural progress in Europe, Tudor London (1485-1603) is at the spear's edge of cultural and technological development. However, as modern plumbing is still generations away, the city is gradually filling up with human waste, making it a terribly fragrant place to live. In the game, players run competing night soil companies. By night, laborer cards will be used to carefully maneuver waste cubes through the narrow streets of London to turn a profit and to recruit workers. By day, these workers can be sent out into London to advertise, to garner favor with local businesses, or to improve their company's assets. However, crowds of workers do tend to add to the waste problem. At the end of the game, the player who has managed to make the most money wins! -description from the designer