Hand sorting, while highly labour intensive, is associated with exceptional coffee quality. In this video from San Francisco–based Sweet Marias, green buyer Thompson Owen has travelled to a washing station run by a cooperative in Burundi. The film explains that it is the policy of the washing station to request each farmer to soak the coffee cherry in water-filled tanks and then to lay the cherry out on tables and hand-sort the green cherry from the red ones.
Due to advances in the technology of optical sorting machines (aka colorimetric sorters), machines have become cheaper and more accurate than they were when they were first introduced into the coffee world in the 1980s. They are extremely fast; a single chute in a machine can sort about 1 tonne of coffee per hour.